20 Integrative Physiology II: Fluid in addition to Electrolyte Balance

20 Integrative Physiology II: Fluid in addition to Electrolyte Balance www.phwiki.com

20 Integrative Physiology II: Fluid in addition to Electrolyte Balance

Hunter, Fred, Meteorologist has reference to this Academic Journal, PHwiki organized this Journal 20 Integrative Physiology II: Fluid in addition to Electrolyte Balance 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+, in addition to Ca2+: nervous, cardiac& muscle function- imbalances cause problems with membranes of cells that are excitable. Primarily replaced with thirst & appetite in addition to 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 in addition to urine as long as mation have largest impact. Key factors as long as Homeostasis Na+ & H2O= affect ECF Osmolarity: amounts of solutes dissolved in solution, concentration in addition to permeability influence direction of osmosis which changes the size of cells

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Osmosis in addition to 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, in addition to CV responses Figure 5-29 Water Balance in the Body Figure 20-2 Water makes up 50-60% 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 Balance A model of the role of the kidneys in water balance Figure 20-3 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 in addition to blood volume

Fluid in addition to Electrolyte Homeostasis The body’s integrated response to changes in blood volume in addition to blood pressure incorporate many systems Decreased blood volume will result in mechanisms that increase blood pressure in addition to volume, in addition to reduce water loss Figure 20-1a Fluid in addition to Electrolyte Homeostasis Figure 20-1b Increased blood volume results in the excretion of salt in addition to water which eventually reduces blood pressure in addition to ECF/ICF volumes. Urine Concentration Osmolarity changes as filtrate flows through the nephron. Reabsorption is controlled by kidney tissue concentrations as water permeability in addition to diffusion of solutes changes as needed. Water in addition to sodium reabsorption alter urine concentration. Diuresis is the removal of excess water. Figure 20-4

Water Reabsorption Vasopression or antidiuretic hormone causes a graded effect of as long as ming water pores on collecting duct cells. Thus permeability is increased in addition to more water is retained making urine more concentrated. Figure 20-5a Water Reabsorption Figure 20-5b If vasopressin is absent water will not move out through water pores (aquaporins) in addition to the urine will be dilute. Water Reabsorption Figure 20-6, steps 1–2 The mechanism of vasopressin action on tubular cells of the nephron

Water Reabsorption Figure 20-6, steps 1–3 Apical membrane water permeability increases exponentially with water pores are added Water Reabsorption Figure 20-6, steps 1–4 Vassopressin is also called antidiuretic hormone- it causes reabsortion of water (in turn increasing urine concentration in addition to decreasing volume). Factors Affecting Vasopressin Release Figure 20-7 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

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+ in addition to K+ reabsorption happens in ascending limb; resulting in dilute urine. Water amounts can be changed again at distal tubule in addition to collecting duct. Figure 20-10 Fluid in addition to 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 in addition to the vasa recta- this allows as long as water to move out of the tubule in addition to 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+) Sodium Balance Homeostatic responses to salt ingestion show the integrated effects on sodium, water, in addition to blood pressure. Without salt appetite [salt] would increase in addition to tissue cells would shrink. Thus vasopressin in addition to thirst is activated. Figure 20-12 .

Sodium Balance Figure 20-13, steps 1–2 Aldosterone action in principle cells- targets cells of the distal convoluted tubule in addition to collecting duct. Sodium Balance Figure 20-13, steps 1–4 Existing channels are called the leak proteins that allow as long as a rapid movement of ions Sodium Balance Figure 20-13, steps 1–5 Aldosterone causes K+ secretion in addition to sodium reabsorption. A secondary effect is that water follows sodium.

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. Figure 20-15 Sodium Balance The renin-angiotensin-aldosterone pathway- (RAAS). Renin is an enzyme that assist in ANG II as long as mation. ANGII activates several mechanisms that ultimately increase blood pressure in addition to volume Figure 20-14 Sodium Balance Action of natriuretic peptides- cause sodium loss through urine (natriuresis) in addition to act as RAAS antagonist. They are released when myocardial cells stretch too much or during heart failure Figure 20-16

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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, in addition to resting membrane potential is more negative (hyperpolaized)= stronger stimulus Muscle weakness in addition to failure of respiratory muscles in addition to 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, in addition to diuretics Behavioral Mechanisms Drinking water in addition to eating salt is the only way the body obtains these substances, there as long as e 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 in addition to signal thirst quench Low sodium stimulates salt appetite – the hypothalamus also has centers as long as salt appetite which trigger a response when osmolarity is low. Avoidance behaviors help prevent dehydration Desert animals avoid the heat Disturbances in Volume in addition to Osmolarity Figure 20-17 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

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, in addition to 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 in addition to lowering of osmolarity Acid-Base Balance Normal plasma pH is 7.38–7.42- also resembles the pH inside cells, its optimum as long as 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+ in addition to K+ in antiport fashion Acidosis: neurons become less excitable in addition to 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 Acid-Base Balance Hydrogen balance in the body is quickly compensated by ventilation in addition to slowly compensated by renal regulation. Figure 20-19

pH Disturbances Overview of renal compensation as long as acidosis. The nephron takes care of the 25% of compensation the lungs can’t h in addition to le. They excrete H+ by trapping it in ammonia in addition to phosphate ions. They also make HCO3 Figure 20-21 Intercalated Cells Role of intercalated cells in acidosis in addition to alkalosis – these are located in between principal cells of the distal tubule in addition to have high amounts of carbonic anhydrase. Movement occurs via H+-ATPase in addition to H+-K+-ATPase Figure 20-23 Acid-Base Balance Respiratory system increases CO2 during hypoventilation in addition to decreases it during hyperventilation. When metabolism causes a disturbance respiratory keeps CO2 levels normal but pH changes because buffer levels drop. Mass balance shifts equation to left or right CO2 + H2O == H2CO3 == H+ HCO3 .

Hunter, Fred Meteorologist

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