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Short Notes Locomotion and Movement - Short Notes for NEET
Types of Movement
1. Ciliary Movement
- Definition: Movement by coordinated beating of cilia
- Structure: Cilia - hair-like projections, 9+2 arrangement of microtubules
- Examples:
- Movement of mucus in respiratory tract
- Movement of ovum in fallopian tube
- Paramoecium locomotion
2. Flagellar Movement
- Definition: Movement by whip-like action of flagella
- Structure: Flagellum - long whip-like structure, 9+2 arrangement
- Examples:
- Sperm movement
- Euglena locomotion
3. Muscular Movement
- Definition: Movement by contraction and relaxation of muscles
- Most significant type in humans and higher animals
- Requires skeletal system for support and attachment
- Examples: Walking, running, breathing, heart beating
Types of Muscles
| Type | Structure | Location | Control | Features |
|---|---|---|---|---|
| Skeletal/Striated/Voluntary | • Cylindrical • Multinucleated • Striations present • Unbranched | Attached to bones | Voluntary (somatic nervous system) | • Fast contraction • Fatigue quickly |
| Smooth/Unstriated/Involuntary | • Spindle-shaped • Uninucleated • No striations • Unbranched | Internal organs (intestine, blood vessels) | Involuntary (ANS) | • Slow contraction • No fatigue |
| Cardiac | • Cylindrical • Uninucleated • Striations present • Branched with intercalated discs | Heart wall | Involuntary (intrinsic) | • Rhythmic contraction • No fatigue |
Skeletal Muscle Structure
- Muscle → Muscle Bundles (Fascicles) → Muscle Fibers → Myofibrils → Myofilaments
- Muscle fiber (cell):
- Multinucleated, syncytial
- Sarcolemma: Plasma membrane
- Sarcoplasm: Cytoplasm
- Sarcoplasmic reticulum: Endoplasmic reticulum (stores Ca²⁺)
- Myofibril:
- Contains contractile units called Sarcomeres
- Light and dark bands give striated appearance
Sarcomere - Functional Unit of Contraction
| Component | Description |
|---|---|
| Z-line (Z-disc) | • Boundaries of sarcomere • Thin elastic fibers |
| I-band (Isotropic) | • Light band • Contains only thin (actin) filaments • Bisected by Z-line |
| A-band (Anisotropic) | • Dark band • Contains thick (myosin) filaments • Length remains constant during contraction |
| H-zone | • Central part of A-band • Contains only thick filaments (no overlap) |
| M-line | • Middle of H-zone • Holds thick filaments together |
Contractile Proteins
Thin Filament (Actin)
- F-actin: Polymer of G-actin (globular) monomers, forms helical structure
- Tropomyosin: Protein that runs along F-actin groove
- Troponin:Complex of 3 proteins (I, T, C)
- Troponin I: Binds to actin
- Troponin T: Binds to tropomyosin
- Troponin C: Binds Ca²⁺ ions
- Active sites: On actin, normally masked by tropomyosin-troponin complex
Thick Filament (Myosin)
- Myosin II: Major protein
- Structure:
- Tail: Two heavy chains twisted together
- Head (Cross-bridge):Globular, projects outward
- Contains ATP-binding site
- Contains actin-binding site
- Has ATPase activity
- Arranged in bipolar manner with heads projecting at both ends
Mechanism of Muscle Contraction - Sliding Filament Theory
Steps of Contraction
| Step | Process |
|---|---|
| 1. Nerve Signal | • Motor neuron releases acetylcholine (ACh) at neuromuscular junction • ACh binds to receptors on sarcolemma • Generates action potential |
| 2. Excitation-Contraction Coupling | • Action potential travels along sarcolemma and T-tubules • Sarcoplasmic reticulum releases Ca²⁺ into sarcoplasm |
| 3. Ca²⁺ Binding | • Ca²⁺ binds to Troponin C • Troponin changes shape • Tropomyosin moves away, exposing active sites on actin |
| 4. Cross-Bridge Formation | • Myosin head (already has ADP+Pi) binds to actin active site • Forms acto-myosin complex |
| 5. Power Stroke | • Myosin head pivots, pulling actin filament toward M-line • ADP + Pi released • Thin filaments slide over thick filaments • I-band and H-zone shorten, A-band remains same |
| 6. Cross-Bridge Detachment | • New ATP binds to myosin head • Myosin detaches from actin |
| 7. Reactivation of Myosin | • ATP hydrolyzed to ADP+Pi by myosin ATPase • Myosin head returns to "cocked" position • Cycle repeats if Ca²⁺ still present |
| 8. Relaxation | • Neural signal stops • Ca²⁺ pumped back into sarcoplasmic reticulum • Tropomyosin covers active sites again • Muscle relaxes |
Key Points
- ATP required for: Cross-bridge detachment and Ca²⁺ pump
- Rigor mortis: After death, no ATP → permanent cross-bridges → muscle stiffness
- Red muscle fibers: More myoglobin (oxygen storage), aerobic, slow-twitch, fatigue-resistant (e.g., back muscles)
- White muscle fibers: Less myoglobin, anaerobic, fast-twitch, fatigue quickly (e.g., extraocular muscles)
Skeletal System - Functions
- Support: Framework for body
- Protection: Protects internal organs (skull-brain, ribcage-heart/lungs)
- Movement: Provides attachment for muscles, acts as levers
- Mineral storage: Stores calcium and phosphorus
- Blood cell formation: Red bone marrow produces RBCs, WBCs, platelets (hematopoiesis)
Types of Bones
| Type | Examples |
|---|---|
| Long bones | Humerus, femur, tibia |
| Short bones | Carpals, tarsals |
| Flat bones | Skull bones, sternum, ribs |
| Irregular bones | Vertebrae |
| Sesamoid bones | Patella (kneecap) |
Axial and Appendicular Skeleton
- Axial skeleton (80 bones): Skull, vertebral column, ribs, sternum
- Appendicular skeleton (126 bones):
- Limbs (upper and lower)
- Girdles (pectoral and pelvic)
- Total bones in adult human: 206
Joints (Articulations)
Classification by Structure and Function
| Type | Subtype | Movement | Examples |
|---|---|---|---|
| Fibrous Joints (Synarthroses) | Sutures | Immovable | Skull bones |
| Syndesmoses | Slightly movable | Tibia-fibula | |
| Gomphoses | Immovable | Teeth in sockets | |
| Cartilaginous Joints (Amphiarthroses) | - | Slightly movable | • Between vertebrae • Pubic symphysis |
| Synovial Joints (Diarthroses) | Ball and socket | Multiaxial (all movements) | Shoulder, hip |
| Hinge | Uniaxial (flexion-extension) | Elbow, knee | |
| Pivot | Uniaxial (rotation) | Atlas-axis (neck) | |
| Gliding | Slight movement in all directions | Between carpals, tarsals | |
| Saddle | Biaxial | Thumb (carpometacarpal) | |
| Condyloid | Biaxial | Wrist |
Synovial Joint Structure
- Articular cartilage: Covers bone ends, reduces friction
- Joint cavity: Space between bones
- Synovial membrane: Lines cavity, secretes synovial fluid
- Synovial fluid: Lubricates joint, nourishes cartilage
- Ligaments: Connect bone to bone, stabilize joint
- Articular capsule: Fibrous covering around joint
Disorders of Muscular and Skeletal System
1. Myasthenia Gravis
- Type: Autoimmune neuromuscular disorder
- Cause: Antibodies against acetylcholine receptors at neuromuscular junction
- Symptoms:
- Progressive muscle weakness
- Fatigue with repetitive use
- Drooping eyelids (ptosis)
- Double vision (diplopia)
- Difficulty swallowing and speaking
- Treatment: Acetylcholinesterase inhibitors, immunosuppressants
2. Tetany
- Cause: Low blood calcium levels (hypocalcemia) - often due to hypoparathyroidism
- Symptoms:
- Rapid, involuntary muscle spasms and contractions
- Painful cramps
- Carpopedal spasm (hands and feet)
- Tetany of larynx (can be fatal)
- Note: Different from tetanus (bacterial infection causing muscle rigidity)
3. Muscular Dystrophy
- Type: Group of genetic disorders
- Cause: Mutation in genes coding for muscle proteins (mainly dystrophin)
- Most common type:Duchenne Muscular Dystrophy (DMD)
- X-linked recessive
- Affects males primarily
- Symptoms:
- Progressive muscle degeneration and weakness
- Begins in childhood
- Difficulty walking, frequent falls
- Calf muscle pseudohypertrophy
- Eventually affects heart and respiratory muscles
- Prognosis: No cure, progressive disorder
4. Arthritis
- Definition: Inflammation of joints
- Types:
- Osteoarthritis:
- Degenerative joint disease
- Wear and tear of articular cartilage
- Common in elderly
- Affects weight-bearing joints (knee, hip)
- Rheumatoid Arthritis:
- Autoimmune disorder
- Inflammation of synovial membrane
- Affects multiple joints symmetrically
- Joint deformity
- Osteoarthritis:
- Symptoms: Pain, stiffness, swelling, reduced range of motion
5. Osteoporosis
- Definition: Decreased bone mass and density
- Cause:Imbalance between bone resorption and formation
- Decreased estrogen (post-menopause in women)
- Calcium/Vitamin D deficiency
- Aging
- Inactivity
- Symptoms:
- Bones become porous, brittle, fragile
- Increased fracture risk (especially hip, spine, wrist)
- Loss of height
- Stooped posture (kyphosis)
- Prevention: Adequate calcium/Vitamin D, weight-bearing exercise, hormone therapy
6. Gout (Gouty Arthritis)
- Cause: Accumulation of uric acid crystals in joints
- Reason:Hyperuricemia (elevated blood uric acid) due to:
- Excessive production of uric acid
- Decreased excretion by kidneys
- High purine diet (red meat, seafood, alcohol)
- Symptoms:
- Sudden, severe joint pain (often big toe - podagra)
- Inflammation, swelling, redness
- Recurrent attacks
- Formation of tophi (uric acid deposits)
- Treatment: Anti-inflammatory drugs, uric acid-lowering drugs, dietary modification
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FAQs on Short Notes Locomotion and Movement - Short Notes for NEET
| 1. What is locomotion? |  |
Ans. Locomotion refers to the movement of an organism from one place to another. It involves various physical activities and mechanisms that allow animals and humans to travel through their environment, such as walking, running, swimming, and flying.
| 2. What are the types of locomotion in animals? | |
Ans. Animals exhibit several types of locomotion, including: 1. <b>Amoeboid movement</b>: Seen in amoeba, where the organism changes shape to move. 2. <b>Ciliary movement</b>: Utilised by organisms like Paramecium, which use hair-like structures called cilia for movement. 3. <b>Muscular movement</b>: Common in vertebrates, where muscles contract and relax to facilitate movement. 4. <b>Jet propulsion</b>: Observed in cephalopods like squids, which expel water to propel themselves.
| 3. What role do joints play in locomotion? | |
Ans. Joints are crucial in locomotion as they connect bones and allow for movement. They provide flexibility and enable various types of movements, such as bending and rotation. Different types of joints, like hinge joints (e.g., knees) and ball-and-socket joints (e.g., shoulders), facilitate specific movements essential for locomotion.
| 4. How does muscle contraction contribute to movement? | |
Ans. Muscle contraction is a key mechanism in movement. Muscles work in pairs: when one muscle contracts, the opposing muscle relaxes. This coordinated action allows for the movement of bones at joints. The sliding filament theory explains that muscle fibres shorten during contraction due to the sliding of actin and myosin filaments past each other, generating force.
| 5. What is the significance of the skeletal system in locomotion? | |
Ans. The skeletal system provides structure and support to the body, allowing for efficient locomotion. It serves as an anchor for muscles, enabling them to exert force for movement. Additionally, the skeleton protects vital organs and plays a role in the production of blood cells within the bone marrow, which is essential for overall health and mobility.
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