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General Psychology
Chapter 3 / PowerPoint Outline
Biological Foundations of Behavior
Neurons: Workhorses / Building Blocks of the NS
 Neurons: individual cells in the NS that receive, integrate and transmit information
o Soma or Cell body: processing center
o Dendrites: receive messages [‘tree’]
o Axon: sends messages
o Myelin sheath: insulates axon
o Nodes of Ranvier: speed up signal
Glial Cells: The ‘Other Stuff’ in the NS
 Provide structure for the NS [Glial = ‘glue’]
 Ratio of glial cells to neurons = 10:1
 Approximately 50% of brain volume
 Nourish neurons, remove waste, insulate, help brain develop prenatally
Action Potential of a Neuron
 Neuron at resting state: slight negative charge (-70 mV) inside of cell
o More negatively charged chloride ions inside cell
o More positively charged sodium and potassium ions outside of cell
 Excitatory neurotransmitters received at dendrite receptor sites
 Causes change in permeability of cell membrane allowing positively charged ions to enter cell
 Voltage in cell goes from negative (-70 mV) to slightly positive (+30 – 40 mV) when neuron fires (1 – 2 milliseconds)
 Cell firing followed by refractory (‘recovery’) period (1 – 2 milliseconds) before returning to resting potential
 Entire action potential process takes an approximate average of 6 – 7 milliseconds
The All-or-None Law
 Neurons either fire at 100% strength or not at all
 Neurons convey differing signal strengths by firing at different rates
 Example:
o Dim lights trigger 5 APs per second
o Bright lights =100 – 200 APs / second
Synaptic Transmission
 Action potential charge reaches axon terminal (tip)
 Synaptic vesicles generate and store neurotransmitters (chemical messengers)
 Vesicles in axon terminal fuse with membrane, burst open releasing neurotransmitters into synapse
 Neurotransmitters cross synapse and potentially bind in matching receptor site on dendrite of neighboring neuron
 Following transmission of message, the synapse may be ‘cleaned up’ by
o Destructive enzymes (MAOs) that clear away excess neurotransmitters
o Taken back into axon terminal through amine pumps in the process of ‘reuptake’
Drug Effects
 Agonist drugs: make transmission easier by mimicking a neurotransmitter, speeding up release, blocking reuptake,
or possibly by sensitizing the receptor site
 Antagonist drugs: make transmission more difficult by slowing transmission, or possibly by desensitizing receptor
site by making the receptor site chemically less sensitive to an incoming neurotransmitter
Neurotransmitters
Norepinephrine
 In the brain causes excitation
 In the body, either excitation or inhibition
 Linked to / created out of dopamine
 Associated with heightened arousal, consciousness and the experience of pleasure
 Low levels associated with depression
o Symptoms of Depression [will not be tested over these symptoms until Test 4 over Chapter 15]
 Sad, depressed mood
 Sleep disturbance
 Appetite disturbance
 Fatigue, loss of energy
 Psychomotor retardation or agitation
 Inability to focus or concentrate
 Excessive guilt or hopelessness
 Thoughts of suicide, suicide plan or attempt
 Loss of interest and pleasure in life
Dopamine
 Found in the brain, inhibitory in nature
 Motivation, reward, pleasure
 Regulation of muscle movement
 Regulation of perception of reality
 Abnormally low levels linked with Parkinson’s disease [also ADHD]
 Abnormally high levels linked with schizophrenia
o Schizophrenia
 Symptoms: delusions, hallucinations, disorganized thought processes, break from reality
 Causes: complete cause is unknown
 Genetics play a notable role (twin studies)
 High levels of dopamine transmission at synapse
 Treatment: anti-psychotic medication
 Anti-psychotic drugs act as a dopamine antagonist by inhibiting receptor sites
Serotonin
 Found in brain & spinal cord, inhibition
 Linked with arousal & consciousness, sleep cycle, appetite, regulation of mood, moderation of aggression
 Unregulated levels associated with mood, eating and anxiety disorders (OCD)
 Low levels associated with depression
o Also eating disorders and OCD
 SSRI drugs used to treat depression block serotonin reuptake [agonist]
Acetylcholine
 In the brain, excitation
 In the body, excitation or inhibition
 Linked with stimulation of muscle movement
o Curare blocks ACh receptors / causes paralysis
[ACh antagonist]
o Botox blocks ACh receptors temporarily paralyzing facial muscles to reduce wrinkling
 In the brain, associated with thinking and memory function
o Nicotine mimics ACh at receptors sites [ACh agonist]
 Abnormally low levels associated with Alzheimer’s disease
o Alzheimer’s Disease
 Most common form of dementia
 Dementia: memory impairment and other problems of language, thinking & movement
 Cause: fairly genetic in origin
 Healthy brain cells degenerate to cellular plaques
 Treatment: Aricept & Cognex act as an agonist for acetylcholine
GABA: Gamma Amino Butyric Acid
 Found widely through brain / NS [40%]
 Found in brain, spinal cord, inhibition
 Serves to help control uncontrolled muscle movement
 Abnormally low levels associated with Huntington’s Disease
 Anti-anxiety drugs like Valium work as an agonist for GABA causing a slowing of neural function
Divisions of the Nervous System
The Brain
Methods of Brain Study
 EEG
 Lesioning
 Electrical Stimulation
 Transcranial Magnetic Stimulation
 Imaging
o CT, PET, MRI, fMRI
Brain Overview [1]
Medulla:
-Blood circulation
-Breathing
-Muscle tone
-Reflexes
Cerebellum:
-Coordinates movement
-Balance
-Posture
-Thought organization
-Damage = fine motor
-1st part depressed by ETOH
Pons:
-L/R coordination
-Sleep
-Bladder
Brain Overview [2]
Amygdala / Hippocampus / Hypothalamus
Amygdala:
• Major emotion center,
especially fear from threat
• Plays a role in memory,
decision making
Hippocampus:
• Primary memory processing
center
Hypothalamus:
 Motivation [food, water, sex]
 Emotion [pleasure, anger/rage]
 Sleep cycle, blood pressure
Pleasure Center Self-Stimulation of a Rat
Video: https://youtu.be/aNXhyPj-RsM
Comparing Animal and Human Brains
Lobes of the Cerebrum
Mirror Neurons [Giacomo Rizzolatti]:
• Neurons activated by performing
an action or by observing
someone perform an action
• Thought to play a role in mimicry
and empathy
• Mirror neuron deficits are
implicated in autism
Left Brain – Right Brain Functions
Left-Right Hemispheric Variation
Functions generally based in left / right brain anatomy:
Left:
 Analytical functions
 Math
 Language / Grammar
 Time
Right:
 Artistic
 Visual
 Spatial
 Creative
Split Brain Research [Roger Sperry / Michael Gazzaniga]
 Rarely performed treatment for severe, uncontrolled epilepsy
 Corpus callosum is severed separating left / right hemispheres
 L-R hemispheres no longer communicate directly
 Yet, sensory-motor functions are still linked to L-R sides of body
Left-Right Brain Conclusions
 Measured L-R brain difference do exist
 For most, the two sides are well integrated
 Many researchers contend L-R brain differences are overblown
 No evidence to support claim that some are ‘left’ or ‘right-brained’
 fMRI studies show no distinct L-R differences in brain activity between L-R brain styles
 Yet, L-R cognitive styles do exist