Membrane Potential Flashcards
What are excitable cells?
Cells capable of generating action potentials on stimulation including neurons and muscles
Give the definition of an action potential
A short-lasting event in which the electrical membrane potential of a cell rapidly rises and falls
What is membrane potential?
The difference in voltage between the interior and exterior of a cell
what is electrochemical equilibrium?
A combination of the voltage gradient and the concentration gradient of an ion
What drives the flow of any ion through a membrane channel protein?
The electrochemical gradient for that ion
What is equilibrium potential?
The membrane potential at which there is no net flow of the ion, can be calculated by the Nerst equation
What determines the resting membrane potential?
Potassium, because resting channels in animal cells are selective for potassium only
Define depolarization
Making the membrane potential less negative, the cell interior becomes less negative
What is depolarization dependent on?
Inward current of positive charges
Define hyperpolarization
Makes the membrane potential more negative, the cell interior becomes more negative
What is hyperpolarization dependent on?
The outward current of positive charges
What are some properties of action potentials?
Stereotypical size and shape, propagating, all or nothing
Describe upstroke of an action potential
Upon stimulation, inward current depolarizes the membrane to threshold causing rapid opening of Na+ channels but does not reach the Na+ equilibrium potential (65mV)
Describe repolarization of an action potential
Repolarization is the combined effect of Na+ channels closing and K+ channels opening
What is undershoot/hyperpolarization?
The K+ channel conductance remains higher than at rest a while making it approach the K+ equilibrium potential