Physiology Introduction & Homeostasis PDF

Introduction Physiology: is the study of the functioning of the normal body, and is responsible for describing how various systems of the human body work to maintain life and health of the individual. Anatomy: is the study of the structure of the body and the physical relationships involved b...

Introduction Physiology: is the study of the functioning of the normal body, and is responsible for describing how various systems of the human body work to maintain life and health of the individual. Anatomy: is the study of the structure of the body and the physical relationships involved between body parts.  Homeostasis The maintenance of constant conditions in the internal environment = ECF. The ECF is the same in different parts of the body because: 1. Rapid exchange of solutes and water between blood and Interstitial fluid. 2. Rapid circulation of blood. 3. Very near capillary to any cell.  Homeostasis Factors homeostatically regulated include: Concentration of nutrient molecules. Concentration of O2 and CO2. Concentration of waste products. pH. Concentration of water, salt, and electrolytes. Volume and pressure. Temperature.  Homeostasis Homeostatic regulation involves three parts: 1) The receptor. 2) The control center. 3) The effector. The receptor receives information that something in the environment is changing. The control center or integration center receives and processes information from the receptor. and lastly, the effector responds to the commands of the control center by either opposing or enhancing the stimulus.  Homeostasis Interdependent relationship of cells, body systems, and homeostasis: Homeostasis is essential for the survival of cells. Body systems maintain homeostasis, and cells make up body systems. This relationship serves as the foundation for today physiology. 7  Homeostatic Control Systems Body System Contributions to Homeostasis 1. Circulatory System 1. Carries materials from one part of the body to another. 2. Digestive System 1. Breaks down dietary food into smaller molecules that can be distributed to body cells. 2. Transfers water and electrolytes from external environment to internal environment. 3. Eliminates undigested food residues to external environment in the feces. 3. Respiratory System 1. Gets O2 from and eliminates CO2 to the external environment. 2. Important in maintenance of proper pH of internal environment. 8 Body System Contributions to Homeostasis 4. Urinary System 1. Removes excess water, salt, acid, and other electrolytes from plasma and eliminates them in urine. 5. Skeletal System 1. Provides support and protection for soft tissues and organs. 2. Serves as storage reservoir for calcium. 3. Along with muscular system enables movement of body and its parts. 4. Bone marrow is ultimate source of all blood cells. 6. Muscular System 1. Moves the bones 7. Integumentary System 1. Serves as outer protective barrier. 2. Important in regulating body temperature. 9 Body System Contributions to Homeostasis 8. Immune System 1. Defends against foreign invaders and against body cells that have become cancerous. 2. Paves way for repairing or replacing injured or worn- out cells. 9. Nervous System 1. Controls and coordinates bodily activities that require rapid responses. 2. Detects and initiates reactions to changes in external environment. 10. Endocrine System 1. Secreting glands of endocrine regulate activities that require duration rather than speed. 2. Controls concentration of nutrients and, by adjusting kidney function, controls internal environment’s volume and electrolyte composition 10  Homeostatic Control Systems Reproductive System: Not essential for homeostasis (not essential for survival of individual cells) Is essential for survival of the human species. 11  Homeostatic Control Systems Control Systems are Grouped into Two Classes: 1. Intrinsic controls Local controls that are inherent in an organ. Operate in all cells to help control intracellular function as well as extracellular function. 2. Extrinsic controls Regulatory mechanisms initiated outside an organ. Operate throughout the entire body to control the interrelations between the organs. Accomplished by nervous and endocrine systems. 12  Control Of Homeostasis 1- Nervous mechanisms: It is a rapid regulatory mechanism, that regulates body functions by nerve impulses carried by nerve fibers. e.g.: ABP (arterial blood pressure) regulation by vasomotor center (VMC).  Control Of Homeostasis 2- Hormonal mechanisms: It is a slow regulatory mechanism, that regulates body functions by hormones released from endocrine glands. e.g.: To maintain glucose level constant.  Feed Back Control Of Homeostatic Mechanisms A) Negative feedback control: In which the resultant effect of a function, inhibit the resultant function. (opposes an initial change) e.g.: 1- Regulation of CO2 in blood by lung, when CO2 increases in arterial blood, the pulmonary ventilation increases.  Feed Back Control Of Homeostatic Mechanisms 2- ABP regulation by (VMC): increase ABP above normal, inhibits the VMC which inhibit the heart + vasodilatation of the blood vessels. 3- Regulation of blood glucose level: If blood glucose is increased above normal, insulin hormone is secreted to maintain its normal level.  Feed Back Control Of Homeostatic Mechanisms B) Positive feedback control : In which the resultant effect of a function, stimulates the resultant function. (amplifies an initial change) e.g.: Parturition: in which the descent of the baby, stretches the uterine cervix that in turn causes reflex uterine contraction and more descent and so on.  Disruptions in Homeostasis Can lead to illness and death. Pathophysiology: Abnormal functioning of the body associated with disease. 19  Levels of Organization in Body The basic living unit of the body is the cell. Each type of cell is specially adapted to perform one or a few particular functions. 20  Total Body Water = 60 % of the total body weight. It is divided into: 1. Intracellular fluid (ICF 40 % ). 2. Extracellular fluid (ECF 20%) composed of: 1. Interstitial fluid (ISF) (15 %). 2. Plasma (5 %).  Physiological Variations in Total Body Water 1. It is greater in young infants (75% of total body weight). 2. It is less in females because of the higher fat content. 3. It is less in obese peoples. 4. It is less in old age.  Effects of Water Loss Loss of 1% of TBW Thirst sensation. Loss of 5% of TBW Dehydration. Loss of more than 20% of TBW Death.