Category Zoology

‘Pins ins and Needles’ is referred to the tingling sensation we feel in our hands, feet, arms or legs when the blood begins to circulate in those areas after being impeded for some time. For example, when we sit with our legs curled up in one position for a long time and then try to stand up, we sometimes get the feeling of numbness as if one of our leg had ‘fallen asleep’. As the blood begins to flow again, the familiar tingling sensation occurs due to the change. But why do we get this tingling sensation?

We know that the blood flows freely through the blood vessels in our body, just as water flows freely through a stretched hose. Imagine what would happen if you bent the hose! Water would only trickle through. Similarly blood is the transport system of our body and performs two important functions. It supplies food and oxygen to different parts of the body as well as collects the poisonous wastes. When a recession occurs in the flow these poisonous wastes accumulate and block the nerve cells from carrying messages from the foot to the brain. This results in the feeling of numbness. Again when the leg is stretched, the blood starts flowing again and this change causes the tingling sensation. 

          The potential threat of a population explosion made family planning a national issue in many developing countries. In the developed countries the changing role of a family to meet the demands of a hectic industrial life necessitated small families. Hence several birth control techniques were developed over the years.

          The sex glands of a man, the testes, produce sperms while the sex glands of a woman, the ovaries, produce eggs or ova. When the male sperm joins the female ovum inside a woman’s body, a new life begins to grow. Birth control methods are used to prevent this meeting of the egg-cell with the sperm. These have been divided into three broad categories: Natural methods, Spacing methods and Terminal methods.

          Natural methods are those which do not involve the use of any device or drug. These are: (i) rhythm or safe period method and (ii) coitus interruptus.

          The rhythm method is based on the avoidance of sexual intercourse during the ‘unsafe period’ or the days when there is a possibility of the egg cell meeting the sperm. Women normally produce one egg cell every month. If the male sperm do not enter the vagina at that time, then pregnancy can be avoided. The safe period is counted basing on the days of the regular menstrual cycle of 28 days. Eleven days before the expected date of commencement of menstruation are considered safe; the eight days preceding these eleven days are full of risk then again eight days before this risk period are considered safe. Since the regularity of monthly period varies from woman to woman, so also the safe period. 

Continue reading “What are the different methods of birth control?”

            It is a matter of common experience that we shiver in winter if we are not wearing woollen clothes. And even if we want to stop it we cannot do much about it. Do you know why do we shiver on a cold day? 

            Physiologically speaking, shivering is an automatic movement of the muscles. When we shiver our muscles tighten and relax very quickly over and over again. Each time when our muscles contract, the muscle cells burn more food for energy and as a result of this, heat is produced. Thus shivering is a mechanism of the body which helps to keep it warm. It keeps the body temperature from falling beyond a certain point. This is a process in which our muscles work hard and keep the body warm. Sometimes, shivering is not enough to warm us up properly. We, therefore, often jump up and down and flap our arms on cold days. Thus extra uses of muscles produce more heat in the body.

            We wouldn’t shiver if we do some exercise or play a physical game. Physical activities make our muscles work hard and warm up the body. Shivering, in fact, does the same job without any exercise.

          EEG is the abbreviated form of electroencephalography which is a bio-medical process of recording the minute electric currents produced by the brains of human beings and other animals. The instrument for detecting and recording the electric current produced by the activity of the brain is called electroencephalograph. This was discovered by Hans Berger of Jena (Germany) in 1929 and found to have important clinical significance in the diagnosis of brain diseases.

          The brain constantly generates minute electrical currents even during sleep and in deep coma. These can be recorded from the skull’s surface by means of small wires called electrodes attached to the scalp. In normal persons they have an electrical potential of about 100 microvolts. So to make such recordings the doctors use a machine that has about 20 equally-spaced electrodes which are attached to the scalp’s surface in accordance with the standard positions adopted by the International Federation of EEG. Electrode positions are carefully measured so that subsequent recordings from the same person can be compared with the earlier ones. The electrodes are connected to an amplifier which amplifies the voltages to 1,000,000 times. The current then moves an electromagnetic pen that makes a graph on a chart paper. 

Continue reading “What is Electroencephalography (EEG)?”

            Emotion can be described as an excited state of mind or moving of the feelings in reaction to certain thoughts or stimuli. They can be positive as well as negative. The positive emotions are those which make a person happy. Love, happiness, pleasure, pride and success etc. can provide the basis for positive emotions. On the contrary, negative emotions make a man sad and unhappy and they are manifested in the form of anger, fear, hatred, disappointment etc. The negative emotions are basically harmful and sometimes lead to self-destruction.

            Many doctors believe that the newborn babies or neonates have no emotions at all. They learn them through their environment and socialization just as they learn to walk and talk. A young child, for example, may not be afraid of a growling dog or a snake unless it bites the child. Then he may develop a fear, as he gradually learns about their aggressiveness and avoid them in future. 

            Emotion is sometimes considered as opposite to reason or rationality when it results from passions. This case arises when actions are more spontaneous and performed without a reasonable control over one’s mind at that time. The emotional activity is an expression of one’s past learning and experiences.

            Emotions cause many chemical changes in the body which is a part of the body’s defence mechanism. For example, if a person is in a dangerous situation, his adrenal gland sends a hormone called adrenaline into his blood stream. As the blood travels, the adrenaline makes his heart beat faster, sending more blood to his brain and muscles. At the same time, more sugar enters his blood to give his body extra energy to handle the situation.

            The emotional disturbances can cause various physical ailments like asthma, stomach ulcers, rheumatoid arthritis (stiffness of the bone joints) and hypertension. Hysteria is also a result of emotional disturbances. In this disorder, the patient feels that some part of his body is paralyzed though the organ is actually not paralyzed and the patient loses control over him and becomes repetitive in his actions.

            Emotion is viewed in a context of subjective experiences, expressive behaviours and the activity of the nervous system which we call the neurochemical activity. 

          A reflex action is an automatic nervous action in which a stimulus causes a rapid response. For example, if a person accidentally touches a hot stove, he would immediately jerk away his hand before he has time to think about it. In this case, the hot stove is a stimulus, and the jerk is the response. 

          Reflexes, such as the ‘pupil reflex’ are quite common. When a bright beam of   light hits a person’s eye, his pupil automatically becomes smaller. And if the light is taken away and his eyes are shaded, the pupil returns to its normal size. Here the light acts as the stimulus and the reaction of the pupil is the eye’s response.

          Reflex actions are of two types: unconditioned and conditioned. Unconditioned reflex actions are exemplified by the reflex tests of the physician. When a doctor tests a person’s reflexes, he makes sure that the different parts of his nervous system are functioning properly. One reflex action frequently tested is the knee-jerk action. In this the doctor lightly strikes an area just below the knee cap with a rubber hammer. This causes the lower part of the leg to jerk upward suddenly. This is because the nerve impulses move via the spinal cord directly to the leg muscle and are not controlled by the brain. Such reflex actions are called ‘unconditioned reflex actions’. These take place without any special learning or experience. 

          The conditioned reflex actions are a result of particular internal or external stimuli. Such conditioning process was popularized by the Russian physiologist I.P. Pavlov and his associates. Pavlov believed that whenever there was a response to a particular stimulus, a kind of reflex was established in the brain. However, most psychologists today believe that the mechanism of learning is much more complicated than explained by him.

          Now the question arises what causes a reflex action? To explain in simple terms, four basic processes are involved in a reflex action. These are: reception, conduction, transmission and response. The stimulus is received by receptors (nerve endings). Energy from the stimulus is changed into nerve impulses and carried from the receptor to the central nervous system. The nerve impulses are then sent to the motor nerves. The motor nerves control muscle action, causing the muscles and glands to respond (act). Most reflex actions, however, are much more complicated and also involve other parts of the nervous system like brain.

          More than 90% of all the actions are performed by man’s nervous system and reflex actions.