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

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

The stimulus (the finger touching the hot object) is detected by temperature or pain receptors in the skin. these generate impulses in sensory neurones. the impulses enter the central nervous system through a part of the spinal cord called the dorsal root. in the spinal cord the sensory neurones connect by synapses with short relay nerones, which in turn connect with motor neurones. the motor neurones emerge from the spinal cord through the ventral root, and send impulses back out to the muscles of the arm. these muscles then contract pulling the arm and therefor the finger away from the harmful stimulus.