NEET Bio — Locomotion and Movement

Chapter Overview & Weightage

Locomotion and Movement is part of the Class 11 Human Physiology unit. It contributes typically 3-4 marks in NEET (1-2 questions out of 90 in Biology). Memory-heavy chapter, but content is well-bounded — almost everything tested is in NCERT.

Key Concepts You Must Know

Prioritized by NEET frequency:

Types of muscles — skeletal (striated, voluntary), smooth (non-striated, involuntary), cardiac (striated, involuntary).
Structure of skeletal muscle — fascicle, fibre, myofibril, sarcomere. Light bands (I), dark bands (A), Z-line, M-line, H-zone.
Sliding filament theory — actin and myosin interaction, role of $Ca^{2+}$ , ATP, troponin, tropomyosin.
Skeletal system — axial skeleton (80 bones: skull, vertebral column, ribs, sternum) vs appendicular (126 bones: limbs and girdles). Total = 206.
Joints — fibrous (immovable), cartilaginous (slightly movable), synovial (freely movable). Types of synovial: hinge, ball-and-socket, pivot, gliding, saddle.
Disorders — myasthenia gravis, muscular dystrophy, tetany, arthritis, osteoporosis, gout.

Important Numbers to Memorise

Total bones in adult human: 206 Axial skeleton: 80 (skull 22, hyoid 1, vertebrae 26, ribs 24, sternum 1, ear ossicles 6) Appendicular skeleton: 126 (each limb 30, pelvic girdle 2, pectoral girdle 4)

Skeletal muscle is ~80% water, with proteins: actin, myosin, troponin, tropomyosin. Each myosin filament has ~6 actin filaments around it (in cross-section). Sarcomere: A-band length ~1.6 μm, I-band variable.

Solved Previous Year Questions

PYQ 1 (NEET 2024)

What is the role of $Ca^{2+}$ in muscle contraction?

Solution: When a muscle is stimulated, $Ca^{2+}$ is released from the sarcoplasmic reticulum. $Ca^{2+}$ binds to troponin C, causing tropomyosin to shift away from the actin’s myosin-binding sites. Myosin heads then attach to actin and pull (with ATP hydrolysis), causing contraction.

PYQ 2 (NEET 2023)

How many bones are present in the human vertebral column of an adult?

Solution: 26 bones — 7 cervical, 12 thoracic, 5 lumbar, 1 sacrum (5 fused), 1 coccyx (4 fused).

PYQ 3 (NEET 2022)

Which of the following changes occur in a sarcomere during muscle contraction? (a) H-zone disappears (b) A-band shortens (c) I-band shortens (d) Both (a) and (c)

Solution: During contraction, A-band length stays the same (it’s the length of myosin), but I-band and H-zone shrink as actin filaments slide over myosin. So (d) both (a) and (c) is correct.

Difficulty Distribution

Easy: ~50% — bone counts, muscle types, basic structure
Medium: ~40% — sliding filament theory, joint types
Hard: ~10% — molecular details ( $Ca^{2+}$ pathway, troponin subunits)

Expert Strategy

Strategy 1: NCERT diagrams cold. Sarcomere structure (with bands and zones), elbow joint (hinge), shoulder (ball-and-socket). Practice sketching them.

Strategy 2: Memorise bone counts by region. Skull 22, vertebrae 26, ribs 24, etc. NEET often asks for specific subregions.

Strategy 3: Master the contraction cycle. $Ca^{2+}$ release → troponin binding → tropomyosin shift → myosin attaches → power stroke (ATP hydrolysed) → release → repeat. Six steps to remember.

NEET 2024 included a tricky question on the order of events in muscle contraction. Memorise the sequence; out-of-order answers lose 4 marks plus negative marking.

Common Traps

Trap 1: Saying A-band shortens during contraction. Wrong — A-band is the myosin filament length, which is constant. Only the I-band and H-zone shrink.

Trap 2: Forgetting cardiac muscle is involuntary. Cardiac muscle is striated (like skeletal) but involuntary (like smooth). Unique combination.

Trap 3: Confusing types of arthritis. Osteoarthritis (wear-and-tear), rheumatoid (autoimmune), gouty (uric acid crystals). NEET tests these distinctions.

Trap 4: Misremembering total bones as 213 or 200. Adult human: 206. Children have more (some bones fuse during growth).

Locomotion and Movement is a guaranteed-marks chapter for NEET if NCERT is read carefully. The content is finite and predictable — high ROI per study hour.