Chapter 50

  1. Types of skeletons
    1. Hydrostatic skeletons:
    1. softbodied inverts: earthworms or jellyfish
    1. circular and longitudinal muscles contract against a fluid filled body cavity.
    2. Limited size due to strength of contaction, limited speed due to method of contraction
    1. exoskeleton
    1. Arthropods (crustaceans & insects)
    1. hard outer body of chitin with attached muscle inside
    2. molt to grow
    3. limits to size due to mass of skeleton, vulnerable to predation during molting
    1. endoskeleton
    1. vertebrates, echinoderms
    1. calcified bones with attached muscles on exterior
    2. cellular and capable of growth and repair
  1. Bone
    1. vertebrate skeleton

      2. axial: crianium, vertebrae, ribs

      appendicular: appendages and girdles that join them to axis

    2. function:
    1. support and attachment of muscle
    2. protection of organs
    3. hematopoeisis: of RBC/WBC
    4. store of calcium and phosphate ions
    1. structure
    1. collagenous (cartilage) connective tissue become impregnated with calcium crystals of hydroxyapetiteè ossification.
    2. Blood supply to osteocytes within living bone tissue
    1. perforating canal (volkmanns canal) è central canal (haversian canal) è canaliculi è lacunae è osteocyte
    2. growth in long bones is at growth plates (epiphiseal plates) where cartilage increasesè some becomes ossified. Once all is ossified growth is complete.
    1. joints
    1. synarthrotic: immovable (sutures in skull)
    2. ampiarthrotic: slightly movable (symphysis pubis)
    3. diarthrotic: freely moveable (hinge, ball and socket, pivot, sadle, etc.)
  1. muscle
    1. origin non moving site where muscle is attached
    2. insertion moving site where muscle is attached
    1. synergists: muscle that aid prime movers
    2. antagonists: muscle that oppose prime movers
    1. sliding filament theory:
    1. muscle fiber is cell
    2. myofibrils organized units
    1. containing myofilaments
    1. actin: thin filament
    2. myosin: thick filament
    1. sarcomere
    1. thin/thick filaments overlap slightly
    2. Z-lines are attachment points for thin filaments
    3. H band is potential space between projecting thin filaments
    4. I band = thin filament only
    5. A band = thick filament and overlap of the two
    1. contraction

neuron releases ACH (acetylcholine) a stimulatory neurotransmitter into the synaptic cleft between neuron and myofiber. ACH diffuses to receptors on the sarcolemma changing the permeability of the sarcolemma to ions. This changes the polarity of the cell and is spread until it reaches T-tubules which are in contact with sarcoplasmic reticulum that store Calcium ions. When activated SR becomes permeable to Ca+ flooding the cell. Ca+ binds to troponin/tropomyosin/actin complex which undergoes a confomational change in shape moving it from its inhibitory position between actin and myosin. Myosin head now comes into contact with actin at the actin biding site/myosin binding site and ATP binds to the ATP binding site on myosin.