Paramedicine – Medical Physiology II Past Paper PDF W2025

PAR3615 Paramedicine – Medical Physiology II W2025 Lecture 1 Fluid & electrolyte balance - recap Acid-base balance  Copyright / Intellectual Property Notice Materials posted to courses are subject to Intellectual Property and Copyright protection, and as suc...

PAR3615 Paramedicine – Medical Physiology II W2025 Lecture 1 Fluid & electrolyte balance - recap Acid-base balance  Copyright / Intellectual Property Notice Materials posted to courses are subject to Intellectual Property and Copyright protection, and as such cannot be used and posted for public dissemination without prior permission from the College. For clarity, these protections are automatic once a work is created, and applies whether or not a copyright statement appears on the material. Students are bound by College policies, including AA 34 - Copyright, and SA 07 - Student Code of Conduct, and any student found to be using or posting course materials for public dissemination without permission is in breach of these policies and may be sanctioned.  Need HELP?? If you need help: 1. Email me for an appointment – can meet individually or as a group 2. Chat with me after or before class Email responses follow the AC policy – 48h grace (not including weekends and holidays) Expect email responses from me during regular College business hours with some exceptions. Ø After the 48h, please send me a polite reminder. J Dr. Pasan Fernando 3  Medical Physiology II Evaluation Test 1 20% Test 2 15% Wiley Quizzes 10% Labster Assignments 10% - based on Labster score Final Exam 40% Dr. Pasan Fernando  Main topics of study in Med Phys II 1. Fluid, electrolyte and acid-base physiology 2. Cardiovascular physiology 3. Cardiac and vascular anatomy 4. Respiratory physiology 5. Lymphatics and immunity Independent and hybrid study: § Cardiac anatomy (some overlap with lectures § Blood § Vasculature anatomy (some overlap with lectures) § Respiratory anatomy (some overlap with lectures) § Pregnancy and development - stages of pregnancy and labor Dr. Pasan Fernando 5  The Muddy Points survey is a good way to think through the lecture and highlight areas that you’re not clear on. Submit your muddy points via Brightspace Dr. Pasan Fernando  Case - 1 A young male, approximately 25-years old, is diabetic (insulin dependent). He appears confused and irritated. He reports having lower abdominal pain with periodic emesis. While sitting, he displays a rapid respiratory rate. On examination, he is hypotensive, tachypneic, and febrile. A fruity breath odor prompts a blood glucose test that reports above 600 mg/dL. Blood tests reveal the individual has hyperkalemia, hypomagnesemia, and increased serum ketones. An arterial blood gas analysis shows the person to be in metabolic acidosis. He is diagnosed with diabetic ketoacidosis and is treated with IV saline controlled for glucose and electrolyte variances. Dr. Pasan Fernando  Case 1 1. Describe the renal response to metabolic acidosis and respiratory alkalosis. 2. What is the expected compensatory response to metabolic acidosis? 3. What mechanism explains the patient’s report of lower abdominal pain? 4. Define hypotensive, tachypneic, febrile. ü Explain the significance of elevated serum ketones in this patient? ü What are the four three primary ways in which plasma acid-base homeostasis is maintained? ü What are the is the mechanism of metabolic acid-base imbalances? ü How is metabolic acidosis determined? ü What features distinguish metabolic acidosis from respiratory acidosis? ü Describe at least three physiological outcomes from acute metabolic acidosis Dr. Pasan Fernando  Fluid Balance - Recap Dr. Pasan Fernando  Ionic Composition of Major Body Compartments § Plasma and IF are almost identical § Plasma and IF are separated by the thin wall of capillary vessel Dr. Pasan Fernando 10 Sherwood, Human Physiology, 2020  Total Body Fluid § Intracellular fluid approx. 40% of total body weight § Composition of cellular fluid is similar between different types of cells § 20% of body weight is found in ECF and includes plasma and interstitial fluid (IF) § Plasma is noncellular part of blood; continuously exchanges with IF through pores of capillary membranes § Pores are highly permeable to almost all solutes in ECF except plasma proteins § Blood is considered a separate fluid compartment contained within the circulatory system § Blood is approx. 7% of total body weight Dr. Pasan Fernando 11  The Pensive Paramedic Make the connection between the integument and insensible water loss: Insensible water loss occurs by diffusion through the skin – up to 400 mL/day. What feature of the integument minimizes the excessive loss of water? Dr. Pasan Fernando 12  Disorders of Water Balance Three main disorders of water balance 1. Dehydration 2. Hypotonic hydration 3. Edema Dr. Pasan Fernando 13  Disorders in Water Balance - Dehydration § Conditions such as heat and high metabolism cause excessive water loss § Loss of water from ECF increases osmotic pressure of ECF § Cells respond by losing water – cells undergo plasmolysis § Dehydration – loss of water; either water alone or water with solutes à Distinguish between dehydration Dr. Pasan Fernando and hypovolemia 14  Dr. Pasan Fernando 15  Plasma Interstitial fluid Intracellular fluid (mOsm/L (mOsm/L water) (mOsm/L water) water) Na+ 142 139 14 K+ 4.2 4 14 Major soluble components and their Ca2+ 1.3 1.2 0 osmolarities in the extra- and Mg2+ 0.8 0.7 20 intracellular fluids HCO3- 24 28.3 10 § Total osmolarity is approximately 300 Amino acids 2 2 8 mOsm/L for each fluid compartment ATP Undetectable undetectable 5 § Corrected osmolarity accounts for the Glucose 5.6 5.6 undetectable attraction between cation and anions which decreases the osmotic activity of Protein 1.2 0.2 4 dissolved substances Urea 4 4 4 § Approximately 280 mOsm/L Phosphates 2 2 11 Sulfates 0.5 0.5 1 Dr. Pasan Fernando Lactate 1.2 1.2 1.5 Others ….. ….. ….. Total mOsm/L 299.8 300.8 301.2 Total corrected 282.2 281 281 16  Tonicity and Cell Volume Small changes in the concentration of impermeable solutes in the ECF causes large changes in cell volume § Tonicity describes the way a solution changes cellular volume, i.e., tonicity refers to the solution surrounding the cell § Cell is approximately 280 mOsm/L § In an isotonic solution, cell remains unchanged § In a solution that’s hypertonic, cell shrinks § In a solution that’s hypotonic, cell swells Dr. Pasan Fernando 17  Normal Fluid Handling and Osmotic Balance § Fluid transfer across cell membranes occurs rapidly § Differences in osmolarity between the two compartments is corrected within seconds to minutes § After drinking water - complete equilibrium throughout the entire body takes about 30 minutes Dr. Pasan Fernando https://www.aquasana.com/on/demandware.static/-/Sites-aquasana- Library/default/dw41a27bdd/final-journey.gif 18  Abnormal Fluid Conditions § Intracellular and extracellular fluid volumes can change § Excessive fluid intake, dehydration, renal dysfunction, emesis, hyperhidrosis, etc. § Water moves quickly across cell membranes § Cell membranes are impermeable to most solutes § Two main categories of IV fluids: crystalloid and colloid § Crystalloids are preferred § Fluid administration is indicated for resuscitation, rehydration, and maintenance Dr. Pasan Fernando 19  Disorders of Water Balance - Edema Edema § Excessive accumulation of fluid in the interstitial space or interstitial fluid § Causes tissue swelling but cells remain the same size § Extra fluid in the interstitial space impairs tissue function Dr. Pasan Fernando 20  The Pensive Paramedic Without the Na+/K+ ATPase pump, the ECF becomes hypertonic. True False Justify Dr. Pasan Fernando 21  Histopathology of cellular fluid accumulation – cellular swelling § Excessive water moving into the cell due to cellular injury § Termed hydropic degeneration § Cells appear to have vacuoles within them § Ex. Respiratory or cardiovascular injury leads to hypoxia § Hypoxia causes a loss of cellular oxygen delivery § Mitochondria switch to anaerobic metabolism (glycolysis); ATP production declines § Subsequent loss of Na+/K+ ATPase activity § Intracellular Na+ accumulates and water accumulates Dr. Pasan Fernando 22  Factors Causing Fluid Imbalance Hypovolemia: § Decrease in total body fluid caused by Ø Trauma induced blood loss Ø Dehydration and excessive fluid loss – vomiting, diarrhea Ø Polyuria – can be induced by diuretic drugs Ø High fever – insensible volume loss (respiratory, skin) Hypervolemia § Total body fluid overload § Related to iatrogenic causes from treating hypovolemia § Secondary causes are related to reduced excretion from renal failure Normovolemia with fluid imbalance § Accompanies fluid recovery following major fluid loss Dr. Pasan Fernando § Total fluid volume is normal, but fluid accumulates and is lost within the vasculature § Localized tissue vasoconstriction and loss of tissue perfusion – leads to multiorgan failure (shock) 23  Diabetes and hydration Diabetes - Greek for passing through Insipidus – Latin for tasteless Mellitus – Greek for pleasant tasting Diabetes insipidus vs Diabetes mellitus § DI and DM are unrelated § But both involve excessive urination Dr. Pasan Fernando 24  Diabetes Insipidus § DI is relatively rare; body makes too much urine § Symptoms include polyuria and polydipsia § Causes orthostatic hypotension, excessive electrolyte loss § Four types of Diabetes insipidus Central DI § Body does not make enough ADH/vasopressin Nephrogenic DI § Body is able to make ADH but the kidneys cannot respond to it. Dipsogenic DI § Hypothalamus continually stimulates the thirst centers Gestational DI § Temporarily develops during pregnancy Dr. Pasan Fernando 25  Role of Glucose and Insulin § All cells rely on energy sources to generate cellular energy (ATP) § Carbohydrates, lipids and proteins will all break down into glucose – primary metabolic fuel § Serum glucose comes from either food or glucose stores in the liver. § Serum glucose requires insulin to enter cells Dr. Pasan Fernando https://www.researchgate.net/figure/The-effect-of-insulin-on-glucose-uptake-and-metabolism-Insulin-activates-the_fig2_27476581 26  Diabetes Mellitus § DM includes a group of diseases related to the inability to produce or use insulin § The cause of DM varies with each type but all can lead to excessive glucose in the serum….and urine § DM includes Type I, and Type II Ø Prediabetes, and gestational diabetes are also considered forms of DM § Excessive glucose spills into the urine (glucosuria) § Polyuria occurs because glucose in the urine osmotically attracts water § Polydipsia occurs due to large water loss from the body and dehydration § Polyphagia occurs because cells are unable to use glucose which stimulates the appetite. Dr. Pasan Fernando 27  Type I Diabetes Mellitus Type I § Characterized by low insulin § Immune system destroys pancreatic islet beta cells § Previously known as insulin-dependent diabetes mellitus § Commonly develops in young people ( 35 yrs § Insulin is produced but cells are no longer sensitive to insulin § Insulin receptor number is decreased in cells § Clinical symptoms are mild; can be controlled by diet, exercise, weight loss Dr. Pasan Fernando 30 Dr. Pasan Fernando  Acid-Base Balance 1. Identify the sources of acids in the body 2. Identify the three main chemical buffer systems 3. Describe how each chemical buffer system resists changes in pH 4. Describe how the respiratory system affects acid-base balance Dr. Pasan Fernando 32  Acid-Base Balance Why is biological acidity and pH so closely regulated? Dr. Pasan Fernando 33  Acid-Base Balance § Normal pH of body fluids § Arterial blood: pH 7.4 § Venous blood, IF: pH 7.35 § ICF: pH 7.0 § Alkalosis: arterial pH >7.45 § Acidosis: arterial pH < 7.35 § Metabolic acid-base à bicarbonate ion HCO3- § Respiratory acid-base à Dr. Pasan Fernando carbonic acid H2CO3 34  Acid-Base Balance cont. Where does acidity come from? § Most H+ is produced as a by-product of metabolism: Ø Phosphorus-containing protein breakdown releases phosphoric acid into ECF Ø Lactic acid from anaerobic respiration of glucose Ø Fat metabolism: fatty acids and ketone bodies § H+ is liberated when CO2 is converted to HCO3- in blood. § Once H+ is generated, the body must deal with it effectively or else blood pH is at risk Dr. Pasan Fernando 35  Consequences of [H+] Fluctuation Small changes in [H+] have drastic consequences on normal cell function Outside the range of 7.35-7.45: § Acidosis – overall suppression of CNS – Disorientation, comatose § Alkalosis – hyperexcitability of NS – Paraesthesis, muscle twitch and spasm, convulsions § Elevated enzyme activity – Faster or slower enzyme activities can prevail when outside the normal range § Arrhythmias Dr. Pasan Fernando – K+ and H+ are oppositely exchanged in the kidneys 36  Acid-Base Balance cont. Free hydrogen ions are controlled by three mechanisms 1. Chemical buffer systems 2. Brain stem respiratory centers 3. Renal mechanisms Dr. Pasan Fernando 37  Chemical Buffer Systems Chemical buffer is a system of one or more compounds that act to resist pH changes when strong acid or base is added Will bind H+ if pH drops or release H+ if pH rises Three major buffering systems: Bicarbonate buffer system Phosphate buffer system Protein buffer system Dr. Pasan Fernando 38  Chemical Buffer Systems cont. Bicarbonate buffer system § Mixture of carbonic acid (H2CO3) and carbonate salts (HCO3-) Ø Ex. NaHCO3 (weak base) § Buffers in both the ICF and ECF but….only important in the ECF § If strong acid is added, HCO3− ties up H+ and forms H2CO3 (carbonic acid) 34. 5 6*347! ! 3"47! 5 6*4. #$%C'()*H,- /0*N)O*#0 /0*N)*H,- #*.$ § Buffering ability is directly related to concentration of HCO3- § HCO3- forms an alkaline reserve § Bicarbonate ion concentration approx. 25 mEq/L, closely regulated by the Dr. Pasan Fernando kidneys 39  Chemical Buffer Systems cont. Phosphate buffer system § Action nearly identical to bicarbonate buffer § Components are sodium salts of: Ø Dihydrogen phosphate (H2PO4−), a weak acid Ø Monohydrogen phosphate (HPO42−), a weak base § Unimportant in buffering plasma § Important in buffering urine and ICF, where phosphate concentrations are high Dr. Pasan Fernando 40  Chemical Buffer Systems cont. Protein buffer systems § Intracellular proteins and plasma proteins are powerful buffers à amphoteric § As pH rises à the carboxyl groups (COOH) release H+ # $ %CC'(!(# $ %CC ! ("('" § As pH falls, NH2 groups bind H+ $ % &'" (!('! (!($ % &'# Dr. Pasan Fernando § Hemoglobin is an intracellular buffer 41  Respiratory Regulation of H+ § Respiratory and renal systems work cooperatively and form the physiological buffering systems § Respiration eliminates CO2 %C# ! '#C ! '#%C$ ! '! ! '%C$ " § During CO2 unloading, reaction shifts to left, H+ forms into water. § During CO2 loading, reaction shifts to right, H+ is buffered by proteins Dr. Pasan Fernando 42  Respiratory Regulation of H+ cont. § If PCO2 in blood rises (hypercapnia), it activates medullary chemoreceptors Ø Causes increased respiratory rate and depth § Rising plasma H+ (acidosis) activates peripheral chemoreceptors Ø Causes increased respiratory rate and depth § Both cause more CO2 to be removed from the blood, pushing reaction to left, which reduces H+ concentration %C# ! '#C ! '#%C$ ! '! ! '%C$ " Dr. Pasan Fernando 43  Respiratory Regulation of H+ cont. § Alkalosis depresses the respiratory center Ø Respiratory rate and depth decrease, causing H+ concentration to increase § Respiratory system impairment causes acid-base imbalances Ø Hypoventilation causes respiratory acidosis Ø Hyperventilation causes respiratory alkalosis %C# ! '#C ! '#%C$ ! '! ! '%C$ " Dr. Pasan Fernando 44  Renal Regulation § Chemical buffer system (and associated buffering components) are not effective in eliminating excess acids or bases § Lungs eliminate carbonic acid via eliminating CO2 § Kidneys eliminate nonvolatile (fixed) acids to prevent metabolic acidosis. § Kidneys regulate blood levels of alkaline substances which helps to replenish chemical buffering capacity Dr. Pasan Fernando 45  Renal Regulation cont. § The kidneys regulate acid-base balance by adjusting the amount of blood bicarbonate § Generating or reabsorbing one HCO3- is the same as losing one H+ § HCO3- cannot directly cross the epithelial membrane into the peritubular capillaries; no direct reabsorption of HCO3- § HCO3- uses Na+ or exchanges with Cl- § H+ that is removed to the filtrate is buffered by HCO3- and forms with water – most of H2O is reabsorbed Dr. Pasan Fernando 46  Generating New Bicarbonate Ions § Metabolism of food generates new H+ § Body must generate new HCO3- to balance the H+ § New HCO3- can be generated by secreting (excreting) H+ as either buffered H+ or NH4+ Dr. Pasan Fernando 47  Generating New Bicarbonate Ions cont. Excretion of buffered H+ § Phosphate buffer system is important in urine § Intercalated cells of CD secrete H+ into urine § Phosphates buffer the H+ § New HCO3- is generated and moves into the interstitial space via HCO3-/Cl- exchanger and passively into the peritubular capillaries Dr. Pasan Fernando 48  Generating New Bicarbonate Ions cont. Excretion with NH4+ § Newly formed HCO3- is produced via glutamine metabolism § Glutamine is metabolized in PCT § Each glutamine produces two ammonium ions and two new bicarbonate ions § Bicarbonate ions move to blood, ammonium is excreted in urine § Blood alkaline reserve is replenished Dr. Pasan Fernando 49  Bicarbonate Ion Secretion § Bicarbonate ions are secreted (eliminated) when the body is in alkalosis § Involves type B intercalated cells of the CD § Opposite mechanism of bicarbonate ion reabsorption (in Type A intercalated cells). § Elimination of bicarbonate ion will conserve hydrogen ion § Most of nephron and collecting duct activity works to conserve bicarbonate ions rather than excrete them Dr. Pasan Fernando 50  Respiratory Acidosis and Alkalosis § PCO2 levels outside of 35-45 mm Hg can indicate inadequate respiratory function Respiratory Acidosis § PCO2 above 45 mm Hg § Due to decrease in ventilation or gas exchange § CO2 accumulates in the blood; causes acidemia Respiratory Alkalosis § PCO2 below 35 mm Hg § Common result of hyperventilation § CO2 is eliminated faster than it is produced; causes Dr. Pasan Fernando alkalemia 51  Normal serum values and their relationships - Metabolic/Respiratory Acidosis and Alkalosis § pH, bicarbonate and pCO2 are related § Free hydrogen ions [H+] is in the range of 35-45 mmol/L § Free hydrogen ion is represented by plasma pH § pH 7.35-7.45 ** § HCO3- = 22-26 mmol/L ** § plasma CO2 is represented by partial pressure of CO2 or pCO2 = 35-45 mmol/L. ** The relationship between pH, HCO3- and pCO2 is expressed as the Henderson-Hasselbalch Equation: pH = pKa + log [HCO3-] / [pCO2] The simplified version ignores pKa and log values – since these factors do not impact the overall equation Dr. Pasan Fernando pH ~ [HCO3-] / [pCO2] or pH ~ (bicarbonate/carbon dioxide) 52  Determining a Patient’s Acid-Base status pH, HCO3-, and pCO2 represent the values in the plasma. As bicarb changes (kidney), the pCO2 will compensate (lungs) and vice versa Compensation is not evident if the compensating variable (bicarb or CO2) remains within normal ranges § To determine the acid-base status of a patient, use the HH equation and write out the direction of change for each of: metabolic acidosis, metabolic alkalosis, respiratory acidosis, and respiratory alkalosis. § Next write out the HH equation and indicate the direction of change shown by the patient, keeping in mind the normal values for each § Determine the acid-base status based on the pattern of arrows § Determine if the compensating variable (bicarb – metabolic; pCO2 – respiratory) is within Dr. Pasan Fernando normal ranges; if so, there is no compensation; if not, it is compensating for the change in pH  Determined another way (from Derrickson) Normal ranges: pH 7.35-7.45, HCO3- = 22-26 mmol/L, pCO2 = 35-45 mmol/L. From a patient’s arterial blood sample: § Is the pH high (alkalosis) or low (acidosis) § Which value is out of the normal range, PCO2 or HCO3-? – this value may indicate the cause of the pH change. § Ex. pH 7.6 could be caused by low CO2 or high HCO3- § Changes in PCO2 are respiratory; changes in HCO3- are metabolic § Which value does not correspond to the change in pH? If its within the normal range, there is no compensation. If its outside the normal range, compensation Dr. Pasan Fernando is working to correct the pH imbalance § Normal ranges: pH 7.35-7.45, HCO3- = 22-26 mmol/L, pCO2 = 35-45 mmol/L. 54  The Pensive Paramedic Using the normal values: pH = 7.4, HCO3- = 24 mmol/L, pCO2 = 40 mmHg, determine the acid – base status. A patient has the following plasma values: pH = 7.31 HCO3- = 16, pCO2 = 33 a) Respiratory acidosis b) Respiratory alkalosis c) Metabolic acidosis Dr. Pasan Fernando d) Metabolic alkalosis e) No apparent acid-base problem 55  Respiratory Acidosis and Alkalosis cont. Dr. Pasan Fernando 56  Metabolic Acidosis Presentation Metabolic acidosis § Low blood pH and bicarbonate concentration § Caused by excessive alcohol intake § Excessive loss of bicarbonate (persistent diarrhea) § Accumulation of lactic acid (exercise/shock), starvation, ketosis in diabetic crisis, kidney failure Dr. Pasan Fernando https://healthjade.net/hyperchloremic-acidosis/ 57  Metabolic Alkalosis Presentation Metabolic alkalosis § Rising blood pH and bicarbonate concentrations. § Less common than metabolic acidosis § Can be caused by excessive vomiting, over-ingestion of antacids Dr. Pasan Fernando 58  Dr. Pasan Fernando 59  Muddiest Point – Post Lecture Reflection Dr. Pasan Fernando  § Identify the fluid compartments in the body. § Distinguish between sensible and insensible water loss. § What sensory receptors contribute to fluid balance? § The main respiratory muscles are under autonomic control, yet the contraction of these muscles can be controlled via somatic innervation. Define somatic innervation. What mechanism drives respiration in this instance? § What portion of the nephron is primarily responsible for H+ regulation? Why is it necessary to buffer H+ as it is secreted? What transport mechanism ensures the secretion of H+? Dr. Pasan Fernando 61