1. 1 Homeostasis

2. 2 Homeostasis Homeostasis is the maintenance of a dynamic consistency of the body’s internal environment. Normal functional activities of the cell depend on the internal environment being maintained within very limited normal range. The chemical content, volume, temperature, and pressure of the fluid must stay the same, regardless of external conditions, so that the cell can function properly.

3. 3 Homeostasis If the conditions in the fluid deviate from normal, mechanisms respond to restore conditions to normal. If the mechanisms are unsuccessful, the cell malfunctions and dies. This leads to illness or disease and if, homeostasis is not restored, eventually to death of the individual.

4. 4 Or when Mr. B asks his wife to buy a new big screen TV Or when Mr. B asks his wife to buy a new big screen TV

5. 5 Homeostasis Stable operating conditions in the internal environment Three components interact RECEPTOR (e.g., free nerve ending in the skin) Regulator (such as the brain) EFFECTOR (a muscle or a gland)

6. 6 Homeostasis Homeostasis is achieved by the regulatory mechanisms of the body, which operate mainly through “negative feedback” loops, counteracting the deviation from the ‘set-point’ value. Negative feedback mechanisms inhibit a change or deviation from normal

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8. 8 Homeostasis: Negative Feedback (continued)

9. 9 Homeostasis: Positive Feedback Positive feedback mechanisms stimulate or amplify changes. Positive feedback mechanisms stimulate or amplify changes. Why is positive feedback mechanism beneficial ? –Because it quickly terminates a process that, if allowed to continue for a prolonged period, might be detrimental. –The events in the birth of a baby and the formation of a blood clot are examples of positive feedback. –Production of oxytocin amplifies uterine contraction to help give birth to a baby –Fever... Infection signals onset of a fever that rises higher and higher to kill infection. At 45 degrees celsius, the fever kills

10. 10 Body Systems hard at work Kidneys – managing and filtering wastes Stomach / Intestines – obtaining nutrients Heart / Lungs – providing oxygen and removing carbon dioxide waste Testes / Ovaries – supplying sex hormones for reproduction Liver – filtering wastes Pancreas – secreting insulin for blood sugar And the list goes on and on and on…