Action potential

sodium - potassium pumpion channels in the neurone membrane - NON MYELINATED resting potential

Resting potential

  • the potential difference between the inside of the neurone and the outside when a neurone is at ‘rest’

  • - 70mV (minus 70)

  • due to relative distribution of ions

    • large negatively charged protein ions stay inside the cell

    • sodium - potassium pump (3Na+ out 2K+ in)

    • potassium ion channels allow K+ ions to diffuse out (as they are pumped in)

  • neurones are polarised

    • inside of a neurone contains more negatively charged ions than the outside

  • ion channels are found along the whole length of neurone

  • resting potential

Generating an action potential

  • when a neurone is stimulated the stimulus causes some of the sodium ion channels to open

  • Na+ ions enter cell

  • inside of the cell becomes more positive so cell potential difference changes

  • when threshold value is reached (-55mV) an action potential is generated and Na+ channels become fully open

  • at +40mV Na+ ion channels shut and K+ ion channels open

  • Refractory period

    • hyperpolarised

    • pump works harder to get back up to -70mV

  • action potential graph
action potential graph drawn

Pacinian corpuscle

  • pressure and vibration receptors found in the skin

  • mechanoreceptor

  • convert mechanical energy into electrical energy