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