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6.5 (Part 2) Hormones and homeostasis

6.5 (Part 2) Hormones and homeostasis. 6.5.7 State that the endocrine system consists of glands that release hormones that are transported in the blood. Endocrine glands Release hormones into the bloodstream.

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6.5 (Part 2) Hormones and homeostasis

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  1. 6.5 (Part 2) Hormones and homeostasis

  2. 6.5.7 State that the endocrine system consists of glands that release hormones that are transported in the blood. • Endocrine glands Release hormones into the bloodstream. • Hormones are chemicals released in one part of the body that travel through the bloodstream and affect the activities of cells in other.

  3. 6.5.8 State that homeostasis involves maintaining the internal environment between limits, including blood pH, carbon dioxide concentration, blood glucose concentration, body temperature and water balance. Body cells work best if they have the correct • Temperature. What will happen if temperature levels get too high? – Think enzymes… • Water levels. What will happen if the blood becomes to diluted? – Think osmosis… • Glucose concentration. What will happen if there is too much sugar in the blood? - Think osmosis again… • pH. What happens if the tissue fluid is too acid? - Think enzymes again….. • Carbon Dioxide. Your body has mechanisms to keep the cells in a constant environment. These mechanisms are called Homeostasis.

  4. 6.5.9 Explain that homeostasis involves monitoring levels of variables and correcting changes in levels by negative feedback mechanisms. Homeostasis works using negative feedback systems. A Feedback system is a cycle of events in which the status of a body condition is continually monitored, evaluated, changed, re-monitored, re-evaluated, etc. http://www.freethought-forum.com/images/anatomy/nfeedback.gif

  5. There are 3 basic components of a feedback system 1) Receptor – this is a sensor that responds to changes (stimuli) e.g. thermo-receptors in the skin. 2) Control center – this sets the range of values or conditions; it evaluates the input and sends an output e.g. the hypothalamus. 3) Effector- this receives the output from the control center and produces a response. e.g. pilo-erector muscles in the skin

  6. The hypothalamus acts as a thermostat and receives nerve impulses from heat and cold thermo-receptors in the skin. There are also receptors in the hypothalamus- called central thermoreceptors. It releases hormones into the blood that effect many different parts of the body.

  7. 6.5.10 Explain the control of body temperature, including the transfer of heat in blood, and the roles of the hypothalamus, sweat glands, skin arterioles and shivering. All mammals maintain a constant body temperature. For humans it is 37ºC. If your body is in a hot environment or is exercising lots your body temperature is 37ºC. If your body is in a cold environment or not exercising your body temperature is still 37ºC In order to maintain this 37ºC the amount of heat coming in to the body and produced by the body must equal the amount of heat being lost by the body.

  8. What mechanisms are there to cool the body down? • Sweating When your body is hot, sweat glands are stimulated to release sweat. The liquid sweat turns into a gas (it evaporates) To do this, it needs heat. It gets that heat from your skin. As your skin loses heat, it cools down.

  9. Sweating The skin

  10. What mechanisms are there to cool the body down? 2. Vasodilation Your blood carries most of the heat energy around your body e.g. from organs like the liver to the skin. There are capillaries underneath your skin that can be filled with blood if you get too hot. This brings the blood closer to the surface of the skin so more heat can be lost. This is why you look red when you are hot!

  11. This means more heat is lost from the surface of the skin If the temperature rises, the blood vessel dilates (gets bigger).

  12. What mechanisms are there to warm the body up? 1. Vasoconstriction This is the opposite of vasodilation. The capillaries underneath your skin get constricted (shut off). This takes the blood away from the surface of the skin so less heat can be lost.

  13. This means less heat is lost from the surface of the skin If the temperature falls, the blood vessel constricts (gets shut off).

  14. What mechanisms are there to warm the body up? 2. Pilo-erection This is when the hairs on your skin “stand up” . It is sometimes called “goose bumps” or “chicken skin”! The hairs trap a layer of air next to the skin which is then warmed by the body heat The air becomes an insulating layer.

  15. Behavioral changes in response to temperature changes Cold Drink hot drinks; eat hot food Put on more clothes Get out of the wind Stand by a fire or ‘radiator’ Huddle up Shiver Do exercise Hot Drink icy drinks; eat ice cream Reduce clothing Stand in a breeze Stand in the shade or get a/c Space out Chill! Lay in a hammock

  16. Controlling Glucose levels Too much Glucose in the blood will affect the cells of the body (and the blood) by osmosis. Water

  17. Controlling Glucose levels Too little Glucose in the blood will affect the cells of the body (and the blood) by osmosis. Water

  18. Levels of glucose are monitored in the pancreas There are 2 types of special cells called Islets of Langerhans. 1.α cells – if the glucose levels are too low these cells release glucagon into the blood. 2. β cells - if the glucose levels are too high these cells release insulin into the blood.

  19. If there is not enough glucose in the blood, Glucagon is transported in the blood from the pancreas to the liver where it converts some glycogen into glucose. Glycogen Glucagon Glucose in the blood

  20. If there is too much glucose in the blood, Insulin produced in the pancreas is carried to the liver by the blood where it converts some of the glucose to glycogen Glycogen Insulin Glucose in the blood

  21. In summary… Insulin In the liver Glucose is changed to Glycogen β cells in the pancreas release insulin Glucose decrease Glucose increase No deviation Glucose Norm Glucose Norm Glucose decrease Glucose increase Glucagon In the liver Glycogen is changed to Glucose α cells in the pancreas release Glucagon

  22. Diabetes • Some people do not produce enough insulin. • When they eat food, the glucose levels in their blood cannot be reduced. • This condition is known as DIABETES. • Diabetics sometimes have to inject insulin into their blood. They have to be careful of their diet.

  23. Glucose levels rise after a meal. Insulin is produced and glucose levels fall to normal again. Glucose Concentration Normal Time Meal eaten

  24. Glucose levels rise after a meal. Glucose Concentration Diabetic Insulin is not produced so glucose levels stay high Time Meal eaten

  25. Glycogen The glucose in the blood increases. But there is no insulin to convert it into glycogen. Glucose concentration rises to dangerous levels. Insulin Glucose in the blood

  26. 6.5.12 Distinguish between type I and type II diabetes. Type I Diabetes • The Pancreas stops producing Insulin. • This is often due to an auto-immune disease killing the β cells. Type II Diabetes • The Liver stops responding to Insulin. • This is often due to eating too much sugar reducing the sensitivity of the liver to Insulin.

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