The Heart Rate Decreases in Response to the Arrival Of

Question

The heart rate decreases in response to the arrival of
A) acetylcholine.
B) epinephrine.
C) endorphin.
D) nitric oxide.
E) GABA.

Accepted Answer

Acetylcholine is released by the parasympathetic nervous system and causes the heart rate to decrease.

Answer: B 
 Epinephrine is released by the sympathetic nervous system and causes the heart rate to increase.

Answer: C 
 Endorphins are opioids that can cause a decrease in pain perception, but they do not directly affect heart rate.

Answer: D 
 Nitric oxide is involved in vasodilation, but does not directly affect heart rate.

Answer: E 
 GABA is an inhibitory neurotransmitter in the brain, but does not directly affect heart rate.