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The Amazon rainforest, located around the river Amazon, is the largest expanse of the world covered with dense tropical forests.  The Amazon rainforest covers an area of more than 5, 5 million square kilometers, which is about 60 percent of the entire continent of South America. Amazon rainforest spreads out in 9 countries, including Brazil, Bolivia, Ecuador, Colombia, Peru. Intertwined with dense and high vegetation, impenetrable, the Amazon rainforest is still unexplored completely, and yet disappears from the face of the earth. Into the inaccessible areas, where constant moisture and dusk rule, there are very few people, mostly Indians, who live by hunting, fishing , gathering fruit and rubber. The average temperature in the Amazon ranges from 25 to 28 degrees Celsius (77 – 83 F). There are no seasons, and drought days are rare. Humidity is very high, about 50 percent during the day and at night is coming up to 100 percent. The average annual rainfall ranges from 15...

How far can you throw a ball? About 60 or 70 feet (18 or 21 meters)? Why doesn't it travel any farther? Gravity limits the distance. When you throw a ball, it rises into the air, but the earth's gravity soon pulls it back to the ground. To launch a spacecraft, we somehow have to overcome gravity. How do we do this? We do it by speed. Think of yourself throwing the ball. If you throw the ball gently, it goes slowly, and it doesn't travel very far. But the harder you throw it, the faster it travels, and the farther it goes. You are starting to beat gravity by speed. If you could throw the ball faster and faster, it would go farther and farther before it dropped back to the ground. Eventually, you could make it go so fast that its curve, as it fell, would be the same as the curve of the earth's surface. In other words, it would stay the same distance above the surface. It would then be in orbit around the earth. To launch your ball into orbit you would ha...

What is a Proton? Protons are positively charged (+1), quite the opposite, as the electric charge of electrons (-1). The number of protons in the nucleus determines the total amount of positive charge in the atom. In electrically neutral atom, the number of protons and electrons is equal, such that positive and negative charges are balanced to zero. Proton is very small, but it is quite massive in comparison with other particles that make up matter. Mass of the proton is about 1840 times the mass of the electron. What is a Neutron? Neutrons are about the same size as protons, but slightly heavier. Without the neutrons, the repulsion between the positively charged protons would cause the nucleus to apart. Consider an element of helium, which consists of two protons in its nucleus. If the core does not contain neutrons, it will be unstable due to the electrical repulsion between protons. The nucleus of the element helium requires one or two neutrons to be stable. Most atoms ...

Most electrical appliances have wires attached to them. The wires carry an electric current around a complete pathway called an electric circuit. Some appliances need more electric current than others before they will work. The amount of electric current depends on how much electricity is flowing along the wires. How can we measure the amount of electric current? We could try counting the number of electrons that pass along the wire each second. But this wouldn't be easy! There are a huge number of electrons traveling along most electric wires. About 3 million million million electrons flow through a flash bulb every second! To make it easier, we measure the flow of electric current in amperes.  The word ampere comes from the name of the French scientist Andre Ampere, who invented a way of measuring electric current. We usually say amp instead of ampere.  One amp is equal to about 6 million million million electrons every second. So a flashbulb would have a curre...

There are two humors, the aqueous humor and the vitreous humor, both of which help to maintain the shape of the eyeball. The aqueous humor is a transparent liquid that fills the region between the cornea at the front of the eye and the lens. The vitreous humor is a transparent, jelly-like substance that occupies the region between the lens and the retina at the back of the eye. The vitreous humor is present from birth and remains virtually unchanged throughout an individual's life. Vitreous humor disorders Specks may occur in the vitreous humor caused by the degeneration of its cells with age. This is a normal occurrence. The presence of specks does not noticeably impair vision. Occasionally, a hemorrhage into the vitreous humor may occur, usually caused by an injury. A hemorrhage may also occur in diabetes mellitus, arteriosclerosis, or retinitis. A hemorrhage may be serious and a physician should be consulted.

There are two humors in the eyes, the aqueous humor and the vitreous humor, both of which help to maintain the shape of the eyeball. The aqueous humor is a transparent liquid that fills the region between the cornea at the front of the eye and the lens. The vitreous humor is a transparent, jelly-like substance that occupies the region between the lens and the retina at the back of the eye. How is the aqueous humor produced? The aqueous humor is constantly secreted by the ciliary body around the lens, so there is a continuous flow of the humor from the lens area to the eye's front chamber. The aqueous humor is kept at constant pressure by a compensating leakage in the angle between the outer rim of the iris and the back of the cornea. Function of Aqueous Humor The aqueous humor carries nutrients and facilitates the exchange of gases (oxygen and carbon dioxide) in the cornea and other tissues of the eyeball that have no blood supply. Aqueous Humor Disorders Several dis...

Histamine is a chemical that is normally present in tissue mast cells and certain white blood cells circulating in the body. Histamine is involved in the immune system, digestion system and central nervous system. Histamine as a neurotransmitter communicates important messages from the body to the brain, and it is also a component of stomach acid, which is what helps us in breaking the food in our stomach. Large amounts of histamine are released in response to an injury or in conjunction with an antigen-antibody reaction, such as an allergic reaction. Histamine causes contraction of pulmonary smooth muscle (bronchocon-striction) that results in an asthma-like disorder. Histamine also dilates small blood vessels and increases their permeability. These actions are responsible for histamine headache and the typical wheal-and-flare allergic skin reaction. Histamine is a potent stimulant of acid secretion in the stomach. Epinephrine and H1-receptor blocking antihistamines reverse t...

Human Eyes are part of the organ of sight, with almost perfect sphere shape, about one inch in diameter. Each eye is protected at its back and sides by the bones of the skull and at the front by two lashed eyelids. The outer covering of the eye, the sclera or "white," is both protective and structural.  Light penetrates the sclera only at the front of the eye, where the outer surface bulges into the transparent cornea, a delicate structure overlaid with a thin defensive membrane, the conjunctiva. Under each upper eyelid is a tear-secreting lacrimal gland whose constant activity keeps the conjuctiva moist and free from germs. Light entering the eye passes through the cornea and then through a watery fluid, the aqueous humor, in the front of the eye.  Behind the fluid is the iris, a ring of muscle with a central hole, the pupil.  The cornea focuses light rays so that they pass through the pupil.   The iris determines how much light enters the eye....

Endomorph, ectomorph and mesomorph are three hypothetical body types first proposed around the turn of the century to explain certain aspects of personality. This system of categorization was established during the 1940's, by William Herbert Sheldon, Jr. (November 19, 1898 - September 17, 1977). Ectomorph The endomorph's body is characterized by a round head, a round and large abdomen, large internal organs, rather short arms and legs with slender wrists and ankles, and a large proportion of body fat. Endomorph is a person characterized by a predominance of structures developed from the endodermal layer of the embryo. Such a person is inclined to be soft-skinned and fat; some also ascribe to endomorphs the characteristics of being easy-going and good-natured. Mesomorph The mesomorph has the body of a classical athlete: a square head, a large heart, broad and muscular chest and shoulders, arms and legs with powerful muscles, and little body fat. Ectomorph The ...

Cell Membranes enclose the entire cell, the nucleus, and all the organelles. The membranes hold the cell and each of its parts together. Most membranes consist of a double layer of a fatty substance called phospholipid. Proteins occur at various points and extend to different depths within the double layer of phospholipids. Only needed materials can enter the cell and its parts because of the structure and chemical composition of the membranes. 

The Cytoplasm is the entire cell except the nucleus. Proteins are made in the cytoplasm, and many of the cell's life activities take place there. Many tiny structures called organelles are located in the cytoplasm. Each has a particular job to do. These organelles are called mitochondria, lysosomes, the endoplasmic reticulum, centrioles, and Golgi bodies. Mitochondria - What is mitochondria? Mitochondria are the power producers of the cell. A cell may contain hundreds of mitochondria. These sausage-shaped structures produce almost all the energy the cell needs to live and to do its work. L ysosome function and definition Lysosomes are small, round bodies containing many different enzymes, which can break down many substances. For example, lysosomes help white blood cells break down harmful bacteria. Endoplasmic Reticulum Endoplasmic Reticulum is a complex network of membrane-enclosed spaces in the cytoplasm. The surfaces of some of the membranes are smooth. Others ...

Bell's palsy is paralysis of the muscles of the face, caused by acute malfunction of, or damage to, the nerve that supplies them. An attack frequently occurs without apparent cause. Symptoms of Bell's palsy Facial features lose their symmetrical arrangement, and the mouth droops at one corner. Paralysis of the muscles results in loss of control over saliva or tears, so that the patient may dribble or appear to  cry. Bell's palsy treatment It is important that a physician is consulted immediately because swift treatment with corticosteroid drugs may help. Many patients recover spontaneously; about 70 percent recover completely within 4 to 6 weeks, and about 20 percent make a partial recovery. Surgery to the affected nerve may restore partial nerve function.

Behavior therapy , often used interchangeably with behavior modification, is a form of psychological treatment based on learning theory. Behavioral therapists believe that maladaptive behavior and thinking is learned or conditioned and, therefore, can be unlearned. New, more constructive behavior can then be taught or shaped. Little attention is paid to intrapsychic or unconscious forces. Instead, behavior therapy focuses directly on overt behavior. Behavior therapy has been found to be particularly effective with anxiety and fear, using techniques such as relaxation training, desensitization, and assertiveness training. To increase the probability of success, behavioral therapists also attempt to remove the reinforcing consequences of maladaptive behavior as well as to reward appropriate behavior.

Decubitus ulcer or also known as Bedsore or pressure sore , is a skin and tissue injury caused by impaired blood supply and tissue nutrition. It is caused by prolonged pressure over bony prominences due to lying too long in the same position. The parts of the body most likely to be affected are the pressure areas: the bone at the lower end of the spine (the sacrum), the buttocks, and the heels. The shoulder blades and elbows may also develop these sores. The area first becomes slightly red with cracked skin, which turns dark blue before ulcerating as dead tissues disintegrate. Pressure ulcer prevention Patients who cannot move themselves must be moved every few hours. Patients must not sit in bed or in a chair for long periods. The patient should be lifted, not slid, when moved. The skin is to be kept clean and dry. Bedclothes must be kept clean, dry, and free from creases. Additional protection can be given to the pressure areas by using foam pads and real or artificial ...

Bedbug (Cimex lectularius or cimex hemipterus) is a small blood-sucking insect that can infest bedding and bite humans or other animals. The insect is red-brown, oval, flat, and wingless. B ed bug bites symptoms Bedbug bite is painful and causes swelling, itching, and sometimes infection. It may transmit relapsing fever. B ed bugs treatment The bite can be treated with a corticosteroid cream or other anti-inflammatory preparation. The infested bedroom furniture should be disinfected.

Addison's disease is a rare medical condition that results from insufficient production by the adrenal gland of several vital hormones. It is caused by a disorder of the adrenal glands themselves or by the failure of the part of the pituitary gland that produces ACTH, the hormone that stimulates the adrenal glands. Addison's disease is most common during middle age. Stopping steroid medications suddenly and without medical supervision can produce a life-threatening Addisonian crisis. Addison disease symptoms: Common symptoms of Addisons disease may include weakness and dizziness caused by low blood pressure, vomiting, diarrhea, anemia, loss of weight, and a brownish color of the skin and the membranes lining the mouth. It is difficult to diagnose the condition because it is slow to develop and because there may be occasional, temporary improvements in the patient. Tests can reveal the low amount of adrenal hormones in the blood and a disturbance in the balance of salts i...