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

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

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

A Chemical Synapse

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

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

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