Homeostasis is the maintenance of a constant internal environment within an organism, crucial for survival, and is mediated by various physiological processes and feedback mechanisms. There are two types of feedback loops: negative feedback, which restores normal values, and positive feedback, which can exacerbate changes but is often regulated by negative feedback. Disruptions in homeostasis can lead to significant health issues, such as diabetes and hyperparathyroidism, highlighting the importance of effective feedback control in physiological regulation.

2. HOMEOSTASIS
BY: GROUP 7 (Roll No.76-88)

4. HOMEOSTASIS
 The term coined by American physiologist Walter Cannon
 homeo = same ; statis = standing
 Maintenance of a Nearly Constant Internal Environment

5. WHAT IF THERE IS CHANGE IN OUR
INTERNAL ENVIRONMENT ?
 Depending upon the degree of change;
• Discomfort
• Disease
• Damage
• Death
 So any significant change in the environment is harmful to an organism.

6. Extracellular Fluid – The
“Internal Environment”
 In the ECF, there are the ions and nutrients needed by the cells to maintain
life.
 Thus, all cells live in essentially the same environment – the ECF.
 Claude Bernard – The Father of Physiology introduced the term
‘milieu interieur’ for the internal environment.

7. HOMEOSTATIC MECHANISMS
 The various physiological processes which serve to restore the normal state ,
once it has been disturbed.
 They maintain constant:
• Concentration of Oxygen and Carbon dioxide
• Concentration of nutrients and waste products
• Concentration of salts and other electrolytes
• Volume and pressure of ECF

8. ALL ORGANS AND ORGAN SYSTEMS OF BODY
HELP IN MAINTENANCE OF HOMEOSTASIS
 Cardiovascular System
 Respiratory System
 Nervous System
 Endocrine System
 GI System
 Excretory System
 Skeletal System
 Integumentary System
 Reproductive System

9. FEEDBACK MECHANISMS
 A feedback mechanism is a cycle in which some proportion of output signal is “fed back”
to the input in order to control behaviour of some system.
 A feedback mechanism may operate at:
• Tissue level
• Organ level
• Organ system level
• Body level, integrating with other organ systems.
• Feedback mechanism can be:
• Negative feedback (more common)
• Positive feedback

10. COMPONENTS OF A FEEDBACK SYSTEM
 SENSOR (RECEPTOR) : Detects specific changes
(stimuli) in the environment.
 INTEGRATOR : Act to direct impulses to the place
where a response can be made
 EFFECTOR : Performs the appropriate responses.
FEEDBACK LOOP

11. NEGATIVE FEEDBACK
 Mechanisms that maintain the factor at some mean value.
 Reverse a change.
 Restore abnormal values to normal.

12. NEGATIVE FEEDBACK LOOP

13. EXAMPLE:
 BLOOD PRESSURE
 HORMONE REGULATION
(Growth Hormone Regulation)

14. POSITIVE FEEDBACK
 Strengthens or reinforces a change.
 Makes abnormal values more abnormal.
 Produces ‘Vicious Cycle’.
 But in the body a mild degree of positive feedback can be overcome by the
negative feedback control mechanisms of the body, and the vicious cycle fails
to develop.

15. POSITIVE FEEDBACK LOOP

16. EXAMPLES:
 ACTION POTENTIAL
 BLOOD CLOTTING
 PARTURITION
 LACTATION
 LH SURGE

17. NEGATIVE vs POSITIVE FEEDBACK

18. EFFECTIVENESS OF FEEDBACK CONTROL-
THE PRINCIPLE OF GAIN

19. APPLIED PHYSIOLOGY

20. TYPE 1 DIABETES MELLITUS
 Blood Glucose Homeostat ceases to function.
 Beta cells of the pancreatic islets are destroyed.
 Glucose sensor is absent and thus the Insulin level
in the blood remains at zero.
 Results in gluconeogenesis by the liver.
 Fatal if not treated.

21. HYPERPARATHYROIDISM
 Plasma ionised Calcium homeostat ceases to function.
 Over production of parathyroid hormone (Collipse Hormone).
 Leads to spontaneous fractures.
 Conformational changes in many cell surface proteins (Ion channels and
hormone or Neurotransmitter receptors)
 Lethargy, muscle weakness, anorexia, constipation and labile emotions.

22. HYPERNATREMIA – HIGH LEVELS OF
SODIUM IONS IN THE BLOOD
 ADH homeostat ceases to function.
 Body water homeostat is compromised.
 Daily water losses via exhaled air, feces and insensible
sweating.
 Zero blood ADH signal.
 Kidneys produce huge unchanging volumes of very dilute
urine, causing dehydration and death if not treated.