Physiology 2130 Lecture Notes - Extracellular Fluid, Negative Feedback, Blood Plasma
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Introduction to Physiology
What is Physiology?
Physiology is the study of functions in living organisms
Explores the mechanisms by which the organisms control their INTERNAL environments
regardless of what happens outside in the EXTERNAL environment
Explains physical and chemical factors responsible for both normal function and disease
Maintenance of relatively stable conditions within the internal environment regardless of what
is happening in the external environment.
o Our body is capable of maintaining internal environment so that our cells can function
regardless of external conditions
o Body maintains homeostasis using negative and positive feedback mechanisms
INTERNAL environment: is the fluid in which the cells of the both are bathed. Ex: interstitial
fluid and blood plasma
EXTERNAL environment: region outside the body. Ex: space and contents of the digestive,
respiratory, urogenital tracts, lungs.
Negative feedback control systems
o Set point
o Control centre (integrator)
o Controlled variable
o Sensor (receptor)
Found throughout the body and
perform different functions such as maintaining body temperature and maintain body fluids
The CONTROLLED VARIABLE eventually shuts off its own production
Example: Body temperature dropping from set point (cold)
o Set point for body temperature is 37 degree Celsius (body wants to maintain)
o If body temperature drops to 35 degrees it is detected by the sensors in the nervous
o The sensors signal the control centre which is in a specific region of the brain called the
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