Locomotion and Movement | Plus 1 | Exam Capsule Notes (Web and PDF)

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LOCOMOTION AND MOVEMENT: 

Chapter at a glance 

Types of movement in human being: 

• Amoeboid movement: By pseudopodia. E.g. Macrophages & leucocytes.
• Ciliary movement: By cilia. E.g. trachea & oviducts.
• Muscular movement: By muscles. E.g. limbs.

Types of muscles
Skeletal (striated)	Visceral (Non-striated)	Cardiac
Attached to skeleton	In visceral organs	In heart wall
Striations present	Absent	Present
Voluntary	Involuntary	Involuntary
Rich blood supply	Poor blood supply	Rich blood supply

STRUCTURE OF STRIATED MUSCLE 

Skeletal muscle is made of muscle bundles (fascicles) containing muscle fibres.

Muscle fibres are lined by plasma membrane (sarcolemma) enclosing the sarcoplasm.

Each muscle fibre contains myofilaments (myofibrils).

Each myofibril has dark (Anisotropic or A-band) and light striations (Isotropic or I-band).

• I-bands: Contain actin filaments. It is bisected by a dark band (Z-line). Region b/w 2 Z-lines is called sarcomere. They are the functional units of muscle contraction.
• A-bands: Contain actin & myosin. Its light middle region (H zone) is formed of myosin. H-zone has a dark line (M-line) at the centre.

Structure of contractile proteins: 

• An actin filament is made of 2 filamentous (F) actins.
• F-actin is a polymer of Globular (G) actins. 

• Actin contains 2 other proteins (tropomyosin & troponin).
• Troponin has 3 subunits.
• Each myosin filament is a polymer of Meromyosins.

• A meromyosin has 2 parts: Heavy meromyosin (HMM or cross arm) & Light meromyosin or LMM (tail).
• Head of cross arm is an ATPase enzyme.

MECHANISM OF MUSCLE CONTRACTION 

Sliding filament theory: 

Contraction of a muscle fibre occurs by the sliding of thin filaments over thick filaments.

Steps:

Impulse from CNS → neuromuscular junction → Synaptic vesicles release Acetylcholine → action potential in sarcolemma → release of Ca2+ from sarcoplasmic cisternae → Ca binds troponin → unmask the active sites for myosin → energy from ATP hydrolysis → myosin head binds to active sites on actin to form cross bridge → actin filaments pull towards centre of A-band → H-zone disappears → Z- line is pulled inwards → contraction of sarcomere.

Repeated activation of muscles → anaerobic breakdown of glycogen →  accumulation of lactic acid → muscle fatigue. 

Red (Aerobic) muscles: Red colour due to more myoglobin. More mitochondria. Aerobic metabolism. Slow & sustained contraction. 

White muscle: White colour due to less myoglobin. Less mitochondria. Anaerobic metabolism. Fast contraction for short period.

HUMAN SKELETAL SYSTEM 

(206 bones & few cartilages) 

I. AXIAL SKELETON (80 bones) 

1. Bones of head (29):

 

• Skull (22): Cranial bones (8) + Facial bones (14). 
• Ear ossicles (2x3=6) 
• Hyoid bone (1) 

    Skull articulates with First vertebra (atlas) by 2 occipital condyles (dicondylic skull). 

2. Vertebral column (26 vertebrae):

• Cervical vertebrae (7) 
• Thoracic vertebrae (12) 
• Lumbar vertebrae (5) 
• Sacrum (1) 
• Coccyx (1) 

3. Ribs (12 pairs):

• True ribs (1-7th pairs): Connected to sternum by Hyaline cartilage. 
• False or vertebro-chondral ribs (8-10th pairs): Join to the 7th rib. 
• Floating ribs (11-12th pairs): Not connected with sternum or other ribs. 

4. Sternum (Breast bone-1) 

II. APPENDICULAR SKELETON (126 bones) 

1. Bones of forelimbs (2x30 =60): 

• Humerus (1) 
• Radius (1) 
• Ulna (1) 
• Carpals (wrist bones)-8 
• Metacarpals (Palm bones)-5 
• Phalanges (digits- 4) 

2. Bones of hind limbs (2x30 = 60):

• Femur (thigh bone -1) 
• Patella (knee cap)-1 
• Tibia (1) 
• Fibula (1) 
• Tarsals (ankle bones)-7 
• Metatarsals (5) 
• Phalanges (digits -14)  

3. Pectoral girdles (2x2=4):

• Clavicle (collar bones)-2 
• Scapula (shoulder blades)-2  

    Clavicle articulates with acromion (elevated ridge) of Scapula. 
    Acromion has glenoid cavity into which humerus articulates to form shoulder joint. 

4. Pelvic girdles (2x1=2 coxal bones): 

• Each coxal bone is formed by the fusion of Ilium, Ischium & Pubis. 
• At the point of fusion of Ilium, Ischium and Pubis is a cavity (Acetabulum) to which the thigh bone articulates.
• The 2 halves of the pelvic girdle meet ventrally to form pubic symphisis.

JOINTS 

3 types:

Fibrous (immovable) joints: E.g. sutures of skull.

Cartilaginous (Slightly movable) joints: E.g. Joints between the adjacent vertebrae.

Synovial (movable) joints: Have a fluid filled synovial cavity between 2 bones. They are many types:

• Ball & socket: E.g. b/w humerus & pectoral girdle.
• Hinge joint: E.g. Knee joint
• Pivot joint: E.g. b/w atlas & axis.
• Gliding joint: E.g. b/w carpals
• Saddle joint: E.g. b/w carpal & metacarpal of thumb

DISORDERS OF MUSCULAR & SKELETAL SYSTEMS 

• Myasthenia gravis: An auto immune disorder that affects neuromuscular junction. Fatigue and paralysis of muscles.
• Muscular dystrophy: Progressive degeneration of skeletal muscles. Mostly due to genetic disorder.
• Tetany: Rapid muscle spasm due to low Ca2+ in body fluid.
• Arthritis: Inflammation of joints.
• Osteoporosis: Age-related disorder. Decreased bone mass causing fractures. Low level of estrogen is a common cause.
• Gout: Inflammation of joints due to accumulation of uric acid crystals. 

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