Ch 3 (Biology and Behavior) Notes

8/13/2019 Ch 3 (Biology and Behavior) Notes

1/12

Ch 3 (Biological Basis of Behavior) Notes

Nervous system

complex communication network in which signals dealing with information are constantly being received,

integrated, and transmitted

Two types of cells in nervous system-

1. Glia (glial cells): cells found throughout the nervous system that provide structural support and insulation

for neurons; hold nervous system together and help maintain the chemical environment of the neurons

2. Neurons: individual cells that receive, integrate, and transmit information; permit communication

Types of neurons

Sensory neurons(afferent neurons): Neurons that travel from body to brain

Motor neurons (efferent neurons): neurons that travel from brain to body (EXIT)

Interneurons: connect sensory and motor neurons located in brain and spinal cord; helps send info quickly (avoids

going all the way to brain from body and back to body)

Mirror neurons: help people take on emotions of the material they are subject to, for example movies and books

and other faces

Neuron features

Information is received at dendrites, passed through soma and along axon, and transmitted to the dendrites of

other cells at synapses.

a. soma: cell body; contains nucleus and much of the chemical machinery common to most cells

b. dendritic trees: branched, featherlike structures; dendrite: part of a neuron specialized to receive

info

c. axon: long, thin fiber that transmits signals away from soma to other neutrons or to muscles/glandsi. may be up to several feet

ii. some do not have, some have multiple

d. myelin sheath: insulating material, derived from glial cells, that encases some axons; 1) speeds up

transmission of signals along axons, 2) keeps neural impulses on the right track

i. multiple sclerosis: loss of muscle control due to degeneration/hardening of myelin sheaths

info moves much more slowly

e. axon terminal: branching structure of knots or bolts that contain terminal buttons at ends

f. terminal buttons (bulbs): small knobs that secrete chemicals

i. neurotransmitters: chemicals that serve as messengers that may activate neighboring

neuronsii. neurotransmitters contained in vesicles

g. synapse: junction where info is transmitted from one neuron to another

i. synaptic cleft: microscopic space between neurons, as neurons DO NOT touch each other

Receptor sites: particular location on the dendrite that serves as a docking harbor for incoming messages


2/12

Neurotransmitters

Chemicals that can cross over to neighboring neurons and activate them; chemicals that transmit information

from one neuron to another

Neurotransmitter + receptor molecule at receptor sites (Step 3 in diagram above) = postsynaptic potential

(PSP): voltage change at receptor site on postsynaptic cell membrane

o NOT all or none, gradedvary in size and increase/decrease probability of neural impulse in receiving

cell in prop to amount voltage change

o two types

1. excitatory PSP: + voltage shift, increases likelihood that postsynaptic neuron will fire action

potentials

2. inhibitory PSP: - voltage shift, decreases

o The state of the neuron (likelihood of action potential being fired) is a weighted balance between

excitatory and inhibitory influences

Antagonists vs. agonists

Agonists: mimic neurotransmitter; bind to receptors and cause PSPs

o Ex: Nicotine is ACh agonist

Antagonist: block/opposes action of neurotransmitters; bind to receptor but fail to produce PSP


3/12

o Ex: Curare is an antagonist for AChparalyzes you

Types of neurotransmitters

Complicationmost aspects of behavior are probably regulated by several types, interactions between various

neurotransmitter systems

Acetylcholine

Acetylcholine (ACh): ALL muscle movement (activates motor neurons controlling voluntary muscles), attention,

arousal, memory

o DeficiencyAlzheimers disease

o venom bites from snakes inject acetylcholine into people, which makes them have muscle spasms

o excess is involved in seizures

Monoamines

Dopamine (DA): voluntarymovement, learning, memory, emotion; produces sensations of pleasure and reward

o ExcessSchizophrenia

o DeficiencyParkinsons

o Amphetamines and cocaine increase release of DA and NE from presynaptic neuronsslowing reuptake

of DA and NE, leaving overabundance of DA and NE in synaptic clefts and causing increased activity Serotonin: sleep, wakefulness, appetite, mood, aggression, impulsivity, sensory perception, aggression in

animals

o Excessbipolar

o Deficiencydepression, OCDs

o LSD, ecstasy block sites for serotonin, which causes crashes after acid trips

Norepinephrine (NE): learning, memory, dreaming, awakening/arousal, emotion/mood, stress-related increase

in heart rate, stress-related slowing of digestive processes

o Works with parasympathetic branch of autonomic nervous system of PNS

o Deficiencydepression

Endorphins

Pain relief, pleasureblock receptor sites for pain

o resemble opiates but are naturally produced endo-morphine

o dependency on pain pillsnatural endorphins become unnecessary, so body gradually stops producing

natural ones

prescription pills esp. strong

GABA

main inhibitoryneurotransmitter in the brain

o imbalancesanxiety, epilepsy

Glutamate

main excitatoryneurotransmitter in the brain involved in learning & memory

o excessmultiple sclerosis

o Release of excessive glutamate apparently causes brain damage after a stroke

Neural impulse: using energy to send info

neural impulse: the signal that moves through the neuron

o Electrochemical processelectrical inside neuron, chemical outside

Resting potential: a neurons stable, negative charge when the cell is inactive


4/12

o Na+, K+, and Cl- ions flow back and forth across cell membrane at different ratesslightly higher

concentration of negatively charged ions inside cell

o about -70 millivolts

WITHIN neuron, communication occurs through action potential: very brief shift in a neurons electrical charge that

travels along axon

o All-or-none response: Either the neuron fires or it does not, no partial/weak firing*

o Steps of action potential

1. Dendrites receive neurotransmitter from another neuron across synapsea. Note: Acquired skills come from repeated use of dendrites in receiving certain information

2. IF threshold is reached, then fires based on all-or-none response

a. signal down axon is sent to open up doors

3. opens up a portal in axon and lets in positive ions (Na+) which mix with negative ions that are

already inside axon

4. mixing of + andions causes an electrical charge that opens up next portal while closing orig

5. process continues down axon to axon terminal

6. terminal buttons turn electrical charge into chemical(neurotransmitter) and shoots message to

next neuron across synapse

Organization of nervous system


5/12

Effervent nerves: axons that carry info outward from CNS to periphery of bodysee sensory neuron

Studying the brainWays we study: accidents, lesions, ESB, EEG, CAT scan, PET scan, MRI, fMRI

Techniques in animal studies

Lesioning studies:

o necessity comes from the limitation of examining how tumors/strokes/head injuries in humans affect their

behavior (extraneous variables make it difficult to isolate causal relationships)o involves purposefully destroying a piece of the brain, usually by inserting an electrode into a brain structure and

passing a high-frequency electric current through it to burn the tissue and disable the structure

o uses stereotaxic instrument to target precise locations

Electric stimulation (ESB)

o involves sending weak electric current into a brain structure along an implanted electrode as an approximation

of normal signals to stimulate/activate it

o like lesioning in that current is delivered through electrode, unlike lesioning in that current stimulates, does not

burn

o

can be used to create brain maps to protect from slicing through crucial areas

o occasionally used on humans when required for medical purposes

Techniques for human brains

Electroencephalographs = EEGs =

o device that monitors electrical activity of brain over time with recording electrodes attached to surface of scalp

o sums and amplifies electric potentials in brain cellsessentially records simultaneous activities of

neurons rather than just individual neuron

o recordings translated into brain wave line tracingsoverview electrical activity

o used in clinical diagnosis of brain damage, neurological disorders, sleep issues


6/12

Brain-imaging equipment

Computerized tomography = (CT or CAT scan)

o computer-enhanced X-ray of brain structure shot from multiple angles to create vivid image of horizontal slice o

brain; 3D x-ray of brain

o least expensive, used widely in research

o good for locating tumors

o STRUCTURE only, tells us nothing about function!

Positron emission tomography (PET) scan =

o introduces radioactively tagged chemicals in brain to mark blood flow or metabolic activity, then monitoring

with X rays, to map actual activity in the brain over time

o measures how much of a chemical the brain is using (usually glucose consumption)

o examine FUNCTION

o help investigate which parts of brain handle what emotion, how drugs affect brain activity

o shows us that even simple mental operations depend on coordination between diff areas

Magnetic resonance imaging (MRI) scan =

o uses magnetic fields, radio waves, and computerized enhancement to give a more detailed map of brain

structure (better than CAT scans)o knocks electrons off axis with magnetic fields

o takes many still pictures and turns them into a movie-like production

o STRUCTURE only, not function

fMRI

o monitor blood/oxygen flow to brain to identify areas of high activity

o combo of PET and MRI

o STRUCTURE AND FUNCTION

The brain and behaviorBrainstem= stem from which the brain flowers

Hindbrain

cerebellum, medulla and pons (medulla and pons located in lower part of brainstem)

Medulla oblongata

o attaches to spinal cord

o unconscious but vital functions including circulation, breathing, maintaining muscle tone, regulating

reflexes such as sneezing, coughing, and salivating, regulating heart beat

Pons

o bridgeof fibers that connects brainstem with cerebellum

o transmits info about body movements

o sleep and arousalsleeping, waking, dreaming

Cerebellum

o large and deeply folded structure located adjacent to the back surface of the brainstem

o coordination of muscle movement, equilibrium (physical balance), fine motor skillsorganizes sensory

information that guides movements


7/12

To make the various segments of your hand and arm deploy smoothly, you need an internal

"clock" that can precisely regulate the sequence and duration of the elementary movements of

each of these segments. That clock is the cerebellum. The cerebellum first receives information

about the intended movement from the sensory and motor cortexes. Then it sends information

back to the motor cortex about the required direction, force, and duration of this movement

o one of the structures first damaged by alcohol

Midbrain

segment of brainstem that lies between hindbrain and forebrain

concerned with sensory processes such as locating where things are in space

contains system of dopamine-releasing neurons that projects into various higher brain centers

o involved in performance of voluntary movements

degeneration of structure in midbraindecline in dopamine synthesisParkinsonism

Reticular formation/reticular activating system

o group of fibers in both hindbrain and midbrain; central core of brainstem (insideof brainstem)

o modulation of muscle reflexes, breathing, pain perception

o regulating sleep/wakefulness and arousal

Forebrain

LARGEST and MOST COMPLEX region of brain; includes thalamus, hypothalamus, limbic system, cerebrum


8/12

Hypothalamus/Thalamus/pituitary gland clarif

Thalamus (part of limbic)

o stationthrough which all sensory info except smellmust pass to get to the cerebral cortex

made up of clusters of somas - each cluster concerned with relaying sensory info to aparticular

part of the cortex that interprets and responds to that info

o integrates info from various sensesactive, not passive

Hypothalamus (part of limbic)

o bundle of nerve fibers found near base of forebrain, below thalamus

o involved in regulation of basic biological needs

control automatic nervous system

vital link between brain and endocrine system

basic biological drives related to survivalfighting, fleeing, feeding (thirst, hunger), mating (sex

drive)

Fight (anger), Flight (survival), Feed (Hunger), F (sexual arousal)

temperature regulation

motivation, emotion

Limbic System

o loosely connected networkof structures located roughly along border between cerebral cortex and

deeper subcortical areas; middle layer of the brain

o controversy over definition, no clear boundaries

o includes parts of thalamus, hypothalamus plus hippocampus, amygdala, septum

Hippocampus

role in memory processes, forming spatial memories or handling consolidation of past and

present memories for factual information

Amygdala

role in emotion, learning fear responses, remembering emotionally charged events,

aggression

o regulation of emotion, memory, motivation

o rich in pleasure centers


9/12

heaviest concentration at medial forebrain bundle(bundle of axons) through hypothalamus

full of dopamine-releasing neurons

but pleasure centers may be neural circuits not anatomical centers

Cerebrum

o LARGEST and MOST COMPLEXpart of human brain

o Learning, remembering, thinking, consciousness

Cerebral cortex

wrinkled, folded outer layer that covers lower brain and controls high-level thought

surface area of 1.5 square feet

two hemispheres (cerebral hemispheres: right and left halves of the cerebrum)

separated by longitudinal fissure that runs from front to back

Corpus callosum:

bundle of nerve fibers that connects 2 cerebral hemispheres

transfers info between two halves

Each cerebral hemisphere has 4 lobes with specific purposes

1. Occipital lobe - vision includes cortical area

o visual cortex: where visual signals are sent and visual processing is begun

interprets messages from our eyes into images we can understand

2. Parietal lobe - touch somatosensory/sensory cortex: area that registers sense of touch that comes from rest of body; INPUT


10/12

o **Left hemisphere section receives input from bodys right side

mostly association areas

functions

o integrating visual input

o monitoring bodys position in space

3. Temporal lobe - hearing auditory cortex: area devoted to auditory processing

NOT lateralized!

Wernickes area: interprets spoken speech, gives ability to comprehend spoken/written language;

located in left temporal lobe

o Wernickes aphasia: when someone is unable to understand language because the syntax and

grammar are jumbled

4. Frontal lobe movement LARGEST lobe in brain

memory, planning, goal-setting, creativity, rational decision making and social judgment, abstract

thought, emotional control, processes memory

contains motor cortex: controls the movement of muscles; OUTPUT

o amount of motor cortex allocated to the control of body part depends on diversity/precision of

its movements, not the parts size, i.e. more of cortex given to parts we have fine control over

such as tongue

o ***Left hemisphere section controls bodys right side

Brocas areaphysical ability to speak (move muscles, jaws, tongue), located in left frontal lobe

Prefrontal cortex/frontal association area

Portion of the frontal lobe to the front of the motor cortex

o disproportionately large28% of cerebral cortex

o high order functionsmemory for temporal sequences, working memory, relational reasoning

o executive control systemmonitor, organize, direct thought processes; prioritize; make

decisions rationally; problem solve

suppresses amygdala

damaged by lobotomies


11/12

Right brain vs. left brain

each hemispheres primary connections are to opp side of body

o visualstimuli in RIGHT half of visual field are registered by receptors on LEFT side of each eye, which

sends signals to the LEFT hemisphere

o auditoryauditory inputs in each ear go to both hemispheres but connections to opposite hemisphere

are stronger and more immediate

fissure: lengthy depression marking off an area of the brain

hemispheres usually in close communication with each other via corpus callosum

Split-brained people

split brain surgery: corpus callosum is cut to reduce severity of epileptic seizures

o studies on split-brained people give insight on specialization of right/left hemispheres

o Roger Sperry, Michael Gazzanigadid studies on split-brained people

Split brain patients are unable to:

o coordinate movements between their major and minor muscle groups

o solve abstract problems involving integrating logical (left hemisphere) and spatial (right hemisphere)

information

o speak about information received exclusively through their left ear, left eye, or left side of their bodies(right hemisphere)

Lateralization

lateralized: how some cognitive functions tend to be dominated by one side or the other

perceptual asymmetries: left-right imbalances between hemispheres in the speed of visual or auditory

processing

LEFT HEMISPHERE DOMINANCE = verbal processing - speech, language (Brocas and Wernickes areas), logic,

writing, math and science, reading

o originally thought of as the dominant hemisphere

o

dysfunction

schizophrenia RIGHT HEMISPHERE DOMINANCE = nonverbal processing - music, athletic, art, dance, perception, creativity,

interpreting spatial relationships and visual images, and recognition of faces

o may play more active role in expressing and recognizing emotions

o more involved in classical conditioning

o dysfunctiondepression

Brain plasticity

The idea that the brain, when damaged, will attempt to find new ways to reroute messages.

Childrens brains are more plastic than adults.

Endocrine system

consists of glands that secrete chemicals into bloodstream to help control bodily functioning

o chemical messengers are hormones: chem substances released by endocrine glands

o some chems are hormones in endocrine system and neurotransmitters in nervous system, for example

norepinephrine

Similar to nervous system, except hormones work a lot slower than neurotransmittersmore long term

hypothalamuscontrols/supervises much of endocrine system


12/12

o Controls the pituitary gland, so has the real power

pituitary gland: master gland that releases hormones that fan out around body to stimulate actions in other

endocrine glandsinfluence secretions of thyroid, pancreas, adrenals, gonads

o Secretes the hormone that regulates growth of muscles, bones, and glands

Gonads: ovaries and testes

thyroid: produces thyroxin, which controls metabolic rateo hypothyroidism: too little thyroxinobesity

o hyperthyroidism: too much thyroxinsudden weight loss

adrenal glands: secretes hormones known as corticosteroids that increase resistance to stress, promote muscle

development, and cause the liver to release stored sugar; control salt and carbohydrate metabolism; secrete

hormones active in arousal and sleep

o fight or flight response by medulla inside

gonads: Testes and ovaries that produce the male and female sex hormones (both genders have all the types of

sex hormones)

o androgens, estrogens, progesterone

Documents

Ch 3 (Biology and Behavior) Notes