Biology: Coordination

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  • Biology: Coordination
    • Forms of Coordination
      • Nervous System
        • Uses nerve cells to pass electrical impulses
          • Stimulates target cells via secretion of neurotransmitters
          • Used for rapid communication between specific parts
          • Short lived
          • Effect is temporary and reversible
      • Hormonal System
        • Communication via hormones
          • Slow
          • Widespread
          • All parts of the body, but only target organs respond
          • Transmission via blood
          • Long lasting and may be permenant
          • Plant growth factors
            • Light
            • Gravity
            • Water
            • Plant growth factors are plant hormones such as IAA
    • Neurones
      • Structure
        • Cell body - nucleus and RER, produces proteins and neurotransmitters
        • Schwann Cells- provides insulation and carry out phagocytosis and nerve regeneration
        • Myelin Sheath- rich in myelin lipid, carry impulses faster
        • Nodes of Ranvier - gaps between adjacent schwann cells where there is no sheath, 2um long
      • Types of neurones
        • Sensory Neurones
          • One dendron and one axon
          • Transmit impulses from a receptor to an immediate or motor neurone
    • Passage of impulses
      • Resting Potential
        • Intrinsic proteins
          • Active transport of K and Na ions
            • Allows diffusion
              • 'Voltage gates'
          • PPL bilayer prevents Na and K ions diffusing across it
        • Sodium  (3) actively transported out of axon by Na-K pump
          • Potassium  (2) ions transported into axon by Na-K pump
            • More sodium ions than potassium in tissue fluid than in the cytoplasm, causes chemical gradient
              • Gates closed to prevent diffusion
                • Negative inside and positive outside of axon
                  • Chemical, electrical  gradients are balanced, no net movement of ions
      • Acton Potential
        • Energy of stimulus causes Na gates to open, Na ions diffuse into axon
          • Triggers a reversal of potential difference
            • +40mV reached, voltage gates closed
              • K gates open
                • Causes repolarisation
                  • Outward diffusion of K ions causes a temporary overshoot of electrical gradient
                    • inside of axon more ngative
                      • Factors affecting speed
                        • Myeelin Sheath
                          • Diameter of axon
                            • Temperature
                          • Refractory period
                            • Ensures action potential goes in one direction
                              • Produces discrete ompulses
                                • Limits number of action potentials
    • Structure of a Synapse
      • Transmits impulses via neurotransmitters
        • Separated by a synaptic cleft
          • Neurone that emits = presynaptic neurone
          • Axon is the synaptic knob
            • Neurotransmitters stored in synaptic vesicles
          • Postsynaptic neurone has NT receptors
  • Dendrons- carry nerve impulses towards cell body
    • Axon- carries nerve impulses away from body
  • Motor Neurones
    • Transmit impulses from an intermediate or sensory neurone to an effector
      • 1 axon, many dendrites
    • Types of neurones
      • Sensory Neurones
        • One dendron and one axon
        • Transmit impulses from a receptor to an immediate or motor neurone
  • Intermediate Neurones
    • transmit impulses between neurones
  • Resting Potential
    • Intrinsic proteins
      • Active transport of K and Na ions
        • Allows diffusion
          • 'Voltage gates'
      • PPL bilayer prevents Na and K ions diffusing across it
    • Sodium  (3) actively transported out of axon by Na-K pump
      • Potassium  (2) ions transported into axon by Na-K pump
        • More sodium ions than potassium in tissue fluid than in the cytoplasm, causes chemical gradient
          • Gates closed to prevent diffusion
            • Negative inside and positive outside of axon
              • Chemical, electrical  gradients are balanced, no net movement of ions
  • Energy of stimulus causes Na gates to open, Na ions diffuse into axon
    • Triggers a reversal of potential difference
      • +40mV reached, voltage gates closed
        • K gates open
          • Causes repolarisation
            • Outward diffusion of K ions causes a temporary overshoot of electrical gradient
              • inside of axon more ngative
                • Factors affecting speed
                  • Myeelin Sheath
                    • Diameter of axon
                      • Temperature
                    • Refractory period
                      • Ensures action potential goes in one direction
                        • Produces discrete ompulses
                          • Limits number of action potentials
  • Transmits impulses via neurotransmitters
    • Separated by a synaptic cleft
      • Neurone that emits = presynaptic neurone
      • Axon is the synaptic knob
        • Neurotransmitters stored in synaptic vesicles
      • Postsynaptic neurone has NT receptors
  • Function
    • single impulse to many neurones
      • Create a number of simultaneous responses
        • Number of impulses to be combined at the synapse
          • Features of synapses
            • Unidirectionality
  • NT made in the presynaptic neurone
    • Synaptic vesicles released into the synapse, when action potential reaches the SK
      • Neurotransmitters diffuses across the cleft to receptor molecules
        • Neurotransmitter binds with receptor molecules, sets up new action potential
  • Features of synapses
    • Unidirectionality
  • Summation
    • Spatial - number of different impulses - together triggers new action potential
    • Temporal- one fires many times

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