BIOL 273
Lecture 1 Course Outline
Lecture 2 Multiple Choice Review Question 1. Which of the following allow the movement of g ases (O2 and CO2) across the epithelium? a. Transport b. Exchange c. Ciliated C iliated d. Protective e. Secretory
Lecture 3 2. Receptor molecules for chemical signalling can be located a. in the membrane b. in the cytosol c. in the nucleus d. b and c e. all of the above If the receptor molecules are nuclear than they are inside, but for cytosolic c ytosolic and membrane they might either be in in the cytosol or on o n the membrane for it bringing it in, so it’s dependant on the signalling molecule and it’s function Nervous System Function - Key control structure (along with endocrine) - Receives information using sensory neurons (receptors) to receive from external environment we have mechanisms inside our body bod y such as specialized cells, like joints that o sense how we are moving there is a sensory pathway regardless of whether the information is being obtained o externally or internally a receptor is a cell that is capable of receiving information (used to describe an o actual cell rather than a protein inside a cell) - Integrates information (organizes info. and brings together with already previously stored information) - Transduces information (sends appropriate signals to muscles or glands) Two components of the nervous system: s ystem: central (CNS) and peripheral (PNS) - CNS: brain and spinal cord - PNS: sensory neurons/receptors, efferent neurons CNS – CNS – Brain Brain and spinal cord - Clusters of cell bodies -> nuclei - Bundles of axons forming a pathway -> tracts (Always associate the terms ‘nuclei’ and ‘tracts’ as related to the CNS) PNS – PNS – Everything Everything else - Consists of nerves -> bundles of axons of sensory o r motor neurons existing outside of the CNS
- Peripheral nerves - Clusters of cell bodies -> ganglia - Receptors Stimulus -> sensor/receptor -> afferent pathway -> integrating center -> efferent pathway -> target or effector -> response - Stimulus attacks the sensor/receptor which then carry on in a sensor/afferent path and arrive at the CNS which receives this information and becomes the integrating center and processes the information to a motor/efferent path which attacks a target/effector target/effector and 9yhy6creates a response to the original stimulus Components of the nervous system 1. Receptors: are specialized cells that convert stimuli (eg. touch) into electrical signals and transmit information to sensory/afferent neurons (Eg. when you hear sounds, the hair cell in your middle ear are rapidly moving when processing this sound deeper into your ear so it is this movement of the hair that creates creates a signal: i.e. the stimuli is changed into a signal) 2. Afferent (sensory) neurons: transmit sensory information TO the CNS because these are cell bodies that are located outside the CNS, and then long c ytoplasmic extensions transmit info. to cells (interneurons) within the CNS 3. MISSED THIS BC ON PHONE (URGH) 4. Efferent (motor) neurons: receive info. from interneurons, there are cell bodies located within CNS and the cytoplasmic extensions transmit info. to effectors – effectors – muscles muscles and glands (so it’s pretty much that you receive a signal that signal is interpreted within the CNS and then sent out to a different area) Concept Maps (very helpful in this course) cou rse) Nervous System CNS PNS Brain and spinal cord Sensory and motor Somatic and autonomic Sympathetic and parasympathetic The only target cell is a skeletal muscle when we are talking about the somatic motor neuron For autonomic, the control is over smooth muscle and influences cardiac muscles, endo/exo crine glands Cells of the nervous system a. Neurons
b. Glial cells (neuroglia)
Typical neuron (nerve cell) - Main role: transmit signals over long distances (this distance varies) - 4 main parts: i. soma (cell body): center of chemical processes (keeps cell functioning and alive) Soma does mean body so you can interchangeably use the words cell soma and cell body ii. dendrites (“dendron”: tree): transmit electrical signals TOWARDS soma
- Peripheral nerves - Clusters of cell bodies -> ganglia - Receptors Stimulus -> sensor/receptor -> afferent pathway -> integrating center -> efferent pathway -> target or effector -> response - Stimulus attacks the sensor/receptor which then carry on in a sensor/afferent path and arrive at the CNS which receives this information and becomes the integrating center and processes the information to a motor/efferent path which attacks a target/effector target/effector and 9yhy6creates a response to the original stimulus Components of the nervous system 1. Receptors: are specialized cells that convert stimuli (eg. touch) into electrical signals and transmit information to sensory/afferent neurons (Eg. when you hear sounds, the hair cell in your middle ear are rapidly moving when processing this sound deeper into your ear so it is this movement of the hair that creates creates a signal: i.e. the stimuli is changed into a signal) 2. Afferent (sensory) neurons: transmit sensory information TO the CNS because these are cell bodies that are located outside the CNS, and then long c ytoplasmic extensions transmit info. to cells (interneurons) within the CNS 3. MISSED THIS BC ON PHONE (URGH) 4. Efferent (motor) neurons: receive info. from interneurons, there are cell bodies located within CNS and the cytoplasmic extensions transmit info. to effectors – effectors – muscles muscles and glands (so it’s pretty much that you receive a signal that signal is interpreted within the CNS and then sent out to a different area) Concept Maps (very helpful in this course) cou rse) Nervous System CNS PNS Brain and spinal cord Sensory and motor Somatic and autonomic Sympathetic and parasympathetic The only target cell is a skeletal muscle when we are talking about the somatic motor neuron For autonomic, the control is over smooth muscle and influences cardiac muscles, endo/exo crine glands Cells of the nervous system a. Neurons
b. Glial cells (neuroglia)
Typical neuron (nerve cell) - Main role: transmit signals over long distances (this distance varies) - 4 main parts: i. soma (cell body): center of chemical processes (keeps cell functioning and alive) Soma does mean body so you can interchangeably use the words cell soma and cell body ii. dendrites (“dendron”: tree): transmit electrical signals TOWARDS soma
iii. iv.
axon: transmit electrical signals AWAY FROM the soma (when the cell becomes very axon terminals: participate as part of the synaptic (presynaptic) (NOTE INCOMPLETE)
Diverse neuron forms and functions Pseudounipolar (pseudo uni polar : false one pole) somatic sensory neuron o o axon & dendrites fuse during development (one long process) bipolar (bi polar : two poles) smell/vision sensory neurons o o single axon and dendrites (?) DIDN’T FINISIH NOTE anaxonic (don’t worry about this too much the function is not very well understood) interneuron o no apparent axon o multipolar – multipolar – CNS CNS (multi polar : many poles) highly branched o no long extensions for the axon o multipolar – multipolar – efferent efferent (multi polar : many poles) 5 – 7 7 dendrites single long axon
Glial cells the y are associated with neurons (there are a lot more - Outnumber neurons by 50:1 -> they glial cells that will help the neurons carry out the job of carrying electrical signals over long distances) (communicate with each other and with - Don’t carry electrical signals over long distances (communicate nearby neurons using electrical/chemical signals) (NOTE UNFINISHED) Two types: Schwann cells and satellite cells 1. Schwann cells -> wrap around axon forms myelin (myelin is just multiple layers of membrane wrapped around itself) o gap junctions found between layers o o electrical insulator 2. Satellite cells non-myelinating Schwann cell o support nerve cell bodies (soma) o Glial cells of CNS - Oligodendria (oligodendrocytes) CNS version of Schwann ecell o wraps around axons -> forms myelin to insulate ax ons o star- shaped cells (“astron”: star) (DIDN’T FINISH TH IS) - astroglia (astocytes) -> small star-shaped - microglia o very small specialized immune cell (macrophage-like) o
function is to remove damaged cells & foreign invaders ependymal cells o epithelial cells that produce cerebral spinal fluid (CSF) create selectively permeable barrier between compartments of the brain) o o
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Lecture 4 3. Which of the following is/are sensory neurons? a. anaxonic b. pseudounipolar c. bipolar d. b and c e. all of the above How do neurons transmit electrical impulses? - via energy stored as an electro-chemical gradient (utilizing this energy is very important) - Need to understand the physics of electrical and osmosis as they apply to cells Cell membranes are really good insulators that ultimately separate the ICF a nd ECF (intra and extra – extra – cellular cellular fluid) - When the cell membrane separates those charges it creates an electrical gradient because of the difference in charges that outside vs inside - Coulombs law: you see a change in the strength as it decreases as it is further awa y from the charges (the closer it is, the stronger it is) - there are net negative charges on the inside and net positive on the outside (this is the difference that creates a gradient, when the g radient involves these electro-chemical charges it is an electrical gradient) - the insulator (membrane prevents the charges from freely moving across the cell membrane) - you must create an ion channel to process movement of these charges because the cell membrane is such a good insulator Osmotic principles deal with a chemical gradient - occurs when you have a difference in concentration across the membrane - a concentration gradient is important because molecules move down the concentration gradient which means they move from an area of high concentration to an area of low concentration (this is important because this naturally occuring behavior of molecules creates a free movement across the membrane as long as the cell membrane is premeable) but from what we know, the cell membrane is semi-premeable The semi-premiability means that some molecules are too big or too repulsive to pass through the cell membrane so even though there is a concentration gradient set a cross the membrane, which is pushing the molecules from a high conc. area to a low conc. area, these molecules must be processed through protein channels (which are big openings in the membrane due to protein interference which allows the specific molecules to pass across the membrane using that protein channel) influx and eflux (eflux is when you move outside, influx is when a molecule moves into the cell) - for most molecules the cell membrane is impremeable too, so it is only through the ion channels that it is able to move across that c ell membrane
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no net movement means that there is no net influx or no net efflux of that ion across the membrane (it doesn’t mean that there is no movement at all)
For any given ion you can easily calculate the electrical potential of the cell needed to generate an equilibrium state, if you know the concentration gradient What does the nernst equation do? predict the equilibrium potential for an ion (understand what the equation is used for, and be able to recognize the equation) Equilibrium potential allows you to determine what the electrical potential will be when there is no net movement across the membrane z = electrical charge of the ion (eg. sodium ion has a +1 charge) If you compare the actual membrane potential of the cell to the equilibrium potential for that ion, you can predict whether an ion is going to move into or out of the cell Membrane potential: at rest there is always a difference ALL CELLS HAVE MEMBRANE POTENTIAL AND ALL CELLS ARE NET ELECTRO NEGATIVE INSIDE THE CELL (but only the cells that are known as excitable tissues that will utilize that membrane potential, which is what the major difference between signalling for the nervous system cells and regular cells are) The membrane potential results from the different concentrations of ions inside the cell vs outside the cell The excitable cells, when they are not at rest they are excited, we call this membrane potential because having that electro-chemical gradient is a source of energy (a dam is no different than a cell membrane, it is a great insulator which do esnt allow molecules to freely pass, when there is a concentration gradient there is potential energ y) Think of a water behind the dam, there is water just waiting to flow out and burst so that dam is the membrane and that water is at rest which has potential ENERGY At rest a neuronal cell at sit at a -70 (which comes from the concentration gradient of different ions across the membrane and their membrane premeability) On the graph, for hyperpolarization, your starting point always has to be at rest (so the resting potential), even when you are at a hyperpolarized state (what is it called when you return to rest? repolarization) Repolarization is from any starting point when you are returning to the original “rest” position The light green is what represents the opening o f the channel where as the dark green represents the two poles that keep the membrane separated CONCEPT CHECK: Match each ions movement with the associated change in membrane potential
1. 2. 3. 4.
Na+ entry (D) Cl- entry (H) K+ exit (H) Ca2+ entry (D)
Depolarizing Hyperpolarizing
Depolarizing is you going towards move positive, hyper is you going more negative So when you gain sodium, you go more positive which is depolarizing, when you lose potassium or gain chloride (you are hyperpolarizing your cell) Would a cell with a resting membrane potential o f -70 mV depolarize or hyperpolarize in the following cases: 1) Cell becomes more permeable to Ca2+ (Eion = +122 mV) -> depolarize 2) Cell becomes less permeable to K+ (Eion = -90 mV) -> depolarizes (the positive charge of the K+ stays within the cell, so it makes the overall charge less negative)
Lecture 5 4. Q: T/F: Na, K, Ca ion concentrations are higher outside the neuron False: K is greater inside Role of sodium ions: Na+ contribute minimally to resting membrane potential -> due to low permeability - but very important in generating changes in membrane potential that causes electrical signals Graded potential Depolarization (moving towards positive), hyperpolarizing (more negative; could be getting more negative towards the resting membrane potential) - occur in dendrites/cell body, open/close channels It can be either strong depolarizing or strong h yperpolarizing, one or the other (not both) - always strongest where it initiates but always loses strength Membrane – incomplete impermeable to the movement of ions (leaky channels: graded potentials lose strength) What causes a graded potential to start? neurotransmitter (signalling molecule that binds to a receptor and opening ion channels) - the ion channels are triggered by neurotransmitters (the binding to the receptor causes the ion channel to open) - strength of the graded potential ~ strength of the original stimulus and how many K/Na/ions have moved through the channel causing a hyperpolarized graded potential or depolarized graded potential
two neurons communicating with each other (synapse) and send chemical signal which causes a Na ion channel to open (depolarizing effect because the Na(+) enters the cell, so where would the graded potential be the strongest? CLOSEST TO THE ORIGIN OF THE ST IMULUS ...if graded potentials travel only short distances how can a neuron that reaches the full length of the body travel? - essentially impossible for a graded potential to travel that distances in a resonable amount of time without degrading (regardless of how strong the original signal, there’s too much leakage/resistance for the graded potential to travel the full length o f the body) - a different kind of signal is used: action potential (rapid long d istance electrical signal/impulse that travels down the length of the bo dy) Action vs graded: two differentiations: 1. action potentials identical to each other: no “volume control” : they are “on/off” - no slightly different graded strength (it is either happening completely or no t at all) 2. action potentials dont diminish in strength as they travel long distances th rough neuron (signal is strong all the way) what triggers action potential? membrane potential (when resting membrane p otential deviates around -55mV, it is known as the threshold potential for the action potential to become triggered) - the right spot to look whether the threshold potential has been reached is at the trigger zone (if the graded potential has a depolarizing effect, at -55 does it initiate an action potential? only if the -55 is at the trigger zone (because thats where it starts) - even if it is strong enough to go past/reach the threshold, if it has decreases in strength b y the time it reaches the trigger zone then no action potential is fired Graded potentials can initiate action potentials: multiple axon terminals all possibly sending signals (could be either depolarizations/hyperpolarizations) but it can happen all the wa y around the cell, so different areas where the signals come from but the y all come together and summate at the trigger zone (and if they collectively have a potential minimum -55mV, then action potential is triggered) Graded potentials can sum over: space (spatial summation) (Regardless of how they summate the main question is whether the threshold potential is met for the action potential to be intiated? is the stimulus strong enough to reach threshold at a distance where the trigger zone lies?) spatial summation: multiple synpases causing graded potential inside the cell and as those graded potentials come together summate at the trigger zone (minimum -55: three depolarizing graded potentials will reach threshold (or go above) over time (temporal summation: where graded potentials occur in one single location, and follow that signal location as time goes on, we can see multiple graded potentials and bring those graded potentials together at the trigger zone to reach the threshold) two graded potenaisl will not cause an action potential if they are far apart in time
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if two subthreshold potentials arrive at the trigger zone within a short period of time (they may sum and create an action potential)
spatial/temporal summations can happen at the same time (temporal is a very strong amount of time) EPSP (exicatory post synaptic potential: signal that happens in the neuron (if depolarizing: it excites the cell: it might not make it there but they increase the chance of exciting the axon to “fire” an action potential (they might not meet threshold but it helps to atleast try to get close) IPSP (inhibitory post synaptic potentials: overall membrane potential is decreasing so its getting further and further away from the -55 threshold w hich causes the action potential to be inhibed) depolarization triggers Na+ (activation gate closed) rapidly opens (activation gate open) and the positive feedback loop continues until something outside isnt happening (then inactivation gate gets corked in to stop) how does the membrane potential return to resting level? K+ ions leave the cell (falling/repolarizing phase of AP) returning resting membrane potential: K channels are slower to open than Na+ channel -> depolarization to threshold triggers opening k channel (gating potential: i.e. full opening is around +30, compared to full opening at -55 for Na channel) open: the activation gate is open, allowing passage closed: activation gate blocks movement the trigger for both the channels is -55 but the k channels just open so slowly that it is around +30 mark that the K channel is fully open which is when we see the movement of potassium inside/outside the cell NOTE*** very few ions move across the membrane during a single action potential: the concentration gradient DOES not change much after one action potential (misconception: doesnt take very many to go across the membrane to change the membrane potential)
Lecture 6 Q. The trigger zone in a neuron: a. is at the axon terminal of efferent neurons b. is a region of the axon called the final segment in efferent neurons c. is the integrating centre of the neuron d. ‘a’ and ‘b’ e. ‘a’, ‘b’, ‘c’ Why can’t AP (action potential) be generated during the absolute refractory period? Na channel is in the inactive phase (you can generate one when it is in the closed conformation) and that closed conformation only happens in the relative refractory period
-70 to -55 is the threshold stimulus, but during the relative refractory period the resting potential might be sitting at -73, -74, so it is hyperpolarized, so to go from -74 to -55 takes more stimulus (so this is called the suprathreshold zone) The Domino effect: electrodes have been placed along the axon (once the dominoes have fallen over that is the absolute refractory period, because you can’t have another domino fall until you reset it: memberance potentials are recorded simultaneously If you can’t propagate the action potential with a decent amount of speed, then it wouldn’t be fast enough which is a problem Membrane resistance: determined by diameter and leakiness of neuron: there altering the diameter of the leakiness chang es the resistance Some invertebrates (squid and earthworm) have fairly simple nervous system but they are able to control the resistance of the membrane - they have GIANT AXONS - which means that there is a great diameter (the greater the diameter, the greater the reduction in the resistance) When you reduce axon diameter, you increase the resistance Vertebrates (because we don’t have giant ax ons that can combat membrane resistance) we have another way which is insulated nerve (remember nerve is just a bundle of axons) insulated nerves: - reduces resistance or degree of leakiness - insulated axons speeds conduction Mammalian neurons are surrounded by a m yelin sheath: - myelin sheath acts as an insulator - it is made up of many layers of plasma membrane - the membranes are part of specialized glial cells that wrap around axons of neurons in PNS (schwann cells) A depolarizing effect happens in the first node of ranvier and the schwann cells are myelinated (which means that they are insulated: so they don’t have open voltage gated channels) so it seems as though the effect is just travelling from the first node to the second node (although really the energy is conserved and transferred through the insulated myelination of the schwann cells) If you have a normally myelinated axon become non-myelinated (degeneration of a normally myelinated axon)
Types of synapses: 1. electrical synapse: - signals pass through gap junctions - rapid conduction -> information can flow in both directions 2. chemical synapse: FIGURE 8.19 - when it is synapse between a neuron and an effector cell: neurotransmitter junction Presynaptic cell: many vesicles -> contain neurotransmitter (neurotransmitteres diffuse through the synaptic cell) bind to receptors on postsynaptic cell membrane (results in changes in the postsynaptic cell) KISS AND RUN (is the second way that the neurotransmitter can be resulted) - the first is when the vesicles diffuses with the vesicle membrane and the presynaptic membrane Our cells are very good at keeping calcium levels very high in the extracellular fluid and up in storage (but the influx of ions which causes the trigger of the neurotransmitter from the synaptic vesicles) - the synaptic vesicle “kisses” the docking protein (which changes conformations) and then the vesicle runs away - the vesicle interacts with the docking protein (the kiss) and when the When the neurotransmitter is released it binds to the ion c hannel directly and influences an influx/efflux of the ion (depending on what channel it binds to) You have a presynaptic axon terminal releasing a neurotransmitter which diffuses across to the postsynaptic membrane (the direct response is where the neurotransmitter binds to the ion channel directly, and changes the shape (i.e. open or closes it)
Lecture 7
Q: When voltage gated Ca2+ channels in the axon terminal open: a. the signal to open was axonal depolarization b. Ca2+ enters the axon terminal c. Ca2+ leaves the axon terminal d. ‘a’ and ‘b’ e. ‘a’ and ‘c’ Cells are very good at keeping Ca outside the cell membrane, so when the channel opens, calcium comes in and causes release of the neurotransmitter at the synapse Neurotransmitter: 6 major types 3. amino acids: most abundant neurotransmitter in CNS 4. neuropeptides: peptide = small little protein, transcription and translation pathways so the synthesis for neuropeptides are made in the rough ER where the rest of the cell’s proteins
are made, and then the vesicle travels down to the axon terminal and waiting for it’s release at the synapse (to pass the signal along) 5. nucleotides can act as signalling molecules but there are receptors found in the CNS that will respond to the release of ATP along the synaptic cleft - the adenosine (nucleoside) can also act as a neurotransmitter 6. gases: kind of FYI Neurotransmitter degradation: Neurotransmitter inactivaton: FIG 8.19B Action potential happens at the axon, it reaches the length of the axon terminus and releases the synapse at the synaptic cleft (as long as there are neurotransmitters ??? 1. neurotransmitters can be returned to axon terminals for reuse or transported into glial cells 2. enzymes inactivate neurotransmitters o the enzyme degrades the neurotransmitter so that it is no longer able to pass the signal onto the post synaptic cell 3. neurotransmitter can diffuse out of the synaptic cleft o if you get far enough away from the receptor then there is no response (it doesn’t just diffuse into the extracellular fluid but can also be diffused into the blood vessel) So if the neurotransmitter is taken away from the receptor, there is no interaction so the signal is cut and that stops continuous firing Smooth muscle might contract when exposed Structure of autonomic division: Ganglion: a cluster of cell bodies as part of the peripheral nervous system In the diagram, for simplicity, there is only one shown b ut in reality you would have a lot of cell bodies clustered together and it’s part of th e autonomic system so it’s called the autonomic ganglion KNOW THE TERMS PRE-GANGLIONIC AND POST-GANGLIONIC The short pre-ganglionic axons emerge from the spinal cords, and they have very short axons (very short length) and the autonomic ganglion descend down the vertebrate column and that reaches the post-ganglion neuron that is much longer and is able to reach the target cell The pre-ganglionic (instead of the middle of the spinal cord) you have these exiting from the brain stem (cranial nerves) and in the bottom of the spine section near the pelvic region - FIG 11.5 The target tissues for the sympathetic and the paras ympathetic are the same o Neurotransmitters (FIG 11.6) Describe that is happening at the different s ynapses in the sympathetic and parasympathetic, what neurotransmitters are released and what the receptors involved do
BE COMFORTABLE WITH THESE TWO PATHWAYS: MIDTERM QUESTION Post ganglionic neurons are looked at when you are discussing the target tissue FIG 11.7
Concept check queston on above diagram: it is a sympathetic pathway ^ (at the target tissue is where you see the difference, if this was p arasympathetic, you would see acetylcholine being released)
Receptors: when we take a look at the target tissue for the autonomic ganglia we find receptors it’s not just a signalling molecule that gets released, the receptors are also important because there are multiple types with various purposes 1. Adrenergic receptors are on the tissue cell (target tissue) that will respond to the autonomic post ganglion sympathetic neurons - BE FAMILIAR WITH THE BINDING DIFFERENCES BETWEEN EPINEPHRINE (E) AND NOREPINEPHRINE (NE) 2. cholinergic reecptors the normal ligand is acetylcholine which stimulates both nicotinic and muscarinic receptors nicotinic receptors: the antagonist nicotine binds to this and causes the same type of response ^ ACETYLCHOLINE IS COMMON IN BOTH muscarinic: muscarinic as an antagonist causes the same response in the muscarinic receptors nicotinic receptors are always excitatory so it is a direct response bec ause the receptor is an ion channel so it opens up muscarinic receptor is coupled with G proteins so it may cause different responses whether it opens (excites) or closes (inhibits) the ion channels Fig 11.9 Rest-and-digest: parasympathetic Another word for epinephrine is adrenaline! FIG 11.8 (ADRENAL MEDULLA)
Fight-or-flight: sympathetic
Lecture 8 Q: T/F Somatic sensory neurons control skeletal muscle a. true b. false (not sensory, somatic motor neurons!) when the somatic motor neuron fires and moves down the length of an axon, it leads to firing of an action potential inside the skeletal muscle (which causes contraction) - so how we don’t cause the skeletal muscle to contract is to not send a neuron; no neuron fired means that no signal is delivered
Fig 11.10
skeletal muscle fibre : same as skeletal muscle cell (there are two indicated in the diagram) each fibre is controlled by a single cell but a single somatic neuron is able to control multiple cells (could be thousands) the terminal bouton is where the somatic motor ne uron attaches to the cell and spreads out a little bit (it looks like when you are trying to spread out the jalepeno cream cheese) motor end plate is a folded back and forth part of the skeletal muscle fibre - nicotinic type ACh receptor channels (THE NICOTINIC ARE ION CHANNELS: which becomes very important) Neuromuscular junction is another term to describe the synpase between the somatic motor neuron and the skeletal muscle fibre (divided into 3 different stages/parts) an action potential arrives at the axon terminal, causing voltage gated Ca+ channels to open, calcium entry (influx) triggers release of ACh by causing synaptic vesicles to fuse with the presynaptic membrane and release ACh into the synaptic cleft AChE is an enzyme that degrades ACh, when it degrades the ACh, there is no more signal in the cleft so the signal can’t be delivered the channel remains closed in it’s normal state an d waits for the signal to come in (ACh) we need two ACh molecules to bind to the nicotinic receptors, which is an ion channel, so when the channel opens (it allows both the passage of sodium and potassium) - there is an unequal movement of sodium/potassium: more sodium ions are coming into the cell than potassium can leave the cell - the sudden influx of sodium will depolarize the cell and we get a signal/response
FIG 11.9
autonomic targets: smooth and cardiac muscles, some endocrine and exocrine glands, some adipose tissue a. parasympathetic pathway b. sympathetic pathway a and b share the same pre-ganglionic/post-ganglionic signal but when it hits the ganglion that is where the difference occurs (between nicotinic vs muscarinic receptors) c. adrenal sympathetic pathway modified sympathetic ganglion (CHROMAFFIN CELL) that responds to a signal from a preganglion neuron, which is without the chromaffin cells firing, the epinephrine would not be released somatic: skeletal muscle UNIT 3 MUSCLE: smooth/cardiac: autonomic system, Stores and hydrolyzes ATP, which leads to a contraction because of the proteins in the cells when you cut/hydrolyze that ATP, heat is released which contributes to our maintenance as homoeothermic animals FIG 12.1 the skeletal muscle is attached to the bones/muscles of the body so when it contract is when we find movement in the body - the long cylindrical (skeletal muscle cell) has multiple nuclei (maybe even hundreds) and it has a repeated light-dark banding pattern which is called as striations
smooth muscle is called smooth because there are no striations (no light and dark banding patterns, they have the same proteins that cause contractions but there are no certain arrangements of these tissues) cardiac muscle only find in the heart, it has a very important job to provide a force of contraction so that the heart can pump (the pumping increases the pressure of the blood inside the heart which causes it to flow outside and throughout the body) - highly branched and also the second of two types that is striated think of it as her right and left hand as each different cardiac muscle cell, when you cross your hands (not arms: hands) there is an interdigitated disk in the middle through which one cell communicates with another cell (gap junction in the interdigitated disk so that the signals pass through very rapidly) A tendon is made up of connective tissue, lots and lots of extracellular matrix is found in connective tissue (and there is lot of collagen p resent: in a tendon it is found in a cable like form) FIG 3.13 FIG 12.3a https://www.google.ca/search?q=skeletal+muscle+structure&safe=strict&espv=2&biw= 1440&bih=708&source=lnms&tbm=isch&sa=X&ved=0ahUKEwiShbjsquDRAhVSPJA KHZdaCsEQ_AUIBigB
epimysium: outer most layer of your skin if we peel that away, we find bundles (bundles of cells called fascicles) the fascicles are covered by a connective tissue layer called perimysium (the white-ish tissue that wraps around the bundles of fibres: muscle fascicles) - the perimysium is where the nerves and blood vessels are found imagine the room: each one is a single muscle fibres (cell) if you put your coat together, you are covered by a endomysium and if you divide the class, half of it is one fascicle and the other half is another fascicle the class (bundle of fascicles) are covered by the walls of the room (perimysium) and the building is the epimysium (the outer most layer) ! - endomysium (surrounds a single muscle cell) FIG 12.3b sarcolemma is the cell membrane of the skeletal muscle fibre - myofibrils are the protein that are responsible for the contractile and elastic movement the modified endoplasmic reticulum encircles the myofibrils when you play with clay, if you poke a finger into it, and take it away you see a dent in the clay (that hole is the T-tubule, now if you poke a hole in somewhere else, that is another T-tubule, but the clay that is : example the division between the two sections of the classroom is the lumen, and the first chairs on either side are the T-tubule) - the second chair is the terminal cisterna which holds on too sequester/holding on to Ca2+
a triad is all the way from the second chair of one side of the class, the first chair on that side of the class and the lumen in the middle (the aisle) and the first and second chair on the other side of the class) the combination of the terminal cisterna , T-tubule and lumen is called a triad the function of T-tubule: the release of ca2+ from the SR helps in the contraction of the muscle fibre
Lecture 9 Which of the follow are striated muscle? a. Smooth b. cardiac c. skeletal
d. ‘a’ and ‘c’
e. ‘b’ and ‘c’
Myofibril: long cylindrical structure found inside skeletal muscle fibre, so when you focus on one individual myofibril, you find proteins: actin and myosin - When these proteins come together, there is a contraction in that muscle - The actin/myosin have to have some way to be controlled/regulated - We have to understand how actin/myosin are organized into fibrils, and how they cause the muscle to undergo contractions Regulatory proteins: regulate whether or not a contraction should be allowed to happen inside a myofibril (tropomyosin and troponin) Accessory proteins: help organize the myofibril What causes striations? Skeletal muscle fibres under the microscope have a very organized unitof proteins which gives rise to a light-dark-light-dark banding patterns, called striations - Names were given to the repeated structure of the organization of the proteins when witnessed under the microscope: KNOW THESE: be familiar with the various structure in the repeated u nit Z-line (disk) I-band (given name according to how they look under the microscope and how light reflects, so the I band is the light band in the light-dark banding pattern) A-band (dark: this is dark because there is too much protein that is scattered to allow light to pass through uniformly so it looks darker) - There is a slight area within the A band that is a little lighter (not as light as the I band) known as a H zone Course notes: page 53 The Z-line passes through an area that is pretty light under the microscope, that lighter area is called the I-band The thicker lines are the dark part of the light-dark banding, called the A band - The repetition of the structure again and again is called the sarcomere
Figure 12.3(?) b and d The two main contractile proteins are organized in a way that gives rise to the striations, in not just skeletal muscles but also cardiac muscles Make a fist, and hold your arm out at an angle (similar to the picture on page 54) - The fist is the myosin heads, which extends to the outer part of the thick filaments - And your bicep area is the tail region, which orient towards the middle of the thick filaments - From your wrist to your elbow is the hinge region which allows for very flexible movement of the heads Now if you hold both arms out (like a titanic pose) your body becomes the ‘M’ line and the tails would have orient themselves towards the middle and attach to the M-line Binding sites: - Myosin binding site is ATP - Actin binding site is (?) Actin is the only protein (very important) found within the thin filament, it is a contractile protein which forms the basis of the thin filament but the regulatory proteins help to complete the thin filament
Fig 12.3f
Cross bridge (KNOW THIS) The myosin heads interact directly with actin filaments, these interactions are called c ross bridges Fig 12.8
I-band The Z-disk goes right in the middle of the I-band so it divides the I-band in two parts, where one part interacts with the sarcomere and the other part of the same I band interacts with the neighbouring sarcomere The center part of the A band (H-band) is where you would find think filaments only The tails orient themselves towards the M-line
The outer edge of the A band is the only part where you find the overlap between thick and thin filaments , single thin filament is always surrounded by three thick filaments within the particular structure Titin very large proteins: Fig 12.6
Titin: helps relax the force by providing elasticity
Nebulin: the tropomyosin is like a rope so there isn’t much you can work around to make sure the globular actins line up along the thin filament for good organization An indentation (like the align in the middle of the room) in the sarcolemma is called T -tubules (tranverse tubules) - They have a job: they conduct action potentials (getting the action potential into the skeletal muscle fibres) Mechanisms of muscle contraction - Early theories suggested that muscles were made of components (molecules) that shorten when activated and stretch at rest Researchers knew that myosin shortens when heated (steak) so th ey assumed it was the active component - Steak is flesh (skeletal muscle) too much heat will cause the steak to shrink, because myosin shrinks when heated which was the early theory It wasn’t until 1954 that two researchers questioned that if the theory were true that you would see changes in the A-band because that is where you find the myosin, but they realized that the A- band wasn’t changing in length at all - So what other explanations did they have? They proposed the sliding filament theory (which comprises of the thin and thick filaments) - At rest you have the conformation of the A-band and I-band in the sarcomere arrangement and at the outer edge of the A band is an optimal degree of overlap of the A and I band with the heads of the myosin pointed towards the thick filaments - The myosin proteins pull the actin thin filaments closer towards the M-line which brings the Z-disk closer together - There is no change in the size of the thin or thick filament, they are just sliding closer to the M line
the myosin can pivot because of the hinge region Cross bridge cycling: what happens when a muscle undergoes contractions which causes sliding filaments to slide past one another (we called it cross bridge because that is where actin and myosin come together) Power stroke: now myosin has pulled actin alon g with it as it pivots back to the 45-degree angle Relaxed muscles are mostly in step 2 (myosin heads at 90-degree and weakly bound to an actin molecule) During contraction the myosin heads don’t move simultaneously (usually 50% moving, 50% are attached) What would happen if all the cross bridges released together? - The thin filaments would slide back to where the y were - Thin filaments would slip back into their orginal positions and the contraction would not occur - Imagine you are play tug of war, the hands of your team members are myosin heads so you would not want all the hands to give up at the same time because then the rope would return to it’s original position
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Remember when you play tug of war, you play hand over hand so one hand is more predominantly pulling than the other you move hand over hand and that’s how the myosin heads move and pull (if you were to pull with both hands and release both hands (in order to move them forward) you would end up letting go of the rope completely So one hand at a time
Midterm review: The type of tissue provides structural support and barriers: connective tissue Epithelial: protection and exchange of materials The maintenance of a relatively stable internal environment is known as homeostasis Which of the following allows direct cell to cell commun ication? Gap junctions Neurons that lie entirely within the CNS are called interneurons Which of the following glial cells has extensions that contact b lood vessels in the brain? Astrocytes Microglia: look for damage tissue Ependymal cells: lining the cavitity separating the CNS Satellite cells A collection of neuronal soma outside the CNS is called a ganglion and within the CNS is called a nucleus Concentration gradient between a cell membrane is more K ions inside and more Na ions outside The value of the resting membrane potential is -70 The resting membrane potential depends on each item below expect: Greater membrane permeability to anions rather than cations Other options: (concentration of Na inons) (greater permeability of plasma membrane to k ions) (greater leaky channels of K ions) a neuron under the influence of a neurotransmitter that opens k channels will be less likely to cause an action potential a threshold stimulus immediately fully opens voltage-gated sodium chann els influx of na ions in one area of an unmyelinated axon initiates which of the following events? AP in that area and depolize area to threshold Action potential progration in myelinated axons is known as salutatory conduction
Which of the following differentiates skeletal muscle from both cardiac and smooth muscle? Multinucleated fibers (both are striated) (all muscle can generate force) which of the following connective tissue sheathes directly cove r skeletal muscle fascicles? Perimysium Terminal cisternae sequester Ca ions Which of the following are contractile proteins in muscle? Actin and myosin What triggers myosin to release from actin in the cross bridge cycle? Binding of ATP
Which of the following are energy sources for ske letal muscle contraction? a. Oxidative metabolism b. Glycolysis c. Creatine phosphate d. ‘b’ and ‘c’ e. ‘a’ ‘b’ and ‘c’ Oxidative vs glycolytic: the primary production of ATP - Red coloration is accumulation of protein (myoglobin) found in the oxidative fibres - Myoglobin contains a heme- (like hemoglobin) group that is able to bind reversibly to oxygen, and store oxygen within the cells that are for oxidative fibre metabolism type - The rate of the diffusion of gases is limited by the distance, so the farther the distance, the lower the rate of diffusion, which is why the ox idative fibres tend to be smaller whereas the glycolytic fibres are more wider (because the rate of d iffusion doesn’t have to be too small) How quickly can a myosin protein hydrolyze/cut an ATP fibre? - Fast twitch fibre: split ATP fibre, because they are able to do that, they are able to go through a cross bridge cycle - When that is able to occur very quickly, you are able to have the sarcomere undergo contractions/movements at a quicker pace - The slower fibres have an isoform (version of the protein) which is different so it is not able to hydrolyze as fast as possible
No tension originally developed, but when the myosin is going through the cross bridge cycle (rubbing, pulling, grabbing the thin filaments to slide past one another), tension increases because that is the contraction phase -
The relaxation phase is when the myosin is no longer to interact with the actin
There is a delay between when we get a stimulus and actually see a contraction – latent period - Our action potential starts on a motor end plate Which type of muscle has a higher rate of Ca removal from the c ytosol? - FAST TWITCH MUSCLES (WHY: KNOW WHY) A single twitch is a single relaxation – contraction cycle The outer edges of the A band is where the myosin and actin (thin and thick filaments) and how much they overlap is proportional to the amount of force generated - For a single skeletal muscle fibre (a single sarcomere) that is an o ptimal overlap to generate a certain amount of force A single twitch does not represent the maximum force that a single muscle fibre can develop - The stimulation always comes from action potentials, that arose from the stimulus of somatic motor neurons - So the rapid rate at which somatic motor neurons stimulate action potentials (which in turn stimulate muscles: the force that is generated is higher) CONCEPT KNOWN AS SUMMATION FIG 12.16 When a cell keeps repeatedly getting stimulated but not quick enough then you see three different twitches - When the stimulus summate (because they happen close enough in time to cause the cell to experience a greater force before returning to rest - If the stimulation happens before the cycle has co mpletely fully relaxed, the cell will undergo a greater force of contraction, a cell will continue to be stimulated until the maximum tension that the muscles can feel has be en reached Tetanus: when a skeletal muscle cell reaches it’s maximum force (tension) of contraction Unfused tetanus is when you have reached the maximum amount of tension, but there are chances when the cell is ever so slightly allowed to relax before contracting again - The period where the tension is building up to the maximum amount is called summation - So the tetanus is when the max tension has been achieved, summation is the period leading up to that
The cell gets hit with a rate of stimulation that was so fast that it reached the maximum tension, and at that point too, it keeps going (horizontally) maintaining the maximum tension, until fatigue causes the muscle to lose tension despite continuing stimuli Fig 12.17 Which will be recruited first oxidative or glycolytic fibres? Oxidative We have more motor units for fine movements because we wanna be able to tweak and refine what contractions are happening Recall skeletal muscles are attached to the bones of the movement, but there are different types of movements of the skeletal muscle which results in different contractions - There are two main types: isotonoic and isometric
A single motor unit consists of a. Somatic motor neuron b. Muscle fibres of different types c. Muscle fibres of the same type d. ‘a’ and ‘b’ e. ‘a’ and ‘c’ To hold the arm stationary at 90 degrees, the rotational force created by the contracting biceps must exactly oppose the downward rotation created by the forearms weight Rot force up = rot force down Biceps force x 5 cm = 2kg x 15 cm Biceps force = 30 kg*cm / 5 cm = 6 kg Sphincter: smooth muscles that are organized in a ring like structure that are able to close/open an opening allowing passage when they relax or contract The small intensitines contract have a circular arrangement a round the contraction Multi unit arrangement All the cells get stimulated thanks to the minority of cells that start interacting due to the original stimulus Just before labour (pregnancy) there is a remodelling of the cell from a multi unit type to a single unit type, this happens because it is believed so that the contractions are happening together as one unit rather than one part of the uterus contracting while the other isn’t Contracts more slowly and for longer periods of t ime than skeletal/cardiac muscle
What would happen if your bladder were lined with muscle organized in sarcomeres? - When the balloon fills up, as it fills up with the liquid that is transferred from the kidneys, if it were organized in sarcomeres, you wouldn’t get any tension developed beause the thin filaments can’t be grabbed on by the myosin heads, so since it is una ble to grab there aren’t that many contractions happening Ca coming from outside the cell causes a release of the intracellular calcium storage causing a higher level of intracellular calcium - Calmodium binds to the calcium (inside the cytosol) and forms a calcium calmodulin complex which activates an enzyme known as myosin light chain kinase (MLCK) - The job of this protein is to add a phosphate group onto something (kinase : phosphorylation addition) The role of myosin being regulated via phosphorylation in smooth muscle is VERY different from actin being regulated through troponin/tropomyosin in skeletal muscle What would happen to contraction if you put a smooth muscle cell in Ca2+ free solution? - You wouldn’t get any contractions - What triggers contraction is the influx of Ca2+ from the extracellular environment, so there isn’t any calcium to come into the cell initially which causes a lack of contraction Calcium can be pumped out of the cell through a sodium calcium ATP, Or you can use an influx of sodium coupled with an efflux of calcium Either way calcium has to get out of the cell Which causes a break up in the calcium calmodulin complex, which inactivates MLCK There is another protein that is always active in the background, known as myosin light chain phosphatase, which take the phosphates away from the myosin heads so it goes from activated to inactivated
Q: The cardiovascular system a. Assists removal of wastes b. Distributes respiratory gases c. Functions in transports of hormones d. ‘a’ and ‘b’ e. ‘a’ ‘b’ ‘c’ Figure 15.1 (Oxygen poor blood: represented in blood coloration) - When this blood leaves the heart, it moves towards the arteries
As the blood drops to the heart, it has too little pressure to travel back wh ich is why we need two pumps in a series. The tip (of a cone) when you hold an ice cream cone is known as an apecs - The heart also has a conical shape, with a slight tilt, so it also has it’s own apecs, and the larger in diameter (the top part: where the ice cream goes) is known as the base - So the superior part of the heart where the blood vessels attach is known as the base - The inferior portion of the heart is known as the apecs The heart is surrounded by a double membrane stack (The pericardium) - The inner membrane rests exactly right on top o f the heart - Whereas the outer membrane is seen attached to retractors that seems to be pulled away from the inner membrane (leaving a black space in the diagram) but in real life there isn’t any space between the two membranes The coronary arteries can get blocked, depending on where the blockage occurs, the amount of damage done to the muscular system, creates a shortage in blood suppy to t he heart which causes a heart attack - BUT THE IDEA TO TAKE HOME IS: the coronary artery has it’s own set of arteries/vessels that supply blood to the sac When you see heart’s in diagrams, it’s like you are looking at the heart of someone else who is standing directly in front of you, facing you. Figure 14.5 The tricuspid is on the right side (the bicuspid is o n the left) - These valves have specialized cords that connect the AV valves to the inner lining of the ventricle - The cords make sure that the valves don’t end up going back into the atrium (preventing backflow of blood) Prevents the backflow of blood that has left a ventricle and entered into the artery Figure 14.7 During ventricular contraction, the AV valves remain closed to prevent blood flow backward into the atria (The bicuspid or the mitral valve shuts) When the ventricle is relaxed (the time of the cycle when it is filling up with blood), we want the blood to flow from the major blood vessels that are brining blood to the heart, past the atria and into the ventricles (The blood from the pulmonary veins) The semilunar valves prevent blood that has entered the arteries from flowing back into the ventricles during ventricular relaxation
The spiral arrangement of the cardiac muscle allows the maximization of the blood (like a towel that is wet, when you want to dry it, you take both the ends and twist it, instead of the just smushing the towel together) - This twist motion (isn’t exactly what happens in the heart but) allows the spiral shaped cardiac muscles to deliver the maximum amount of blood during contraction Be familiar with both auto rhythmic cell and contractile cell be cause action potentials in both of these look very different! The time period for the action potential in pace maker cells (depending on how many times it beats per minute which is individual to each and every one of us) EVERY CARDIAC MUSCLE CELL (PACEMAKER OR CONTRACTILE ARE CONNECTED TO THE GAP JUNCTIONS) - The fastest cells in the SA node are what drive the heart rate Figure 14.19
Q: The unstable membrane potential observed in pacemaker cells is due to: a. Na+ efflux / K+ efflux b. Na+ influx / K+ efflux c. Na+ influx / K+ influx d. None of the above
If = funny ion channels. Coordination of contraction 1% of cardiac muscles cells are not contractile - Involved in electrical excitation of heart > conduct ing system - Initiate heart beat - Allow it to spread rapidly throughout heart - Connected to other cardiac cells via gap junctions The heart contracts in a very coordinated way to effectively pump blood out of the heart FIGURE 14.13 Pathway of conduction: Pacemaker cells in the sino-atrial (SA) node generate a ction potential
The pathway always start with the fastest cells in the conducting system, which are in the SA node – because of their funny ion channels, they are able to spontaneously generate action potentials which then spreads to neighbouring cells through gap junctions 1. Internodal (in between the SA and the AV node) pathway connects the SA node to the atrioventricular (AV) node in the floor of the right atrium 2. AV node action potentials enter more fibres called the BUNDLE OF HIS (AV Bundle) The bundle divides into left and right bundle branches PURKINJE FIBRES (rapid electrical signalling of action potentials) o Spread out into contractile cells (of the ventricles)
Figure 14.14 The ventricular septum is the wall that divides the light and right ventricle Events in conduction of an AP 1. AP fired from SA node 2. Spreads to adjacent cells > via gap junctions 3. Rapid spread through cells of internodal pathway a. Spread is slower through contractile cells of atrium (than the pac emaker cells found in the internodal pathway) WHY? ANS: Resistance, contractile cells are supposed to contract, so the flow of the charge that hits the chalk material of the contractile cells required to contract, there is a delay because of high organization and make-up of contractile cells 4. Signals passed through AV node only at AV junction -> layer of fibrous material acts as an insulator prevents electrical signals from atrium -> ventricle a. AV node only pathway for AP 5. Signal is slightly delayed by AV node: WHY? To ensure atrial contraction is over 6. Signal is carried to bottom of the heart (APEX) through Bundle of His Why is it necessary to conduct signals only throug h AV node & bundle of his? [Like a tube of hand cream, if you want the cream to come out, you press from the bottom all the way to the top… so in order to maximize the blood flow, the AV node at the bottom of the right atrium leading to the bundle of his is required to carry the signal all the way down to the apex and to the purkinje fibres] So that signal for contraction initiates at the bottom of the heart This ensures the contraction drives the blood up since it leaves the heart at the top
Abnormal heart rhythm: arrhythmia can develop a. When another part of the heart takes over as pacemaker b. When the SA node develops an abnormal rate/ar-rhythm c. When the normal conduction pathway is interrupted Bradycardia: slow heartbeat > less than 60 bpm: fatigue, d izziness, light-headedness, fainting (The normal heart rate is somewhere between 60 – 100) May occur as a result of physical conditioning (e.g. endurance in runne rs)
Serious cases result from blockages in conducting pathways of heart Treatment: electronic pacemaker (Unable to conduct enough blood to various regions of the body for proper functioning)
Tachycardia/Tachyarrhythmia: rapid heart beat > more than 100 bpm Palpitations, rapid heart beat Ventricular fibrillation (V-fib) Disorganized contraction Ventricle quivers > heart cannot pump any blood Collapse and sudden death follows unless medical help is provided immediately Treatment: can be converted into normal rhythm with electrical shock (defibrillator)
Atrial fibrillation Atria quiver instead of beating effectively Blood isn’t pumped out completely when heart beats Blood pools and clots : if lodged in artery in brain : stroke (coronary arterties?) 15% of strokes occur in people with A-fib Treatment: atrial contraction is unimp. for cardiac function except during strenuous exercise therefore treated with aspirin and warfarin: interfere with blood clotting, reduces risk of stroke
Electrocardiogram: use 3 leads to make “Einthoven’s triangle” - Clinically use 12 ECG leads -> given information abou t different regions of the heart Figure 14.15 Each and every lead is like a camera angle, that gives you shot of the heart to depict what happens (Lead consists of two electrodes, one positive and one negative) - Electrodes are attached to the skin surface FIGURE 14.15D When we see deflections either above or below the baseline, we are seeing Components of ECG: 1. Waves Deflections above or below baseline Electrical events 3 major waves: a. P wave: depolarization of atria b. QRS complex: ventricular depolarization c. T wave: repolarization of ventricles
The ECG diagnostic tool Cardiac cycle Two phases: Systole: contraction Diastole: relaxation
Q: In the cardiac cycle, relaxation is called a. Systole b. Diastole Possible questions on systole/diastole: ventricular and atrial Factors influencing heart rate: Parasympathetic and sympathetic are direct via the nerves versus plasma epinephrine reinforces The stretch of the sarcomere gives more binding sites for the myosin (but there is limited elasticity meaning that you can’t stretch too much) The walls of blood vessels can be made up of multiple layers, Important to note which type of blood vessels contain which type of layers (in the walls) because not all type of blood vessels has all type of layers -
Blood vessels are tubes that are surrounded by walls (each with different layers) But the center of the tube is the lumen (the inner central cavity)
B/D – elastic and fibrous connective tissue are each individual layers of connective tissues The elastic is called elastic because it has the ability to stretch and then recoil When the vascular smooth muscle layer contracts, it takes the lumen and the diameter of the lumen shortens (vasoconstriction) There are five types of blood vessels – make a note of the different type of wall found in each a. Artery (carry blood away from the heart) so it must be able to withstand blood at it’s highest pressure (when the blood is being pushed out of the heart through the pumping motion) ALL FOUR LAYERS b. The arteries start to branch as it moves away and away from the heart and the pressure in the blood starts to decrease (arteriole) are able to regulate the flow of blood through them thus they are able to dilate/constrict in order to direct the blood flow Smooth muscle lining and endothelial cell lining (what faces the lumen) c. Gas exchange happens in capillary beds but for adequate amount of exchange to happen you must have a small diameter between the different cells Thus the capillary is very small, and made up of Layer of endothelial cells
Diffusion and gas exchange are correlated to distance so the further away the gas exchange is going to have to travel, the less diffusion you will have thus it is important that capillaries are small d. Venule: small veins that branch out from the capillaries inner most lining of endothelial cells and fibrous connective tissue lining e. Vein – blood is being carried at a very low pressure but we want the blood to flow nicely thus All FOUR LAYERS
Pressure always decreases by friction Adjustments are made by changing r – the radius of the blood vessels - Arteriole (peripheral) are found in the systemic ___ and they are very good at regulating the flow and resistance of the blood, so there i s a really good shift in the flow of blood at the arteriole level With regards to pressure gradient and resistance, we can understand the flow of blood as it flows through our network of blood vessel (F directly proportional to pressure gradient (from high to low, so at the exit and entrance of the heart, respectively) - Setting up that pressure gradient will cause flow to occur - Inversely proportional to radius (1) Systolic and (2) diastolic pressure: 1. The time when the heart is contracting 2. The time when the heart muscles are relaxing
As the pressure gauge increases, the pressure of the cuff i ncreases, so that when it squeezes on the outer part of your arm, it is hopefully squeezing that artery enough to momentarily block any blood flow through that artery - As you release, VERY SLOWLY, the air from t he cuff, you have to listen very carefully - Now suddenly, the artery that had been blocked is now being open so you get a very narrow passage through which blood is allowed to pass - When you don’t hear the turbulent sounds at all, you have your diastolic pressure Figure 15.6: Changes in pressure that is recorded by tracking in di fferent areas of systemic circulation of the blood in the cardiac system Low pressure when it relaxes, high pressure when it contracts Be familiar with the MAP formula If we change cardiac output, we will be able to influence or change in mean arterial pressure (MAP) - Either heart rate or stroke volume will influence cardiac output Baroreceptors: pressure receptors (barometer: the pressure of the atmosphere) ‘baro’ = ‘pressure’
Make sure the pressure is adequate enough so that it can undergo the journey to supply oxygenated blood to our very oxygen dependent brain - Mechanoreceptors: some sort of physical force that is applied to a cell to activate the initial signal in a cell Figure 15.14
What is blood? Plasma: fluid portion of the blood Red blood cells -> erythrocytes - The job of the hemoglobin is to be able to bind reversibly to gases, mostly oxygen and carbon dioxide for transport White blood cells -> leukocytes - Lymphocytes are a type of white blood cell, but leukocytes means ‘white bloods cells’ (all inclusive) - If you take a sample of the blood, separate the white blood cells and analyze them, you discover that anything that is a foreign identity (no matter what), the WBC will ingest it through phagocytosis o Basophils are immature mast cells, allergies are mast cells (overreacting to something that shouldn’t be considered harmful to our body)
Never let monkeys eat bananas (NLMEB): Neutrophils, lymphocytes, monocytes, eosinophils, and basophils are our different types of leukocytes Platelets - thrombocytes, involved in blood cotting Derived from megakaryocytes: pinch off and have no nucleus Pinched off little extensions that (without stimulus) are inactive, thus always found in the blood
RBC need adequate amount of hemoglobin (it is made up of four protein chains (subunits)) Called globins, because they are globular (round, spherical) proteins rather than linear protein chains Why do we see a different form of foetal (fetus) hemoglobin and the maternal hemoglobin? - The foetal hemoglobin needs to pull more oxygen away from the maternal, so with better binding abilities, it is better able to scoop the oxygen away as the mother’s hemoglobin is their only way of attaining oxygen - Whereas a mother gains oxygen when she births in (therefore, the babies hemoglobin needs to be stronger than the mothers so that the oxygen from the mother’s is efficiently transported to the babies blood) Figure 16.6 We can explain the saturation of hemoglobin using a hemoglobin oxygen saturation curve
Capital P represents the partial pressure of the gas, i n this case oxygen which describes the amount of gas that we will find in the system
Q: Platelets are also known as which of the following: a. Erythrocytes b. Megakaryocytes c. Leukocytes d. Thrombocytes e. None of the above Figure 16.2 Figure 16.4c The mechanism by which we form thrombocytes Figure 16.7b/c As the damage occurs, platelets activate and group together to form something called a platelet plug The thrombocyte goes from a smooth looking surface to a activated platelet form When EPO enters the bone marrow, it acts on the stem cells and causes the maturation/formation of RBC (red blood cells) Figure 16.9
Know the common pathway: where the instrinsic and the extrinsic meet to f orm the blood clot Areas in the lungs that are geared towards gas exchange are known as alveoli The bronchi branch further and further into bronchioles, that branch further into terminal bronchioles Figure 17.2
Q: Which of the following are components of the respiratory system? a. Exchange surface b. Conducting system c. Pumping system d. ‘a’ and ‘c’ e. ‘a’ ‘b’ and ‘c’ The thickness of the ventricular walls is different between the contractions on the left side of the heart vs the right side of the heart - eventually the pressure develops in the right chamber, which leads to lower pressure in the blood as it leaves the heart
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the blood should have enough pressure to defy gravity, f low all the way around the body and return back to the heart
Boyles law: pressure is inversely related to volume Figure 17.5
This orange blob is the protein channel known as the NKCC channel (because it transport one sodium, one potassium, and 2 chlorides) If the cilia are paralyzed, they cant move and cant engage in the movement in the respiratory tract If the chlorine channel doesn’t work due to a mutation, where it is unable to pump chloride, if chloride can’t get pumped out, sodium wont follow, so then water won’t follow When we expand the chest, we increase the volume of the chest, so the pressure within the chest decreases and gases flow from an area of high pressure to an area of low pressure If there is a break in one of the way pleural membranes, atmospheric pressure gets introduced and the individual suffers from collapsed lungs Compliance, resistance and elastis are factors that impact breathing When the lungs are stretched, it allows the alveolar cells to release surfactants easier Fetal development puts lung development on hold because really the lungs aren’t needed until the baby comes out and takes it’s first breathe, so when an individual is born premature the
type 2 alveolar cells aren’t functioning at i t’s full capacity (if born more than 6-8 weeks prematurely) The cells aren’t mature enough to produce an adequate amount of surfactants so the lungs themselves don’t have the ability to be compliant, which causes difficulty in breathing A normal lung is like a balloon, it has elastance so that when you blow up a balloon, it expands and then when you let it go, it goes back to normal (air is being pushed out by itself) - in an emphysema lung, imagine a paper ball - you blow it up and it expands but then when you let it go, the air doesn’t get pushed out so you have to forcefully squish the bag with your hands to get the air out (i.e. breathing is forced) FIGURE 17.7
Q: The diaphragm can initiate contractions spontaneously a. true b. false Venous PCO2 increases, but arterial doesn’t Arterial PCO2 set by alveolar PCO2 Venous PO2 decreases but arterial doesn’t Chapter 17 and Chapter 18 – Tonight’s Quiz When you suffer from an autoimmune disorder, it is because your body is recognizing foreign particles that are actually not that dangerous but the body perceives it to be, causing a greater reaction than that would be expected Bacteria can enter the body, remember what protects the inside of our bodies from the outside world is skin, but even inside our body, our body is protected because the lumen of the multiple pathways that you can take to the inside of your body is separated from the rest of your body (i.e. the respiratory system lumen (airways), the oral system lumen (digestive trac t)) - The key message to take is that bacteria can survive in intracellular and extracellular conditions - Antibiotics only target bacterial cells - You can not treat a viral infection using an antibiotic A course of antibiotics always needs to be finished b ecause you need to ensure that there are no survivors at the end, because otherwise you might develop strains of resistant bacteria to that antibiotic, which down the road leads to problems because then you are unable to handle it with just an antibiotic There is a net movement of fluid from the plasma of the blood into the capillary and out into the tissues (?) Lymphatic capillaries pick up the extra little bit of fluid and ultimately (through a long path) get right back to venous circulation, where the fluid returns back to the plasma of the blood - The flow of the lymphatic is through the movement of your body (there is no pressure gradient that supports the circulation) Lymph nodes : FIGURE 24.3
The green lines drawn are lymphatic vessels (the movement of these body parts causes the lymphatic fluid to circulate within these vessels) With regards to immune system function, here is the job of the bone marrow and thymus: 1. Bone marrow: there are strategic parts in the human body where the bone marror is activated (hemapoiesis: collection of all types of blood cells) - RBC, WBC, and platelets produced here - There is a specific type of WBC called B-cells that matures in the bone marrow - When the T cells are produced in the bone marrow, they are still considered immature - So they travel to thymus 2. The T cells reach the thymus and mature so that they are able to progress and continue their function (which will not happen until the maturation process is complete) Primary organs are those that produce T cells and B cells and help to undergo maturation (bring it to finish) - Secondary organs job is to help the cells carr y out their function Never Let Monkeys Eat Bananas – Helps you recognize different types of RBC
Q: All white blood cells are called lymphocytes a. True b. False Lymphocytes are a type of white blood cells, with multiple types of lymphocytes! B lymphocytes (B cells) - Mature in the bone marrow (Bone marror: thus B cells) T lymphocytes (like every other cell in the blood) is produced in the bone marrow, but it undergoes a maturation process in the thymus (THUS T cells) The Y shaped proteins (the arms are what recognize the antigen) and the stem stays of the B cell, known as the B cell receptor If the antigen is being presented on the surface of the cell (via the MCH proteins) MCH proteins are expressed on the surface of the cell and will show antigens - Self and non-self Class 1 (found on all nucleated cells)
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A cell in your body that doesn’t have a nucleus: blood cell (thus these don’t represent Class 1 MHCs) Class 2 (found on APCs) Pretend you have an epithelial cell in your nasal passage that gets affected by the viral cell, the epithelial cells will take some of the viral proteins and via the MCH proteins will display the antigens to the surface of the cell (the non-self antigens: antigens that are displayed on the surface of a cell but are not belonging to the cell) o This sends a red signal to the body’s immune system because the antigen detected is a foreign material (certain MHC proteins in the body: a large amount are quickly able to detect the smallest of foreign bodies) Two main types of T cells: - Kills and expresses appropriate Ag Back to the epithelial analogy: as a viral infected cell, this cell will try to divide and repopulate, but it has a Class 1 MHC that it will use to display the viral antigens on the surface of the cells, the cell that can respond to that viral antigen (through the immune system communication processes) and the killer T cell will kill the target (viral-infected) epithelial cell through programmed cell death (apoptosis) Antibodies : bind to antigen (Ag) as a signal Cytokines : affect growth or activity of other cells Innate and acquired (adaptive and specific) immunity Humoral immunity (antibodies – Ab) The skin isn’t the only part of your body that is in contact with the external body Phagocytes: extravasion/diapedesis - Imagine the desk as being the capillary layer in the endothelial cells in the tissues of our bodies, but as a the phagocyte you are stuck in that lumen/layer but you can’t just bust through the cell, the phagocytes attach to the lumen (the desk) and just roll along the desk towards an area that has an attractive force towards the other cells (it initiates junctions and enters the tissues of the body) - This process happens because of the chemoattrant damage to the phagocytes (kinda like Starbucks to the customer, the smell that attracts) Some pathogens are tricky, and cannot be recognized as being a foreign entity by the phagocytes Tagging: opsonization Protein to do it: opsonin
The immune system is smarter though so the protein attaches to the pathogens and flags/tags it so that it becomes visible to the phagocyte Figure 24.6 Phagocytosis: Form a phagolysosome NK don’t have specific receptors: like B and T cells Inteferons: interfere with viral replication Acts on endothelial cells lining blood vessels -> loosens junctions b/n cells Compliment proteins are very large group of proteins: there is a sequential, one-after-the-other proteiolysis (activation of the protein) - Membrane Attack Complex (MAC) insert themselves into the membrane of a pathogen and forms a hole so that water and ions (Na, Cl, K) causing the cell to swell until it lysis THE MAC ATTACK
