Transcript Unit 2 Notes

Introductory Psychology:
Biological Bases of Behavior
AP PSYCHOLOGY: UNIT II
Topic: Neurons and
Neurotransmitters
Everything that is biological, is
simultaneously psychological…
Paul Broca: (1824 – 1880)
 Studied brain lesions and made connection to
speech/language
 Determined left frontal lobe to be center for language
production

“Broca’s area”
 One of first discoveries of a separation of function between
left and right hemispheres
 Broca’s aphasia
 Damage to frontal lobe

Individuals can comprehend speech but have difficulty expressing thoughts
Carl Wernicke (1848 – 1905)
 Related nerve diseases to specific areas of the brain
 Discovered structure in left temporal lobe
controls language comprehension
 “Wernicke’s area”
 Wernicke’s aphasia
 Speak in garbled sentences and poor speech
comprehension
Roger Sperry (1913 – 1994)
 Studied psychology and zoology
 Human beings are of two minds
 Two hemispheres can operate independently
 Won Nobel Prize (medicine)
 Split-brain research
 Research helped chart map of brain and led to
expansion of field
Michael Gazzaniga (1939 - )
 Worked under Roger Sperry
 Understanding of functional lateralization
 How
some cognitive functions tend to be
dominated by one side or the other
 Studied how cerebral hemispheres
communicate
 Professor of psychology at UC Santa Barbara
The Biological Bases:
Cells of the Nervous System
PART ONE
Imagine that you are watching an
action-packed movie. As the tension
mounts, your palms sweat and your
heart beats faster. You begin
shoveling popcorn into your mouth,
carelessly spilling some into your
lap. If someone were to ask you
what you were doing in that
moment, how would you respond?
Biological Bases: Cells
 The Nervous System

An extensive network of specialized cells that
carries information to and from all parts of the
body; body’s information system
 Brain to the body, face and internal organs
 Senses to the brain

Two Major Types of Cells in the Nervous System
 Neurons (the basic building blocks)
 Glia (a neuron’s support system)
Biological Bases: Cells
 Neurons
 Individual
cells; basic
building block of the
nervous system
 Neurons
perform
three primary tasks:
receive, integrate and
transmit information
Biological Bases: Cells
 Afferent Neurons (Sensory Neurons)
 Carry information from the body’s tissues & sensory
organs to the brain & spinal cord (INWARD; access)
 Efferent Neurons (Motor Neurons)
 Carry information from the brain & spinal cord to the
body’s tissues & sensory organs (OUTWARD; exit)
 Interneurons
 CNS neurons that communicate internally and
intervene between sensory inputs and motor outputs
(make reflexes happen)
Dendrites
Terminal
Buttons
Node of
Ranvier
Soma
Nucleus
Axon (inside)
Myelin Sheath (covering)
Schwann
Cell
Biological Bases: Cells
 Basic Parts of a Neuron
 Soma (“body” in Greek)


Dendrites (“tree” in Greek)


Cell body; contains nucleus & chemical “machinery”
common to most cells
Branchlike structures that receive information from
other neurons
Axon (“axle” in Greek)

Tube-like structure that carries the neural message away
from the soma and to other cells (neurons)
Biological Bases: Cells
 Basic Parts of a Neuron
 Myelin Sheath


Terminal Branches/Buttons


Fatty substance produced by certain glial cells; encases
axon; helps insulate, protect & speed the neural impulse
Small knobs that secrete chemicals called
neurotransmitters (chemical messengers)
Synapse (“junction” in Greek)

Junction where information is transmitted from one
neuron to another
Biological Bases: Cells
The importance
of myelin is
evident in M.S.
In M.S. the
myelin sheath
degenerates
causing neural
communication
to slow down
Eventually leads
to the loss of
muscle control
Real Life Application: Neurons
Myelin Sheath & Multiple Sclerosis
Biological Bases: Cells
 Glia Cells (“glue” in Greek)
 Provide support for neurons

Deliver nutrients, produce
myelin, flush waste & dead
neurons and influence
information processing

Influence the generation of new
neurons during prenatal development

Outnumber neurons 10 to 1; account for 50% of the
brain’s total volume
Biological Bases:
The Neural Impulse
PART TWO
Alan Hodgkin & Andrew Huxley
Biological Bases: Neural Impulse
 Alan Hodgkin &
Andrew Huxley (1952)
 Studied squid giant
axon
 Unraveled
the
mystery
of the neural
impulse
 WHY
SQUID?
Semi-Permeable
Fluid
Allows ions to travel
both in and out of
the neuron
Inside the
Neuron
Ions are mostly
negative
Outside the
Neuron
Ions are mostly
positive
Biological Bases: Neural Impulse
 Resting Potential
A
neuron’s state when it is NOT firing a
neural impulse; a neuron at rest
 An
inactive neuron has a stable, negative
charge (-70 millivolts)
In this state the neuron is capable of
generating an action potential; ready to
fire
Biological Bases: Neural Impulse
 Action Potential
A
very brief shift in a
neuron’s electrical
charge that travels
along the axon; begins
at the soma
Neural messages travel
anywhere from 2 mph to 270 mph
Depolarization
occurs when
positive ions
enter the
neuron
making it
more prone to
fire an action
potential
Hyperpolarization
occurs when
negative ions
enter the neuron
making it less
prone to fire an
action potential
Biological Bases: Neural Impulse
 Absolute Refractory Period

After an action potential, the minimum length of
time during which another action potential
cannot begin
 The “recharging phase” (1-2 milliseconds)
 The nerve WILL NOT respond to a second
stimulus during this period
Biological Bases: Neural Impulse
 Threshold
 The level of stimulation
required to trigger a
neural impulse
 All-or-None Principle
 If a neuron fires it will
ALWAYS fire at the same
intensity (100%); the
intensity of the stimulus
DOES NOT matter
Biological Bases:
The Synapse
PART THREE
Biological Bases: The Synapse
 Synapse

A junction between the
axon tip of the sending
neuron and the dendrites
of the receiving neuron
 The action potential
CANNOT jump the gap
 How do action
potentials travel from
one neuron to another?
Biological Bases: Neural Impulse
 Like a neuron, a toilet has an
action potential. When you
flush, an “impulse” is sent
down the sewer pipe
 Like a neuron, a toilet has a
refractory period. There is a
short delay after flushing
when the toilet cannot be flushed again
because the tank is being refilled
Biological Bases: Neural Impulse
 Like a neuron, a toilet has a resting
potential. The toilet is “charged” when there
is water in the tank and is capable of being
flushed again
 Like a neuron, a toilet operates on the all-or-
none principle – it always flushes with the
same intensity, no matter how much force
you apply to the handle
Biological Bases:
Neurotransmitters
PART FOUR
Biological Bases: Neurotransmitters
 Neurotransmitters

A chemical messenger
that travels across the
synapse from one neuron
to the next; transmits
information
 Influences whether the
second neuron will
generate an action
potential or not
Biological Bases: Neurotransmitters
 Excitatory Effect

A neurotransmitter effect
that makes it MORE likely
the receiving neuron will
generate an action
potential
 The second neuron is
more likely to fire
 GREEN LIGHT
Biological Bases: Neurotransmitters
 Inhibitory Effect

A neurotransmitter effect
that makes it LESS likely
the receiving neuron will
generate an action
potential
 The second neuron is
less likely to fire
 RED LIGHT
Biological Bases: Neurotransmitters
Neurotransmitters bind to the receptors of the receiving neurons
in a lock & key mechanism
Biological Bases: Neurotransmitters
 Agonists
 Chemical substances that mimic or enhance the effects of
a neurotransmitter on the receptor sites of the next cell
 Increases or decreases the activity of that cell, depending
on the effect of the original neurotransmitter (excitatory
or inhibitory)
Example
Black widow venom – floods synapses
with ACh
 Violent muscle contractions and
convulsions
 Morphine, a man-made chemical
substance, is an endorphin agonist

Biological Bases: Neurotransmitters
 Antagonists

Chemical substances that
block or reduce a cell’s
response to the action of
other chemicals or
neurotransmitters
Example
 Curare is an acetylcholine (ACh) antagonist
that blocks motor neurons and paralyzes you
 Botulin – blocks ACh release – used to paralyze
underlying facial muscles
Biological Bases: Neurotransmitters
 Reuptake

Neurotransmitters in the
synapse are reabsorbed
into the sending neurons
through the process of
reuptake
 This process applies the
brakes on
neurotransmitter
action
Biological Bases: Neurotransmitters
 Acetylcholine (ACh)
 Characteristics
Located at neuromuscular junctions
 Involved in muscle action, learning,
attention, memory and arousal


Dysregulation


Alzheimer’s Disease
 ACh producing neurons deteriorate
Psychopharmacology
Curare (antagonist)
 Botulism (antagonist)
 Spider venom (agonist)

Is there a connection
between Botox &
Acetylcholine??
Biological Bases: Neurotransmitters
 Dopamine (monoamine)
 Characteristics


Involved in mood,
voluntary movement,
learning, attention,
motivation & emotion
Dysregulation
Parkinson’s Disease
 Schizophrenia


OVERSUPPLY or
UNDERSUPPLY?
Psychopharmacology

Cocaine (agonist)
Biological Bases: Neurotransmitters
 Norepinephrine (monoamine)
 Characteristics
Involved in mood, alertness and arousal
 Affects parts of the brain where attention
and responding actions are controlled


Dysregulation
Depressive disorders
 Attention Hyperactivity Disorder (ADHD)


Psychopharmacology

Adderall (agonist)
Biological Bases: Neurotransmitters
 Serotonin (monoamine)
 Characteristics
Involved in sleep, wakefulness, mood, appetite & arousal
 Appears to set an “emotional tone”


Dysregulation
Depression
 Obsessive-Compulsive Disorder
 Eating Disorders


Psychopharmacology
Antidepressants (agonists)
 Ecstasy and LSD (agonists)

Biological Bases: Neurotransmitters
 GABA (amino acid)
 Characteristics
The most common inhibitory neurotransmitter
 Reduces activity of neurons to which it binds
 Involved in sleep and the inhibition of movement; aids in
the regulation of anxiety


Dysregulation
Anxiety disorders
 Seizure disorders
 Insomnia


Psychopharmacology

Alcohol (agonist) & Valium (agonist)
Biological Bases: Neurotransmitters
 Glutamate (amino acid)

Characteristics
 The most common excitatory neurotransmitter
 Over half of all brain synapses release glutamate
 Involved in learning, memory formation and the
development of the nervous system

Dysregulation
 Schizophrenia
 Migraines
Biological Bases: Neurotransmitters
 Endorphins
 Characteristics
 Inhibitory neural regulators; controls the
release of other neurotransmitters
 Involved in pain relief and response to stress
 Reduce perception of pain
 Produce feeling of euphoria

Dysregulation
 Heightened state of rage or anxiety
 Overdoing their job

Psychopharmacology
 Morphine and Codeine