2.85 describe the structure and functioning of a simple reflex arc illustrated by the withdrawalof a finger from a hot object

Only the spinal chord is used to product a reflex. This is so that time is reduced for the response and the persons finger won't be damaged as much.

Reflexes are always the same.
Reflexes can't be controlled but responses can.

The receptors are stimulated by the heat, electrical impulses sent to the spinal chord, The relay nerve directly connects the impulses to the motor nerve which creates the response to withdraw the hand.