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
