HP-05 NEET CHEAT SHEET — Locomotion and Movement
MUSCLE TYPES (3 KEY DISTINCTIONS)
SKELETAL SMOOTH CARDIAC
Striations: YES NO YES ← KEY TRAP
Voluntary: YES NO NO ← KEY TRAP
Nuclei: Multi(peri) Uni(central) Uni(central)
Special: T-tubules,SR Caveolae Intercalated discs
Fatigue: Readily Resistant NEVER
SARCOMERE BANDS — THE MOST TESTED CONCEPT
| Band/Zone | Contains | During Contraction |
|---|---|---|
| A band (DARK) | Myosin + overlapping actin | CONSTANT (always) |
| I band (LIGHT) | Actin ONLY | DECREASES |
| H zone | Myosin ONLY | DECREASES (may vanish) |
| Sarcomere | Everything | DECREASES (Z-lines closer) |
| Filament lengths | — | UNCHANGED (neither shortens) |
SLIDING FILAMENT — CRITICAL SEQUENCE
Nerve impulse → ACh → Action potential → T-tubules → Ca2+ from SR → Troponin-C → Tropomyosin shifts → Cross-bridge → Power stroke → ATP binds (detach) → ATP hydrolysis (re-cock) → Repeat
TWO ATP ROLES:
- ATP hydrolysis = RE-ENERGIZE myosin head
- ATP binding = DETACH myosin from actin
NO ATP = RIGOR MORTIS
SKELETON COUNTS (MEMORIZE)
- TOTAL = 206 (axial 80 + appendicular 126)
- AXIAL (80): Skull 22 + Vertebrae 26 + Ribs 24 + Sternum 1 + Hyoid 1
- VERTEBRAE (26): C7 + T12 + L5 + S1 + Cx1
- RIBS (24 = 12 pairs): 7 true + 3 false + 2 floating
- HYOID = only non-articulating bone
JOINT TYPES (6 SYNOVIAL — MUST KNOW ALL)
| Type | Example | Movement |
|---|---|---|
| Hinge | Knee, elbow | Uniaxial |
| Pivot | Atlas-axis (C1-C2) | Rotation only |
| Ball-and-socket | Shoulder, hip | All planes + rotation |
| Gliding | Intercarpal | Sliding, multiple planes |
| Saddle | Thumb CMC | Biaxial (no rotation) |
| Ellipsoid | Wrist | Biaxial (no rotation) |
FIBROUS = skull sutures (immovable) CARTILAGINOUS = pubic symphysis, intervertebral discs (slightly movable)
DISORDERS — CAUSE + KEY FEATURE
| Disorder | Cause | Key Feature |
|---|---|---|
| Myasthenia gravis | Autoimmune → ACh-R destruction | Skeletal weakness; worsens with use |
| Muscular dystrophy | Genetic: X-linked dystrophin | Progressive skeletal muscle loss |
| Tetany | Hypocalcemia | Involuntary sustained spasms |
| Osteoarthritis | Wear-and-tear cartilage | Weight-bearing joints; elderly |
| Rheumatoid arthritis | Autoimmune → synovial membrane | Symmetric joints; morning stiffness |
| Osteoporosis | ↓ bone density (↑ osteoclasts) | Post-menopausal; fragility fractures |
| Gout | Uric acid crystals | Big toe; acute; purine-rich diet |
TOP 5 NEET TRAPS
- A band = CONSTANT (NOT decreasing during contraction)
- Cardiac = striated + INVOLUNTARY (not voluntary like skeletal)
- ACh receptor destroyed = MYASTHENIA GRAVIS (not muscular dystrophy)
- ATP BINDING = detachment; ATP HYDROLYSIS = re-energize
- Wrist = ELLIPSOID joint (not ball-and-socket)