Cell Physiology Homeostasis and Immunity PDF - UQU

CELL PHYSIOLOGY Homeostasis and Immunity WEEK- 8 ©UQUMed,Year3 2/12/2025  2 Objectives By the end of this lecture, the student should be able to: o Ex...

CELL PHYSIOLOGY Homeostasis and Immunity WEEK- 8 ©UQUMed,Year3 2/12/2025  2 Objectives By the end of this lecture, the student should be able to: o Explain homeostasis, and negative & positive feed back mechanisms o Identify the immune system, non-specific and specific defense mechanisms. o Describe the pillars of inflammation, and the innate and acquired (adaptive) immunity o Demonstrate the cell-mediated and the antibody-mediated immunity o Identify the types of acquired immunity, the five types of antibodies, and the different types of hypersensitivity, as well as the factors affecting the immune response  3 Outlines  Homeostasis  Negative & positive feedback mechanisms  The lymphatic system  Non-specific and specific defense mechanisms  First & second line of defenses  Innate and acquired (adaptive) immunity  Inflammation  Cell-mediated immunity  Antibody-mediated immunity (humoral)  Five types of antibodies  Types of acquired immunity  Hypersensitivity  Factors affecting immune response  HOMEOSTASIS 4 HOMOIOS = Same STASIS = Standing Homeostasis thus means “Standing or Staying the same”. In other words homeostasis means a condition that remains same (constant) inside the body. Homeostasis is an important condition for the survival of body cells. These observations were first of all made by Claude Bernard (1813-1878), a French Physiologist and later on confirmed by Walter B. Cannon (1871-1945), a famous American Physiologist Walter B. Cannon very simply defined homeostasis as the maintenance of the constant internal environment. ©UQUMed, Year 2 2/12/2025  Examples of Homeostasis: 5  Temperature of blood inside the body is averagely 370C. In different physiological conditions it varies slightly above or below this point. Thus the homeostasis for blood is 370C.  Homeostasis for glucose concentration in blood in normal healthy conditions ranges from 80-100 mg glucose per 100 ml. of blood.  In different physiological conditions, it varies slightly above or below this level. Thus the homeostasis for blood glucose level is about 80-100 mg/100 ml of blood. ©UQUMed, Year 2 2/12/2025  MECHANISM OF ACTION OF HOMEOSTASIS (CONTROL SYSTEM) 6 Homeostasis is operated by the control system known as “Feedback mechanism” which is classified into two types: 1: Negative Feed Back Mechanism It means that if the activity of a particular system is increased, the control system will immediately reduce the activity of that particular system to maintain homeostasis. ©UQUMed, Year 2 2/12/2025  7 Example: (Negative Feed Back Mechanism)  Thyroxin hormone is secreted by the thyroid gland under the influence of another hormone Thyroid Stimulating Hormone (TSH), secreted by the pituitary gland.  Whenever the secretion of Thyroxin is increased, secretion of TSH from the pituitary gland is decreased. As a result, secretion of Thyroxin is also decreased.  Thus a normal level of Thyroxin is maintained in the body. ©UQUMed, Year 2 2/12/2025  Negative Feed Back Mechanism 8 Thyroxin hormone ©UQUMed, Year 2 2/12/2025  POSITIVE FEED BACK MECHANISM 9 In this system a stimulus, progressively increases the response, so that as long as the stimulus is continued, response is progressively being amplified. Example: (Positive Feed Back Mechanism) Coagulation of Blood Whenever a blood vessel is ruptured and the blood is shed, immediately 4 steps occur to stop the blood shed, called blood coagulation: 1. Prothrombin activator is formed. 2. It converts prothrombin into Thrombin 3. Thrombin converts Fibrinogen into Fibrin 4. Formation of the fibrin stops the blood shed and blood coagulation occurs. ©UQUMed, Year 2 2/12/2025  Positive Feed Back Mechanism Coagulation of Blood 10 Factor II = prothrombin Factor XIII = fibrin stabilizing factor ©UQUMed, Year 2 2/12/2025  HOMEOSTASIS AND CONTROL SYSTEM 11 ©UQUMed, Year 2 2/12/2025  12 The Immunity ©UQUMed, Year 2 2/12/2025  Basic immunology 13 The study of the physiological mechanisms which enable the body to recognize materials as foreign and to neutralize, eliminate, or metabolize them without injury to the host tissue. ©UQUMed, Year 2 2/12/2025  the lymphatic system 14 consists of ▪ Lymph vessels ▪ Lymph nodes and other lymphatic tissues ▪ Spleen ▪ Thymus gland ▪ Red bone marrow Function of lymphatic system 1- Draining excess interstitial fluid 2- transporting dietary lipids. 3- carrying out immune response ©UQUMed, Year 2 2/12/2025  15 lymphoid organs divide according to their function into : Primary Lymphatic organs:- a. Thymus gland: responsible for differentiation of immature lymphocytes into T-cells. b. red bone marrow: responsible for differentiation of B-cells. Secondary Lymphatic organs: the sites where most immune responses occur. ©UQUMed, Year 2 2/12/2025 Pathogen: an infectious agent that causes disease. 16 Infectious disease :occurs when a microorganism succeeds in evading host defenses to establish a local site of infection and replication. Defense mechanisms ▪ Non-specific defense mechanisms (innate or natural immunity) → protect against any dangers. ▪ Specific defense mechanisms (specific immunity or acquired immunity) → protect against only one specific antigen. ©UQUMed, Year 2 2/12/2025  Non-specific defense mechanisms 17 (innate or natural immunity) include:- First Line of Defense : Physical Factors: Epidermis of skin, mucous membranes, mucus; hairs, cilia , lacrimal apparatus, saliva, urine, defecation and vomiting Chemical Factor: Sebum, lysozyme, gastric juice and vaginal secretions ©UQUMed, Year 2 2/12/2025  Second Line of Defense: 18 1- Antimicrobial Proteins. 2-Natural killer (NK) cells. 3-phagocytes. 4-inflammation. 5-Fever. ©UQUMed, Year 2 2/12/2025  19 Which one of the following is a primary lymphoid organ: a) Lymph nodes b) Spleen c) Peyer's patches d) Tonsils e) Thymus gland ©UQUMed, Year 2 2/12/2025  Second Line of Defense: 20 1- Antimicrobial Proteins: Interferons (IFNs): Protect uninfected host cells from viral infection Complement system : System of about 30 proteins. Causes cytolysis of microbes, promotes phagocytosis, and contributes to inflammation. Transferrins: Inhibit growth of certain bacteria by reducing the amount of available iron. 2- Natural killer (NK) cells: Kill infected target cells by releasing granules that contain perforin and granzymes ©UQUMed, Year 2 2/12/2025  3- Phagocytes: 21 are cells that protect the body by ingesting harmful foreign particles, bacteria, and dead or dying cells. the phagocytic cells within tissues :as Macrophages and dendritic cells are immune cells (phagocytes) that reside within the tissue Neutrophils are phagocytes that reside in the blood but can migrate to tissue during inflammation. ©UQUMed, Year 2 2/12/2025  The Immune System 22 ©UQUMed, Year 2 2/12/2025  4-inflammation : 23 the inflammatory response: is characterized by : -Redness -heat -swelling -pain - loss of function Inflammation confines and destroys microbes and initiates tissue repair 5-Fever: intensifies the effects of interferons. inhibits growth of some microbes. speeds up body reactions that aid repair. ©UQUMed, Year 2 2/12/2025  24 cell-mediated immunity antibody-mediated (humoral) immunity ©UQUMed, Year 2 2/12/2025  cell-mediated immunity 25  T lymphocytes provide cell-mediated immunity  T- lymphocytes → recognize &bind antigen particles that processed by antigen presenting cells and differentiate into 4main types: 1- helper T- lymphocytes → release cytokines to support cytotoxic T and B lymphocytes. 2- cytotoxic T- lymphocytes → bind antigen and destroy it. 3- memory T- lymphocytes → long-lived and provide immunity to the same antigen. 4- suppressor T- lymphocytes → turn off the immune response ©UQUMed, Year 2 2/12/2025  Cell-mediated immunity 26 ©UQUMed, Year 2 2/12/2025  Antibody-mediated (humoral) immunity 27  B lymphocytes provide antibody- mediated (humoral) immunity B lymphocytes → recognize and bind antigen (foreign) particles and differentiate into 2 main types: 1-Memory B lymphocytes → long-lived and provide immunity to the same antigen. 2- Plasma cells → produce & release antibodies that bind to the antigen & inactivate (neutralize) it. ©UQUMed, Year 2 2/12/2025  Antibody-mediated (humoral) immunity 28 ©UQUMed, Year 2 2/12/2025  Antibodies 29  are synthesized by plasma cells and released into plasma or other body fluids.  Five types of antibodies. ©UQUMed, Year 2 2/12/2025  Summary of types of aquired immunity 30 ©UQUMed, Year 2 2/12/2025  Abnormal immune function 31  Hypersensitivity :  it is powerful immune response to an antigen.  For mechanism for hypersensitivity:  Type I: Immediate (anaphylactic) hypersensitivity (Peanut allergy)  Type II: Cytotoxic hypersensitivity: (RA, transfusion reaction, hemolytic disease of newborn.  Type Ill: Immune Complex: glomerulonephritis.  Type IV: Delayed type hypersensitivity: graft rejection, nickel allergy. ©UQUMed, Year 2 2/12/2025  Hypersensitivity: 32 ©UQUMed, Year 2 2/12/2025  Factors affecting immune response: 33 1-Age  very old and very young subjects are more susceptible to disease. 2- Nutrition  dietary deficiency → immune dysfunction.  direct toxic effects  allergic reactions. 3- Stress  lymphoid atrophy.  decreased phagocytosis.  decreased Ig A secretion along with an increase in respiratory infections. ©UQUMed, Year 2 2/12/2025  Summary 34  Homeostasis is a concept refers to stability or balance in a system. It is the body's attempt to maintain a constant internal environment  Innate immunity operates in conjunction with acquired immunity and is characterized by rapid response to aggression, being the organism first line of defense. Its mechanisms include physical, chemical and biological barriers, cellular components, as well as soluble molecules.  Cell-mediated immunity is the core of the adaptive immune response which results in the generation of antigen-specific effector T-cells. A variety of effector T-cells sub-types are generated during an adaptive response and responsible for a direct killing of infected cells or induction of effector functions by other immune cells.  Humoral immunity results in the release of antigen-specific antibodies that target an invading microbe. This response is largely carried out by the help of T-cells and thus in part depends on successful cell- mediated immunity.  35 References 1) Medical Physiology by Guyton and Hall, 12th edition 2) Review of Medical Physiology by Ganong W. F. 3) PubMed database