Question

Heartbeats are accelerated by:

• A. Cranial nerves and acetylcholine
• B. Sympathetic nerves and acetylcholine
• C. Cranial nerves and adrenaline
• D. Sympathetic nerves and epinephrine

Answer 1

The correct option is D Sympathetic nerves and epinephrine

The involuntary actions are controlled by the autonomic nervous system by the sympathetic and parasympathetic chains. The sympathetic nerve chain accelerates the heartbeat during the fight, flight, or fear. Epinephrine, more commonly known as adrenaline is released by the adrenal medulla on activation by the sympathetic nerves into the bloodstream which increases heartbeat. It binds to the adrenergic receptors on the membrane of various organelles to regulate its function and secretion. For example, it attaches to the beta-adrenergic receptors of the heart and stimulates the SA node to increase the heart rate.

So, the correct answer is option D.