Part 1: Types of Movement (Concepts 1-3)

Living organisms exhibit three fundamental movement types. Ciliary movement uses hair-like projections (cilia) to propel substances along epithelial surfaces — seen in the respiratory tract and fallopian tubes. Flagellar movement uses whip-like flagella for cellular propulsion — the classic example is sperm motility. Muscular movement is the most complex, involving the coordinated action of the entire musculoskeletal system. These three types are important for NEET because they appear in multiple chapters (reproductive biology for ciliary and flagellar, physiology for muscular).

Part 2: Types of Muscle (Concepts 4-12)

Three muscle types are testable. Skeletal muscle: striated, voluntary, multinucleated, cylindrical, fatigues readily, has well-developed T-tubules and SR. Smooth muscle: non-striated, involuntary, uninucleate (fusiform), found in visceral organ walls, resistant to fatigue, has caveolae instead of T-tubules. Cardiac muscle: striated (like skeletal) but involuntary (like smooth) — this contradiction is tested heavily. Additional cardiac features: intercalated discs (gap junctions + desmosomes), intrinsic rhythmicity, never fatigues, short branched cells, uni/binucleate. The combination of striation + involuntary control is unique to cardiac muscle and is a near-annual NEET question.

Part 3: Sarcomere Structure (Concepts 13-20)

The sarcomere (Z-line to Z-line) is the functional contractile unit. Key bands: A band (dark, myosin + actin, CONSTANT during contraction); I band (light, actin only, DECREASES); H zone (myosin only within A band, DECREASES); M-line (anchors myosin at H zone centre); Z-line (anchors actin, bisects I band, marks sarcomere boundary). The key NEET rule: A band is ALWAYS constant; I band and H zone decrease. The sarcomere shortens because actin slides over stationary myosin — neither filament changes length.

Part 4: Sliding Filament Theory (Concepts 21-30)

The molecular mechanism proceeds: motor nerve impulse → ACh at NMJ → action potential → T-tubules → Ca2+ from SR → troponin-C activation → tropomyosin shift → cross-bridge formation → power stroke → ATP binding (detachment) → ATP hydrolysis (re-energizing) → cycle repeats. Key regulatory proteins: troponin-C (Ca2+ sensor), tropomyosin (gate for actin-binding sites). ATP has two roles: hydrolysis re-energizes the myosin head; binding causes detachment. Without ATP: rigor mortis. SERCA pumps Ca2+ back into SR for relaxation (ATP-dependent).

Part 5: Skeletal System (Concepts 31-38)

Adult skeleton = 206 bones (axial 80 + appendicular 126). Axial = skull (22) + vertebrae (26: C7+T12+L5+S1+Cx1) + ribs (24: 7 true + 3 false + 2 floating pairs) + sternum (1) + hyoid (1, non-articulating). Appendicular = pectoral girdle + upper limbs + pelvic girdle + lower limbs. Hip bone = ilium + ischium + pubis (fused). Pelvic girdle more stable; pectoral girdle more mobile.

Part 6: Joints (Concepts 39-45)

Joints classified by tissue and mobility: fibrous (synarthrosis, skull sutures), cartilaginous (amphiarthrosis, pubic symphysis, intervertebral discs), synovial (diarthrosis, 6 subtypes). The six synovial subtypes with examples: hinge $\frac{knee}{elbow}$, pivot (atlas-axis), ball-and-socket $\frac{shoulder}{hip}$, gliding $\frac{intercarpal}{intertarsal}$, saddle (thumb CMC), ellipsoid (wrist). Each subtype has a specific range of motion from uniaxial (hinge, pivot) to multiaxial (ball-and-socket).

Part 7: Musculoskeletal Disorders (Concepts 46-53)

Seven disorders: myasthenia gravis (autoimmune ACh receptor destruction), muscular dystrophy (genetic X-linked dystrophin), tetany (hypocalcemia), osteoarthritis (degenerative), rheumatoid arthritis (autoimmune synovial membrane attack), osteoporosis (post-menopausal bone loss), gout (uric acid crystals in joints). NEET tests cause, mechanism, and distinguishing features. Key comparisons: RA (autoimmune, symmetric, young-middle age) vs OA (degenerative, asymmetric, elderly); myasthenia gravis (NMJ) vs muscular dystrophy (muscle fiber itself).