AQA A Level Biology

Revision Notes

6.1.8 Generator Potential

Establishment of a Generator Potential

  • When Pacinian corpuscles are stimulated by pressure on the skin this leads to the establishment of a generator potential
    • This happens due to the movement of charged ions across the membrane
  • There is usually an excess of positively charged sodium ions (Na+) surrounding the axon
  • When pressure is exerted on the Pacinian corpuscle the layers of membrane become distorted and the stretch-mediated sodium protein channels in the axon membrane open
    • These channels are referred to as stretch-mediated sodium channels
  • Sodium ions enter the axon via facilitated diffusion
  • This influx of ions changes the electrical potential difference across the membrane
    • This leads to depolarisation
    • This establishes a generator potential
  • The generator potential triggers impulses (action potentials) that travel along the sensory neurone to the central nervous system

Generator potential 1, downloadable AS & A Level Biology revision notesGenerator potential 2, downloadable AS & A Level Biology revision notes

The influx of sodium ions establishes an electrical potential difference across the membrane of the axon. This is the generator potential.

Exam Tip

In the following sentence, the words in speech marks are the underlined keywords found in mark schemes – these must be incorporated to achieve the marks:
Pressure causes the stretch-mediated” sodium ion channels to “deform”, causing sodium “ions” to flow into the axon. This causes depolarisation” which leads to a generator potential.

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Author: Lára

Lára graduated from Oxford University in Biological Sciences and has now been a science tutor working in the UK for several years. Lára has a particular interest in the area of infectious disease and epidemiology, and enjoys creating original educational materials that develop confidence and facilitate learning.

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