Module 5 Section 5/4 - Plant and Animal Responses Part 3

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  • Module 5.5 Plant and Animal Responses (Muscles)
    • Antagonistic
      • as one relaxes the other contracts
    • Skeletal Muscle
      • Fibres appear striated
      • Control is conscious (voluntary)
      • regularly arranged so muscles contract in one direction
      • its rapid contraction
      • contraction length is short
    • Cardiac Muscle
      • Fibres appear specialised striated
      • Control is involuntary
      • the cells branch and interconnect resulting in simultaneous contraction
      • the speed of the contraction is intermediate as well as the length
    • Involuntary Muscle
      • Fibres appear non-striated
      • Control is involuntary
      • no regular arrangement meaning different cells can connect in different directions
      • the contraction is slow and can remain contracted for a long period of time
    • Structure of Skeletal muscles
      • fibres bound together into a dascicle
        • Fascicle's bind to form a muscle
      • muscle fibres are multi-nucleate
        • sarcolemma
          • cell membrane of muscle fibres
        • ER
          • Sarcoplasmic reticullum
        • cytoplasm
          • sarcoplasm
      • transverse tubules run through fibres
      • Each fibre contains myofibris (contractile in the muscle)
    • Sliding Filament model of muscle contraction
      • contraction caused by myofibrils changing length
      • myofibrils centain bundles of thick (myosin) and thin (actin) myofilaments)
      • myosin and ctin are cytoskeleton components
    • Sacromere
      • a unit of thick and thin filaments.
        • the distance between the two z-lines is about 2.5um long at rest
    • A - band
      • length of a thick filament responsible for contraction
    • M-line
      • a disk in the middle of the sarcomere. formed of cross connecting elements of the sytoskeleton
    • z - line
      • holds together the thin filaments. forms the borders of one sarcomere
    • h-zone
      • area of thick filament where there is no overlap with the thin filament.
        • the m-line would be at the centre of the -zone
    • Energy supplies and ATP
      • Myoglobin releases o2 when surrounding concentrations are low (emergency store)
      • anaerobic respiration means you do not receive much ATP per glucose molecule
    • Neuromuscular Junctions
      • end of motor neuron synapses with a muscle
      • neurotransmitter:Acetylchoine
      • folded postsynaptic muscle cell
        • e.g. motor end plate
        • increases surface area so more can be present (receptors)
      • threshold potential doesn't have to b reached for a contraction to occur
        • single impulse needed


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