The brain and the nervous system

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Question 5
Medium

When a person accidentally steps on a sharp pin, a rapid reflex action occurs to lift the foot away.

A diagram of a reflex arc involved in a withdrawal reflex of the foot. A receptor in the skin of the foot is connected to Neurone P. Neurone P enters the spinal cord via the dorsal root. Inside the grey matter of the spinal cord, Neurone P meets Neurone Q. Neurone Q then connects to Neurone R, which leaves the spinal cord via the ventral root and connects to a muscle in the leg. There are tiny gaps shown between Neurone P and Q, and between Neurone Q and R.

Describe the pathway of the electrical impulses from the pain receptor in the foot to the effector muscle.

In your answer, you should:

  • name neurones P, Q, and R
  • describe the sequence of events along the reflex arc, including how information is passed between neurones.
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The brain and the nervous system Questions

  1. GCSE
  2. /Biology
  3. /The brain and the nervous system