Homeostasis is the maintenance of a constant internal environment Keeping warm 1.Vasoconstriction- blood vessels _______ and move away from ______ of skin 2.Hairs on skin become erect which trap ______ which is an ________ 3.Shivering- muscles moving rapidly which generates heat by ________. 4.Thermoregulatory centre in brain sends messages e.g. to put a jumper on. Cooling down 1.Vasodilation- blood vessels _______ and move towards ______ of skin 2.Hairs on skin lay flat. 3.Sweating- water _______ from the surface of the skin using heat energy from the surface of the skin therefore cooling us down. 4.Thermoregulatory centre in brain sends messages e.g. have a cold drink Can you explain why? 1.Imagine you have just walked out of the shower. Why do you feel chilly when you walk from the bathroom to your bedroom? 2.What 3 ways can we get water into the body? 1.__________ 2.__________ 3._______ 3. Why does a person who is dehydrated sweat less? Explain these pictures:

Using the picture above explain: 1.What is filtered out of the blood and how?__________________________ _______________________________ ______________________________ 2. What stays in the blood and why?______________________________ __________________________________ 3. What is completely reabsorbed into the blood in healthy kidneys and how?_____________________________ __________________________________ __________________________________ 4. What else is reabsorbed and in what amounts?__________________________ __________________________________ __________________________________ Active transport of glucose Glucose is reabsorbed back into the blood by active transport. Active transport is special type of diffusion where substances move from a lower concentration to a higher concentration (__________ concentration gradient). This process uses ________ from respiration. Compare osmosis, diffusion and active transport:

Summary of kidney function: A healthy kidney produces urine by: ■ first filtering the blood ■ reabsorbing all the sugar ■ reabsorbing the dissolved ions needed by the body ■ reabsorbing as much water as the body needs ■ releasing urea, excess ions and water as urine. Kidney failure can be treated by either having dialysis of a kidney transplant In dialysis the persons blood flows between partially permeable membranes. The dialysis fluid contains same concentration of useful substances as the blood- so glucose and mineral ions are not lost. Urea diffuses out of blood. Carried out at regular intervals Kidney transplants replace a diseased kidney with a normal one. The donor kidney may be rejected by immune system because the antigens on the cells of the donor (proteins on surface of cells) are different to the recipients therefore the recipients antibodies may attack them as they appear foreign Disadvantages of transplants: any major surgery carries some risk the kidney may be rejected by the body of the patient a precise match of tissue type is needed there is a severe shortage of donors Advantage- can live a normal life if all goes well Disadvantages of dialysis: they are expensive the patient must have his or her blood connected to the machine for several hours every week patients must follow a very rigid diet to avoid complications they only work for a limited time for a patient

Blood glucose is controlled by the pancreas When blood glucose is high (after eating a meal) Insulin also stimulates the production of glycogen- a store of glucose in the liver When blood glucose is low (missed lunch) Pancreas makes another hormone, Glucagon- causing glycogen to be converted back into glucose to raise blood glucose levels Glycogen is a long chain of glucose molecules