Muscle System Revision Sheet

1. 📌 Essentials

• The muscular system enables movement, posture, stabilization, and heat generation.
• Composed of skeletal, cardiac, and smooth muscle tissues.
• Muscle tissues exhibit excitability, contractility, extensibility, and elasticity.
• Sarcomeres are the functional contractile units within muscle fibers.
• Myofilaments (actin and myosin) slide past each other during.
• ATP energy for cross-bridge cycling; produced via cellular respiration.
• Muscle fatigue results from ATP depletion, oxygen debt, and lactic acid buildup.
• Tendons connect muscles to bones; origin is less movable, insertion is more movable.
• Muscles work in pairs: prime mover (agonist) and antagonist.
• Major muscles are named based on size, shape, location, origin, and function.

2. 🧩 Key Structures & Components

• Skeletal muscle — voluntary, striated, multinucleated.
• Cardiac muscle — involuntary, striated, branched.
• Smooth muscle — involuntary, nonstriated, spindle-shaped.
• Muscle fibers — long, cylindrical cells with multiple nuclei.
• Myofibrils — rod-like structures within fibers, composed of sarcomeres.
• Sarcomeres — repeating units of actin and myosin filaments.
• Epimysium — outer connective tissue covering entire muscle.
• Perimysium — surrounds fascicles (muscle bundles).
• Endomysium — surrounds individual muscle fibers.
• Tendons — connect muscles to bones.

---