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Biological Psychology
Key Point for this Unit:
Everything psychological is
simultaneously biological!!
NEURON
Dendrites
Dendrites – receive messages from other cells
and conduct impulses toward the cell body
NEURON
Dendrites
Cell Body
Cell Body – the cell’s life-support center
NEURON
Dendrites
Cell Body
Axon
Axon – the extension of a neuron through which messages
are sent to other neurons or to muscles or glands
NEURON
Dendrites
Cell Body
Axon
Myelin Sheath
Myelin Sheath – a layer of fatty cells covering
the axon, helps speed neural impulses
NEURON
Dendrites
Terminal branches of axon
Cell Body
Axon
Myelin Sheath
Terminal branches of axon – form junctions
with other cells
Biological Psychology
It is all about the body!!!!
Concerned with the links between biology and
behavior (also called Neuroscience)
The Nervous System
It starts with a NEURON: an
individual nerve cell; the basic
building block of the nervous
system
How does a Neuron fire?
• Resting Potential: slightly
negative charge.
• Reach the threshold when enough
neurotransmitters reach
dendrites.
• Threshold: level of stimulation
required to trigger a neural
impulse; excitatory signals minus
inhibitory signals must equal a
minimum intensity
• Go into Action Potential; a neural
impulse (brief electrical charge)
that travels down an axon.
• All-or-none response.
Neurons – How do they work?
• Neurons send messages to other
neurons – this is what keeps every
part of our body in communication with
every other part.
• Neurons “fire” – send an impulse
(message) down their length – or they
don’t “fire”
Action Potentials
Watch “The
Action Potential”
movie at home:
http://brainu.org/files/movies
/action_potential_cartoon.swf
• This “firing” of impulse messages is
called the action potential.
• An action potential is a brief
electrical charge that travels down
the axon of the neuron.
Play
Animation
What causes an impulse to
fire or not fire?
• When a neuron is at rest and capable of
generating an action potential, it is called
the resting potential
• There are fluids inside and outside of the
neuron, filled with electrically charged
particles (ions)
• When the neuron is at rest, there is a
negative charge on the inside of the
neuron compared to the outside.
• At rest, the inside of the cell is at -70
millivolts
Neuron Communication
Resting Potential
Action Potentials, cont.
• Stimulation from inputs to dendrites causes
the cell membrane to open briefly
• Positively charged sodium ions flow in
through the cell membrane
• If resting potential rises above threshold,
an action potential starts to travel from the
cell body down the axon
– Threshold - Each neuron receives excitatory and
inhibitory signals from many neurons. When the
excitatory signals minus the inhibitory signals
exceed a minimum intensity (threshold) the
neuron fires an action potential.
Figure 2.3 Action potential
Myers: Psychology, Ninth Edition
Copyright © 2010 by Worth Publishers
Action Potential, cont.
• The shift in electrical charge travels
along the neuron
• The intensity of an action potential
remains the same throughout the
length of the axon
• Refractory period - The “recharging
phase” when a neuron, after firing,
cannot generate another action
potential
To help a mad
scientist make a
“mad, mad, mad
neuron” in a cartoon
game, see
http://learn.genetics.
utah.edu/content/add
iction/reward/madneu
ron.html
For more information on action
potentials, see
http://faculty.washington.edu/chudl
er/ap.html
For an interactive game/demo to
help you learn about action
potentials, see
http://outreach.mcb.harvard.edu/a
nimations/actionpotential_short.swf
Neuron Communication
All-or-None Principle
• The principle that if a neuron
fires it will always fire at the
same intensity
• A strong stimulus can trigger
more neurons to fire, and to
fire more often, but all action
potentials are of the same
strength and speed.
• A neuron does NOT fire at
30%, 45% or 90% but at
100% each time it fires.
Just like a gun,
there is no
“part-way”
firing
How is a neuron firing similar to a
toilet flushing?
• Consider the following concepts:
– Depolarization
– All-or-none principle
– Direction of impulse
– Refractory period
– Threshold
– Resting potential
– Action potential
How about a school bus?
See “The School Bus
Story” ppt. here:
http://ap-psychology1st.grandblanc.high.schoolf
usion.us/modules/locker/fil
es/group_files.phtml?gid=
1316804&parent=4425886
&sessionid=8b85e917de89
43dc49c835c286f82aff
The School Bus Story
A tale of ionic influence on action
potentials
Setting the stage
• Imagine a school bus, filled with unhappy
kids on their way to school…
Meanwhile…
• Outiside, it’s a BEAUTIFUL day!
– Sun is shining
– Birds are chirping
– Everything is happy
The point is…
• The unhappy (negative) kids, sealed
inside their impermeable school bus,
cannot get to the happiness (positivity)
outside!
All of a sudden…
• The bus driver opens the door! Yay! The
bus is now permeable… but only in a
selected place.
Area of
selective
permeability
And then?
• Sunlight, happiness, butterflies, and
positivity fill the negative kids on the bus
with deep inner joy.
Yay, happy kids!
• If enough kids go from sad to happy when
the beautiful air whooshes in, they have
reached the “threshold.” If/when this
threshold is reached, they start getting
rambunctious ("action potential").
• After having wasted their energy being
rambunctious, there's a short time
("refractory period") before they can start it
up again.
How does this relate?
•
•
•
•
The kids = negative ions.
The bus = an axon.
The sunlight = positive sodium ions.
The bus pre-open door = a polarized neuron in
its resting potential.
• The driver = cell nucleus.
• The opened door = selectively permeable gates.
• The happy kids = an action potential… but only if
enough of them become happy!
What happens when an action
potential reaches the end of the
axon and enters the terminal
buttons?
TYPES OF
NEUROTRANSMITTERS
Chemical messengers that that traverse the synaptic
gap between neurons
REVIEW… remember
agonists and antagonists???
Agonist – mimic neurotransmitters
**Example: Morphine mimics endorphins
Antagonist – block neurotransmitters
**Example: Poison blocks muscle
movement
Did you know? Botox is an antagonist that paralyzes facial muscles!
Acetylcholine (ACH)
• Involved with
voluntary muscle
movement, learning
and memory
• Lack of ACH has
been linked to
Alzheimer’s disease.
Dopamine
• Deals with motor
movement and
alertness.
• Lack of dopamine
has been linked to
Parkinson’s disease.
• Too much has been
linked to
schizophrenia.
Serotonin
• Involved in mood
control.
• Lack of serotonin
has been linked to
clinical depression.
Endorphins
Did you know? The word
“endorphin” literally means
“morphine within”!
• Involved in pain
control.
• Many of our most
addictive drugs deal
with endorphins.
“Runner’s High”
occurs when your
brain signals the
release of
endorphins to
reduce pain!
The Nervous System
The Nervous System - body’s speedy,
electrochemical communication network consisting
of nerve cells
Central Nervous System (CNS)
• The Brain
and spinal
cord
• Neural networks –
interconnected neural
cells; more
connections made as
experience gained
Peripheral Nervous System (PNS)
• All nerves that are
not encased in bone.
• Sensory and motor
neurons that connect
the CNS to the rest of
the body
• Is divided into two
categories….somatic
and autonomic.
Somatic Nervous System
• Controls voluntary
muscle movement.
• Uses motor neurons.
Autonomic Nervous System
• Controls the
automatic functions
of the body.
• Divided into two
categories…the
sympathetic and the
parasympathetic
Sympathetic Nervous System
• Arouses the body
• Fight or Flight
Response.
• Automatically
accelerates heart
rate and breathing,
dilates pupils
Parasympathetic Nervous System
• Calms the body
• Automatically slows
the body down after
a stressful event.
• Heart rate and
breathing slow down,
pupils constrict
Sympathetic and
Parasympathetic
Types of Neurons
• Sensory Neurons –
sends receptors to
CNS
• Interneurons – internal
communication neurons
• Motor Neurons – CNS
to muscle and glands
• Normally, sensory
neurons take info up
through spine to the
brain.
• With reflexes
though, some
reactions occur when
sensory neurons
reach just the spinal
cord.
• Automatic response
to sensory stimulus;
interneurons react to
sensory neurons w/o
going to brain
Reflexes