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| HUMAN BIOLOGY Home |
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Human Biology comprises of more than 30% of Zoology portion in all national and state level PMTs. It forms an important component of B.Sc. (Human Biology) at AIIMS and in AFMC interview. |
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Must for National level entrance exams like CBSE, AIIMS, AFMC, BHU, CMC, UGET Manipal And State level entrance exams like WB-JEE, Bihar CECE, Orissa JEE, K-CET, Delhi PMT (incl. VMMC), Punjab-PMT, J & K –CET etc. |
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Q. What are Phatom Limbs ? Ans. Phatom Limb Pain (PLP) is a serious condition that occours when a person who has lost a part of their body through amputation , trauma or loss of nervous connections in an appendge, preceives that the limb is still there and experiences sensations coming from this area. It was first described in 1866 by S.Weir Mitchell, an American neuologist. :: Approximately 80% of amputees have some phantom limb sensations. :: The phantom sensation can occur right after the amputation or many months or years later. :: Phantom pain are not typically experienced by children under the age of 4. :: Intensity, duration , severity , quality and chroncity all are variable and are not static from patient to patient. :: Many phatom limb sensations occur after some injury to the site of the amputation. Thus , a person who was born without a limb, and did not experience any type of phatom sensation could suddenly find themselves experiencing one if some type of injury occurred to the stump. :: Phatom limbs help with the use of prosthetics. It's easier to use some type of prosthetic device if there are phantom sensations associated with the limb. Q. What is Cardiac skeleton ? Ans. It is a dense fibrous connective tissue mass that supports meocardial cells. It inculdes the trigona fibrosa, the membrane part of the interventricular septum and the annuli fibrosi which surrounds the atrioventricular and arterial foramina. It provides the attachment to the cardiac muscle and keeps the cardiac valves competent. In old age the cardiac skeleton may be calcified to some extent. Q. Why clotting does not takes place inside the vessels? Ans. Because blood is fluid while in circulation. While circulation inside the vessels - 1. Smoothness of the endothelium lining prevents rupture of platelet and formation of thromboplastin.This also prevents activation of intrinisic factors . 2. Speedy flow prevents accumulation of fibrin threads , if formed. 3. Presence of monomolecuar layer of negatively charged proteins adsorbed to the inner surface of endothelium repels the clotting factors . 4. Presence of anticoagulant -heparin prevent coagulation by inhibiting the action of active thromboplastin. Q. Why alcohol intake increases urination ? Ans. Because alcohol decreases the level of vasopressin . This lowers reabsorption of water and increases loss of water in urine .Therefore beverages having a high content of alcohol causes excessive urination and dehydration. Q. Why a convict dies instantly when hanged ? Ans. Brain stem is very sensitive. When a prisoner is hanged the noose cord breaks the atlas (1st vertebrae) as a resultant of which the pointed end (odontoid process which extends upwards from its body and projects through the odontoid fossa of the atlas) of the axis (2nd vertebra)pierces the brain stem leading to instant death. Q. Why Acetycholine decreases heart beat and Adrenaline increases ? Ans. Because Ach released from the vagus nerve endings hyperpolarizes the SA nodal cells. As a result rate of impulse generation is reduced , leading to bradycadia or decreased heart beat.Reverse happens with adrenaline. Q. What is Double Bohr effect ? Ans. Double Bohr effect refers to the situation in the placenta where the Bohr effect is operative in both the maternal and foetal circulations. The increase in pCO2 in the maternal intervillous sinuses assists oxygen un loading . The decrease in pCO2 on the foetal side of the circulation assists oxygen loading . The Bohr effect facilities the reciprocal exchange of oxygen for carbondioxide. The double Bohr effect means that the oxygen curves for maternal HbA and foetal HbF move apart (i.e.in opposite directions). Q. Why scrotum is called as temperature regulator of tests ? Ans. Scrotum is a place where test begins to desend during the third month with a concomitant (existing or occuring together ) shortening of gubernaculum. The descent of testis is under the control of testosterone and gonadotopin. Proper descent is essential for complete fertility because sperm needs low temperature by about 20C from normal body temperature (370C) to mature than the abdominal temperature. Therefore if the testis do not descend from the abdominal cavity to scrotum the heat/higher temperature (which is incompatible to spermatogenesis) destroy the sperm producing seminiferous tubule result ing in sterility. Heat does not harm the leydig inerstitial cells. The scrotal sacs have dartos muscles which constantly contract or relax the loose scrotal skin.This helps to keep the testicular temperature at 350C. Failure of testis to descend in scrotum is called cryptorchidism . Q. How are damaged muscles repaired ? Ans. Skeletal muscle cells are associated with a type of stem cell knows as satellite cell. These cells are believed to aid in recovery of muscle fibres from damaged and can contribute their nuclei to replace and supplement the nuclei of the damaged cells. This occurs in response to the "microtears" produced by strenuous exercise and results in increased production of protein and myofibrils. IGF-1. (Insulin Growth Factor ) is released locally as a result of exercise and is believed to play a major role in attracting the satellite cells to the site of the injury . Q. How is body temperature regulated by sweat gland? Ans. Heat and cold receptors are located in the skin. When the body temperature rises,the hypothalamus sends a nerve signal to the sweat-producing skin glands, causing them to release about 1-2 liters of water per hour , cooling the body. The hypothalamus also causes dilation of the blood vessels of the skin , allowing more blood to flow those areas,causing to be convected away from the skin surface. When body temperature falls, the sweat glands constrict and sweat production decreases. If the body temperature continues to fall, the body will engage in thermiogenesis, or heat generation, by raising the body's metabolic rate and by shivering. |
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