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POWERPOINT ® LECTURE SLIDE PRESENTATION by LYNN CIALDELLA, MA, MBA, The University of Texas at Austin Additional Text by J Padilla exclusively for physiology.

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Presentation on theme: "POWERPOINT ® LECTURE SLIDE PRESENTATION by LYNN CIALDELLA, MA, MBA, The University of Texas at Austin Additional Text by J Padilla exclusively for physiology."— Presentation transcript:

1 POWERPOINT ® LECTURE SLIDE PRESENTATION by LYNN CIALDELLA, MA, MBA, The University of Texas at Austin Additional Text by J Padilla exclusively for physiology at ECC Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings HUMAN PHYSIOLOGY AN INTEGRATED APPROACH FOURTH EDITION DEE UNGLAUB SILVERTHORN UNIT 3 20 Integrative Physiology II: Fluid and Electrolyte Balance

2 Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Mass Balance in the Body  Homeostasis requires that amounts gained must be equal to that lost.  Ion concentration- need proper amounts of Na+, Cl-, K+, and Ca2+:  nervous, cardiac& muscle function- imbalances cause problems with membranes of cells that are excitable.  Primarily replaced with thirst & appetite and excreted in urine, sweat, & feces  pH balance- cells functions within a pH range that is maintained by H+, CO2, & HCO3–  Fluid- water levels need to be maintained, ingestion and urine formation have largest impact.

3 Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Key factors for Homeostasis  Na+ & H 2 O= affect ECF  Osmolarity: amounts of solutes dissolved in solution, concentration and permeability influence direction of osmosis which changes the size of cells

4 Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure 5-29 Osmosis and Osmotic Pressure Osmolarity describes the number of particles of solution in a quantity of osmoles OsM per liter Osmolarity is influence by fluid, ion, & protein levels. Compensation occurs via renal, behavioral, repiratory, and CV responses

5 Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure 20-2 Water Balance in the Body Water makes up % of total body weight. Main entry way is through food, most lost in urine unless there is excessive sweating or diarrhea Homeostasis maintains water balance unless there is pathology or an abnormal ingestion of water. Men have more water than women Water makes up % of total body weight. Main entry way is through food, most lost in urine unless there is excessive sweating or diarrhea Homeostasis maintains water balance unless there is pathology or an abnormal ingestion of water. Men have more water than women

6 Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure 20-3 Water Balance A model of the role of the kidneys in water balance Kidneys cannot add water, only preserve it or get rid of excess amounts. Renal filtration will stop if there is a major loss causing extremely low blood pressure and blood volume

7 Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Fluid and Electrolyte Homeostasis The body’s integrated response to changes in blood volume and blood pressure incorporate many systems Decreased blood volume will result in mechanisms that increase blood pressure and volume, and reduce water loss Figure 20-1a

8 Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure 20-1b Fluid and Electrolyte Homeostasis Increased blood volume results in the excretion of salt and water which eventually reduces blood pressure and ECF/ICF volumes.

9 Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure 20-4 Urine Concentration Osmolarity changes as filtrate flows through the nephron. Reabsorption is controlled by kidney tissue concentrations as water permeability and diffusion of solutes changes as needed. Water and sodium reabsorption alter urine concentration. Diuresis is the removal of excess water.

10 Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure 20-5a Water Reabsorption Vasopression or antidiuretic hormone causes a graded effect of forming water pores on collecting duct cells. Thus permeability is increased and more water is retained making urine more concentrated.

11 Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure 20-5b Water Reabsorption If vasopressin is absent water will not move out through water pores (aquaporins)a nd the urine will be dilute.

12 Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure 20-6, steps 1–2 Water Reabsorption Collecting duct lumen Filtrate 300 mOsm Cross-section of kidney tubule Collecting duct cell Second messenger signal cAMP Medullary interstitial fluid Vasopressin receptor Vasa recta Vasopressin binds to mem- brane receptor. Receptor activates cAMP second messenger system mOsM 700 mOsM The mechanism of vasopressin action on tubular cells of the nephron

13 Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure 20-6, steps 1–3 Water Reabsorption Collecting duct lumen Filtrate 300 mOsm Exocytosis of vesicles Cross-section of kidney tubule Collecting duct cell Second messenger signal cAMP Storage vesicles Aquaporin-2 water pores Medullary interstitial fluid Vasopressin receptor Vasa recta Vasopressin binds to mem- brane receptor. Receptor activates cAMP second messenger system. Cell inserts AQP2 water pores into apical membrane mOsM 700 mOsM Apical membrane water permeability increases exponentially with water pores are added

14 Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure 20-6, steps 1–4 Water Reabsorption Collecting duct lumen Filtrate 300 mOsm H2OH2O Exocytosis of vesicles Cross-section of kidney tubule Collecting duct cell Second messenger signal H2OH2O cAMP Storage vesicles Aquaporin-2 water pores 600 mOsM H2OH2O Medullary interstitial fluid Vasopressin receptor 600 mOsM Vasa recta H2OH2O 700 mOsM Vasopressin binds to mem- brane receptor. Receptor activates cAMP second messenger system. Cell inserts AQP2 water pores into apical membrane. Water is absorbed by osmosis into the blood Vassopressin is also called antidiuretic hormone- it causes reabsortion of water (in turn increasing urine concentration and decreasing volume).

15 Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure 20-7 Factors Affecting Vasopressin Release Three stimuli control vasopressin but the most potent is blood osmolarity above 280mOsM. The higher the osmolarity, the more vasopressin released by posterior pituitary. Osmoreceptors also trigger thrist centers in hypothalamus

16 Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure Water Balance Countercurrent exchange in the medulla of the kidney. Descending limb is permeable to water while the ascendig limb is permeable to ions. 25% of all Na+ and K+ reabsorption happens in ascending limb; resulting in dilute urine. Water amounts can be changed again at distal tubule and collecting duct.

17 Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Fluid and Electrolyte Balance  Vasa recta removes water- blood runs in opposite direction as filtrate, water moves in according to the concentration gradient  Close anatomical association of the loop of Henle and the vasa recta- this allows for water to move out of the tubule and into the blood without dilution the interstitial fluid in the medulla.  Urea increase the osmolarity of the medullary interstitium- transporter proteins move urea into the medulla to increase osmolarity of the interstitial fluid creating a gradient to move water out without affecting the movement of other ions (Na+ & K+)

18 Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure Sodium Balance Homeostatic responses to salt ingestion show the integrated effects on sodium, water, and blood pressure. Without salt appetite [salt] would increase and tissue cells would shrink. Thus vasopressin and thirst is activated...

19 Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure 20-13, steps 1–2 Sodium Balance Interstitial fluid Blood Aldosterone receptor P cell of distal nephron Lumen of distal tubule Aldosterone combines with a cytoplasmic receptor. Hormone-receptor complex initiates transcription in the nucleus Transcription mRNA Aldosterone action in principle cells- targets cells of the distal convoluted tubule and collecting duct.

20 Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure 20-13, steps 1–4 Sodium Balance Interstitial fluid Blood Aldosterone ATP Aldosterone receptor P cell of distal nephron Translation and protein synthesis ATP Lumen of distal tubule Aldosterone combines with a cytoplasmic receptor. Hormone-receptor complex initiates transcription in the nucleus. New protein channels and pumps are made. Aldosterone- induced proteins modify existing proteins Transcription mRNA New channels Proteins modulate existing channels and pumps. New pumps Existing channels are called the leak proteins that allow for a rapid movement of ions

21 Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure 20-13, steps 1–5 Sodium Balance Interstitial fluid Blood Aldosterone ATP Aldosterone receptor P cell of distal nephron Translation and protein synthesis K+K+ Na + K+K+ K+K+ ATP K + secreted Na + reabsorbed Lumen of distal tubule Aldosterone combines with a cytoplasmic receptor. Hormone-receptor complex initiates transcription in the nucleus. New protein channels and pumps are made. Aldosterone- induced proteins modify existing proteins. Result is increased Na + reabsorption and K + secretion Transcription mRNA New channels Proteins modulate existing channels and pumps. New pumps Aldosterone causes K+ secretion and sodium reabsorption. A secondary effect is that water follows sodium.

22 Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure Sodium Balance Decreased blood pressure stimulates renin secretion. Granular cells can be activated to release renin by three factors: drop in blood pressure, a signal from the kidneys, or increased sympathetic activity.

23 Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure Sodium Balance The renin- angiotensin- aldosterone pathway- (RAAS). Renin is an enzyme that assist in ANG II formation. ANGII activates several mechanisms that ultimately increase blood pressure and volume

24 Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure Sodium Balance Action of natriuretic peptides- cause sodium loss through urine (natriuresis) and act as RAAS antagonist. They are released when myocardial cells stretch too much or during heart failure

25 Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Potassium Balance  Regulatory mechanisms keep plasma potassium in narrow range (3.5-5meq/L)  Aldosterone is released in response to excess levels, it increases permeability at distal nephron so K is moved into the urine while sodium is reabsorbed  Hypokalemia (K+ levels below 3)  In ECF levels are low, K+ leaves the cell, and resting membrane potential is more negative (hyperpolaized)= stronger stimulus  Muscle weakness and failure of respiratory muscles and the heart due to hyperpolarized neurons.  Hyperkalemia (K+ levels above 6)  In ECF levels are high, more K+ enters the cell, thus depolarizing it but then less able to repolarize thus LESS excitable  Can lead to cardiac arrhythmias  K+ irregularities include kidney disease, diarrhea, and diuretics

26 Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Behavioral Mechanisms Drinking water and eating salt is the only way the body obtains these substances, therefore individuals who cannot do this must be assisted.  Drinking replaces fluid loss – when body osmolarity raises above 280mOsM hypothalmic osomreceptors trigger thrist. Oropharynx receptors are stimulated by cold drink and signal thirst quench  Low sodium stimulates salt appetite – the hypothalamus also has centers for salt appetite which trigger a response when osmolarity is low.  Avoidance behaviors help prevent dehydration  Desert animals avoid the heat

27 Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Disturbances in Volume and Osmolarity Figure In each situation compensantion mechanism aim to bring conditions to normal, in some cases there is incomplete compenstation. Notice how most imbalances are due to what is ingested or loss in excess amounts

28 Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Severe Dehydration Compensation  Condition: low ECF volume, low blood pressure, high osmolarity  Compensation Mechanisms  Cardiovascular Responses- increase cardiac output & vasoconstriction to increase blood pressure. Vasoconstriction reduces GFR activating granular cells to release renin  Angiotensin II- produce after renin release that activates RAAS pathway to trigger thirst, vasopressin release, and vasoconstrion. (aldosterone is not release as it would increase osmolarity)  Vassopressin- increase water reabsorption to reduce loss in urine  Thrist/ IV-replacement of loss fluids and lowering of osmolarity

29 Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Acid-Base Balance  Normal plasma pH is 7.38–7.42- also resembles the pH inside cells, its optimum for proper protein & enzyme function  H + concentration is closely regulated- slight pH changes indicate a 10-fold increase/decrease in [H+] which can have damaging effects on protein structure & function.  Abnormal pH affects the nervous system- H+ imbalances cause K+ imbalances because transporter protein in kidneys moves H+ and K+ in antiport fashion  Acidosis: neurons become less excitable and CNS depression patients can fall into a coma or have respiratory failure  Alkalosis: hyperexcitable- numbness, tingling, muscle twitches, severe cases lead to paralysis of respiratory muscles  pH disturbances- induced by an imbalance of H+ input/output  Compensation by buffers, ventilation, or renal regulation  Greatest source is CO2 level changes induced by metabolic or respiratory factors

30 Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure Acid-Base Balance Hydrogen balance in the body is quickly compensated by ventilation and slowly compensated by renal regulation.

31 Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Acid and Base Input Acid  Organic acids – acids produced by the body during metabolism or ingested molecules that realease H+ (acidic fruits, amino acids, fatty acids)  Under extraordinary conditions – produce more H+ than the body can normally get rid off and cause pathological effects  Metabolic organic acid production can increase Ketoacids – strong acids produced when fats & proteins are metabolized  Diabetes – metabolism disorder causes ketoacid formation  Accumulation of CO 2 - can occur as a result of anaerobic respiration, increased metabolism, or decreased ventilation  Acid production - CO 2 combines with water rapidly to make an acid and drop pH. Respiratory system gets rid of 75% of a Base  Few dietary sources of bases- conditions of alkalosis rarely encountered

32 Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure pH Disturbances The reflex pathway for respiratory compensation of metabolic acidosis responds to shifts in H+ & CO2 based on the law of mass action. CO2 + H2O == H2CO3 == H+ HCO3.

33 Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings pH Homeostasis  Buffers moderate changes in pH- cannot prevent changes, they absorb/release H+  Cellular proteins, phosphate ions, and hemoglobin- serve as intracellular buffers  Ventilation  Rapid- quickly gets rid of CO 2 by increasing breathing rate  75% of disturbances- are cleared by ventilation thanks to the central and peripheral chemoreceptors that sense changes in [H+]  Renal regulation- uses ammonia and phosphate buffers in addition to  Directly excreting or reabsorbing H +  Indirectly by change in the rate at which HCO 3 – buffer is reabsorbed or excreted

34 Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure pH Disturbances Overview of renal compensation for acidosis. The nephron takes care of the 25% of compensation the lungs can’t handle. They excrete H+ by trapping it in ammonia and phosphate ions. They also make HCO3

35 Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure Intercalated Cells Role of intercalated cells in acidosis and alkalosis – these are located in between principal cells of the distal tubule and have high amounts of carbonic anhydrase. Movement occurs via H + -ATPase and H + -K + -ATPase

36 Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Acid-Base Balance Respiratory system increases CO 2 during hypoventilation and decreases it during hyperventilation. When metabolism causes a disturbance respiratory keeps CO 2 levels normal but pH changes because buffer levels drop. Mass balance shifts equation to left or right Respiratory system increases CO 2 during hypoventilation and decreases it during hyperventilation. When metabolism causes a disturbance respiratory keeps CO 2 levels normal but pH changes because buffer levels drop. Mass balance shifts equation to left or right CO2 + H2O == H2CO3 == H+ HCO3.


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