Human Physiology Lecture 1 PDF

Introduction Prepaired by Jamil Mohanna Course Outline  ‫بسم اهلل الرمحن الرحيم‬ Chapter 1 Homeostasis: The Foundation of Physiology  Introduction To Physiology All the physiological activities we do are a sampling of the processes that occur i...

Introduction Prepaired by Jamil Mohanna Course Outline  ‫بسم اهلل الرمحن الرحيم‬ Chapter 1 Homeostasis: The Foundation of Physiology  Introduction To Physiology All the physiological activities we do are a sampling of the processes that occur in our bodies all the time just to keep us a life. Physiology: is the study of the function of the human body; “How the body work”. Physiology focuses on mechanisms of action: Approaches to explain the events that occur in the body: (1) Teleological approach: (1) Emphasizing the purpose of a body process. (2) In response to the Why? question. (3) Explain body functions in terms of meeting bodily needs. (2) Mechanistic approach: (1) Focus on a mechanistic approach. (2) Physiologists explain the How? question. (3) View the body as a machine whose mechanism of action explained in term of cause and effect sequences of physical and chemical processes. Example: Shivering. Structure and function are inseparable. Anatomy: is the study of the structure of the body. Physiological mechanisms are made possible by the structural design and relationships of the various body parts that carry out each of these functions. Levels of Organization in the body Body systems  Levels of Organization in the body How the body is structurally organized into a whole functional unit, from the chemical level to the total body(fig.1-1). The chemical level: various atoms and molecules make up the body. The human body is a combination of various chemicals. O2, C, H and N are the most common atoms in the body; about 96% of the total body chemistry. Atoms form molecules such as proteins, carbohydrates, fats and nucleic acids (see Appendix B of the text book). The cellular level: cells are the basic units of life. The cell is the smallest unit capable of carrying out the processes associated with life. The oily plasma membrane encloses the contents of each cell, and control movement of materials into and out of the cell, so the cell’s interior contains a different combination of atoms and molecules from the mixture of chemicals in the surrounding environment. Organisms are independent living entities, the single-celled organisms such as bacteria and amoebae, while the complex multicellular organisms such as trees and humans. Cells are the living building blocks, simpler multicellular forms; (such as a Hydra or a sponge) may all be similar. However, more complex organisms, such as humans, have many different kinds of cells e.g. muscle cells, nerve cells. During development of complex multicellular organisms such as humans, each cell differentiates, or becomes specialized to carry out a particular function.  Basic cell functions All cells, perform certain basic functions essential for survival of the cell, include the following: 1. Obtaining food (nutrients) and oxygen(O2) from the surrounding environment. 2. Use nutrients and O2 to provide energy for the cells, as follows: Food + O2 → CO2 + H2O + energy 3. Eliminating carbon dioxide (CO2) and other by-products, or wastes. 4. Synthesizing proteins and other components need for cellular structure, growth and carrying out particular cell functions. 5. Controlling to a large extent the exchange of materials between the cell and its surrounding environments. 6. Moving materials from one part of the cell to another in carrying out cellular activities, or through their surrounding environment. 7. Being sensitive and responsive to changes in the surrounding environment. 8. In the case of most cells, reproducing except nerve cells and muscle cells. Specialized cell functions: – Secretion of synthesized proteins; the gland cells of the digestive system secrete digestive enzymes. – The kidney cells are able to selectively retain the substances needed. – Muscle contraction. – Nerve cells generate and transmit electrical impulses.  The tissue level: tissues are groups of cells of similar specialization Cells of similar structure and specialized function combine to form tissues, of which there are four primary types: Muscle tissue is composed of cells specialized for contraction and force generation. There are three types: skeletal, cardiac and smooth muscles. Nervous tissue consists of cells specialized for initiating and transmitting electrical impulses. It is found in the central and peripheral nervous system. Epithelial tissue is made up of cells specialized for the specialized for the exchange of materials between the cell and its environment. It is organized into epithelial sheets and secretory glands. Glands are epithelial tissue derivatives that are specialized for secretion, there are two categories of glands: exocrine and endocrine. Connective tissue connects, supports and anchors various body parts; include loose connective tissue, tendons, bone, and blood. Except for blood, its cells produces elastin protein whose facilitates stretching and recoiling of tissue.  The organ level: an organ is a unit made up of several tissue types Organs are composed of two or more types of primary tissue organized together the perform a particular function or functions, the stomach is an example of an organ made up of all four primary tissue types. The body system level: a body system is a collection of related organs each system is a collection of organs that perform related functions and interact to accomplish a common activity that is essential for survival of the whole body. For example, the digestive system. The Human body has eleven systems: (fig. 1-3). The human body has eleven systems The human body has eleven systems  The organism level: The body systems are packaged together into a functional whole body The whole body of a multicellular organism is composed of the various body systems structurally and functionally linked together as an entity. Many complex body processes depend on the interplay among multiple systems. For example, regulation of blood pressure depends on coordinated responses among the circulatory, urinary, nervous, and endocrine systems. How these different levels word together to maintain life?  CONCEPT OF HOMEOSTASIS Why can’t the body cells live without performing specialized tasks and being organized according to specialized into systems that accomplish functions essential for the whole body’s survival? Because the vast majority of cells are not in direct contact with the external environment in which the organism lives. How is it possible for a muscle cell to make vital exchanges with the external environment with which it has no contact? The key is the presence of a watery internal environment with which the body cells are in direct contact and make life- sustaining exchange.  Body cells are in contact with a privately maintained internal environment The fluid collectively contained within all of the cells of the body is known as intracellular fluid (ICF) and the fluid outside the cells is referred to as extracellular fluid (ECF), which made up of two components: the plasma and the interstitial fluid. Cells can make life-sustaining exchanges with its own surrounding internal environment. In turn, various body systems accomplish the transfer of material between the external environment and the internal environment, examples: Digestive system, Respiratory system and Urinary system. Thus a body cell takes in essential nutrients from and eliminates wastes into its watery surroundings, just as an amoeba does.  Body systems maintain homeostasis, a dynamic steady state in the internal environment The body cells can live and function only when the extracellular fluid is compatible with their survival; thus the chemical composition and physical state of this internal environment must be maintained within narrow limits. Homeostasis is maintenance of a relatively stable internal environment. Homeostasis is essential for the survival of each cell, and each cell, through its specialized activities, contributes as part of a body system to the maintenance of the internal environment shared by all cells. When any factor starts to move the internal environment away from optimal conditions, the body systems initiate appropriate counteractions to minimize the change. External factor: temp. compensated by shivering, while internal factor:  temp. compensate by sweating and others. Thus homeostasis should be viewed not as a rigid, fixed state but as a dynamic steady state in which the changes that do occur are minimized by compensatory physiological responses, immediate or in long-term adaptations e.g. increased blood pressure during exercise include both of them through nervous and endocrine system.  Factors homeostatically regulated 1. Concentration of nutrient molecules. 2. Concentration of O2 and CO2. 3. Concentration of waste products. 4. pH, that affect nerves function and enzymes activity. 5. Concentration of water, salt and electrolytes. Cells do not function normally when they are swollen or shrunken, e.g. arrhythmia due to K+ deficiency. 6. Temperature. 7. Volume and pressure.  Contributions of the body systems to homeostasis 1) The circulatory system. 2) The digestive system. 3) The respiratory system. 4) The urinary system. 5) The skeletal system, provide support and protection. Also serves as a storage reservoir for calcium (Ca2+). 6) The muscular system, enable an individual to move toward food or away from harm, and involved in heat regulation via generating heat. 7) The integumentary system, important in the regulation of body temperature. 8) The immune system, defends against foreign invaders and cancerous cells. 9) Nervous system, controls and coordinates bodily activities that require swift responses. It is responsible for higher functions. 10. The endocrine system, regulate activities that require duration rather than speed, e.g. nutrients concentration, kidney function, internal environment’s volumes and electrolyte composition. 11) The reproductive system, for perpetuation of the species. So the body is a coordinated whole even though each system provides its own special contributions. Also be aware that the functioning whole is greater than the sum of its separate parts.  HOMEOSTATIC CONTROL SYSTEMS Homeostatic control systems, operate to maintain a given chemical or physical factor relatively constant around an optimal level. To maintain homeostasis, the control system must be able to: 1. Detect deviations from normal within narrow limits. 2. Integrate this information with any other relevant information. 3. Make appropriate adjustments. Homeostatic control systems may operate locally or body wide Homeostatic control systems can be: – Intrinsic (local) controls built into or are inherent in an organ, e.g. an exercising skeletal muscle, fall of O2 within the muscle acts directly of the smooth muscle on the walls of the blood vessels making it dilate, so increase blood flow and increase O2 supplying to the muscle itself. Intrinsic controls operate on the principle of feedback. – Extrinsic controls, which are regulatory mechanisms initiated outside an organ to alter the activity of the organ, for example; cardiovascular, nervous and endocrine systems restore elevated blood pressure. Extrinsic controls operate on the principles of feedback as will as feedforward mechanisms.  Negative feedback opposes and initial change and is widely used to maintain homeostasis In negative feedback, change in a homeostatically controlled factor triggers a response by moving the factor in the opposite direction of its initial change. A common example of negative feedback is control of room temperature (fig. 1-7). With positive feedback, the output is continually enhanced or amplified so that the controlled variable continues to be moved in the direction of the initial change. It is play an important role in certain instances as in the birth of a baby (by enhancing secretion of oxytocin hormone).  Feedforward mechanisms initiate responses in anticipation of a change Feedforward mechanisms, bring about a response in anticipation of a change in a regulated variable. For example, when a meal is still in the digestive tract, a feedforward mechanism increases the secretion of a hormone that will promote the cellular uptake and storage of ingested nutrients, so, this response limit the rise in blood nutrient concentration following absorption. Disruptions in homeostasis can lead to illness and death: When one or more of the body’s systems fail to function properly, homeostasis is disrupted, and all the cells suffer. The term Patho-physiology refers to the abnormal functioning of the body associated with disease.  ‫‪The End‬‬ ‫احلمد هلل رب العاملني‬ ‫‪Next‬‬ ‫‪Next‬‬