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Microscopic Anatomy of Heart Muscle

Microscopic Anatomy of Heart Muscle. Cardiac Muscle Contraction. Heart muscle: Is stimulated by nerves and is self-excitable (automaticity) Contracts as a unit Has a long (250 ms) absolute refractory period Cardiac muscle contraction is similar to skeletal muscle contraction.

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Microscopic Anatomy of Heart Muscle

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  1. Microscopic Anatomy of Heart Muscle

  2. Cardiac Muscle Contraction • Heart muscle: • Is stimulated by nerves and is self-excitable (automaticity) • Contracts as a unit • Has a long (250 ms) absolute refractory period • Cardiac muscle contraction is similar to skeletal muscle contraction

  3. Heart Physiology: Intrinsic Conduction System • Autorhythmic cells: • Initiate action potentials • Have unstable resting potentials called pacemaker potentials

  4. Heart Physiology: Sequence of Excitation

  5. Heart Physiology: Sequence of Excitation • Sinoatrial (SA) node generates impulses about 75 times/minute • Atrioventricular (AV) node delays the impulse approximately 0.1 second • Impulse passes from atria to ventricles via the atrioventricular bundle (bundle of His)

  6. Heart Physiology: Sequence of Excitation • AV bundle splits into two pathways in the interventricular septum (bundle branches) • Bundle branches carry the impulse toward the apex of the heart • Purkinje fibers carry the impulse to the heart apex and ventricular walls

  7. Heart Excitation

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