Action Potentials

Resting Membrane Potential (labeled)

#1 and #4 in this diagram

typical resting membrane potential of a neuron

-70 mV

typical resting membrane potential of a cardiac muscle cell

-90mV

Na+/K+ pump mechanism

3 Na+ ions are pumped out of the cell for every 2 K+ ions pumped in.

Resting Membrane Potential (labeled)

A in this diagram (the dashed line indicates the point at which depolarization takes off!)

action potential fails to initiate (labeled)

C in this diagram - indicates situations in which the stimulus was NOT high enough to stimulate an action potential

Cause of hyperpolarization

Excess K+ leaves the cell, beyond what is necessary to bring the cell back to its resting membrane potential

Ion responsible for repolarization of a neuron or muscle cell

K+

Ion responsible for depolarization of a neuron or muscle cell

Na+

maintains the resting membrane potential of cells

Na+/K+ ATPase pump function

repolarization

Period during which potassium ions diffuse out of the neuron and it returns to a polarized state

hyperpolarization phase

Roman Numeral V in this diagram

Restore the Na+ and the K+ back to their resting positions in which Na+ is far more concentrated outside of the cell and K+ is more concentrated inside the cell?

The Na+/K+ ATPase pump function after an action potential

hyperpolarization

The movement of the membrane potential of a cell away from rest potential in a more negative direction.

depolarization

The process during the action potential when sodium is rushing into the cell causing the interior to become more positive.

action potential

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

relative refractory period

a stronger than usual stimulus is necessary to initiate an action potential

Is the Na+/K+ ATPase pump active or passive transport?

active (requires ATP!!) - it is pumping AGAINST the concentration gradient

Another action potential animation

https://youtu.be/-h_kWFM2faQ

Action Potential Animation

https://youtu.be/b2ctEsGEpe0

Is K+ movement during repolarization active or passive?

passive - moving down its concentration gradient

Is Na+ movement during depolarization active or passive?

passive - moving down its concentration gradient

Purpose of hyperpolarization

prevents the neuron from firing again too quickly

graded potentials

small changes in membrane potential that by themselves are insufficient to trigger an action potential

threshold

the level of stimulation required to trigger a neural impulse

action potential propagation

the movement of an action potential along an axon; in myelinated axons, it occurs via saltatory conduction

saltatory conduction

the propagation of action potentials along myelinated axons from one node of Ranvier to the next node, increasing the conduction velocity of action potentials.

absolute refractory period

time during which another action potential is impossible; limits maximal firing rate