Exercise Facts

  • When you exercise, your muscles have to work much harder than normal, so need much more oxygen and glucose (a kind of sugar) from the blood.
  • To boost oxygen, your heart beats twice as fast and pumps twice as much blood, and your lungs take in ten times more air with each breath.
  • To boost glucose, adrenalin triggers your liver to release its store of glucose.
  • If oxygen delivery to muscles lags, the muscles fill up with lactic acid, affecting your body for hours and sometimes causing cramp.
  • The fitter you are, the quicker your body returns to normal after exercise.
  • Aerobic exercise is exercise that is long and hard enough for the oxygen supply to the muscles to rise enough to match the rapid burning of glucose
  • Regular aerobic exercise strengthens your heart and builds up your body’s ability to supply extra oxygen through your lungs to your muscles.
  • Regular exercise multiplies muscle fibers and strengthens tendons.
  • Regular exercise helps to reduce weight when it is combined with a controlled diet.

Oxytocin Challenge Test

Oxytocin Challenge Test (OCT) is done in the hospital to help determine how well the baby will undergo the stress of labor. The OCT is also known as the Contraction Stress Test.

Oxytocin is a medication that causes uterine contractions. While reclining on a 45-degree angle, the woman is given oxytocin intravenously until she has contractions 3 to 4 minutes apart for a full half-hour. At the same time, the heart rate is electronically monitored to check the effect of the contractions on the baby. If the results are positive—that is, the fetal heart rate appears normal during the stress of the contractions—the doctor may recommend a wean birth, since the baby may not be able to tolerate the stress of labor. If the results are negative—that is, the heart rate remains normal during the contractions—the baby will most likely do well during labor.

When taking the OCT, avoid lying flat on your back. This can cause your blood pressure to drop, decreasing oxygen to the baby and possibly causing the appearance of fetal distress on the monitor.

Sweating

The skin is liberally supplied with intricate network of sweat glands. They are referred to as the Eccrine Sweat Glands, and there are several million them all over the body. Although all parts of the skin are copiously supplied, they are concentrated mainly on the forehead, in the armpits on the palms of the hands and soles of feet.

The sweat glands are part of system’s heat regulatory mechanism: They react almost immediately to the stimulus of heat, which operates via the brain. It is essential that the body temperature be maintained between certain critical boundaries. Any rise above normal is quickly compensated through the sweating system. When these glands are stimulated fluids pour onto the skin surface where they dry almost instantly. This immediately draws heat from the body, and the temperature falls. A very delicate balance exists to keep body temperatures operatic, within the prescribed limits in this manner.

The fluid excreted is mainly water, however, it contains some salt (sodium chloride) and other chemicals called electrolytes. The volume of fluid that is perspired can reach high levels. On an average two hour period this can reach 10,000 ml. To give an indication of the amount, 5 ml approximately equals one teaspoonful so 500 ml is roughly equal to one glass, and 10,000 ml is about equal to 20 pints! On extremely hot days, or if prolonged hard physical activity is being undertaken, the daily volume can rise still further.

In areas where the humidity is high the sweat does not tend to evaporate from the skin surface. Therefore very uncomfortable feeling occurs. The feeling is sticky as salty water accumulates. Sweat may trickle down the face, under the arms and promote greater discomfort. It is not so common in hot, dry regions such as inland regions where humidity is appreciably lower than most coastal locations. Cramps commonly follow if sweating has been very profuse. This is due to the excessive loss of sodium chloride from the system, and is often relieved by an increased intake of salt in the diet.

A serious Sebaceous (oil-secreting) gland, Dermi Gland cells that secrete sweat cross-sections through the sweat gland known as cystic fibrosis, is often diagnosed by the excessive salt content of the patient’s sweat. There is a defect in sweat-gland function, but this is only an outward sign of an internal disorder. Many people are troubled by excessive sweating. It can be triggered by hot weather or emotional stress. Even in cool weather, many people perspire abnormally. Some find their feet sweat so heavily that new footwear is required every few weeks, because shoes fall apart so quickly with the continuing moisture! For these persons, abnormal sweating becomes a major problem.

Sweating Treatment

When facetious remarks are made about the disability it does little to assist people with this problem, and little help is available. The following ideas may be of some assistance:

Temperature control: working in an area subject to regular air-conditioning may assist, but this is not the answer to the problem on a permanent basis.

Frequent bathing: this gives temporary relief, and helps to avert body odor that may be a common and embarrassing problem. But the sweating usually recommences soon afterwards, and this is a temporary measure only.

Antiperspirants: these are aimed at narrowing the ducts of sweat glands by chemical means. They assist mild cases only. They are of little value for the excessive perspiration.

Vitamin C: some find that large daily doses of vitamin C (ascorbic acid)-1,000 mg once or twice dailysometimes helps.

Further Treatment

Simple remedies rarely (if ever) cure this disorder. Most finally arrive at the doctor’s surgery for advice.

The professional lines available are:

Sympathectomy: this is a form of treatment offering a complete and permanent result. The nerve that supplies the sweat glands is surgically severed. The result is a complete absence of sweating in the offending part(s) supplied from that time forth. Some believe this is a radical measure for a simple symptom, but patients treated often prefer this. Some complain of being “too dry” following the operation. This operation is performed by a surgeon or neurosurgeon. Surgical removal of the skin and sweat glands is also being successfully used in some suitable patients.

Removal of sweat glands: Surgical removal of a triangular area of skin in the armpit is often effective. The application of Aluminium Chloride Hexahydrate (if available) periodically painted on locally is recommended. The daily washing of the armpits with a rough rag for at least five minutes helps.

Other methods

There are IT medicaments of value for this. The anticholinergics and others expected on theoretical grounds to cure must be given as too high for convenience. They produce side reactions that may be unacceptable and they are not generally used for this purpose. Relaxation is often successful in the long-term.

Of course, if you want to learn much more about the skin diseases as well as most other body illnesses, we can only advise you to check with some of the other information we have prepared. Probably the best reference guide of all is Volumes 3-5 of Family Medical Care, which covers the whole spectrum of conditions and medical care of family illnesses. These are available from the same publishers of this book.

Sunburn

We have already dealt with sunburn, but I think it should have a further brief mention here. Agreed?

Agreed, for it is very important and may be classified as an accident. In Chapter 13, “Strange Conditions of the Skin” we set out the salient items about sunburn and the treatment. I wish to reemphasize that children’s skin is prone to burning, so take adequate precautions against sunburn. Many children brown up quickly also, but when it is soft and tender and lilywhite, it may burn rapidly, often within minutes of exposure to the hot sun. Never leave a baby or child in the sun unattended. Sun kicks are great for babies, but do remember that while they are kicking away probably in a birthday suit, they could be silently and stealthily sustaining sunburn. Also, remember that the ultraviolet rays of the sun bounce back from large masses of light-colored expanses, such as clouds, beaches, open paddocks and fields. Sunburn may occur in any of these situations, often when the child is oblivious to it all.

What’s the best treatment?

Apart from avoidance in the first case, application of cool packs is the best starting point. Repeat these often, using small folded towels placed in icy water wrung out, then placed over the burnt places. Plenty of fluids, ideally fresh fruit juices, will replace fluid loss. Add some vitamins. Paracetamol elixir is best for fevers and pain reduction. The dose will usually be printed on the label. Do not place skin applications on sunburn, for they may sensitize it, and seldom help. Avoid them, despite what your friends may say. Apply ultraviolet screeners to protect against sunburn, but after the event, they are useless.

Heart Failure Symptoms

Usually the left side of the heart is affected first, and this invariably leads to failure in the right side, the portion of the circulation that delivers blood through the lung system.

Breathlessness

This is an early and cardinal sign. A cough is common, and frequently the material brought up is tinged with blood. This is termed hemoptysis. This is the typical set of symptoms.

Breathlessness is referred to clinically as dyspnoea. All levels are experienced. In the initial stages of failure, “effort dyspnoea” is the earliest indication, coming on only with severe exertion. However, as cardiac efficiency decreases, so dyspnoea increases. The threshold of effort needed to bring on breathlessness gradually lowers, so a gradual lessening of physical activity will produce symptoms.

Progressively, it becomes noticeable mainly toward evening, and the simple effort of undressing may produce it. Sleep at night often brings relief, and in the morning a good start may be made to another day. With advancing disease, breathlessness even at rest may take place, and simple efforts involved in speaking, gesturing or making any movement may precipitate dyspnoea. The respiratory movements are shallow, quick and obviously troublesome, and accompanied by much effort. They are never sighing or deep, and are not relieved if the attention is suddenly diverted to something else.

With the progression of time, the patient develops a condition called orthopnoea. This means that breathing difficulty occurs at night during sleep. When the patient is in the recumbent position, a build-up of fluid occurs in the lungs. This reduces the ability to secure adequate oxygenation of the blood.

This may cause the sufferer to awaken with dyspnoea. Often he or she will find it better to sleep propped up with pillows, or even to remain propped up in an easy chair instead of lying flat.

This nocturnal difficulty may suddenly get out of hand, and a condition called paroxysmal cardiac dyspnoea (also commonly called cardiac asthma) may follow. This is an extension of orthopnoea, and it is frequently a striking feature late in heart failure.
The symptoms may be of any degree of severity. Most attacks occur at night, and lying in the recumbent position appears to be the immediate aggravating factor. The inadequacy of the heart as a pump allows a build-up of fluid in the lungs, aggravated by the gravitational flow of blood to the lungs in this position.

This is more common after a hard day’s work and a large evening meal. The patient will suddenly awaken about 2 am with a sense of suffocation and dyspnoea. Gripped with an intense desire to get out of bed, he or she invariably does this at once, and going to the window, throws it open, endeavoring to inhale deeply in an effort to get adequate oxygen into the lungs. There is a sense of constriction in the chest; coughing is common, and often blood-stained fluid is brought up. Breathing may become extremely difficult, and a wheeze, very much like the wheeze of the asthmatic, occurs. The patient is anxious, tense and drawn, and often fears for his or her life. The skin may be pale and cold. Often, the standing position in itself assists in mechanically bringing relief.

A disorder named pulmonary edema is a more severe form of this condition. Often there is pain over the chest, breathing is noisy, and there is coughing and the production of much blood-stained, watery fluid. Sometimes a bluish tinge occurs as inadequate oxygen enters the circulation. Mental confusion can frequently follow from inadequate oxygenation of the higher centers in the brain. This constitutes a medical emergency, and prompt treatment is essential. In advanced cases, a typical breathing pattern develops, referred to as Cheyne-Stokes respiration. Each breath commences as a very shallow inspiration. These gradually increase in depth and speed, until they are forceful and deep. The blood becomes oversupplied with oxygen, and there is then a temporary lull, or gradual reduction in the inspiratory movements. Advanced cases are often associated with irregularities of the heartbeat, and abnormal sounds in the chest and heart.

Edema

This is the accumulation of fluid in dependent parts, a common occurrence in heart failure, and indicates that the right side of the heart is reducing in efficiency.

This was once commonly referred to as dropsy, and is a typical symptom of a failing heart. Swelling takes place in dependent parts of the body, the ankles being the most common. But it may occur low down in the back, in the so-called sacral area, about the genital region and in the upper thigh areas.

This is merely another indication that the heart is not pumping all the blood that is being delivered to it and blood is building up on the venous side.

If a person is standing all day, the fluid tends to accumulate about the ankles. Toward the end of the day (or at any time of day in more advanced cases), the ankle disappears altogether. If a finger is pushed into the tissue and then removed, an indentation occurs that may take several minutes to smooth out. It is a bit like poking a finger into a piece of putty. The tissue underneath is saturated with fluid, and indentations from outside pressures remain. Wearing tight shoes or socks will also leave their pattern indented on the swollen part.

Usually, with rest at night, and the feet elevated, the edema tends to vanish by morning, but gradually develops as the day progresses.

Often the degree of edema is a good indication as to the effectiveness of therapy, and lets the doctor know if the treatment is working. Fluid tends to be removed, and the heart often improves in Palpitation (premature beat). Incomplete heart block Typical electrocardiogram (ECG) tracings, made by an electrocardiograph and used in diagnosing irregularities of heart action efficiency with the administration of certain drugs.

Sometimes other internal organs are similarly filled with fluid. The circulation to the intestinal region and liver may be involved. For this reason, the liver may be swollen, and the vessels of the bowel tense and engorged. Appetite may be depressed due to this.

In more advanced stages, fluid tends to seep out into the general abdominal space, accumulating by gravity in the lower regions. This is known as ascites, and is usually a serious indication of advanced cardiac disease.

Other Heart Failure Symptoms

Many other symptoms may be present. Fatigue and exhaustion may occur. Sometimes, a bluish tinge of the lips and extremities and other skin surfaces may indicate inadequate oxygenation of the general blood supply. This will be aggravated if anemia is also present.

The doctor will frequently order various tests that give an indication of the severity of the disease. X-rays will often show enlargement of the chambers of the heart, as they distend and become less efficient. The lungs may show marked congestion, as excessive amounts of fluid accumulate there. The electrocardiogram will also indicate that the heart is not operating efficiently.

Heart Failure Treatment

There are wide variations in the clinical picture of heart failure. It commences as a disorder without symptoms, and gradually (or rapidly) develops into a more serious condition.

The sooner any underlying cause can be found and corrected, the better are the chances of stemming the deterioration. Often other concurrent disorders are present, and can be diagnosed and corrected.

These may include diseases of the heart valves, thyroid disease (thyrotoxicosis, a potent troublemaker), beriberi (often from excessive alcoholic intake) or anemia. However, once established, general principles of treatment follow. These are basically aimed at resting the disordered heart muscle. Physical and mental rest can only assist in allowing the heart to carry out its actions as efficiently as possible without undue outside interference of an artificial kind.

Next, the efficiency of the heart must be improved as much as possible and the tendency to accumulate fluid and salts must be actively treated by the use of fluid-removing tablets, commonly the oral diuretics, now in wide use.

Rest

This is important. The amount required will depend on the extent to which the disorder has advanced. If bouts of cardiac asthma are recurring, then with each attack bed rest may be required for a few days.

Physical and mental rest alleviates anxiety and worry; physical repose reduces the amount of work the heart muscle must perform each day. Treatment of the cardiac patient is under the care of a physician.

There is always a fear that doctors keep well in mind. With prolonged rest in bed, and lack of movement, there is an increased risk of clots forming. The calf muscles are a favorite site for this condition, referred to as deep venous thrombosis. Apart from causing marked swelling of the affected limb, a piece of clot may break off and block a major segment of the lung, and this is a serious but ever-present possibility. Often a compromise is made between bed rest and partial ambulation or sitting on a chair.

Diet

This is given consideration. With rest, there is less need for large meals, and a 4200 kJ (1000 calories) a day food intake is adequate in the initial stages of therapy. Often the patient does not feel hungry, so that a reduction in food intake is seldom a hardship. Meals must be small but attractively served, for there is always a psychological overlay and the patient needs a certain amount of nutrition. Smaller meals mean that the heart works less in coping with this.

Attention is given to the salt content of food, and a low-salt regimen is sometimes recommended. It is suggested food be served without the addition of salt. Often salt-free food is unpalatable. In the past, many diets have been advocated with severely restricted salt routines. Today, with the extreme efficiency of the fluid-eliminating medication (the oral diuretics), not so much attention is being paid to the need for salt restriction.

There is no need to restrict fluid intake. Some doctors (but not all) believe that there is little reason to eliminate alcoholic beverages from the routine purely for reasons of cardiac health. But on moral grounds, and on the grounds of general health, abstinence may well be justified.

Smoking

Tobacco use in all forms must be restricted or preferably entirely stopped. The adverse effects of the drugs contained in tobacco smoke and their serious effect on the heart and blood-vessel system arc too well documented for smoking to be permitted. It is best to explain this in a kindly way to the patient, who may suffer adversely in the early stages from such deprivation.

White Blood Cells

Apart from red cells, there are the white cells or leucocytes. Some are produced by the bone marrow and are called granulocytes, because they have varying coloured granules dotted throughout them when stained ready for examination under the microscope.

There are three kinds of granulocytes. One form, called the neutrophil, has the capacity of engulfing and devouring foreign particles in the blood. They are termed phagocytes, and this capacity is necessary to combat infections. The germs are simply gobbled up by the cell, digested and destroyed. Incidentally, the white cell dies also – a case of giving its life to help keep the owner alive. This is seen in the formation of pus.

There are two other types of granulocytes: the eosinophils (that stain a bright red) and the basophils (that turn blue on staining). The eosinophils are associated with allergic reactions, being present in higher numbers in patients with allergies (such as asthma and hay fever) and parasitic infections. Basophils are involved in inflammatory and allergic reactions.

So much for the red cells. They seem very important. Now what about the white cells you spoke of? These are also extremely important. They are really the fighting force of the body. Their task is essentially one of protection. In time of need they are mobilised, and they vigorously attack any unwanted foreign invaders that may harm the system. There are many different kinds, but they are essentially there for the same purpose.

If infection occurs at any part of the system, the white cells congregate, and actively attack the germs. They actually approach them, roll over them and totally encompass them in a weird process called phagocytosis. When this has happened, the cell usually dies, with the germ inside it. This is how pus forms – it’s really a collection of millions of dead white cells and dead germs.

In times of infection, huge numbers of white cells are manufactured rapidly by the system, and thus the “white cell count” of the blood increases, as the doctors say. This condition is called leucocytosis – the leucocyte being the official name of the white cells. Sometimes there is a swing in the opposite direction, and there are insufficient white cells. This is called leucopenia, and may be dangerous if an infection strikes.

Where do the cells come from?

There are many different places around the body where they are manufactured. The softish material in the centre of the large bones of the limbs called marrow is an important one. Others are made in the lymph glands, and two large organs located in the upper part of the abdomen called the liver and spleen are also associated with the cells. A gland in the upper part of the chest of children, called the thymus, also produces certain types of white cells. Another solid part of blood are the platelets, microscopic particles that play an important part in blood clotting

First Aid in Drowning

Treatment prolonged lack of oxygen from being submerged under water leads to cardiac arrest, so it is important that rescue breathing or CPR (either mouth-to-mouth or mouth-to-nose ventilation) be started immediately – even in the water if necessary.

  • Call 911 for medical assistance and a quick transfer to the nearest emergency center.
  • If you know what happened prior to the accident, tell the rescue workers, particularly if head and neck injuries are likely (as would be the case if the child was diving when the accident occurred). Keep the child warm, especially if he was in cold water. Wrap him in towels or a blanket until medical personnel arrive.

Drowning Prevention

Studies show that 70 percent of drowning accidents could be avoided if self-closing, self-latching doors were installed in homes and on gates in the fences around pools. Sturdy, childproof pool covers and alarms on doors leading to the pool area – or even an alarm that sounds when someone enters the water – are also appropriate safety measures. Parents need to teach their children the importance of swimming only when supervised and the necessity of life jackets when boating. Older children and adolescents should be warned explicitly of the risks of alcohol and/or drug consumption while swimming.

When young children are around water, they must always be supervised by an adult. Parents and teens should strongly consider becoming certified in CPR. Poolside telephones are helpful because they allow adults to answer the phone while continuing supervision. They also can speed the process of calling for help if an accident occurs.

Chances of Surviving Drowning

The chances of surviving submersion are not significantly affected by the type of water (salt, fresh, or pool water with chemicals). How long a child can survive without oxygen depends on many other factors, including age, previous health, the water temperature, and the speed and effectiveness of the rescue effort. Children under age five have an advantage because of a nerve reflex that causes the heart to slow down and blood to be directed to the brain and heart. Younger children usually survive if submersion lasts less than 3 minutes and may survive a submersion lasting up to 10 minutes if the water temperature is 50° to 60°F (10° to 15°C). In general, cold water temperatures improve survival chances.

ADHD Symptoms

Inattention and Distractability

An ADHD child cannot stay focused on any task that requires continuous attention, especially schoolwork. He may daydream or become distracted by any sight or sound in his vicinity. Completing an assignment can require much effort, but he is likely to misplace the final product between home and school. He cannot remember a sequence of directions: “Take out the trash, feed the bird, and pick up your clothes before you take your bath” might result in one or at most two of the commands being completed. The others will be forgotten or jumbled.

Hyperactivity

Perpetual motion has traditionally been the most striking trademark of ADHD, but in fact it is prominent in only about 30 percent of children who have the disorder. Experts now divide children with ADHD into subtypes based on their most overt characteristic: lack of attention, hyperactivity, or a blend of the two. While difficulty with attention may not be apparent until the child enters school, hyperactivity makes an impact on everyone in his world from the time he is young.

Some parents are aware that “something is different,” from the first days of life with their demanding baby who later turns into a turbocharged toddler. Most parents of small children wish they could acquire some of the energy of their offspring, but the hyperactive child is in a different league, living every day at top speed. Many children with ADHD also have volatile modal. Whether they are joyful or angry, everyone in earshot will hear about it. Just as rapidly, these feelings seem to pass as the child forgets the episode and moves on to some-else.

Impulsiveness

The child with ADHD has a little timer. He cannot wait his turn, stand in line, follow directions, or keep his hands off whatever he supposed to touch. He talks before he thinks, acts before he analyzes, and leaps before he looks. As a result, he suffers more than a few battle wounds and fractures.

ADHD has been given many names over the US including Minimal Brain Dysfunction and Hyperkinetic Reaction of Childhood. The following causes have been related to ADHD: brain damage, birth trauma, poor parenting, lack of discipline, food additives, sugar and pure wilfulness. The best understanding at present is that the primary basis for ADHD is neurochemically subtle inherited malfunction of the intricate passing messages between cells in the brain. So far, no spool medical finding, blood test, or X-ray is sensitive CTIOU to detect the abnormality, although a doctor’s evaluation is important in ruling out other causes of the troublesome behavior.

The child with ADHD exhibits difficulties in many areas of life (home, school, playground), but not a beam to the same degree, and parents may be confused or frustrated by some of the inconsistencies. Certain activities – usually ones that are highly intense such as games – can hold his interest, at times to a striking degree. In some one-on-one situations, he may act quite normal. This variability is actually very typical with ADHD, but it gives the definite impression that the child’s lack of attention is simple laziness or that impulsivity is wilful defiance.

One of the greatest challenges of parenting an ADHD child is discerning how much of a particular behaviour arises from biology and how much from consciousness. As the child grows older, the causes may blend. For example, extreme difficulty with schoolwork, which requires prolonged concentration and mental effort, them to dislike and then eventually to refusal to participate.

Repeated rejection by others because of behavior hest control may push him toward more deliberately excessive acts.

Global Warming Facts

  • Global warming is the increase in average temperatures around the world. This increase has been between 0.3°C and 0.8°C over the 20th century.
  • Most scientists now think that global warming is caused by human activities, which have resulted in an increase in the Earth’s natural greenhouse effect.
  • The greenhouse effect is the way that certain gases in the air – notably carbon dioxide – trap some of the Sun’s warmth, like the panes of glass in the walls and roof of a greenhouse.
  • The greenhouse effect keeps the Earth pleasantly warm – but if it increases, the Earth may become very hot.
  • Many experts expect a 4°C rise in average temperatures over the next 100 years.
  • Humans boost the greenhouse effect by burning fossil fuels, such as coal, oil and natural gas that produce carbon dioxide.
  • Emission of the greenhouse gas methane from the world’s cattle has added to the increase in global warming.
  • Global warming is bringing stormier weather by trapping more energy inside the atmosphere.
  • Global warming may melt much of the polar ice caps, flooding low-lying countries such as Bangladesh.
  • Recent observations show global warming 14 could be much worse than we thought.

Kiwi Facts

  • There are three species of kiwi, found only in New Zealand. All are flightless birds that live in burrows. The female dwarf cassowary, or moruk, is an extremely dangerous bird and will attack anything that comes near its nest with its 10-cm long claws. The three species of cassowary live in rainforests in New Zealand and northeastern Australia. Largest of its family is the brown kiwi, which is about 55 cm long and weighs up to 3.5 kg.
  • Only the kiwi has nostrils at the end of its beak.
  • The kiwi is the national symbol of New Zealand, appearing on stamps, coins and banknotes.
  • Cassowaries in Australia are known to eat the fruits of at least 75 different types of tree.
  • The female cassowary mates with several males, laying 6-8 eggs each time. The males care for the young.
  • About 1200 years ago there were probably 12 million kiwis in New Zealand. Today there are only 70,000.
  • The nocturnal kiwi’s good sense of smell helps it to find worms, insects and spiders in the ground at night.
  • A kiwi lays the largest eggs for its size of any bird – each egg weighs 25% of its body weight. Females lay up to 100 in a lifetime.

Facts About Air Pressure

  • Although air is light, there is so much of it that air can exert huge pressure at ground level. Air pressure is the constant bombardment of billions of air molecules as they zoom about.
  • Air pushes in all directions at ground level with a force of over 1 kg per sq cm – that is the equivalent of an elephant standing on a coffee table.
  • Air pressure varies constantly from place to place and from time to time as the Sun’s heat varies.
  • Air pressure is measured with a device called a barometer in millibars.
  • Normal air pressure at sea level is 1013 mb, but it can vary from between 800 mb and 1050 mb.
  • Barometers are used to detect changes in air pressure. The first barometer was invented by Evangelista Toricelli in 1644.
  • In this satellite picture, a spiral of clouds indicates that stormy weather in a depression is heading for California, USA.
  • Air pressure is shown on weather maps with lines called isobars, which join together places of equal pressure.
  • High-pressure zones are called anticyclones; low-pressure zones are called cyclones, or depressions.
  • Barometers help us to forecast weather because changes in air pressure are linked to changes in weather.
  • A fall in air pressure warns that stormy weather is on its way, because depressions are linked to storms.
  • Steady high pressure indicates clear weather, because sinking air in a high means that clouds cannot form.