1. Homeostasis: The Foundation of Physiology
بسم الله الرحمن الرحيم
Homeostasis: The Foundation of Physiology
Prepared by
Dr.Mohammed Sharique Ahmed Quadri
Assistant prof. Physiology
Al Maarefa College

2. Physiology Study of Functions of Living Things
Two approaches to explain body functions
Emphasis on purpose of body process (Why)
Explanations are in terms of meeting a bodily need
Emphasis on Mechanism (How)
Explanations are in terms of cause and effect sequences
Body is viewed as a machine

3. Organization of the Body
Levels of organization
Chemical
Molecules composed
of atoms
Cellular
Cells are basic unit
of life
Tissue
Organ
Body system
Organism

4. Basic Cell Functions
Obtain nutrients and oxygen from surrounding environment
Perform chemical reactions that provide energy for the cell
Eliminate carbon dioxide and other wastes to surrounding environment
Synthesize needed cellular components

5. Basic Cell Functions
Control exchange of materials between cell and its surrounding environment
Sensing and responding to changes in surrounding environment
Reproduction
Exception
Nerve cells and muscle cells lose their ability to reproduce during their early development

6. Tissues
Groups of cells with similar structure and specialized function
Four primary types of tissues
Muscle tissue
Nervous tissue
Epithelial tissue
Connective tissue

7. Tissues
Muscle tissue
Specialized for contracting which generate tension and produce movement
Three types of muscle tissue
Skeletal muscle
Moves the skeleton
Cardiac muscle
Pumps blood out of the heart
Smooth muscle
Encloses and controls movement of contents through hollow tubes and organs

8. Tissues Nervous tissue Epithelial tissue
Consists of cells specialized for initiating and transmitting electrical impulses
Found in brain, spinal cord, and nerves
Epithelial tissue
Consists of cells specialized for exchanging materials between the cell and its environment
Organized into two general types of structures
Epithelial sheets
Secretory glands

9. Tissues Connective tissue
Connects, supports, and anchors various body parts
Distinguished by having relatively few cells dispersed within an abundance of extracellular material
Examples
Tendons
Bone
Blood

10. Organs
Consist of two or more types of primary tissues that function together to perform a particular function or functions
Example
Stomach
Inside of stomach lined with epithelial tissue
Wall of stomach contains smooth muscle
Nervous tissue in stomach controls muscle contraction and gland secretion
Connective tissue binds all the above tissues together

11. Body Systems
Groups of organs that perform related functions and interact to accomplish a common activity essential to survival of the whole body
Do not act in isolation from one another
Human body has 11 systems

12. Body Systems

13. Body Systems

14. Homeostasis
Defined as maintenance of a relatively stable internal environment
Does not mean that composition, temperature, and other characteristics are absolutely unchanging
Homeostasis is essential for survival and function of all cells
Each cell contributes to maintenance of a relatively stable internal environment

15. Components of the extracelluar fluid ( internal environment)

16. Homeostasis
Body cells are contained in watery internal environment through which life-sustaining exchanges are made
Extracellular fluid (ECF)
Fluid environment in which the cells live (fluid outside the cells)
Two components
Plasma, interstitial fluid
Intracellular fluid (ICF)
Fluid contained within all body cells

17. Homeostasis

18. Homeostasis Factors homeostatically regulated include
Concentration of nutrient molecules
Concentration of O2 and CO2
Concentration of waste products pH
Concentration of water, salt, and other electrolytes
Volume and pressure
Temperature

19. Role of Body Systems in Homeostasis

20. Homeostatic Control Systems
In order to maintain homeostasis, control system must be able to
Detect deviations from normal in the internal environment that need to be held within narrow limits
Integrate this information with other relevant information
Make appropriate adjustments in order to restore factor to its desired value

21. Homeostatic Control Systems
Control systems are grouped into two classes
Intrinsic controls
Local controls that are inherent in an organ
Extrinsic controls
Regulatory mechanisms initiated outside an organ
Accomplished by nervous and endocrine systems

22. Homeostatic Control Systems
Feedforward
Term used for responses made in anticipation of a change
Feedback
Refers to responses made after change has been detected
Types of feedback systems
Negative
Positive

23. Homeostatic Control Systems
Negative feedback system
Primary type of homeostatic control
Opposes initial change
Components
Sensor
Monitors magnitude of a controlled variable
Control center
Compares sensor’s input with a set point
Effector
Makes a response to produce a desired effect
Example
Blood pressure regulation
Temperature regulation

24. Homeostatic Control Systems
Positive feedback system
Amplifies an initial change
Do not occur as often as negative feedback system
Example
Uterine contractions become increasingly stronger until the birth of the baby

25. Disruptions in Homeostasis
Can lead to illness and death
Pathophysiology
Abnormal functioning of the body associated with disease

26. References Human physiology by Lauralee Sherwood, seventh edition
Text book physiology by Guyton &Hall,11th edition
Text book of physiology by Linda .s contanzo,third edition