Category Zoology

Why do doctors take your temperature?

The body temperature of a human being is an indication of his physical condition, so that an abnormally high or low temperature is generally a sign that something is wrong.

     The normal temperature is usually given as 36.90 C. (98.40 F.), but as the body temperature varies throughout the day, anything between approximately 36.70 C. (OR 98.10 f.) and 37.20 C. (or 99.00 F.) may be taken as normal.

    For instance, the temperature rises after a large meal, during hot weather and after violent exercise. Your temperature is at its lowest at night when you are asleep.

    Control of body temperature is exercised by a centre in the brain which ensures that a balance exists between heat production and heat loss. A raised temperature is often the sign of bacterial or virus infection. It may be due to heatstroke, to certain types of brain injury or disease or to shock.

     A very high temperature, or fever, may begin with a “rigor” (an attack of shivering and cold), in which the whole body may tremble uncontrollably and the teeth chatter. Although at this stage the skin feels cold and clammy, the temperature within the body is raised. Soon the skin becomes hot and dry, pulse and breathing rate are speeded up and there is a feeling of exhaustion, aching muscles. Headache, thirst and perhaps delirium and loss of the sense of time.

    Finally this stage is succeeded by profuse sweating and a gradual relief of the symptoms.

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When does blood congeal?

Blood congeals when a part of the body is wounded. If it failed to congeal the injured person would die from loss of blood.

    The congealing, or coagulation of the blood, is the first step towards healing a wound. It closes the wound and builds a scaffold for new tissue by means of a chemical process in the plasma, the fluid part of the blood. In this process the platelets (small cellular bodies in the blood) produce thromboplastin. This changes fibronigin, a protein in the blood, into fibrin. Finally a spongy network of fibrin connects the edge of the wound and prevents the loss of any more blood cells. Often, a scab is formed over the wound as a protection.

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Why do we become sea-sick?

We become sea-sick because our balancing organs, the labyrinthine portions of the inner ear, are disturbed by out-of-level movements, by sudden turning movements, or by sudden changes in movements in a straight line, either horizontal or vertical.

       The ear has three semicircular canals, filled with fluid and set on different planes in the ear. When sudden movements occur, each canal is affected differently. As a result, nerves in the canals send conflicting information to the brain, so giddiness is likely to occur.

        Nowadays, seasickness comes under the general heading of motion sickness a name invented by Sir Frederick Banting in 1939, which include the discomfort people feel while travelling in all kinds of vehicles.

    Sea-sickness may vary with individuals from slight uneasiness to complete prostration. The symptoms are pallor, cold sweating, nausea and vomiting. People who have lost their ear labyrinths because of disease do not become seasick. Others become resistant to it. We say they develop their “sea-legs”, but it would appear to be an adjustment of the central nervous system rather than the organs of balance. Some people find it helpful to keep their gaze firmly fixed on a steady object.

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Why do we have brains?

The brain directs and coordinates movements and reflexes, registers sensations and is the supreme nervous organ by which man acquire knowledge and the power to use and adapt it. It shapes our personalities, and without it we would be more helpless than the tiniest human baby.

       There are three main parts of the brain: the forebrain (or cerebrum), the midbrain and the hindbrain. They have the consistency of soft jelly and are protected by three membranes (meanings), a tough outer envelope called the dura and a water fluid (cerebrospinal fluid) which acts as a support and a cushion. The brain is connected to the spinal cord, and its surface is highly convoluted.

      The cerebrum which forms nearly nine-tenths of the brain is divided into two halves (hemispheres). Generally the left half of the cerebrum controls the right half of the body, and the right half of the cerebrum controls the left half of the body. Some areas are connected with the special senses of man, but there are so-called “silent areas” which scientists believe are connected with memory and the association of ideas. The thalamus, a mass of grey matter which is buried in the cerebrum, is the source of instinctive feelings and emotion.

    The midbrain is concerned with eye-movements, while the hind-brain contains the nerve cells responsible for breathing, heart action, and digestive juices and so on. The cerebellum, a part of the hindbrain, plays an important role in the execution of the more highly skilled movements.

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Where does a leech feed?

      Leeches, which are rather slimy worms and vary in length from an inch to several inches, have two suckers, a big one at the rear and a smaller one at the mouth end. They have powerful muscles which enable them to expand and contract their bodies.

      This makes them excellent swimmers. They can also use their suckers to crawl on the land in tropical Asia, the island of the Pacific and the Indian Ocean, there is a particularly vicious and dreaded species of land leech which enters the breathing passages of animals, gorges on the animal’s blood and swells so that it cannot escape.

     Aquatic or water leeches cling to fishes, turtles and shell fish. Some leeches feed on earthworms and frogs’ eggs. Others live on the larvae of insects and even on the microscopic life on the floor of the pond.

     Leeches have been used in medicine from early times until quite recently to draw blood from a patient.

What is a salamander?

A salamander is amphibian-an animal that lives both on land and in the water. It is a lizard like member of a group of back-boned creatures between fish and reptiles. This class includes frogs and toads. Like fish and reptiles, the salamander is cold-blooded.

      It was anciently believed that the first salamander was born out of the court of a fire and that the so called fire salamanders were unaffected by heart. In fact, the salamander is active usually only in the cool of the night, when it hunts worms, slugs and insects.

     The salamander, which grows up to about 11 inches long, is attacked by few enemies, as its skin glands are poisonous. But the European water snake is not affected by the venom and frequently asked the salamander its prey.