Homeostasis

1. Introduction to Physiology
Dr Sunil Dhungel, Department of Clinical
Physiology , NAIHS-COM, Kathmandu,
The discipline that supports modern medicine –
so important that there is a Nobel Prize for it !

2. What is Physiology?
• Physiology: biological sciences dealing with
how the body functions at the various levels
of organization / Study of the function of all
living organism.
• Human physiology: preclinical sciences
dealing with normal life phenomena of the
human body.
• Goal of physiology:
explain the physical and chemical factors that
are responsible for the origin, development
and progression of life.

3. Physiology ……………
Physiology: (phy, nature; logos, discourse)
• Thales of Miletos First physiologist
• Modern sense - William Harvey(1578-1657)
“Physiology” = Herman Boerhave (1660-1738)
• Physiology emerged from the ancient
scientific and philosophical disciplines of the
Ayurveda (“science of life”)
• The Father of modern Physiology:
Claude Bernard (1813-1878)
• Nepali : “मानब शारीरक्रिया बबज्ञान”

4. Human Physiology
Deals-Molecules
- Sub cellular component
- Organ-system & their
interaction
•The basis for
-Pathology
-Pharmacology
-Immunology
-Biochemistry
-Microbiology
Human physiology
(medical Physiology)
links the Basic
Medical sciences to
Clinical Medicine

5. Why do we study Physiology ?
Understand the physiologic principle underlie
normal function in order to cure the
impairments.

6. Organization of the human body
Cells
Tissues
Organs
Organ
systems
Organisms
(Human body)

7. • Multicellular organism: Cell-tissue-organs-
systems
• The optimum condition/constancy required for
smooth functioning of the body : Homeostasis
(Walter canon)
“Dynamic self-regulation”.
- All systems function together to help the
human body to maintain homeostasis
- “A person who is in good health is in a state of
Homeostasis”
Organization of the human body

8. Stable Internal environment ‘milieu interieur’
(Claude Bernard) = Homeostasis
Role of System for the regulation of homeostasis
1.ECF fluid transport system (circulatory system)
2.Origin of nutrients in ECF (respiratory/ GI
system)
3.Changes in usable form –(Hepatobiliary system)
4.Removal of metabolic end product – (kidney,
respiratory)
5.Regulation of Body function ( NS, Endocrine,
immune, Integumantary, reproduction )
Organization of the human body

9. Homeostasis
1. Dynamic equilibrium
2. In spite of multiple stimuli
3. Maintained by negative feedback
The feedback signals from controlled
system produces effect opposite to the
action of the control system.

10. Homeostasis & Controls
•Successful
compensation
•Homeostasis
reestablished
•Failure to compensate
•Pathophysiology
•Illness
•Death

11. Regulation of the Body Functions
Regulation- the ability of an organism to maintain a stable
internal conditions in a constantly changing environment
Three types:
1. Chemical (hormonal) Regulation- a regulatory process
performed by hormone or active chemical substance in
blood or tissue.
-It response slowly, acts extensively and lasts for a long time.
2. Nervous Regulation- a process in which body functions
are controlled by nerve system
- Pathway: nerve reflex
- Types: unconditioned reflex and conditioned reflex

12. - Example: baroreceptor reflex of arterial blood pressure
Characteristics: response fast; acts exactly or locally, last for a
short time
3. Autoregulation – a tissue or an organ can directly respond to
environmental changes that are independent of nervous and
hormonal control
Characteristics：Amplitude of the regulation is smaller than
other two types.
Extension of the effects is smaller than other two types.
Regulation of the Body Functions

13. Basic components of a feedback
system
1. A receptor :detects changes (stimuli) in
the body.
2. A control center : determines a set point
for a normal range.
3. An effector : causes the response
determined by the control center.

14. Negative feedback

15. Characteristics of Control system
Negative feedback system
-Effector response is –ve to the initiating
Stimulus ( disturbance)
= BP control, temperature regulation,
regulation of oxygen, carbon dioxide
Negative feedback

16. Positive feedback system
A REGULATORY MECHANISM IN
WHICH THE RESPONSE TO A
STIMULUS, IN A CONTROL SYSTEM,
CAUSES THE CONTROLLED VARIABLE
TO MOVE FARTHER FROM THE
SET POINT.

17. Positive feedback system
An unusual of phenomena of control
system
• Sex hormone during ovulation
• Contraction of the uterus during
childbirth (parturition).
• Defecation
• Blood coagulation
• Na+ inflow in genesis of nerve signals

18. Importance- does not lead to stability
1) Enhance the action of original stimulus or
amplify or reinforce change, promote an
activity to finish
2) It is known as a vicious circle because it
can lead to instability or even death
Positive feedback system

19. Feed-forward control
Concept: a direct effect of stimulus on the
control system before the action of
feedback signal occurs.
Here the direct effect of the stimulus is
termed disturb signal or interfere signal.
Example: Shivering before diving into the
cold water

20. Significance of Feedback-forward :
adaptive feedback control.
makes the human body to foresee and adapt
the environment promptly and exactly
(prepare the body for the change).

21. • Additional complexities in control
system
Servomechanism
-Set point not fixed ( stretch reflex)
Coupling
Two control system couple
= hypoxia- RR, BP
Physiological Condition
Childhood, Adult, Old, Male,
Female, Pregnancy, Lactation, Rest,
Exercise, Environmental temperature,
Altitude
Feedback system

22. Physiology at NAIHS-COM
Three missions:
1.Teaching 2. Research 3. Patient care

23. At NAIHS-COM
At the end of phase I
How does the body function during the normal
demands of everyday life, and during stressful
situations like exercise, or working in extreme
environments?
How oxygen is supplied to the body?
How general and special sensory information are
perceived and processed by the body?

24. At NAIHS-COM
At the end of phase I
How hunger and thirst is regulated?
How reproduction and higher intellectual
functions like learning and memory is
coordinated?
How blood pressure and body temperature is
maintained?

25. At NAIHS-COM
At the end of phase I
How do body systems fail in diseases such as
diabetes, hypertension, kidney failure and
neurodegeneration?
How might these conditions be alleviated and
cured?

26. At NAIHS-COM
At the end of phase I
Identification of human blood cells, their
characteristics, blood grouping, and other
practical skills of Hematology
Clinical Examination of Sensory and Motor
System
Blood Pressure Measurement
Estimation of Oxygen Consumption

27. At NAIHS-COM
At the end of phase I
Reproductive Biology and Experimental
Endocrinology
Recording and interpretation of :
Electrocardiography (ECG) Electromyography
(EMG) , Electroencephalography (EEG) ,
Autonomic Function Test (AFT)

28. At NAIHS-COM
Knowledge of physiology will be achieved by:
as per TU curriculum
Conventional Learning Experience (CLE)
Laboratory exercise (Labex), Practical
Problem Base Learning (PBL)
Correlation seminar
as per departmental activities :
Small Group Discussion (SGD), tutorial
Continue Medical Education (CME)
Journal Club
Research

29. At NAIHS-COM
Organization of Human Physiology Department
Undergraduate teaching lab:
• Hematology laboratory
• Clinical Physiology laboratory
• Skill laboratory
Research lab:
• Neuroendocrine laboratory
• High altitude laboratory
• Animal house

30. Next: Cell membrane: composition, structure,
properties, functions
Rainbow bridge, Tokyo ©sunil