F214 Unit 4: Nervous communication

  • Created by: Saoirse
  • Created on: 09-06-14 23:04

Sensory receptors

  • Specialised cells that can detect changes in our surroundings
  • Energy transducers - convert from one form to another
  • Each change in energy is called a stimulus

Generating nerve impulses

  • Neurones have specialised gated protein channels specific to K+ or Na+ ions
    • When open permability for the ion increases, decreases when closed.
  • Nerve cell membranes have carrier proteins that actively pump Na+ out and K+ in.
    • More Na+ moved out than K+ in giving inside of cell a negative (less positive) charge
    • Cell membrane is polarised
  • Nerve impulse created by altering permeability to Na+ ions.
    • Movement of ions across membrane causes a change in potential difference (charge) across the membrane
    • Inside becomes less negative than usual - depolarisation
  • A generator potential is a small depolarisation caused by sodium ion entering the cell


  • Sensory neurones: carry AP from sensory receptor to central nervous system
  • Motor neurones carry AP from CNS to an effector e.g muscle/gland
  • Relay neurones connect sensory and motor neurones
  • Function is to transmit AP from one place to another. Specialised:
    • Very long to transmit AP across a long distance
    • Many gated ion channels to control entry of Na+, K+ and Ca+
    • Na/K pumps present that use ATP to pump Na+ out
    • Maintain a potential difference across cell membrane
    • Surrounded by fatty myelin sheath
      • Series of Schwann cells
      • Insulates neurone from electrical activity in nearby cells
      • Gaps = Node of Ranvier
    • Motor neurones have cell body in CNS and have a long axon to carry AP to effector
    • Sensory neurones have a long dendron carrying the AP from a sensory receptor to the cell body, positioned just outside CNS. Then have a short axon carrying AP to CNS
    • Dendrites are connected to neruones

Resting potentials and action potentials

Resting potential is the potential difference across a neurone cell membrane while the cell is…


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