Homeostasis

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Define Homeostasis
conditions of the internal environment are maintained within a narrowly defined limit in the body regardless of what enters or how the external environment may change
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Whats in the Internal Environment?
Fluid surrounding cells- extracellular fluid that involves 2 main elements
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Name and describe the 2 main elements of extracellular fluid
Interstitial Fluid (tissue fluid)- fluid that leaves the body capillaries to 'bathe' cells bringing O2& nutrients, Fluid returns to the blood with wastes e.g. CO2 from cellular metabolism. 2.) Blood Plasma- fluid surrounding blood cells
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Factors in the Internal Environment
Core Body Temp, pH, Gases (O2, CO2), BP, Glucose, Blood Volume, Ca ions, Na ions
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Describe Internal Environment
Cells take in O2, Glucose, AA, vitamins& minerals from internal env so amount of these substances in internal environment decreases. cells increase level of cellular waste products e.g. CO2& ammonia. Heat Gained from outside& in changes IE temp
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Describe Internal Environment
infection with microorganisms- increase harmful toxins, cells survive as health composition of IE is stabilised by homeostatic regulation. Keep cell surroundings narrow limits as chem in cells may be subjected to altered activity.
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Monitoring Levels of Potassium is important because...
Levels of K in narrow limits or lead to membrane potentials in nerve and cardiac muscles affected leading to heart failure/ death
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What are homeostatic mechanisms?
Based around feedback loop where the variable e.g. BGL or BP are constantly monitored
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Important homeostatic principle is
self-adjusting mechanisms in operation e.g. control process built into the system, which normally form a system (loop or cycle) which automatically responds to change
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Describe the Homeostatic Process
Within loop of info in form of stimulus is received by RECEPTOR& converted into a signal. The signal travels to area where it's evaluated& interpenetrated by the CONTROLLER. Set of signals sent to EFFECTOR to produce a response to regain normal value
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What is Negative Feedback
Corrective Mechanism. Automatic Response which reverses the original change& brings variable/ factor within internal environment back to normal.
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First 2 stages of Negative feedback?
Exposed to stressor-disturbance= series of reactions decrease any changes produced& returns inner stability. Level of substances& parameters kept within 'normal' range by action of 2 opposing mechanisms- 1 elevation, 1 reduction
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Last Stages of Negative Feedback?
Homoeostasis results in oscillations of any given parameter, about set level because feedback results in constant adjustment up& down. Effective homeostatic mechanisms decrease fluctuations- if all BGL monitored or temps taken= narrow range values
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Explain Positive Feedback
opposite to negative feedback encouraging physiological process/ amplifies action of the system
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Glucose is....
Most abundant& important simple sugar, all body cells are able to metabolise glucose to produce energy. Brain& nerve cells use it preferentially& RBC use it exclusively. Maintain stable BGL any glucose not required immediately stored.
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Where is Glucose Stored?
1. Glycogen- Liver, 2. Glycogen- muscle cells, 3. Triglyceride- adipose tissue
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Whats the importance of relatively stable BGL in Internal Environment?
1. Essential energy source enabling mitochondria to produce ATP for cell activities, 2. Liver and skeletal muscle cells glucose is converted into carbohydrate storage molecule- glycogen- readily broken down by releasing glucose into blood
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Whats the importance of relatively stable BGL in Internal Environment?
3. Switch between storage& breakdown of glycogen helps maintain relatively stable BGL between meals, 4. Fat cells- excess glucose synthesises fat& increases long term energy stores
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High Glucose- Glucose Homeostasis
1. Stimulus: increased BGL, 2. B cells of pancreas stimulated= release insulin -> blood. 3. Insulin-> body cells takes up more glucose& liver takes up glucose to store as glycogen. 4. BGL decrease to set point, stimulus for insulin release decrease
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Low Glucose- Glucose Homeostasis
1. removal of excess glucose from blood, low BGL, 2. A cells of pancreas stimulated= release glucagon-> blood. 3. glucagon- liver breaks down glycogen& release glucose-> blood. 4. BGL increase set point, stimulus for glucagon release dimishes
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Effects of Hormone on Metabolism: Insulin
* uptake of glucose from blood-> cells. * glucose conversion-> glycogen for liver& muscle storage (Glycogen synthesis), use of glucose in cells to form ATP (glycolysis), increased fat& protein synthesis
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Effects of Hormone on Metabolism: Glucagon
*increased breakdown glycogen stores from glucose (glycogenolysis), * increased breakdown fats= increase circulating fatty acid, *increase glucose synthesis in liver& kidneyys from breakdown of fats or proteins (glucogenesis)
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Hormones on BGL
Insulin-> secretions lead to decreased BGL, Glucagon-> secretions lead to increased BGL
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Feedback Loop
Receptor-> surface of A&B cells, Controller-> Insulin& glucagon, Effectors-> liver cells, muscle cells, fat cells& other target cells
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Other cards in this set

Card 2

Front

Whats in the Internal Environment?

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Fluid surrounding cells- extracellular fluid that involves 2 main elements

Card 3

Front

Name and describe the 2 main elements of extracellular fluid

Back

Preview of the front of card 3

Card 4

Front

Factors in the Internal Environment

Back

Preview of the front of card 4

Card 5

Front

Describe Internal Environment

Back

Preview of the front of card 5
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