MBBS-1 Applied Homeostasis PDF

MBBS-1 APPLIED HOMEOSTASIS Department of Physiology Faculty of Medicine  Desired Learning Outcomes On completion of this topic, you should be able to: 1.Explain homeostasis at the cellular level. 2.Differentiate between homeostasis and allostasis. 3.Explain — adaptation, acclimati...

MBBS-1 APPLIED HOMEOSTASIS Department of Physiology Faculty of Medicine  Desired Learning Outcomes On completion of this topic, you should be able to: 1.Explain homeostasis at the cellular level. 2.Differentiate between homeostasis and allostasis. 3.Explain — adaptation, acclimatization, biological clock, apoptosis. 4. State the effects of increased demand or stress on a normal cell.  INTRO: THE CELL Cell – termed coined by Robert Hooke – 1665 Cell Theory – Schleiden and Schwann -1839 – Cell is the structural and functional unit of all living organisms – All life forms are made from one or more cells -Cells arise only from pre-existing cells -Cells is the smallest form of life as the structural basis of living organisms “ The basic living unit of the body is the cell”  THE CELL Entire body – 100 trillion cells Each cell is specially adapted to perform one or few specific functions Cells differ markedly from one another Cells have basic functional characteristics – e.g: metabolism Cells deliver end products to the surrounding medium All cells have the ability to reproduce additional cells of their own kind  THE CELL Collections of CELL with similar function – Tissues Organ – contains many types of tissues System – consists of several organs The proper functioning of body cells depends on precise regulation of the composition of the interstitial fluid surrounding them. Because of this, interstitial fluid is often called the body’s internal environment. The composition of interstitial fluid changes as substances move back and forth between it and blood plasma. Such exchange of materials occurs across the thin walls of the smallest blood vessels in the body, the blood capillaries. This movement in both directions across capillary walls provides needed materials, such as glucose, oxygen, ions, and so on, to tissue cells. It also removes wastes, such as carbon dioxide, from interstitial fluid  INTERNAL ENVIRONMENT Unicellular organisms – e.g; Amoeba – totally dependent on the external aquatic medium Muliticellular organisms , by and large, are independent of the external environment Reason - ‘ millieu interieur’ or the internal environment – Claude Bernard (1887)  millieu interieur “ The living body though it has need of the surrounding environment, is nevertheless relatively independent of it. This independence, which the organism has of its external environment, derives from the fact that the in the tissues living being, are in fact withdrawn from direct external influences and are protected by a veritable internal environment which is constituted in particular by the fluids circulating in the body” – Claude Bernard.  INTERNAL ENVIRONMENT An important aspect of homeostasis is maintaining the volume and composition of body fluids, dilute, watery solutions containing dissolved chemicals that are found inside cells as well as surrounding them. Internal environment is the watery medium that bathes all the cells of the body This is termed the EXTRACELLULAR FLUID (ECF) ECF comprises the PLASMA of blood and the INTERCELLULAR FLUID (interstitial fluid) surrounding the cells of the body The fluid contained within the cells is termed the INTRACELLULAR FLUID (ICF) ECF contains large amounts of NaCl, HCO3 ions and nutrients plus waste products – e.g; carbon dioxide ICF differs significantly from ECF – contains large amounts of Potassium, Phosphate and Magnesium ions The fluid within cells is intracellular fluid (intra- inside), abbreviated ICF. The fluid outside body cells is extracellular fluid (extra- outside), abbreviated ECF. The ECF that fills the narrow spaces between cells of tissues is known as interstitial fluid (inter-STISH- al; inter- between). Dynamic exchange exists between ECF and ICF Cells derive their nutrients from their immediate ECF, even though the constituents of the ECF are ultimately derived from the external environment This confers , in higher organisms, certain level of independence from their external environment Summary:The fluid within cells is intracellular fluid (intra- inside), abbreviated ICF. The fluid outside body cells is extracellular fluid (extra- outside), abbreviated ECF. The ECF that fills the narrow spaces between cells of tissues is known as interstitial fluid (in-ter-STISH-al; inter- between). interstitial fluid is often called the body’s internal environment.  Cell-cell communication The human body is composed of trillions of cells. Those cells need to communicate with one another in a rapid and effective manner to convey physiological information.  What do celsneedto communicate effectively? Language (that they can mutually understand) Electrical and chemical signals There are FOUR basic methods of cell-to-cell communication in our bodies: (1)gap junctions which allow direct cytoplasmic transfer of electricaland chemical signals between adjacent cells. (2)contact-dependent signals, in which surface molecules on one cell membrane bind to surface molecules on another cellmembrane. (3)local communication is accomplished by paracrine and autocrine signaling that is mediated by chemicals that diffuse through the extracellular fluid. (4)long-distance communication through a combination of electrical signals carried by nerve cells and chemical signals transported in the blood.  Identify the type of communication? C D B A Gap junctions form direct cytoplasmic connections between adjacent cells. Contact-dependent signals require interaction membrane between molecules on two cells. Autocrine signals act on the same cell that secreted them. Paracrine signals are secreted by one cell and diffuse to adjacent cells.  Important characteristics of each type of cell-cell communication Gap junctions -Theyare not all alike(Different in different tissues) -20 different connexin isoforms. -Theonly waythat allow direct transfer of electric signalsin-between the cells. Contact-dependentsignals - It ismediatedby Celladhesion molecules (CAMS) - Such contact-dependent signalling occurs in the immune systemand during growth and development. - CAMshavenow been shown to act asreceptors in cell- to-cell signaling. - CAMs are linked to the cytoskeleton and to intracellular enzymes. Through these linkages, CAMs transfer signals in both directions across cell membranes.  Local communications are carried out by ParacrineandAutocrine Signals -In somecases amolecule mayact as both an autocrine signal and a paracrine signal. -All cels in the body canrelease paracrine signals. -The signal molecules reach their target cells by diffusing through the interstitial fluid. Because distance is a limiting factor for diffusion, the effective range of paracrine signals is restricted to adjacent cells. -An example of a paracrine molecule is histamine, a chemical released from damaged cells. When you scratch yourself with a pin, the red, raised wheal that results is due in part to the local release of histamine from the injured tissue.  Communications: Electrical or Chemical Long-distance communication between cells is the responsibilityof the nervousand endocrinesystems. The endocrine system communicates by using hormones; chemical signals that are secreted into the blood and distributed all over the body by the circulation. Hormones come in contact with most cells of the body, but only those cells with receptors for the hormone are targetcells  Thenervoussystem usesa combination of chemical signals andelectrical signals. - An electrical signal travels along a nerve cell (neuron) until it reaches the terminal end of the cell, where it is translated into a chemical signal secreted by the neuron. Such a chemical signal is called aneurocrine. If aneurocrine molecule diffuses from the neuron acrossa narrow extracellularspace to atargetcell and has a rapid effect, it is called a neurotransmitter  If aneurocrine actsmore slowly asanautocrine or paracrine signal,it iscalled a neuromodulator. If aneurocrine releasedby aneuron diffuses into the blood for distribution, it iscalled a neurohormone  Cellular signaling is primarily chemical Cells can detect both chemical and physical signals. Physical signals are generally converted to chemical signals at the level of the receptor. Receptors sense diverse stimuli but initiate a limited repertoire of cellular signals Receptors contain: a ligand-binding domain and an effector domain Cells may express different receptors for the same ligand. The same ligand may have different effects on the cell depending on the effector domain of its receptor. Ligand binding drives the receptor toward the active conformation Signals are sorted and integrated in signaling pathways (usually multisteps and comprise activation of secondary messengers) Second messengers provide readily diffusible pathways for information Overview of cellsignalling  Intro-Homeostasis Homeostasis (ho¯me¯-o¯-STA ¯ -sis; homeo- sameness; -stasis standing still) is the condition of equilibrium (balance) in the body’s internal environment due to the constant interaction of the body’s many regulatory processes. Homeostasis is a dynamic condition. In response to changing conditions, the body’s equilibrium can shift among points in a narrow range that is compatible with maintaining life. For example, the level of glucose in blood normally stays between 70 and 110 milligrams of glucose per 100 milliliters of blood. Each structure, from the cellular level to the systemic level, contributes in some way to keeping the internal environment of the body within normal limits.  HOMEOSTASIS -CONTROL SYSTEMS Homeostasis in the human body is continually being disturbed. Some disruptions come from the external environment in the form of physical insults such as the intense heat or a lack of enough oxygen. Other disruptions originate in the internal environment, such as a blood glucose level that falls too low when you skip breakfast. Homeostatic imbalances may also occur due to psychological stresses in our social environment—the demands of work and school, for example. In most cases the disruption of homeostasis is mild and temporary, and the responses of body cells quickly restore balance in the internal environment However, in some cases the disruption of homeostasis may be intense and prolonged, as in poisoning, overexposure to temperature extreme’s, severe infection, or major surgery.  CONTROL SYSTEMS - TYPES The body can regulate its internal environment through many feedback systems. A feedback system or feedback loop is a cycle of events in which the status of a body condition is monitored, evaluated, changed, re-monitored, re-evaluated Each monitored variable, such as body temperature, blood pressure, or blood glucose level, is termed a controlled condition. Any disruption that changes a controlled condition is called a stimulus. Components: A feedback system includes three basic components—a receptor, a control center, and an effector Homeostatic control mechanisms have at least 3 interdependent components: Receptor - sensor that responds to stimuli Control centre - determines set point, analyses input and determines appropriate response(output) Effector - provides means for control centres response.  Components: A receptor is a body structure that monitors changes in a controlled condition and sends input to a control center. Typically, the input is in the form of nerve impulses or chemical signals. A control center in the body, for example, the brain, sets the range of values within which a controlled condition should be maintained, evaluates the input it receives from receptors, and generates output commands when they are needed. Output from the control center typically occurs as nerve impulses, or hormones or other chemical signals. An effector is a body structure that receives output from the control center and produces a response or effect that changes the controlled condition. Nearly every organ or tissue in the body can behave as an effector  FEEDBACK SYSTEM A group of receptors and effectors communicating with their control center forms a feedback system that can regulate a controlled condition in the body’s internal environment. In a feedback system, the response of the system “feeds back” information to change the controlled condition in some way, either negating it (negative feedback) or enhancing it (positive feedback). 1.NEGATIVE FEEDBACK 2.POSITIVE FEEDBACK 3.FEEDFORWARD CONTROL  HOMEOSTATIC MECHANISMS MAY FAIL DUE TO.. Congenital metabolic disorders Ageing ( Homeostenosis) Chromosomal abnormalities Environment Factors -UV radiation -Chemical pollutants  Homeostatic Imbalance Disturbances of homeostasis or the body`s normal equilibrium. Overwhelming of negative feedback mechanism by destructive positive feedback mechanisms. Homeostatic Imbalances In The Body 1. Integumentary system – Burns, cutaneous lesions (cold sores, Psoriasis ), skin cancer. 2. Skeletal System – Rickets, Abnormal spinal curvatures (Scoliosis,kyphosis,lordosis), Osteoporosis. 3. Muscular System – Muscular Dystrophy, Myasthenia Gravis. 4.Nervous system – Multiple sclerosis, Huntington’s disease, Parkinson’s disease, Alzheimers disease. 5.Endocrine System – Goitre, Grave’s disease, Pituitary dwarfism, Infertility. 6. CVS – Pericarditis. Valvular stenosis, Varicose veins, Atherosclerosis. 7.Lymphatic System – Allergies, Immunodeficiencies (AIDS), Autoimmune disease ( Lupus, Rheumatoid Arthritis, etc ). 8.Respiratory System – Sinusitis, tonsillitis, Pleurisy, Emphysema, Bronchitis, Cystic fibrosis 9.Digestive System – Gall stones, Heartburn, Gastric ulcers. 10.Urinary System- Kidney stones, Addison’sdisease, Polycystic kidney disease. 11.Reproductive system – Pelvic inflammatory disease, Cervical cancer, Testicular cancer. HomeostasismodelversusAllostasis model Homeostasis Allostasis  Homeostasis-SETPOINT - Homeostasis means stability through constancy. - There is a set point for the variable as body temperature. Any tendency to deviate it from the set point, there are mechanisms to bring it back to the set point. - Some parameters are regulated quite closely to their set point as oxygen, pH, temperature, glucose and osmotic pressure. - Failure of homeostasis results in diseases. Failure of the pancreas to release insulin results in diabetes.  Allostasis In Allostasis there is prediction of the needs of the body that results in re-setting of the set point. The body organs try to achieve thenew set point. If that is happening for short periods of time it is physiological but if it happens for sustained time it mayturn to a pathology. Theprediction is the function ofour brain (howwe perceiveand plan to act). Examplesare exerciseand exposureto stress. Reponsesof a normal cellto stress & cellularinjuries  Examplesof cell injuries and type ofcellular response Injuries Cellularresponse 1) Altered physiological stimuli as: - Increased stimulation (increasedGH -Hypertrophy release) &Hyperplasia Adaptation - Decreasedstimulation -Atrophy -Chronicirritation - Metaplasia 2)Chemicalinjuriesand reducedoxygen supply : - Acutetransient - Acutereversibleinjury - Progressive andsevere - Irreversible cellinjury Celldeath  Adaptation Adaptations are reversible changes in the size, number, phenotype, metabolic activity, or functions of cells in response to severe physiologic or pathologic changesin their environment. Forms of adaptations: Hypertrophy refers to an increase in the size of cells, resulting in an increase in the size of the organ. The increased size of the cells is due to the synthesis of more structural components of the cells. The main stimulus for hypertrophy is 1.increased workload ascardiachypertrophy due to hypertension 2.excessivestimulation asuterus hypertrophy during pregnancy (oestrogenstimulation). 3.druginduced. Whatever the exact cause and mechanism of cardiac hypertrophy, it eventually reaches a limit beyond which enlargement of muscle mass is no longer able to compensate for the increased burden. In extreme cases myocyte death can occur by either apoptosis or necrosis. The net result of thesechangesis cardiac failure. Mechanisms of hypertrophy increased production of cellular proteins triggered by growth factors (including TGF- β, insulin-like growth factor-1 [IGF-1], fibroblast growth factor), and vasoactive agents (such as α-adrenergic agonists,endothelin-1, and angiotensin II). Hyperplasia is an increase in the number of ce ls in an organ or tissue, usually resulting in increased mass of the organ or tissue. Hyperplasia takes place if the cell population is capable of dividing. Hyperplasia can be physiologicor pathologicand occurtogether withhypertrophy. Causes/types ofhyperplasia Physiologic Hyperplasia as hormonal hyperplasia as proliferation of the glandular epithelium of the female breast at puberty and during pregnancy by hormones. It is usually accompanied by enlargement (hypertrophy) of the glandular epithelial cells. Compensatory hyperplasia that is seen after damage or partial resection of a tissue as in individuals who donate one lobe of the liver for transplantation, the remainingcellsproliferate sothat the organsoongrows backto its originalsize. Pathologic Hyperplasia which are mostly caused by excesses of hormones or growth factors acting on target cells. Endometrial hyperplasia is an example of abnormal hormone-inducedhyperplasia and that is induced by viral infections.  Atrophy is reduced size of an organ or tissue resulting from a decrease in cell sizeand number.It canbe physiologic or pathologic. Physiologic atrophyis commonduring normal development. Onemore exampleis decreased uterus sizeshortly after parturition, and this is aform of physiologic atrophy. Causes of atrophy Decreased workload (disuse atrophy). - Exampleis immobilization when a bone is fractured.Theinitial decreasein cell sizeisreversibleonceactivity is resumed. Loss of innervation (denervation atrophy).Damageto the nerves leadsto atrophyof the musclefiberssupplied by thosenerves. Diminishedblood supply.Adecreasein blood supply (ischemia) to atissue as a result of slowly developing arterial occlusive diseaseresults in atrophy of the tissue. Inadequatenutrition. Loss of endocrinestimulation. Pressure,tissue compression forany lengthof timecancauseatrophy. Mechanisms ofAtrophy - Decreasedprotein synthesis and increasedprotein degradation in cels. Metaplasia is a reversible change in which one differentiated cell type is replaced by another celltype. The most common epithelial metaplasia is columnar to squamous , as occurs in the respiratory tract in response to chronicirritation. The normal ciliated columnar epithelial cel s of the trachea and bronchi are often replaced by stratified squamousepithelial cels. The influences that predispose to metaplasia, if persistent, may initiate malignant transformation  Acclimatization Acclimatization describes adaptive physiological or behavioural changes within an organism in responseto their natural climateor environment. Usual y completely reversible once stress is removed, body reverts back to pre- acclimatization condition. Humansgo and stay a high altitude (where oxygen is low) naturally acclimatize to their new environment by developing an increase in the number of red blood cells to increase the oxygen carrying capacity of the blood, in order to compensatefor lower levels of oxygen in the air. This acclimatization is a slow process that may takes days to few  Apoptosis: Programmed Cell Death The total number of cells is regulated in our body is regulated by controlling the rate of cell division andthe rate of celldeath. When cells are no longerneededor become a threat to the organism,they undergoa suicidalprogrammed cell death, orapoptosis. Studies suggestthat abnormalities of apoptosis mayplayakeyrole in neurodegenerative diseasessuch as Alzheimer’s disease. Somedrugsthat havebeen usedsuccessfully for chemotherapy appearto induce apoptosisin cancercells.  Mechanism of apoptosis This process involves a specific proteolytic cascade that causes the cell to shrink and condense, to disassemble its cytoskeleton, and to alter its cell surface so that a neighboring phagocytic cell, such as a macrophage, can attach to the cell membraneand digest the cell.  BIOLOGICALCLOCK Biological clock is an inherent timing mechanism in a living system (as a cell) that is inferred to exist in order to explain various cyclical behaviors and physiological processes. Thecyclical changescanbedaily, monthly, or seasonal Diurnal variations in our body temperature, arterial blood pressure,bronchialtone, cortisollevel andothers. It explainthe reasonof patientswith getting their attacks late night or early morning. It canalsoexplainthe better timing for  SuprachiasmaticNucleus(SCN) is the centrefor control of the biologicalclock APPLIED HOMEOSTASIS A dehydrated patient with sunken eyes, loss of skin elasticity, & drowsiness  Tutorial 1. Define ‘Homeostasis’,and control system 2. Explain the mechanism of homeostasis with a common example. 3. State basic methods of cell-to-cell communication in the human body. 4. Differentiate homeostasis from a lostasis citing one example for each. 5. State the significance of cellularapoptosis. 6. Explain applied physiology of Homeostasis with examples Thank you Lecture 2: Body Fluids and Composition MBBS YEAR 1 DR. ROS  DESIRED LEARNING OUTCOMES : On completion of this topic, you should be able to: 1. List the bodily fluid compartments & state the ionic composition of each. 2. State the importance of barriers between compartments. 3. Explain the mechanism of fluid exchange between bodily fluid compartments. 4. State its importance in health and disease. Solution  Total body water Water is the most abundant molecule in the body. A body fluid is a substance, usually a liquid, that is produced by the body and consists of water and dissolved solutes. Fluid balance is closely related to electrolyte balance. Constituting about 50% of total body weight in females ages 17 to 39, and 60% of total body weight in males of the same age group.  Sources of Body Water Gain and Loss Body fluid volume remains constant because water loss equals water gain. The body can gain water by ingestion and by metabolic synthesis. The main sources of body water are ingested liquids (about 1600 mL) and moist foods (about 700 mL) absorbed from the gastrointestinal (GI) tract, which total about 2300 mL/day. Metabolic water is produced during aerobic respiration (200 mL/day). Daily water gain from these 2 sources totals about 2500 mL.  Sources of Body Water Gain and Loss On average, daily water loss totals about 2500 mL. Water loss occurs in 4 ways: Each day the kidneys excrete about 1500 mL in urine The skin evaporates about 600 mL. Lungs exhale about 300 mL as water vapor. Gastrointestinal tract eliminates about 100 mL in feces. In women of reproductive age, additional water is lost in menstrual flow.  Body fluid Body fluids are present in two main “compartments”—inside cells and outside cells. Intracellular fluid (ICF) = fluid within cells. 2/3 of body fluid. Also known as cytosol. Extracellular fluid (ECF) = fluid outside cells and includes all other body fluids. 1/3 of body fluid. 80% of the ECF is interstitial fluid which occupies the microscopic spaces between tissue cells 20% of the ECF is blood plasma, the liquid portion of the blood. 50% 50%  Minor ECF Compartments Other extracellular fluids that are grouped with interstitial fluid include lymph in lymphatic vessels and transcellular fluid. Transcellular fluid consists of a number of small, specialized fluid volumes, all of which are secreted by specific cells into a particular body cavity to perform some specialized functions. Cerebrospinal fluid in the nervous system Synovial fluid in joints. Intraocular fluid in the eyes. Endolymph and perilymph in the ears. Digestive juices. Pleural, pericardial, and peritoneal fluids between serous membranes.  Barriers between compartments 1. Plasma membrane of individual cells. It separates intracellular fluid from the surrounding interstitial fluid. It is a highly selective plasma membrane that permits passage of certain materials while excluding others Active transport pumps work continuously to maintain different concentrations of certain ions in the cytosol and interstitial fluid.  Barriers between compartments 2. Blood vessel walls Divide the interstitial fluid from blood plasma. Only in capillaries, the smallest blood vessels, are the walls thin enough and leaky enough to permit the exchange of water and solutes between blood plasma and interstitial fluid. Plasma and interstitial fluid are nearly identical in composition, except that interstitial fluid lacks plasma proteins. Ionic composition of the major body-fluid compartments  Major differences between ECF and ICF 1. The presence of cell proteins in the ICF that cannot permeate the enveloping membranes to leave the cells. 2. The unequal distribution of Na+ and K+ and their attendant anions (negatively charged ions) as a result of the action of the membrane bound Na+-K+ pump present in all cells. In the ECF, Na+ is accompanied primarily by the anion chloride (Cl-) and to a lesser extent by bicarbonate (HCO3-). The major intracellular anions are phosphate (PO43-) and the negatively charged proteins trapped within the cell.  Fluid balance 2 factors are regulated to maintain fluid balance in the body: ECF volume ECF osmolarity.  1. ECF volume Must be closely regulated to help maintain blood pressure. A reduction in ECF volume causes a fall in arterial blood pressure by decreasing plasma volume and vice versa. 1. Short term: The baroreceptor reflex alters both cardiac output (CO) and total peripheral resistance (TPR) to adjust blood pressure. BP low → CO & TPR increase → BP increase. Fluid shifts occur temporarily and automatically between plasma and interstitial fluid. Reduction in plasma volume → shift of fluid out of the interstitial compartment into the blood vessels. Increased in plasma volume → excess fluid shifts into the interstitial compartment. 2. Long-term : regulation of blood pressure by the kidneys (maintaining salt balance) and the thirst mechanism, which control urinary output and fluid intake, respectively.  2. ECF osmolarity Must be closely regulated to prevent swelling or shrinking of cells. Maintaining water balance is the primary importance in regulating ECF osmolarity. The osmolarity of a fluid is a measure of the concentration of the individual solute particles dissolved in it. The higher the osmolarity, the higher the concentration of solutes → the lower the concentration of H2O.  Osmolarity of body fluid At normal fluid balance and solute concentration, the body fluids are isotonic at an osmolarity of 300 milliosmols per liter (mOsm/L). If too much H2O is present relative to the solute load, the body fluids are hypotonic, which means they are too dilute at an osmolarity less than 300 mOsm/L. However, if a H2O deficit exists relative to the solute load, the body fluids are too concentrated or are hypertonic, having an osmolarity greater than 300 mOsm/L.  Importance of Regulating ECF Osmolarity Hypertonicity of the ECF, the excessive concentration of ECF solutes, is usually associated with dehydration. Hypotonicity of the ECF is associated with overhydration. The condition of overhydration, hypotonicity, and cellular swelling resulting from excess free H2O retention is known as water intoxication. ECF osmolarity has to be maintained within narrow limits to prevent the cells from shrinking (by osmotically losing water to the ECF) or swelling (by osmotically gaining fluid from the ECF).  Tonicity and osmotic water movement The tonicity of a solution is the effect the solution has on cell volume—whether the cell remains the same size, swells, or shrinks Summary of the regulation of ECF volume and osmolarity  Fluid exchange between ICF & ECF Influenced by: Osmotic pressure Hydrostatic pressure 1. Osmotic pressure : a measure of the tendency for osmotic flow of water into that solution because of its relative concentration of nonpenetrating solutes and water. 2. Hydrostatic pressure : is the pressure exerted by a standing, or stationary, fluid on an object (membrane).  Water intoxication Hypotonicity of the ECF is associated with overhydration—that is, excess H2O. Usually, any surplus H2O is promptly excreted in the urine, so hypotonicity generally does not occur. However, hypotonicity arises in 3 ways: 1. Patients with renal failure who cannot excrete dilute urine and become hypotonic when they consume relatively more H2O than solutes. 2. Hypotonicity occurs transiently in healthy people if H2O is rapidly ingested to such an excess that the kidneys cannot respond quickly enough to eliminate the extra H2O. 3. Hypotonicity occurs when excess H2O without solute is retained in the body as a result of the syndrome of inappropriate vasopressin secretion → the body to retain too much water.  Excess H2O retention first dilutes the ECF, making it hypotonic. The H2O move by osmosis from the more dilute ECF into the cell → cells swelling. Swelling of brain cells → brain dysfunction. Symptoms include confusion, irritability, lethargy, headache, dizziness, vomiting, drowsiness, and in severe cases, convulsions, coma, and death. Nonneural symptoms of overhydration include weakness caused by swelling of muscle cells and circulatory disturbances, including hypertension and edema, caused by expansion of plasma volume. The condition of overhydration, hypotonicity, and cellular swelling resulting from excess free H2O retention is known as water intoxication.  Tutorial questions 1. Briefly describe the body fluid compartments. 2. Give the compositions of ECF and ICF. 3. Describe the barriers between the body fluid compartments. 4. Discuss the sources of body water gain and loss in normal conditions. 5. Describe the changes in cell volume when a cell is placed in a hypotonic solution & hypertonic solution. Biophysical principles Dr.Jinu  VELOCITY VERSUS PRESSURE ❑ Change in the pressure in a hydraulic system changes the velocity of fluid movement  VELOCITY VERSUS PRESSURE Pressure in a hydraulic system has two compartments: Lateral pressure –is the side pressure that is exerted constantly on the wall of the tube. Dynamic pressure- is affected by the kinetic energy of the flow. Total pressure(always constant) -LP+DP  Lateral pressure in the blood vessel determines the degree of perfusion  BERNOULLI’S PRINCIPLE States that the total pressure in a closed system remains always constant As the total pressure does not change, the alteration in any component of pressure occurs at the cost of the other. Especially, change in dynamic pressure component that occurs frequently in a hydraulic system changes the lateral pressure.  In circulatory Narrowing of system blood vessel Velocity ↑es In circulatory system, at the sites of ↑ Dynamic narrowing of blood vessel the velocity of pressure flow increases, which in turn increases ↓ Lateral pressure the dynamic component of the pressure. The increase in dynamic pressure ↓es tissue perfusion decreases the lateral pressure APPLIED ASPECT Narrowed aortic valve Myocardial infarction ↑es velocity of aortic flow is common in aortic stenosis ↑dynamic pressure ↓ lateral pressure Coronary arteries originate from the root of aorta receive less blood Induces myocardial ischemia  Types of blood flow Laminar Turbulent Laminar/stream line flow  Laminar Flow Normally, flow of blood in the vessels is laminar in nature (laminar means ‘in layers’) Laminar flow is also called streamline flow. The layer of the blood, which is in close contact with the wall of the vessel, does not move at all due to the frictional resistance with the vessel wall, the next layer moves with lesser velocity. The velocity slowly increases toward the center of the vessel. The velocity of flow is maximal in the central layer of blood in the vessel  CRITICAL VELOCITY Velocity of flow at which blood flow becomes turbulent Turbulence of flow depends on the diameter of the vessel and the viscosity of the blood The probability of turbulence--- Reynolds number ρ- Density of blood(Greek letter rho) Re = ρDV/ η D- Diameter of the vessel in cm, V- Velocity of blood flow in cm/sec η (eta)– Viscosity of the blood  The probability of turbulence increases when the value of ‘Re’ is greater. Usually, when the ‘Re’ is less than 2000 the flow is laminar and when the ‘Re’ is more than 3000 the flow is turbulent.  APPLIED ASPECTS Turbulence of flow produces sound Eg:- Bruit- Auscultated over an arterial constriction Murmur – Heard over a stenosed cardiac valve Korotkov sounds – Due to constriction of brachial artery by inflated BP cuff during measurement of BP by auscultatory method FLOW, PRESSURE AND RESISTANCE Pressure is a principle determinant of rate of flow. Ohm’s law Current (I) = Electromotive force /Resistance In vascular system Flow (F) = Pressure (P)/Resistance P – Effective perfusion pressure R – Peripheral resistance Poiseuille-Hagen Formula Poiseuille-Hagen formula denotes the relationship bet ween viscosity of the fluid with the radius and length of the tube. POISEUILLE- HAGEN FORMULA F=P/R So R = 8η L r F π r4  PERIPHERAL RESISTANCE PR is determined by two factors Caliber of the blood vessel/ Vascular hindrance Viscosity of blood / Hematological hindrance  Vascular hindrance Radius of the blood vessel significantly affects PR. Vasoconstriction increase and vasodilation decreases PR Hematological hindrance Viscosity affects the peripheral resistance which is called Haematological hindrance E.g: Hematocrit CRITICAL CLOSING PRESSURE In capillaries, the flow ceases when pressure is reduced beyond a point The pressure at which flow stops is called critical closing pressure. MEASUREMENT OF BLOOD PRESSURE Methods of measurement of blood pressure are broadly divided into two categories: (1) Direct methods and (2) Indirect methods.  Direct Methods The blood pressure is measured directly by placing a cannula in the artery and connecting the cannula to a mercury manometer or a pressure transducer. Indirect Methods Blood pressure is usually measured with the help of a sphygmomanometer. The procedure is called sphygmomanometry. Indirect Methods Palpatory Method Auscultatory Method Indirect method (Sphygmomanometry ) Principle of sphygmomanometer The cuff is wrapped around the patient's arm and inflated until the brachial artery is compressed and blood flow is stopped. After that, the pressure is slowly released and the rushing blood produces a vibration around the vessel tissue, which is heard using a stethoscope.  In auscultatory method, pressure in the cuff is raised by about 20 mm Hg above palpatory level and then progressively lowered during which brachial artery is auscultated for sounds by placing the diaphragm of a stethoscope on it. The sounds undergo a series of changes in their quality and intensity. These sounds are known as Korotkow sounds.  Described by the Russian scientist Korotkow in 1905.  The sounds are heard in five different phases. Phase I : Sudden appearance of faint tapping sound which becomes gradually louder and clearer during the succeeding 10 mm Hg fall in pressure. Phase II : The sound becomes murmurish in the next 10 mm Hg fall in pressure. Phase III : The sound changes little in quality but becomes clearer and louder in next 15 mm Hg fall in pressure. Phase IV : Sounds become muffling in character during next 5 mm Hg fall. Phase Phase V : Sounds completely disappear.  Appearance of the sound is recorded as systolic blood pressure and disappearance of sound is recorded as diastolic blood pressure. PRINCIPLES OF DIFFERENT TYPES OF REGULATIONS IN THE BODY Dr. Thazin Shwe/ Hazel Desired Learning Outcome 1. List the different types of regulations in the body. 2. Comprehend the mechanisms of endocrine regulation and understand neural regulation. 3. Explain homeostatic regulation and apply principles of genetic regulation. 4. Identify immune system regulation and distinguish between autocrine, paracrine, and endocrine signaling. 5. Comprehend metabolic regulation and understand circadian rhythm regulation 6. Recognize the importance and integration of regulatory systems Outline 1. Importance of principles of different types of regulations in the body 2. Endocrine Regulation (Hormonal Regulation) 3. Neural Regulation 4. Homeostatic Regulation 5. Genetic Regulation 6. Immune Regulation 7. Autocrine and Paracrine Regulation 8. Metabolic Regulation 9. Circadian Rhythm Regulation Importance Maintaining Homeostasis Understanding Disease Mechanisms Foundation for Clinical Treatment Critical for Pharmacology and Drug Action Guiding Preventive Medicine Adapting to Environmental Changes Critical for Understanding Genetic and Developmental Disorders Enabling Personalized Medicine Supporting Advances in Medical Technology Improving Public Health and Epidemiology Endocrine Regulation (Hormonal Regulation) Principle The endocrine system uses hormones to regulate processes such as growth, metabolism, and reproduction. Hormones are secreted by glands and travel through the bloodstream to target organs or tissues. Endocrine Regulation (Hormonal Regulation) Examples Negative Feedback: Most hormones work through negative feedback loops, where the outcome of a process inhibits its own production (e.g., insulin regulation of blood glucose levels). Positive Feedback: In some cases, hormones promote their own production (e.g., oxytocin during childbirth). Negative Feedback Positive Feedback Neural Regulation Principle The nervous system regulates body functions through electrical signals (nerve impulses) transmitted by neurons. It allows for rapid responses to internal and external stimuli. Neural Regulation Examples Somatic motor reflex: Voluntary actions like pressing the brake pedal when you see a red light. Autonomic motor reflex: Controls involuntary functions like heart rate, digestion, and respiratory rate, involving sympathetic (fight-or-flight) and parasympathetic (rest-and- digest) systems. Homeostatic Regulation Principle The body maintains a stable internal environment despite external changes, a concept known as homeostasis. This regulation often involves feedback loops. Homeostatic Regulation Examples Thermoregulation: Body temperature is maintained through mechanisms like sweating, shivering, and blood vessel dilation or constriction. Osmoregulation: Water and electrolyte balance is regulated by kidneys, ADH (antidiuretic hormone), and aldosterone. Genetic Regulation Principle Gene expression is controlled by various genetic mechanisms that turn genes on or off depending on the needs of the cell or organism. Genetic Regulation Examples Transcriptional Control: Factors like enhancers or repressors can influence how much of a gene is transcribed into mRNA. Epigenetic Regulation: Modifications like DNA methylation or histone acetylation can influence gene expression without altering the DNA sequence itself. Reference Guyton, A. C., & Hall, J. E. (2011). Textbook of Medical Physiology. 12th ed., Saunders. Bear, M. F., Connors, B. W., & Paradiso, M. A. (2020). Neuroscience: Exploring the Brain. 4th ed., Wolters Kluwer. Sherwood, L. (2015). Human Physiology: From Cells to Systems. 9th ed., Cengage Learning. Alberts, B., et al. (2015). Molecular Biology of the Cell. 6th ed., Garland Science. Tutorial Questions 1. List the different types of regulations in the body. 2. What are the importance of regulating mechanisms in the body? 3. What types of physiological regulatory mechanisms are activated in response to a burning fire? 4. Provide a detailed explanation of the processes involved.  MBBS -YEAR 1 AUTONOMIC NERVOUS SYSTEM Desired Learning Outcomes ◼ On completion of this topic, you should be able to: 1. identify the divisions and subdivisions of the peripheral nervous system 2. list the functions of sympathetic and parasympathetic systems 3. compare and contrast the two subdivisions of ANS 4. list the higher control of ANS 5. outline the role of ANS and endocrines in stress responses ◼ Contents 1. Divisions of autonomic nervous system – sympathetic and parasympathetic 2. Functions of autonomic nervous system 3. Importance of ANS in maintenance of homeostasis 4. Control by higher centers  AUTONOMIC NERVOUS SYSTEM ◼ Definition: Part of the nervous system that controls most of the visceral functions: Eg: 1) Arterial blood pressure 2) G.I tract motility 3) G.I secretions 4) Sweating 5) Body Temperature ◼ All these functions are quick  CENTERS FOR ANS ◼ 1)Spinal cord ◼ 2) Brain stem ◼ 3)Hypothalamus ◼ 4) Limbic cortex ◼ ANS also operates by visceral reflexes AUTONOMIC NERVOUS SYSTEM ◼ Supplies & controls cardiac & smooth muscles, glandular cells, & special cells such as J.G. cells ◼ Maintains internal environment of the body, meeting it’s demands on minute- to-minute basis ◼ Involuntary in control ◼ Regulation mainly through reflexes  Autonomic Nervous System ◼ Two divisions - Sympathetic N.S, - Parasympathetic N.S. ◼ Two links- Preganglionic, postganglionic ◼ Sympathetic- short preganglionic fibers & long postganglionic fibers ◼ Parasympathetic- long preganglionic fibers & short postganglionic fibers  Autonomic outflow Sympathetic outflow Preganglionic Postganglionic Ach NE Parasympathetic outflow Postgan. Preganglionic Ach Ach  Autonomic outflow ◼ Parasympathetic-Cranio-sacral outflow III, VII, IX, X cranial nerves S 2,3,4 segments of spinal cord ◼ Sympathetic- Thoraco-lumbar outflow T1 – L2 segments of spinal cord ◼ Sympathetic & Sacral Parasympathetic neuron cell bodies in lateral horn of spinal cord  Sympathetic outflow ◼ Thoracolumbar outflow (T1-L2) ◼ Preganglionic axons short, leave the spinal cord through the ventral roots ◼ Axons pass via the white rami (myelinated) to the paravertebral sympathetic ganglion at the same segmental level ◼ Sympathetic chain extends from cervical to coccygeal level  Sympathetic outflow ◼ Most preganglionic neurons synapse on the cell bodies of postganglionic neurons in the sympathetic ganglia. ◼ Axons of the postganglionic neurons reenter the spinal nerves via the gray rami (nonmyelinated) ◼ Distributed to the autonomic effectors ◼ Each of the 31 pairs of spinal nerves has a gray ramus. ◼ Some preganglionic neurons end on postganglionic neurons of collateral or prevertebral ganglia ◼ Sympathetic chain forms the distributing system LHC White ramus Gray ramus Sympathetic ganglion  Effectors of the sympathetic nervous system ◼ Blood vessels ◼ Abdominal viscera, liver ◼ Piloerector muscles ◼ Pelvic organs ◼ Eccrine sweat glands ◼ Kidneys ◼ Heart ◼ Genitalia ◼ Lungs ◼ Salivary glands ◼ Bronchi ◼ Eye (Dilator pupillae) ◼ Adrenal medulla  Parasympathetic outflow I.Cranial outflow: Edinger Westphal nucleus (of III cranial nerve) Superior salivatory nucleus (of VII cranial nerve) Inferior salivatory nucleus (of IX cranial nerve) Dorsal motor nucleus and nucleus ambiguous (of X cranial nerve) II.Sacral outflow: ◼ Intermediolateral gray columns of S2, S3 and S4 segments  Parasympathetic outflow ◼ The parasympathetic ganglia near or within walls of the visceral organs. Ciliary ganglion of occulomotor (III cranial) nerve, behind the eyeball. The Pterigopalatine and Submandibular ganglion of facial (VII cranial) nerve. The Otic ganglion of glossopharyngeal (IX cranial) nerve The parasympathetic ganglia situated within the walls of thoracic, abdominal and pelvic viscera.  Effectors of the parasympathetic nervous system ❑ Sphincter pupillae and ciliary ❑ Liver,Pancreas and muscles of eyeball (III n) Gastrointestinal tract from ❑ Lacrimal gland (VII n). the esophagus to the splenic ❑ Salivary glands (VII & IX) flexure of the colon (Vagus) ❑ Remainder of the colon, ❑ Heart (X n) rectum, urinary bladder and ❑ Lungs (X n) reproductive organs ❑ Bronchi (X n) ( S 2, 3, 4) Constricts pupil  Parasympathetic Sympathetic Response Organ Response "Fight or Flight" "Rest and Digest" Heart Increased rate and strength of Decreased heart rate (baroreceptor contraction Cardiac output decreases reflex) Cardiac output increases Lung Bronchioles Constriction Dilation Glycogen breakdown Liver Glycogen No effect Blood glucose increases Breakdown of fat Adipose tissue No effect Blood fatty acids increase Basal No effect Increases Metabolism Increased secretion of HCl & Decreased secretion Stomach digestive enzymes Decreased motility Increased motility  Increased secretion of HCl & Decreased secretion Intestine digestive enzymes Decreased motility Increased motility Relaxes internal sphincter Constricts internal sphincter Urinary bladder Detrusor muscle contracts Relaxes detrusor Urination promoted Urination inhibited Relaxes sphincter Constricts sphincter Rectum Contracts wall muscles Relaxes wall muscles Defecation promoted Defecation inhibited Pupil constricts Pupil dilates Eye Adjusts for near vision Adjusts for far vision Male Sex Organs Promotes erection Promotes ejaculation  NEUROTRANSMITTERS IN ANS Sympathetic nervous system Parasympathetic n. system ◼ At the autonomic ganglia ◼ At the autonomic ganglia Acetylcholine Acetylcholine (Nicotinic receptors) (Nicotinic receptors) ◼ At the effector structures ◼ At the effector structures Norepinephrine (Adrenergic Acetylcholine receptors;  & ) (Muscarinic receptors)  Blockers of ANS neurotransmiiters Drugs that block -adrenergic receptors ◼Phentolamine, phenoxybenzamine, prazocin (1), yohimbine (2) Drugs that block -adrenergic receptors ◼Propranolol, atenolol , metaprolol, labetalol Drugs that block muscarinic cholinergic receptors ◼ Atropine, scopalamine Drugs that block autonomic ganglia (nicotinic receptors) ◼ Hexamethonium  AUTONOMIC CONTROL OF ORGAN SYSTEMS ◼ Most organs supplied by both the divisions of autonomic nervous system, ◼ This dual innervation results in reciprocal actions that precisely control visceral activity ◼ E g., when there is a need for decreased heart rate (in sleep), parasympathetic fibers to heart are activated to inhibit SA node & decrease heart rate. Sympathetic NS is inhibited However, some organs only receive sympathetic innervation: Spleen Sweat glands Piloerector muscles Most blood vessels AUTONOMIC CONTROL OF ORGAN SYSTEMS ◼ Most autonomic actions mediated through reflexes ◼ E.g., pupillary reflexes, GI activity, micturition, baroreceptor reflex, etc ◼ Sympathetic nervous system has diffuse actions (‘fight or flight response’ ) – ‘catabolic’ ◼ Parasympathetic nervous system regulates vegetative functions of the body (“Rest and Digest”)- ‘anabolic’  Higher control of ANS Hypothalamus is the main integration center of ANS activity. Posterior nucleus- sympathetic center Anterior nucleus –parasympathetic center Subconscious cerebral input via limbic lobe connections influences hypothalamic function Other controls come from the prefrontal lobe of cerebral cortex, & reticular formation.  A.1. The autonomic nervous system: is regulated by the Hypothalamus It regulates activities of : (1) Visceral muscles : which are involuntary , and include (a) cardiac muscle , and (b) smooth moscle in arterioles and the gastro-intesinal tract (GIT). (2) Glands ( e.g. , sweat glands and GIT glands ) It consists of 2 subdivisions: 11/14/2024 Figure 11-2 25  A.2 The autonomic nervous system pathways: The autonomic division consists of two efferent neurons in series Fig. 11-4 Tasrget tissue : effector Effector 11/14/2024 26  Higher control of autonomic function Sympathetic functions regulated by posterior hypothalamus Parasympathetic functions regulated by anterior hypothalamus 11/14/2024 27  The ANS has 2 subdivisions : sympathetic and parasympathetic 11/14/2024 28 Effect of sympathetic stimulation Sympathetic part of ANS is active during fear, anxiety, sever pain preparing the body for fight or flight Promoting mechanisms which increase energy & metabolism 11/14/2024 29  Effect of parasympathetic stimulation Parasympathetic system activities is related to relaxed state Vegetative function: – Feeding – Resting – Part of the sexual function 11/14/2024 30  Sympathetic (Thoracolumbar) System 1.The preganglionic fibers are short ( because most ganglia are paravertebral ) and postgang fibers are long. 2. Pregang fibers are myelinated and postgang fibers unmyelinated. 3.Pregang fibers secrete ACh in ganglia 4. The cholinergic receptor in ganglia is nicotinic 5.The neurotransmitter secreted by postgang fibers is Norepinephrine , except in sweat glands and blood vessels in skeletal muscle (in the latter cases it is ACh). 6.There is muchdivergence. The ratio (pre/post) being = 1/10 or more. This divergence implies simultaneous diffuse ( generalized ) actions. 11/14/2024 31  Parasympathetic (Craniosacral ) system : 1.The preganglionic neurons are long and postgang fibers are short ( because the parasympathetic ganglia are located either close to the arget organ or embedded in its wall. 2. Pregang fibers are myelinated and postgang fibers unmyelinated. 3.Pregang fibers secrete ACh in ganglia 4. The cholinergic receptor in ganglia is nicotinic 5.The neurotransmitter secreted by postgang fibers is ACh 6. The receptors on the target organ is cholinergic muscarinic ( can be blocked by Atropine ). 7.There is little divergence. The ratio (pre/post) = 1/3. The limited divergence results in more specific and selective actions. 11/14/2024 32  It should be noted that Under physiological conditions , nearly all sympathetic and parasympathetic activities are opposite ( contradictory ) to each other ; however , the two systems cooperate ( & may act in unison/accord ) in (1) salivary secretion ( sympathetic → scanty secretion rich in enzymes , parasympathetic → Watery , copious secretion ) , (2) Emotional stress : parasympathetic → increased tear and nasal secretions , sympathetic → increased heart- rate , BP , etc (3) Sexual intercourse : parasympathetic → erection of the penis or clitoris , sympathetic → ejaculation or orgasm 11/14/2024 33  Autonomic Neurotransmitter All preg. Fibres (sympathetic and parasympathetic ) secrete acetylcholine at the ganglia. All postganglionic parasympathetic fibers secrete acetylcholine at target organs. Most postganglionic sympathetic fibers secrete norepinephrine at target organs. Postganglionic sympathetic fibers to sweat gland & blood vessels of skeletal muscles release acetylcholine All epinephrine in the bloodstream comes from the adrenal medulla. Postganglionic sympathetic nerves can not synthesize epinephrine from its precursor which is norepinephrine. 11/14/2024 34 Further reading –Tutorial 1]Describe the autonomic reflexes integrated at the level of spinal cord. 2]Outline the functions of the autonomic nervous system 3]Describe the location of postganglionic sympathetic and parasympathetic neurons and the pathways they take to the visceral structures they innervate. 4] How does sympathetic discharge prepare the individual for flight of fight? Does the sympathetic nervous system have any other functions? 25  References 1.Dee Silverthorn. Human Physiology. 6 th ed. Pearson, 2013, Boston. 2.Guyton A C and Hall J E. Textbook of Medical physiology. 12th ed. W. B. Saunders & Co, 2008. Philadelphia. 3.Ganong W F. Review of Medical Physiology. 24th ed. Simon Schuster Asia Pvt. Ltd, 2012. Singapore. Biophysical Principles Dr.Jinu  Desired learning outcomes On completion of this topic, student should be able to: 1. Explain the concepts of biophysical principles like pressure, work, energy, viscosity, surface tension, in the different organs of the body for the maintenance of health. 2  What is biophysics Biophysics is a bridge between biology and physics. Biophysics is the scientific field that studies how biological systems work by applying the principles of physics to them. Applies the principle of physics- Heat of Vaporization  Work & Energy Work is done when the point of application of a force F moves through a certain distance D W= FxD Energy – Potential Energy : PE= mgh – Kinetic Energy : KE = ½ mv2  Potential energy Potential energy is the stored energy in an object due to its position, properties, and forces acting on it. Common types of potential energy include gravitational, elastic, magnetic, and electric. PE=mgh. m= the mass of the object, g=the gravitational acceleration constant h= the height above the ground  Kinetic energy Kinetic energy is the energy an object has because of its motion Kinetic energy is directly proportional to the mass of the object and to the square of its velocity: K.E. = 1/2 m v2. If the mass has units of kilograms and the velocity of meters per second. Application to physiology  Muscle and nerve function: Potential energy is converted into kinetic energy to power these functions Protein synthesis: Potential energy is converted into kinetic energy to drive the synthesis of body protein for growth Photosynthesis: Plants absorb photons, which have high kinetic energy, to excite electrons in chlorophyll molecules Movement: Kinetic energy is involved in moving atoms, ions, and molecules  ATP as energy source Adenosine triphosphate (ATP) is the source of energy for use and storage at the cellular level. ATP hydrolysis provides the energy needed for many essential processes in organisms and cells. These include intracellular signaling, DNA and RNA synthesis, synaptic signalling, active transport, and muscle contraction.  ATP = ADENOSINE - P - P~P ATP is hydrolyzed to ADP in the reaction ATP+H2O→ADP+Pi+ free energy; The calculated ∆G for the hydrolysis of 1 mole of ATP is - 57 kj/mol.  Surface tension Surface tension is the tendency of fluid surfaces to shrink into the minimum surface area possible. Intermolecular forces such as Van der Waals force, draw the liquid particles together. It therefore assumes a spherical shape because the surface to volume ratio is minimum for a sphere Application in physiology When water forms a surface with air, the water molecules on the surface of the water have an especially strong attraction for one another. As a result, the water surface is always attempting to contract. In alveoli, the water surface is also attempting to contract. This results in an attempt to force the air out of the alveoli through the bronchi and, in doing so, causes the alveoli to try to collapse  Surfactant is a surface-active agent in water, which means that it greatly reduces the surface tension of water It is secreted by special surfactant- secreting epithelial cells called type II alveolar epithelial cells, which constitute about 10 percent of the surface area of the alveoli.  Pressure = 2x Surface tension Radius of the alveolus For the average-sized alveolus with a radius of about 100 micrometers and lined with normal surfactant, this calculates to be about 4 centimeters of water pressure (3 mm Hg). If the alveoli were lined with pure water without any surfactant, the pressure would calculate to be about 18 centimeters of water pressure, 4.5 times as great.  Laplace’s Law States that: Distending pressure (P) in a hallow organ at equilibrium is equal to 2 times the tension ( T ) in the wall divided by radius (R). P = 2T / R or PR = 2T for hollow organs like stomach, urinary bladder, alveoli etc. P=T/R or PR = T in blood vessels (cylinder)  When the alveoli have half the normal radius (50 instead of 100 micrometers), the pressures noted earlier are doubled. Significance: This is especially significant in small premature babies, many of whom have alveoli with radii less than one quarter that of an adult person.  Infant respiratory distress syndrome (IRDS) Further, surfactant does not normally begin to be secreted into the alveoli until between the sixth and seventh months of gestation, and in some cases, even later than that. Therefore, many premature babies have a little or no surfactant in the alveoli when they are born, and their lungs have an extreme tendency to collapse. This causes the condition called respiratory distress syndrome of the Functions of pulmonary surfactant 1. Reduces the tendency of alveoli to collapse- Surfactant reduce surface tension and decreases the tendency to collapse. 2. Reduces work of breathing- According to the Laplace’s law, due to reduction in the surface tension, the mean alveolar radius is increased. This reduces the transmural pressure required for expanding the alveoli. As alveoli are easily expanded, so work of breathing is reduced.  3. Prevents pulmonary oedema- Surface tension is retracting force which not only pulls alveolar wall to the center of alveolus but also pulls fluid from the capillaries into the interstitial space surrounding the alveoli and into the alveoli leading to pulmonary oedema. Surfactant prevents this phenomenon by lowering the surface tension.  In the two alveoli (with unequal size) connected to each other Thus, when the surface tension is constant, the pressure developed in the smaller alveolus will be more than the larger alveolus. This will cause pushing of air from the smaller alveolus (with higher pressure) to the larger alveolus (with lower pressure). As a result, the smaller alveolar sac will become smaller and larger alveolar sac will become larger  Pulmonary surfactant causes alveolar stabilization In the smaller alveolus, the surfactant molecules form a thick layer while in a larger alveolus the surfactant molecules are scattered on the larger surface Pressure Force exerted per unit area. SI unit : – Newton/m2 : 1 Pascal [Pa] Significance in physiology Significance in physiology Oncotic pressure Hydrostatic pressure Significance in physiology  Blood pressure Blood pressure is defined as the lateral pressure exerted by the column of blood on the wall of arteries. Blood pressure means the arterial pressure. Blood Flow Blood flow means the quantity of blood that passes a given point in the circulation in a given period of time. Ordinarily, blood flow is expressed in milliliters per minute or liters per minute. The overall blood flow in the total circulation of an adult person at rest is about 5000 ml/min. This is called the cardiac output because it is the amount of blood pumped into the aorta by the heart each minute  Blood flow through a blood vessel is determined by two factors: (1) pressure difference of the blood between the two ends of the vessel, also sometimes called "pressure gradient" along the vessel, which is the force that pushes the blood through the vessel, and (2) The impediment to blood flow through the vessel, which is called vascular resistance. P1 represents the pressure at the origin of the vessel; at the other end, the pressure is P2 ΔP is the pressure difference (P1 - P2)  The difference in pressure between the two ends of the vessel, not the absolute pressure in the vessel, that determines rate of flow. For example, if the pressure at both ends of a vessel is 100 mm Hg and yet no difference exists between the two ends, there will be no flow despite the presence of 100 mm Hg pressure  Resistance occurs as a result of friction between the layers of the flowing blood and the intravascular endothelium all along the inside of the vessel. Flow through the vessel can be calculated by the following formula, which is called ohm's law : Blood flow = P R  High pressure system- control of systemic arterial pressure & distribution of blood flow Low pressure system – control of blood volume and venous return.  Windkesselvessels Aorta and large arteries like pulmonary artery Windkessel –German word -Elastic reservoir They have more elastic tissue in their wall Distensible-High compliance  During systole , their wall stretches to accommodate the ejected blood and during diastole, their wall recoils back- This recoiling effect is called Windkessel effect. Pushes the blood in forward direction during diastole.  Arteries are the distribution channels  Resistance vessels Arterioles, metarterioles – major seat of peripheral resistance  Arterioles Resistance is inversely proportional to the fourth power of radius of arterioles- (regulation) Resistance – impediment to the blood flow BF ∝ Pressure gradient BF ∝ 1/r4  VELOCITY – FLOW RELATIONSHIP The velocity of blood flow refers to the rate of linear displacement of blood within circulatory system per unit time. cm/s Determinates: Blood flow and cross- sectional area The velocity of blood flow (v) is inversely proportional to vascular cross-sectional area (A) Velocity= Blood flow/ cross sectional area  Aorta and Arteries Arterioles Capillaries  Velocity gradually decreases as blood flows from aorta through arteries and arterioles into capillaries due to progressive increase in cross sectional area V↓es Aorta capillaries Velocity gradually increases as blood passes from venules through veins into vena cava  APPLICATION OF LAPLACE’S LAW  Applies to all the hollow viscous structures in the body  In vascular system  In heart--When the radius of a cardiac chamber is increased, a greater tension must be developed in the myocardium to produce any given pressure; consequently, a dilated heart must do more work than a non- dilated heart T=P x r  Ventricular hypertrophy as the wall is thick, wall tension is less  Tutorial Questions 1. Discuss the relationship of pressure, flow and resistance in the blood vessels. 2. Explain the differences between the laminar flow and turbulent flow. 3. Define the critical velocity, explain the role of Reynolds number in related to turbulence flow. 4. Discuss the Poiseuille- Hegan’s law. 39 6.Give the relationship of total cross sectional area with velocity of blood flow. 7.Explain the Wind-kessel effect. 8.Discuss the principles of blood pressure measurements. 9.Explain how Korotkoff sounds are produced?  Lecture 1 Introduction To Physiology And Homeostasis DR RAZI  Desired Learning Outcomes:- 1. define homeostasis. 2. explain feedback mechanisms. 3. state examples of feedback mechanisms. 27 Introduction to Physiology Physiology is the study of the functions of living things. Focus on how the human body works. Physiology focuses on mechanisms of action. Two approaches are used to explain events that occur in the body; 1. purpose of a body process and 2. underlying mechanism by which this process occurs. Example: “Why do I shiver when I am cold?” Purpose: “to help my body warm up, because shivering generates heat.” Underlying mechanism: explanation of shivering is that when temperature-sensitive nerve cells detect a fall in body temperature, they signal the area in the brain responsible for temperature regulation. In response, this brain area activates nerve pathways that ultimately bring about involuntary, oscillating muscle contractions (that is, shivering). Structure and function are inseparable. Physiology is closely related to anatomy, the study of the structure of the body Some structure–function relationships are obvious. For example, the heart is well designed to receive and pump blood, the teeth to tear and grind food, and the hingelike elbow joint to permit bending of the arm. The respiratory airways, which carry air from the outside into the lungs, branch extensively when they reach the lungs. Tiny air sacs cluster at the ends of the huge number of airway branches. The branching is so extensive that the lungs contain about 300 million air sacs. Levels of Organization in the Body The chemical level: Various atoms and molecules make up the body The cellular level: Cells are the basic units of life. The tissue level: Tissues are groups of cells of similar specialization. The organ level: An organ is a unit made up of several tissue types. The body system level: A body system is a collection of related organs. The organism level: The body systems are packaged into a functional whole body Four primary types: muscle, nervous, epithelial, and connective  Concept of Homeostasis The external environment is the surrounding environment in which an organism lives. The internal environment is the fluid that surrounds the cells and through which they make life-sustaining exchanges. The fluid collectively contained within all body cells is called intracellular fluid (ICF). The fluid outside the cells is called extracellular fluid (ECF). ECF is made up of two components: the plasma, the fluid portion of the blood, and the interstitial fluid, which surrounds and bathes the cells (inter means “between”; stitial means “that which stands”) Homeostasis Homeostasis (homeo means “similar”; stasis means “to stand or stay”) is termed maintenance of a relatively stable internal environment. Homeostasis is essential for the survival of each cell, and each cell, through its specialized activities as part of a body system, helps maintain the internal environment shared by all cells. The 11 body systems contribute to homeostasis Homeostatically Regulated Factors Factors of the internal environment must be homeostatically maintained: 1. Concentration of nutrients. 2. Concentration of O2 and CO2. 3. Concentration of waste products. 4. pH. 5. Concentrations of water, salt, and other electrolytes. 6. Volume and pressure. 7. Temperature. Homeostatic Control Systems To maintain homeostasis, the control system must be able to : (1) detect deviations from normal in the internal environmental factor that needs to be held within narrow limits; (receptor/sensor) (2) integrate this information with any other relevant information; (Integrating center) and (3) make appropriate adjustments in the activity of the body parts responsible for restoring this factor to its desired value; (Effector) Homeostatic control systems may operate : locally(intrinsic) or bodywide/extrinsic (systemic) Extrinsic control of the organs and body systems is accomplished by the nervous and endocrine systems, Control systems 1. Negative feedback opposes an initial change and is widely used to maintain homeostasis control of body temperature 2. Positive feedback amplifies an initial change. In the birth of a baby. The hormone oxytocin causes powerful contractions of the uterus (womb). As the contractions push the baby against the cervix (the exit from the uterus), the resultant stretching of the cervix triggers a sequence of events that brings about the release of even more oxytocin, which causes even stronger uterine contractions, triggering the release of more oxytocin, and so on. This positive- feedback cycle does not stop until the cervix is stretched sufficiently for the baby to be pushed through and born 3. Feedforward mechanisms initiate responses in anticipation of a change. For example, when a meal is still in the digestive tract, a feedforward mechanism increases secretion of a hormone (insulin) that promotes the cellular uptake and storage of ingested nutrients after they have been absorbed from the digestive tract. This anticipatory response helps limit the rise in blood nutrient concentration after nutrients have been absorbed. Positive feedback Disruptions in homeostasis can lead to illness and death. The term pathophysiology refers to the abnormal functioning of the body (altered physiology) associated with disease. Many diagnostic tests rely heavily on principles learned by physiologists; examples include the electrocardiogram and lung function tests. Treatments for a number of pathophysiological conditions, such as high blood pressure, diabetes mellitus, and erectile dysfunction, are likewise based on knowledge acquired through physiological research. Thus physiology is at the heart of clinical practice.  Tutorial Questions 1. List and describe the levels of organization in the body. 2. Name the four primary types of tissue and give an example of each. 3. Distinguish among external environment, internal environment, intracellular fluid, extracellular fluid, plasma, and interstitial fluid. 4. Define homeostasis 5. Compare negative feedback and positive feedback. 6. Body temperature is homeostatically regulated around a set point. Given your knowledge of negative feedback and homeostatic control systems, predict whether narrowing or widening of the blood vessels of the skin will occur when a person exercises strenuously. (Hints: Muscle contraction generates heat. Narrowing of the vessels supplying an organ decreases blood flow through the organ, whereas vessel widening increases blood flow through the organ. The more warm blood flowing through the skin, the greater is the loss of heat from the skin to the surrounding environment.) Thank you  Lecture Nerves Physiology DR RAZI  Desired Learning Outcomes:- 1. Classify nerves and state their functions. 2. State the functions of neurons and neuroglia. 3. Briefly state the process of nerve injury and regeneration of nerves. 27 Nervous system The nervous system is one of the two major regulatory systems of the body; the other is the endocrine system. The three basic functional types of neurons: 1. afferent neurons, 2. efferent neurons, and 3. interneurons In general, the nervous system acts by means of its electrical signals (action potentials) and neurotransmitter release to control the rapid responses of the body Organization of the nervous system Sensory, motor and interneurons  THE NEURON: Basic Working Unit Of The Nervous System Functions of Myelin Sheath Support the neuron Insulator Rapid conduction of nerve signals Myelinated neuron Unmyelinated neuron CNS In Multiple sclerosis (MS), patchy destruction of myelin occurs in the CNS. The loss of myelin is associated with delayed or blocked conduction in the demyelinated axons. In MS, antibodies and white blood cells in the immune system attack myelin, causing inflammation and injury to the sheath and eventually the nerves that it surrounds. Loss of myelin leads to leakage of K+ through voltage-gated channels, hyperpolarization, and failure to conduct action potentials. Initial presentation commonly includes reports of paraparesis (weakness in lower extremities) that may be accompanied by mild spasticity and hyperreflexia; paresthesia; numbness; urinary incontinence; and heat intolerance. Clinical assessment often reports optic neuritis, characterized by blurred vision, a change in color perception, visual field defect (central scotoma), and pain with eye movements; dysarthria; and dysphagia. PNS Myelin protein zero (P0) and a hydrophobic protein PMP22 are components of the myelin sheath in the peripheral nervous system. Autoimmune reactions to these proteins cause Guillain–Barré syndrome, a peripheral demyelinating neuropathy. Mutations in myelin protein genes cause peripheral neuropathies that disrupt myelin and cause axonal degeneration (eg, Charcot- Marie-Tooth disease)  IMPULS CONDUCTION & SPEED OF IMPULS Once initiated, the velocity, or speed, with which an action potential travels down the axon depends on two factors: 1) whether the fiber is myelinated or not Contiguous conduction : occurs in unmyelinated fibers. Saltatory conduction : occurs in myelinated fibers. 2) the diameter of the fiber When fiber diameter increases, the resistance to local current decreases. Thus, the larger the fiber diameter, the faster action potentials can be propagated. Large myelinated fibers, such as those supplying skeletal muscles, can conduct action potentials at a velocity of up to 120 meters/second (268 miles/hour), compared with a conduction velocity of 0.7 meters/second (2 miles/hour) in small unmyelinated fibers such as those supplying the digestive tract. 9  1. NEURONS (NERVE CELLS) - TRANSMIT MESSAGE Anatomy: Cell body – contains nucleus; metabolic center Dendrite – fiber that conveys messages toward cell body Axon – conduct nerve impulses away from the cell body Axon terminals – end of axon; contain neurotransmitters & release them Synaptic cleft/synapse – gap between neurons  Myelin: whitish, fatty material that covers nerve fibers to speed up nerve impulses Schwann cells: surround axons and form myelin sheath Myelin sheath: tight coil of wrapped membranes Nodes of Ranvier: gaps between Schwann cells Ganglia: collections of cell bodies Bundles of nerve fibers = tracts (CNS) or nerves (PNS) White matter: dense collections of myelinated fibers Gray matter: unmyelinated fibers & cell bodies Types of neurons in the mammalian nervous system. NERVE FIBER TYPES & FUNCTION Letter classification Mammalian nerve fibers are divided into A, B, and C groups, and the A group can be subdivided into α, β, γ, and δ fibers.  Numerical system Although the letter classification is commonly used to describe motor fibers, a numerical system (Ia, Ib, II, III, and IV) is often used to classify sensory fibers based on their axonal diameter and conduction velocity. Clinical/Physiologic significance of nerve type Peripheral nerves differ in their sensitivity to hypoxia and anesthetics. Local anesthetics depress transmission in the pain sensation in unmyelinated group C fibers before they affect the myelinated group A fibers. Conversely, pressure on a nerve can cause loss of conduction in large- diameter motor, touch, and pressure fibers while pain sensation remains relatively intact. Eg : individuals who sleep with their arms under their heads for long periods, causing compression of the nerves in the arms. Alcoholic intoxication, the syndrome is most common on weekends and has acquired the interesting name Saturday night or Sunday morning paralysis. AXONAL TRANSPORT Axonal transport along microtubules by dynein and kinesin. Fast (400 mm/day) and slow (0.5– 10 mm/day) axonal orthograde transport occurs along microtubules that run along the length of the axon from the cell body to the terminal. Retrograde transport (200 mm/day) occurs from the terminal to the cell body. Glial cells/ neuroglia There are four major types of glial cells (supporting cells) in the CNS : astrocytes oligodendrocytes microglia ependymal cells *each with specific roles  Functions of different CNS Glial cells Astrocytes Forms almost half of the CNS cells Have many roles because of its connections to synapses There are gap junction in between the astrocytes making a network of communication Functions: a. Help to form Blood brain barrier (BBB). b. Take up K+, water and neurotransmitters. c. Secrete neurotrophic factors. d. Provide substrate for ATP production. e. clearing toxic metabolic byproducts from the brain by means of the glymphatic system, a glia substitute for the lymphatic system (hence, this system is dubbed “glymphatic.”) Oligodendrocytes form the insulative myelin sheaths around axons in the CNS. An oligodendrocyte has several elongated projections, each of which wraps jelly-roll fashion around a section of an interneuronal axon to form a patch of myelin The function is just like Schwann cell in PNS Microglia cells (Immune cells) They are scavenger cells similar to monocytes When trouble occurs in the CNS, microglia retract their branches, round up, and become highly mobile and move toward the affected area to remove any foreign invaders or tissue debris by phagocytosis. Activated microglia also release destructive chemicals for assault against their target. Microglia are the only CNS cell type that can be infected by HIV, the virus that causes AIDS. Ependymal cells Beating of ependymal cilia contributes to the flow of cerebrospinal fluid through the ventricles They are source of neural stem cells [immature cells that can differentiate into neurons and Glial cells] Neurons in the rest of the brain are considered irreplaceable. But the discovery of ependymal cells as a reservoir of precursors for new neurons suggests that the adult brain has more potential for repairing damaged regions than previously assumed.  Neuroglia vs. Neurons ▪ Neuroglia divide. ▪ Neurons do not divide. ▪ Most brain tumors are “gliomas.” ▪ Most brain tumors involve the neuroglia cells, not the neurons. ▪ Glial cells communicate with each other and with neurons through chemical signals. AXONAL INJURY/DEGENARATION Changes occurring in a neuron when its axon is crushed or injured. The distal axon stump separates from the cell body, orthograde (Wallerian) degeneration occurs from the point of damage to the terminal, and the myelin sheath degenerates. The cell body of the injured neuron swells and the endoplasmic reticulum is fragmented as part of the chromatolytic reaction.  Recovery of the cell body ▪ It may take several months. ▪ RNA & protein synthesis is accelerated. ▪ Reconstitution of the original Nissl structure ▪ Appearance of Golgi apparatus followed by other organelles. ▪ The cell loses the excess water and swelling decreases. ▪ Return of nucleus to its characteristic central position  Axonal Regeneration in PNS Peripheral nerve damage is often reversible. Although the axon will degenerate distal to the damage, connective elements of the so-called distal stump often survive. Axonal sprouting occurs from the proximal stump, growing toward the nerve ending. This results from growth-promoting factors secreted by Schwann cells that attract axons toward the distal stump. The nerve then starts to regrow, with multiple small branches projecting along the path the axon previously followed (regenerative sprouting). Axons sometimes grow back to their original targets, especially in locations like the neuromuscular junction. Regeneration of the peripheral nerves Regeneration means regrowth of lost or destroyed part of a tissue. Nerves when injured can regenerate. Regeneration starts after 4 days from injury, becomes effective after 30 days and complete in 80 days. For regeneration to occur, some criteria should be there: 1. The size of the gap between the cut ends < 3mm. 2. Neurolemma “sheath of Schwann cells” is present [It is absent in CNS, so regeneration is not possible] 3. Intact Nucleus 4. The two cut ends remain at the same line - If regeneration does not occur, the axon & the Schwann cells are replaced by fibrous tissue produced by localfibroblasts. Axonal Regeneration in CNS The proximal stump of a damaged axon in the CNS will form short sprouts, but distant stump recovery is rare, and the damaged axons are unlikely to form new synapses. This is in part because CNS neurons do not have the growth- promoting chemicals needed for regeneration  Tutorial Questions 1. Classify nerves and state their functions 2. State the functions of neurons and neuroglia cells 3. Discuss about nerve injury. 4. Describe the process of regeneration of the nerves 5. State the importance of the myelin sheath Thank you  MBBS -YEAR 1 AUTONOMIC NERVOUS SYSTEM-II PHYSIOLOGY OF THE ANS  Desired Learning Outcomes On completion of this topic, you should be able to: 1. identify the divisions and subdivisions of the peripheral nervous system 2. list the functions of sympathetic and parasympathetic systems 3. compare and contrast the two subdivisions of ANS 4. list the higher control of ANS 5. outline the role of ANS and endocrines in stress responses 6. Describe the major responses of the body to stimulation by the sympathetic and parasympathetic divisions of the ANS. Contents 1. Divisions of autonomic nervous system – sympathetic and parasympathetic 2. Functions of autonomic nervous system 3. Importance of ANS in maintenance of homeostasis 4. Control by higher centers 5. ANS and endocrines in stress responses in the body ANS- Response(Summary from ANS-I)  Autonomic Tone Most body organs receive innervation from both divisions of the ANS, which typically work in opposition to one another. The balance between sympathetic and parasympathetic activity, called autonomic tone, is regulated by the hypothalamus. Typically, the hypothalamus turns up sympathetic tone at the same time it turns down parasympathetic tone, and vice versa. BUT , The two divisions can affect body organs differently because their postganglionic neurons release different neurotransmitters and because the effector organs possess different adrenergic and cholinergic receptors.  ANS Supply-Exception A few structures receive only sympathetic innervation—sweat glands, arrector pili muscles attached to hair follicles in the skin, the kidneys, the spleen, most blood vessels, and the adrenal medullae. In these structures there is no opposition from the parasympathetic division. Still, an increase in sympathetic tone has one effect, and a decrease in sympathetic tone produces the opposite effect.  Sympathetic Responses During physical or emotional stress, the sympathetic division dominates the parasympathetic division. High sympathetic tone favors body functions that can support vigorous physical activity and rapid production of ATP. At the same time, the sympathetic division reduces body functions that favor the storage of energy.  Sympathetic Responses (Contn) Besides physical exertion, various emotions—such as fear, embarrassment, or rage—stimulate the sympathetic division. Visualizing body changes that occur during “E situations” such as exercise, emergency, excitement, and embarrassment will help you remember most of the sympathetic responses. Activation of the sympathetic division and release of hormones by the adrenal medullae set in motion a series of physiological responses collectively called the fight-or- flight response.(Response discussed in ANS-I) The effects of sympathetic stimulation are longer lasting and more widespread than the effects of parasympathetic stimulation  Sympathetic Responses (Contn) for three reasons: (1)Sympathetic postganglionic axons diverge more extensively; as a result, many tissues are activated simultaneously. (2)Acetylcholinesterase quickly inactivates acetylcholine, but norepinephrine lingers in the synaptic cleft for a longer period. (3)Epinephrine and norepinephrine secreted into the blood from the adrenal medulla intensify and prolong the responses caused by NE liberated from sympathetic postganglionic axons.  Parasympathetic Responses In contrast to the fight-or-flight activities of the sympathetic division, the parasympathetic division enhances rest and digest activities. Parasympathetic responses support body functions that conserve and restore body energy during times of rest and recovery. In the quiet intervals between periods of exercise, parasympathetic impulses to the digestive glands and the smooth muscle of the gastrointestinal tract predominate over sympathetic impulses. This allows energy-supplying food to be digested and absorbed. At the same time, parasympathetic responses reduce body functions that support physical activity.  Parasympathetic Responses (Contn) other important parasympathetic responses are “three decreases”: decreased heart rate, decreased diameter of airways (bronchoconstriction), and decreased diameter (constriction) of the pupils.  Autonomic Reflexes Autonomic reflexes are responses that occur when nerve impulses pass through an autonomic reflex arc. These reflexes play a key role in regulating controlled conditions in the body, such as blood pressure, by adjusting heart rate, force of ventricular contraction, and blood vessel diameter; digestion, by adjusting the motility (movement) and muscle tone of the gastrointestinal tract; and defecation and urination, by regulating the opening and closing of sphincters.  The components of an autonomic reflex arc are as follows: Receptor :Like the receptor in a somatic reflex arc ,the receptor in an autonomic reflex arc is the distal end of a sensory neuron, which responds to a stimulus and produces a change that will ultimately trigger nerve impulses. Autonomic sensory receptors are mostly associated with interoceptors. Sensory neuron. Conducts nerve impulses from receptors to the CNS.  Integrating center. Interneurons within the CNS relay signals from sensory neurons to motor neurons. The main integrating centers for most autonomic reflexes are located in the hypothalamus and brain stem. Some autonomic reflexes, such as those for urination and defecation, have integrating centers in the spinal cord.  Motor neurons. Nerve impulses triggered by the integrating center propagate out of the CNS along motor neurons to an effector. In an autonomic reflex arc, two motor neurons connect the CNS to an effector: The preganglionic neuron conducts motor impulses from the CNS to an autonomic ganglion, and the postganglionic neuron conducts motor impulses from an autonomic ganglion to an effector. Effector :In an autonomic reflex arc, the effectors are smooth muscle, cardiac muscle, and glands, and the reflex is called an autonomic reflex. Autonomic Control by Higher Centers Normally, we are not aware of muscular contractions of our digestive organs, our heartbeat, changes in the diameter of our blood vessels, and pupil dilation and constriction because the integrating centers for these autonomic responses are in the spinal cord or the lower regions of the brain. Somatic or autonomic sensory neurons deliver input to these centers, and autonomic motor neurons provide output that adjusts activity in the visceral effector, usually without our conscious perception. Organization: Sympathetic NS  Sympathetic Nervous System Also calledThoracolumbar system All preganglionic sympathetic fibers Arises from lateral horn of spinal cord Leave the spinal cord with the ventral roots of the spinal nerve Cell body located in gray matter from T1-L2 Sympathetic trunk extend the entire length of spinal cord Post ganglionic fibers pass to effector organ Sympathetic Nervous System All preganglionic sympathetic fibers- Arises from lateral horn of spinal cord Leave the spinal cord with the ventral roots of the spinal nerve Cell body located in gray matter from T1-L2 Sympathetic Nervous System All preganglionic sympathetic fibers are: Short Myelinated Type B fiber Leave the spinal cord via ventral root Pass via the white rami communicates to the paravertebral ganglia Terminates in sympathetic ganglia Synapses with postganglionic neurons Sympathetic Nervous System Destination of the preganglionic fibers after reaching the sympathetic trunk Preganglionic fibres after reaching the sympathetic trunk may- 1. Terminate in the same ganglia that it enters 2. Pass upward & terminate in the other ganglia 3. Pass downward & terminate in the other ganglia 4. Leave the sympathetic trunk without synapsing & terminate in other ganglia which lies out side the sympathetic trunk Sympathetic Ganglia Ganglia: Structures where synapsing between pre and post ganglionic fibers occurs One preganglionic fiber synapses with several post ganglionic neurons Important groups of sympathetic ganglia are- 1. Sympathetic trunk (Paravertebral ganglia) 2. Prevertebral ganglia 3. Peripheral ganglia Sympathetic Trunk Ganglia Postganglionic Sympathetic Neuron All Postganglionic Sympathetic Neuron arises from sympathetic ganglia Cell body located in ganglion These are - Short & Nonmyelinated Type C fibers Postganglionic Sympathetic Neuron Postganglionic Sympathetic Fibers may- Pass through gray ramus communicantes and re-enter ventral root to reach a spinal nerve and innervate the- Sweat gland Blood vessels Piloerector muscle Postganglionic Sympathetic Neuron Postganglionic Sympathetic Fibers may- 1. Pass through gray ramus communicantes and re- enter ventral root to reach a spinal nerve 2. Reach a cranial nerve through communicating branch & distributed through it 3. Pass into a vascular branch and distributed to branches of vessels 4. Innervate the visceral organs  Distribution of Sympathetic neurons Segmental level Area of distribution 1. T1,T2 Head & Neck 2. T3,T4 Thoracic viscera 3. T5 toT9 Upper limb 4. T10 to L2 Lower Limb 5. T6 toT12 Upper Abdominal Viscera 6. L1,L2 Lower Abdominal Viscera 7. T1toT12 Thoracic & abdominal Vessels  Effect of Sympathetic stimulation Effects System/organ CVS Cardiac stimulation Heart SAN +ve Chronotropic Effect AVN +ve Dromotropic Effect Purkinje Fibers +ve Bathmotropic Effect Myocardium Blood Vessels +ve Inotropic Effect Vasoconstriction – Splanchnic Cutaneous Vasodilatation-skeletal blood vessels  Effect of Sympathetic stimulation System/organ Effects CVS Cardiac stimulation HR Increases SV Increases CO Increases SBP Increases DBP Increases PVR Increases  Effect of Sympathetic stimulation System/organ Effects Respiratory Bronchodilatation Tachypnea GIT Relaxation of smooth muscle Constriction of sphincters CNS Increased alertness Loss of sleep Genitourinary Relaxation of detruser Constriction of sphincters Ejaculation in male Sympathetic responses  Further reading –Tutorial 1] Define autonomic tone. 2] What are some examples of the antagonistic effects of the sympathetic and parasympathetic divisions of the autonomic nervous system? 3] Why is the parasympathetic division of the ANS called an energy conservation/restoration system? 4] How does an autonomic reflex arc differ from a somatic reflex arc? 20  References 1.Dee Silverthorn. Human Physiology. 6 th ed. Pearson, 2013, Boston. 2.Guyton A C and Hall J E. Textbook of Medical physiology. 12th ed. W. B. Saunders & Co, 2008. Philadelphia. 3.Ganong W F. Review of Medical Physiology. 24th ed. Simon Schuster Asia Pvt. Ltd, 2012. Singapore. Lecture 3 - Cell Volume and Cell Signaling - maintenance & importance in health MBBS (YEAR 1) DR. ROS