Transcript The Nervous System

Biological Psychology
Neural and Hormonal Systems – Module 3
How the Brain Governs Behavior – Module 4
Intro Psych
Sep 9-11, 2009
Classes #7-8
“So why do we have to study
biology in a psych class?”

Let me use Phineas
Gage to help answer
this question…
“He was no longer Gage…”

Several different
angles of where the
rod passed through
his skull
There is a Phineas Gage display in the Warren
Medical Museum at Harvard University
This is what went through his brain (see
below)…
 3½ feet in length; 1¼ inch in diameter

Some history buffs travel to the
tiny town of Cavendish, VT
Biological Roots of Behavior

Franz Gall (1758-1828)
– Austrian physicist who invented
phrenology
– He felt that bumps on the skull
could reveal our mental abilities
and character traits.
– Introduced as being scientific but
its use was exploited by “quacks
on gullible individuals”
– Became similar to that of
astrology, palm-reading and tarot
– Although, ill-fated theory was
laughed at by scientific
community of that day – it may
have had some validity
– Localization of brain
functions somehow hit the
mark
The Nervous System
Electrochemical communication system
that enables us to think, feel, and behave
 Complex beyond comprehension
 Although, human brains are more complex
our nervous systems and those of animals
operate in a similar fashion – advantage of
this is experimentation
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Major Components
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Neurons
– Rapidly respond to signals and quickly send
signals of their own

Glial cells
– Help neurons to communicate, keep chemical
environment stable, secrete chemicals to help
restore damage, and respond to signals from
neurons – enable neurons to function
Axons
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Function
– Carries signals away from the cell body
– Pass information along to other nuerons, or to
muscles or glands

Type of Signal Carried
– The action potential, an all-or-nothing
electrochemical signal that shoots down the
axon to vesicles at the tip of the axon,
releasing neurotransmitters
Synapse

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Very small gap between
neurons
For communication to
occur between cells, the
signal must be
transferred across this
gap
Function
– Provides an area for the
transfer of signals
between neurons, usually
between axon and
dendrite
Dendrite

Function
– Detects and carries signals to the cell body

Type of Signal Carried
– The postsynaptic potential, which is an
electrochemical signal moving toward the cell
body
Receptors

Function
– Proteins on the cell membrane that receive
chemical signals

Type of Signal Carried
– Recognizes certain neurotransmitters, thus
allowing it to begin a postsynaptic potential in
the dendrite
Okay, so how do neurons actually
transmit information?
A neuron:
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–
–
–
Receives signals form other neurons through
its branching dendrites and cell body
Then combines these signals in the cell body
And then transmits an electrical impulse
down its axon
Transmitting information…
The impulse is called the action potential which
is a brief electrical charge that travels down the
axon like a line of dominoes falling, each one
tripping up the next
 This is real electricity as a handful of neurons
produce enough power to light up a flashlight
 When electrical signals reach the end of the
axon, they stimulate the release of chemical
messengers – neurotransmitters

Neurotransmitters

Function
– A chemical released by one cell that binds to
the receptors on another cell

Type of Signal Carried
– A chemical message telling the next cell to
fire or not to fire its own action potential
The Nervous System

Allows researchers to study simple animals
such as squids and sea slugs to help us
better understand the organization of our
own brains
Divisions of the Nervous
System

Consists of two systems
– Central Nervous System
 Brain and spinal cord
– Peripheral Nervous System
 Which connects the CNS to the rest of the
body
Organization of the Nervous System
Peripheral Nervous System

Two components:
– Somatic Nervous System
 Transmits sensory input to the CNS from
the outside world and directs motor output
– Autonomic Nervous System
 Controls glands and muscles of our internal
organs – “automatic pilot”
Autonomic Nervous System
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Dual system:
– Sympathetic Nervous System
 Arouses the body
– Parasympathetic Nervous System
 Calms us down
Neurons

Nerve cells (building blocks) – essentially
identical to animals
– Small samples of brain tissue from a person
and a monkey are basically indistinguishable
Endocrine System: Taking the slow lane
Unlike the speedy nervous system which
zips messages from eyes to brain to hand
in a fraction of a second, endocrine
messages use the slow lane
 May take several seconds or more as
bloodstream carries a hormone from an
endocrine gland to its target tissue

Endocrine System
Hormones are chemical messengers
 Influence all aspects of our lives – growth,
metabolism, reproduction, moods, etc.
 Strives for homeostasis (balance) by
responding to stress, exertion, internal
thoughts, etc.

The Brain

Studying the brain:
– Clinical observations
– Manipulating the brain
How does the brain govern
behavior?

3 Principle layers of the brain:
– Brainstem
– Limbic System
 Hippocampus
 Amygdala
 Hypothalamus
– Cerebral Cortex
Brainstem (or Hindbrain)

The brain’s innermost region…
– Begins where the spinal cord enters the skull
and swells slightly forming the medulla
– Towards the rear of the brainstem is the
cerebellum – this is linked to memory and its
major function is muscular control
Limbic System
Limbic System

Hippocampus
– This structure plays a key
role in allowing us to store
new information
– Problems here may cause
Alzheimer's – these
individuals have trouble
processing declarative
memories
– Milner (1968): the classic
case of H.M.
Limbic System

Amygdala
– Emotional control center of the brain – major
influence on aggression and fear
– Emotional memories as well
– Alzheimer’s ???
 Kluver and Bucy (1939)
 Demasio (1994)
Limbic System

Hypothalamus
– Major influence on hunger, thirst, body
temperature, and sexual behavior
 Olds and Milner (1954)
Cerebral Cortex
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Makes us distinctively
human – much higher
developed than in animals
– Motor Cortex – involved in
the conscious initiation of
voluntary movements in
specific parts of the body
including hand, knee, foot and
head
Fritsch and Hitzig (1870)
 Delgado (1969)
 Penfield (1975)
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Cerebral Cortex
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Sensory Cortex
– receives information from our senses
 Visual cortex
– visual info
 Auditory cortex
– auditory info
 Somatosensory cortex
– info from skin
Association cortex
– involved in complex cognitive tasks associating words
with images
 Broca’s area (aphasia)
 Wernicke’s area (aphasia)
Neurotransmitters
Neurotransmitters are chemicals made by
neurons and used by them to transmit signals to
the other neurons
 A chemical message telling the next cell to fire
or not to fire its own action potential
 More than 200 in our body all with different
functions
 Lets briefly discuss some of the most important
ones…

Serotonin

Facilitates a relaxed,
sleepy feeling
– Tryptophan an amino
acid found in dairy
products and turkey is
converted into serotonin
in the body
– So, insomnia sufferers
may be smart to listen
to grandmother’s
suggestion to drink a
warm glass of milk
before going to bed
Some Illnesses Associated With Serotonin
Too low levels in depression and anxiety
sufferers
 Obesity may also be associated with low
levels
 Linked to aggression as well -- low levels
in the brains of suicide victims
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Dopamine
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High levels lead to pleasure
– Makes person feel happy and active
Dopamine raises the body's temperature and
increases metabolic rate
Gives you euphoric feelings and allows you to
be active
Drug and alcohol abuse will block dopamine
receptors and therefore a person needs to take
more to get the same effect
Illnesses Associated With Dopamine

Parkinson’s Disease
– too low levels
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Schizophrenia
– too high levels
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Tourette’s disorder
– too high levels
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Huntington’s disease
– too high levels
Norepinephrine
Plays a role in attention and arousal
 Used by sympathetic nervous system to
prepare us for action
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Illnesses Associated With
Norepinephrine

Depression
– chronic stress depletes this neurotransmitter
and can lead to depression

Note:
– Aerobic Exercise is found to protect the brain
from this depletion – so go out and run a mile
or two if your down in the dumps
Epinephrine
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Involved in energy and glucose
metabolism
Illnesses Associated With Epinephrine

Depression – too low levels
Acetylcholine
Involved in voluntary movement, learning,
memory, and sleep
 Helps parasympathetic nervous system to
slow our heart rate
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Illnesses Associated With
Acetylcholine
Alzheimer’s disease – too low levels
 Note:

– Unfortunately, drugs used to increase
acetylcholine to help restore normal levels
appear to have small effects on improving
memory
GABA
Inhibits excitation and anxiety
 Appears directly related to anxiety
reduction

Illnesses Associated With
GABA
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Anxiety disorders – too low levels
Huntington’s Disease – too low levels
– GABA systems aren’t working and this allows
dopamine systems to run wild
– Huntington's disease is a hereditary disorder
characterized by memory loss, abnormal
movement and premature death
 It affects 1 in 10,000 people, and children with an
affected parent have a 50 percent chance of developing
the disease

Epilepsy – too low levels
Glutamate
Main excitatory neurotransmitter in the
brain
 Very important in learning and memory

Illnesses Associated With
Glutamate
 Alzheimer’s
disease
– too low levels in hippocampus
 Strokes
– too high levels can cause neurons to die
 ALS
(Lou Gehrig’s Disease)
– causes death in neurons in the spinal cord
and brainstem
Endorphins
Involved in pain reduction and pleasure
 They enhance the release of dopamine
 These natural opiates are released in
response to pain and vigorous exercise

Illnesses Associated With Endorphins

Use of artificial opiates can cause body to
stop manufacturing its own – this can lead
to drug addiction