2.84 + 2.85 nerve impulses --> responses

Understand that stimulation of receptors in the sense organs sends electrical impulses along nerves into and out of the central nervous system, resulting in rapid responses
                                                                     +Describe the structure and functioning of a simple reflex arc illustrated by the withdrawal of a finger from a hot object

1. Reflex actions

when a receptor is stimulated by a change, it sends an electrical impulse along the sensory nerves to the CNS, where the brain co-ordinates the response (decision making). Sometimes a very rapid response is need = reflex actions.

Reflex actions are rapid and happen without us thinking.

eg: pulling your hand away from a hot surface. (you do it without thinking about it)

• pain receptor detects a stimulus (heat)  
• sensory nerve sends the electrical impulse to the CNS, brain
• the motor nerve sends the signal to the effector 
• the effector (skin) produces a response (reflex +muscle contracts)