Nervous System, continued.

The nervous system is coordinated by the brain and allows the body to respond to changes in the environment. We take our responses in very quick "reflex" actions  in response to stimuli. (changes in the environment)

Receptors 

• are groups of specialised cells that detect stimuli, and turn them into "electrical" impluses. 
• they are located in the sense organs, (ear, skin, nose and eye)
• each are sensitive to particular kinds of stimulus. 

Skin: receptors sensitive to: touch, pain, pressure and temperature. 
Tongue: receptors sensitive to: chemicals in food.
Nose: receptors sensitive to: chemicals in the air. 
Eyes: receptors sensitive to: light 
Ear: receptors sensitive to: sound

Process:  A receptor is stimulated by a change --> a signal (electrical impulses)  is sent along the sensory nerves to the CNS (brain+spinal cord) --> the brain then co-ordinates (decision) --> impulses are then sent along the motor nerves to the effector where the response is produced.

Eg of Effectors 

• a muscle contracting to move the arm
• a gland releasing a hormone into the blood
• a muscle squeezing saliva from the salivary gland
• a muscle squeezing sweat from the sweat gland