Physiology for Nursing Institute PDF Summary 2023-2024

Summary of Physiology 2023-2024 Summary of Physiology By staff members of Physiology department Sohag University 2019-2020...

Summary of Physiology 2023-2024 Summary of Physiology By staff members of Physiology department Sohag University 2019-2020 1 Summary of Physiology 2023-2024 Introduction What is physiology? it is a science concerned with studying: 1. Functions of different body systems. 2. How they perform their functions. 3. Factors affecting their functions. The human body consists of a number of systems, each system is formed of organs, each organ is formed of tissues and each tissue is formed of cells which is the structural unit of the body. Systems organs tissues cells The cell: Composed of a cell membrane and cytoplasm. Inside the cytoplasm there is: ✓ Nucleus: which contain the genetic material (DNA). ✓ Mitochondria: responsible for energy production inside the cell. ✓ Golgi apparatus. ✓ Lysosomes: containing proteolytic enzymes ✓ Ribosomes: responsible for protein synthesis. ✓ Centrosome: responsible for cell division. ✓ Rough and smooth endoplasmic reticulum. 2 Summary of Physiology 2023-2024 REGULATION OF BODY TEMPRATURE INTRODUCTION Living organisms are classified into two groups, depending upon the maintenance (regulation) of body temperature: 1. Homeothermic animals 2. Poikilothermic animals. „ HOMEOTHERMIC (WARM BLOODED) ANIMALS Homeothermic animals are the animals in which the body temperature is maintained at a constant level, irrespective of the environmental temperature. Birds and mammals including man belong to this category. They are also called warm blooded animals „ POIKILOTHERMIC (COLD BLOODED) ANIMALS Poikilothermic animals are the animals in which the body temperature is not constant. It varies according to the environmental temperature. Amphibians and reptiles are the poikilothermic animals. These animals are also called cold blooded animals. BODY TEMPERATURE MEASURMENT: Body temperature can be measured by placing the clinical thermometer in different parts of the body such as: 1. Mouth (oral temperature) 2. Axilla (axillary temperature) 3. Rectum (rectal temperature) NORMAL BODY TEMPERATURE Normal body temperature in human is 37°C (98.6°F), when measured by placing the clinical thermometer in the mouth (oral temperature). It varies between 35.8°C and 37.3°C (96.4°F and 99.1°F). „ TEMPERATURE AT DIFFERENT PARTS OF THE BODY Axillary temperature is 0.3°C to 0.6°C (0.5°F to 1°F) lower than the oral temperature. The rectal temperature is 0.3°C to 0.6°C (0.5°F to 1°F) higher than oral temperature. 3 Summary of Physiology 2023-2024 Physiological Variations 1. Age In infants, the body temperature varies in accordance to environmental temperature for the first few days after birth. It is because the temperature regulating syste does not function properly during infancy. In children, the temperature is slightly (0.5°C) more than in adults because of more physical activities. In old age, since the heat production is less, the body temperature decreases slightly. 2. Sex In females, the body temperature is less because of low basal metabolic rate, when compared to that of males. During menstrual phase it decreases slightly. 3. Diurnal variation In early morning, the temperature is 1°C less. In the afternoon, it reaches the maximum (about 1°C more than normal). 4. After meals The body temperature rises slightly (0.5°C) after meals 5. Exercise During exercise, the temperature raises due to production of heat in muscles. 6. Sleep During sleep, the body temperature decreases by 0.5°C. 7. Emotion During emotional conditions, the body temperature increases. 8. Menstrual cycle In females, immediately after ovulation, the temperature rises (0.5°C to 1°C) sharply. Pathological variation: Abnormal increase in body temperature is called hyperthermia or fever and decreased body temperature is called hypothermia. 4 Summary of Physiology 2023-2024 Heat Balance Regulation of body temperature depends upon the balance between heat produced in the body and the heat lost from the body. HEAT GAIN OR HEAT PRODUCTION IN THE BODY Various mechanisms involved in heat production in the body are: 1. Metabolic Activities Major portion of heat produced in the body is due to the metabolism of food stuffs. It is called heat of metabolism. Heat production is more during metabolism of fat. About 9 calories of heat is produced during metabolism of fats. carbohydrate metabolism produces 4.7 calories of heat. Protein metabolism produces 4.5 calories/L. 2. Muscular Activity Heat is produced in the muscle both at rest and during activities. During rest, heat is produced by muscle tone. Heat produced during muscular activity is called heat of activity. About 80% of heat of activity is produced by skeletal muscles. 3. Role of Hormones Thyroxin and adrenaline increase the heat production by accelerating the metabolic activities. 4. Radiation of Heat from the Environment Body gains heat by radiation. It occurs when the environmental temperature is higher than the body temperature. 5. Shivering Shivering refers to shaking of the body caused by rapid involuntary contraction or twitching of the muscles as during exposure to cold. Shivering is a compensatory physiological mechanism in the body, during which enormous heat is produced. 6. Brown Fat Tissue Brown adipose tissue is one of the two types of adipose tissues, the other being white adipose tissue. 5 Summary of Physiology 2023-2024 HEAT LOSS: Maximum heat is lost from the body through skin and small amount of heat is lost through respiratory system, kidney and GI tract. When environmental temperature is less than body temperature, heat is lost from the body. Heat loss occurs by the following methods: 1. Conduction Three percent of heat is lost from the surface of the body to other objects such as chair or bed, by means of conduction. 2. Radiation Sixty percent of heat is lost by means of radiation, i.e. transfer of heat by infrared electromagnetic radiation from body to other objects through the surrounding air. 3. Convection Fifteen percent of heat is lost from body to the air by convection. First the heat is conducted to the air surrounding the body and then carried away by air currents, i.e. convection. 4. Evaporation – Insensible Perspiration When water evaporates, heat is lost. Twenty two percent of heat is lost through evaporation of water. Normally, a small quantity of water is continuously evaporated from skin and lungs. We are not aware of it. So it is called the insensible perspiration or insensible 5. Panting Panting is the rapid shallow breathing, associated with dribbling of more saliva. In some animals like dogs which do not have sweat glands, heat is lost by evaporation of water from lungs and saliva by means of panting. BODY TEMPRATURE REGULATION Body temperature is regulated by the hypothalamus, which sets the normal range of body temperature. The set point under normal physiological conditions is 37°C. 6 Summary of Physiology 2023-2024 Hypothalamus has two centers which regulate the body temperature: 1. Heat loss center 2. Heat gain center. HEAT LOSS CENTER Heat loss center is situated in preoptic nucleus of anterior hypothalamus. Neurons in preoptic nucleus are heat sensitive nerve cells, which are called thermoreceptor.Stimulation of preoptic nucleus results in cutaneoub vasodilatation and sweating. Removal or lesion of this nucleus increases the body temperature. HEAT GAIN CENTER Heat gain is otherwise known as heat production center. It is situated in posterior hypothalamic nucleus. Stimulation of posterior hypothalamic nucleus cause shivering. The removal or lesion of this nucleus leads to fall in body temperature. MECHANISM OF TEMPERATURE REGULATION When Body Temperature Increases blood temperature also increases. Which when passes through hypothalamus, it stimulates the thermo receptors present in the heat loss center in pre optic nucleus. Now, the heat loss center brings the temperature back to normal by two mechanisms: 1. Promotion of heat loss 2. Prevention of heat production. 1. Promotion of heat loss When body temperature increases, heat loss center promotes heat loss from the body by two ways: i. By increasing the secretion of sweat: When sweat secretion increases, more water is lost from skin along with heat ii. By inhibiting sympathetic centers in posterior hypothalamus: This causes cutaneous vasodilatation. Now, the blood flow through skin increases causing excess sweating. 2. Prevention of heat production Heat loss center prevents heat production in the body by inhibiting mechanisms involved in heat production, such as shivering and chemical (metabolic) reactions. When Body Temperature Decreases 7 Summary of Physiology 2023-2024 When the body temperature decreases, it is brought back to normal by two mechanisms: 1. Prevention of heat loss 2. Promotion of heat production. 1. Prevention of heat loss When body temperature decreases, sympathetic centers in posterior hypothalamus cause cutaneous vasoconstriction. This leads to decrease in blood flow to skin and so the heat loss is prevented. 2. Promotion of heat production Heat production is promoted by two ways: i. Shivering: When body temperature is low, the heat gain center stimulates the primary motor center for shivering, situated in posterior hypothalamus near the wall of the III ventricle and shivering occurs. During shivering, enormous heat is produced because of severe muscular activities. ii. Increased metabolic reactions: Sympathetic centers, which are activated by heat gain center, stimulate secretion of adrenaline and noradrenaline. 8 Summary of Physiology 2023-2024 9 Summary of Physiology 2023-2024 Blood Composition of the blood: blood plasma 55% cells 45% plasma protiens red blood water 90% minerlas 0.9% others 7-8% corpuscles albumin 4.5% nutreints white blood cells globulins 2.7% waste products platelets fibrinogen 0.4% gaes hormones antibodies Functions of blood Blood has three main functions: transport, defense and regulation. 1) Transport Transport of oxygen (O2) from lungs to tissues and carbon dioxide (CO2), from tissues to lungs. Transport of Nutrients as glucose & amino acids. Transport of Waste products to be removed. 10 Summary of Physiology 2023-2024 Transport of Hormones from the glands in which they are produced to their target cells (regulation of metabolism) Transport of Heat from internal organs to the skin so as to help regulate body temperature. 2) Defense by the: White blood cells destroy invading microorganisms. Antibodies. 3) Regulation of: Water balance. pH. Minerals. Plasma 100 cc of plasma contain 7-8 gm plasma proteins which are Albumin 4.5gm Globulins 2.7gm Fibrinogen 0.4gm Site of synthesis of plasma proteins: Albumin and fibrinogen: formed only by the liver. Globulins: formed in the liver, spleen, bone marrow and lymph glands. Functions of plasma proteins 1. Maintenance of plasma colloidal osmotic pressure : This is achieved by plasma proteins mainly albumin. It is about (25-30 mmHg): This is important for regulation of water exchange between blood and tissues and hence regulation of blood volume. 2. Defense function: Because the antibodies are mainly gamma-globulins which have great importance in protecting the body against viruses, bacteria and either toxins. 11 Summary of Physiology 2023-2024 3. Clot formation: fibrinogen plays an important role in clot formation 4. Viscosity: Plasma proteins mainly fibrinogen give viscosity to the plasma which is important for maintenance of peripheral resistance and hence arterial B.P. 5. Carriers: plasma proteins act as carriers for: ✓ Hormones e.g. (thyroid, adrenocortical and gonadal hormones) ✓ Metal ions. ✓ Fatty acids & amino acids. ✓ Drugs. 6. Buffers: i.e. help in keeping the PH of the blood constant. ❖ If acids is added e.g. lactic acid as during muscular exercise Lactic acid + Na proteinate → Na lactate + Proteinic acid. ❖ If an alkali is added: NaOH + Proteinic acid → Na proteinate + H2O 7. CO2 carriage. 8. Capillary permeability regulation: by blocking the pores of the capillaries. 9. Diet reserve: Can be utilized during starvation. 10.ESR regulation: Fibrinogen and globulin are responsible for the roulaux formation So↑ fibrinogen and globulin ➔↑ ESR. Red blood corpuscles (RBCs) Erythrocytes Shape: circular, biconcave, non nucleated discs. Normal count:  In males ➔ (average 5.4 million / mm3).  In females ➔ (average 4.8 million / mm3). 12 Summary of Physiology 2023-2024 Functions of RBCs: 1) Functions of the content: 1. Haemoglobin:  Has a respiratory function. It transports O2 from lungs to tissues & CO2 from tissues to lungs. 2. Carbonic anhydrase:Important in CO2 carriage. 2) Functions of the wall: 1. It allows the RBCs to pass through the narrow capillaries due to its plasticity. 2. It keeps the content inside the RBCs protecting carbonic anhydrase enzyme from being lost in urine. And protect Hb from being free in plasma. If Hb is free in plasma this will lead to:  It may be precipitated in renal tubules in the form of acid haematin blocking them and produces anuria and renal failure.  Hb will be converted into bile pigments.  The viscosity of the blood will be increased ➔ ↑ the cardiac work ➔ may lead to heart failure. ORIGIN of RBCs (erythropoiesis): In infants & young children ➔ bone marrow in all bones. In adults ➔ erythropoiesis is limited to the red bone marrow (which is present in the ends of long bones, vertebrae & flat bones). LIFE SPAN OF ERYTHROCYTES: 120 days Factors affecting erythropioesis 1. Oxygen tension of arterial blood: Oxygen tension of arterial blood is the main stimulus for erythropoiesis. Lowering of oxygen tension stimulate bone marrow to produce more R.B.Cs as in high altitudes, lung disease or heart disease. It doesn’t act directly on bone marrow but through the release of Erythropiotin hormone from the kidney. 2. Kidney: 13 Summary of Physiology 2023-2024 Through release of Erythropiotin hormone that stimulates bone marrow to produce more R.B.Cs. 3. Hormones: Specific → erythropoietin. Non specific → thyroxin, testosterone. 4. Liver Produces → globin of haemoglobin, part of erythropoietin. Stores → iron &vitamin B12. 5. Bone marrow: ▪ A healthy bone marrow is essential in erythropoiesis. ▪ If bone marrow is destroy by prolonged exposure to X-rays, atomic radiations or drugs → results in aplastic anaemia. 6. Food factors : 1. Iron: Iron is the essential constituent of Hb molecule. Iron deficiency results in anaemia. Absorption of iron: Most of inorganic iron in food is in ferric state. Iron is reduced to ferrous iron in the stomach by vitamin C in the presence of HCl. Iron absorption takes place in the upper part of the duodenum. 2. Vitamin B12 : Vit. B12 is important for normal development of R.B.Cs. Deficiency of Vit. B12 results in failure of nuclear maturation and cell division in bone marrow → megalocytes appear in peripheral blood which is larger in size than normal R.B.Cs, Oval in shape, less in number, large amount of Hb, and of shorter life span.  Daily requirement 1 μg / day. Absorption: ❖ Vit B12 is called the extrinsic factor. ❖ It combines with intrinsic factor secreted by parietal cells of the stomach.to protect Vit. B12 from digestion. ❖ It is absorbed from the terminal ileum ❖ It is stored in the liver. 14 Summary of Physiology 2023-2024 3. Folic acid : Folic acid, like Vit. B12 is needed for maturation of R.B.Cs. Its deficiency leads to megaloblastic anaemia. It is absorbed from jejunum. 4. Proteins: ▪ Proteins of high biological value are needed for synthesis of haemoglobin. 5. Trace elements : ▪ Copper and cobalt act as catalyst for the synthesis of Hb but do not enter in the formation of Hb. ▪ Copper deficiency leads to anaemia. Anaemia What is the normal level of haemoglobin? Males: 16 grams/dl Females: 14 grams/dl If the haemoglobin level drops below normal, the condition is called Anaemia. Definition ofanaemia: It is decrease in the quality or quantity of RBCs. How you can diagnose anaemia laboratory? Blood count: if No. of RBCs is below 5 millions. Hb estimation: if Hb level is below 12 gm / dl. Causes of anaemia 1. Excessive destruction of RBCs (haemolysis): This is may be due to: A. Antigen-Antibody reaction as in incompatible blood transfusion. B. Bacterial toxins and malaria. C. Drugs: as sulfa. D. Enzyme deficiency: as in favism there ↓ in levels of G6PD enzyme. E. Snake venom. 15 Summary of Physiology 2023-2024 F. Blood diseases: as thalassemia, spherocytosis or sickle cell anaemia. 2. Aplastic anaemia: This is may be due to: A. Prolonged exposure to X-rays. B. Exposure to atomic radiations. C. Malignant diseases infiltrating the bone marrow. D. Drugs as chloramphanicol. 3. After haemorrhage 4. Iron deficiency anaemia: This is may be due to:Defective intake, Defective absorption or increased iron requirements. The RBCs are small in size and pale in colour. 5. Vitamin B12 deficiency ( pernicious anaemia): This is may be due to: Stomach diseases or its removal → Lack of intrinsic factor. Disease or removal of lower ileum. 6. Folic acid deficiency: This is may be due to: Increase its requirements in the pregnant women in the first 3 months of pregnancy. How to treat anaemia? 1. Treatment of the cause. 2. Iron deficiency anaemia is treated by ↑ iron supplementation. 3. Vitamin B12 deficiency is treated by Vitamin B12 injections. 4. Folic acid deficiency is treated by folic acid by mouth. 5. In megaloblastic anaemia and the cause is not well known give both Vitamin B12 by injection& folic acid orally. 16 Summary of Physiology 2023-2024 Blood groups The surface of the R.B.Cs contains many antigens (agglutinogen) the most important of these antigens are the A and B antigens. According to the presence or absence of these antigens, people are divided into 4 groups: 42%group A contain A antigen on R.B.Cs and anti-B in plasma 9%group B contain B antigen on R.B.Cs and anti-A in plasma. 3%group AB contain both A & B antigens and no anti Bodies in plasma. 46%group O contain neither A nor B antigen and both anti-A, anti- B in plasma. This is important in blood transfusion as follows: Donor A B AB O recipient Group A (Anti B) √ X X √ Group B (Anti A) X √ X √ Group AB √ √ √ √ No antibodies Group O X X X √ Anti A & anti B RH factor There is another antigen on the surface of R.B.Cs called Rh. Factor. It is determined by the presence of the D antigen. It is firstly discovered in rhesus monkey and present in 100% of these monkeys (all are RH +ve). 17 Summary of Physiology 2023-2024 In people, D antigen is found in 85% of persons and are said to be (Rh+ve). But 15% have no D antigen on their R.B.Cs and are said to be (Rh -ve). The plasma of either Rh +ve or Rh –ve persons doesn’t contain antibodies against Rh. factor naturally. Importance of Rh-factor: 1. Blood transfusion:  If Rh –ve person receives Rh +ve blood for the first time antibodies are developed in his plasma but no agglutination occur.  If second transfusion of Rh +ve blood occurs → serious agglutination and haemolysis occurs.  When Rh –ve blood is transfused to Rh –ve or Rh +ve blood no harm occur. 2. in marriage :  When an Rh-ve woman is married to an Rh +ve man, the fetus will be Rh +ve like his father.  Small amount of fetal blood may leak into the maternal circulation during delivery when the placenta is separated from the uterus so anti-D antibodies will be formed.  During the next pregnancy these antibodies cross the placenta and reach the fetus causing agglutination and haemolysis of his R.B.Cs.  The condition is called erythroblastosisfetalisand the baby is born usually dead. N.B.: If the baby is born alive he will suffer from anaemia, jaundice and may be kernictrus. Erythroblastosisfetalis can occur in the 1st pregnancy if the mother receives Rh +ve blood before pregnancy Treatment If the baby is born alive with erythroblastosisfetalis can be treated by blood exchange by a blood group O Rh –ve. Prevention Rh-ve women should marry Rh-ve men. Rh-ve women must not receive Rh +ve blood even before marriage. 18 Summary of Physiology 2023-2024 If Rh-ve woman marries Rh +ve man she must be given anti D antibodies within 72 hours after any delivery or abortion. Cross matching test: Add One drop of recipient’s plasma to one drop of donor‫יִ‬s cells and also one drop of recipient’s cells to one drop of donor‫יִ‬s plasma. No agglutination in either case should occur before blood transfusion is considered safe. Indications of blood transfusion: 1. RBCs loss: as in massive haemorrhage, haemolysis. 2. Plasma loss: as in severe burns. 3. Thrombocytopenia or deficiency in coagulation factors. 4. Severe anaemia. Precautions: 1. Similar Blood groups. 2. Cross matching test. 3. Donor must be: Suitable age. With no blood transmitted disease as HIV or hepatitis. Normal ABP. Normal Hb. 4. Blood should be fresh (for fear of hyperkalaemia) Effects of incompatible blood transfusion: 1. Severe pain in chest or loin. 2. Haemolysis 3. jaundice 4. Renal failure. 5. Heart failure. 6. Arrhythmias & flaccidity to the heart. 7. Allergy: hypotension, itching, difficulty in breathing. White blood cells (leucocytes) Shape → spherical, have nuclei and capable of amoeboid movement. 19 Summary of Physiology 2023-2024 Colour→ colourless, but may appear white due to refraction. Normal count → 4000 - 11000 / mm3. Types of leucocytes: According to the presence or absence of granules in their cytoplasm, leucocytes can be classified into: 1. Granular leucocytes (granulocytes) : Which include → Neutrophils 60 - 70% → Eosinophils 2 - 5% → Basophils 0 - 1% 2. Non granular leucocytes (agranulocytes): Which include → Lymphocytes 15-25% → Monocytes 2-8% Origin: bone marrow &lymphatic tissue. Functions of leucocytes: 1. Neutrophils : They have a defensive action against invasion of micro-organisms. They have highly phagocytic (microphages). 2. Eosinophils : Weak phagocytes. It may absorb histamine released in allergic conditions. Release plasminogen needed for lysis of blood clots. 3. Basophils : Not phagocytic They secrete histamine They secrete heparin (anticoagulant). 4. Lymphocytes : B-lymphocytes. When activated it changed into plasma cells which produce antibodies T-lymphocytes: 4 types of cells: 1) T-memory cells. 20 Summary of Physiology 2023-2024 2) T-helper cells: which activate both B & T lymphocytes. It is the cell which attacked by HIV virus causing AIDS. 3) T-suppressor cells: which suppress both B & T lymphocytes. 4) T-killer cells: which can kill: ➔ Malignant cells. ➔ Cells infected by virus. ➔ Micro-organisms. ➔ Responsible for graft rejection. 5. Monocytes : Functions: Highly phagocytic (macrophages): It can engulf large sized particles as R.B.Cs, tissue debris, malaria or large No. of bacteria. Blood platelets These are granular, non nucleated oval bodies. Formed in the bone marrow by fragmentation of giant cell called megakaryocyte. They have short life span 8-12 days. Normal platelets count is 125,000 -450,000/mm3. Function of the platelets Haemostasis : prevention of blood loss Prevention of blood coagulation in normal vascular system: a) Smoothness of the endothelium: This prevents platelet aggregation or activation of clotting factors. b) Heparin: anticoagulant. c) Lysis of blood clots by fibrinolysin (plasmin): Released from eosinophils. It causes lysis of blood clot and destruction of many clotting factors. d) Presence of the coagulation factors in an inactive form. e) Normal dynamic circulatory state. Prevention of blood coagulation (by anticoagulants): A. Outside the body (in vitro): e.g. in test tube we can use: 21 Summary of Physiology 2023-2024 Na citrate → bind to Ca++ in an unionized form (so it is used in blood banks). Na oxalate → form insoluble salts with Ca++ → its precipitation. Notice that Ca+2 is one of the coagulation factors Collecting blood in containers with a very smooth surface e.g. silicon coated. → This prevents platelet aggregation or activation of clotting factors. Addition of heparin. Cooling the blood sample into zeroᵒ C → inhibit formation of thromboplastin. B. Inside the body (in vivo):By Heparin (by injection). Dicumarol (orally). Heparin Dicumarol Origin Extracted from animal Of plant origin tissues Mechanism of action Prevent activation of Competitive inhibitor some coagulation of Vitamin K factors Site of action In vivo & in vitro In vivo only Onset of action Rapid delayed (after 1-2 days) Duration Short prolonged Administration Intravenous or orally subcutaneous Antidote Protamine sulphate Vitamin K Bleeding time It is the time passed from the skin injury to the stoppage of bleeding. Steps: 1. Small injury to the skin by a sterilized pin. 22 Summary of Physiology 2023-2024 2. The blood is removed by filter paper at intervals to prevent clot formation 3. The time passed from the skin injury to the stoppage of bleeding is recorded. normal bleeding time: 2-6 minutes. Prolonged: in platelet disorders. Coagulation time It is the time passed from start of bleeding to formation of fibrin threads. Steps: 1. Blood is withdrawn into a capillary tube. 2. Sections of the tube are broken at intervals (every 0.5 minute). 3. The coagulation point is known when fibrin threads are seen between the edges of the broken sections. Normal Coagulation time: 3-8 minutes. Prolonged Coagulation time occur in: 1. Haemophilia A→ deficiency of factor VIII Haemophilia B→ deficiency of factor IX Haemophilia C→ deficiency of factor XI Hemophilia is a recessive X-linked disorder, is more likely to occur in males than females. 2. Vitamin K deficiency: Vitamin K is needed by the liver for synthesis of some coagulation factors It is Due to: Liver disease (failure of the liver to secrete bile salts) Obstructive jaundice. 23 Summary of Physiology 2023-2024 Respiratory system Respiration: is a process that provides oxygen to tissues and remove carbon dioxide. This is achieved through the following 4 events: 1. Pulmonary ventilation: this is the inflow & outflow of air between atmosphere & lung alveoli. 2. Diffusion: of O2& CO2between blood & alveoli (external respiration). 3. Transport: of O2& CO2 in blood to & from cells (internal respiration). 4. Regulation of respiration. Anatomy: Respiratory system consists of: 1) Air passages: nose, pharynx, larynx, trachea, bronchi, bronchioles, terminal bronchioles (conducting airways) then, respiratory bronchioles, alveolar ducts, alveolar sacs & alveoli (where gas exchange occurs). 2) Lungs. 3) Respiratory muscles:diaphragm, intercostals muscles & accessory muscles. 4) Respiratory center: and nerve supply to respiratory muscles. 24 Summary of Physiology 2023-2024 Functions of the respiratory system A. Gas exchange. B. Lung defense mechanisms: a) Filtration &cleaning: By the hairs of the nostrils which strain out particles larger than 10 μm in diameter. Cough reflex for particles 2-10 μm in diameter which fall on bronchial mucosa. b) Air conditioning: The respiratory passages humidify and cool or warm the inspired air due to its richness in capillaries. c) Bronchial mucosa secretes secretory antibodies (IgA) that help in resistance of infection. d) Pulmonary alveolar macrophages which phagocytose foreign particles those reach the alveoli. C. Regulation of blood PH. D. Regulation of water balance by excretion of water vapor. E. Supply air to the larynx for voice production. F. Smell. G. Regulation of body temperature in panting animals. Mechanism of respiration: Respiratory rate: 12-16 cycles / minute. Respiratory cycle: inspiration – expiration – expiratory pause. Inspiration: Is an active process. There is contraction of the diaphragm &external intercostals muscles → ↑ anteroposterior, transverse & vertical diameters of the thorax → ↓intrathoracic pressure → air flow into the lungs. Diaphragm is responsible for 75% of respiration. It is supplied by the phrenic nerves arising from C 3,4, 5. Expiration: Is a passive process. There is relaxation of the respiratory muscles → ↑ intrathoracic pressure → outflow of air from the lungs. 25 Summary of Physiology 2023-2024 Surfactant It is a phospholipid-protein complex secreted by type II alveolar epithelium and Present inside the lung alveoli. Functions: 1. Decrease the surface tension of the fluid lining alveoli 2. Decreases muscular effort needed to ventilate the lungs. 3. It prevents collapse of small alveoli Respiratory distress syndrome: In the absence of surfactant, lung expansion is very difficult. It occurs in some new born prematurebabies who do not secrete adequate quantities of surfactant which makes lung expansion difficult. Some of these die after birth because of in adequate respiration. Dyspnea Definition:difficulty in breath. Causes: 1- Lung diseases. 2- Bronchial asthma. 3- Heart disease. 4- Increase metabolic rate as in hyperthyroidism & fever. 5- Chest wall deformities. 6- Weak respiratory muscles. 7- Acidosis of the blood as in diabetes mellitus. 8- O2 lack. Control of respiration This includes: I. Chemical control of respiration. II. Non chemical control. 26 Summary of Physiology 2023-2024 Chemical control of respiration: This depends on the level of CO2, O2 and H+ in the blood. ↑ CO2 or H+ stimulates respiration. ↓ O2  stimulates respiration. Non chemical control of respiration (nervous regulation): A. Afferent impulses From the lungs: Inflation of the lung → inhibits the respiratory center → expiration. Deflation of the lung → stimulates the respiratory center → inspiration. B. Afferents from upper respiratory passages: Irritation of nasal mucosa  Sneezing reflex. Irritation of tracheal or bronchial or laryngeal mucosa  Cough reflex C. Afferent impulses from the circulatory system : a) from baroreceptors: ↑ ABP  inhibits the respiratory center  inhibition of respiration and may produce apnea (temporary stoppage of breathing) ✓ This may occur after injection of adrenaline (adrenaline apnea). But with haemorrhage  ↓ ABP ↑ respiratory rate. b) From chemoreceptors: (chemical regulation). ↑ CO2 ,↓ O2 or ↑ H+ stimulate chemoreceptors  send excitatory impulses to RC  ↑ respiratory rate. c) From the right atrium (Harrison’s reflex): Distension of right atrium →stimulate the RC → ↑ respiratory rate. D.Afferents from higher centers: a) Cerebral cortex : ✓ voluntary apnea ✓ Voluntary hyperventilation ✓ Controlled expiratory effort with singing or talking. b) Hypothalamus : 27 Summary of Physiology 2023-2024 ✓ Moderate pain ,↑ temperature , moderate emotions  ↑ respiratory rate ✓ Stimulation of anterior hypothalamus  ↓ respiratory rate. ✓ Stimulation of posterior hypothalamus  ↑ respiratory rate. E. Afferents from other parts of the body : a) Skin: ✓ Cold receptors: its stimulation  apnea followed by deep inspiration. ✓ Pain receptors : mild , moderate pain  ↑ respiratory rate ✓ Sever pain ↓ RR or apnea. b) Swallowing: inhibits respiration Hypoxia Definition:It is oxygen deficiency at the tissues. Types: 1) Hypoxic hypoxia. 2) Anaemic hypoxia. 3) Stagnant hypoxia. 4) Histotoxic hypoxia. i. Hypoxic hypoxia Causes: 1) Decrease oxygen in atmosphere as in High altitudes or closed places. 2) Lung diseases: 3) Depression of respiratory center: as in morphine poisoning. 4) Shunting of venous blood into arterial blood: as in Fallotʼstetrology. ii. Anaemic hypoxia: Causes: 1. All types of anaemia 2. Lack of functioning Hb as in Carbon monoxide poisoning. iii. Stagnant hypoxia: Causes: 28 Summary of Physiology 2023-2024 Generalized stagnant hypoxia: as in right sided heart failure or polycythaemia. Localized stagnant hypoxia: as in thrombosis of artery, pressure on it or DVT. iv. Histotoxic hypoxia: Causes: Cyanide poisoning→ block cytochrome oxidase so cytochrome remains in the reduced form. Alcohol poisoning→ block cytochrome dehydrogenase so cytochrome remains in the oxidized form. Cyanosis Definition: it is blue discoloration of the skin and mucous membranes due to excessive amounts of deoxygenated haemoglobin in skin vessels. Threshold of cyanosis: Definite cyanosis appears whenever the arterial blood contains more than 5 grams deoxygenated haemoglobin in 100 ml blood. Causes of cyanosis: 1. All causes of hypoxic hypoxia. 2. All causes of stagnant hypoxia. 3. Moderate cold in exposed areas even in normal individuals. Types of cyanosis: 1. Central cyanosis: In cardiac, respiratory or haematological problems causing cyanosis. There is cyanosis all over the body including extremities but known by cyanosis of the tongue. 2. peripheral cyanosis: In cold weather or localized causes of cyanosis. There is cyanosis of finger tips, lips, ear lobule or the affected limb but there is no cyanosis of the tongue. 29 Summary of Physiology 2023-2024 Digestion The digestive system consists of:  The gastro-intestinal tract (GIT): This includes the mouth, pharynx, oesophagus, stomach, small intestine (duodenum, jejunum&ileum), large intestine, rectum & anal canal.  Accessory glands (salivary glands, pancreas, liver & biliary system). Functions of the GIT: 1. Secretion of digestive juices needed for digestion. 2. Digestion of food to be easily absorbed. 3. Motility: to propagate food to the sites of absorption or excretion. 4. Absorption of digested food or simple substances as vitamins. 5. Excretion of undigested or nonabsorbed substances in stool. The aim is to provide the body with continual supply of water, electrolytes & nutrients 30 Summary of Physiology 2023-2024 Salivary secretion Saliva is secreted by 3 pairs of salivary glands: parotid, sublingual & submandibular salivary glands. Functions of saliva 1. Facilitation of Deglutition:  By Lubrication and moistening the food and buccal cavity that help the process of chewing and swallowing. 2. Facilitation of Articulation:  Moistening of the buccal cavity including the soft palate, tongue and lips is essential for speech. 3. Digestion:  Salivary amylase can hydrolyze the cooked starch into maltose in the presence of chloride ions. 4. Antibacterial & cleaning: By → ✓ The flow of saliva itself helps wash away the pathogenic bacteria as well as the food particles that provide their metabolic support. ✓ The presence of several factors that attack and digest bacteria as lysozyme. ✓ Saliva contains antibodies that can destroy oral bacteria. 5. Regulation of water balance:  Decrease body water content → decreased salivary secretion → dryness of the mouth and pharynx → thirst sensation. 6. Buffering action:  The bicarbonate and phosphates protect the mouth from acids or alkalis that may be introduces into it.  Mucin also has a buffering action.  This prevents loss of Calcium from teeth in acidity and help to neutralize gastric HCl relieving the heartburn in regurgitation. 7. Excretion:  Some drugs as mercury, iodides, and lead are partly excreted in saliva. In chronic lead poisoning a blue line develops at the margins of the teeth and gums. 8. Dilution:  Saliva dilutes the irritating substances and excessively hot or cold substances. 31 Summary of Physiology 2023-2024 9. Solvent:  Saliva dissolves some foods to stimulate the taste buds of the tongue that initiate taste sensation. 10.Regulation of body temperature:  In animals with no sweat glands as dogs. The evaporation of saliva during panting increases heat loss in hot weather. Gastric secretion Gastric juice:  Clear colourless fluid.  Its PH is 0.9 – 1.5 (the most acidic fluid in the body)  Volume: about 3 L / day.  Composition: ✓ 99% → water. ✓ 0.5% → HCl. ✓ 0.5% → solids: organic & inorganic. Organic: as pepsin, rennin, lysozyme, lipase, intrinsic factor &mucin. Inorganic: as Na+, Cl-& K+, PO43-, Ca2+& HCO3-. Functions of gastric HCl: a) It transforms the inactive pepsinogen into active pepsin. b) It provides the optimum PH for the action of pepsin (PH 1.5-2.0). c) Has an antibacterial function. d) Help absorption of calcium (by preventing its precipitation) and iron (by converting ferric iron into ferrous). e) Help milk clotting. f) When HCl becomes in contact with duodenum it stimulates: - Release of secretin hormone. - Enterogastric reflex that controls evacuation of the stomach. Digestive enzymes and other organic constituents: 1. Pepsin:  Proteolytic enzyme (endopeptidase) secreted in an inactive form (pepsinogen) from peptic cells.  Activated by HCl to pepsin. 32 Summary of Physiology 2023-2024  Its optimum PH is 1.5 - 2.  It hydrolyzes the proteins into proteoses, peptones & polypeptides. 2. Rennin:  Milk clotting enzyme.  Not present in human but found in gastric juice of young animals.  Its function in human is performed by pepsin. Importance of milk clotting: It prevents rapid evacuation of the milk from the stomach. This allows sufficient time for gastric digestion & the antibacterial action of HCl to take effect. 3. Intrinsic factor:  glycoprotien secreted from parietal cells.  Required for absorption of vitamin B12. 4. Lysozyme: has antibacterial action. 5. Mucin:  Secreted by mucous cells of gastric glands in the fundus and pylorus which protects the wall of the gut from HCl or mechanical irritation. How the stomach protects itself against gastric juice?  The presence of thick layers of mucous.  The digestive enzymes are secreted in an inactive form & activated only in the lumen of the stomach. Vomiting 1- Mechanical irritation of the posterior part of the tongue or the throat by finger or tongue depressor. 2- Chemical irritation of the stomach. 3- Rotation or acceleration of the head Such as occurs in motion sickness. 4- Intense pain as renal or biliary colic or myocardial infarction. 33 Summary of Physiology 2023-2024 5- Psychogenic vomiting (conditioned reflex) induced by emotional factors including those accompanying nauseating sights & odors & anxiety before taking an examination. 6- By stimulation of vomiting center in the brain by: 1- Drugs & chemical agents: anaethetics, emetics, cancer chemotherapy, tartar emetate, apomorphine. 2- Anoxia of vomiting center as in High altitudes. 3- Increased intracranialtension as in brain tumors. 4- Head injuries. 5- Acidosis. Effects of vomiting: 1. Dehydration. 2. Alkalosis. 3. Loss of electrolytes especially K+. Pancreatic secretion Pancreatic juice:  Clear colourless isotonic fluid.  Its PH is 8.5 (the most alkaline fluid in the body) Aim of its alkalinity:  To provide an optimum PH for pancreatic enzymes.  To neutralize the acidity of acid chyme emptied by stomach to protect the duodenal mucosa.  Volume: about 1.5 L / day.  Composition: ✓ 98.5% → water. ✓ 1% →Inorganic: mainly HCO3– responsible for its alkalinity. ✓ 0.5% →Organic: as trypsin, chymotrypsin, carboxypeptidase, lipase and amylase. Functions of Digestive enzymes: a) trypsin:  Proteolytic enzyme (endopeptidase) secreted in an inactive form (trypsinogen). 34 Summary of Physiology 2023-2024  Activated by enterokinase enzyme (secreted by duodenal mucosa) in the presence of Ca+2 to trypsin. Then the active trypsin activates the rest of trypsinogen (autoactivation)  It hydrolyzes the proteins into proteoses, peptones & polypeptides (as pepsin). b) Pancreatic lipase:  It is the most powerful lipolytic enzyme.  It hydrolyzes the fat into glycerol & fatty acids in the presence of bile salts which accelerates the reaction.  Absence of this enzyme → passage of much undigested fat in faeces. This condition is called steatorrohea. c) Pancreatic amylase:  Its action is similar to salivary amylase but it is more powerful.  It can hydrolyze both cooked & uncooked starch into maltose in the presence of chloride ions. Effect of loss of pancreatic juice: 1. Incomplete digestion→ malnutrition. 2. Acidosis: due to loss of NaHCO3. 3. Dehydration: due to loss of water and electrolytes. Bile secretion  Bile is continuously formed by theliver. Bile is both secretion & excretion:  Secretion: of the bile salts which is important for lipid digestion and absorption.  Excretion: of bile pigments which are the end products of Hb breakdown. 35 Summary of Physiology 2023-2024 Functions of the gall bladder: 1- Storage of bile:  Bile is continuously secreted by the liver cells and transported through the biliary system to the gall bladder to be stored until needed. 2- Concentration of bile:  The total secretion of bile is 1000 ml/ day.  The max. Volume of gall bladder is 70 ml.  During storage of bile, water, Cl-, Na+, HCO3- are absorbed by the gall bladder mucosa while bile salts, bile pigments & cholesterol are concentrated up to 10 times. 3- Acidification of liver bile:  The absorption of NaHCO3 by the gall bladder causes the PH of liver bile (PH 8 - 8.6) to be less alkaline (PH 7). This prevents precipitation of Calcium and calcium stones formation. 4- Equalization of pressure:  This allows the liver to secrete bile continuously as the liver can’t secrete bile against high pressure. 5- Secretion of mucous:  The gall bladder secretes a large quantity of mucous helps to protect the gall bladder mucosa & ducts from highly concentrated bile. 6- Evacuation of bile in duodenum:  When the food reach the duodenum by contraction of its wall and relaxation of the sphincter of oddi. Functions of bile salts: 1- Digestion:  Bile contains no digestive enzymes but bile salts help fat digestion by: Act as activator of pancreatic lipase. Decrease the surface tension of fat globules and breaks them into fine particles (emulsification of fat). This help in exposing a larger surface area for the action of lipase enzyme. 36 Summary of Physiology 2023-2024 2- Absorption:  Bile salts are important for absorption of: - Fatty acids. - Fat soluble vitamins D, E & K. - Help the absorption of iron and calcium. 3- Choleretic:  Bile salts are the best stimulant of bile secretion by the liver. 4- Solvent:  It converts water insoluble cholesterol to water soluble.  This prevents precipitation in the gall bladder and formation of gall stones. 5- Stimulant of peristalsis:  Bile salts stimulate the movement of small and large intestine and prevent constipation. 6- anti-putrefactive:  The effect is secondary to stimulation on fat absorption.  In the absence of bile salts, the unabsorbed fat forms a layer around the protein particles that prevent their digestion and absorption.  The unabsorbed protein acts as a good medium for growth of bacteria in the colon. Other functions of bile: Neutralization of HCl:  Bile is an important source of alkali for neutralization of gastric HCl. Excretion:  Bile is a route for excretion of certain drugs, toxins, copper, iron & calcium. Lubrication:  By its mucin content 37 Summary of Physiology 2023-2024 Jaundice (icterus) Definition:  Yellowish discoloration of the skin and mucous membranes due to hyperbilirubinaemia.  Usually seen in the sclera. Normal level of total bilirubin= 0.5 mg / dl.  Jaundice appears when bilirubin level reaches 1.5 mg / dl. Types of jaundice:  Haemolytic jaundice.  Obstructive jaundice.  Hepatocellullar jaundice. Causes of haemolytic jaundice: Haemolysis of RBCs. Physiological jaundice of newborn. The patient color is pale yellow with normal urine color and dark stool color. Causes of obstructive jaundice: Stone in thecommon bile duct. Cancer head of pancreas The patient color is very dark yellow with dark urine color (tea like) and pale stool color. Causes of hepatocellular jaundice: Liver diseases as hepatitis or cirrhosis. The patient color is dark yellow with dark urine color and pale stool color. 38 Summary of Physiology 2023-2024 Liver It is the largest gland in the body. Functions: 1. Carbohydrate, protein & fat metabolism. 2. Blood reservoir. 3. Immunity: through Kupffer cells. 4. Removal of ammonia and convert it into urea. 5. Detoxification of drugs and toxins. 6. Formation of : Plasma proteins - bile salts - blood cells especially in the fetus. 7. Excretion and removal of: Bilirubin - drugs – hormones. 8. Storage of : Glycogen - vitamins A, D & B12. Small intestine Functions of the small intestine: 1. Digestion: complete digestion of food occurs mainly in its upper half. 2. Absorption: of digestive products occurs mainly in its lower half. 3. Secretionof hormones: concerned with regulation of GIT secretions and motility. 4. Mixing & propagation of food towards the colon. Digestive enzymes: include → 1- Erypsin: this is a mixture of enzymes that hydrolyze polypeptides. It includes: a- Dipeptidase: splits dipeptides into free amino acids. b- Aminopolypeptidase: splits polypeptides separating amino acids with free amino group. c- Carboxypeptidase: splits polypeptides separating amino acids with free carboxyl group. 39 Summary of Physiology 2023-2024 2- Disaccharidases: which hydrolyze disaccharides and include: a- Maltase: splits maltose into 2 molecules of glucose. b- Sucrase: splits sucrose into glucose and fructose. c- Lactase: splits lactose into glucose and galactose. Absorption in the small intestine: Absorption: is the transfer of digested products of food from the intestinal lumen to the blood or lymphatics. Small intestine is main site of absorption due to: ✓ Its wide surface area provided by: o The presence of villi and microvilli. o Its length. ✓ Its rich blood & lymphatic flow. Large intestine Functions of large intestine: 1) Absorption:  Of water and electrolytes and may be glucose when present.  This is important in rectal feeding as in unconsciousness or severe vomiting. 2) Secretion:  Mainly mucin for: ✓ Neutralization of acids produced by bacterial fermentation. ✓ Protect the mucosa from mechanical injury. 3) Bacterial action:  Synthesize vitamin K.  Cellulose digestion in animals by beta-amylase enzyme formed by bacteria. 4) Storage of faeces:  Till the time of defecation. 5) Defecation. 40 Summary of Physiology 2023-2024 Kidney Renal system includes: 1- A pair of kidneys 2- Two ureters 3- Urinary bladder 4- Urethra. Functions of the kidney: 1- Excretion of Waste Products; Urea, uric acid, creatinine, bilirubin, harmful foreign chemical substances such as toxins, drugs, heavy metals, pesticides, etc. 2- Maintenance of Water Balance 3- Maintenance of Electrolyte Balance 4- Maintenance of pH 5- Hemopoietic function: Kidneys stimulate the production of erythrocytes by secreting erythropoietin. 6- Endocrine function Kidneys secrete many hormonal substances: i. Erythropoietin i. Thrombopoietin ii. Renin iv. 1,25-dihydroxycholecalciferol (calcitriol) v. Prostaglandins. 7- Regulation of blood pressure 8- Regulation of blood calcium level Structure of the kidney: Each kidney composed of about 1 million nephrons which represent the structural and the functional unit of the kidney. The nephron is composed of: A. Tuft of capillaries invaginating the dilated blind end of Bowman‫׳‬s capsule forming the glomerulus. B. Renal tubule which have the following parts: a) Proximal convoluted tubule. b) Loop of Henle. c) Distal convoluted tubule. d) Collecting tubules. 41 Summary of Physiology 2023-2024 Urine formation Urine formation is a blood cleansing function. Normally, about 1,300 mL of blood (26% of cardiac output) enters the kidneys. Kidneys excrete the unwanted substances along with water from the blood as urine. Normal urinary output is 1 L/day to 1.5 L/day. Processes of Urine Formation The urine formation includes three processes: I- Glomerular filtration II- Tubular reabsorption III- Tubular secretion. Among these three processes filtration is the function of the glomerulus. Reabsorption and secretion are the functions of tubular portion of the nephron. I- Glomerular Filtration: Glomerular filtration is the process by which the blood is filtered while passing through the glomerular capillaries by filtration membrane. It is the first process of urine formation. Filtration membrane is formed by three layers: 1. Glomerular capillary membrane 2. Basement membrane 3. Visceral layer of Bowman capsule. When blood passes through glomerular capillaries, the plasma is filtered into the Bowman capsule. All the substances of plasma are filtered except the plasma proteins. The filtered fluid is called glomerular filtrate. Normal GFR is 125 mL/minute or about 180 L/day. Forces determining filtration: 1- Filtrating (Favoring) forces: A- Glomerular Capillary Pressure: it is the pressure exerted by the blood in glomerular capillaries. It is about 60 mmHg and, varies between 45 and 70 mm Hg. Glomerular capillary pressure is the highest capillary pressure in the body. 2- Reabsorping (Opposing) forces: 42 Summary of Physiology 2023-2024 A- Colloidal Osmotic Pressure It is the pressure exerted by plasma proteins in the glomeruli which is about 32 mm Hg. B- Hydrostatic Pressure in Bowman Capsule It is the pressure exerted by the filtrate in Bowman capsule. It is also called capsular pressure. It is about 18 mm Hg. Net Filtration Pressure (Starling forces): Filtrating forces – Reabsorping forces = 60 – (32 + 18) = 10 mmHg II- Tubular reabsorption Tubular reabsorption is the process by which water and other substances are selectively transported from renal tubules back to the blood. Essential substances such as glucose, amino acids and vitamins are completely reabsorbed from renal tubule. Whereas the unwanted substances like metabolic waste products are not reabsorbed and excreted through urine. Site of reabsorption Reabsorption of the substances occurs in almost all the segments of tubular portion of nephron. 1- Substances Reabsorbed from Proximal Convoluted Tubule About 7/8 of the filtrate (about 88%) is reabsorbed in proximal convoluted tubule. The brush border of epithelial cells in proximal convoluted tubule increases the surface area and facilitates the reabsorption. Substances reabsorbed from proximal convoluted tubule are glucose, amino acids, sodium, potassium, calcium, bicarbonates, chlorides, phosphates, urea, uric acid and water. 2- Substances Reabsorbed from Loop of Henle Substances reabsorbed from loop of Henle are sodium and chloride. 3- Substances Reabsorbed from Distal Convoluted Tubule Sodium, calcium, bicarbonate and water are reabsorbed from distal convoluted tubule. III Tubular secretion 43 Summary of Physiology 2023-2024 Tubular secretion is the process by which the substances are transported from blood (peritubular capillaries) into renal tubules, eg. Potassium, ammonia, hydrogen and urea. 44 Summary of Physiology 2023-2024 The nervous system The nervous system is divided into: A. Central nervous system. B. Peripheral nervous system. 1. The central nervous system: Responsible for control & communication all over the body. It is connected to the other systems through the peripheral nervous system (nerves). It is formed of: 1) Brain: which includes: ✓ The 2 cerebral hemispheres. ✓ The cerebellum. ✓ The brain stem: midbrain, Pons & medulla. 2) Spinal cord. 2. The peripheral nervous system: Formed by the nerves which can be classified into: ✓ 12 pairs of cranial nerves arise from the brain stem except for the olfactory & optic nerves which reach the cerebral hemispheres directly. ✓ 31 pairs of spinal nerves (8 cervical, 12 thoracic, 5 lumbar, 5 sacral & one coccygeal). The structural unit of the nervous system is the nerve cell which if formed of a cell body, axon & dendrites. 45 Summary of Physiology 2023-2024 Functions of Spinal cord: Pathway for impulses from the periphery to the brain and in the opposite direction. Responsible for the following automatic reflexes: ✓ Protective withdrawal reflex. ✓ Walking movement. ✓ Stretch reflex. ✓ Micturition, defecation & erection reflexes. Functions of brain stem: Control the arterial blood pressure and respiratory movements, swallowing, coughing, vomiting….…etc. by centers in medulla oblongata and Pons. Functions of cerebellum: Coordination of voluntary movements. Maintain equilibrium. Functions of cerebral hemispheres: Memory storage. Contain motor centers. Essential for most of thought processes & learning. Contain sensory centers. Contain centers of vision, hearing and smell. The activities of the body are under control of: 1- Somatic (Voluntary) nervous system: to skeletal muscles. 2- Autonomic (Involuntary) nervous system: to cardiac muscle, smooth muscles & glands. The autonomic nervous system is subdivided into: 1- Sympathetic nervous system: In general, symoathetic nerves are excitatory to cardiac muscle but inhibitory to smooth muscles & glands. i.e. sympathetic stimulation to any smooth muscle leads to its relaxation (With some exceptions).Whereas Sympathetic stimulation to any gland leads to decrease its secretions (With some exceptions). 46 Summary of Physiology 2023-2024 2- parasympathetic nervous system: In general, parasympathetic nerves are inhibitory to cardiac muscle but excitatory to smooth muscles & glands.i.e. Parasympathetic stimulation to any smooth muscle leads to its contraction (With some exceptions) whereas Parasympathetic stimulation to any gland increases its secretions. Sympathetic nervous system originates from LHC of all thoracic segments & the upper 4 lumber segments (Thoraco-lumber). Parasympathetic nervous system originates from cranial nerve nuclei of 3rd (Oculomotor), 7th (facial), 9th (glossopharyngeal), 10th (vagus) & from LHC of 2, 3, 4 sacral segments (Cranio-sacral). I. Functions of the sympathetic On the head & neck: 1) Eye:  Dilatation of the eye pupil.  Elevation of upper eye lid.  False Exophthalmos. 2) Skin:  Hair erection.  Sweating.  Vasoconstriction. 3) Salivary glands: Little secretion Poor in water & electrolytes but rich in enzymes. 4) Functions of the sympathetic On thoracic viscera: 1) heart:  Stimulate all properties of cardiac muscle.  Increase coronary blood flow. 2) Respiratory system:  Bronchodilatation.  Pulmonary vasoconstriction. 5) Functions of the sympathetic On abdominal viscera:  GIT: relaxation of the smooth muscles of the wall of the stomach & small intestine but motor to the sphincters. 47 Summary of Physiology 2023-2024  Blood vessels: vasoconstriction.  Liver: glycogenolysis.  Spleen: contraction of the smooth muscles of the capsule of the spleen → pouring its stored blood in the circulation.  Adrenal medulla: secretory to adrenal medulla → adrenaline secretion. 6) Functions of the sympathetic On pelvic viscera:  Urinary bladder: relaxation of the smooth muscles of the wall of the bladder but motor to the internal urethral sphincter.  Rectum: relaxation of the smooth muscles of the wall of the rectum but motor to the internal anal sphincter. →Retention of urine & stool.  Blood vessels: vasoconstriction.  Male genital organs: ejaculation of semen. II. Functions of parasympathetic nerves: 1. Oculomotor nerve: 1) Motor to the sphincter pupillae muscle →miosis. 2) Motor to the ciliary muscle → accommodation of vision. 2. Facial nerve: 1) Secretory and vasodilator to the sublingual & submandibular salivary glands → secretion which is large in volume, rich in water & electrolytes but poor in enzymes. 2) Secretory and vasodilator to the lacrimal gland. 3) Vasodilator to blood vessels of the anterior 2/3 of the tongue. 3. Glossopharyngeal nerve: 1) Secretory and vasodilator to the parotid glands → secretion which is large in volume, rich in water & electrolytes but poor in enzymes. 2) Vasodilator to blood vessels of the posterior 1/3 of the tongue. 4. Vagus nerve: 1) heart:  Inhibit all properties of cardiac muscle.  Decrease coronary blood flow. 2) Respiratory system:  Bronchoconstriction.  Increased bronchial secretion. 48 Summary of Physiology 2023-2024  Pulmonary vasodilatation. 3) GIT:  Motor to the smooth muscles of the wall of the stomach & small intestine, proximal ½ of large intestine & gall bladder but inhibit the sphincters.  Secretory to the glands of the stomach, pancreas & liver. 5. Pelvic nerve:  Urinary bladder: contraction of the smooth muscles of the wall of the bladder but inhibits the internal urethral sphincter →urination.  Rectum: contraction of the smooth muscles of the wall of the rectum but inhibits the internal anal sphincter →Defecation.  Blood vessels: vasodilatation.  Penis & clitoris: vasodilatation →erection.  Male genital organs: secretory to the prostate & seminal vesicles. 49 Summary of Physiology 2023-2024 Circulatory system The circulatory system consists of the heart and blood vessels. The Heart It is a muscle about the size of your fist. The heart is located in the center of your chest slightly to the left. Its job is to pump your blood and keep the blood moving throughout your body. The Blood Vessels There are three types of blood vessels: Arteries Capillaries Veins Arteries Arteries are blood vessels that transport blood AWAY from the heart to the tissues. Capillaries Capillaries are tiny blood vessels thin or thinner than the hairs on your head. Capillaries connect arteries to veins. Food substances (nutrients), oxygen and wastes pass in and out of your blood through the capillary walls to the tissues. Veins Veins are blood vessels that carry blood back toward heart from tissues. Physiological anatomy of the heart The heart is composed of, 4 chambers: 2 atria & 2 ventricles. 4 valves (Tricuspid, Bicuspid , Pulmonary and Aortic) The upper two chambers of the heart are called atria (Right Atrium and Left Atrium). They have thin walls and function to receive blood returning to the heart from the lungs and the body during ventricular contraction (systole) then it pumps blood to ventricle during ventricular relaxation (diastole). The bottom chambers of the heart are called ventricles. (Right Ventricle and Left ventricle) They function to pump blood into the arteries. 50 Summary of Physiology 2023-2024 The four valves of the heart, Function, keep blood flowing in one direction and include; The atrioventricular (AV) valves; tricuspid and bicuspid. o They allow blood to pass in one direction from atria to ventricles. The Semilunar valves, pulmonary, and aortic valves. o They allow blood to pass in one direction from ventricles to aorta or pulmonary artery. Tricuspid valve (right AV valve): between the right atrium and the right ventricle. It has 3 cusps. Bicupid Valve (Mitral valve) (Left AV valve): between the left atrium and the left ventricle. It has 2 cusps. Aortic valve: between the aorta and the left ventricle. Pulmonary valve: between the pulmonary artery and the right ventricle Blood Flow Through the body Blood circulation inside body is divided into; Pulmonary Circulation, Pulmonary circulation starts from right ventricle and ends in left atrium. General circulation, Systemic circulation starts from left ventricle and ends in right atrium. 1. Blood that is low in oxygen and rich in carbon dioxide enters the right atrium of the heart through large veins called the inferior and superior vena cavae. 2. When Rt. Atrium contract, the blood pass through opened tricuspid valve into the right ventricle. 3. When the right ventricle contracts, the blood pass through opened Pulmonary valve into a larger artery called the pulmonary trunk. 4. The pulmonary trunk branches into pulmonary arteries, which carry blood to the lungs. In the lungs, blood picks up oxygen and gets rid of carbon dioxide. 5. Blood rich in oxygen and low in carbon dioxide then returns to the heart through four veins called the pulmonary veins. The pulmonary veins empty the blood into the left atrium. 6. From the left atrium, , the blood pass through opened Mitral valve into Left ventricle 7. When the left ventricle contracts, blood is pushed over the aortic valve into the aorta. 8. The aorta distributes blood bbbbbbbbbbbbbbbbe3buiwqd6into its branches and throughout the body. 51 Summary of Physiology 2023-2024 9. In the body, the blood gives oxygen to cells and picks up carbon dioxide. 10.Veins of the body pick up the oxygen poor blood and empty it into the vena fe, and the whole circuit starts all over again. 52 Summary of Physiology 2023-2024 Heart rate Normal heart rate is between: 60 – 90 beats / minute Increase heart rate above 90 beats / minute is called tachycardia. Decrease heart rate below 60 beats / minute is called bradycardia. Physiological factors affecting heart rate: 1) Age:  Heart rate in newly born infant = 160 beats / minute.  Then it gradually decrease with age till the adult age reaching about 72 beats / minute then remains constant. 2) Sex:  Heart rate is more in females than in males due to the high vagal tone in males. 3) Sleep:  The heart rate decreases in deep quit sleep but increases during nightmares. 4) Physical training:  The heart rate in athletics is less than non-athletics due to high vagal tone. 5) Circadian rhythm:  At the morning the heart rate is less than in the evening. 6) Body posture:  The heart rate increases by about 25% during standing or sitting from a recumbent position. Arterial Blood Pressure ABP Definition: It is the lateral pressure exerted by the blood column on the arterial wall. A. Systolic blood pressure: It is the maximal pressure reached in arteries during systole. It equals 90-140 mmHg, average 120 mmHg. 53 Summary of Physiology 2023-2024 B. Diastolic blood pressure: It is the minimal pressure reached in arteries during the cardiac cycle. It equals 60-90 mmHg, average 80 mmHg. Physiological variations in ABP: 1) Age:  ABP in newly born infant = 50/30 mmHg.  Then it gradually increase with age till the adult age reaching about 120/80 mmHg then remains constant.  In old age increases to 170 / 90 mmHg. 2) Sex:  In children the blood pressure is identical in both sexes.  In adult age, the ABP is lower in females than in males by 5 mmHg due to the relaxing effect of female sex hormones specially progesterone on blood vessels.  During menopause, the ABP is higher in females than in males by 5 mmHg. 3) Sleep:  The ABP decreases in deep quit sleep but increases during nightmares. 4) Body built:  The ABP is higher in obese than in thin individuals by 5-10 mmHg. 5) Circadian rhythm:  At the morning (4 a.m.) the ABP is the lowest. But at afternoon (4p.m.) is the highest. 6) Body posture:  The ABP increases by about 0.77 mmHg every 1 cm below the level of the heart in standing position. It is the weight of the blood column.  Above the heart the reverse occurs.  In recumbent position, no difference in ABP above or below the heart. 7) After meals:  The ABP increase by about 5-10 mmHg after heavy meals due to vasoconstriction in systemic blood vessels except that of the abdominal viscera. Also venoconstriction→ VR → COP. 8) Muscular exercise:  The ABP increases up to 180 mmHg due to ↑ VR &↑ COP. 54 Summary of Physiology 2023-2024 9) Emotions:  Mild or moderate emotions ↑ ABP.  Severe or sudden emotions ↓ ABP. Heart Sounds 2 sounds are heard normally by the stethoscope.  1st heart sound: caused by sudden closure of A-V valves.  2nd heart sound: caused by sudden closure of semilunar valves. Aucultatory areas: These heart sounds can be best auscultated at certain areas on the chest. The first heart sound can be auscultated at: ✓ Mitral area: left 5thintercostals space midclavicular line. ✓ Tricuspid area: at the lower end of the sternum. The second heart sound can be auscultated at: ✓ Aortic area: right 2nd intercostal space near the sternum. ✓ Pulmonary area: left 2nd intercostal space near the sternum. Edema Definition: presence of excess fluid in interstitial space. Causes: 1- Increased capillary hydrostatic pressure: This may occur as a result of: Venous thrombosis. Compression on veins from outside by enlarged uterus in pregnancy which compress the iliac veins → lower limb oedema. Rightsided heart failure. 2- Hypoprotienaemia. Due to: 1- Liver cell failure. 2- Severe kidney disease (Renal edema). 3- Increased capillary permeability: As in Allergic conditions. 55 Summary of Physiology 2023-2024 4- Lymphatic obstruction: As in filariasis: Because of the extreme edema of lower limbs this condition is called elephantiasis. Haemorrhage Definition: it is loss of blood from cardiovascular system. Types: 1) According to the site of haemorrhage: a) External haemorrhage. b) Internal haemorrhage. (more dangerous) 2) According to the rapidity of haemorrhage: a) Chronic haemorrhage: (repeated little bleeding) Occurs in piles, peptic ulcer, bilharziasis or anklystoma. It isn’t dangerous but may lead to iron deficiency anaemia. b) Acute haemorrhage: (excessive rapid bleeding) Depends on the amount of bleeding: ✓ If blood loss is ↓ 10% (0.5L or 1-5 ml/kg) → ABP little changed (as there is a series of compensatory reaction to maintain adequate arterial blood pressure). ✓ If blood loss 15-20% (1 L or 6-15 ml/kg) → moderate hypotension but recovers spontaneously. ✓ If blood loss 20-30% (1-1.5 L or 16-25 ml/kg) → early shock, usually reversible. ✓ If blood loss ↑ 30% (↑ 1.5 L or ↑ 25ml/kg) → serious shock, may be irreversible. Compensatory reactions of haemorrhage: 1) Immediate (rapid ) compensatory reactions: Start within seconds and last for minutes or hours. Aim: to maintain adequate arterial blood pressure to ensure sufficient blood supply for the vital organs. 2) Delayed (long term) compensatory reactions: Start within minutes and last as long as needed. Aim: to restore blood volume and blood components. I. Immediate (rapid ) compensatory reactions: 1. Blood coagulation: helped by increased fibrinogen by adrenaline secretion. 56 Summary of Physiology 2023-2024 2. Cardiovascular changes: A) ↑Heart rate. B) Vasoconstriction. 3. Respiratory changes: There is increase in the rate of respiration. 4. Endocrine changes: There is release of: 1- Epinephrine and norepinephrine: Released from adrenal medulla and causes vasoconstriction, increased heart rate & improves contractility. 2- Aldosterone: Released from adrenal cortex and causes salt and water retention. 3- Antidiuretic hormone: Released from posterior pituitary and causes water reabsorption by the kidney. 4- cortisol: Released from adrenal cortex and increases the resistance to stress. 5- Erythropoietin: Released from the kidney and stimulates erythropioesis. 5. Splenic contraction: Leads to pouring its stored concentrated blood (about 200 cc) into the circulation. Not important in humans. 6. Renal changes: Decreased urine formation through: ✓ ↓ ABP →↓ blood flow to the kidney. ✓ Vasoconstriction of renal blood vessels. ✓ ↑ ADH. ✓ Salt and water retention. II. Delayed (long term) compensatory reactions: 1. Restoration of water and electrolytes: Occurs within 12-72 hours by: thirst sensation, capillary fluid shift & decreased urine formation. 2. Restoration of plasma proteins: 57 Summary of Physiology 2023-2024 Rapid mechanism: by addition of proteins from the liver and tissues. This occurs within one hour. Slow mechanism: by synthesis of new proteins by the liver. This occurs within 3-4 days and needs high biological value proteins. 3. Restoration of R.B.Cs: Rapid mechanism: by splenic contraction. Slow mechanism: by stimulation of bone marrow to form new RBCs by erythropoietin hormone. This is occurs within 4 weeks. Manifestations of haemorrhage: 1. Rapid weak pulse. 2. Hypotension (according to amount of blood loss) 3. Shallow rapid breathing. 4. Dry mouth and thirst sensation. 5. ↓ Urine formation. 6. Pale, cold, sweaty skin. 7. Restlessness and anxiety. Cardiac output Definition: it is the amount of blood pumped from each ventricle \ minute. Usually, it refers to left ventricular output. Normal Value: in Normal adult it is about 5 L/min. Cardiac output = Stroke volume × Heart rate (number of heart beats) Stroke volume, is the amount of blood pumped out by each ventricle during each beat. Normal value: 70 mL (60 to 80 mL) when the heart rate is normal (72/minute). Factors controlling cardiac output 1. Venous return, it is the amount of blood which is returned to heart from different parts of the body. 2. Force of cardiac (ventricular) contraction 58 Summary of Physiology 2023-2024 3. Heart rate 4. Peripheral resistance. Endocrine glands Endocrine gland: It is a ductless gland which pours its secretion directly into the blood for regulation of cellular metabolism, growth &reproduction. Hormone: It is a Chemical messenger synthesized by endocrine glands and secreted directly into the blood to produce specific physiological action on other distant cells (target organs) The major endocrine glands include: 1) Pituitary gland (anterior and posterior lobs). 2) Thyroid gland. 3) Parathyroid glands. 4) Adrenal gland (cortex &medulla). 5) Pancreas (islet of Langerhans). 6) Gonads (testis and ovary). Pituitary gland It is the master of the endocrine glands as it controls the activities of some other glands. Lies inside the sella turcica at the base of the skull. Connected with the hypothalamus by the pituitary stalk. It is divided into : ▪ Anterior lobe (adenohypophysis): Glandular in nature. ▪ Posterior lobe (neurohypophysis): nervous in origin. ▪ Intermediated lobe: rudimentary in man. Hormones secreted by pituitary gland: The anterior lobe of the pituitary gland secretes Growth hormone (GH) Physiological action: 1. Effect on growth : GH promotes bone and soft tissue growth. 59 Summary of Physiology 2023-2024 A. Bone growth:  Leading to increased linear growth (stature) by: ✓ Stimulate proliferation of epiphyseal cartilage → widening of epiphyseal plate. ✓ Activate formation of osteoblasts. B. Soft tissue growth : ✓ As skeletal muscles, heart, kidney, liver & spleen by ↑Protein synthesis and protein deposition. 2. Metabolic action: Protein metabolism: → anabolic Carbohydrate metabolism : → diabetogenic (↑ blood glucose level) By:  Stimulate glycogenolysis & gluconeogenesis.  ↓ glucose utilization by tissues. Fat metabolism :  Lipolysis → ↑free fatty acids in plasma. =. Control of GH secretion: 1) Hypothalamic control: Through the secretion of GHRH (mainly) and GHIH. 2) Feedback control: Increased GH level in the blood inhibits the release of GHRH and stimulate the release of GHIH. Disorders of GH secretion I. Hyposecretion: A. Before puberty: 1) Pituitary dwarfism: isolated deficiency of GH. Leads to Short stature (the height is less than 1.2 meter), Delayed soft tissue growth with normal Mentality &sexual maturity. 2) Pituitary infantilism:  Pituitary dwarfism + hypogonadism.  It is due to decrease both of GH and gonadotropins.. B. In adults : Panhypopituitarism: Causes: 60 Summary of Physiology 2023-2024 1. Sheehan syndrome: pituitary necrosis due to hypotension and ischemia following severe postpartum haemorrhage 2. Tumors destroying pituitary tissue as non functioning chromophobe adenoma. Manifestations: 1. Hypogonadism: in the form of amenorrhea and breast atrophy in female or impotence and regression of secondary sex characters. 2. Hypothyroidism → ↓ BMR → hypothermia. 3. Hypocorticism. 4. Hypoglycaemia: due to ↓ GH, cortisol. 5. Marked pallor due to decreased MSH & ACTH. 6. Failure of lactation : the first sign to appear (due to ↓ prolactin secretion) II. Hyperfunction: A. Before puberty: → Gigantism Causes: increased GH secretion either due to: Manifestations: a. ↑ Linear growth → the patient height exceeds 2 meters b. Over growth of soft tissues : ✓ Muscles: ↑ in bulk so the patient at first is strong and powerful then he becomes weak and fatigue easily ✓ Viscera: enlarged → hepatomegaly, splenomegaly …etc (organomegaly) c. Metabolic disorders :  Hyperglycemia, insulin resistant Diabetes Mellitus.  Ketoacidosis. d. Pressure manifestations. B. After puberty: → Acromegaly Manifestations: 1) Increased thickness of : Short bones of the hands (spade hand) and feet. 61 Summary of Physiology 2023-2024 Skull → acromegalic face & Big skull. 2) Deep hoarse voice: due to hypertrophy of vocal cords. 3) Skin: coarse, thick, Wrinkled with excessive sweating (due to increased metabolism) & hirsutism may occur. 4) Gynaecomastia & lactation. Posterior pituitary 1) Anti-diuretic hormone (ADH) or vasopressin. 2) Oxytocin. Anti-diuretic hormone (vasopressin) Action: I. On the kidney: (the main action) Increase water reabsorption by the distal convoluted tubules (DCT) and collecting tubules (CT) of the nephrons passively by opening of water channels (aquaporin II channels) → water retention and urine concentration (antidiuresis). II. On smooth muscles: (in large pharmacological doses) Causes smooth muscle contraction. ✓ In blood vessels: → vasoconstriction. ✓ In sphincters: → colic. ✓ In uterus: → uterine contraction (oxytocin action). Receptors of vasopressin: 1. V1 receptors are found in: ✓ Smooth muscle→ contraction. Acts By the phospholipid breakdown products in smooth muscles. 2. V2 receptors: on DCT & CTs of the kidney. Acts by↑ c.AMP. Control of ADH secretion: 1. Osmotic pressure of the plasma:  ↑ Osmotic pressure of the plasma → ↑ ADH secretion. 62 Summary of Physiology 2023-2024  ↓ Osmotic pressure of the plasma → ↓ ADH secretion. 2. Plasma volume: ↑ Plasma volume → ↓ ADH secretion. This is done by stimulation of: ↓ Plasma volume (as in haemorrhage) → ↑ ADH secretion. 3. Stressful stimuli: Pain, exercise & emotions → ↑ ADH secretion. Cold inhibits ADH secretion. 4. Drugs: Morphine, nicotine & angiotensin II → ↑ ADH secretion. Alcohol inhibits ADH secretion. Abnormalities of ADH secretion: 1) Diabetes insipidus: Manifestations: a) Polyurea: ↑ urine volume (= diabetes) up to 20 liters / day or more. The urine is: ✓ Colorless (watery). ✓ Tasteless (= insipidus). ✓ Specific gravity is 1001-1003. b) Polydipsia: drinking large amounts of water (secondary to polyurea). c) Dehydration: if fluid intake is not adequate. d) Loss of water soluble vitamins. e) ↑ BMR: to maintain body temperature due to drinking large amounts of water with low temperature. f) Signs of ↑ intracranial tension, pressure manifestations: in the case of tumor. desmopressin; Synthetic drug has very high antidiuretic activity with little pressor activity, making it valuable in the treatment of vasopressin deficiency. Oxytocin Actions: 1. On the uterus: a) On pregnant uterus: uterine contractions. At the time of labour: to facilitate labour. After labour to: 63 Summary of Physiology 2023-2024 ✓ Prevent postpartum haemorrhage. ✓ Help involution of the uterus. b) On non pregnant uterus: During coitus: causes Reverse peristalsis of the uterus to help sperm transport. 2. On the breast: Milk ejection by contraction of myoepithelial cells surrounding the alveoli of the mammary gland. 3. In males: It may help transport of sperm in epidydmis and vas difference or it may have a role in ejaculation. 4. Weak anti-diuretic effect. Thyroid gland Lies in front of the neck. Consists of 2 lobes and an isthmus. Thyroid hormones: Follicular cells secrete T4 & T3. Parafollicullar C cells which secrete calcitonine (Ca2+ lowering hormone). Synthesis of thyroid hormones: 1. Iodine metabolism: Iodine supply from: sea fish, cod liver oil & plants that grow near the sea. Absorption: from the stomach and small intestine. 2. Iodide trapping: iodide uptake and concentration by the thyroid occurs by active transport. ✓ Stimulated by TSH. ✓ Inhibited by perchlorate and thiocyanate. 3. Oxidation of ionized iodide to elemental iodine I2: this reaction occurs in the colloid catalyzed by peroxidase enzyme. 4. Iodination of tyrosine attached to thyroglobulin to form mono- iodotyrosin and di-iodotyrosine. 64 Summary of Physiology 2023-2024 5. Oxidative coupling of: MIT with DIT → T3. DIT with DIT→ T4. ✓ Catalyzed by peroxidase. ✓ Inhibited by propylthiouracil. Physiological Actions of thyroxin: I. On metabolism 1. on general metabolism : ↑ B.M.R and O2 consumption of all tissues. ↑ Heat production. 2. on protein metabolism: Normal levels of thyroxin have anabolic effects. Excess levels leads to protein catabolism. 3. on carbohydrate metabolism : ↑ Liver glycogenolysis & Gluconeogenesis. ↑ Intestinal absorption of glucose. ↑ Glucose uptake and utilization. 4. On lipid metabolism : Stimulate lipolysis. II. On growth: Thyroxin is essential for physical, mental & sexual growth. ✓ on physical growth : Stimulate bone growth and ossification. Stimulate eruption and development of teeth. Stimulate Skin and hair follicle growth. Stimulate Skeletal muscle function and energy production ✓ On Mental growth : CNS development, growth & function. Myelination of nerves and development of synapses. ✓ On sexual growth : Essential for normal menstrual cycle and spermatogenesis. Essential for milk secretion. III. On body systems: 1) On cardiovascular system: ↑ Heart Rate, force contraction & C.O.P. 65 Summary of Physiology 2023-2024 ↑ Systolic BP but↓ diastolic BP. ↑ Blood flow to tissues. 2) On GIT: ↑ Appetite, gastric and intestinal secretions. ↑intestinal motility and absorption. 3) On bone marrow: stimulate erythropoiesis. Disorders of thyroid hormones secretion: Hypothyroidism: Before puberty → cretinism. Causes: 1) Congenital absence of the thyroid. 2) Iodine deficiency during pregnancy. Manifestations: I. Growth: a) Physical growth → delayed. ✓ Short stature (disproportionate) height > span. ✓ Delayed dentition & closure of fontanelles. ✓ Delayed sitting and walking…… ✓ Weak musculature. b) Mental growth : ✓ The cretin is idiot (mentally retarded). ✓ Delayed speech. ✓ Incontinence of urine & stool. c) Sexual growth : ✓ Sex organs remain infantile → sterility & impotence. II. Characteristic features: Face: ✓ Swollen eyelids with narrow palpebral fissure. ✓ Depressed nose with wide nostrils. ✓ Thick lips enlarged protruded tongue. Abdomen: bulging and umbilical hernia due to muscle weakness and constipation. Skin: cold, pale dry with scanty hair. 66 Summary of Physiology 2023-2024 III. Metabolism: ↓ BMR, cold intolerance, ↑serum cholesterol. Treatment: Thyroid hormones are given early after birth (before the age of 6 months) to avoid permanent mental retardation. Hypofunction After puberty → Myxoedema: Causes: Autoimmune disease (Hashimoto‫יִ‬s thyroiditis): characterized by formation of destructive antibodies against thyroid tissue. Surgical removal. Severe Iodine deficiency → endemic goiter. Intake of goitrogens. Manifestation: 1. General metabolism: ↓ BMR to - 40%. ↑ Body weight. Cold intolerance & Body temperature is subnormal. 2. Protein metabolism: ↑ protein in plasma, liver, heart & skin → retention of subcutaneous fluid rich in protein under the skin called myxoedematous tissue 3. Carbohydrate metabolism: ↑ Muscle and liver glycogen. ↓ Intestinal absorption of glucose. 4. Lipid metabolism: ↑cholesterol level. Fatty infiltration of the liver. 5. CNS: Depressed mental function (poor memory, slow thinking, apathy, ↑ sleep (somnolence). Depressed deep reflexes. 67 Summary of Physiology 2023-2024 Coma due to hypothermia, hypoventilation, hypotension in severe cases. 6. CVS: ↓ HR, ↓ COP. Myocardium weakness. 7. Respiratory system : hypoventilation 8. GIT: anorexia, constipation, anacidity. 9. Gonads: Depressed sexual function. ↓ Milk secretion. 10. Blood: ↑ Cholesterol, plasma proteins & phospholipids levels. Anaemia: ↓ Vitamin A level and ↑ carotene level (hypercarotenaemia) manifested by yellow skin (carotenoderma). 11. Eye: Swollen eyelids with puffiness of the face Loss of hair from outer 1/3 of the eyebrow. Hyperthyroidism (thyrotoxicosis) Causes: 1. Mainly due to Grave‫יִ‬s disease. It is an autoimmune disease characterized by formation of antibodies against TSH receptors which activate these receptors → hypersecretion of thyroxin so called long acting thyroid stimulators LATS which are not controlled by the negative feedback mechanism. Manifestations: 1. General metabolism: ↑ BMR to + 100%. ↓ Body weight inspite of good appetite. Heat intolerance. 2. Protein metabolism: ↑ protein catabolism leading to: ✓ Muscle weakness and easy fatigability. 68 Summary of Physiology 2023-2024 ✓ ↓ Body weight. ✓ Osteoporosis. 3. Carbohydrate metabolism: Glucose tolerance curve shows: ✓ Low fasting blood glucose level. ✓ Sharp rise after glucose intake (due to rapid absorption). ✓ Rapid fall due to rapid utilization. 4. Lipid metabolism: ↓ Cholesterol level. 5. CNS: Irritability, restlessness or insomnia. Exaggerated deep reflexes. Fine tremors: in the tongue and outstretched hand. 6. CVS: ↑ HR (sleeping pulse > 100 beats / minutes. ↑ COP. ↑ Systolic BP & ↓ diastolic BP → ↑ pulse pressure (water hammer pulse). Heart failure inspite of high COP (high COP heart failure) when the heart fails to supply tissues with their needs. 7. Respiratory system : hyperventilation 8. GIT: ↑ appetite & diarrhea. 9. skin: warm & flushed (due to vasodilatation) & moist (due to excess sweat secretion) 10.Eye: Lid retraction: due to spasm of Muller‫יִ‬s muscle leading to → ✓ Widening of palpebral fissure → starring look. Exophthalmos: protrusion of the eyeball. Treatment: Propylthiouracil. Radioactive iodine. Surgery: subtotal thyroidectomy. Control of thyroid hormone secretion: 1. Hypothalamic control: 69 Summary of Physiology 2023-2024 By secretion of TRH from hypothalamus. 2. Pituitary control: By secretion of TSH 3. Feedback mechanism. 4. Iodine supply: Iodine deficiency → ↓ thyroid hormone secretion. Large doses of iodides produce mild, transient inhibition of thyroid hormone synthesis (Wolf-Chaikoff phenomenon). So, iodides in large doses are used to reduce secretion, size & the vascularity of the gland preoperatively. 5. Antithyroid agents: Drugs: ✓ Thiocyanate & perchlorate. ✓ Propylthiouracil. ✓ Large doses of iodides. Naturally occurring goitrogens: in cabbage, cauliflower and turnip. Goiter Definition: Enlargement of the thyroid gland. It may be accompanied by normal, hypo- or Hyperfunction. Thyroid function tests:. I. Specific tests: By measuring the level of Free T3, T4 & TSH in plasma by radioimmunoassay. Parathyroid gland There are four parathyroid glands located on the posterior surface of the thyroid gland (2 embedded in the superior pole and 2 embedded in the inferior pole). Secretes parathormone hormone They are essential for life, deficiency of its hormones leads to death due to spasm of laryngeal and respiratory muscles. 70 Summary of Physiology 2023-2024. Normal calcium level is 9 -11 mg / dl. . Functions of parathormone: PTH ↑ Ca+2 level and ↓ PO4-3 level by action on: kidney, bone & intestine. 1. Effect on kidney: 1) Inhibit PO4-3 reabsorption by PCT: This leads to: ↓ PO4-3 in plasma and ↑ in urine. ?