Locomotion and Movement Exercise Solutions | KalviGavani

| Feature | Skeletal | Smooth | Cardiac | |---|---|---|---| | Shape | Long, cylindrical | Spindle-shaped | Branched, cylindrical | | Striation | Present | Absent | Present (faint) | | Nuclei | Multinucleate | Uninucleate | Uninucleate | | Control | Voluntary | Involuntary | Involuntary | | Location | Attached to bones | Hollow organs | Heart wall | | Special | — | — | Intercalated discs |

The sliding filament theory states that during muscle contraction, the thin filaments (actin) slide over the thick filaments (myosin) toward the centre of the sarcomere. The filaments themselves don't shorten — the overlap between actin and myosin increases. This shortens the I-band and H-zone, while the A-band remains the same length, resulting in overall sarcomere shortening and muscle contraction.

1. Fibrous joints (immovable): Skull sutures — bones are held together by fibrous tissue 2. Cartilaginous joints (slightly movable): Intervertebral discs — bones are held together by cartilage 3. Synovial joints (freely movable): Knee, elbow, shoulder — bones are separated by a fluid-filled cavity

Osteoporosis is a condition in which bone density decreases, making bones porous, weak, and prone to fractures. It is caused by: - Decreased oestrogen levels (post-menopausal women) - Calcium and vitamin D deficiency - Lack of exercise - Ageing Prevention: Adequate calcium and vitamin D intake, regular exercise, hormone replacement therapy.

Sliding Filament Theory: During muscle contraction, the thin filaments (actin) slide over the thick filaments (myosin) toward the centre of the sarcomere. The filaments themselves do not shorten — the overlap between them increases. Changes during contraction: - I-band: Shortens (thin filaments only) - H-zone: Shortens (thick filaments only in centre) - A-band: Remains the same length (full length of myosin) - Sarcomere: Shortens overall Steps of Muscle Contraction: 1. Neural signal: Motor neuron releases acetylcholine (ACh) at the neuromuscular junction. ACh binds to receptors on the muscle fibre, generating an action potential. 2. Calcium release: The action potential travels along the muscle fibre membrane (sarcolemma) and into T-tubules, triggering the release of Ca²⁺ from the sarcoplasmic reticulum. 3. Cross-bridge formation: Ca²⁺ binds to troponin on the thin filament. This causes tropomyosin to shift, exposing the myosin-binding sites on actin. Myosin heads bind to actin, forming cross-bridges. 4. Power stroke: The myosin head pivots, pulling the thin filament toward the centre of the sarcomere. This uses energy from ATP hydrolysis. 5. Detachment: A new ATP molecule binds to the myosin head, causing it to detach from actin. 6. Recovery stroke: The myosin head returns to its original position (cocked state), using energy from ATP hydrolysis, ready for the next cycle. 7. Relaxation: When the neural signal stops, Ca²⁺ is pumped back into the sarcoplasmic reticulum (requires ATP). Tropomyosin covers the binding sites again, and the muscle relaxes.

Axial Skeleton (80 bones): 1. Skull (29 bones): - Cranial bones: 8 (1 frontal, 2 parietal, 2 temporal, 1 occipital, 1 sphenoid, 1 ethmoid) - Facial bones: 14 (2 maxilla, 2 zygomatic, 2 nasal, 2 palatine, 2 lacrimal, 2 inferior nasal conchae, 1 mandible, 1 vomer) - Ear ossicles: 6 (2 malleus, 2 incus, 2 stapes) - Hyoid bone: 1 (in the neck, not attached to any other bone) 2. Vertebral Column (26 bones): - Cervical vertebrae: 7 (neck) - Thoracic vertebrae: 12 (chest) - Lumbar vertebrae: 5 (lower back) - Sacrum: 1 (fused) - Coccyx: 1 (fused) 3. Rib Cage (25 bones): - 12 pairs of ribs (24 ribs) - 1 sternum (breastbone) - True ribs: Pairs 1-7 (directly attached to sternum) - False ribs: Pairs 8-10 (indirectly attached to sternum) - Floating ribs: Pairs 11-12 (not attached to sternum) Appendicular Skeleton (126 bones): 1. Pectoral Girdle (4 bones): - 2 clavicles (collar bones) - 2 scapulae (shoulder blades) 2. Upper Limbs (60 bones): - 2 humerus (upper arm) - 2 radius + 2 ulna (forearm) - 16 carpal bones (wrist) - 10 metacarpal bones (palm) - 28 phalanges (fingers) 3. Pelvic Girdle (2 bones): - 2 hip bones (each made of ilium, ischium, pubis) 4. Lower Limbs (60 bones): - 2 femur (thigh bone — longest bone) - 2 patella (kneecap) - 2 tibia + 2 fibula (lower leg) - 14 tarsal bones (ankle) - 10 metatarsal bones (sole) - 28 phalanges (toes)

Types of Joints: 1. Fibrous Joints (Immovable): - Bones are held together by fibrous tissue - No joint cavity - No movement - Examples: Skull sutures, teeth in sockets 2. Cartilaginous Joints (Slightly Movable): - Bones are held together by cartilage - Slight movement possible - Examples: Intervertebral discs (between vertebrae), pubic symphysis, costochondral joints (ribs to sternum) 3. Synovial Joints (Freely Movable): - Bones are separated by a fluid-filled synovial cavity - Synovial fluid lubricates the joint - Articular cartilage covers the bone ends - Most common type of joint in the body Types of Synovial Joints: - Ball-and-socket: Shoulder, hip — movement in all directions - Hinge: Elbow, knee, ankle — movement in one plane - Pivot: Atlas-axis (neck rotation) — rotation around one axis - Gliding: Between vertebrae, wrist bones — sliding movement - Saddle: Thumb (carpometacarpal) — movement in two planes - Condyloid: Wrist (radiocarpal) — movement in two planes (not rotation) Joint Disorders: 1. Osteoporosis: - Decreased bone density → fragile bones - Common in post-menopausal women (low oestrogen) - Calcium and vitamin D deficiency increases risk - Prevention: Exercise, calcium, vitamin D 2. Arthritis: - Inflammation of joints causing pain, swelling, stiffness - Osteoarthritis: Degeneration of cartilage (wear and tear), common in elderly - Rheumatoid arthritis: Autoimmune — immune system attacks joint lining - Gout: Accumulation of uric acid crystals in joints (often big toe) 3. Myasthenia gravis: - Autoimmune disorder affecting neuromuscular junctions - Antibodies block acetylcholine receptors - Causes progressive muscle weakness and fatigue