SCIENCE FORM 2

THE WORLD THROUGH OUR SENSES

THE SENSORY ORGANS

Main sensory organsSKINNOSETONGUEEAREYE

FUNCTION OF MAIN SENSORY ORGANS

SKINDetect 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 SYSTEM

♥Responsible 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 RESPONSE

StimulusSensoryorgans

Sensory nerves

BrainMotor nerves

Responses

THE SENSES OF TOUCH

THE SKIN AS A SENSORY ORGAN

THE SKIN

♥The skin is made up of two layers: -the epidermis -the dermis♥The 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 RECEPTORS

TOUCH RECEPTORDetects any contact made with the

skin.

PRESSURE RECEPTORDetects pressure exerted on the

skin.

PAIN RECEPTORDetects pain when the skin is

injured.

HEAT RECEPTOR Detects heat or any that rise in temperature.

COLD RECEPTOR Detects a cold substance or any fall in temperature.