Lecture 3.2 - The Action Potential

Within a cell: Electrical

Responding to an input , action potential is generated at the axon hillock
The signal is propagated won the length of the axon
When the action potential reaches the axon terminal, it produces exocytosis
Between Cells: Chemical
Neurochem diffuse away from the releasing axon
Neurochem interact with post synaptic receptors
With sufficient input, the post synaptic cell now produces an action potential of its own.
Intra- and extracellular fluid
energy comes from difference between
extraceullular fluid is similar to seawater interms of saltiness
intracellular fluid high in potassium
difference of electrical chagre across membrane of about 7 millivolts
intracelluar is relatively negative to exterior
diffusion pushes potasium out of cell from concentration gradient, but it is attracted to inside, leaving it at equilibrium.

works hard to keep sodium out
Explain concentrations of Sodium, Potassium, and Chloride
action potentials dont generate until substantial input
5-15 nmilivolts of input required
Sodium chennels open; Na+ rushes in
Potassium channels opem amd K+ starts to leave
Sodium channels become inactive
Potassium channels close.
Resting membrane potential is -70mV

Propagation: Unmyelinated Axon