Science Portfolio JAZZ

8/3/2019 Science Portfolio JAZZ

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SENSORYORGAN AND THEIR

FUNCTIONS

Human have five sensesThe five senses are sight, hearing, touch, tasteand smellThe five senses are found in parts of the bodycalled sensory organWe respond to stimulus in a few stepsFirst, the stimulus is detected by the sensoryorgan.A message is the sent to the brain through thenerveThe brain interprets the message and help youunderstand what is going around you.The brain decides what to do and sends anothermessage through the nerve to some other bodyparts.Upon receiving the message your body respondsto the stimulus


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SENSES OFTOUCH

Our skin is the sensory organ that gives us thesense of touch.

It contains receptors that detect touch,pressure, heat and cold and pain.

Touch and pressure receptors detect touch.Heat and cold receptors detects the

temperature around the skinPain receptors are different than otherreceptors because the amount of receptors in

the skin is different depending on the part ofbody


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SENSES OF SMELL

Our nose is the sensory organ for smell.It can detect at least 20 different smells

Smells are carried by certain chemicals gothrough our nose. It will then dissolve in thelayer of moisture that covers the smellreceptors on the upper part of the nose. Thedissolved chemicals stimulate the smell

receptors. The simulated smell receptors thensend messages to the brain.


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SENSE OF TASTE

Our tongue is the sensory organ that gives usthe sense of taste.

Sensory cells that detect taste are called tastereceptors.

Taste receptors can detect sweet, sour, saltyand bitter.

When we drink or eat, dissolved substance inour mouth are detected by the taste receptorsin our tongue. Messages are the sent to ourbrain through nerves


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SENSE OF HEARING AND SOUND

Our ear is the sensory organ for the sense ofhearing.

The hearing mechanism1. The pinna collects sound waves and

directs it down the ear canal.

2. The sound waves heads towards theeardrum. The sound waves hits the eardrum causing it to vibrate.

3. The vibration causes a chain of tiny ear

bones to vibrate.4. As the last ossicle is connected to theoval window, the vibrations of the ossiclealso causes the oval window to vibrate.


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5. As the oval window moves in and out itcauses the fluid in the cochlea to vibrate aswell.

6. The cochlea detects the vibrations and

responds by sending the messages to thebrain through the auditory nerves.

7. Messages sent through the auditory nervesreach the rain which then interprets the

messages as sounds.Parts Of HumanEar FunctionPinna Collects sound waves and then

directs the sound down the ear canal

Ear Canal Directs the sound waves to the eardrum

Eardrum Sound waves in the ear strike againstthe eardrum and causes it to vibrate

Ossicles The vibrating eardrum causes the

chain of ear bones to vibrate. Thelast vibrating ear bone vibrate againsta membrane called the oval window.

Oval Window As the oval window vibrates, itmakes the fluid In the cochleavibrate.

Cochlea The cochlea detects the vibration andconverts them into nerve impulse

Auditory nerves Send messages to the brain whichinterpret the message as sounds


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Defects Of Hearing. Our ear is a very delicate sensory organ. It

can be easily damaged leading to defects inour hearing. Humans are said to have defects

if they cannot hear certain sounds. Limitations Of Hearing. We cannot hear all the sounds around us.

Different people have different limitations of

hearing Stereophonic Hearing Hearing with two ears enables us to tell

which direction the sound is coming from.

Stereophonic hearing involves the use of twoears.


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SENSE OF SIGHT AND LIGHT Our eyes are the sensory organ for sight.

How do we see? 1. When the light from an object enters the

eye, it first passes through he cornea wherethe light is slightly bent

2.The bent light then passes through aliquid behind the cornea and reaches thepupil. The pupil is the opening throughwhich the light enters the eye.

3.Light then passes through the pupil strikes

the lens. Here the light is further bent toproduce an upside down image that formson the retina


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4. The lights receptors on the retina detectsthe image that is made up of light. Theyproduce a message.

5. The message is sent to the brain along the

optical nerve. The brain then interprets themessage and we see the object the rightway up.

Properties Of Light Reflection is the bouncing of lights of asurface on which light falls on. Refraction is the bending of light when light

passes at an angle from one medium such asair to another medium such a glass, eachmedium with a different density.


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Monocular And Stereophonic Visions. The survival of an animal often depends on

the position of the animals eyes. Someanimal, for example, have eyes on the sides

of their head. This kind of vision is calledmonocular vision.

Some animal have eyes on the front oftheir heads. This helps them to judge the

distance of objects that they are lookingat. These two views are put together toform a 3D image rather than just a flatimage. This vision is called stereoscopicvision.

MonocularVision

Stereoscopic Vision


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STIMULI AND RESPONSES IN

PLANTS

Positive And Negative Tropism Plants, like all other living things, can also

react to changes in their surroundings. However, unlike animals, plants often

react slowly to stimuli such as light, water,gravity and touch.

Tropism is when plant move towards oraway from a stimulus.

If the plant move towards the stimuli it is

called positive tropism If the plant does the opposite it is called

negative tropism. Plants response to ; Phototropism,

geotropism, hydrotropism,thigmotropism and nastic movement


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Phototropism Phototropism is the movement or growth

of plants in response towards light. Geotropism Geotropism is the movement or growth

towards gravity. Hydrotropism Hydrotropism is the movement or growth

of plants in response to water. Thigmotropism Thigmotropism is the movement or growth

of plants in response to touch.


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CHAPTER 2 :

NUTRITION


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CLASSES OF FOOD

Carbohydrates Carbohydrate gives us energy. They are

sugars and starch found in food. Excesscarbohydrates are stored as fat.

Proteins. Proteins are used for building body

tissues, enzymes and hormones. Protein isneeded for growth , development andrepair of body tissue. They also gives usenergy.

Fats. Fats provide us with energy and warmth.

Fats are found in animal products such asbutter and fatty meat. Fats are also foundin plant products.

Vitamins. Vitamins are needed in small amounts for

our health and growth. A shortage ordeficiency in any vitamin may cause

health problems.


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Minerals. Minerals are needed in small amount for

our growth and development. They are alsoneeded by body tissues and used in somechemical reactions in the body.


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Fibre. Fibre keeps our intestines healthy and

working properly. Food containing fibrecan move along quickly and easily through

the intestines. Without fibre, we mayconstipate. Eating food containing fibrealso prevents cancer piles and even bowelcancer.

Water. Water is needed for breaking down food,

dissolving the different classes of food andtransporting various substances aroundour body. Water makes up 70% of our

body weight and forms a major part of ourblood. Chemical reaction in our body canonly take place if there is enough water.


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THE IMPORTANCE OF A BALANCE

DIET.

A Balanced Diet.A balanced diet contains the right

amount of energy for our needs. Wemust eat enough of seven classes of foodfor our growth, development and health.

A balanced diet is determined by thepersons age, size, sex, occupation oractivity, state of health or the climateand environment..

Calorific Value Of Food. Energy stored in food can be measured

in units such as calories or joules(1Calorie = 4.2 joules).


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HUMAN DIGESTIVE SYSTEM

Digestion. Some classes of food like starch, protein

and fats consist of large molecules thatcannot be absorbed by the bloodstreaminto our cells. For the large molecules toenter it must be broken down into tiny

molecules. The process of breaking downthe large food molecules is calleddigestion.

The human digestive system is made up ofa tube called the alimentary canal, also

known as the gut, and several other organthat work together to break down thefood as we eat.


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The Flow Of Food In The AlimentaryCanal. Food travels through our body along the

alimentary canal. It is a continuous tube

beginning at the mouth and ending at theanus. Mouth. Digestion starts in the mouth. Food is being

chewed by our teeth and it is broken downinto smaller pieces.

The food is mixed up with saliva and anenzyme, amylase. An enzyme is a substance

that speeds up a specific chemical reaction inthe body. Amylase is a digestive enzyme thathelps to break down large starch moleculesinto the smaller molecule. It digest starchinto glucose. Food is usually not kept longin the mouth so, not all the starch can bedigested. Our tongue rolls up the digested

food into a lump and the lump travels downthe esophagus. Esophagus or Gullet. The esophagus is a narrow tube with smooth

muscles in it walls. After food enters theesophagus, The food is being pushed downby a motion called peristalsis.


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Stomach. The stomach is a muscular bag with wall

that secretes hydrochloric acid, waterand protease, a digestive enzyme. Food

may be held in the stomach by itscontracted muscles for several hours.Contracted stomach muscles also churnup the food in the stomach withhydrochloric acid, water and protease.Protease helps to digest proteins intoamino acids. When most of the proteinsare digested a thick liquid called chymeleaves the stomach.

Small Intestine. The small intestine is where most of the

digestion of food takes place. It has adiameter of about 2 cm but a lenght of

more than 6 m. As the chyme movesinto the small intestine, it mixes theenzymes and secretion from threedifferent organs the small intestine,

the liver and the pancreas.


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The liver and the pancreas deliver theirenzymes or secretions to the smallintestine through small tubes . The liverproduce bile, a substance that breaks up

large fat droplets into smaller particle.Bile flows from the liver into the gallbladder, the organ that stores bile. Asfood enters the small intestine, bile passesthrough a tube from the gall bladder intothe small intestine. It then mixes withfood.

The pancreas produces digestive enzymessuch as amylase, protease and lipase that

flow into the small intestine. Amylasehelps to break down starch into glucose.Protease help to break down protein intoamino acids. Lipase helps to break downfats into fatty acids and glycerol.

The small intestine produces differentenzymes such as amylase, lipase andprotease to complete the digestion ofcarbohydrates, fats and proteins.

Digestion of food in our body ends inthe small intestine.


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ABSORPTION OF DIGESTED

FOOD

The inner lining of the small intestine is

lined with many ridges and folds -:

Note the millions of tiny finger shapedprojections called vili that covers thelining of the small intestine. The

presence of vili greatly increases thesurface area of the small intestine. Thegreatly increased surface area enablesdigested food to be absorbed faster into

the small intestine than if the walls were

smooth.


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REABSORTION OF WATER AND

DEFECATION Reabsortion Of Water In The LargeIntestine. The large intestine forms the last part of

the digestive system. It has a diameter of

about 6cm to 7cm but a length of about2m. By the time the watery mixture from the

end of the small intestine enters the largeintestine, most of the products ofdigestion would have been absorbed into

the body . The large intestine reabsorbslarge amount of water from the waterymixture through its walls. As water is

reabsorbed , the watery mixture changesinto solid waste that contain undigestedfood such as fibre, bacteria, dead cells andothers.


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Defecation. The large intestine ends in a short tube

called the rectum. Here, the solid wasteare compressed. The compressed waste

leave the body through the anus, amuscular opening at the end of therectum, as faeces, through a processcalled defecation.

Defecation is the process in which faecesis expelled from the body through therectum due to contractions of musclesin the rectal wall

Rates of defecation among humans vary

widely from three times a day to oncein two or three days. However, when aperson can only defecate at longintervals such as a week, the person

suffers from constipation, a problem ofdefecation.


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HEALTHY EATING HABITS

Malaysia is one the fortunate countries inthe world where a great variety of food is

available in large amounts.

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