Cards (8)

  • When stimulus is detected plasma membrane becomes more permeable; causing a voltage change across plasma membrane, reduces difference (depolarised)
  • Change is known as generator potential, bigger stimulus move more Na^+ ions in creating a larger voltage change; if crosses threshold (-55mV), it will cause an action potential
  • Voltage gated Na^+ ion channels open, making membrane more permeable to it, causing influx, making positive ions on inside more positive/less negative
  • Once voltage reaches -55mV it causes wave of depolarisation (electrical impulse); occurs on the all or nothing principle: it is same size and only occurs if specific value is reached
  • More voltage-gated Na+ channels open, and more Na^+ ions flood in making it more positive than outside until it reaches maximum (40mV)
  • It is a rapid, brief and temporary depolarisation of neurone cell surface membrane, caused by stimulus to membrane
  • Calculate time from first increase in membrane potential (when Na+ voltage gated channels open) to when resting potential is resumed (just after hyperpolarisation) for length of actio potential
  • Repolarisation: Eventually Na^+ channels close and K+ channels open, more K+ ions diffuse out down their gradient, bringing membrane back to resting potential