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Biology 3.4

Biology 3.4. Demonstrate understanding of how an animal maintains a stable internal environment. Homeostasis.

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Biology 3.4

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  1. Biology 3.4 Demonstrate understanding of how an animal maintains a stable internal environment

  2. Homeostasis “The tendency of an organism or a cell to regulate its internal conditions, usually by a system of feedback controls, so as to stabilize health and functioning, regardless of the outside changing conditions” ?

  3. Why? • Cells only function within a narrow range of conditions such as: • pH • Osmotic pressure • Temperature • These conditions must be kept relatively the same, despite internal activity and changes in the external environment • The body must be constantly working using various organs / systems / physiological processes to achieve a stable equilibrium

  4. How? • Feedback control systems control the internal environment and involve: • Input: a stimulus (internal or external, eg temp change) • Receptors / sensors: detect stimulus (nerves, organs) • Controllers: signal a response, (brain, esp hypothalamus) • Effectors: action the response, (glands / muscles / organs) • Output: the response / action of effector • Feedback means that the level of output will affect input and thus the system is cyclical.

  5. Where’s the hypothalamus?

  6. Negative Feedback • High output inhibits further output (system receives high input which halts output) • For example: • Its cold in the room • Thermostat detects cold temperature, turns on heater (output) • The room gets hot • Thermostat detects hot temperature, turns off heater (output): this is negative feedback • Room gets cold…

  7. Biology 3.4 Requirements… • Comprehensive understanding of a control system that regulates ONE of these: • Body temperature • Blood pressure • Osmotic balance • Blood glucose levels • Levels & balance of respiratory gases in tissues

  8. When good control systems go bad… • Efficiency of control systems decreases with aging…results in: • Unstable internal environment • Disorders • Hypothermia, hyperthermia…. • Death

  9. Oxygen Saturation • http://en.wikipedia.org/wiki/Pulse_oximetry#Indication • http://www.howequipmentworks.com/physics/respi_measurements/oxygen/oximeter/pulse_oximeter.html • http://en.wikipedia.org/wiki/Oxygen_saturation

  10. http://www.gizmag.com/wello-iphone-case-health-tracker-heart-rate-blood-pressure/31043/pictures#5http://www.gizmag.com/wello-iphone-case-health-tracker-heart-rate-blood-pressure/31043/pictures#5

  11. Purchasing • Oximeter • http://www.fishpond.co.nz/c/Health/q/Blood+Oxygen+Monitor • http://www.emech.co.nz/Medical+Supplies/ENT++Diagnostic/Pulse+Oximeters.html?gclid=CLPd6Oa-4b4CFZYGvAodsFMAEg • http://www.emech.co.nz/Medical+Supplies/Weekly+Specials.html • http://www.aliexpress.com/wholesale?SearchText=oximeter&catId=0&initiative_id=SB_20140604195300

  12. Urine Strips • http://www.fishpond.co.nz/c/Health/q/Urine+Glucose+Test+Strips

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