Question

Select all that apply

Which chemical messenger(s) increase heart rate?
a) Norepinephrine
b) Acetycholine
c) Epinephrine

Answer 1

Norepinephrine and epinephrine are the chemical messengers that increase heart rate. They work by binding to beta-1 receptors, contributing to the fight-or-flight response. Acetylcholine is not involved in increasing heart rate.

Step-by-step explanation:

The chemical messengers that increase heart rate are norepinephrine and epinephrine. Norepinephrine and epinephrine are catecholamines released by the adrenal medulla. They bind to beta-1 receptors on the heart, causing an increased rate of depolarization and a shortened period of repolarization, which leads to an increased heart rate. Norepinephrine also dilates the pupil and epinephrine increases blood pressure, but both contribute to the physiological changes associated with a fight-or-flight response.

Acetylcholine, on the other hand, typically has the opposite effect and is not a correct answer in this context because it is known to decrease heart rate by its action on the parasympathetic nervous system.