SCIENCE FORM 2

SCIENCE FORM 2THE WORLD THROUGH OUR SENSES

THE SENSORY ORGANS

Main sensory organsSKINNOSETONGUEEAREYE

FUNCTION OF MAIN SENSORY ORGANSSKINDetect touch,pressure, pain, heat, cold.Organ for touch.

NOSEDetect chemicals.Organ for smell.

TONGUEDetect chemicals. Organ for taste.

EARDetect sound.Organ for hearing.

EYEDetect light.Organ for sight.THE HUMAN NERVOUS SYSTEMResponsible for detecting stimuli and changes in the environment and sending the information to the brain for interpretation.The brain then send out instructions to the relevant parts of the body for actions to be taken.The information and instructions are send out in the form of nervous impulses along nerves.The nervous system consists of the brain, the spinal cord and the nerves.The brain and the spinal cord form the central nervous system.The nerves which send nerves impulses from the sensory organs or receptors to the brain are called the sensory nerves.The nerves which carry nervous impulses from the central nervous system to the muscles or glands for carrying out the responses are called the motor nerves.

THE PATHWAY FROM STIMULUS TO RESPONSETHE SENSES OF TOUCH

THE SKIN AS A SENSORY ORGAN

THE SKINThe skin is made up of two layers: -the epidermis -the dermisThe skin is a sense organ helping the body to know what is happening in its surroundings.The nerve endings or receptors in the skin detects stimuli

THE FUNCTION OF RECEPTORSTOUCH RECEPTORDetects any contact made with the skin.

PRESSURE RECEPTORDetects pressure exerted on the skin.

PAIN RECEPTORDetects pain when the skin is injured.HEAT RECEPTORDetects heat or any that rise in temperature.

COLD RECEPTORDetects a cold substance or any fall in temperature.