Stimuli, both internal and external, are detected and lead to a response (A-level only)

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Question 3

Medium

A tactile mechanoreceptor, such as a Pacinian corpuscle, responds to mechanical pressure on the skin.

Describe the sequence of events by which mechanical pressure on a Pacinian corpuscle initiates a generator potential in the sensory neurone.

[3]

Researchers studied the electrical response of a single Pacinian corpuscle in a mammalian paw when subjected to mechanical forces of different magnitudes. Figure 1 shows the changes in membrane potential over time following stimulation at $2.0\text{ ms}$ .

Figure 1: Membrane potential changes over time under different stimulus strengths

With reference to Figure 1, explain how the results demonstrate the all-or-nothing principle.

[2]

Between $2.0\text{ ms}$ and $6.0\text{ ms}$ , applying a second, highly intense mechanical stimulus is unable to trigger another action potential. State the term used to describe this specific duration of physiological insensitivity.

[1]

Stimuli, both internal and external, are detected and lead to a response (A-level only)

Question 3

Stimuli, both internal and external, are detected and lead to a response (A-level only) Questions

Stimuli, both internal and external, are detected and lead to a response (A-level only)

Question 3

Stimuli, both internal and external, are detected and lead to a response (A-level only) Questions