Cardiac Muscle vs Skeletal Muscle

SKELETAL MUSCLE FIBER

1. ​Striated muscle, actin, and myosin filaments are arranged in sarcomeres.
2. Well-developed sarcoplasmic reticulum and transverse tubules.
3. Contains troponin in thin filaments.
4. Nerve stimulation required for contraction, gap junctions are absent.

CARDIAC MUSCLE

1. ​Striated muscle, actin, and myosin filaments are arranged in sarcomeres.
2. Moderately developed sarcoplasmic reticulum and transverse tubules.
3. Contains troponin in thin filaments.
4. Action potentials will be generated in pacemaker cells and spreads via gap junctions.

SMOOTH MUSCLE

1. Non-striated, more actin than myosin
2. Poorly developed sarcoplasmic reticulum. No transverse tubules.
3. Contain calmodulin (binds to calcium and activates myosin). Nitric oxide (nitroglycerine) binds myosin-light chain phosphatase and relaxes venous smooth muscle.
4. Visceral smooth muscle produces action potentials and current spreads via gap junction.

To review any cardiac condition, just search on google followed by 'medrx education'. For example: Atrial fibrillation medrx education. You can also review all up-to-date material in our book "Fundamentals of Cardiology".

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Adapted from: Fundamentals of Cardiology: Concise Review for USMLE and General Medical Boards
To review any cardiac condition, just search on google followed by 'medrx education'. For example: Atrial fibrillation medrx education. You can also review all up-to-date materials in our book "Fundamentals of Cardiology".

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