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Cardiac Physiology: Chambers, Valves, and Muscle Cells

Explore the different chambers and valves of the heart, as well as the characteristics of cardiac muscle cells. Discover the role of autorhythmic cells and the excitation-contraction coupling process.

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Cardiac Physiology: Chambers, Valves, and Muscle Cells

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  1. Cardiac Physiology • The heart: chambers, the valves • Cardiac muscle cells • Some cardiac muscle cells are autorhythmic • Arrangement of cardiac muscle cells • Excitation-contraction coupling

  2. Atrioventricular (AV) Valves • guard the passageway between the atria and the ventricles • Tricuspid valve between right atrium and right ventricle • Bicuspid (mitral) valve between left atrium and left ventricle

  3. Semilunar valves • Between ventricles and arteries • Pulmonary valve between right ventricle and pulmonary artery • Aortic valve between left ventricle and aorta

  4. All myocardial cells • Gap junctions at intercalated discs, waves of depolarization spread from one cell to another

  5. Autorhythmic myocardial cells • (pacemakers) are small myocardial cells with few contractile fibers • Spontaneously generate action potentials • Enables the heart to contract without any outside signal • The heart is myogenic: signal for contraction originates from heart muscle itself

  6. Most myocardial cells • Remaining myocardial cells are striated • Have sarcomeres • Much smaller than skeletal muscle fibers • Connected by gap junctions at intercalated discs • Lots of mitochondria • Lots of blood flow to myocardial cells

  7. More facts about myocardial cells • Large branching t-tubules • Sparse sarcoplasmic reticulum • Source of Ca++ is largely extracellular

  8. Excitation-contraction coupling • Depolarization cell membrane voltage gated Ca++ channels open •  Ca++ enters cell •  calcium-induced calcium release: Ca++ released from SR •  Ca++ binds to troponin contraction

  9. Myocardial cell relaxation • Ca++ dissociates from troponin •  Ca++ returns to SR by Ca++ ATPase •  Ca++ also transported from cell by Na+-Ca++ indirect active transport protein: Ca++ is exchanged for Na+, which moves in along its electrochemical gradientNa+ removed by active transport

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