name - mervyn chah

class - 2 setia

The world through our senses

1.1Sensory organ and their functionsThe skin, nose, tongue, ears and eyes are our sensory organs.They enable us to use our senses of touch, smell, taste, hearing and sight to detect changes in our environment.Our senses are our abilities to detect changes in our environment.The changes in our environments are called stimuli (singular: stimulus).Table below shows the connection between the five senses, the sensory organs and the stimuli.

The pathway from stimulus to responseOur skin is sensory organ that can detect stimuli such as pain, pressure, touch, heat. Our skin consists of two main layers: Epidermis (outer layer) and Dermis (inner layer)There are 5 types of receptors in our skin. Can you identify them in the figure above?Each type of receptor is sensitive to a different stimulus.at and cold.

The skin at different body parts is not equally sensitive to stimuli. The skin of some body parts is more sensitive than that of other body part.Such difference is due to the different thickness of the epidermis and different numbers of receptors in the skin.

Functions of the nervous system in humans

Sensory organsenseTypes of stimuliSkintouchPressure, pain, heat, coldNoseSmellChemical in the airTongueTasteChemical in the foodEarsHearingSoundeyesSightlight

The sence of touch

THE SENSE OF SMELL

STRUCTURE OF A NOSEThe visible part of the human nose is the protruding part of the face that bears the nostrils. The shape of the nose is determined by the ethmoid bone and the nasal septum, which consists mostly of cartilage and which separates the nostrils. On average the nose of a male is larger than a female.

Structure of a human skinSkin is very important as it covers and protects everything.Skin holds everything together. It also protects our bodies, helps keep our bodies at just the right temperature and, through nerve endings close to the surface of the skin, allows us to have the sense of touch inside your body.However skin can become infected with bacteria, viruses and fungi, and can be irritated by chemicals or other substances it is in contact with.

Sensitivity of the skinWhen the receptors are stimulate, they send out nerve impulses along the nerves to the brain.The brain interprets these impulses as the sensation of touch.It will then send suitable messages to the effectors as how to react.

DETECTION OF SMELLCertain chemical particles present in the air circulate the smells in the airFor example , flowers ,food and perfumes release chemical into the airThe dissolve chemical particles stimulate the smell receptors.The smell receptors then send out nerve impulses to the brain

The sense of taste

Sence of taste and smell

Both of the senses of taste and smell are needed to detect the flavours of food accuratelyThe nasal cavity and the mouth are connectedChemicals from food that stimulate the taste receptors also move into our nasal passages.These chemicals stimulate the sensory cells in the nose

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