2. Topics to be discussed
Definition
Internal environment
Systems involved in maintaining homeostatis
Feedback mechanisms
Components of feedback loop
Negative feedback
Positive feedback
Gain of feedback
3. Homeostatis
• The term used by physiologist to mean maintainence of
nearly constant conditions in internal environment
irrespective to the change in external environment.
• Term was coined by a American physiologist W.B.
Cannon In 20th century.
4. What is Internal environment?
• The extracellular fluid forms the internal environment.
5. Parameters of homeostatic mechanisms
• Temperature
• PH
• Osmolality
• Conc of K+ Na+
• glucose
• CO2,O2,etc.
6. Systems involved in maintaining
Homeostatis
• Respiratory System : supply of O2 and removal of
CO2
• Gastrointestinal Tract: supply nutrients including
carbohydrates,Fatty acids,Amino acids.
• Excretory system: removal of unwanted substance
like urea,uric acid, Excessive ions and water.
• Nervous system: composed of sensory input
portion ,the central nervous system and the motor
unit.
• Endocrine system: 8 major endocrine gland
secretes hormones eg. thyroid
hormone,insulin,adenocortical hormones so
mostly they regulates metabolic functions.
12. POSITIVE FEEDBACK
• In positive feedback mechanism , an increase in the
variable triggers further increase the quantity of variables.
• This cycle terminates only when the stimulus applied to
trigger the system is removed or the process itself
terminates.
• The positive feedback mechanism is always a part of
negative feedback mechanism.
16. Gain of control system
• the degree of effectiveness with which a control
system is determined by the gain of the negative
feedback.
• for eg. large amount of blood is transfused in a
person whose baroreceptors are not working .
• so the blood pressure rises from 100- 175mmhg
• Healthy person: 100- 125
So, the gain is correction/error
-50/25
Gain = -2
