The process by which an action potential in the plasma membrane ...

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The process by which an action potential in the plasma membrane of a myocardial cell triggers the events that directly cause contraction of the myocardial cells is referred to as:
 
  a. electrocontraction.
  b. intercalated communication.
  c. excitation-contraction coupling.
  d. myosin communication.

Question 2

One difference between cardiac muscle and skeletal muscle is that:
 
  a. cardiac muscle cells are arranged in branching networks.
  b. skeletal muscle cells have only one nucle-us.
  c. cardiac muscle cells appear striped.
  d. skeletal muscle cells contain sarcomeres.

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Answer to Question 1

ANS: C
Excitation-contraction coupling, not electrocontraction, is the process by which an action poten-tial in the plasma membrane of the muscle fiber triggers the cycle, leading to cross-bridge activity and contraction. Neither intercalated nor myosin communication is associated with leading to cross-bridge activity and contraction.

Answer to Question 2

ANS: A
Cardiac cells are arranged in branching networks throughout the myocardium, whereas skeletal muscle cells tend to be arranged in parallel units throughout the length of the muscle. Cardiac muscle cells have only one nucleus, whereas skeletal muscle cells have many nuclei. Both cardiac and muscle cells appear striped and contain sarcomeres.

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