which of the following statements concerning action potentials in the heart is correct

a. the rising phase of action potential in cardiac autorhythmic cells is due to a rising in Ca+

b.the rising phase of action potential in cardiac autorhythmic in cardiac contractile cells is due to a rapid Na+ influx

c. the plateau phase of the action potential in cardiac contractile cells is due to a slow Ca+ influx

d. both a nd c are correct

e. all of the above are correct

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Deanna HettingerLv2

28 Sep 2019

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What would be most strongly affected by a drug that inhibited the opening of voltage-gated potassium channels (also known as delayed rectifiers)?

A. Falling phase of an action potential

B. Rising phase of an action potential

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D. Threshold for an action potential

Why does the voltage during the undershoot phase of the action potential become more negative than the resting membrane potential?

A. During the undershoot potassium ions are flowing into the cell due to the reversal of the potassium concentration gradient occurring during the action potential

B. The undershoot phase results from a delay in the activation of sodium channels, resulting in some sodium channels being open after the voltage-gated potassium channels have closed. C. The potassium conductance is higher during the undershoot than during the resting membrane potential.

D. The concentration gradient for potassium has been reversed as a result of the action potential, and the undershoot phase lasts until this the concentration gradient is restored.

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A. While using dot points, briefly describe how a sphygmomanometer is used to measure blood pressure. Note: Focus on the action of the cuff on the vasculature of the arm to explain your point.

B. In 2 sentences, briefly describe how the sympathetic and parasympathetic nervous systems alter the rate of the SA node depolarisation.

C. In short, what two factors affect mean arterial blood pressure?

D. Why do humans have a plateau phase in the action potentials of the cardiomyocytes of the bundle of His, Purkinje Fibers and the Ventricular walls, that results in a large absolute refractory period?

E. What causes the plateau phase in the action potential of the cardiomyocytes reffered in D? (In other words: What is the closed or open status of the particular ion channel and what is the relevant ion responsible?)

F. Why is the 'Pacemaker' potential of the AV and SA node cardiomyocytes unstable? (i.e. what is the molecular basis of the said instability?)

G. What ions are responsible for the depolarization phase in (a) cardiomyocytes of the AV and SA nodes; and (b) the other cardiomyocytes?

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Answer the following and provide a BRIEF/SHORT explanation for each:

A. Why do humans have a plateau phase in the action potentials of the cardiomyocytes of the bundle of His, Purkinje Fibers and the Ventricular walls, that results in a large absolute refractory period?

B. What causes the plateau phase in the action potential of the cardiomyocytes reffered in A? (In other words: What is the closed or open status of the particular ion channel and what is the relevant ion responsible?)

C. While using dot points, briefly describe how a sphygmomanometer is used to measure blood pressure. Note: Focus on the action of the cuff on the vasculature of the arm to explain your point.

D. In 2 sentences, briefly describe how the sympathetic and parasympathetic nervous systems alter the rate of the SA node depolarisation.

E. Why is the 'Pacemaker' potential of the AV and SA node cardiomyocytes unstable? (i.e. what is the molecular basis of the said instability?)

F. What ions are responsible for the depolarization phase in (a) cardiomyocytes of the AV and SA nodes; and (b) the other cardiomyocytes?

G. In short, what two factors affect mean arterial blood pressure?