Chapter 8 Lecture Slides
Chapter 8-Nervous System
Functions 1. Sensory input:
sensory receptors respond to stimuli 2. Integration:
brain and spinal cord process stimuli 3. Control of muscles and glands 4. Mental activity:
brain 5. Homeostasis
Main Divisions of Nervous System 1. Central Nervous System (CNS):
brain and spinal cord
2. Peripheral Nervous System (PNS):
all neurons outside CNS
Neuron Characteristics • Nerve cells • Require oxygen and glucose • Receive input, process input, produce a response
Neuron Structures • Dendrite: receives stimulus from other neurons or sensory receptors • Cell body: - processes stimulus - contains a nucleus • Axon: transmits stimulus to a gland, muscle, organ, or other neuron
Myelin Sheath • What is it? - fatt fatty, y, prot protec ecti tive ve wrapp wrappin ing g aro around und axons axons - excel xcelllent insula ulator • Nodes of Ranvier: gaps in myelin sheath where action potentials develop • Saltatory conduction:
• Myelinated axons conduct action potentials more quickly (3-15 meters/sec) than unmyelinated due to Nodes of Ranvier. • Multiple sclerosis: disease of myelin sheath that causes loss of muscle function
Types of Neurons • Multipolar: - many dendrites and a single axon
- Ex. Ex. CNS CNS and and most most moto motorr neur neuron onss • Bipolar: - one one den dendr drit itee and and one one axon axon - Ex. Ex. Eye Eye and and nasa nasall cavi cavity ty • Pseudo-unipolar: - one axon and no dendrites
Neuroglia Characteristics • Supporting cells for neurons • More numerous than neurons • Can divide to produce more cells • 5 types
Types of Neuroglia
• Astrocytes: - star-shaped - most abun bundant - form form bloo bloodd-br brai ain n barr barrie ier r • Ependymal Cells:
Types of Neuroglia
• Microglia: help remove bacteria and cell debris from CNS
• Oligodendrocytes: produce myelin sheath in CNS
Types of Neuroglia • Schwann cells: produce myelin myelin sheath in PNS
Organization of Nervous Tissue • Gray matter: collection of dendrites and cell bodies • White matter: collection of axons and their myelin sheath
CNS
PNS
Oligodendrocytes
Schwann cells
Produce myelin sheath Nerve tracts
Nerves
Collection of axons Nuclei
Ganglion
Collection of cell bodies
Electrical Signals and Neural Pathways Resting Membrane Potential
• Outside of cell is more + (Na+) • Inside of cell is more – more – (K (K +) • Leak ion channels: - always open - K + channels
• Gated ion channels: - close closed d unti untill open opened ed by speci specifi ficc sig signal nal
Action Potentials • “Electricit “Electricity” y” that that cause cause depolarizati depolarization on and repolarization • Change resting membrane potential by activating gated ion channels • Local Current: movement of Na+ which causes inside of cell to be more positive (depolarize)
• If enough Na+ enters then threshold is reached and more Na+ chann hannel elss open pen • Once threshold is reached all or none law applies • Action potentials continue until Na+ channels close, K + channe channels ls open, open, and repolarization occurs • Sodium/potassium pump restores
Synapse • What is it? - where an axon attaches to a muscle, gland,
organ, or other neuron - invol involved ved with with rele release ase of of neuro neurotr trans ansmi mitt tter erss - Ex. Ex. Neur Neurom omus uscu cula larr junc juncti tion on
Figure 8.13
Reflexes • What are they? involuntary response to a stimulus • Reflex arc: path reflex travels
Components of Reflex Arc 1. Sensory receptors:
- pick up stimulus - in skin 2. Sensory (afferent) neurons:
send stimulus to interneurons in spinal cord 3. Interneurons (Association) neuron:
- locat located ed in CNS CNS and connec connectt to to moto motorr neur neurons ons ti
l
4. Efferent (motor) neurons:
send response to effector 5. Effector:
muscle, gland, or organ
Figure 8.14
Neuronal Pathways • Converging: - two two or more more neur neurons ons synaps synapsee same same neuron neuron - allows info. to be transmitted in more than one
neuronal pathway to converge into a single pathway • Diverging: - axon axon from from one one neur neuron on divi divides des and synaps synapses es wit with h more than one neuron - allow allowss info. info. to be be tran transmi smitt tted ed in in one neuron neuronal al
Central Nervous System Consists of brain and spinal cord Brain in brain case:
Spinal cord in vertebral column:
Spinal Cord • Extends from foramen magnum to 2 nd lumbar vertebra • Protected by vertebral column • Spinal nerves allow movement • If damaged paralysis can occur
Gray Gray and and White White Matter Matter in in Spinal Spinal Cord • Gray Matter: - cent enter of of sp spinal nal cor cord d - look lookss lik likee let lette terr H or or a but butte terf rfly ly • White Matter: - outs outsid idee of of spi spina nall cor cord d - conta contain inss myeli myelinat nated ed fiber fiberss
White Matter in Spinal Cord • Contains 3 columns dorsal, ventral, lateral columns • Ascending tracts: axons that conduct action potentials toward brain • Descending tracts: axons that conduct action potentials away from
Gray Matter in Spinal Cord • Posterior horns: contain axons which synapse with interneurons • Anterior horns: contain somatic neurons • Lateral horns: contain autonomic neurons • Central canal: fluid filled space in center of cord
Spinal Nerves • Arise along spinal cord from union of dorsal roots and ventral roots • Contain axons sensory and somatic neurons • Located between vertebra • Categorized by region of vertebral column from which it emerges (C for cervical) • 31 pairs • Organized in 3 plexuses
Cervical Plexus • Spinal nerves C1-4 • Innervates muscles attached to hyoid bone and neck • Contains phrenic nerve which innervates diaphragm
Brachial Plexus • Originates from spinal nerves C5-T1 • Supply nerves to upper limb, shoulder, hand
Lumbosacral Plexus • Originates from spinal nerves L1 to S4 • Supply nerves lower limbs
Cerebrospinal Fluid • Fluid that bathes the brain and spinal cord • Provides a protective cushion around the CNS • Produced in choroid plexus of brain
Brainstem
• Components: – Medulla oblongata – Pons – Midbrain
Brainstem Components • Medulla oblongata – Location: – Location: continuous with spinal cord – Function: – Function: regulates heart rate, blood vessel diameter, diameter, breathing, swallowing, vomiting, hiccupping, coughing, sneezing, balance – Other – Other : pyramids: involved in conscious control of skeletal s keletal muscle
• Pons – Location: – Location: above medulla, bridge between cerebrum and cerebellum – Function – Function:: breathing, chewing, chewing, salivation, swallowing swallowing • Midbrain – Location: – Location: above pons – Function: – Function: coordinated eye movement, pupil diameter, turning head toward noise
• Reticular Formation - Location: scattered throughout brainstem - Function: regulates cyclical motor function, respiration, walking, chewing, arousing and maintaining consciousness, regulates sleep-wake cycle
Diencephalon
• Located between the brainstem and cerebrum • Components: -Thalamus
Diencephalon Components • Thalamus - Ch Char arac actter eriist stiics cs:: largest portion of diencephalon - Function: influences moods and detects pain •
Epithalamus: - Location: above thalamus - Function:
• Hypothalamus - Location: below thalamus - Characteristics: controls pituitary gland and is connected to it by infundibulum - Function: controls homeostasis, body temp, thirst, hunger, fear, rage, sexual emotions
Figure 8.24
Cerebrum Characteristics • Largest portion of brain • Divisions: – Right Hemisphere – Left Hemisphere
separated by longitudinal fissure
• Lobes: frontal, parietal, occipital, temporal
Cerebrum Components Cerebr bral al Cort Cortex ex • Cere - Location:
surface of cerebrum, composed of gray matter - Function: controls thinking, communicating, remembering, understanding, and initiates involuntary movements
• Gyri: folds on cerebral cortex that increase surface area • Sulci: shallow indentations • Fissure: deep indentations
• Left hemisphere: - cont contro rols ls righ rightt sid sidee of body body - respon responsib sible le for for mat math, h, analy analyti tic, c, and and spee speech ch • Right hemisphere: - controls left side of body - respo responsi nsibl blee for for musi music, c, art art,, abst abstra ract ct ide ideas as • Corpus callosum: connection between 2 hemispheres
Lobes of Brain • Frontal lobe - Location: front - Function: controls voluntary motor functions, aggression, moods, smell • Parietal lobe - Location: top - Function: evaluates sensory input such as touch, pain, pressure, temp., taste
• Occipital lobe - Location: Location: back back
- Function: vision • Temporal lobe - Location: sides
- Function: hearing, smell, memory
Cerebellum • Location: below cerebrum • Characteristics: - means eans littl ittlee brai brain n - cort cortex ex is compo ompose sed d of of gyri, sulci, gray matter • Functions: controls balance, muscle tone, coordination of fine
Sensory Functions • CNS constantly receives sensory input • We are unaware of most sensory input • Sensory input is vital of our survival and normal functions
Ascending Tracts • What are they? - path pathwa ways ys in brai brain n and and spi spina nall cor cord d - transmit info. via action potentials from
periphery to brain - each tract has limited type of sensory input
(temp, touch, pain, etc.) - trac tracts ts are are nam named ed that that indi indicat cated ed ori origi gin n and and termination
Sensory Areas of Cerebral Cortex • Primary sensory areas: - wher wheree asc ascen endi ding ng trac tracts ts proj projec ectt - where sensations are perceived
• Primary somatic sensory cortex: - gener eneraal se sensor nsory y ar area - in pa parietal lobe - senso sensory ry inpu inputt such such as as pain pain,, press pressure ure,, temp temp..
Motor Areas of Cerebral Cortex • Primary motor cortex: - frontal lobe - cont contro roll vol volun unta tary ry moto motorr move moveme ment nt • Premotor area: - frontal lobe - where motor functions are organized before
initiation • Prefrontal area: motivation and foresight to plan and initiate
Descending Tracts • Project from upper motor neurons in cerebral cortex to lower motor neurons in spinal cord and brainstem • Control different types of movements
Basal Nuclei • Group of functionally related nuclei • Plan, organize, coordinate motor movements and posture • Corpus striatum: deep in cerebrum • Substantia nigra: in midbrain
Speech • Mainly in left hemisphere • Sensory speech (Wernicke’s area): - parietal lobe - where words are heard and comprehended
• Motor speech (Bronca’s area): - frontal lobe
Brain Waves and Consciousness • Used to diagnose and determine treatment ofr brain disorders • Electroencephalogram (EEG): electrodes plated on scalp to record brain’s electrical activity • Alpha waves: person is awake in quiet state
• Beta waves: intense mental activity • Delta waves: deep sleep • Theta waves: in children
Memory • Encoding: - brief retention of sensory input received by
brain while something is scanned, evaluated, and acted up - also also cal calle led d sens sensor ory y mem memor ory y - in temporal lobe - last lastss les lesss tha than n a sec secon ond d
• Consolidated: - data data that that has has bee been n enc encod oded ed - temporal lobe - short term memory
• Storage: - long term memory - few minute minutess or permanen permanently tly (depends (depends on on
retrieval) • Retrieval: how often info. is used
Types of Memory • Short-term memory: - info. info. is is reta retain ined ed for a few few seco seconds nds or min. min. - bit bits of of inf info. o. (usua usuall lly y 7) 7) • Long-term memory: can last for a few minutes or permanently • Episodic memory: places or events • Learning:
Meninges • What are they? protective wrapping around brain and spinal spina l cord • Meningitis: infection of meninges (bacterial or viral)
Types of Meninges •
Dura Mater: - superficial
- thickest layer •
Arachnoid mater:
2nd layer •
Pia mater:
- 3rd layer - surface of br brain •
Subarachnoid space:
• Epidural space: - in vert verteb ebra rall col colum umn n betw betwee een n dur duraa and and vert verteb ebra ra - inje inject ctio ion n site site for for epidur epidural al anest anesthe hesi siaa • Spinal block and spinal tap: - in suba subara rachn chnoi oid d space space wher wheree cere cerebr brosp ospin inal al fluid can be removed or anesthetic inject - numbs umbs spin pinal ner nerves ves
Ventricles • What are they? cavities in CNS that contain fluid • Fourth ventricle: - base of of ce cerebellum - conti continuo nuous us with with cent centra rall canal canal of spin spinal al cord cord
Cranial Nerves • 12 pair of cranial nerves • Named by roman numerals • 2 categories of functions: sensory and motor
Peripheral Nervous System • Consists of all neurons outside brain and spinal cord • Collects input from different sources, relays input to CNS, and performs action
Divisions of Peripheral Nervous System 1. Afferent (Sensory):
collects input from periphery and sends it to CNS 2. Efferent (Motor):
carries processed input from CNS to effector
Divisions of Efferent (Motor) 1. Autonomic:
- respo response nse is autom automati aticc (invo (involu lunt ntar ary) y) - contr control olss smoot smooth h and cardi cardiac ac mus muscl cles es and and gland glandss 2. Somatic:
- resp respon onse se is volu volunt ntar ary y - cont contro rols ls skel skelet etal al musc muscle less
Divisions of Autonomic 1. Sympathetic: – activated – activated during times of stress – part part of fight or flight response – prepares prepares you for physical activity activity by:
- ↑ HR - ↑ BP - ↑ BR - sendin sending g more more blood blood to skele skeleta tall musc muscle less inhi inhibi biti ting ng dige digest stiv ivee trac tractt
2. Parasympathetic: – “housekeeper” – activated – activated under normal conditions – involved – involved in digestion, urine production, and dilation/constriction of pupils, etc.
