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Thinking About Psychology:
The Science of Mind and
Behavior 2e
As before, with much thanks to:
Charles T. Blair-Broeker
Randal M. Ernst
Neuroscience and
Behavior
Neuroscience –
scientific study of the
nervous system
• Nervous system- body’s primary
communication network
• The nervous system is closely linked to
the endocrine system – system of glands
that secrete hormones into the blood
stream.
Nervous System
• The electrochemical
communication
system of the body
• Sends messages from
the brain to the body
for movement
• Brings information
to the brain from the
senses
Neurons:
The Building Blocks of
the Nervous System
Neuron
• A nerve cell; the basic building block of the
nervous system
• There may be as many as 100 billion
neurons in the brain
• Neurons perform three basic tasks
– Receive information
– Carry the information
– Pass the information on to the next neuron
Parts of the Neuron
Parts of the Neuron - Dendrites
Dendrite – The branching extensions of a neuron that receive
information and conduct impulses toward the cell body
Parts of the Neuron - Soma
Soma – The cell body of a neuron, which contains the nucleus
and other parts that keep the cell healthy
Parts of the Neuron - Axon
Axon – The extension of a neuron through which neural
impulses are sent
Parts of the Neuron – Myelin Sheath
Parts of the Neuron - Terminals
Axon terminals – The endpoint of a neuron where
neurotransmitters are stored
• Glial Cells
– Specialized support cells for the neurons
– More numerous (10x) than neurons
•
•
•
•
Structural support
Nutrition
Remove waste
Perhaps involved in communication between
neurons, enhances speed
Types of Neurons
• Sensory Neurons (aka afferent neurons)
– Tell us about the environment; share
information from specialized receptor cells (in
various sense organs) with the brain; also
carry info from skin and organs to the brain
• Motor Neurons (aka efferent neurons)
– Gets us moving; sends info to the muscles
and glands
• Interneurons (aka relay or connector neurons)
– Share info between neurons (there are more
of these than the previous two)
Quick question?
What’s the longest axon in your body?
{Remember most neurons are terribly
small}
It’s found on the motor neuron that works
your big toe.
For a basketball player (7’) it’s 4 feet long;
for most people it’s about 3 feet long.
Module 6: The Nervous System and the Endocrine System
How Neurons
Communicate:
The Neural Impulse
Action Potential
• A neural impulse; a brief electrical
charge that travels down the axon of a
neuron
• Considered an “on” condition of the
neuron
Changes in charge across the membrane causes
ion channels to open and close. In response to
depolarization, Na+ channels open quickly and
close slowly. While K+ channels open slowly and
close slowly in response to depolarization.
A neuron has to re-set itself after every reaction for
the next reaction. Na+ is moved back out while K+ is
moved back in. One protein pumps both potassium
and sodium out with the use of energy because both
are moving against the concentration gradients. The
nerve re-sets itself by pumping 3 Na+ out and 2 K+ in,
which is not an equal exchange. Active transport
proteins in the membrane are responsible for
pumping Na+ out and K+ in. These proteins require a
great deal of energy, or ATP
• Each neuron requires a minimum level of stimulation
from other neurons to be activated (stimulus
threshold).
– While waiting to be stimulated it is said the neuron is
polarized.
– In this state the axon’s interior is more negatively
charged than the exterior fluid surrounding the axon.
• This condition is due to primarily to different ions:
potassium and sodium.
• While the neuron is at resting potential (-70 mv), the
fluid surrounding the fluid surrounding the axon contains
a larger concentration of sodium ions than does the fluid
within the axon. The fluid within contains a larger
concentration of potassium.
• Once stimulated by other neurons or sense receptors,
neuron depolarizes beginning action potential…Na+
rush in and K+ rush out and charge of axon is
momentarily changed to +30mv (this is the action
potential) it happens at each segment of the axon and it
goes through the whole process at each segment until it
reaches the end and it goes from start to finish through
the neuron due to the all-or-nothing principle. After the
action potential there is a refractory period where the
neuron repolarizes and makes it negative inside and
positive outside again(another progressive segment by
segment movement) and we’re back at the resting
potential.
Action Potential
Refractory Period
• The “recharging phase” during which a
a neuron, after firing, cannot generate
another action potential
• Once the refractory period is complete
the neuron can fire again
Refractory Period
Resting Potential
• The state of a neuron when it is at rest
and capable of generating an action
potential
• The neuron is set and ready to fire
Resting Potential
All-or-None Principle
• The principle stating that if a neuron
fires it always fires at the same intensity
• All action potentials are of the same
strength.
• A neuron does NOT fire at 30%, 45% or
90% but at 100% each time it fires.
What’s the speed of Neuron
Communication?
• The fastest neural messages zoom around
at 270 mph
• The slowest neural messages creep by at
2 mph
• These speeds are based on:
– the size of the axon (the greater the
diameter, the faster it moves)
– the myelin sheath (myelinated neurons are
faster than non)
A Neural Chain
A Neural Chain
A Neural Chain
A Neural Chain
A Neural Chain
Module 6: The Nervous System and the Endocrine System
How Neurons
Communicate:
Communication
Between Neurons
Types of Neural Communication
• Electrical
– almost instantaneous; only 1% ‘talk’ this way
• Chemical
– involves neurotransmitters; 99% of neurons
engage in this 1-way conversation
• Chemical communication occurs
when the presynaptic neuron
(message sending) creates a
chemical substance
(neurotransmitter) that diffuses
across the synaptic gap and is
detected by the postsynaptic neuron
(receiving neuron).
Synapse
• The point of communication between two
neurons
• The tiny, fluid filled gap between the axon
terminal of one neuron and the dendrite of
another neuron, synaptic gap.
– The action potential cannot jump the gap
1. Presynaptic neuron is activated, it generates an action potential
that travels to the end of the axon.
2. The end of the axon has several small branches called axon
terminals.
3. Floating in the interior fluid of the axon terminals are tiny sacs
called synaptic vesicles.
4. The synaptic vessels hold special chemical messengers
manufactured by the neuron called neurotransmitters.
5. NT cross the synaptic gap and attach to the receptor sites on the
dendrites surrounding neurons, synaptic transmission.
6. They will then detach and are reabsorbed by the presynaptic
neuron so they are recycled and reused, reuptake.
Neurotransmitters
3. After attachment,
what happens? Usually reuptake - the neurotransmitters, detach
and are reabsorbed by the
presynaptic neuron, to be used
again
NT communicates either an excitatory message
or an inhibitory message.
Excitatory Effect
• A neurotransmitter effect that makes it
more likely that the receiving neuron
will generate an action potential or
“fire”.
Inhibitory Effect
• A neurotransmitter effect that makes it
less likely that the receiving neuron will
generate an action potential or “fire”
• The effect of the NT depends on the receptor
site on to which it binds, could have an
excitatory effect on one and an inhibitory on
another.
• On average, each neuron in the brain
communicates directly with 1,000 other neurons.
Thus, there are up to 100 TRILLION synaptic
interconnections.
• There are nearly a thousand times more
synaptic connections in your brain than
there are stars in the entire galaxy!!
NT and Their Effects
• Physical functioning
• Psychological functioning
• Too much or too little can have devastating effects
Yet they are present in extremely tiny amount in our brains!
• Effects can be the result of complex interactions of
different NT and NT have different effects in different
areas of the brain.
Acetylcholine
• 1st neurotransmitter discovered
• Present in all motor neurons
• Stimulates muscles to contract (heart and stomach
too)
• Also useful in learning, memory & general thinking
• Patients with Alzheimer’s have very little Ach as well
as a depletion of other NT
• Nerve gas causes Ach to be continuously released
causing severe muscle spasms that suffocate the
victim. Atropine blocks Ach receptor sites saving
victims from the nerve gas.
• http://www.psychologytoday.com/blog/brai
n-babble/201208/paralyze-your-face-fightdepression
Dopamine
• Useful in movement, attention, learning and pleasurable
sensations
• Addiction to drugs (e.g. nicotine and cocaine) related to
how the drugs increase dopamine’s activity in the brain
• Parkinson’s is caused – in part – by deterioration of
dopamine producing neurons in the brain; counteracted
some by L-dopa
• Too much dopamine is associated with hallucinations in
schizophrenia (drugs work to block dopamine receptors
and decrease levels in the brain)
• http://www.psychologytoday.com/blog/gre
aseless/201112/score-dopamine-repeator-not
Serotonin
• Sleep, moods,
emotions, hunger
• Prozac makes
serotonin more
available
& Norepinephrine
• Learning & memory
retrieval
• Get ready to fight…
or RUN!
• (aka noradrenalin)
• Involved with
depression and other
woes
• http://www.psychologytoday.com/blog/theantidepressant-diet/201008/serotoninwhat-it-is-and-why-its-important-weightloss
• http://www.psychologytoday.com/blog/psy
chology-writers/201104/triggering-thewarrior-gene-in-villain-or-hero
• http://www.psychologytoday.com/blog/yout
h-and-consequences/201001/why-teensaddict-the-elusive-search-happiness
GABA: gamma-aminobutyric acid
• Primarily in the brain
• Inhibits neurons, helping to balance and offset
excitatory messages
• But very delicate
• Too much GABA and learning, motivation and
movement are adversely affected
• Too little GABA can cause seizures
• Alcohol works by activating GABA  relaxation
• Same with valium and xanax
Too bad ?! oral GABA doesn't cross the blood brain barrier or even make it out of the digestive tract into the bloodstream.
• http://www.psychologytoday.com/blog/brai
n-sense/201207/new-study-reveals-levelsbrain-neurotransmitter-may-be-key-inadhd
Endorphins
(aka endogenous morphines)
• Pert & Snyder (1973) discovered brain’s
opiate (morphine, heroine, codeine –
derived from the opium poppy) receptor
sites, which led to the discovery of
endorphins, the body’s own painkillers
(100x more potent)
• Released in response to stress or trauma
and lower pain perception
• http://www.psychologytoday.com/blog/brai
n-bootcamp/201009/can-exercise-curedepression
Neurotransmitters
Neurotransmitters (cont.)
Neurotransmitter
Functions
Problems
Norepinephrine
arousal
learning
memory
depression, stress
GABA
inhibition of
brain activity
anxiety disorders
Endorphins
pain perception
positive emotions
opiate addiction
Module 6: The Nervous System and the Endocrine System
The Structure of the
Nervous System
The Nervous System
Neurons and nerves are not
the same thing: Nerves are
comprised of bundles of
axons.
As many as 1 trillion
neurons comprise the
nervous system
The Nervous System
• Central Nervous System & The Peripheral
Nervous System
Central Nervous System (CNS)
• The brain and spinal cord
• Both of which are protected by bone, skull or spinal
column and buoyed by the CSF: cerebrospinal fluid
• The brain is the location of most information
processing.
• The spinal cord is the main pathway to and from the
brain.
• The Neuron is the most important message carrier.
• All thoughts, feelings, and sensations go through the
CNS.
• Brain is the command center.
• Spinal cord is like a old fashioned, switch board sending
messages and receiving messages.
– Sensory receptors send messages along sensory
nerves to the spinal cord and then up to the brain.
– To activate muscles the brain sends signals down the
spinal cord to motor nerves to the muscles.
– Most behaviors are controlled by the brain.
Spinal Reflex Arc
simple behavior without brain involvement
In a simple reflex arc, such as the knee
jerk, a stimulus is detected by a
receptor cell, which connects with a
sensory neuron. The sensory neuron
carries the impulse from the
site of the stimulus to the central
nervous system (spinal cord), where it
connects with an interneuron. The
interneuron connects with a motor
neuron, which carries the nerve
impulse to an effector, (a muscle),
which responds by contracting.
Divisions of the Nervous System
Divisions of the Nervous System
Peripheral Nervous System (PNS)
• The sensory and motor nerves that connect the brain and the
spinal cord to the rest of the body
• Peripheral means “outer region”
– Communication occurs along bundles of nerves.
• The system is subdivided into the somatic and autonomic
nervous systems.
Divisions of the Nervous System
Somatic Nervous System
• The division of the peripheral nervous system that controls
the body’s skeletal muscles.
• Contains the motor nerves needed for the voluntary muscles.
• Communicates sensory information from sensory receptors
along sensory nerves to the CNS.
Divisions of the Nervous System
Autonomic Nervous System
• The division of the peripheral nervous system
that controls the glands and muscles of the
internal organs
• Monitors the autonomic functions
• Controls breathing, blood pressure, and
digestive processes
• Sub-divided into the sympathetic and
parasympathetic nervous systems
• Not fully automatic, tensing or relaxing
muscles or being very active can raise or
lower autonomic functions, also mental
imagery can work in the same way.
Divisions of the Nervous System
Sympathetic Nervous System
• The part of the autonomic nervous system that
arouses the body to deal with perceived threats
• Fight or flight response
– Heart rate increases, digestion stops,
and the bronchial tubes in your lungs
expands…increasing the amount of
oxygen to the brain and muscles.
Pupil dilate to increase vision, your mouth
becomes dry. Sweating occurs due to the increase
in energy and heat. This happens to help you deal with the
situation but can lead to exhaustion.
• Emotional arousal involves your
sympathetic nervous system.
• Heightened arousal can also work against
you.
Divisions of the Nervous System
Parasympathetic Nervous System
• The part of the autonomic nervous
system that calms the body
• Brings the body back down to a relaxed
state
The Sympathetic and Parasympathetic Divisions of the
Autonomic Nervous System
The Sympathetic and Parasympathetic Divisions of the
Autonomic Nervous System
The Sympathetic and Parasympathetic Divisions of the
Autonomic Nervous System
The Sympathetic and Parasympathetic Divisions of the
Autonomic Nervous System
The Sympathetic and Parasympathetic Divisions of the
Autonomic Nervous System
The Sympathetic and Parasympathetic Divisions of the
Autonomic Nervous System
The Sympathetic and Parasympathetic Divisions of the
Autonomic Nervous System
Module 6: The Nervous System and the Endocrine System
The Endocrine
System
Endocrine System
• One of the body’s two communication
systems
• A set of glands that produce hormones-chemical messengers that circulate in
the blood until they reach the
appropriate receptor sites at destination
organ or tissue
Hormone
• Chemical messengers produced by the endocrine
glands and circulated in the blood
• Similar to neurotransmitters in that they are also
messengers
• Slower communication system, but with longer
lasting effects
• Regulate metabolism, growth rate, digestion, blood
pressure, and sexual development and reproduction.
• Also involved in emotional response and your
response to stress.
• Release of hormones may be stimulated
or inhibited by parts of the nervous system
(flight or fight).
• Hormones can promote or inhibit nerve
impulses.
• Some hormones and neurotransmitters
are chemically identical.
Pituitary Gland
• The endocrine system’s gland that, in
conjunction with the brain, controls the
other endocrine glands
• Called the “master gland”
• Located at the base of the brain and & &
connects to the hypothalamus
• Hypothalamus is the liaison
between the endocrine and nervous system
• Pituitary gland produce growth hormone
and also prolactin & oxytocin
Endocrine System – Pituitary Gland
Adrenal Gland
• Endocrine glands that help to arouse the body in times of stress
• Located just above the kidneys
• Releases epinephrine (adrenaline) and norepinephrine
– During emergencies, when the body needs to be alert, responsive,
and self-preserving, epinephrine sends chemical hormonal
messages throughout the body to allow for greater muscle strength,
stronger lung functions, greater blood volume, and enhanced
senses.
– Norepinephrine works like epinephrine in that it also increases blood
pressure and stimulates respiration and gastrointestinal contractions,
but the two chemicals balance each other. Norepinephrine
decreases heart rate and increases the actions of the peripheral
nervous system by constricting blood vessels. It also constricts blood
vessels in the muscles and skin, and decreases stimulation of the
bronchial airways in the lungs to return the body to a state of
homeostasis or of basic daily functioning.
Thyroid Gland
• Endocrine gland that helps regulate the
energy level in the body
• The thyroid secretes several hormones, collectively called thyroid
hormones. The main hormone is thyroxine, also called T4. Thyroid
hormones act throughout the body, influencing metabolism,
growth and development, and body temperature. During infancy
and childhood, adequate thyroid hormone is crucial for brain
development.
Endocrine System – Thyroid Gland
Endocrine System – Adrenal Gland
Pancreas
• Regulates the level of blood sugar in the blood and
impacts hunger and eating
• Two of the main pancreatic hormones are insulin,
which acts to lower blood sugar, and glucagon, which
acts to raise blood sugar. Maintaining proper blood
sugar levels is crucial to the functioning of key organs
including the brain, liver, and kidneys.
Endocrine System – Pancreatic Gland
Sex Glands (aka gonads)
• Ovaries (females) and testes (males) are
the glands that influence emotion and
physical development.
• Testosterone – primary male hormone
• Estrogen – primary female hormone
• Males and females have both estrogen
and testosterone in their systems.