Anatomy muscular system exam

4 primary characteristics of muscle tissue?

Excitability, Contractility, Extensibility, and Elasticity.

Structural hierarchy of a muscle?

Tendon -> Whole Muscle -> Fascicle -> Muscle Fiber -> Myofibril -> Myofilaments.

Functional unit of muscle contraction?

The Sarcomere.

What allows a muscle to contract?

Interaction between actin and myosin, powered by ATP and triggered by Calcium.

Sliding Filament Model definition?

Thin (actin) filaments slide past thick (myosin) filaments without changing length.

4 steps of Cross-Bridge Cycle?

1. Formation, 2. Power stroke, 3. Detachment, 4. Reactivation.

Role of Myosin?

The motor that pulls actin filaments toward the center of the sarcomere.

Role of Actin?

The track/rope that myosin pulls on to create tension.

Ions used in muscle contraction?

Calcium (Ca2+) for triggering and Magnesium (Mg2+) for relaxation/ATP.

Where is Calcium stored?

Sarcoplasmic Reticulum (SR).

Role of Calcium?

Binds to Troponin to move Tropomyosin away from binding sites.

Role of ATP?

Provides energy for the power stroke and allows myosin to detach (relax).

What is a Motor Unit?

One motor neuron and all the muscle fibers it innervates.

Factors affecting force?

1. Recruitment, 2. Stimulation frequency, 3. Initial muscle length.

Creatine Phosphate (Energy)?

1 ATP per CP; used for short bursts (0–15s).

Anaerobic Glycolysis (Energy)?

2 ATP + Lactic acid; used for high intensity (30–60s).

Aerobic Respiration (Energy)?

~32 ATP; used for sustained, moderate activity.

Muscle aging after 30?

Sarcopenia (1–2% loss per year); countered by resistance training.

Resistance vs. Endurance?

Resistance: Increases fiber size. Endurance: Increases mitochondria/capillaries.

Cause of Muscle Fatigue?

Ion imbalances or ATP depletion. (Lactic acid is NOT the cause).

Recovery: Fast/Explosive?

Needs nervous system rest and PCr replenishment.

Recovery: Moderate/Sustained?

Needs glycogen (carbs) and tissue repair.