(I)GCSE Topic 2.85

Describe the structure and functioning of a simple reflex arc illustrated by the withdrawal of a finger from a hot object

Receptor: Heat sensor in the skin
- The impulse travels to the spinal cord along the sensory nerve.
- In the spinal cord the impulse is passes on to the relay nerve.
- This passes the impulse on to the MOTOR NERVE. 

Effector: Arm muscles
- The motor nerve carries the impulse to the muscle in the arm.

Response: Muscles 

- Contract to remove the hand from the hot surface.