Homeostasis We Are Learning Today: The mechanisms by which the body maintains a constant internal environment Starter: Sports drinks Why do runners drink these rather than just water? What do the labels claim they can do? Do you think these claims are true or are they just a good way for drinks manufacturers to make quick money?

Homeostasis Humans need to maintain a constant internal environment, controlling levels of water, blood sugar and temperature. Homeostasis is the result of the coordination of your nervous system, your hormones and your body organs.

Thermoregulation: What organs are involved? Hypothalamus Muscle

Thermoregulation: Controlling temperature This is controlled to maintain the temperature at which enzymes work best. If you get too hot: Hair muscles relax; hairs lie flat so letting more heat out. Evaporation of sweat secreted by sweat glands cools skin. Capillaries dilate, blood flow increases at the surface of the skin causing heat to be lost by radiation.

Thermoregulation: Controlling temperature If you get too cold: Hairs muscles pull hairs on end, trapping a layer of air which acts as an insulator. Sweat glands stop secreting sweat. Capillaries close to surface constrict, to allow less blood to flow. Muscles shiver, generating heat.

Osmoregulation What organs are involved? Pituitary gland Hypothalamus Kidney

Osmoregulation: Controlling water Inputs Water content in: Drinking Digestion Water made in: Cellular respiration Outputs Water content in: Urine Breathing Sweating Bowel movement

Check your learning How might you expect the volumes in the above table to change on: A very hot day A very cold day

Osmoregulation: Controlling water Place the sequence of events in order: Detected by the hypothalamus Kidneys absorb less water from the blood So less water is lost in urine (urine is more concentrated) Blood water level returns to normal Too little water in the blood More ADH released into the blood by the pituitary gland

Too little water in the blood Detected by the hypothalamus More ADH released into the blood by the pituitary gland Kidneys absorb less water from the blood So less water is lost in urine (urine is more concentrated) Blood water level returns to normal

Glucoregulation – Controlling blood sugar levels Liver Pancreas

Glucoregulation It is important that the concentration of glucose in the blood is kept at a constant level. Glucose is a sugar needed by cells for respiration. Insulin is secreted by the pancreas to control sugar level.

What is insulin? Insulin is a hormone which affects your metabolism and other body functions. Insulin causes cells in the liver, muscle, and fat tissue cells to take up glucose from the blood, storing it as glycogen in the liver and muscle, and stopping use of fat as an energy source. When insulin is absent (or low), glucose is not taken up by body cells, and the body begins to use fat as an energy source.

Glucoregulation – Controlling blood sugar levels Place the sequence of events below in order: More glucose absorbed by tissues and the liver Blood glucose reduced Insulin injected by the pancreas Blood with too much glucose in it

Blood with too much glucose in it Insulin injected by the pancreas More glucose absorbed by tissues and the liver Blood glucose reduced

Complete the word loop first to win the prize! Team Challenge Complete the word loop first to win the prize!