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PHGY 214 - Homeostasis + Nervous System (CH 1, CH 3) .pdf

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Queen's University
PHGY 214
Dean Vaughan

PHGY 214NERVOUS 1 CH 1 CH 3 Chapter 1 pg 818Homeostasis and HomeokinesisHomeostasis ability of a cellorganism to regulate internal conditions ex pH using feedback systems to minimize variation and maintain health ONLY in response to the INTERNAL ENVIRONMENTThere is no set point in homeostasis more of a set range eg body temp btwn 3637Homeokinesis suggests the organism will achieve equilibrium in body functions by continuous change conditions are continuously changing ex breathing heart rate blood pressure In healthy lungs control of airway calibre is homeokineticThe difference homeostasis responds to change in internal environment while homeokinesis initiates itConcept of Homeostasis Since most cells do not have access to the external environment like say a single celled amoeba would have they rely on the watery internal environment to make exchangesBODY CELLSFluid contained in body cells is intracellular uid ICF Fluid outside the body is extracellular uid ECF The ECF is the internal environment of the body inside the body but outside of each cellThe ICF is inside each cell and the external environment is OUTSIDE the bodyThe ECF internal environment is made of two components 1Plasma uid portion of the blood2Interstitial uid surrounds and bathes the cellCells use the plasmainterstitial uid to transportreceive various materials from other cells and the external environment BODY SYSTEMSThe internal environment ECF must be compatible with the body cells in order for them to survive ex pH must be maintained in physiological range wastes must be removed and temperature must be maintainedHomeostasis is essential for survival of cells which make up body systems which maintain homeostasis loopHomeostasis is a dynamic steady state meaning always responding to changes in the internal environment wo deviating from the physiological range Long term chronic adaptations make the body more effective in responding to an ongoing repetitive challenge Ex response to exercise is acute and chronic regulation of heat for next time
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