Levick’s Introduction to Cardiovascular Physiology 6th edition (2018) [PDF] download
Levick’s Introduction to Cardiovascular Physiology 6th edition (2018) [PDF] download action potentials a. Depolarization makes the membrane potential less negative (the cell interior becomes less negative).
b. Hyperpolarization makes the membrane potential more negative (the cell interior becomes more negative).
c. Inward current is the flow of positive charge into the cell. Inward current depolarizes the membrane potential.
d. outward current is the flow of positive charge out of the cell. Outward current hyperpolarizes the membrane potential.
e. action potential is a property of excitable cells (i.e., nerve, muscle) that consists of a rapid depolarization, or upstroke, followed by repolarization of the membrane potential.
Action potentials have stereotypical size and shape, are propagating, and are all-or-none.
f. Threshold is the membrane potential at which the action potential is inevitable. At
threshold potential, net inward current becomes larger than net outward current.
The resulting depolarization becomes self-sustaining and gives rise to the upstroke of
the action potential. If net inward current is less than net outward current, no action
potential will occur (i.e., all-or-none response).
2. Ionic basis of the nerve action potential (Figure 1.6)
a. resting membrane potential
■ is approximately −70 mV, cell negative.
■ is the result of the high resting conductance to K+, which drives the membrane potential toward the K+ equilibrium potential.
■ At rest, the Na+ channels are closed and Na+ conductance is low.