Action potential Flashcards
(9 cards)
What is an action potential?
A sequence of changes in the membrane potential that occurs when an excitable cell is stimulated
Action potentials are critical for the functioning of neurons and muscle cells.
Define depolarization in the context of cardiac muscle.
The process of discharging resting cardiac muscle fibers by means of an electrical impulse that stimulates contraction
Depolarization is essential for initiating muscle contractions in the heart.
What role do chemical pumps play in myocardial cells?
They maintain the ion concentration within the cell, creating an electrical gradient across the cell membrane
This gradient is vital for the generation of action potentials.
What is the typical net internal charge of a resting (polarized) cell?
−90 millivolts (mV) relative to the outside of the cell
This negative charge is crucial for the cell’s ability to generate action potentials.
What happens to the cell wall when it is stimulated?
The cell wall becomes more permeable as specialized channels open, allowing sodium ions (Na+) to rush into the cell
This influx of sodium ions is a key component of depolarization.
How does the reversal of the cell’s electrical charge occur?
It begins at one point in the cell wall and spreads in a wave until the cell has been completely depolarized
This wave-like propagation is essential for coordinated muscle contraction.
What initiates repolarization in a cell?
Repolarization begins as the sodium and calcium channels close
This marks the transition back to a resting state.
Which channels open during repolarization?
Special potassium channels
The opening of these channels allows potassium ions (K+) to escape from the cell.
What is the effect of potassium ions escaping from the cell?
It restores a negative charge within the cell
This process is vital for returning the cell to its resting state after depolarization.
