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Homeostasis • Controlling your internal conditions Carbon Dioxide • Produced by respiration • Removed from the lungs when we breathe out • High concentration of CO2 in blood. • Low concentration of CO2 in lungs. • Blood moves from high concentration to low concentration down concentration gradient. • CO2 in lungs breathed out during exhalation. Temperature • Regulated in the thermoregulatory centre in the brain • It has receptors that detect the temperature of the blood in the brain • Temperature receptors in skin • Done to maintain core body temperature needed for chemical processes/enzymes to work effectively When We’re Too Hot Heat energy Dilated capillaries • Sweating • Heat loss by evaporation Skin • Vasodilation • Capillaries near skin surface get bigger • Heat lost by radiation • When core body temperature is above 37°C • Detected by skin and thermoregulatory centre • Hairs lay down • Stops air being trapped – no insulation When We’re Too Hot • Shivering • Generate heat by muscles rapidly contracting and relaxing • Heat from respiration and friction • Vasoconstrictions • Capillaries near skin surface get smaller • Reduces heat lost by radiation • When core body temperature is below 37°C • Detected by skin and thermoregulatory centre • Hairs stand up • Traps air – good insulator Temperature Too hot (temperature above 37°C) Too cold (temperature below 37°C) Sweating – increase heat Shivering – generate heat loss by evaporation by respiration in muscles Hairs lay down – reduce insulation Hairs stand up – trap an insulating layer of air Vasodilation – increase heat loss by radiation Vasoconstriction – reduce heat loss by radiation Water • Water is lost by: • Sweating • Breathing out • Excretion Water Filtration in the Nephron Water, glucose, amino acids, protein, mineral salts and urea filtered out of the blood. Water is mixed with the urea here depending on hydration levels. Glucose, proteins, mineral salts and amino acids are reabsorbed into the blood. Water is collected here depending on the hydration level. Urine is taken to the bladder to be stored. What happens when the kidneys go wrong? Kidney Dialysis Kidney Transplant Kidney Dialysis • • • • • • • Blood is removed from arm and thinned to prevent clotting. Goes through dialyser which contains membranes and dialysis fluid. Large proteins and blood cells can’t fit through membrane. Concentration of glucose, water and mineral ions same in dialysis fluid as in blood. Urea moves from blood to dialysis fluid down concentration gradient. Excess salt moves from blood to dialysis fluid down concentration gradient. Air bubbles removed from clean blood and returned to body. Kidney Transplant • Need to find a donor that is a good tissue match for the recipient. • This means they need to find someone with similar antigens on the cell surface. • After the operation, immunosuppressant drugs need to be taken to help prevent organ rejection. • This can lead to lots of side-effects such as reduced immune response to communicable diseases. • Transplanted kidneys last on average 9 years – then it’s back onto dialysis until a new donor is found. What happens when the kidneys go wrong? Kidney Dialysis Machine removes toxins from blood Not very portable Hooked up to the machine for up to eight hours three times a week Kidney Transplant No need for machine to help clean blood Can take a long time to find a donor Body can reject donor organ Glucose or Sugar • Controlled by the pancreas • It has receptors that detects the glucose levels in the blood • Releases hormones (chemical messengers that travel through the bloodstream) to the liver Insulin Glucagon HT Only: Glucose Regulation Glucose receptors in pancreas Glucose too high. Pancreas releases insulin Glucose too low. Pancreas releases glucagon. Insulin tells liver to convert glucose into GLYCOGEN Glucagon tells liver and muscles to convert GLYCOGEN into glucose GLYCOGEN stored in liver and muscles Glucose levels drop Glucose levels rise Diabetes • Caused when pancreas doesn’t produce enough or any insulin • Two types: • Type 2 – controlled by diet and tablets • Type 1 – controlled by insulin injections • Symptoms of diabetes – • Unbearable thirst • Sweet smelling urine • Weight loss due to protein digestion • Extreme tiredness
