1.
CHARECTERISTICS OF CARDIAC
MUSCLE

2.
• The heart is composed of three major types of cardiac muscle:
• Atrial muscle
• Ventricular muscle
• Specialized excitatory and conductive muscle fibers
• Three layers viz. Epicardium , Myocardium and Endocardium

3.
• Show Striations and Involuntary
• Plasma membrane is called sarcolemma
• Sarco tubular system is different from skeletal muscle
• Presence of Intercalated discs which contains desmosomes and gap
junction.
• Functions as syncytium
• They have prolonged Action Potential and Plateau phase

4.
Cardiac Muscle Skeletal Muscle
Location of T tubules At Z line At A-I junction
Diameter of T tubules More less
L tubules Narrow tubular cistern
(Diad)
Large dialated cistern
(triad)

5.
The velocity of conduction of AP in both Atria and Ventricle is 0.3
to .05 m/s (1/10 of that of Skeletal muscle).

6.
• Calcium induced Calcium
release from sarcoplasmic
reticulum during excitation
contraction coupling.
• Does not show Tetany
• Has the property of Automatic
rhythmic discharge and
contraction

7.
Rhythmic Discharge of SA Node

8.
MYOCARDIAL ACTION POTENTIAL

9.
• Rapid depolarization (Phase 0) – due to Na+ influx
• Rapid Repolarization (Phase 1) - Due to closure of Na+ channels
• Slow depolarization (Phase 2) - this is called Plateau phase and is
maintained for 200 – 300 ms – due to Ca++ influx
• Repolarization (Phase 3) – due to K+ efflux
• Resting Membrane Potential (Phase 4)