The phase of the action potential that accounts for the generation and propagation of impulses by the heart without external stimulation is the automaticity or pacemaker potential phase. This is primarily seen in the sinoatrial node (SA node) and the atrioventricular node (AV node) of the heart.

Here are the steps:

1. The pacemaker cells in the SA node have an unstable resting potential that continuously depolarizes, drifting towards the threshold for an action potential. This is known as the pacemaker potential.

2. When the membrane potential reaches the threshold, voltage-gated calcium channels open. The resulting influx of calcium ions causes the depolarization phase of the action potential.

3. After the cell depolarizes, potassium channels open, allowing outflow of potassium ions, which causes repolarization and returns the membrane potential to its resting state.

4. The cycle then repeats, with the pacemaker potential gradually depolarizing until it reaches the threshold and triggers another action potential.

This automaticity of the heart's pacemaker cells allows the heart to generate and propagate its own electrical impulses without external stimulation.

Question

The phase of the action potential that accounts for the generation and propagation of impulses by the heart without external stimulation is the automaticity or pacemaker potential phase. This is primarily seen in the sinoatrial node (SA node) and the atrioventricular node (AV node) of the heart.

Here are the steps:

1. The pacemaker cells in the SA node have an unstable resting potential that continuously depolarizes, drifting towards the threshold for an action potential. This is known as the pacemaker potential.

2. When the membrane potential reaches the threshold, voltage-gated calcium channels open. The resulting influx of calcium ions causes the depolarization phase of the action potential.

3. After the cell depolarizes, potassium channels open, allowing outflow of potassium ions, which causes repolarization and returns the membrane potential to its resting state.

4. The cycle then repeats, with the pacemaker potential gradually depolarizing until it reaches the threshold and triggers another action potential.

This automaticity of the heart's pacemaker cells allows the heart to generate and propagate its own electrical impulses without external stimulation.

Knowee AI · Accepted Answer

The phase of the action potential that accounts for the generation and propagation of impulses by the heart without external stimulation is the automaticity or pacemaker potential phase. This is primarily seen in the sinoatrial node (SA node) and the atrioventricular node (AV node) of the heart.

Here are the steps:

1. The pacemaker cells in the SA node have an unstable resting potential that continuously depolarizes, drifting towards the threshold for an action potential. This is known as the pacemaker potential.

2. When the membrane potential reaches the threshold, voltage-gated calcium channels open. The resulting influx of calcium ions causes the depolarization phase of the action potential.

3. After the cell depolarizes, potassium channels open, allowing outflow of potassium ions, which causes repolarization and returns the membrane potential to its resting state.

4. The cycle then repeats, with the pacemaker potential gradually depolarizing until it reaches the threshold and triggers another action potential.

This automaticity of the heart's pacemaker cells allows the heart to generate and propagate its own electrical impulses without external stimulation.

00. Which phase(s) of the action potential accounts for thegeneration and propagation of impulses by the heart withoutexternal stimulation?CABAll

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