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What is the neural basis of behavior?
• Molecular vs. Molar levels of analysis
• The Neuron
–Structure
–Electrical and Chemical Action
• The Action Potential and the All-or-None Law
–Synaptic Transmission
–Neurotransmitters
(See Gleitman, p. 63)
Nodes of Ranvier
(cell nucleus)
Axon
Myelin sheath
(cell body)
Dendrites
Axon terminals
(See Gleitman, p. 70)
Axon
Recording electrodes
At threshold:
At 160% of threshold:
At 270% of threshold:
500 msec
(See Gleitman, p. 68)
The action potential
Voltage change over Time
40
Inside voltage (mV)
depolarization
resting
potential
repolarization
20
0
-20
hyperpolarization
-40
-60
-80
0
(polarized)
1
2
Time (milliseconds)
refractory period
Stimulus onset
3
4
5
These axon terminals have
excitatory effects.
Dendrite
Axon
These axon terminals have
inhibitory effects.
Temporal summation:
several impulses from one source over time
Dendrites
Spatial summation:
several impulses from several
sources converging at the
same time
(See Gleitman, p. 69)
(outside)
(inside)
K+
Na+ Na+
K+
Na+
K+
(outside)
Na+
Na+
Na+
(inside)
(See Gleitman, p. 72)
Axon of the
sending
neuron
Neural impulse
Axon terminal
Synaptic
vesicle
Synapse
(Synaptic gap
or cleft)
Presynaptic
membrane
Binding site
Postsynaptic
membrane
Neurotransmitter
molecule
Receiving neuron
A brief selection of well known
neurotransmitter substances
(from Gleitman, pp. 73-75):
• Acetylcholine (+)
• Serotonin (+)
• Catecholamines:
– Dopamine (+)
– Norepinephrine (+)
• Amino Acids
– GABA (-)
– Glutamate (+)