Homeostasis

• The environment of living organisms is always changing.
• The cells inside your body, do not have a changing environment.
• Your body keeps the environment inside of you almost the same, all the time.
• The temp, amount of water, and concentration of glucose are almost always constant. Keeping this internal environment constant is called homeostasis.
• Homeostasis helps your cells to work as efficiently as possible.
• Keeping a constant internal temperature of 37 c helps enzymes to work at the optimum rate.
• Keeping a constant amount of water means that your cells are not damaged by absorbing or losing too much water by osmosis.
• Keeping a constant concentration of glucose means that there is always enough fuel for respiration.
• Sweat glands secrete a liquid called sweat. Sweat is mostly water mixed with a small amount of salt and urea dissolved in it.
• Sweat travels up the sweat ducts and out onto the surface of the skin through sweat pores.
• Blood vessels and nerve endings are sensitive to touch, pain, pressure, and temperature, so they help to keep you aware of changes in the environment.
• Beneath the skin is a layer of fat. This fatty tissue is made up of cells which contain large drops of oil. This helps to insulate your body against heat loss and also acts as an energy reserve.
• Sweat lies on the surface of hot skin. The water in it then evaporates, taking in heat from the skin with it and cooling down the body.
• Negative feedback: Feedback that tends to stabilize a process by reducing its rate or output when its effects are too great.
• Cells need a steady supply of glucose to allow them to respire, without this they cannot release the energy they need. Brain cells are especially dependent on glucose for respiration (They die quickly if they are deprived of it)
• Too much glucose in the blood is not good either, as it can cause water to move out of the cells and into the blood by osmosis. This leaves the cells with too little water for them to carry out their normal metabolic processes.
• The control of blood glucose concentration is carried out by the pancreas and the liver.
• The pancreas makes pancreatic juice. It also contains little groups of cells that make two hormones called insulin and glucagon.
• Insulin and glucagon help to control the amount of glucose in the blood. Insulin has the effect of lowering blood glucose concentration, and glucagon does the opposite.
• Glucose is absorbed through the walls of the small intestine and the concentration of glucose in the blood goes up.
• The cells in the pancreas detect the rise in blood glucose concentration and secrete insulin into the blood. When the insulin reaches the liver, it causes the lier to absorb glucose from the blood.
• Glucose is used for respiration and glycogen, which is stored in the liver.
• If the blood glucose concentration falls too low, the pancreas secretes glucagon. This causes liver cells to break down glycogen into glucose and release it into the blood.