1. Homeostasis
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2. PHYSIOLOGY Physis means nature Logos means study
Greek word
Physis means nature
Logos means study
“It is the study of biological functions of how the body works from cell to tissues, tissues to organs, organs to systems, from systems to organism and how the organism as a whole accomplishes particular tasks essential for life”.

3. Levels of organization in the body

4. Levels of organization in the body
The cell is the basic unit of both structure and function in a living being and is the smallest unit capable of carrying out the processes associated with life
The tissues are group of cells of similar specialization
An organ is unit made up of several tissue types
A body system is a collection of related organs
The body systems are packaged together into a functional whole body(Organism)
Organisms are independent living entities

5. Concept of Extracellular and Intracellular fluid
Intracellular fluid—fluid contained within all of the cells of the body
Extracellular fluid—fluid outside the cells of the body and is the internal environment in which the cells live . It is composed of plasma and interstitial fluid

6. Intracellular and extracellular fluid
Pp6 fig 1-4 silverthorn

7. Homeostasis Stasis means to “stand or stay”
Homeo means “same”
Stasis means to “stand or stay”
“Maintenance of a relatively stable internal environment or body’s coordinated response in order to maintain internal stability” OR
“Maintenance of internal environment against the harms of fluctuations in the external environment is called homeostasis”

8. Interdependent relationship of cells, systems and homeostasis
Pp12 fig 1-5 sherwood

9. Factors homeostatically regulated
Concentration of nutrient molecules
Concentration of CO2 andO2
Concentration of waste products pH
Concentration of water , salt and other electrolytes
Temperature
Volume and pressure

10. Contribution of body systems to Homeostasis
The Circulatory System
The Digestive System
The Respiratory System
The Urinary System
The Skeletal System
The Muscular System
The Integumentary System
The Immune System
The Nervous System
The Endocrine System
Reproductive system is not essential for homeostasis and therefore not essential for survival.

11. Homeostatic Control System
Is a functionally interconnected network of body components that operate to maintain a given physical or chemical factor in the internal environment relatively constant around an optimal level.
Can be classified as:
Intrinsic (local controls) are inherent compensatory responses of an organ to a change
Extrinsic controls are responses of an organ that are triggered by factors external to the organ , namely, by the nervous and endocrine systems

12. Continue…. Negative feedback mechanism In addition
Both intrinsic and extrinsic control systems generally operate on the principle of
Negative feedback mechanism
In addition
Positive feedback mechanism
Feedforward mechanism

13. Negative feedback mechanism
Change in a homeostatically control factor triggers a response that seeks to restore the factor to normal by moving the factor in the opposite direction of its initial change or it is a pathway where the response opposes or removes the signal.
If the results suppress or stops the original signal then it is said to be negative feed back mechanism.
Most of the mechanisms of the body belongs to this category

14. Negative Feedback

15. Negative Feedback Baroreceptors (sensor)
Increased arterial pressure
Baroreceptors (sensor)
Inhibit vasomotor center in medulla
Decreased impulses to heart &blood vessels
Decreased pumping activity of heart and V.D
Decreased blood pressure

16. Negative Feedback
Increased CO2 in tissue fluid Excites respiratory center Increased rate of breathing More CO2 is expired Decreased CO2 in tissue fluid

17. Positive Feedback
The output is continually enhanced or amplified so that the controlled variable continues to be moved in the direction of the initial change or a pathway in which the response reinforces the stimulus.
It is also precisely defined as “if the response enhances the original stimulus it is called positive feed back mechanism.
It is also called vicious cycle in some cases.

18. Positive Feedback
Positive feedback

19. Positive Feedback
Blood vessel ruptured Clotting factors activated in clot itself Activated clotting factors activate inactivated clotting factors as an enzyme Clot formed and bleeding stopped

20. Positive Feedback
Onset of labour Oxytocin released from hypothalmus Increased uterine contractions Baby’s head pushed through cervix Stretch of cervix More oxytocin released

21. Negative and Positive Feedback

22. Feedforward Mechanism
It brings about a compensatory response in anticipation of a change in a regulated variable.
In this mechanism our body gives response prior to signals sent by brain.
Examples
Production of saliva in the mouth when we see the food.
Secretion of HCL in stomach when we engulf the food.
Drawback of our hand instantly when we touch a hot pot.

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