1. Introduction to Human Physiology Abdul Aleem Khan

2. Le Milieu Intérieur
And
Homeostasis I and II

3. STRUCTURE
FUNCTION
WHAT IT “IS”
HOW IT “WORKS”

4. What is human Physiology
A branch of science that deals with the functioning of Human body
How does the heart beat ?
How do we breathe ?
How do we see ?
How do we remember ?
How do we move ?
How do we reproduce?

5. How cells (like muscle, nerve) function?
To answer these global questions it is essential to understand that the functional unit of the body is the cell.
How cells (like muscle, nerve) function?
And how similar and dis-similar types of cells work together at various organisational levels (integration)  as a whole organism
All most all life processes are governed by laws of physics and chemistry

6. Divisions of Physiology
Integumentary Physiology (system)
Cardiovascular Physiology (system)
Respiratory Physiology (system)
Gastrointestinal Physiology (system)
Renal Physiology (system)
Reproductive Physiology (system)
Musculo-skeletal Physiology (system)
Neurophysiology Nervous system
Endocrine Physiology (system)
Immune Physiology (system)

7. Various levels of structural organization
Atoms
Molecules
Organelles
Cells
Tissues
Organs
Systems
Organism

8. Figure 1-1: Levels of Organization and Related Fields of Study

9. A Cell

10. Cell theory
The cell is the basic structural and functional unit of living organisms
The activity of an organism depends on both the individual and collective activity of its cells
The biochemical activities of cells are dictated by their specific subcellular structures (principle of complementarity)
Continuity of life has a cellular basis (cells come from cells)

11. Cell Diversity
There is really no “typical” cell. Cells have different shapes, different sizes, different functions, different life spans.
Stem cells is pluripotent.
Examples of Specialized cells:
Many different types of blood cells
Three different types of muscle cells
Fat Storage cells
Nerve cells that transmit electrical impulses
Cells for reproduction

12. Cells internal Environoment

13. “La fixité du milieu intérieur est la condition de la vie libre.”
Claude Bernard
( )
“La fixité du milieu intérieur est la condition de la vie libre.”
“The fixity of the internal environment is the condition for free life.”

14. Internal Environment
Claude Bernard in 1829 said: The proper functioning
of the cells depends on precise regulation of
the composition of their surrounding fluid.
Surrounding fluid = Internal environment
= Le Milieu interier

15. Internal Environment

16. Body water Water is main solvent in living cells
Hydrophilic molecules dissolve in water
Hydrophobic molecules do not dissolve in water
Amphiphilic - molecule part hydrophilic/part hydrophobic
Body Water
Intracellular fluid
(inside cells)
Extracellular fluid
(outside cells)
Plasma
(inside
blood vessels)
Interstitial Fluid
(outside
blood vessels)

17. Chemical composition of body
Major Elements % body wt
Oxygen %
Carbon %
Hydrogen %
Nitrogen %
Mineral Elements
Sodium %
Potassium %
Chloride %
Calcium %
Magnesium %
Phosphorus %
Sulphur %
Trace Elements
Iron %
Zinc %
Water
= 60% adult male
= 50% adult female
Principal organic constituents
carbohydrates  sugars
fats  fatty acids
proteins  amino acids
nucleic acids  nuclotides

18. Organ system Interrelationship
Nutrients and oxygen are distributed by the blood
Metabolic wastes are eliminated by the urinary and respiratory systems

19. Co-ordination of Organ System

20. Maintenance of constancy of the Internal Environment
Homeostasis
Maintenance of constancy of the Internal Environment
Walter Cannon
(1929)

21. Closed Loop Systems (Feedback Systems)
Control Systems
Open Loop Systems
Control center
Effector
Controlled
variable
Closed Loop Systems (Feedback Systems)
Control center
(Set point)
Effector
Controlled
variable
Sensor
Feedback Systems are of two types: Negative feedback Positive feedback

22. Maintenance of constancy of the Internal Environment
Homeostasis
Maintenance of constancy of the Internal Environment

23. Physiological variables maintained by controlled systems

24. Homeostasis
Process of maintaining the composition of the internal body compartments within fairly strict limits (ion concentrations, pH, osmolarity, temperature etc).
Require regulatory mechanisms to defend against changes in external environment and changes due to activity.
Cellular homeostasis - intracellular fluid composition
Organismal homeostasis - extracellular fluid composition.
Control system designed to maintain level of given variable (concentration, temperature, pressure) within defined range following disturbance.

25. Negative feedback loop requires
Sensor (Detector): specific to variable needing to be controlled
Comparator (Control system): reference point for sensor to compare against
Effector: if sensor  comparator  Error Signal  restore variable to desired level
Comparator
(reference point)
Effector
Controlled
variable
Sensor
Disturbance
Error
signal

26. Homeostasic Setpoint Homeostatic range -oscillation around setpoint
Change in setpoint
1. Acclimatization 2. Biorhythms

27. Negative feedback System Negative feedback System
The response reverses
the original stimulus.
Example:Blood pressure and
blood glucose regulation
The response enhances
the original stimulus
Example child birth
Negative feedback System

28. Maintenance of body temperature
Composed of
Detector
Control system
Effector
The effector response
Decreases or increases
the effect of the original
stimulus

29. Negative feedback System Receptors: Baroreceptors
Stimulus: change in BP
Receptors: Baroreceptors
Control Center: Brain
Effector: Heart

30. Negative feedback System

31. Negative feedback System

32. Negative feedback System

33. Limitation of negative feedback
Negative feedback control is initiated after variable is disturbed
Amount of correction to be applied, is assessed by magnitude of error signal  incomplete correction
Overcorrection  oscillations in controlled variable
Disadvantages overcome by multiple regulatory mechanisms.
Regulation of blood [glucose]
Insulin   [glucose]blood
Glucagon   [glucose]blood

34. Positive feedback
Negative feedback - error signal  reduces deviation from reference point
Positive feedback - error signal  increases deviation from reference point (vicious circle)
Error
signal
controlled
variable
disturbance
effector
sensor +

35. Positive feedback System
Stimulus: stretch of the uterus
Receptors: stretch receptors (cervix)
Control Center: Brain
Effector: Uterus

36. Positive feedback System

37. Homeostasis
Homeostasis is the ability to maintain a relatively stable internal environment in an ever-changing outside world.
The internal environment of the body is in a dynamic state of equilibrium.
Concepts of homeostasis dynamic.
Chemical, thermal, and neural factors interact to maintain homeostasis.