AP Psychology Chapter Two Neuroscience and Behavior
I.
Neural Communication: Biological Psychologists study the Iinks between biological activity and psychological events. A.
Neurons: Are nerve cells that each consist of a cell body, dendrites, and axons (away). 1.
Dendrites receive info.
2.
Axons pass info. Along Along to other neurons.
3.
Fatty tissue known as myelin sheath insulates the axons of some neurons speeding up transmission. 4.
As seen in multiple sclerosis patients, if the myelin sheath begins to break down, communication to muscles begins to slow and will eventually lead to loss of muscle control.
5.
Speeds can range from 2-200 miles per hour.
B.
Neural Transmission: A neuron fires an impulse when it receives signals from sense receptors stimulated by pressure, heat, or light, or when it is stimulated by chemical messages from adjacent neurons. 1.
This impulse is known as an action potential (electrical charge).
2.
Neurons, like batteries, generate electricity from chemical events.
3.
Electrically charged atoms atoms called ions are exchanged in this chemistry to electricity process.
4.
Fluid inside resting axon is mostly negatively charged while fluid outside axon membrane is mostly positively charged.
5.
This separation of neg./pos. (known as resting potential) occurs b/c an unmyelinated axon's membrane is selectively permeable.
6.
In other words, the pos. ions can't get through.
7.
However, when the neuron fires, the first bit of the axon opens its gates allowing pos. ions to flood in causing depolarization.
8.
Depolarization causes the next axon channel to open and so on ... (dominoes).
9.
During a resting phase, the pos. ions are pumped back outside.
1 O.Then the neuron can fire again. 11 .If myelinated, the action potential speeds up. C. Excitatory and Inhibitory signals: Neurons make decisions based on the signals they receive. Most neurons have a resting rate of random firing that either increased or decreases w/input from other neurons. 1.
Excitatory signals accelerate neurons.
2.
Inhibitory signals slow neurons down.
3.If
excitatory signals - inhibitory signals exceed a minimum
intensity, called the threshold, the combined signals trigger an impulse. 4. Increasing the stimulus above the threshold DOES NOT increase the impulse's intensity or speed. 1. Ex. Like guns, neurons either fire or they don't and squeezing the trigger harder won't make the bullet go faster. 2. A strong stimulus CAN trigger more neurons to fire and to fire more often. D. How Neurons Communicate: Neurons are separated by a very small junction known as a synapse. We refer to this as a synaptic gap or cleft. 1. When the action potential reaches the knoblike terminals at an axon's end, it triggers the release of chemical messengers known as neurotransmitters.
2. These fill the gap and allow for the "kiss" to take place OR ions to enter the receiving neuron either exciting or inhibiting its readiness to fire. 3. Excess neurotransmitters are reabsorbed by the sending neuron in a process known as reuptake. 4. Many drugs increase the availability of selected neurotransmitters by blocking their reuptake. 1. Ex.
E. How Neurotransmitters influence us: motions and emotions. 1. Dopamine: Influences movement, learning, attention, and emotion. Excess dopamine has been linked w /schizophrenia. 2. Serotonin: Affects mood, hunger, sleep, and arousal. Prozac and other antidepressants raise serotonin levels. 3.
Nor epinephrine: helps control alertness and arousal.
4.GABA
(gamma-amino butyric acid) serves inhibitory
functions and is sometimes implicated in eating disorders and sleep disorders. 5. Acetylcholine: Works on 'neurons involved in muscle, action, learning, and memory. Alzheimer's patients experience a deterioration of those neurons that produce this critical chemical messenger. F. Acetylcholine: More info. 1. ACh is the messenger at every junction between a motor neuron and skeletal muscle. 2.
When released to our muscle cells, the muscle contracts.
3.
If transmission is blocked, our muscles cannot contract. 4.
Ex. Curare-hunting darts-paralysis.
5.
Ex. Botulin-paralysis.
3. Ex. Black widow's poison-not blocked but allowed to flood causing violent muscle contractions, convulsions, and possible death. G. The Endorphins: Neurotransmitters similar to morphine that re produced in the brain and elevates mood and eases pain.
1. These natural opiates are released in response to pain and vigorous exercise. Ex. "runner's high". H. How Drugs and Other Chemicals Alter Neurotransmission: 1. When flooded w / opiate drugs such as heroin and morphine the brain may stop producing its own natural opiates. When this drug is withdrawn, the brain is deprived of any form of opiate, which is not pleasant for the drug addict. 2. Drugs affect communication at the synapse often by exciting or inhibiting neuron firing. 1. Agonists excite by mimicking a particular neurotransmitter or by blocking its reuptake. 2. Antagonists inhibit by blocking neurotransmitters or by diminishing their release. 3. New therapeutic drugs are being created to address neurotransmitter related problems. 4. The brain-blood barrier makes creating drugs harder than you'd think b/c the brain can block out chemicals in the blood. 1. Ex. Parkinson's patients can not take a drug that mimics dopamine b/c it is blocked by the brain and can't slither through the barrier. 2. However, if given the raw material L-dopa, which can sneak through, the brain can convert this to dopamine and as a result decrease the deficit.
II.
The Nervous System: Our body's primary info. system. A. The (CNS) is made up of the brain and spinal cord while the (PNS) links the CNS w/ the body's sense receptors, muscles, and glands. B. Info. travels in the nervous system via 3 types of neurons: 1. Sensory neurons carry INCOMING info. from the sense receptors to the CNS. 2. Interneurons are CNS neurons that internally communicate and intervene between the sensory inputs and motor outputs.
III.
IV.
v.
3. Motor neurons carry OUTGOING info. from the CNS to the muscles and glands. C. Our nerves serve as electrical cables by bundling the sensory and motor axons carrying PNS info. 1. Ex. Optic nerve: billions of axons in a single cable carrying info. from eye to brain. The Peripheral Nervous System: Consist of two components: Skeletal/somatic and Autonomic A. The somatic controls voluntary movements of skeletal muscles. B. . The Autonomic controls the gland and muscles of our internal organs 1. Usually operates on its own to influence internal functioning. 2. But, can be consciously overridden sometimes. 3. This is a dual sys. that usually work together to maintain a steady internal state. 4. If needed, the sympathetic ns sys. arouses us for defensive action. 5. When the stress subsides, the parasympathetic ns produces opposite effects to calm us down. The Central Nervous System: Our spinal cord and brain allow neurons to talk to other neurons which enable our humanity-our thinking, feeling, and acting. A. Spinal cord: an information highway connecting the PNS to the brain. 1. Ascending neural tracts send up sensory info. and descending tracts send back motor-control info. 2. Our reflexes are automatic and our body reacts before our brain receives info. to feel pain b/c of interneurons. 3. However, to produce bodily pain or pleasure, the info. must reach the brain. B. The Brain: receives info., interprets it, and decides responses. 1. Our neural networks strengthen connections between neurons b/c certain patterns of input will produce a given output. The Brain A. Tools of discovery: we've come a long way baby! 1. Lesion production allows us to observe the effects of brain diseases and injuries. (can be produced surgically in animals) 2. Why wait for an injury when you can, electrically, chemically, and magnetically stimulate parts of the brain and note the effects. 3. EEG is an amplified recording of the electrical activity that sweeps across the brain's surface. 4. Neuroimaging techniques allow us to see inside the brain w/o lesioning it.
1. CT scan: x-ray photos that can reveal brain damage. 2. PET scan: sugar glucose is injected into patient and where this sugar concentrates tells us which parts of the brain are active during a given task. 3. MRI: head is put into strong magnetic field, which aligns spinning atoms. Brief radio waves disorient atoms and when they return to their normal spin signals are detected. These signal concentrations can be seen. Ex. schizophrenia. 4. Functional MRI: brain lights up when participant is asked to perform different mental functions. VI. Low-level Brain Structures: functions w/o any conscious effort and sustains basic life functions as well as enables memory, emotions, and basic drives. A. The Brainstem (basement/custodians): begins where the spinal cord enters the skull and swells slightly forming the medulla. B. The medulla is responsible for heartbeat and breathing/automatic survival functions. C. The reticular formation runs the brain stem passing through the medulla and up to the thalamus. It controls arousal. D. The thalamus is the brain's switchboard for all sensory info. except smell. It receives info. from the senses and routes it to various higher brain regions. E. The cerebellum (little brain) most obvious function is coordinating voluntary movement. F. The limbic system is located at the border of the lower brain's part and the cerebral hemispheres and plays a part in emotions and basic drives. 1. The hippocampus is the only part of this system that processes memory; 2. The amygdala influence aggression and fear. Must remember however, that this is not the only part of the brain involved in such emotions. 3. The hypothalamus helps keep the body's internal environment in a steady state by regulating thirst, hunger, and body temperature. Sexual behavior is also influenced much like a reward system (built in). Reward deficiency syndrome has been proposed for addictive behaviors such as alcoholism, drug abuse, and food binging.
VII. The Cerebral Cortex: like bark on a tree it is the thin outer covering of our brain and is our body's ultimate control and info. processing center. A. Structure of the cortex: thin surface of the cerebral hemispheres (left/right). B. Each hemisphere is divided into 4 lobes. Each lobe carries out many functions and some of these functions require the interplay of several lobes. 1. Frontal lobes: just behind forehead. Speaking, muscle movements, and speaking. Motor strip lies at the rear. 2. Parietal lobes: top of head and toward rear. Includes the sensory cortex. 3. Occipital lobes: back of head. Visual cortex receives info. from opposite visual field. 4. Temporal lobes: above ears. Auditory cortex receives auditory info. primarily from the opposite ear. C. Functions of the cortex: Motor functions, sensory functions, and association functions. *Beware! Complex activities involve many brain areas. 1. The motor cortex sends messages out to the body and can be stimulated to make different body parts move(simple) . . ~ Opposite body parts move from the side stimulated. 2. Those areas that require precise control, occupied the greatest amount of cortical space. Ex. fingers and mouth. 3. *Functional MRIs show, however, that most movements require more than one part of the brain: D. The sensory cortex: receives incoming messages. 1. The more sensitive a body region the greater the area of the sensory cortex devoted to it. Ex. lips, foes 2. If you lose a finger that region of the sensory cortex receives info. from your other fingers making them more sensitive. 3. Nurture is also involved. "WELL PRACTICED" pianist have larger than usual auditory cortex area that encodes piano sounds. 4. The visual cortex part of your occipital lobes processes visual info. E. The other 3/4s of our brain not committed to sensory or muscular activity is referred to as our association areas. 1. No part of our brain is not used. .
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2. For ex. the associations areas in our frontal lobes allow us to plan, judge, and process new memories. 3. Electronically probing these areas produces no observable responses. 4. Frontal lobe damage can also affect personality. Ex. Phineas Gage. 5. Assoc. areas of the parietal lobe are involved in math and spatial reasoning. 6. An area on the underside of the right temporal lobe enables us to recog. faces. If damaged, couldn't recog. your own mom. F. Language requires the use of many brain areas. 1. For ex. damage to any of several cortical areas can cause an •• impaired use of language known as aphasia. 2. Left 'frontal lobe: Broca's area (Tom Brokaw): disrupts speaking. 3. Left temporal lobe: Wernicke's area: disrupts understanding. 4. Angular gyrus: could speak and understand but not read. G. In summary, the brain's specific subsystems are localized in particular regions, yet the brain acts as a unified whole. Brain Reorganization: .Nurture reveals the plasticity of the brain. A. Even though severed neurons are not likely to regenerate, neural tissue can reorganize in response to damage. 1. Ex. Monkeys arm severed-sensory area shifted to face. 2. Ex. cat's eye-laser damages spot in eye-other areas of the eye gain sensory area. 3. Ex. Blind people have greater area of sensory cortex devoted to touch. B. New evidence reveals that adult humans can generate new brain cells. ., ~ 1. Brains way to compensate for gradual loss of neurons. 2. Master "stem cells" that can dev. into any type of brain cell could be used in a diseased brain. (?) 3. The younger our brains the more plastic. 4. Ex. Hemispherectomies. Our Divided Brains: Two hemispheres serve different functions. A. Left hemisphere: reading, writing, speaking, arithmetic reasoning, and understanding. B. Right hemisphere: understands simple requests and easily perceives objects.
C. Split brain patients (cut the corpus callosum) show hemispheric differences. D. Our Intact brain hemispheric differences: E. Right hemisphere: perceptual tasks. 1. Ex. recog. picture faster and more accurately B. Left hemisphere: speaks or calculates. 1. Ex. recog. work faster and more accurately 2. Ex. Zulu lang. heard clicks in right ear and more accurately recog. 3. Ex. Sign lang. is processed in left hem. XI. Handedness: Is it inherited? A. Genes or some prenatal factor influences handedness. 1. Ex. newborn study 2. Poor Kelsea! XII. The Endocrine System: Hormones released by endocrine glands forms the body's slower information system. (pg.81 diagram) A. Glands secrete other forms of chemical messengers known as hormones. 1. These chemicals travel via the bloodstream. 2. They influence our interest in sex, food, and aggression. 3. This system takes longer but the effects usually last longer than the effects of a neural message. B. Your adrenal glands release epinephrine and norepinephrine which increase heart rate, blood pressure, and blood sugar, providing us with a surge of energy. 1. When the emergency passes, the hormones and their effects linger for a while. C. The pituitary gland (master gland) is controlled by the hypothalamus AND is also a controller in its own right. 1. Releases the growth hormone. 2. Signals sex hormones to release sex hormones. D. The nervous and endocrine systems are so interconnected the distinction between them sometimes blurs.
