L5: Action Potential

what is the resting membrane potential of a neuron?

-70mV

what floods in once threshold is met?

Na+ ions flood in through ion-gated channels, depolarization, turns off once peak is reached

what floods in once the peak of activation has occurred?

K+ ions flood out through K+ ion gated channels, called repolarization past the resting membrane potential

what happens during hyperpolarization?

only the sodium-potassium pump is active, trying to reach membrane potential again by pumping 3 Na+ out and 2 K+ in

What does the Nernst equation calculate?

It calculates what the equilibrium potential (the membrane potential at equilibrium) would be if one and only one ion were allowed to pass through the membrane.

so Na+ would prefer a positive potential, K+ would be very negative

accurately describe what's going on with the AP one ion at a time

where is action potential generated?

at the axon hillock

what is graded potential?

temporary, localized change in resting potential caused by stimulus, much faster than action potential

always how electrical stimulus travels, general state of being

1. graded, dissapates

2. fast

what is the electrical condition of depolarization?

-55mV is around what must be met to trigger action potential

what is action potential?

a neural impulse; a brief electrical charge that travels down an axon

1. all or none, either happens or doesn't

2. relatively slow

where does graded potential happen?

on the dendrites or soma cell body and the myelinated sheath

where does action potential happen?

on the unmyelinated sheath, travels down the axon as a graded potential and propagation allows the next section of the axon because it is still over threshold

if you were take a stimulating electrode and stimulate the axon, where does the action potential go?

it goes down the axon towards the terminal

how does the refractory period drive the action potential down the axon?

the Na+/K+ pumps follow the action potential to restore the resting membrane potential (hyper polarizing)

why does graded potential in the myelinated axon sheath force the action potential down the axon?

it pushes the action potential forwards on the nodes of Ranvier to speed up signaling and trigger another action potential

what are the benefits of myelin?

although it takes resources to build myelin, but it requires less energy to propagate a signal faster

what are volted gated calcium ion channels?

calcium comes into the cell at axon terminal, triggering the docking of vesicles and release of their contents into the synaptic cleft to find receptors