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myocyte
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Illustration of a human heart cross-section showing four chambers-left and right atria and ventricles-with labeled major blood vessels. An inset highlights cardiac muscle tissue, showing myocytes and intercalated disks.
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myocyte

physiology
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Illustration of a human heart cross-section showing four chambers-left and right atria and ventricles-with labeled major blood vessels. An inset highlights cardiac muscle tissue, showing myocytes and intercalated disks.
Human heart The human heart is both a pump and a muscle. Its four chambers move blood efficiently, while cardiac muscle cells joined by intercalated disks synchronize each contraction.

Myocyte refers to a muscle cell. In cardiac muscle, these cells, known as myocytes, are responsible for the heart's contractility and rhythmic contractions. The amount of blood pumped by the heart is determined by the contractile force of these myocytes and how frequently they are activated.12

The process of muscle contraction involves a complex interplay of electrical signals and chemical interactions. When a nerve impulse triggers an action potential at the muscle cell membrane (sarcolemma), this signal is transmitted internally. This leads to the release of calcium ions from the sarcoplasmic reticulum, a network within the cell. Calcium ions bind to proteins (troponin and tropomyosin) associated with actin filaments, removing an inhibition that allows actin and myosin filaments to interact. This interaction, fueled by ATP, generates force and causes muscle contraction. The sarcoplasmic reticulum then actively removes calcium ions, allowing the muscle to relax.342

Summary created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.
8 Britannica Sources
  1. muscle - Structure and organization
  2. sarcoplasmic reticulum
  3. hormone - Relationships between endocrine and neural regulation
  4. muscle disease - Mitochondrial myopathies
  5. muscle - Molecular mechanisms of contraction
  6. physiology - Regulation
  7. muscle disease - Myotonic diseases
  8. muscle - Excitation/contraction coupling

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