Introduction to Movement and Locomotion

  1. Definition and Significance:
    • Movement is a key feature of all living organisms.
    • Examples:
      • Amoeba: Protoplasmic streaming.
      • Other organisms: Use cilia, flagella, or tentacles.
    • Humans: Move limbs, jaws, eyelids, tongue, etc.
  2. Locomotion vs. Movement:
    • Locomotion: Voluntary movement leading to a change in location (e.g., walking, running, swimming).
    • All locomotions are movements, but not all movements are locomotions.
  3. Examples of Locomotory Structures:
    • Paramoecium: Cilia assist in feeding and movement.
    • Hydra: Tentacles help in prey capture and movement.
    • Humans: Limbs used for both locomotion and posture.
  4. Purpose of Locomotion:
    • Searching for food, shelter, mate, and breeding grounds.
    • Escaping predators and seeking favorable conditions.

Types of Movements in Humans

  1. Amoeboid Movement:
    • Found in cells like macrophages and leucocytes.
    • Involves pseudopodia formation and cytoskeletal elements like microfilaments.
  2. Ciliary Movement:
    • Found in organs lined with ciliated epithelium:
      • Trachea: Removes dust and foreign particles.
      • Female reproductive tract: Moves ova.
  3. Muscular Movement:
    • Involves contraction of muscles for movement (e.g., limbs, tongue).
    • Requires coordination between muscular, skeletal, and neural systems.

Muscle Structure and Function

  1. General Features:
    • Muscles are specialized tissues of mesodermal origin.
    • Make up 40-50% of adult human body weight.
    • Properties:
      • Excitability: Respond to stimuli.
      • Contractility: Shorten actively.
      • Extensibility: Stretch passively.
      • Elasticity: Return to original shape.
  2. Types of Muscles:
    • Skeletal Muscles:
      • Associated with bones, striated appearance, voluntary control.
      • Function: Locomotion and posture.
    • Visceral Muscles:
      • Found in hollow organs (e.g., digestive tract), smooth appearance, involuntary.
      • Function: Transport food and gametes.
    • Cardiac Muscles:
      • Found in the heart, striated but involuntary.
      • Function: Pump blood efficiently.

Detailed Muscle Structure

  1. Basic Unit:
    • A skeletal muscle is made of muscle bundles (fascicles), each containing muscle fibers.
    • Muscle fiber (cell) is enclosed by a sarcolemma (plasma membrane) and filled with sarcoplasm.
  2. Special Features:
    • Sarcoplasmic Reticulum: Stores calcium ions essential for contraction.
    • Myofibrils: Parallel filaments with alternating dark and light bands.
  3. Protein Composition:
    • Actin: Thin filaments; form the I-band (light).
    • Myosin: Thick filaments; form the A-band (dark).
  4. Functional Unit: Sarcomere
    • Region between two Z-lines.
    • Key areas:
      • Z-line: Anchors thin filaments.
      • M-line: Holds thick filaments.
      • H-zone: Central part of the thick filament not overlapped by thin filaments.

Additional Insights for Competitive Exams

  1. Locomotory Adaptations:
    • Different organisms have specialized structures:
      • Sponges: Flagella maintain water currents.
      • Euglena: Flagella aid locomotion.
      • Sperm cells: Flagellar movement for swimming.
  2. Muscle Disorders:
    • Muscular Dystrophy: Genetic disorder causing muscle degeneration.
    • Myasthenia Gravis: Autoimmune disease leading to muscle weakness.
  3. Key Muscle Proteins:
    • Troponin and Tropomyosin: Regulate contraction by interacting with actin and myosin.
  4. Applications:
    • Understanding muscle physiology aids in treating paralysis, designing prosthetics, and enhancing athletic performance.

Contractile Proteins and Muscle Structure

  1. Actin Filaments (Thin Filaments):
    • Composed of two twisted filamentous (F-actin) strands.
    • Each F-actin is a polymer of globular actin (G-actin) units.
    • Tropomyosin filaments run parallel to actin.
    • Troponin, a complex protein, is present on tropomyosin at intervals. It masks binding sites for myosin in the resting state.
  2. Myosin Filaments (Thick Filaments):
    • Made of polymerized monomeric proteins called meromyosins.
    • Each meromyosin has:
      • A globular head (HMM – Heavy Meromyosin) that acts as an ATPase and binds to actin and ATP.
      • A tail (LMM – Light Meromyosin).
    • The head and short arm (cross-arm) project outward and form cross-bridges with actin during contraction.

Mechanism of Muscle Contraction

  1. Sliding Filament Theory:
    • Thin actin filaments slide over thick myosin filaments, shortening the sarcomere and causing contraction.
  2. Process:
    • Signal initiation:
      • CNS sends signals via motor neurons to the neuromuscular junction.
      • Neurotransmitter acetylcholine triggers an action potential in the muscle fiber.
    • Calcium Release:
      • Action potential causes calcium (Ca²⁺) release into the sarcoplasm.
      • Ca²⁺ binds to troponin, exposing actin’s myosin-binding sites.
    • Cross-Bridge Formation:
      • Myosin heads bind to actin using ATP energy, pulling actin filaments inward.
    • Relaxation:
      • ATP binds again, breaking the cross-bridge.
      • Ca²⁺ returns to the sarcoplasmic reticulum, masking actin sites.
    • Fatigue:
      • Repeated use leads to lactic acid buildup due to anaerobic respiration.
  3. Muscle Fiber Types:
    • Red Fibers:
      • High myoglobin content (red color).
      • Rich in mitochondria, rely on aerobic respiration.
    • White Fibers:
      • Low myoglobin (white appearance).
      • Few mitochondria, depend on anaerobic energy.

Skeletal System

  1. Axial Skeleton (80 bones):
    • Skull (22 bones: 8 cranial, 14 facial).
    • Vertebral column (26 vertebrae: cervical, thoracic, lumbar, sacral, coccygeal).
    • Sternum and 12 pairs of ribs (7 true, 3 false, 2 floating ribs).
  2. Appendicular Skeleton (126 bones):
    • Limb bones:
      • Forelimbs: Humerus, radius, ulna, carpals, metacarpals, phalanges.
      • Hind limbs: Femur, tibia, fibula, tarsals, metatarsals, phalanges.
    • Girdles:
      • Pectoral (clavicle + scapula) connects forelimbs.
      • Pelvic (ilium, ischium, pubis) connects hind limbs.

Joints

  1. Types of Joints:
    • Fibrous: Immovable (e.g., skull sutures).
    • Cartilaginous: Limited movement (e.g., vertebral column).
    • Synovial: Free movement with synovial fluid (e.g., knee, shoulder).
  2. Synovial Joint Types:
    • Ball and socket (e.g., shoulder).
    • Hinge (e.g., knee).
    • Pivot (e.g., atlas-axis).
    • Gliding (e.g., wrist).
    • Saddle (e.g., thumb).

Muscle and Skeletal Disorders

  1. Myasthenia Gravis: Autoimmune disorder causing muscle fatigue and weakness.
  2. Muscular Dystrophy: Genetic disorder causing muscle degeneration.
  3. Tetany: Muscle spasms due to low calcium levels.
  4. Arthritis: Joint inflammation.
  5. Osteoporosis: Decreased bone mass, often due to reduced estrogen.
  6. Gout: Joint inflammation due to uric acid crystal buildup.

Additional Knowledge for Exams

  1. Myoglobin: Oxygen-storing pigment in muscles, crucial for endurance activities.
  2. Longest Bone: Femur.
  3. Smallest Bones: Ear ossicles (malleus, incus, stapes).
  4. ATP Role: Provides energy for muscle contraction and relaxation.
  5. Sliding Filament Theory Proponents: Andrew Huxley and Rolf Niedergerke (1954).

These notes encapsulate the essential details and provide added context for competitive exams. Let me know if you want to delve deeper into any topic!

These all are the notes of chapter 17. And important are below HERE. *#THANKS FOR VISITING, VISIT AGAIN#* 😊

1. What is movement in living organisms?

Answer: Movement is the ability of living organisms to change their position or the position of their body parts. All living organisms, including humans, show movement. Examples include amoeba moving by protoplasmic streaming and humans moving their limbs, jaws, eyelids, and tongue.

2. What is the difference between movement and locomotion?

Answer:

  • Movement refers to any change in position of body parts, such as moving the eyelids or jaw.
  • Locomotion is a type of movement that results in a change of location, like walking, running, or swimming. All locomotions are movements, but not all movements lead to locomotion.

3. What are examples of locomotory structures in organisms?

Answer:

  • Paramoecium uses cilia to help in feeding and movement.
  • Hydra uses tentacles for movement and capturing prey.
  • Humans use limbs for walking, running, and other movements.

4. What is the purpose of locomotion in animals?

Answer: Locomotion helps animals find food, shelter, and mates. It also helps in escaping predators and moving to favorable conditions for survival.

5. What are the types of movement in humans?

Answer:

  • Amoeboid Movement: Found in cells like macrophages and white blood cells. It involves the formation of pseudopodia (temporary projections of the cell) for movement.
  • Ciliary Movement: Found in organs with ciliated epithelium, like the trachea (clearing dust) or the female reproductive tract (moving eggs).
  • Muscular Movement: Involves the contraction of muscles to move body parts, such as limbs and the tongue. It requires coordination of the muscular, skeletal, and neural systems.

6. What are the features of muscles?

Answer:

  • Muscles are specialized tissues from mesoderm.
  • They make up 40-50% of the human body weight.
  • Muscles have properties like excitability (respond to stimuli), contractility (shorten actively), extensibility (stretch passively), and elasticity (return to original shape).

7. What are the different types of muscles?

Answer:

  • Skeletal Muscles: Attached to bones, striated in appearance, and under voluntary control. They are involved in locomotion and posture.
  • Visceral Muscles: Found in hollow organs (like the digestive tract), smooth in appearance, and under involuntary control. They help transport food and other substances.
  • Cardiac Muscles: Found in the heart, striated, but involuntary. They are responsible for pumping blood.

8. How is a skeletal muscle structured?

Answer: A skeletal muscle is made up of muscle bundles called fascicles, each containing muscle fibers. Each fiber is enclosed by a membrane called the sarcolemma and filled with sarcoplasm. Muscle fibers contain myofibrils made up of actin and myosin filaments that work together for contraction.

9. What are actin and myosin filaments?

Answer:

  • Actin: Thin filaments that form the light band (I-band) in muscles.
  • Myosin: Thick filaments that form the dark band (A-band).
  • These filaments interact during contraction, with myosin pulling actin filaments inward to shorten the muscle.

10. What is the sliding filament theory of muscle contraction?

Answer: The sliding filament theory explains how muscles contract:

  • Signal initiation: The CNS sends signals through motor neurons.
  • Calcium release: The signal triggers calcium release in the muscle.
  • Cross-Bridge Formation: Myosin heads bind to actin, using ATP energy to pull the actin filaments inward.
  • Relaxation: ATP is used again to break the cross-bridge, and calcium is pumped back, allowing the muscle to relax.

11. What are the two main types of muscle fibers?

Answer:

  • Red Fibers: Contain more myoglobin, rely on aerobic respiration, and are used for endurance activities.
  • White Fibers: Contain less myoglobin, rely on anaerobic respiration, and are used for quick bursts of energy.

12. What is fatigue in muscles?

Answer: Fatigue occurs when muscles cannot sustain activity due to the buildup of lactic acid from anaerobic respiration. This leads to muscle weakness and exhaustion.

13. What is the structure of the human skeleton?

Answer:

  • Axial Skeleton (80 bones): Includes the skull, vertebral column, sternum, and ribs.
  • Appendicular Skeleton (126 bones): Includes the limb bones and girdles (pectoral and pelvic) that attach limbs to the body.

14. What are the different types of joints in the human body?

Answer:

  • Fibrous Joints: Immovable joints, such as those in the skull.
  • Cartilaginous Joints: Limited movement, like in the vertebral column.
  • Synovial Joints: Free-moving joints, such as the knee, shoulder, and elbow.

15. What are some common muscle and skeletal disorders?

Answer:

  • Myasthenia Gravis: An autoimmune disorder that causes muscle weakness.
  • Muscular Dystrophy: A genetic disorder causing muscle degeneration.
  • Tetany: Muscle spasms due to low calcium levels.
  • Arthritis: Inflammation of joints.
  • Osteoporosis: Reduced bone mass, often due to aging or hormone changes.
  • Gout: Joint inflammation caused by uric acid buildup.

16. What are some important proteins in muscle function?

Answer:

  • Troponin and Tropomyosin: Regulate muscle contraction by interacting with actin and myosin filaments.
  • Myoglobin: An oxygen-storing protein in muscles, important for endurance.

17. What are the longest and smallest bones in the human body?

Answer: The longest bone is the femur, and the smallest bones are the ear ossicles (malleus, incus, and stapes).

18. What role does ATP play in muscle contraction?

Answer: ATP provides energy for both muscle contraction (cross-bridge formation) and relaxation (breaking the cross-bridge and pumping calcium back into the sarcoplasmic reticulum).

Additional Knowledge for Exams:

  • Muscle Disorders: Understanding muscle physiology is important for treating conditions like paralysis, designing prosthetics, and improving athletic performance.
  • Sliding Filament Theory: The theory was proposed by Andrew Huxley and Rolf Niedergerke in 1954, revolutionizing our understanding of muscle contraction.