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  • Coordination
    • Systems
      • Nervous system detects change or stimuli and processes
      • Central nervous system is brain and spinal cord
      • Peripheral  nervous system is nerves carrying impulses from CNS
    • Receptors & effectors
      • CNS processes initiating response through effectors eg muscles or glands
      • Stumulus detected by receptors eg sensory cells or organs
      • reflex arc
        • involuntary rapid response
        • brain is bypassed
        • Stimulus causes receptor to signal sensory neurone sending impulse to spinal cord
        • relayed by relay neurone connecting sensory neurone to motor neurone
        • Signal reaches effector
      • Conduction
        • 2 factors affect speed
        • myelination speeds upas insulates preventing depolarisation
        • impulse has to jump between nodes of ranvier
        • saltatory conduction
        • diameter of axon, greater diameter= greater speed transmission
    • Hydra nerve net
      • Slow transmission
      • Limited responses to limited stimuli
      • Simple nerve cells with short extensions
    • Motor neurone structure
      • scwann cells cells attach to axon forming myelin sheath with interval nodes of ranvier
      • membraneous cytoplasmic axon with axon terminals at end are on cell body
      • dendrite thin extensions reach out from cell body
      • cell body has granular cytoplasm with ribosomes as nissl granules
    • Action potential
      • k+/Na+ pump restores polarity
      • stimulus detected by receptor causing charge reversal on axon membrane
      • -70mv to +40mv depolarising membrane
      • Na channels open influx of Na+ cause +40mv
      • Na Channels close K channels open K+ leave to repolarise
      • temporary overshoot on refractory period so another AP cant be generated
    • synapse
      • diffuses across to receptor sites on postsynaptic membrane for depolarisation for initiation of impulse
      • acetyl choline destroyed by enzymes in the cleft to limit effect
      • when impulse arrives at synaptic knob the permeability is altered
      • Ca+ enters so synaptic vesicles fuse with presynaptic membrane releasing acetyl choline into synaptic cleft
      • receptor sites change shape when acetyle choline binds to them opening the channel for Na+ to diffuse in starting an action potential
      • cholinesterase produces choline and ethanoic acid that diffuses backwards to presynaptic cleft to reform acetyl choline using atp to form storage vesicles
    • effecting transmission
      • caffine increases metabolic rate in presynaptic cells
      • increased atp production stimulates synthesis of neurotransmitter
      • organophosphates are in insecticides that block the enzyme that breaks down neurotranmitter
      • acts as neuromuscular junction causing uncontrollable muscle contractions
    • flowering
      • 3 types of flowering plants
      • day neutral unaffected by day length
      • long day plants induced by dark periods shorter than critical length
      • short day plants are induced by dark periods longer than critical length
        • flowering in short day plants is inhibited by exposure to red light which converts pfr to pr
      • short day plants only flower if pfr is low enough but this is the opposite for long day plants


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