Action Potentials

what does it mean for a cell membrane to be polarized

the inside is negative compared to the outside

what two factors establish the resting membrane potential

• ion gradients

• selective membrane permeability

what 3 factors are the key players in maintaining the resting membrane potential

• Na/K ATPase

• K leak channels

• intracellular anionic protiens

At the peak of the action potential what happens to voltage gated Na and K channels

voltage gated Na channels close and voltage gated K channels open

a stimulus that does NOT bring the membrane to threshold will result in

no action potential

what structures make up and neuron

• axon

• dendritres

what does an axon do

transmits impulses away from the cell body

where are neuron cell bodies typically located

in the CNS

how do dendrite convert a chemical signal into an electrical one

nuerotransmitter binds a receptor → opens ion channels → creates an electrical signal

if a neuron has many dendrites recieveing input at once, what determine swhether an action potential fires

the combined effect of the inputs must change the overall charge enough to reach the threshold

what hapens when the action potential reaches the axon terminal

Ca centers the terminal triggering neurotransmitter release

depolarization

threshold reaches → voltage gated Na channels open → Na moves in → membrane becomes more positive

what ultimately resets the ion concetrations to baseline after repeated action potential

the Na/ K ATPase resets the sodium and potassium levels

why can lidocaine be used as a local anesthetic

it blocks voltage gated Na channels preventing AP generation/ propagation

ligand gated ion cahnnels open in response to

a chemical binding to the channel

chemical gradient

concentration difference

electrical gradient

attraction/ repulsion based on charge

overall flow from action potential to chemical communication

AP travels along axon → reaches terminal → Ca entry → neurotransmitter release → chemical communication with next cell

what happens to Na and the membrane when voltage gated Na channels first open

Na moves in and the membrane depolarizes

if myelin is lost, what happens to conduction

it decreases