Human Physiology Introduction PDF

INTRODUCTION TO HUMAN PHYSIOLOGY Dr/ Enas Nassar  INTRODUCTION Physiology is the study Of the biological functions of Organs and their Interrelationships. INTRODUCTION To accomplish this goal, We will use the Many levels of Organization Of the human body.  INT...

INTRODUCTION TO HUMAN PHYSIOLOGY Dr/ Enas Nassar  INTRODUCTION Physiology is the study Of the biological functions of Organs and their Interrelationships. INTRODUCTION To accomplish this goal, We will use the Many levels of Organization Of the human body.  INTRODUCTION The internal environment Remains remarkably constant Despite changing conditions In the external environment.  – Interior of body separated from external environment by a layer of epithelial tissue – Lumen of respiratory system, gastrointestinal system, and urinary system are part of external environment The Body’s External Environment  The Body’s Internal Environment Internal environment = fluid surrounding cells  Body Fluid – Internal environment = fluid surrounding cells = extracellular fluid (ECF) – 70 kg man -Total body water = 42 liters 28 liters intracellular fluid (ICF) 14 liters extracellular fluid (ECF) -3 liters plasma -11 liters interstitial fluid (ISF) Body Fluid Compartments Figure 1.5  Intracellular Fluid (ICF) comprises 2/3 of the body's water. If your body has 60% of its weight water, ICF is about 40% of your weight. The ICF is primarily a solution of potassium and organic anions, proteins etc. (Cellular Soup!). The cell membranes and cellular metabolism control the constituents of this ICF. ICF is not homogeneous in your body. It represents a conglomeration of fluids from all the different cells. Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings.  Extracellular Fluid (ECF) is the remaining 1/3 of your body's water. ECF is about 20% of your weight. The ECF is primarily a NaCl and NaHCO3 solution. The ECF is further subdivided into three sub compartments: Interstitial Fluid (ISF) surrounds the cells, but does not circulate. It comprises about 3/4 of the ECF. Plasma circulates as the extracellular component of blood. It makes up about 1/4 of the ECF. Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings.  Transcellular fluid is a set of fluids that are outside of the normal compartments. These 1-2 liters of fluid make up the CSF, Digestive Juices, Mucus, etc. Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings.  Variation due to Age Neonates contain more water then adults: 75-80% water with proportionately more extracellular fluid (ECF) then adults. At birth, the amount of interstitial fluid is proportionally three times larger than in an adult. By the age of 12 months, this has decreased to 60% which is the adult value. Total body water as a percentage of total body weight decreases progressively with increasing age. By the age of 60 years, total body water (TBW) has decreased to only 50% of total body weight in males mostly due to an increase in adipose tissue. Inc., Copyright © 2005 Pearson Education, publishing as Benjamin Cummings.  There are balance between the fluid input and output: Daily Intake and Output of Water (ml/day) Input Fluids ingested 2100 From metabolism 200 -------------------------------------------------------------------------------------- Total intake 2300 Output Insensible—skin 350 Insensible—lungs 350 Sweat 100 Feces 100 Urine 1400 ------------------------------------------------------------------------------------- Total output 2300  Composition Plasma Water Plasma, (mEq/L) Interstitial Fluid Intracellular Electrolyte (mEq/L) [molarity] (mEq/L) Fluid (mEq/L) [molality] Cations: 142 153 145 10 Sodium Potassium 4 4.3 4 160 Calcium 5 5.4 5 2 Magnesium 2 2.2 2 26 Total Captions: 153 165 165 198 Anions: Chloride 101 108.5 114 3 Bicarbonate 27 29 31 10 Phosphate 2 2.2 2 100 Sulphate 1 1 1 20 Organic Acid 6 6.5 7 Protein 16 17 1 65 Total Anions: 153 165 156 198 Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings. INORGANIC COMPOUNDS Water is the most abundant And important inorganic Compound in living Materials. It makes up 60 to 80% of the volume of most Living cells.  SALTS A salt is an ionic compound Containing cations other Than h+ and anions other Than the hydroxyl ion _ (Oh ). when salts are dissolved In water, they dissociate into Their component ions.  SALTS Salts commonly found in The body include: Nacl, Ca2Co3 , kcl, Ca3(po4)2. OTHER IONS WHICH ARE Important in the body include: Fe, I, mg, zn.  ACIDS An acid is a substance That releases hydrogen Ions in detectable amounts. Because a hydrogen ion is just A hydrogen nucleus, acids Are also defined as a proton Donors.  ACIDS Acids commonly found In the body include: Hcl, H2CO3. Acids Can be strong or weak Depending on the amount of Hydrogen ions liberated.  BASES A base is a substance Which dissociates Liberating hydroxyl ions _ (Oh ). Bases remove H+ ions from solution and Are often called a proton Acceptor.  BASES Bases commonly found In the body include: Naoh, and ammonia nh3.  pH The h+ concentration of A solution IS USUALLY INDICATED IN ph UNITS ON A Ph SCALE THAT RUNS FROM 0 to 14. THE ph VALUE IS EQUAL To the log of 1 over the H+ concentration.  pH pH = - log [H+] WHERE [H+] = MOLAR H+ CONCENTRATION  pH ACIDIC SOLUTION HAVE A pH OF LESS THAN 7, BASIC SOLUTION HAVE A pH OF GREATER THAN 7. A SOLUTION WITH A pH OF 7 IS NEUTRAL.e.g. water pH  Sources of H+ in the body: 1-Oxidation of carbon in organic food substances CO2 which dissolves in fluids H2CO3 H+ + HCO3- (in normal adult 300 Lit. CO2 & 13.000 mEq of H+ ion resulted per day). 2-Oxidation of sulphur & phosphorus in the proteins and lipids thus a high protein diet can produce acidosis in the body. 3- Ingestion of acids as lemon or acidifying salts as NH4Cl.  Sources of H+ in the body: 4-Anerobic glycolysis in muscle which occurs in prolonged muscle contraction or starvation leads to lactic acid accumulation. 5-Hydrolysis of high-energy phosphate bond of ATP or CP.  Body defensive mechanisms against pH disturbances The body metabolism and muscle activities tend to add acids to the body fluids, hence we have an alkaline reserve in our body to oppose this tendency  Body defensive mechanisms against pH disturbances maintenance of this pH depends on: [A] Chemical buffers: (very rapid – in fraction of a second) [B] Respiratory regulation of the pH. (1-12 minute) [C] Renal regulation of pH II. Homeostasis: A Central Organizing Principle of Physiology Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings.  [A] Chemical buffers: (very rapid – in fraction of a second) By substances which minimize changes in pH of solution when acids or bases are added. E.g. 1- Bicarbonate – carbonic acid system When strong acid (HCL) is added to plasma, it will combine with Na HCO3 NaCL (neutral) + H2Co3 (weak acid). When strong base (NaOH) is added to plasma, it will combine with H2CO3 NaHCO3 (weak base) + H2O. - Yet, bicarbonate buffer is actually more important than all the other body.  [A] Chemical buffers: 2- Phosphate system: (H2PO4 and HPO4) 3- Protein buffer system: e.g. plasma protein Haemoglobin Intracellular protein [B] Respiratory regulation of the pH. Respiratory system controls pH of body fluids by controlling CO2 tension in the arterial blood, which is the main source of H+ ions. - If rate of removal of CO2 from alveoli is less than rate of CO2 production by cells (as occurs in hypoventilation) CO2 content in blood will be increased leading to respiratory acidosis as occurs in cases of respiratory center depression. - If the reverse occurs e.g., in hyperventilation respiratory alkalosis occurs (e.g., in hysterical dyspnoea).  While in metabolic acidosis, there will be hyperventilation resulting from stimulating effect of excess H- on respiratory center. This hyperventilation will cause more wash of CO2 from blood to correct this condition. - The reverse occurs in metabolic alkalosis, where the decreased amount of H- will lead to hypoventilation that will help in increasing CO2 content of blood to correct the condition. So the respiratory system acts as feed-back regulatory system for control of pH. as 2 times powerful than all chemical buffers.  [C] Renal regulation of pH It is the final and most important defense in H+ ion homeostasis. It is able to correct the pH completely but with delay effect in hours to days. Mechanisms: 1- Excretion of H+ and conservation of HCO3 2- Excretion of acids or alkalies: In diabetes mellitus, the kidney excretes ketoacids. In alkalosis the kidney excretes NaHCO3  Homeostasis Process of maintaining stable internal environment compatible for life – Most organ systems contribute to homeostasis Negative Feedback Control in Homeostasis – Primary mechanism for maintaining homeostasis – External change  triggers change in regulated variable in internal environment  triggers reaction to oppose the change and return regulated variable toward normal (set point)  Negative Feedback Mechanisms – Set point = desired level of regulated variable – Sensors detect level of regulated variable and provide input to integrating center – Integrating center compares set point to actual level of regulated variable – Error signal = difference between actual level and set point – Integrating center sends output to effectors to return regulated variable toward set point Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings. NEGATIVE FEEDBACK NEGATIVE FEEDBACK  Thermoregulation – Homeothermic animals – regulate body temperature within a narrow range – Poikilothermic animals – do not regulate body temperature Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings.  Homeothermic Animals – Normal body temperature = set point Differs in animal species Humans: 37oC (98.6oF) – Hypothermia = decrease in body temperature – Hyperthermia = increase in body temperature above 41oC, dangerous above 43oC, deadly Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings. Mechanisms of Heat Transfer Between Body and External Environment – Radiation - thermal energy as electromagnetic waves – Conduction - thermal energy through contact – Evaporation - heat loss through evaporation of water insensible water loss sweating – Convection - heat transfer by movement of fluid or air Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings. Components of Thermoregulatory System – Thermoregulatory system maintains core body temperature – Detectors - thermoreceptors (central and peripheral) – Integrator - hypothalamus – Effectors - sweat glands, blood vessels in skin, skeletal muscles  Thermoneutral Zone Range of outside temperature where alterations in blood flow alone regulates body temperature 25-30oC – Body temperature increase: blood flow to skin increases – Body temperature decrease: blood flow to skin decreases Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings. Negative Feedback Control of Body Temperature Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings. Figure 1.9a, b Thermoregulation Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings. Figure 1.9c  Fever – Fever accompanies infections – White blood cells secrete pyrogens – Body temperature set point increases – Fever enhances immune response Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings.  POSITIVE FEEDBACK A REGULATORY MECHANISM IN WHICH THE RESPONSE TO A STIMULUS, IN A CONTROL SYSTEM, CAUSES THE CONTROLLED VARIABLE TO MOVE FARTHER FROM THE SET POINT.  POSITIVE FEEDBACK POSITIVE FEEDBACK USUALLY DOES NOT MAINTAIN HOMEOSTASIS. IT IS CHARACTERIZES BY BEING SHORT IN DURATION, AND INFREQUENT. POSITIVE FEEDBACK Positive Feedback Loop Positive feedback loops cause a rapid change in a variable.