Locomotion and Movement Class 11 Chapter 20 Notes PDF - NEET 2027

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Free NEET Notes for Chapter 20: Locomotion and Movement 🔥

✅ 3 Types of Muscles

✅ Sliding Filament Theory 

✅ 206 Bones + Types of Joints

✅ NEET High Yield Points + Disorders

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### *1. Types of Movement in Animals*

1. *Amoeboid Movement*: By pseudopodia. Ex: Amoeba, Macrophages, WBCs. Uses actin microfilaments

2. *Ciliary Movement*: By cilia. Ex: Paramecium, lining of trachea, oviduct

3. *Flagellar Movement*: By flagella. Ex: Sperm, Euglena, Chlamydomonas

4. *Muscular Movement*: By skeletal muscles. Most advanced. Helps in locomotion

### *2. Human Muscular System - 3 Types*

Feature Skeletal Muscle Smooth Muscle Cardiac Muscle

**Location** Attached to bones Hollow organs, blood vessels Heart wall only

**Control** Voluntary Involuntary Involuntary

**Striations** Present Absent Present

**Shape** Cylindrical, unbranched Spindle shaped Branched

**Nuclei** Multinucleated, peripheral Uninucleated, central Uninucleated, central

**Intercalated discs** Absent Absent Present

*Properties of Muscle*: Excitability, Contractility, Extensibility, Elasticity, Conductivity

### *3. Ultrastructure of Skeletal Muscle*

*Hierarchy*: Muscle → Fascicles → Muscle Fiber → Myofibrils → Sarcomeres

1. *Sarcolemma*: Plasma membrane of muscle fiber

2. *Sarcoplasm*: Cytoplasm with glycogen, myoglobin

3. *Sarcoplasmic Reticulum*: Stores Ca²⁺ ions. Releases during contraction

4. *T-tubules*: Transverse tubules. Conduct nerve impulse inside

*Myofibril*: Has alternate dark *A-band* and light *I-band*

- *A-band*: Anisotropic. Contains thick + thin filaments. Middle has *H-zone*

- *I-band*: Isotropic. Contains only thin filaments. Middle has *Z-line*

- *Sarcomere*: Segment between 2 Z-lines. *Functional unit of contraction*

*Protein Filaments:*

- *Thick filament*: Myosin. Head has ATPase + binding site for actin

- *Thin filament*: Actin + Tropomyosin + Troponin

- *Troponin*: 3 subunits. *TnC* binds Ca²⁺

### *4. Sliding Filament Theory - Detailed*

*Events of Muscle Contraction:*

1. *Stimulus*: Motor neuron releases *Acetylcholine* at NMJ

2. *Action potential* generated in sarcolemma → Travels via T-tubules

3. *Ca²⁺ release* from SR → Ca²⁺ binds to *TnC of Troponin*

4. *Conformational change*: Tropomyosin shifts → Myosin binding site on actin exposed

5. *Cross-bridge formation*: Myosin head binds to actin using ATP

6. *Power stroke*: ADP + Pi released → Myosin pulls actin → Sarcomere shortens

7. *Detachment*: New ATP binds to myosin → Cross-bridge breaks

8. *Relaxation*: Ca²⁺ pumped back to SR by active transport

*During Contraction*: I-band + H-zone shorten. A-band length remains constant

*Rigor mortis*: After death, no ATP → Cross-bridges cannot break → Muscles become stiff

### *5. Types of Muscle Fibers*

Feature Red Fiber / Slow Oxidative White Fiber / Fast Glycolytic

**Myoglobin** High Low

**Mitochondria** Many Few

**Blood supply** Rich Less

**Contraction** Slow, sustained Fast, fatigues quickly

**Metabolism** Aerobic Anaerobic

**Example** Postural muscles Eye muscles

### *6. Skeletal System - 206 Bones*

*A. Axial Skeleton = 80 bones*

- *Skull*: 22 bones. Cranial: 8, Facial: 14

- *Ear ossicles*: 6 - Malleus, Incus, Stapes

- *Hyoid*: 1 - U-shaped, does not articulate with any bone

- *Vertebral column*: 26 bones. Formula: C7 T12 L5 S1 Coccyx1

- *Ribs*: 24. 1st 7 = True ribs, 8-10 = False, 11-12 = Floating

- *Sternum*: 1

*B. Appendicular Skeleton = 126 bones*

- *Pectoral girdle*: 4 - 2 Clavicle + 2 Scapula. Glenoid cavity articulates with humerus

- *Upper limbs*: 60

- *Pelvic girdle*: 2 Coxal bones. Each = Ilium + Ischium + Pubis. Acetabulum articulates with femur

- *Lower limbs*: 60

### *7. Joints - Classification*

1. *Fibrous*: Immovable. Dense fibrous tissue. Ex: Sutures of skull, tooth in socket

2. *Cartilaginous*: Slightly movable. Hyaline/fibrous cartilage. Ex: Pubic symphysis, IV discs

3. *Synovial*: Freely movable. Has synovial cavity + fluid + articular cartilage

*Types of Synovial Joints:*

- *Ball & Socket*: Shoulder, Hip - Movement in all 3 axes

- *Hinge*: Elbow, Knee, Ankle - Movement in 1 axis

- *Pivot*: Atlas-Axis, Radio-ulna - Rotation only

- *Gliding*: Intercarpal, Intertarsal - Sliding movement

- *Saddle*: Carpometacarpal of thumb - Movement in 2 axes

- *Ellipsoid/Condyloid*: Wrist - Movement in 2 axes

### *8. Disorders - NEET Favorites*

1. *Myasthenia gravis*: Autoimmune. Antibodies destroy ACh receptors → Muscle fatigue

2. *Muscular dystrophy*: X-linked recessive. Dystrophin protein missing → Progressive muscle degeneration

3. *Tetany*: Low plasma Ca²⁺ → Rapid muscle spasms

4. *Arthritis*: 

   - *Rheumatoid*: Autoimmune, inflamed synovial membrane

   - *Osteoarthritis*: Age related, cartilage degeneration

5. *Osteoporosis*: Low bone mass. Due to estrogen deficiency, Ca²⁺ deficiency

6. *Gout*: Uric acid crystal deposition in joints. Painful

7. *Sprain*: Ligament damage

8. *Dislocation*: Displacement of bone from joint

### *9. Extra NEET High Yield Points*

- *Neuromuscular Junction*: Synapse between motor neuron and muscle fiber

- *Motor unit*: 1 motor neuron + all muscle fibers it innervates

- *Oxygen debt*: Accumulation of lactic acid due to anaerobic respiration

- *Calmodulin*: Ca²⁺ binding protein in smooth muscle contraction

- *Coracoid process*: Part of pectoral girdle

Revise this + NCERT diagrams once. *Sarcomere, Joint types, Skeleton* are most important for NEET 💯