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Homeostasis

Homeostasis. Homeostasis. Process that maintains a constant internal environment despite changes in the external environment. Blood sugar range 80-110 mg/100 mL. temp range 36.8 o C +/- 7 o C. Blood pH range 7.35-7.44. Average Blood Volume 4.7 L **. Pg 345. Feedback Systems.

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Homeostasis

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  1. Homeostasis

  2. Homeostasis • Process that maintains a constant internal environment despite changes in the external environment

  3. Blood sugar range 80-110 mg/100 mL temp range 36.8oC +/- 7oC Blood pH range 7.35-7.44 Average Blood Volume 4.7 L **

  4. Pg 345

  5. Feedback Systems 3 Functional Parts 1. Sensor - detect changes in their environment, send signal to control centre

  6. Feedback Systems 3 Functional Parts 2. Control Centre – sets the range of values within which a variable should be maintained • Receives info from sensors, send signals to effectors when needed 3. Effector – receives signal from control centre and responds

  7. Negative Feedback Systems • Designed to resist change • Trigger a response that reverses the changed condition back to within a normal range • Most common in the body

  8. Pg 346

  9. Stimulus: ↑Core Temperature Results from... • exercise • environmental temperature

  10. Stimulus: ↑Core Temperature • Sensors in the brain send a msg to the hypothalamus

  11. Response to Heat Stress Hypothalamus Sweat Glands Skin blood vessels

  12. Hypothalamus Sweat Glands Initiate sweating Evaporation of sweat causes cooling

  13. Hypothalamus Skin blood vessels Dilate to allow more blood flow to skin Blood loses heat through skin

  14. Result? • Body temperature ↓

  15. Stimulus: Extreme Cold • Thermoreceptors in skin send a msg to the hypothalamus

  16. Response to Cold Stress Hypothalamus Skeletal Muscles Skin blood vessels

  17. Hypothalamus Skeletal Muscles Contract (goose bumps) Causes hair to stand up – traps warm air next to skin

  18. Hypothalamus Skin blood vessels constrict Limit blood flow to reduce heat lost through skin

  19. Response to Cold Stress • Shivering • Cycles of rapid muscle contraction (10 – 20 X per min) • Generate heat by increasing metabolism

  20. Result? • Body temperature ↑

  21. Positive Feedback Systems • Strengthen or increase a change in a variable • Less common in the body Example: • Birthing process • Blood clotting

  22. Pg 347

  23. What kind of feedback system is this?? During lactation (milk production), the suckling by the baby stimulates the production of oxytocin, which in turn causes contraction of smooth muscle surrounding the milk duct, causing milk to flow. The flow of milk increases the suckling by the baby and more oxytocin is produced. Positive feedback

  24. Now it’s your turn... • Draw a feedback loop to show how your body reacts to a stimulus of an increase in body temperature AND the feedback loop for a stimulus of a decrease in body temperature (pg 346 & 347) • Label the 3 parts for each feedback system • Answer pg 348 # 1-3, 6-10

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