1. What is meant by tolerable limits Mechanisms never allow it to go too high or too low What two ways does an animal have of communicating a response? Hormones or by nerves Explain why the above is called a negative feedback system. If it goes too high mechanisms bring it down/ if it goes too low other mechanisms bring it back up Control of water content of the blood Which part of the body monitors the water concentration? Pituitary gland in the brain Explain what would happen if it detected a decrease in the water concentration of the blood Increases the production of ADH by the pituitary gland Increases the permeability of tubules to water More water reabsorbed back into the blood Water concentration of the blood increases Urine less volume but concentrated

2. Explain what would happen if the pituitary detected an increase in the water concentration of the blood. A decrease the production of ADH by the pituitary gland A decrease in the permeability of tubules to water Less water reabsorbed back into the blood Water concentration of the blood now decreases Urine large volume but dilute What type of messages are used to maintain water levels in the blood? Hormone ADH

3. Which part of the body is used as a resevoir of stored carbohydrates? Liver Which part of the body monitors the blood sugar levels? Pancreas Explain what would happen if the body detected an increase in the blood sugar (glucose) levels. Pancreas increase the insulin production and decrease glucagon Insulin acts on the liver cells by making them more permeable to glucose and stimulating enzymes in the cell to change glucose into glycogen store. Glucose concentration in the blood decreases.

4. Explain what would happen if the body detected a decrease in the blood sugar (glucose) levels. The pancreas increase the production of glucagon and decrease production of insulin Glucagon will stimulate the production of specific enzymes in the liver cells Glycogen changes into glucose in the liver cells Glucose concentration in the blood increases What type of messages are used in maintaining blood sugar levels? Hormones

5. Maintaining the body temperature in mammals Why is it important to keep the body temperature within tolerable limits? To provide optimum temperature for enzyme activity. Which part of the body monitors the body temperature? The hypothalamus in the brain Explain what corrective mechanisms would occur if your body temperature should increase. Hypothalamus send nerve impulse to the skin This stimulates sweating which will cool the body down as water evaporates from the surface of the skin Vasodilation occurs which makes arterioles dilate bringing more blood to the skin surface and more heat radiates from the skin Hair erector muscles relax and the hair lies flat Now body temperature lowers

6. Explain what corrective mechanisms would occur if your body temperature should decrease A decrease in body temperature is detected by the hypothalamus in the brain The hypothalamus sends nerve impulses to the skin Hair erector muscles contract and make the hair stand up, this traps air and insulates the skin Vasoconstriction occurs – this is when the arterioles constrict and a smaller volume of blood flows to the skin surface so less heat is radiated from the skin. Muscles make you shiver increasing metabolism and creating heat. The body temperature is now raised What form of communication takes place between the receptor centre and the effector eg skin Nervous impulses

7. Explain the following terms Endotherm – An organism that gets most of its heat from its own metabolism ( ie heat is produced within the body) eg mammals and birds These organisms use negative feed back and will therefore have a fairly constant body temperature. Ectotherm – An organism that gets most of its heat from the surrounding environment which means the body temperature changes. Eg fish These ectotherms do not use negative feedback