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Neuroscience
Neurons and Neurotransmitters
Biology in Psychology
 Biological Psychology
 branch of psychology concerned with the links
between biology and behavior
 some biological psychologists call themselves
behavioral neuroscientists,
neuropsychologists, behavior geneticists,
physiological psychologists, or
biopsychologists
The Neuron
 Neuron
 a nerve cell
 the basic building
block of the
nervous system
Parts of a Neuron
Cell Body (Soma): Life support center of the neuron. Houses
the nucleus and other major cell parts.
Dendrites: Branching extensions at the cell body. Receive
messages from other neurons.
Axon: Long single extension of a neuron, covered with myelin
[MY-uh-lin] sheath to insulate and speed up messages through
neurons.
Terminal Branches of axon: Branched endings of an axon that
transmit messages to other neurons.
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The Neuron
Action Potential and Threshold
Action Potential: A neural impulse. A
brief electrical charge that travels down
an axon and is generated by the
movement of positively charged atoms
in and out of channels in the axon’s
membrane.
Threshold: The level of stimulation
required to trigger the action potential
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Depolarization & Hyperpolarization
Depolarization: Depolarization occurs when
positive ions enter the neuron, making it more
prone to firing an action potential.
Hyperpolarization occurs when negative ions
enter the neuron, making it less prone to firing
an action potential.
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Refractory Period & Pumps
Refractory Period: After a neuron fires an action
potential it pauses for a short period to recharge
itself to fire again.
Sodium-Potassium Pumps: Sodium-potassium
pumps pump positive ions out from the inside
of the neuron, making them ready for another
action potential.
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Action Potential Properties
All-or-None Response: When the depolarizing
current exceeds the threshold, a neuron will
fire. If the depolarizing current fails to exceed
the threshold, a neuron will not fire.
Intensity of an action potential remains the
same throughout the length of the axon.
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Neural Communication
 Synapse [SIN-aps]
 junction between the axon tip of the sending neuron
and the dendrite or cell body of the receiving neuron
 tiny gap at this junction is called the synaptic gap or
cleft
 Neurotransmitters
 chemical messengers that traverse the synaptic gaps
between neurons
 when released by the sending neuron,
neurotransmitters travel across the synapse and bind
to receptor sites on the receiving neuron, thereby
influencing whether it will generate a neural impulse
Neural Communication
Neural Communication
Serotonin Pathways
Dopamine Pathways
Neural Communication
 Acetylcholine [ah-seat-el-KO-leen]
 a neurotransmitter that, among its
functions, triggers muscle contraction
 Endorphins [en-DOR-fins]
 “morphine within”
 natural, opiatelike neurotransmitters
 linked to pain control and to pleasure
Neural Communication
Neurotransmitter
molecule
Receptor site on
receiving neuron
Receiving cell
membrane
Agonist mimics
 Like Morphin
neurotransmitter
Antagonist
blocks
Like curare
neurotransmitter
Blood-Brain Barrier
• Barrier that separates
blood and the brain
and central nervous
system.
• Prevents toxic stuff
from entering brain
• Makes it hard to treat
chemical imbalances
in the brain