Examville.com - Anatomy - Organ System Of Human Body,maintenance Of Life

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Maintenance of life The human beings share certain unified and basic characteristics like maintenance of boundaries by integumentary system due to which internal environment remains distinct from the external environment It also protects internal organs from drying out and being invaded by foreign agents. Some functional characteristics are as follows : (i) Cellular Structure. Each living being is a complex entity which is formed of one or more cells. (ii) Organisation. It has an organization, that is, the living being consists of several components which cooperate with one another for the well being of the whole organism. (iii) Energy. It constantly receives energy not only to perform various activities of the body but also to overcome entropy or tendency to randomness. (iv) (v) (vi) (vii) (viii) (ix)

(x) (xi) (xii) (xiii) (xiv) (xv)

Homeostasis . It shows homeostasis or ability to maintain perfect internal environment through self regulated system. Response. It is able to recognise and respond to different types of external and internal stimuli. Growth. A living being is able to grow in size and attain maturity. Reproduction. Life comes from pre-existing life. Young-ones grow and become mature. They develop the faculty to produce young-ones of their own type. Assimilation. It is able to obtain raw materials from outside and convert them into protoplasmic constituents. Metabolism. A living being carries out numerous chemical processes in an organized and controlled fashion. They constitute metabolism. Metabolism has two types of reactions, catabolism (break-up reactions. e.g. cellular respiration) and anabolism (build-up reaction e.g. formation of glycogen by glucose). Healing and Repair. Living beings are able to repair and heal broken and injured parts. Disposal of Wastes. Wastes generated during metabolism are regularly disposed off by living beings. Movements. Living beings show movements of their parts. Some are able to move from place to place. This phenomenon is called locomotion. Adaptation. It is in perfect harmony to its surroundings and shows adaptability to varied environments. Variations. It possesses variations and has the ability to evolve with time. Life Span. Every living organism has a definite life span of birth, growth, maturity, senescence and death.

SURVIVAL NEEDS

Homoeostasis – A Function of Regulatory System (Gk. Homoeos – like, stasis – standing) It is the maintenance of favourable internal conditions despite changes in the external environment through a self regulating mechanism. Regulatory system coordinates internal function in such a way as to transport substances throughout the body and supply optimum nutrients to individual cells. Favourable internal conditions help the cells to continue their metabolic activities at an optimum level or physiological equilibrium despite unfavourbale external condition. Some examples of homeostasis are. 1.

During exercise or running up a flight of stairs, the heart starts beating much faster than the normal of 72 times/minute in order to supply extra blood to muscles and tissues which are made to perform extra work. After some rest the heart rate returns to normal. 2. Vigorous exercise raises body temperature. It is brought back to normal through sweating. Sweating in summer is also meant for bringing down the body temperature that has a tendency to rise due to higher external temperature. Homeothermy in Humans. Human beings are endothermic or homeothermic. Normal body temperature is maintained at 37°C or 98.6°F. Human body has a thermostat and sensors like the one present in a room air conditioner. In air conditioner, the thermostat is set at a particular temperature (say 21°C ). Whenever, the room temperature rises sufficiently above this point, the sensor attached to thermostat detects the change and activates the compressor (effector machine) of the air conditioner. The machine will continue to work till the room temperature reaches below 21°C. Human body has two types of thermoreceptors, warm receptors immediately below the skin and cold receptors slightly deeper in the dermis. Thermostat (= set point) is present in hypothalamus (Barbour, 1912) which also possesses thermoreceptors for warmth and cold. In warm environment, the cold receptors are inhibited. Warm receptors pick up the sensation and send the message to thermoreceptors of hypothalamus. The internal thermoreceptors also monitor the temperature changes in blood passing through hypothalamus. If required, hypothalamus sends messages to effectors that dilate superficial blood vessels and release sweat. Dilated blood vessels allow diffusion of body heat. Evaporation of sweat causes cooling of body. As the temperature regulation is on the negative side for cooling, the control system is called negative feedback mechanism. It keeps the body temperature within normal range. In a cold environment, the warm receptors are inhibited. The cold receptors pick up the sensation and send it to thermoreceptors of hypothalamus. The same also detect the change in temperature of the blood passing through hypothalamus. Hypothalamus sends information to superficial blood vessels for constriction and skeletal muscles for undergoing contractions. Constricted superficial blood vessels prevent loss of body heat. Contrations of skeletal muscles bring about shivering. It generates heat for raising body temperature. As temperature regulation is on the positive side for warming the control system is called positive feedback mechanism. (i) Glucose level of blood is controlled by two pancreatic hormones, insulin and glucagon. Whenever glucose is present in excess quantity, it is removed in liver and muscles to produce insoluble glycogen through insulin mediated polymerization or glycogenesis. As soon as glucose content of blood decreases, glycogen of liver is hydrolysed to form glucose (glycogenolysis). It is mediated by glucagon. (ii) ADH is antidiuretic hormone formed by hypothalamus but released by posterior pituitary in response to presence of water deficiency in blood and excess water in nephric filtrate passing through distal convoluted tubules and collecting tubules. The hormone brings about reabsorption of water from nephric so that loss of water is minimized. When water is in excess in blood, ADH (= vasopressin) production is reduced so that dilute urine is allowed to pass out.