Download UNIT 3A: Biological Bases of Behavior – Neural Processing and the

UNIT 3A: Biological Bases of Behavior – Neural Processing and the Endocrine System
I.
II.
Overview
A.
Everything psychological is simultaneously biological
B.
Early history
1.
Plato located the mind in the spherical head
2.
Aristotle believed the mind was in the heart
3.
Scientists have since concluded that it is the brain that feels, not the heart
4.
Phrenology
a.
Invented by German physician Franz Gall
b.
Incorrect theory that claimed bumps on the skull could reveal mental abilities as well
as character traits
c.
Correctly focused attention on the fact that various parts of the brain have different
functions
C.
Biological psychology
1.
Link biological activity and psychological events
a.
Sleep and dreams
b.
Disease and stress
2.
We are biopsychosocial systems
a.
Cells form organs; organs form systems; systems for the individual
b.
Individual is part of a family, culture, and community
Neural Communication
A.
Information systems of animals function similarly to those of humans. Hence, a scientist can study an
animal and get the gist of a human’s comparable function.
B.
What are neurons, and how do they transmit information?
1.
Neurons – nerve cells; building blocks
2.
Sensory neurons
a.
Carry messages from the body’s tissues and sensory organs
inward to the brain and spinal cord
b.
Millions of these
3.
Motor neurons
a.
Carry messages from the brain and spinal cord to the body’s
tissues
b.
Millions of these
4.
Interneurons
a.
Brain’s internal communications system where information is processed
b.
Billions of these
c.
Dendrite
i.
Receive information and conduct it toward the cell body
ii.
They “listen”
iii.
Short
d.
Axon
i.
Passes the message along to other neurons or to muscles or glands
ii.
They “speak”; axons away!
iii.
Long – projecting several feet throughout the body
e.
Myelin sheath
i.
Insulates the axons of some neurons and helps speed impulses
ii.
Stops being created at about age 25 (growth of neural efficiency, judgment,
and self-control)
iii.
Degeneration of the myelin sheath results in multiple sclerosis
(communication to muscles slows with eventual loss of muscle control)
f.
Speed of neural impulse
i.
2 miles per hour to 200 or more miles per hour
ii.
iii.
5.
C.
D.
3 million times slower than that of electricity through a wire
Brain activity is measured in milliseconds (thousandths of a second) v.
computer activity in nanoseconds (billionths of a second)
Process
a.
Neurons transmit messages when stimulated by signals from our sense when
triggered by chemical signals from neighboring neurons
b.
Neuron fires an impulse (action potential) which is a brief electrical charge that
travels down its axon
c.
At the cell body end of an axon, neuron stimulation causes a brief change in
electrical charge
i.
Fluid interior of a resting axon has an excess of negatively charged ions
ii.
Fluid outside of the axon membrane has more positively charged ions
iii.
Negative interior and positive exterior is called resting potential
d.
Neuron fires
i.
First bit of the axon opens its gates
ii.
Positively charged sodium ions flood through the membrane
iii.
This depolarizes that section of the axon
iv.
The axon’s next channel opens, and then, the next
v.
During a resting pause (the refractory period), the neuron pumps the
positively charged sodium ions back outside
vi.
Neuron can then fire again (100 – 1000 times a second)
e.
Neuron as decision maker
i.
Most signals are excitatory (somewhat like pushing a neuron’s accelerator)
ii.
Other signals are inhibitory (more like pushing a brake)
iii.
If excitatory minus inhibitory exceed threshold (minimum intensity), the
combined signals trigger action potential
iv.
Neuron’s reaction is all or nothing (ie. pulling a trigger of a gun)
How do nerve cells communicate with other nerve cells?
1.
Meeting point between neurons is called a synapse
2.
Axon terminal of one neuron is separated from the receiving neuron by a synaptic gap/cleft
(less than a millionth of an inch wide)
3.
Process
a.
Action potential reaches the knoblike terminals at an axon’s end
b.
Triggers release of chemical messengers – neurotransmitters
c.
Within 1/10,000th of a second, the neurotransmitter molecules cross the synaptic gap
and bind to receptor sites on the receiving neuron
d.
The neurotransmitter unlocks tiny channels at the receiving site
e.
Electrically charged atoms flow in, exciting or inhibiting the receiving neuron’s
readiness to fire
f.
The sending neuron reabsorbs the excess neurotransmitter in a process called
reuptake
How do neurotransmitters influence behavior, and how do drugs and other chemicals affect
neurotransmission?
1.
Neurotransmitters influence our motions and emotions
a.
Acetylcholine (ACh) is one of the best-understood neurotransmitters
i.
Has a role in learning and memory
ii.
Messenger at every junction between a motor neuron and skeletal muscle
iii.
When ACh is released to our muscle cell receptors, the muscle contracts
iv.
If ACh transmission is blocked (like during anesthesia), the muscles cannot
contract; we are paralyzed
2.
Some neurotransmitters and their functions
a.
Acetylcholine (ACh)
i.
Enables muscle action, learning, and memory
III.
ii.
With Alzheimer’s disease, ACh-producing neurons deteriorate
b.
Dopamine
i.
Influences movement, learning, attention, and emotion
ii.
Excess dopamine receptor activity is linked to schizophrenia. Starved of
dopamine, the brain produces the tremors and decreased mobility of
Parkinson’s disease
c.
Serotonin
i.
Affects mood, hunger, sleep, and arousal
ii.
Undersupply linked to depression. Prozac and some other antidepressant
drugs raise serotonin levels
d.
Norepinephrine
i.
Helps control alertness and arousal
ii.
Undersupply can depress mood
e.
GABA (gamma-aminobutyric acid)
i.
Major inhibitory neurotransmitter
ii.
Undersupply linked to seizures, tremors, and insomnia
f.
Glutamate
i.
Major excitatory neurotransmitter; involved in memory
ii.
Oversupply can over-stimulate brain, producing migraines or seizures
(which is why some people avoid MSG, monosodium glutamate, in food)
E.
How do drugs and other chemicals alter neurotransmission?
1.
If endorphins make a person feel good, why not give the body artificial opiates such as heroin
and morphine?
a.
When flooded with opiates, the body stops producing its own
b.
Thus, a person who stops taking the artificial opiates will suffer from withdrawal
2.
Drugs and other chemicals affect brain chemistry at synapses, often by either amplifying or
blocking a neurotransmitter’s activity
a.
Agonists are molecules that are similar enough to a neurotransmitter to bind to its
receptor and mimic its effects
i.
Some opiate drugs are agonists and produce a temporary “high” by
amplifying normal sensations of arousal or pleasure
ii.
Black widow spider venom floods synapses with ACh. This results in
violent muscle contractions, convulsions, and possible death
b.
Antagonists also bind to receptors but the result is to block a neurotransmitter’s
function
i.
Botulin, a poison that can form in improperly canned food, causes paralysis
by blocking ACh release. Botox (small injections of botulin) smooth
wrinkles by paralyzing the underlying facial muscles.
ii.
Curare, a poison certain So. American Indians have applied to hunting-dart
tips, occupies and blocks ACh receptor sites, leaving the neurotransmitter
unable to affect the muscles. The animal is paralyzed.
The Nervous System
A.
What are the functions of the nervous system’s main divisions?
1.
To take I information from the world and the body’s tissues
2.
To make decisions
3.
To send back information and orders to the body’s tissues
B.
Main divisions
1.
Peripheral nervous system
a.
Body’s sensory receptors, muscles, and glands
b.
Two parts
i.
Autonomic – controls self-regulated action of internal organs and glands
a).
Sympathetic – arousing – stress and alertness, acceleration of
heartbeat
b).
IV.
V.
Parasympathetic – calming – de-stressing, deceleration of
heartbeat
ii.
Somatic – controls voluntary movements of skeletal muscles
2.
Central nervous system
a.
Composed of brain and spinal cord
b.
Neurons fire together, work together, and form networks
c.
Spinal cord connects the peripheral nervous system to the brain
i.
Ascending neural fibers send up sensory information
ii.
Descending fibers send back motor-control information
iii.
Reflexes are automatic responses to stimuli and illustrate the spinal cord’s
work. Do not involve the brain
d.
Reflex
i.
Skin receptor feels the heat of the flame
ii.
Sensory neuron passes information to the spinal cord
iii.
Interneurons carry information to motor neurons
iv.
Muscles jerk the hand away from the flame
The Endocrine System
A.
Endocrine glands secrete another form of chemical messengers – hormones
B.
Hormones travel through the bloodstream and affect other tissues including the brain. They influence
our interest in sex, food, and aggression
C.
Comparison and contrast between nervous and endocrine systems
1.
Both produce molecules that act on receptors elsewhere
2.
Differences: speed and effect
a.
Nervous system – fast and does not linger
b.
Endocrine system – slow and lingering
D.
Adrenal glands
1.
Pituitary gland
a.
Controlled by the hypothalamus (region of the brain)
b.
Secretes many different hormones, some of which affect other glands
c.
Master gland since it sets other glands into action
2.
Thyroid gland – affects metabolism, among other things
3.
Adrenal glands – inner part helps trigger the “fight-or-flight” response
4.
Testis – secretes male sex hormones
5.
Ovary – secretes female sex hormones
6.
Pancreas – regulates the level of sugar in the blood
7.
Parathyroids – help regulate the level of calcium in the blood
Path
A.
Brain  pituitary  other glands  hormones  brain
B.
Nervous system directs endocrine secretions; endocrine secretions affect the nervous system
C.
Always controlling is the brain