Which of the following mechanisms play(s)a role in regulating heart rate?
A)chemical messengers in the blood,such as epinephrine
B)nerves originating from the medulla (lower part of the brain)
C)pacemaker cells within the heart
D)chemical messengers in the blood,such as epinephrine;nerves originating from the medulla (lower part of the brain);and pacemaker cells within the heart
E)chemical messengers in the blood,such as epinephrine,and pacemaker cells within the heart

Question

Quizplus · Accepted Answer

All of the mechanisms listed play a role in regulating heart rate. Chemical messengers in the blood, such as epinephrine, can bind to specific receptors on the heart muscle and either increase or decrease heart rate. Nerves originating from the medulla in the brain can send signals to the heart to increase or decrease heart rate. Pacemaker cells within the heart are specialized cells that initiate the electrical signals that cause the heart to contract, and the rate at which these cells fire can also regulate heart rate. Therefore, the correct answer is D.

Which of the Following Mechanisms Play(s)a Role in Regulating Heart