Resting Membrane and Action Potentials Flashcards
What is primarily responsible for the RMP?
potassium leak channels (permeability to K+)
RMP cardiac and skeletal muscle
-80 to -90 mV
RMP smooth muscle
-60 mV
RMP neuron
-60 to -70 mV
Equilibrium potential (E-ion)
membrane potential when electrical and chemical forces are equal; no further movement occurs
NOT EQUAL TO RMP
Nernst Equation
61.5/z(charge) + (log [X-out])/ (log [X-in])
Driving force equation
RMP - E-ion
if larger ion concentration outside cell
log is +
if larger ion concentration inside cell
log is -
takes into account all ion concentrations and permeability
Goldman equation
depolarization
MP becomes less negative (action potential)
hyperpolarization
MP becomes more negative
Repolarization
MP returns to resting MP
increase in permeability of membrane to Na+ via Voltage-gated Na+ channels
depolarization
Voltage-gated Na+ channels
open rapidly, delay, and then close automatically to stop other ions entering the cell
***inactivation gate closes, not permitting ions to pass
Voltage-gated K+ channels
not leak channels; turn on at peak AP and filter K+ out selectively; stay on too long leading to hyperpolarization
Voltage-gated Na+ channels reset; activation closes and inactivation gate opens
hyperpolarization
Absolute refractory period
Na+ channels are open or inactivation gate is closed and cannot open; NO AP can be generated
Relative refractory period
inactivation gate is open and the activation gate is closed; K+ permeability still high so hyper polarized cell; not all voltage gated Na+ channels are on same level; AP CAN BE INITIATED BUT NEED STRONGER STIMULUS
