Pacinian Corpuscle
Laura Armstrong
Teacher
Contents
Recall Questions
This topic requires prior knowledge of an overview of the nervous system. You can test your knowledge on this below.
What is a receptor?
A specialised cell that detects a specific stimulus and initiates an electrical impulse.
What does a receptor do in response to a stimulus?
Converts energy from a stimulus into an electrical impulse.
What is meant by a stimulus?
A detectable change in the internal or external environment that is capable of causing a response.
Topic Explainer Video
Check out this @LauraDoesBiology video that explains the pacinian corpuscle, or read the full notes below. Once you've gone through the whole note, try out the practice questions!
Pacinian Corpuscle
What is the Pacinian Corpuscle?
- A mechanoreceptor found in the skin and other tissues.
- It detects mechanical pressure (e.g., touch, vibration).
- Example of a sensory receptor that generates an action potential in response to a stimulus.
Structure of the Pacinian Corpuscle
- Composed of:
-
- A single sensory neurone (axon ending) at the centre.
- Surrounded by multiple concentric layers of lamellae (connective tissue).
- Each lamella is separated by a gel-like substance.
- The neurone has stretch-mediated sodium ion channels in its membrane.
Where Are They Found?
- In the deep layers of the skin (especially in fingers and soles of the feet).
- Also located in joints, ligaments, and tendons — areas where detecting changes in pressure or movement is important.
What Stimuli Do They Detect?
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Mechanical pressure (e.g., vibrations, firm touch).
How Is an Action Potential Generated?
1. At rest:
- The stretch-mediated sodium channels are closed.
- The inside of the neurone is negative relative to the outside (resting potential).
2. When pressure is applied:
- The lamellae are deformed, stretching the cell surface membrane of the sensory neurone.
- Stretch-mediated sodium ion channels open, allowing Na⁺ ions to diffuse in.
3. Generator potential:
- The influx of Na⁺ causes the membrane to depolarise.
- If the threshold is reached, a generator potential leads to an action potential that travels along the sensory neurone.
Summary Table
Key Terms
- Pacinian Corpuscle: A pressure receptor in the skin that responds to mechanical stimuli.
- Mechanoreceptor: A receptor that responds to mechanical pressure or distortion.
- Stretch-mediated sodium ion channel: A type of channel protein that opens when the cell surface membrane is deformed.
- Generator potential: A small depolarisation in a membrane that can trigger an action potential.
- Action potential: An electrical impulse generated if the generator potential reaches threshold.
No answer provided.
Exam Tips
Don’t confuse generator potential with action potential.
The generator potential must reach threshold (i.e. enough Na⁺ must diffuse into the neurone) to trigger an action potential.
Make sure you name the Na⁺ channels as stretch-mediated Na⁺ channels.
No answer provided.
Describe how a Pacinian corpuscle responds to mechanical pressure to produce an action potential. (5 marks)
- When pressure is applied, the lamellae are deformed
- This stretches the membrane of the neurone, causing stretch-mediated Na⁺ channels to open.
- Sodium ions diffuse in.
- Causing the membrane to depolarise.
- A generator potential is created, and if threshold is reached, this will lead to an action potential.
Practice Question
Try to answer the practice question from the TikTok on your own, then watch the video to see how well you did!