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

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

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

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

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

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

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

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

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

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

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

Body Systems

Body Systems

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

Components of the extracelluar fluid ( internal environment)

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

Homeostasis

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

Role of Body Systems in Homeostasis

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

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

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

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

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

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

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