Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Chapter 27 - Maintaining the Internal Environment 1. Homeostasis – regulating the internal environment: Animals maintain their internal conditions relatively constant despite changes in the outside environment. Bigger changes in the environment result only in small changes in the organism. Mostly homeostasis is achieved by negative feedback mechanism. In a negative feedback the result of a process stops that process. For example, regulation of body temperature, regulation of fluids and solutes in blood, secretion of hormones. Ectotherms can absorb heat from sunlight to raise body temperature (lizard) and Endotherms lose heat by evaporation of water, sweating (mammals). Glucose level in blood is controlled by Pancreas with the help of liver. When glucose level in blood increases above the upper limit, pancreas secretes Insulin. Insulin causes greater absorption of glucose by liver and muscles by opening special gates for glucose absorption. When blood sugar level in blood falls below the lower limit, pancreas secretes Glucagon. It causes the breakdown of glycogen in liver and muscles and release of more glucose into blood. 2. Diabetes mellitus causes abnormally high blood levels of glucose. Diabetes mellitus type-1 is caused if pancreas cannot secrete enough insulin which can be on gaining lot of weight. It can be cured by taking insulin pills or injections. Diabetes mellitus type-2 is caused if the receptors for insulin are modified. This is caused even when normal insulin is secreted in the body. It cannot be cured by taking pills. Diabetes mellitus type-2 is mostly associated with obesity. 3. Osmoregulation: is the homeostasis of water and dissolved substances by animals. In organisms like Amoeba it can be done by a contractile vacuole but higher animals including man need urinary system. 4. Urinary system of humans is formed of a pair of Kidneys, a pair of ducts called Ureters, a Urinary Bladder to store urine and Urethra the duct that carries urine outside the body. Filtration: Kidneys filter the blood and small molecules enter the renal tubules. Reabsorption: Useful substances are reabsorbed from the filtrate. Secretion: Some substances not filtered from blood are actively secreted into filtrate. Excretion: The urine with wastes like urea and excessive salts or amino acids, leaves body with variable amount of water. Chapter 28 - How animal Body defends itself 1. Lymphatic System plays major role in body defense system. It consists of organs Spleen, thymus, lymph nodes, and lymph capillaries, lymphatic vessels, and lymphatic ducts. Tonsils and appendix are lymphatic tissues. 2. Immunity means resistance to a particular disease. Body achieves immunity by non-specific and specific responses against invaders. Non-specific action is against all invaders and consists of 2 defense lines 1st and 2nd. Non-specific Immunity: An intact skin and mucus membranes form 1st line of defense against all invaders. It includes tears in eyes, sweat on skin, saliva in mouth, and acid in stomach. • 2nd defense line is formed by Phagocytes, Natural Killer cells and proteins like Interferon. • Phagocytes eat bacteria and viruses by phagocytosis. • Interferon interferes in multiplication of viruses. • Inflammatory response draws phagocytes to the site of injury, causes swelling and redness. • Lymph nodes filter interstitial fluid and kill cancer cells. Specific Immunity serves the 3rd line of defense. It produces special proteins effective against a specific invader. Humoral Immunity: It involves making Y-shaped proteins called Antibodies which roam in body fluids like blood to inactivate the invaders. B-cells are responsible for this immunity. Cellular Immunity: T-cells are responsible to defend against invaders inside cells. Active Immunity is achieved by making Antibodies inside the body due to infection or vaccination. Passive Immunity is achieved by giving antibodies made in another organism of same or different species. This is done if the patient’s immune system is weak or cannot make antibodies fast enough to defend against the attack. For example a newly born baby has a weak immune system and mother’s milk passes its antibodies to the baby to defend against certain diseases. • 3. 4. 5. 6. 7. 8. Comparison of B-Cells and T-Cells Cell Type B-Cells T-Cells Mature inside Bone marrow Thymus gland Responsible for Humoral (body fluid) immunity Cellular immunity Act by making Antibodies Cytotoxic cells and enzymes Other types Change to Plasma cells to form antibodies Helper T-cells and Memory cells 9. HIV attacks Helper T-cells and compromises the immune system and causes AIDS. Then many opportunistic diseases like Pneumonia attack and kill the person. 10. Memory T-cells live for long periods and alert the immune system when an invader enters the body after 1st infection or vaccination.