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Brain and Behaviour
Second Hour – How do neurons communicate?
Afferent (sensory) and Efferent (motor) nerves revisited
•A demonstration
•Interneurons
Parts of the neuron
Neuronal communication
•Electrical and chemical
Spatial and temporal summation
Average Individual Reaction Time
Measuring the speed of the nervous impulse
.55
.50
.45
Shoulder with decision
.40
.35
.30
.25
Ankle
.20
.15
.10
Shoulder
.05
1
2
3
Practice Trials
Note: This is an approximation of your responses to show the pattern of response.
Electrical communication within the neuron
Myelin Sheath
(speeds transmission)
Axon
Nodes of Ranvier
Cell Body
Dendrites
(receivers)
Axon Terminals
(transmitters)
Electrical Transmission
Synapse
Chemical transmission
Electrical Transmission
Neuron 1
Neuron 2
Electrical Transmission – The Action Potential
At rest – Positive on the outside, negative on the inside
1. Action potential Sodium channels open - Positive sodium ions
surge in making the inside of the neuron positive
2. Positive potassium ions are forced out. Excess positive sodium ions
forced out. Stability returns
1.
(outside)
(inside)
2.
Sodium+
Sodium+ Potassium+
Potassium+
(outside)
(inside)
(See Gleitman, p. 68)
The action potential
Voltage change over time
Depolarization
+Sodium in adds to
+Potassium
Inside voltage (mV)
40
resting
potential
Positive outside
Negative inside
Polarized
Repolarization
+ Potassium out
20
0
-20
Hyperpolarization
+ Sodium out
-40
-60
Resting
+ Potassium back in
returns to positive
outside negative inside
-80
0
Stimulus onset
1
2
3
Time (milliseconds)
refractory period
4
5
Electrical Transmission
Synapse
Chemical transmission
Electrical Transmission
Neuron 1
Neuron 2
(See Gleitman, p. 72)
Axon of the
sending
neuron
Neural impulse
Axon terminal
Presynaptic
membrane
inding site
Postsynaptic
membrane
Synaptic
vesicle
Synapse
(Synaptic gap
or cleft)
Neurotransmitter
molecule
Receiving neuron
Chemical
Transmission
Electrical Transmission
Synapse
Chemical transmission
Electrical Transmission
Neuron 1
Summation
Neuron 2
Temporal summation:
several impulses from one source over time
Dendrites
Axon Hillock
Point of summation
Axon
Spatial summation:
several impulses from several
sources converging at the
same time