Anatomy and Physiology
Orientation and terminology
Anatomical position - standing, palms forward, feet parallel - is the reference for every directional term: superior/inferior, proximal/distal (toward or away from the trunk), medial/lateral, anterior/posterior, superficial/deep. Nerve traffic follows the same logic: afferent fibers arrive at the CNS carrying sensory input; efferent fibers exit carrying motor commands. Item writers swap these two constantly.
Muscle and joint anatomy
Muscle → fascicles → fibers → myofibrils → sarcomeres. Inside the sarcomere, actin (thin) and myosin (thick) filaments slide past one another - the sliding-filament theory - driven by ATP and calcium released from the sarcoplasmic reticulum. Type I fibers are slow-twitch, oxidative, and fatigue-resistant; Type II fibers are fast, glycolytic, powerful, and fatigable. The origin is the more proximal, relatively fixed attachment; the insertion is distal and moves. Synovial joints permit the greatest range of motion; fibrous and cartilaginous joints permit little.
System integration
Cardiac output = heart rate × stroke volume and drives oxygen delivery; alveolar gas exchange loads the blood; the nervous system recruits motor units smallest-first, the size principle.
Traps and a rule of thumb
Muscle spindles sense stretch and trigger contraction of the stretched muscle; Golgi tendon organs sense tension and trigger relaxation. Questions also blur agonist/antagonist and origin/insertion. Rule of thumb: “Afferent Arrives, Efferent Exits.” Apply it to the patellar reflex: tapping the tendon stretches the quadriceps, the spindle fires an afferent signal to the spinal cord, and an efferent signal returns to contract the quadriceps.