Human System: Nervous System

The nervous system is an organ system containing a network of specialized cells called neurons that coordinate the actions of an animal and transmit signals between different parts of its body. The nervous system is divided into two main systems, the central nervous system (CNS) and the peripheral nervous system. The spinal cord and the brain make up the CNS. Its main job is to get the information from the body and send out instructions. The peripheral nervous system is made up of all of the nerves and the wiring. This system sends the messages from the brain to the rest of the body.

Human System: Skeleton System

The human skeleton system consists of both fused and individual bones supported and supplemented by ligaments, tendons, muscles and cartilage. It serves as a scaffold which supports organs, anchors muscles, and protects organs such as the brain, lungs and heart. The biggest bone in the body is the femur in the upper leg, and the smallest is the stapes bone in the middle ear. In an adult, the skeleton comprises around 14% of the total body weight, and half of this weight is water.

Fused bones include those of the pelvis and the cranium. Not all bones are interconnected directly: there are three bones in each middle ear called the ossicles that articulate only with each other. The hyoid bone, which is located in the neck and serves as the point of attachment for the tongue, does not articulate with any other bones in the body, being supported by muscles and ligaments.

If you are interested to find out more about the individual bones and their functions, click here.

Human System: Muscular System

So what do muscles do? 

Muscles move cows, snakes, worms and humans. Muscles move you! Without muscles you couldn't open your mouth, speak, shake hands, walk, talk, or move your food through your digestive system. There would be no smiling, blinking, breathing. You couldn't move anything inside or outside you. The fact is, without muscles, you wouldn't be alive for very long! 

Do I have lots of muscles? 

Indeed. On average, probably 40% of your body weight is in muscles. You have over 630 muscles that move you. Muscles can't push. They pull. You may ask yourself, if muscles can't push how can you wiggle your fingers in both directions, back and forth, back and forth? The answer? Muscles often work in pairs so that they can pull in different or opposite directions. 

How do muscles move? 

The cells that make up muscles contract and then relax back to original size. Tiny microscopic fibers in these cells compress by sliding in past each other like a sliding glass door being opened and then shut again. The cells of your muscles use chemical energy from the food you eat to do this. Without food, and particular kinds of nutrients, your muscles wouldn't be able to make the energy to contract! 

Some muscles are known as "voluntary" -- that is, they only work when you specifically tell them to. Do you want to say something? Or swing a bat? Or clap your hands? These are voluntary movements. Others, like the muscular contracting of your heart, the movement of your diaphragm so that you can breathe, or blinking your eyes are automatic. They're called involuntary movements. And how do any of these muscles move? Through signals from your nerves, and, in some cases, your brain, as well. 

Can you hurt muscles? 

Yup. If you hear someone say that they "pulled" a muscle, they have, in fact, torn a muscle in the same way that you can tear a ligament or break a bone. And, like these other living body parts, with a little help, they generally mend themselves. 

Factoids:

• You have over 30 facial muscles which create looks like surprise, happiness, sadness, and frowning.
• Eye muscles are the busiest muscles in the body. Scientists estimate they may move more than 100,000 times a day!
• The largest muscle in the body is the gluteus maximus muscle in the buttocks.

Human System: Respiratory System

Our cells need oxygen to survive. One of the waste products produced by cells is another gas called carbon dioxide. The respiratory system takes up oxygen from the air we breathe and expels the unwanted carbon dioxide. The main organ of the respiratory system is the lungs.

The nose and trachea
Breathing in through the nose humidifies the air. Nose hairs help to trap any particles of dust. The warmed air enters the lungs through the windpipe, or trachea. The trachea is a hollow tube bolstered by rings of cartilage to prevent it from collapsing.

The lungs
The lungs are inside the chest, protected by the ribcage and wrapped in a membrane called the pleura. The lungs look like giant sponges, since they are filled with thousands of tubes, branching smaller and smaller. The smallest components of all are the air sacs, called 'alveoli'. Each one has a fine mesh of capillaries. This is where the exchange of oxygen and carbon dioxide takes place.

The breathing muscles
To stay inflated, the lungs rely on a vacuum inside the chest. The diaphragm is a sheet of muscle slung underneath the lungs. When we breathe, the diaphragm contracts and relaxes. This change in air pressure means that air is ‘sucked’ into the lungs on inhalation and ‘pushed’ out of the lungs on exhalation. The intercostal muscles between the ribs help to change the internal pressure by lifting and relaxing the ribcage in rhythm with the diaphragm.

The exchange of gas
The blood containing carbon dioxide enters the capillaries lining the alveoli. The gas moves from the blood across a thin film of moisture and into the air sac. The carbon dioxide is then breathed out. On inhalation, oxygen is drawn down into the alveoli where it passes into the blood using the same film of moisture.



Summary

The main organ of the respiratory system is the lungs. Our lungs breathe in oxygen and breathe out carbon dioxide. This exchange of gases is vital to life. Breathing depends on the diaphragm, a sheet of muscle slung beneath the lungs inside the ribcage. Common problems of the respiratory system include asthma, bronchitis, emphysema, hayfever, influenza, laryngitis and pneumonia.

For more information on the respiratory system, click here.

Human System: Circulatory System

The circulatory system (also called the cardiovascular system) is made up of group of organs that transport blood and the substances it carries (oxygen, nutrients, etc) to and from all parts of the body. The organs of circulatory system consist of vessels that carry the blood and a muscular pump, the heart, that drives the blood.

Of the vessels, the arteries carry blood away from the heart; the main arterial vessel, the aorta, branches into smaller arteries, which in turn branch repeatedly into still smaller vessels and reach all parts of the body. Within the body tissues, the vessels are microscopic capillaries through which gas and nutrient exchange occurs (see respiration). Blood leaving the tissue capillaries enters converging vessels, the veins, to return to the heart and lungs. The human heart is a four-chambered organ with a dividing wall, or septum, that separates it into a right heart for pumping blood from the returning veins into the lungs and a left heart for pumping blood from the lungs to the body via the aorta.

Human System: Digestive System

Digestion is the mechanical and chemical breaking down of food into smaller components that can be absorbed into a blood stream. Digestion is a form of catabolism: a break-down of larger food molecules to smaller ones.

System: Plant System - An Overview of the Plant System.

System refers to a whole made up of several parts or members. This set of interacting or interdependent entities form an integrated whole to perform a task.

The video clip below provides an overview of the plant system.

Plant System: How do plants store food?

Plant leaves produce food in the presence of sunlight, water and carbon dioxide. The plants use the food and store the excess within itself. Different plants store food (sugars/starch) in their roots (turnips, carrots, sweet potatoes, etc), stems (water chestnuts, gingers, yams, potatoes, etc), leaves, fruits and even seeds. 

Please refer to your textbook (pages 12 to 15) in addition to the following notes.

(Click on the links to learn more about the terms.)

A storage organ is any part of a plant specifically modified for storage of energy (generally in the form of starch), nutrients or water in order to be used for future growth.

A storage organ is any part of the plant in which excess of energy (generally in the form of starch, sugars, lipids or protein), nutrients or water are stored in order to be used for future growth (usually in biennial or perennial plants). In the first year biomass is added to the storage organ. Afterwards some of the biomass from the storage organ is returned to the rest of the plant. 

Storage organs often grow underground, where they are better protected from attack by herbivores. Underground storage organs are also characteristic of geophytes. They evolved as a mechanism for plant survival through adverse climatic conditions, and as a result, geophytes in their natural habitats are capable of perennial life cycles. In the geophyte - especially during temperature extremes and prolonged drought - the aerial portions die back, leaving only the storage organ in the soil until the temperature or water availability is appropriate for above-ground growth. This stage in geophyte development is often referred to as a dormancy period or resting stage. But the storage organ is never physiologically dormant even when aerial growth is halted. It continues to change and constantly senses its environment like a biocomputer.

In common parlance, underground storage organs may be generically called roots, tubers, or bulbs, but to the botanist these are specific, technical terms, which apply only more narrowly:

• True roots:
	▫	Tuberous root
	▫	Storage taproot
• Modified stems:
		Corm
		Tuber
		Rhizome
		Pseudobulb
		Succulent stems
• Modified  leaves
		Bulb
		Succulent leafs
		Leaf petioles (e.g. celery, onion)
• Seeds:
		Cotyledons
		Endosperm
• Others:
		Storage hypocotyl (caudex)
		Axillary buds (e.g. Brussels sprouts)
		Inflorescences (broccoli, cauliflower)
		Etc.

In some plants the storage organ are short-lived and serve as regenerative organ bearing a bud or buds (e.g. a tuber); in that case the plant dies back in the resting season, except for the underground storage organ with the buds, later utilised for regrowth; afterwards old tubers decay and new ones are formed. In addition some plants produce smaller reproductive storage organs (bulbils, small tubers, etc); plants growing from them resemble in morphology and size seedlings.

(extracts from CACTUS ART Nursery)

Plant System: Capillary Action Experiment (Part 2)

Look at the video clip below to have a look at the effects of food colouring on cut flowers. Have you linked this effect with the importance of having clean water in our natural environment yet?

Plant System: Capillary Action Experiment (Part 1)

The effects of capillary action allows for amazing effects in flowers and other plants. Before you observe the experiment below, think about capillary action why it is important to keep our (water) resources clean.

Plant System: Capillary Action

Capillary action, or capillarity, is a phenomenon where liquid rises in a narrow space such as a thin tube, or in porous materials. This effect can cause liquids to flow against the force of gravity. This behaviour of water allows plants to take in water through the roots and up the stems to be distributed throughout the plant.

Plant System: Plants need light.

Plants need light for photosynthesis. What would plants do in order to get as much light as possible? We have discussed three main ways:

1. Growing leaves to ensure large surface area.
2. Growing tall to reach the canopy where there is most light.
3. Spreading its branches wide to increase light catchment.

There is one more way which plants will behave in order to catch more light. Watch the clip below and see if you can guess what it is...

Magnets: Uses of magnets – from the everyday to the industries.

People use magnets to keep notes on refrigerator doors. They are an essential part of technology items such as speakers, motors and computer hard disks. Credit cards carry account information on a magnetic strip. Here are some short descriptions on how they care used:

Door Latch

Magnets are a simple, reliable way to latch doors on refrigerators and cabinets.

Speakers

From tiny ear buds to stadium PA systems, every speaker has a magnet in it. The stronger the magnet, the better the sound quality.

Toys and Games

Many familiar toys such as the Woolly Willy drawing game use magnets. Some construction toys use magnets to securely attach parts.

Motors

DC motors have a set of permanent magnets and electromagnets inside. When connected to a battery, the electromagnets repel the permanent magnets and make the motor spin.

Refrigerator Magnets

Refrigerator magnets are used for everything from notes to jokes to the pediatrician's phone number.

Credit Cards

Credit cards have a strip of magnetic material on their backs. Account data are recorded on it in a special, machine-readable format.

Transportation

Magnets are now used in the very advanced technology of public mass transportation known as the Maglev (from the words magnetic levitation) train. Watch the video clip to see how the magnetic system works.

Magnets: Magnetic materials - let's find out!

How to conduct an experiment that aims to find out which materials can be attracted to a magnet.

Magnets: How do magnets behave when placed near each other?

Around a typical bar magnet - or any magnetised object (like the Earth, for example) - there are lines of magnetic flux. These are said to flow away from the north pole and re-enter at the south pole.

These field lines become evident if iron filings are sprinkled over a sheet of paper underneath which there is a bar magnet. Their direction can be plotted using a small 'plotting compass'. The needle aligns with the N-S field (flux) lines and the needle follows the same pattern as revealed by the iron filings.

When two magnets are brought close to each other, the flux lines from both magnets interact. If these flux lines are flowing in the same direction, they will link up and the magnets will attract each other. If they are flowing in opposite directions, they will produce a repulsive force and push away from each other, (often taking the magnets with them!) The force between them depends on the separation distance and the flux density (magnetic strength) of the magnets used

Magnets: How do magnets behave when allowed to move freely?

A magnet can be allowed to move freely. This is usually done by suspending it on a thin thread or floating on water and allowed to rotate and swing freely. The magnet will then interact and align itself to the Earth's magnetic field. However, this is provided that there are no other magnetic or electromagnetic influences.

Magnets: How to make a magnet using the stroking method?

Magnetic materials can be magnetized by stroking. When existing magnet is moved from one end of the item to the other repeatedly in the same direction, the magnetic object becomes a temporary magnet.

Magnets: How to make an electromagnet?

An electromagnet in its simplest form, is a wire that has been coiled into one or more loops, known as a solenoid. When electric current flows through the wire, a magnetic field is generated. It is concentrated near (and especially inside) the coil, and the magnetic field lines are very similar to those of a magnet. The strength of the magnetic field of the electromagnet are proportional to the number of loops of wire. That means, the more loops there are, the stronger the magnetic field. In addition, if it is wrapped around a magnetic material, such as an iron nail, then the overall result may be several hundred to thousand times increase in the field strength.

Magnets: Magnetic fields

Magnetic fields surround magnetic materials and electric currents and are detected by the force they exert on other magnetic materials and moving electric charges.

Magnets: magnetism

The term magnetism is used to describe how materials respond to a magnetic field; to categorize of if a material is magnetic. Magnetic materials, like iron and steel are also known as ferrous materials. Materials that are not affected by magnetic fields are known as non-magnetic or non-ferrous materials. They include copper, aluminium, water, gases, and plastic.

Magnets: Magnets

A magnet is a material or object that produces a magnetic field. This magnetic field is invisible but is responsible for properties of a magnet: a force that pushes/repels or pulls/attracts on other magnetic materials like iron and/or other magnets.

A permanent magnet is an object made from a material that is magnetized and creates its own magnetic field. An everyday example is a refrigerator magnet used to hold notes on a refrigerator door. Materials that can be magnetized, which are also the ones that are strongly attracted to a magnet, are described as magnetic, ferrous, ferromagnetic and ferrimagnetic. These include iron, nickel, cobalt, some rare earth metals and some of their alloys and some naturally occurring minerals such as lodestone.

Some ferromagnetic materials can be magnetized by a magnetic field but do not tend to remain magnetized when the field is removed, they are described as soft. Permanent magnets are made from ferromagnetic materials that stay magnetized and are described as hard.

An electromagnet is made from a coil of wire which acts as a magnet when an electric current passes through it, but stops being a magnet when the current stops. Often an electromagnet is wrapped around a core of ferromagnetic material like steel, which enhances the magnetic field produced by the coil.

Physical Property: Buoyancy - sink or float?

When an object floats, it can stay on the surface of a liquid by itself. Different solids, liquids, and gases can float. For example, both cork and oil will both float on the surface of water. Some gases, such as helium, can rise, or “float” in the air. When an object sinks, it moves down with gravity. Different solids, liquids, and gases sink. For example, a solid coin will sink in a cup of water. Gases that are heavier than air, such as propane and butane, can sink as well.

Displacement explains why objects sink or float. Displacement occurs when you place something in a fluid, or any substance that flows, and it moves the fluid out of its way. You can watch displacement at work when you drop an object in a cup of water and the water level rises. Gravity pulls the object down, but the difference in pressure above and below the object causes an upward force. The object pushes the water out of its way, making the water rise. An object will sink if it weighs more than the water it pushes away, and an object will float if it weighs less than the water it pushes away. The Greek mathematician Archimedes discovered that the amount of water displaced by an object depends on the mass of that object. Mass is the amount of matter in a substance, and dense objects have more mass than less dense objects. Dense objects that do not displace much water will sink, while less dense objects that displace a lot of water will float.

Shape can also help an object float. A ball of clay will sink, but a canoe shape made from the same amount of clay can float because it displaces more water. A canoe shape can push more fluid out of its way in relation to its weight. The amount of air inside of an object can also help it float. Boats can float despite the heavy and dense materials used to build them because of the large amount of air inside the hull. Hollow objects, such as table tennis balls or an empty plastic bottle, are able to float better than solid objects.

Many children believe that heavy objects sink and lighter objects float. Some heavy objects like boats float, while relatively lighter objects such as coins sink. Why do you think these objects sink and float? Think about it and describe observations you have made of sinking and floating objects.

 

Physical Property: Buoyancy - displacement.

Did you ever notice that when something floats in water, part of it is actually under water? As it sinks (even a little bit) it pushes away the water until that amount of water weighs the same as the thing that is floating.

If the thing you try to float is too heavy, it cannot push away enough water to be the same as how much it weighs. If that happens, the thing will sink.

Ask an adult to help you with an experiment (a test) that can show you how this works: Float a small plastic boat in water and notice how deep the boat sinks when it is empty. Then add pennies to the boat and watch how the boat sinks deeper and deeper the more pennies you add. The pennies make the boat weigh more and more. If you add enough pennies, the boat will sink deep enough so that water reaches the top and then the whole thing sinks.

Blow up a balloon and float it on water. It will not sink very far because it is not very heavy. If you look really close, where the balloon touches the water, you can see a little dent in the water under the balloon. That's the place where the water is pushed out of the way. If you try this test with a ball that is exactly the same size as the balloon, the ball will sink deeper before it floats. Because the ball is heavier than the balloon, it has to push more water out of the way before it can float.

It is not just how heavy something is that makes it float or sink. Look how heavy real boats are -- and they still float. Floating or sinking has to do with the amount of water pushed out of the way. Any boat will sink if you put enough stuff inside it -- just like your experiment showed. Small, heavy things like a marble or a rock cannot float because they cannot push enough water out of the way to be the same as how much they weigh..

So remember, anything that floats weighs the same as the water pushed out of the way.