Exam2 AP

Main functions of muscles?

Movement, posture, joint stabilization, and heat generation.

Three types of muscle tissue?

Skeletal (voluntary, striated), Cardiac (involuntary, striated), Smooth (involuntary, non-striated).

Muscle connective tissue layers?

Epimysium (whole muscle), Perimysium (fascicle), Endomysium (fiber).

Functional unit of muscle?

Sarcomere.

Proteins in sarcomere?

Actin, Myosin, Troponin, Tropomyosin.

Neuromuscular junction?

Synapse where motor neuron releases acetylcholine to stimulate the muscle fiber.

Excitation-contraction coupling?

Action potential → Ca²⁺ release → binding to troponin → contraction.

Calcium's role in contraction?

Binds to troponin to expose actin binding sites.

ATP's role in contraction?

Powers myosin movement and detachment.

Rigor mortis cause?

No ATP after death → myosin stays bound to actin → stiffness.

Phases of a muscle twitch?

Latent, Contraction, Relaxation.

Recruitment?

Increasing number of active motor units for stronger contraction.

Tetanus?

Continuous contraction with no relaxation (max stimulation).

Isotonic vs isometric?

Isotonic = length changes; Isometric = tension only, no movement.

Muscle tone?

Slight constant contraction maintaining posture.

Hypertrophy vs atrophy?

Hypertrophy = muscle growth; Atrophy = muscle loss.

Energy sources for muscle?

Creatine phosphate, anaerobic glycolysis, aerobic respiration.

Aerobic vs anaerobic respiration?

Aerobic: uses O₂ (36 ATP); Anaerobic: no O₂ (2 ATP + lactic acid).

Muscle fatigue?

When ATP is low or lactic acid accumulates → reduced contraction.

Endurance?

Ability to sustain long-term activity (improves with training and O₂ use).

Slow-twitch fibers?

Red, slow oxidative, endurance, aerobic, many mitochondria/myoglobin.

Fast-twitch fibers?

White, fast glycolytic, powerful, fatigue quickly, anaerobic.

Intermediate fibers?

Fast oxidative, mixed aerobic/anaerobic metabolism, moderate fatigue resistance.