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Action Potentials in the Sinoatrial (SA) Node

Why is the sinoatrial area of the heart known as a pacemaker? The sinoatrial node is a region of the heart that has the ability to generate to electrical signals similar to those produced by neurons. These signals are used to control the rate of contraction of different regions causing the entire heart to work in unison and for the contractions to occur at a constant rate. In this way the sinoatrial node sets the pace of the heart and is known as the pacemaker region.

View the animation below, then complete the quiz to test your knowledge of the concept.






1The sinoatrial node membrane potential peaks when...
A)the membrane sodium channels open slightly.
B)the membrane sodium channels open wide.
C)calcium flows into the intracellular fluid.
D)potassium flows out of the intracellular fluid.
E)calcium flows into the intracellular fluid and potassium trickles out of the intracellular fluid.



2During the initiation of repolarization...
A)the membrane sodium channels open slightly.
B)the membrane sodium channels open wide.
C)calcium flows into the intracellular fluid.
D)potassium flows out of the intracellular fluid.
E)calcium flows into the intracellular fluid and potassium trickles out of the intracellular fluid.



3The sinoatrial node muscle fibers maintain a continual permeability to...
A)calcium ions.
B)sodium ions.
C)potassium ions.
D)calcium and potassium ions.
E)calcium and sodium ions.



4The duration of a SA node action potential averages 0.30 seconds.
A)True
B)False



5The sinoatrial node has a 0.15 second recovery period between action potentials.
A)True
B)False







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