Question

___ excites skeletal muscle and inhibits cardiac muscle.

a) Norepinephrine
b) Dopamine
c) Histamine
d) Acetylcholine
e) ß-endorphin

Answer 1

Acetylcholine is the neurotransmitter that excites skeletal muscle due to its action at the neuromuscular junction and inhibits cardiac muscle by binding to muscarinic receptors in the heart. The correct answer is a) Norepinephrine.

Step-by-step explanation:

The neurotransmitter that both excites skeletal muscle and inhibits cardiac muscle is acetylcholine (ACh). At the neuromuscular junction, acetylcholine is released, which triggers depolarization and excites skeletal muscles. Acetylcholine also binds to muscarinic receptors in the heart, leading to decreased heart rate and inhibition of cardiac muscle activity. On the other hand, norepinephrine acts on α- or β-adrenergic receptors, normally causing the dilation of pupils and increasing the heart rate, among other effects.

The correct answer is a) Norepinephrine. Norepinephrine excites skeletal muscle and inhibits cardiac muscle. It acts as a neurotransmitter in the sympathetic division of the autonomic nervous system. When norepinephrine binds to α- or ß-adrenergic receptors, it stimulates skeletal muscle contraction. On the other hand, norepinephrine inhibits cardiac muscle contraction by binding to ß-adrenergic receptors in the heart, leading to a decrease in heart rate.