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nmdcat.online July 28, 2026

Among the following statements concerning the pacemaking abilities of muscle tissues, which is most accurate?

A. All skeletal muscles possess intrinsic myogenic pacemaker activity
B. Cardiac muscle contraction is entirely neurogenic and requires autonomic input
C. Some smooth muscles and all cardiac muscles can spontaneously generate action potentials
✓
D. Only cardiac muscle possesses specialized autorhythmic cells

📝 Explanation

Cardiac muscle is myogenic, possessing specialized pacemaker cells (like the SA node) that spontaneously generate action potentials. Certain types of single-unit smooth muscle (e.g., in the gut) also exhibit spontaneous pacemaker activity (slow waves). Skeletal muscle is entirely neurogenic.

📖 Additional Information

  • All skeletal muscles possess intrinsic myogenic pacemaker activity
  • Cardiac muscle contraction is entirely neurogenic and requires autonomic input
  • Some smooth muscles and all cardiac muscles can spontaneously generate action potentials
  • Only cardiac muscle possesses specialized autorhythmic cells

Cardiac muscle is myogenic, possessing specialized pacemaker cells (like the SA node) that spontaneously generate action potentials. Certain types of single-unit smooth muscle (e.g., in the gut) also exhibit spontaneous pacemaker activity (slow waves). Skeletal muscle is entirely neurogenic.

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