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nmdcat.online July 28, 2026

An increase in the concentration of acetylcholine at the neuromuscular junction typically stimulates skeletal muscle contraction. However, in the heart, acetylcholine release from the vagus nerve leads to:

A. Increased strength of ventricular contraction
B. Opening of sodium channels to speed up depolarization
C. Opening of potassium channels to hyperpolarize pacemaker cells
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D. Immediate tetanic contraction of the atria

📝 Explanation

Acetylcholine at the neuromuscular junction of skeletal muscle binds to nicotinic receptors to cause depolarization. In the heart, it binds to muscarinic receptors on pacemaker cells, opening potassium channels, which hyperpolarizes the cells and slows the heart rate.

📖 Additional Information

  • Increased strength of ventricular contraction
  • Opening of sodium channels to speed up depolarization
  • Opening of potassium channels to hyperpolarize pacemaker cells
  • Immediate tetanic contraction of the atria

Acetylcholine at the neuromuscular junction of skeletal muscle binds to nicotinic receptors to cause depolarization. In the heart, it binds to muscarinic receptors on pacemaker cells, opening potassium channels, which hyperpolarizes the cells and slows the heart rate.

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