1. Propagation of the action potential
Day 15 – Quick Notes
Propagation of the action potential

2. Conduction Speed (Saltatory Conduction)
The speed of an action potential increases with the axon’s diameter
In vertebrates, axons are myelinated, also causing an action potential’s speed to increase
Action potentials in myelinated axons jump between the nodes of Ranvier in a process called saltatory conduction

3. When an action potential reaches a terminal, the final result is release of neurotransmitters into the synaptic cleft
Postsynaptic
neuron
Synaptic
terminals
of pre-
synaptic
neurons
5 µm

4. A Chemical Synapse

5. Neurotransmitters Excite and Inhibit
Effect of neurotransmitter can be
excitatory postsynaptic potential (EPSP)
inhibitory postsynaptic potential (IPSP)
Numerous EPSPs can raise the membrane potential to the threshold level and result in an action potential

6. Neurotransmitters: Acetylcholine: excitatory to skeletal muscles
Epinephrine and Norepinephrine: increase metabolism
Dopamine: affects sleep, mood, attention, learning; Parkinson’s disease is associated with a lack of dopamine in the brain; schizophrenia is associated with an excess
Seratonin: affects sleep, mood, attention, learning; psychoactive drugs (LSD) binds to serotonin and dopamine receptors in the brain
GABA: inhibitory in brain, produces IPSPs
Endorphins: analgesics

7. Try these links at home…
Nerve Impulse Animation
Mad, Mad, Mad Neuron
Mouse Party
HMWK: Write one paragraph about a chosen mouse. Explain
the drug taken by the mouse
Neurotransmitters involved
Action of drug
Summary illustration