LOCOMOTION AND MOVEMENT
Movement in Living Organisms
Movement is essential for all living beings.
Various forms of movement are exhibited by animals and plants.
Example: Streaming of protoplasm in unicellular organisms (e.g., Amoeba).
Cilia, flagella, and tentacles contribute to movement.
Humans demonstrate a range of voluntary movements (e.g., limbs, jaws, tongue).
Locomotion vs. Movement
Movements that result in a change of place are termed locomotion.
Examples of locomotion: walking, running, climbing, flying, and swimming.
Locomotory structures may overlap with structures responsible for other movements.
Example: In Paramecium, cilia aid both in locomotion and moving food.
Hydra uses tentacles for both locomotion and prey capture.
There is a connection between movement and locomotion:
All locomotion is a form of movement, but not all movement qualifies as locomotion.
Reasons for locomotion:
Search for food, shelter, mates, breeding grounds, and escape from predators.
TYPES OF MOVEMENT
Three primary types of movement in body cells:
Amoeboid Movement: Found in specialised cells like macrophages and leucocytes, facilitated by pseudopodia (streaming of protoplasm).
Ciliary Movement: Occurs in lined tubular organs (e.g., trachea), helping remove dust and aiding passage of ova in the reproductive tract.
Muscular Movement: Involves the contractile property of muscles for movement, including locomotion.
Successful locomotion involves coordination between muscular, skeletal, and neural systems.
MUSCLE
Muscles: Specialised tissue of mesodermal origin, constituting 40-50% body weight.
Properties of muscles: excitability, contractility, extensibility, and elasticity.
Types of muscles based on location:
Skeletal Muscles: Associated closely with the skeleton, striated appearance, voluntary control (involved in locomotion and posture).
Visceral Muscles: Located in hollow organs, nonstriated and involuntary (e.g., transport food).
Cardiac Muscles: Striated and branched, found in the heart, involuntary nature.
Structure of Muscle Fibres
Muscle fibre: Surrounded by plasma membrane (sarcolemma) enclosing sarcoplasm, contains multiple nuclei.
Sarcoplasmic reticulum stores calcium ions.
Myofibrils contain alternating dark (A band, thick myosin filaments) and light (I band, thin actin filaments) bands.
Sarcomere: Functional unit of contraction, defined by Z lines.
MECHANISM OF MUSCLE CONTRACTION
Sliding Filament Theory: Muscle contraction occurs as thin filaments (actin) slide over thick filaments (myosin).
Initiated by a neural signal from the CNS via motor neurons, forming a motor unit.
Neuromuscular junction: Site where the motor neuron contacts the muscle fibre; neurotransmitter (Acetylcholine) generates an action potential.
Increased calcium ion levels trigger binding of calcium to troponin, exposing myosin binding sites on actin.
Myosin heads bind to actin, forming cross-bridges, pulling actin filaments toward the center of the sarcomere—causing contraction.
Cross-bridges break and reform with new ATP, facilitating further contraction until calcium ions return to the sarcoplasmic reticulum, resulting in relaxation.
SKELETAL SYSTEM
Framework of bones and cartilages essential for movement.
Total of 206 bones in humans, organised into two divisions:
Axial Skeleton: 80 bones, including the skull, vertebral column, sternum, and ribs.
Skull: Composed of cranial (8) and facial bones (14).
Vertebral Column: Composed of 26 vertebrae; supports and protects spinal cord.
Ribs: 12 pairs; true ribs, false ribs, and floating ribs based on attachments.
Appendicular Skeleton: Includes limb bones and girdles, involving a total of 30 bones per limb.
JOINTS
Joints connect bones (or bone and cartilage) and allow movements.
Types of joints:
Fibrous Joints: No movement (e.g., skull bones).
Cartilaginous Joints: Limited movement (e.g., vertebrae).
Synovial Joints: Allow considerable movement; examples include:
Ball and socket (shoulder joint)
Hinge (knee joint)
Pivot (between atlas and axis)
Gliding (between carpal bones)
DISORDERS OF MUSCULAR AND SKELETAL SYSTEM
Myasthenia gravis: Autoimmune disorder causing muscle fatigue and paralysis.
Muscular dystrophy: Genetic disorder leading to skeletal muscle degeneration.
Tetany: Rapid muscle spasms due to low Ca++ levels.
Arthritis: Inflammation of joints.
Osteoporosis: Age-related bone mass decrease leading to fractures.
Gout: Joint inflammation from uric acid accumulation.
SUMMARY
Movement is crucial for survival; serves various purposes such as seeking food and shelter.
Three main types of body cell movements: amoeboid, ciliary, and muscular.
Coordinated muscle actions enable locomotion, with three types of muscles identified
The skeletal system, comprising bones and joints, is integral for movement and support.