PhysiologyLesson 1 of 2 in the course Muscle Tissue

Cardiac Muscle Cell Structure and Electrical Coordination

5 flashcards · 5 quiz questions · 5 match pairs · 5 fill-in sentences · English

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Summary

Cardiac muscle tissue is specialized to make the heart contract continuously and efficiently, pumping blood through the circulatory system. This lesson explores how cardiac muscle cells are built, how they communicate and stay connected, and how their electrical activity coordinates each heartbeat.

Cardiac muscle tissue is found only in the heart. Like skeletal muscle, it is striated and organized into sarcomeres, which give it a similar banding pattern. Cardiac muscle fibers, however, are generally shorter and more extensively branched than skeletal muscle fibers. Each cell usually has one centrally located nucleus.

All flashcards

What are the main structural features of a cardiac muscle cell?
Cardiac muscle cells are short, branched, striated, and organized into sarcomeres. They usually have one centrally located nucleus and contain many mitochondria and myoglobin.
What are the functions of gap junctions and desmosomes?
Gap junctions allow electrical current to pass between adjacent cardiac cells. Desmosomes mechanically anchor the cells so they do not pull apart during contraction.
What is a functional syncytium?
A group of electrically connected cardiac muscle cells that contracts in a coordinated manner as a functional unit.
What is autorhythmicity?
The ability of pacemaker cells to depolarize to threshold and generate action potentials without requiring a separate signal for each beat.
Why is calcium important to the cardiac muscle action potential and contraction?
Calcium entering through voltage-gated channels helps sustain the action-potential plateau and supports a longer contraction. A substantial portion of the calcium that initiates contraction comes from outside the cell.

Quiz questions

  1. Which anatomical site contains cardiac muscle tissue?Answer: The heart
  2. What structures organize cardiac muscle into repeating units that produce its striated pattern?Answer: Sarcomeres
  3. What do the abundant mitochondria and myoglobin in cardiac muscle help support?Answer: Aerobic ATP production
  4. How can the autonomic nervous system and hormones affect the heart?Answer: They can modulate heart rate.
  5. Which statement describes conscious control of cardiac muscle?Answer: Cardiac muscle is not consciously controlled.

Based on Anatomy and Physiology 2e by J. Gordon Betts, Kelly A. Young, James A. Wise, Eddie Johnson, Brandon Poe, Dean H. Kruse, Oksana Korol, Jody E. Johnson, Mark Womble, Peter DeSaix (OpenStax), licensed CC BY 4.0. Adapted into a summary, flashcards and quizzes.

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