3. CARDIAC MUSCLE OBJECTIVES
At the end of this lecture you should be able to know types of cardiac muscle and its anatomical location.
Arrangement of myofilaments and sarcoplasmic reticulum
Steps involved in Contraction
Functional differences

4. CARDIAC MUSCLES Cardiac muscle is found only in heart.
Shape = Rectangular shape.Short branched cells
Diameter = 20um Length = 100 um
Single nucleus
Regeneration of cardiac muscle fiber is controversial.Recent studies suggest that cardiac muscle cells have mild proliferative property.

6. Cardiac muscle Thick myosin filaments.
Thin actin filaments (Troponin present)
Striated appearance.
T-Tubule system associated with calcium loaded sarcoplasmic retculum.
Contraction occurs by sliding filament mechanism.

7. Intercalated Disks Structures between adjacent cells.
Myofibrils attached to desmosomes.
Gap junctions present.

10. Input influencing Cardiac muscle contractile activity.
1. Sinoatrial node (SA node-Pacemaker) Location=Superior posterolateral wall of right atrium. Hormones. Neurotransmitters

12. EXCITATION CONTRACTION COUPLING IN CARDIAC MUSCLE

14. Sources of Cytosolic Calcium
L-Type calcium channels (modified DPR)
(L= long lasting current )—Cardiac muscle cannot under go tetanic contractions.
ECF calcium
1.Depolarization of plasma membrane.
2.Slight Increase in cytosolic Ca
3.Triggers release of Ca from SR.
Rynaodine receptors (Ca channels)

15. Thin filament activation
Cross- bridge cycling
Force generation
Same as SKELETAL MUSCLE

16. Action Potential in Cardiac Muscle.

17. Steps involved in contraction of Cardiac muscle

19. Contraction ends
Cytosolic Ca conc is restored
Ca-ATPase pumps
Na/Ca countertranspoters

20. Contraction ends
Cytosolic Ca conc is restored.
Ca-ATPase activity
Na/Ca countertranspoters