Which is true when your sympathetic nervous system is more active? A) The SA node depolarizes more rapidly. B) The myocardium repolarizes more rapidly. C) More Ca²⁺ becomes available and causes more forceful heart contractions. D) Norepinephrine is stimulating the heart. E) All of these.

Question

Quizplus · Accepted Answer

- A is true because the sympathetic nervous system activates the SA node to increase heart rate.
- B is false because the sympathetic nervous system does not affect the repolarization of the myocardium.
- C is true because the sympathetic nervous system releases more Ca2+ into the cytoplasm of cardiac muscle cells, leading to more forceful contractions.
- D is true because the sympathetic nervous system releases norepinephrine, which stimulates the heart.

Which Is True When Your Sympathetic Nervous System Is More