Pacinian Corpuscle

What type of stimulus does a Pacinian Corpuscle respond to?

Mechanical Stimuli

Describe the structure of a Pacinian Corpuscle.

Contains the end of a sensory neurone and the sensory nerve ending is surrounded by lamellae

Explain how the presence of a stimulus triggers an action potential in a Pacinian corpuscle

When a PC is stimulated, the lamellae are deformed and press on the nerve ending.
This causes the deformation of stretch mediated Na+ channels.
These Na+ channels open and sodium ions diffuse into cell (depolarisation).
This creates a generator potential and if it reaches threshold, it triggers an action potential.

What are lamellae?

Concentric rings of fibrous connective tissue

Give three examples of mechanical stimuli

Pressure, vibration, touch

Explain how the resting potential of -70 mV is maintained in the sensory neurone when no pressure is applied.

Membrane more permeable to potassium ions and less permeable to sodium ions;
Sodium ions actively transported / pumped out and potassium ions in.

What effect does the stimulus have on the sensory neurone?

Stretches the membrane of the neurone

Explain how the size of the stimulus affects the
formation of an action potential

A larger stimulus means the sensory neurone will be compressed in more areas, causing the membrane to stretch in more areas and lamellae become more deformed.
More stretch mediated sodium ion channels open causing a greater influx of sodium ions into the sensory neurone.
This means the generator potential produced is more likely to reach threshold and trigger an action potential

Why are receptors said to be specific?

Each receptor can only detect one type of stimulus