Membrane Potentials and Action Potentials Flashcards
What establishes the resting membrane potential in a cell?
The resting membrane potential is established by the movement of ions across the cell membrane, particularly the higher concentration of K+ inside the cell and the lower concentration of Na+ inside relative to outside.
How does the sodium-potassium pump contribute to membrane potential?
The sodium-potassium pump moves 3 Na+ ions out of the cell and 2 K+ ions into the cell, helping to maintain the concentration gradients necessary for the resting membrane potential.
What is the role of potassium leak channels in resting membrane potential?
Potassium leak channels allow K+ ions to move out of the cell down their concentration gradient, leaving behind negatively charged anions and contributing to the negative resting membrane potential.
What is meant by the term “electrochemical gradient”?
The electrochemical gradient refers to the combined effect of the concentration gradient and the electrical gradient across the membrane, which leads to the potential difference (membrane potential) between the inside and outside of the cell.
What is the difference between membrane potential and resting potential?
Membrane potential is the voltage difference across the plasma membrane at any given time, while resting potential specifically refers to the membrane potential of a cell that is not actively sending signals.
What happens during depolarization?
During depolarization, the membrane potential becomes more positive than the resting potential, often due to the influx of Na+ ions when sodium channels open.
What is repolarization?
Repolarization is the process by which the membrane potential returns to the resting potential after depolarization, often involving the opening of potassium channels and the efflux of K+ ions.
What is hyperpolarization?
Hyperpolarization occurs when the membrane potential becomes more negative than the resting potential, often as a result of prolonged K+ ion efflux.
What is an action potential, and how is it triggered?
An action potential is a rapid change in membrane potential that occurs when sufficient depolarization raises the voltage above a certain threshold, leading to the propagation of an electrical impulse along the axon.
How does an action potential propagate along an axon?
An action potential propagates along an axon by causing sequential depolarization of adjacent membrane regions, allowing the electrical signal to travel rapidly.
What occurs at the synapse following an action potential?
At the synapse, the arrival of an action potential causes the release of neurotransmitters into the synaptic cleft, facilitating communication between neurons.
What are the stages of the cardiac action potential?
The stages of the cardiac action potential include:
Stage 0: Depolarization (sodium channels open).
Stage 1: Repolarization begins (sodium channels inactivate, potassium channels open).
Stage 2: Plateau phase (potassium channels remain open, calcium channels activate).
Stage 3: Repolarization (calcium channels close, potassium channels open).
Stage 4: Resting state (most sodium and potassium channels are closed).
Why is the plateau phase significant in cardiac action potentials?
The plateau phase in cardiac action potentials prolongs the depolarization, preventing tetany (sustained contraction) and allowing the heart to fill with blood before the next contraction.
How do gated ion channels influence changes in membrane potential?
Gated ion channels open or close in response to stimuli, allowing specific ions to flow in or out of the cell, leading to changes in membrane potential such as depolarization or hyperpolarization.
What ion primarily contributes to the negative resting membrane potential inside the cell?
The primary ion contributing to the negative resting membrane potential is potassium (K+), as it moves out of the cell, leaving behind negatively charged anions.
