Anatomy and Physiology
What this domain tests
The Anatomy and Physiology domain asks you to link structure with movement: muscle contraction, joint actions, proprioception, cardiorespiratory control, and endocrine response. Exam items often require the prime mover, the plane and axis of a movement, or the receptor behind a reflex.
Core rules and concepts
- Muscle hierarchy: epimysium, perimysium, endomysium; fascicle, fiber, myofibril, sarcomere. A sarcomere runs Z line to Z line and contains actin thin filaments and myosin thick filaments.
- Sliding filament: calcium binds troponin, tropomyosin shifts, myosin cross-bridges attach; ATP powers detachment and calcium reuptake.
- Fiber types: type I is slow, oxidative, fatigue-resistant; type IIa is fast, oxidative-glycolytic; type IIx is fast, glycolytic, fatigable.
- Proprioceptors: muscle spindles detect stretch and rate of stretch and drive the stretch reflex; Golgi tendon organs detect tension and inhibit muscle action (autogenic inhibition).
- Joint motion: sagittal plane flexion/extension; frontal plane abduction/adduction; transverse plane rotation. Planes pair with perpendicular axes.
- Cardiopulmonary: right heart sends blood to lungs, left heart to body; SA node is the pacemaker, AV node delays; cardiac output = heart rate × stroke volume.
- Autonomic and endocrine: sympathetic raises heart rate and redirects blood flow; parasympathetic lowers it; insulin stores fuel, glucagon and cortisol mobilize it.
Worked example
A client performs a dumbbell biceps curl. The elbow flexes in the sagittal plane about a frontal axis. Biceps brachii and brachialis are agonists; triceps brachii is the antagonist. The biceps is a third-class lever because the muscle effort inserts between the elbow axis and the hand load. If the forearm is suddenly pushed toward extension, biceps muscle spindles detect the stretch and trigger a stretch reflex.
Traps that cost marks
Do not name a muscle without its joint action; do not confuse spindle (stretch) with Golgi tendon organ (tension); do not assign pulmonary circulation to the left ventricle; do not treat 220 − age as an anatomical fact; and do not say a muscle 'lengthens' during a concentric action.