Human Physiology – Action Potential Overview

Human Physiology – Action Potential Overview


>>Eric: Brain freeze! [music starts]>>Dr. Ketchum: [rapping] Do you ever think
about how your brain works? Billions of neur-ons, wearing not a tie or a shirt. Never taking
time off, whether you’re asleep or awake. Always open like a leak channel, that’s
the one with no gate!>>Reid: Sodium moves in while potassium moves
out. Membrane potential—reaching threshold is what it’s all about. Initiation at the
hillock, an action potential begins. All-or-none principle, save amplitude till the end.>>Dr. Ketchum: Sodium channel activation,
rapid depolarization. Positive feedback lend the perfect explanation.>>Reid: I know it doesn’t sound as fun,
but don’t forget about potassium. When a positive leaves the cell, we see a repolarization.>>Dr. Ketchum: Jumping from node to node,
traveling myelin sheath to sheath. At the end of the axon, the terminal is what we’ll
reach.>>Reid: Unidirectional propagation—yeah,
it’s a one-way street. No going back the other way, absolute refractor period is what
you’ll meet.>>Dr. Ketchum: Some people may say that you
can’t fire again. Hold that thought and I’ll introduce you to a friend. Oh wait!
Did I say friend?>>Reid: What she meant was relative. A second
refractory period overcome by a larger stimulus.>>Dr. Ketchum: Once it’s reached the terminal
bouton, the job isn’t done yet! Released neurotransmitter must travel across the synaptic
cleft.>>Reid: Postsynaptic dendrites are its target
destination, in hopes of carrying this message to you—[all together] enjoy neural communication!

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