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General Properties of Cardiac Muscle

General Properties of Cardiac Muscle. Fig Heart. Fig 10-1. Fig Microscopic Structure of Cardiac Muscle. Fig 9-2. EM of muscle. FIg 24-2. Cardiac muscle. Atrial muscle Ventricular muscle Specialized excitatory and conductive muscle. Properties of myocardial cells.

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General Properties of Cardiac Muscle

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  1. General Properties of Cardiac Muscle

  2. Fig Heart • Fig 10-1

  3. Fig Microscopic Structure of Cardiac Muscle • Fig 9-2

  4. EM of muscle • FIg 24-2

  5. Cardiac muscle • Atrial muscle • Ventricular muscle • Specialized excitatory and conductive muscle

  6. Properties of myocardial cells • Automaticity (Chronotropic property) • Conductivity (Dromotropic property) • Contractivity (Inotropic property) • Excitability (Bathmotropic property)

  7. Fig automaticity • fig 10-2

  8. fig automaticity • FIg 23-7

  9. Automaticity (Chronotropic property) • Pacemaker cell • SA node, AV node and Purkinje fiber • Slow diastolic depolarization • Follower cell • bundle of His, ventricular muscle, et al. • Ion channels • Fast Na+ channel • Slow Ca2+-Na+ channel • K+ channel • Resting membrane potential (RMP) • Maximal diastolic potential (MDP) • Threshold potential (TP)

  10. Fig regulation of automaticity • handbook 167

  11. Regulation of Automaticity • Maximal diastolic potential • Decreased by acetylcohline • Rate of diastolic depolarization • Decreased by acetylcholine • Increased by norepinephrine • Threshold potential

  12. Fig Stannius ligature • page 5

  13. Conductivity(Dromotropic property) • Sinoatrial (SA) node • Internodal tract • Atrioventricular (AV) node • Bundle of His (AV bundle) • Bundle branches (left and right) • Purkinje fiber • Ventricular muscle

  14. Sinoatrial (SA) node • Junction of superior vena cava and right atrium • 8 x 8 x 2 mm3 • Innervations of sympathetic nerve and parasympathetic nerve

  15. Internodal Tract • Anterior internodal tract • Bachmann`s bundle (to left atrium) • Middle internodal tract • Posterior internodal tract

  16. Fig internodal tract • Fig page 7

  17. Atrioventricular (AV) node • Interatrial septum, near coronary sinus • 22 x 10 x 3 mm3 • AV conduction delay • AN (upper; atrionodal zone) • N (middle zone of nodal cell) • NH (Lower; nodal-His zone)

  18. Fig AV node • Page 7

  19. AV node Slow channel Fast channel Automaticity Effect of (Ca2+-Na+ channel) (Na+ channel) Ca2+ blocker AN 60% 40% yes + N 80% 20% no ++ NH 60% 40% yes +

  20. Table conduction speed • table Ganong 28-1

  21. AV conduction delay • Allows time for the atria to emty their contents into ventricle • Smaller fiber diameter • Less intercalated disc • Poor differentiation • Regulated by sympathetic and parasympathetic nerves (negative and positive dromotropic effect)

  22. Fig Accessory pathway • page 10

  23. Fig Discharge of ventricular muscle • fig Gan 28-4

  24. Intercalated Disc • Cell membrane seperate but also connect cardiac muscle cells • Gap junction • Low resistance (5 ohm cm2 vs 2000 ohm cm2) • Functional syncytium

  25. Fig functional syncytium • Fig 11

  26. fig excitability • fig handbook 167

  27. Contractility (Inotropic property) • Ventricle, Ventricular muscle • Correlated to intracellular concentration of Ca2+ • Sympathetic stimulation • Inotropic drugs

  28. Fig inotropic property • Gan 29-8

  29. fig inotropic property • fig 24-5

  30. Excitability (Bathmotropic property) • Full recovery time (FRT) • Absolute refractory period (ARP) • Inactivation of fast Na+ channels • Relative refractory period (RRP) • Part of fast Na+ channels are recovered to resting stage • Supernormal period (SNP) • Most of fast Na+ channels are recovered • Higher membrane potential

  31. Fig excitability • Page 12+13

  32. Fig extrasystolic contraction • page 14

  33. Extrasystolic contraction • Premature contraction • Compensatory period • Extopic focus • Ischemia • Stimulants (Nicotine, Caffeine) • Lack of sleep • Stress, anxiety

  34. Cardiac Energetics Net energy change = disappearance of internal (chemical) energy = appearance of external energy (heat and work) Energy source of cardiac muscle Carbohydrate Non-carbohydrate Glucose 18% Fatty acid 67% Lactate 6% Amino acid 6 % Ketone 4 % Similar to red skeletal muscle

  35. Myocardial cells and autonomic nervous system Sympa. Para. Chronotropism (frequency) + - Dromotropism (conduction) + - Inotropism (contractility) + Bathmotropism (excitability) + -

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