Support and Movements: Key Concepts

Support and Movements: Concepts and Need

• Plants need support from collenchymatous cells (young) and sclerenchymatous cells (adult). Animals use muscles, cartilage, and bones.

• Animals move for food, safety, and shelter; plants are mainly stationary.

Support in Plants

• Turgor Pressure: Hydrostatic pressure in cells maintains rigidity. Loss of turgidity causes wilting.

  • Generated by osmotic pressure in cell vacuoles.

  • Tonoplast: Membrane bounding vacuole; actively transports ions, increasing water intake and turgidity.

• Specialized Tissue:

  • Sclerenchyma Cells: Thick, lignified secondary walls for support; usually non-living.

    • Fibers (Tracheids): Long, cylindrical; in xylem or bundle caps.

    • Sclereids: Shorter, in seed coats and nut shells for protection.

    • Vessels (Trachea): Tubular, form water-conducting pipes in xylem.

  • Collenchyma Cells: Protoplasts, lack secondary walls, angular thickenings. Support young, growing parts.

  • Vascular Tissue: Xylem provides support like steel rods. Sclerenchyma fibers strengthen vascular bundles.

Significance of Secondary Growth

• Increases plant girth via vascular cambium activity.

• Vascular cambium: Produces secondary xylem (inner) and secondary phloem (outer).

• Secondary xylem forms annual rings, used for age determination.

• Sapwood: Active in water conduction.

• Heartwood: Inactive, accumulates chemicals for decay and insect resistance.

• Callus Formation: Parenchymatous tissue over wounds, aids in grafting.

Movement in Plants

• Autonomic Movements: Spontaneous, internal causes.

  • Tactic Movements: Entire cell or organism moves.

    • Phototactic: Response to light (e.g., chloroplast movement).

    • Chemotactic: Response to chemicals (e.g., sperm towards archegonia).

  • Turgor Movements: Changes in cell turgor.

    • Sleep Movements: (e.g., Bean plants) Leaf position changes due to pulvinus turgor.

    • Rapid Leaflet Movement: (e.g., Mimosa) Leaflets fold due to rapid turgor loss.

  • Growth Movements: Unequal growth in plant organs.

    • Epinasty: Upper surface grows more (bud opening).

    • Hyponasty: Lower surface grows more (bud remains closed).

    • Nutation: Zig-zag growth of stem tip.

• Paratonic Movements: Due to external causes.

  • Tropic Movements: Curvature towards/away from stimuli.

    • Phototropism: Response to light.

    • Thigmotropism: Response to touch (e.g., climbing vines).

    • Chemotropism: Response to chemicals.

    • Hydrotropism: Response to water.

    • Geotropism: Response to gravity.

  • Nastic Movements: Non-directional responses.

    • Nyctinasty: Due to photoperiod/temperature.

      • Photonasty: Light intensity affects flower opening/closing.

      • Thermonasty: Temperature affects flower movements (e.g., tulip).

    • Haptonastic: Response to contact (e.g., Venus flytrap).

Role of Plant Growth Substances

• Auxins: Influence phototropism and gravitropism.

• Gravitropism: Auxins inhibit root cell growth, stimulate stem cell growth.

• Nastic Movements: Balance between growth inhibitors (abscisins) and stimulators (gibberellins).

Support and Movement in Animals: The Skeleton

• Provides protection, shape, and support.

• Types: Hydrostatic, Exoskeleton, Endoskeleton.

• Hydrostatic Skeleton: Fluid-filled cavity supports movement.

  • Sea Anemone: Water-filled cavity and muscle contractions maintain upright position.

  • Earthworm: Fluid-filled compartments move via muscle contractions and setae.

• Exoskeleton: Hardened outer surface for muscle attachment.

  • Composition: Epicuticle (waxy lipoprotein, impermeable) and Procuticle (chitin and protein).

  • Molluscan: Shell of calcium carbonate.

  • Arthropods: Complex exoskeleton with adaptations for muscle attachment, joints, sensory receptors, and gas exchange.

  • Ecdysis (Moulting): Shedding exoskeleton for growth, controlled by ecdysone.

• Endoskeleton: Internal skeleton of bone and cartilage.

  • Bone: Rigid connective tissue with collagen hardened by calcium phosphate.

    • Compact Bone: Dense, strong, for muscle attachment.

    • Spongy Bone: Light, porous, contains bone marrow for blood cell formation.

    • Cells: Osteoblasts (form bone), Osteocytes (mature), Osteoclasts (dissolve bone).

  • Cartilage: Flexible connective tissue; chondrocytes secrete collagen matrix.

    • Hyaline Cartilage: Most abundant, at moveable joints.

    • Fibro Cartilage: Contains collagen fibers, in ears and epiglottis.

Human Skeleton

• Axial Skeleton: Skull, vertebrae, ribs, sternum.

  • Skull: Cranium (8 bones, protects brain) and Facial Bones (14 bones).

  • Vertebral Column: 33 vertebrae (cervical, thoracic, lumbar, pelvic), protects spinal cord.

  • Rib Cage: 12 pairs of ribs; supports chest cavity.

• Appendicular Skeleton: Pectoral girdle (scapula, clavicle), pelvic girdle, limbs.

  • Fore Limb: Humerus, radius, ulna, carpals, metacarpals, phalanges.

  • Hind Limb: Femur, tibia, fibula, tarsals, metatarsals, phalanges.

Joint Classification

• Based on Movement:

  • Immovable

  • Slightly Movable

  • Freely Movable: Hinge joint, Ball and socket joint

• Based on Structure:

  • Fibrous Joints: Held by short fibers (e.g., skull).

  • Cartilaginous Joints: Reduce friction (e.g., between vertebrae, at the pubic symphysis).
    Synovial Joints: Hinge Joint and Ball & Socket Joint

Deformities of Skeleton

• Genetic Causes: Cleft palate, Microcephaly, Osteoarthristis

• Hormonal Causes: Osteoporosis (reduced bone mass)

• Nutritional Causes: Osteomalcia (soft bones), Rickets (vitamin D deficiency).

• Disc-Slip: Rupture of annulus fibrosus.

• Spondylosis: immobility and fusion of vertebral joint.

• Sciatica: Injury of sciatic nerve: pain, weakness.

• Arthritis: Joint inflammation.

Repair of Broken Bones

• Procedure: Reduction (realignment), Immobilization (cast).

• Phases: Hematoma formation, Callus Formation (soft callus), Bony Callus Formation (hard callus), Remodeling.

Muscles

• Specialized cells with actin and myosin.

• Types: Smooth, Cardiac, Skeletal.

  • Smooth: Non-striated, involuntary, in blood vessels and digestive tract.

  • Cardiac: Striated, involuntary, in heart.

  • Skeletal: Striated, voluntary, attached to bones via tendons.

Skeletal Muscle Fibre

• Composed of muscle bundles, fibres (cells).

• Myofibrils: Contractile units with sarcomeres.
  A bands (dark), I bands (light), H-zone, Z-line.

Ultrastructure of Myofilament:

• Thick Filament: Myosin with cross bridges.

• Thin Filament: Actin, tropomyosin, troponin.

Sliding Filament Model:

• Actin slides past myosin.

• I-band shortens, Z-lines move closer.

Controlling Actin-Myosin Interaction by $Ca^{++}$ Ions

• Nerve impulse -> SR releases $Ca^{++}$ -> binds troponin -> exposes myosin binding sites -> contraction.

• ATP needed for myosin bridge detachment.

• Rigor mortis: ATP depletion after death causes muscle stiffness.

Controlling the Actin-Myosin Interaction by Calcium Ions:

*T-Tube and its Role: Nerve impulse carried via T-tubules. Calcium is released from SR for muscle contraction.
*All or None Response: Contraction based on fibre participation.

Other Key Points

• Energy for Muscle Contraction: From ATP; maintained by aerobic glucose breakdown.

• Muscle Fatigue: ATP deficit, lactic acid accumulation.

• Muscle Exercise: Increase in fibre size, strength, efficiency.

Tetany

Low calcium in blood -> Muscle twitches and convulsion.

Tetanus

Bacterial, causing painful spasms.

Arrangement of Skeletal Muscles

The skeletal muscles produce movements by pulling on tendons that attach muscles to the bones. The term tetanus is used for an acute infectious disease caused by anaerobic bacterium clostridium tetani resulting in persistant painful spasms of some skeletal muscles

Locomotion

• Locomotion is swift walking but it also takes to flight by its wings in Cockroach.

• Jelly fish has an umbrella-like body called bell.

Evolutionary Changes:

Mammals walk on the tips of toes modified into hoof as deer, goat, horse.