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1、Potassium Balance and Potassium ImbalancePart Potassium Balance Content and Distribution of Potassium in the Body Intake and Excretion of PotassiumDietary K intake70100mmol/dayECF 2%Serum K+round 4.5mmol/LK+Skin trivial normallyColon 10%Kidneys 80%More ingested,more excretedLess ingested,less excret
2、edNot ingested,excretion goes on Content,distribution,intake and excretion of K Content,distribution,intake and excretion of K Excretion ICFK+160mmol/L98%of the total body potassiumTotal body K content3157mmol/Kg body weight Maintenance of Potassium Homeostasis Distribution of K+across the cell memb
3、rane and Regulation of renal K+excretion Distribution of Potassium across the Cell MembraneThe Na+/K+ATPase membrane pump and permeability of ion channels1.Hormones 1.Hormones insulininsulin,glucagon,glucagon,catecholaminescatecholamines,thyroid hormone,thyroid hormone2.Serum K2.Serum K+3.pH of ECF
4、and plasma 3.pH of ECF and plasma osmolalityosmolality4.Others rate of cell breakdown,4.Others rate of cell breakdown,hypoxia,hypothermia,exercisehypoxia,hypothermia,exerciseInfluencing Factors KK+NaNa+NaNa+/K/K+-ATPaseATPaseKK+KK+HH+CatecholamineCatecholamine Insulin Insulin Regulation of Renal Pot
5、assium ExcretionFiltration,reabsorption and secretion of potassium The The nephronnephron and collecting tubule and collecting tubuleCl-NaNa+/K/K+ATPase(MgATPase(Mg2+2+activatedactivated)NaNa+/K/K+ATPaseATPaseHH+-KK+ATPaseATPaseAfferent Efferent arterioleBowmans capsuleglomerulusProximal tubuleReabs
6、orption GlucoseSodiumWaterBicarbonate(HCO3-)Henles loop(thick and thin segment)Primer Urine 180L/day(ultrafiltrate)Juxtaglomerular cellsReninAngiotensin I II IIIAldosterone(Adrenal cortex)RAAS(+)Macula densaReabsorption Sodium WaterdiluteReabsorption Water SodiumExchange of ionHydrogen-SodiumPotassi
7、um-SodiumReabsorb waterADH can increase the permeability of the tubular membrane walls to reabsorb more water.Collecting tubulecondenseUrine 1.52.0L/dayAdlosterone can enhance the exchange of potassium-sodium(increases the reabsorption of sodium)(enhances the excretion of potassium)(1)Reabsorb sodiu
8、m(water)and excrete potassium.(2)Excrete hydrogen and reabsorb bicarbonateDistal convoluted tubuleRegulation of Renal Potassium ExcretionFiltration,reabsorption and secretion of potassiumSecretion of potassium in the distal and collecting tubules principal cells,with Na+/K+ATPase membrane pump,for s
9、ecretion of K+lumenPrincipal CellPrincipal CellbloodK+Na+Na+K+Cl-Cl-K+CO2HCO3-Cl-Cl-H+K+CO2Intercalated CellIntercalated CellRegulation of Renal Potassium ExcretionFiltration,reabsorption and secretion of potassiumSecretion of potassium in the distal and collecting tubules Reabsorption of K in the d
10、istal and collecting tubules,intercalated cells,with H+/K+-ATPase(proton pump)for reabsorption of K+Regulation of Renal Potassium ExcretionFiltration,reabsorption and secretion of potassiumSecretion of potassium in the distal and collecting tubulesReabsorption of K in the distal and collecting tubul
11、es intercalated cells,with H+/K+-ATPase (proton pump)for reabsorption of K+Factors influencing excretion of K+by the distal and collecting tubules Factors Influencing Excretion of K+by the Distal and Collecting TubulesAldosterone activates Na+/K+ATPase,increase membrane permeability to KK+in the ECF
12、Flow rate of tubular fluid in the distal tubulepH of ECF pH inhibits Na+/K+ATPase+lumenlumenbloodbloodPrincipal CellPrincipal CellK+Na+Na+K+Cl-Cl-K+K+CO2HCO3-Cl-Cl-H+K+CO2Intercalated CellIntercalated CellH+flow rateFactors Influencing Excretion of K+by the Distal and Collecting Tubules+Ald+-Mainten
13、ance of Potassium HomeostasisDistribution of potassium across the cell membrane Regulation of renal potassium excretion Excretion of K by the Colon also controlled by aldosterone Function of Potassium in the Body Function of Potassium in the BodyThe part K+plays in metabolismMaintenance of the resti
14、ng membrane potential of excitable cellsMaintenance and regulation of osmotic pressure and acid-base balance both in ICF and ECFPart Potassium Imbalance-abnormal changes in K+in ECFHypokalemiaSerum K+3.5mmol/L,may or may not be associated with K deficitECF 2%Dietary intake Serum K+3.5mmol/LG.I losse
15、s-diarrhea,vomitingRenal losses-diuretics,some diseases of the kidney Losses from the skin-profuse sweating,burnsExcessive losses ICFK+may or may not be decreasedTotal body K content decreased (K deficit)shifting normalCrude cotton seed oil poisoning orEtiology and PathogenesisEtiology and Pathogene
16、sis.Inadequate Intake Fasting,anorexia,inability to eat,prolonged IV alimentation without K supplementation,alcoholism .Excessive Losses 1.Gastrointestinal losses Diarrhea extrusion of large amount of alkaline liquid stool with a high content of KK depletion,acidosis,ECF volume contraction secretion
17、 of aldosterone Vomiting mainly increased renal excretion of K+due to metabolic alkalosis caused by loss of gastric acid,contraction of ECF volumeEtiology and Pathogenesis.Inadequate Intake.Excessive Losses 1.Gastrointestinal losses 2.Excessive renal losses (1)Diureticsincreased flow rate and delive
18、ry of Na+,Cl-and water to the distal tubule increased Na+-K+exchange;volume contraction increased aldosterone renal K excretion Regulation of Renal Potassium ExcretionThe The nephronnephron and collecting tubule and collecting tubuleCl-NaNa+/K/K+ATPase(MgATPase(Mg2+2+activatedactivated)NaNa+/K/K+ATP
19、aseATPaseHH+-KK+ATPaseATPaseEtiology and Pathogenesis.Inadequate Intake.Excessive Losses 1.Gastrointestinal losses 1.Gastrointestinal losses 2.Excessive renal losses2.Excessive renal losses (1)Diuretics (1)Diuretics (2)Some diseases of the kidney (2)Some diseases of the kidney Renal tubular acidosis
20、 Renal tubular acidosisExcessive Renal Losses(1)Diuretics(2)Some diseases of the kidney Renal tubular acidosis Renal tubular acidosis Diuretic recovery phase of acute renal failure Diuretic recovery phase of acute renal failure(3)Antibiotics(4)Excess of adrenocortical hormones AldosteronismAldostero
21、nism,Cushings syndrome,Cushings syndrome(5)Magnesium deficiency Diuretic recovery phase of acute renal failureDiuretic recovery phase of acute renal failureRegulation of Renal Potassium ExcretionThe The nephronnephron and collecting tubule and collecting tubuleCl-NaNa+/K/K+ATPase(MgATPase(Mg2+2+acti
22、vatedactivated)NaNa+/K/K+ATPaseATPaseHH+-KK+ATPaseATPaseExcessive Renal Losses(1)Diuretics(2)Some diseases of the kidney Renal tubular acidosis Renal tubular acidosis Diuretic recovery phase of acute renal failure Diuretic recovery phase of acute renal failure(3)Antibiotics(4)Excess of adrenocortica
23、l hormones AldosteronismAldosteronism,Cushings syndrome,Cushings syndrome(5)Magnesium deficiency(6)AlkalosisEtiology and Pathogenesis.Inadequate Intake.Excessive Losses 1.Gastrointestinal losses 2.Excessive renal losses 3.Excessive losses from the skin Profuse sweatings,burns or scalds Etiology and
24、Pathogenesis.Inadequate Intake.Excessive Losses.Shifting of K+from the ECF to ICF 1.Overdose of insulin 2.-adrenergic agonist overdose NaNa+NaNa+/K/K+-ATPaseATPaseKK+KK+HH+AlbuterolAlbuterolInsulin Insulin Etiology and Pathogenesis.Inadequate Intake.Inadequate Intake.Excessive Losses.Excessive Losse
25、s.Shifting of K.Shifting of K+from the ECF from the ECF to ICFto ICF 1.Overdose of insulin1.Overdose of insulin 2.2.-adrenergic agonist overdose-adrenergic agonist overdose 3.Alkalosis 3.Alkalosis 4.Barium poisoning 4.Barium poisoning 5.Familial 5.Familial hypokalemichypokalemic periodic periodic pa
26、ralysisparalysis NaNa+NaNa+/K/K+-ATPaseATPaseKK+KK+HH+AlbuterolAlbuterolInsulin Insulin Etiology and Pathogenesis.Inadequate Intake.Excessive Losses.Shifting of K+from the ECF to ICF Crude Cotton Seed Oil poisoningEffects on the Body factors influencing the effects:the underlying diseases,the degree
27、 of hypokalemia and rapidity of its development,the ratio of K+i/K+eEffects on Neuromuscular Excitability The Resting Membrane Potential(RMP)and Action Potential The Resting Membrane Potential(RMP)and Action Potential(AP)of a skeletal muscle cell in the normal state(AP)of a skeletal muscle cell in t
28、he normal state +350-60-90Millivolts Milliseconds Threshold Nernst equation Em=-60lgK+icf/K+ecf(mv)Acute HypokalemiaK+i/K+e RMP more negative than normalhyperdepolarization block,excitabilitymuscle weakness,flaccid paralysis,smooth muscle symptoms-120-90-60-30030Normal Low K+High K+TMPRMPAction pote
29、ntial(AP)The effects of serum K+concentration on cellular membrane excitability mv ratio of K+i to K+e may be normal,RMP and excitability unchanged,interfering with cellular metabolism and vasodilation of muscles during exerciseChronic HypokalemiaEffects on the Heart A Brief Review of the Bioelectri
30、c Phenomena of the Heart a:effective refractory period;b:relative refractory period c:supranormal periodRMP and AP of a Ventricular Muscle Cell of the Heart40+200-20406080100401234340124RMPmax.diast.potentialAtrial musclePurkinjes fiberThe Membrane Potential of Atrial Muscle,and Purkinjes Fiber1.Eff
31、ects on excitability RMP5.5mmol/L,a medical emergency Etiology and PathogenesisInadequate excretion of K Renal failure,hypoaldosteronism,K sparing diureticsRedistribution of K in the body tissue injury,acidosis,insulin deficiency,familial hyperkalemic periodic paralysisIncreased intake of Krapid IV
32、K administration Effects on the Body.Effects on neuromuscular excitability In mild to moderate hyperkalemia the ratio of K+i to K+e RMP less negative than normal,excitability abnormal sensibility(paresthesia),diarrhea Severe hyperkalemia,RMP decreased to level of TMP,depolarization block muscle weak
33、ness,paralysis,dizziness,coma .Effects on neuromuscular excitability.Effects on the heart 1.Effects on excitability In mild to moderate cases,excitability ,phase 0 upstroke smaller and slower;Phase 2 plateau prolonged,phase 3 repolarization shortened In severe cases,no AP can be induced cardiac arre
34、stEffects on the BodyEffects on the Body.Effects on neuromuscular excitability.Effects on the heart 1.Effects on excitability 2.Effects on autorhythmicity K channel conductance ,autorhythmicity .Effects on neuromuscular excitability.Effects on the heart 1.Effects on excitability 2.Effects on autorhy
35、thmicity 3.Effects on conductivity a smaller and slower phase 0 upstroke conductivity Effects on the Body.Effects on neuromuscular excitability.Effects on the heart 1.Effects on excitability 2.Effects on autorhythmicity 3.Effects on conductivity 4.Effects on contractility high serum K+inflow of Ca2+
36、contractility Effects on the Body.Effects on neuromuscular excitability.Effects on the heart.Effects on acid-base balance ECF K+secretion of insulin and aldosterone ECF K+shifted into cells while H+move out ECF K+Na+-K+exchange in renal distal tubules and secretion of H+ECF K+renal NH4 production,acid retention metabolic acidosisEffects on the BodyEffects on Acid-Base BalancePrinciples of Prevention and Treatment Restriction of K intake,control of underlying diseases,insulin+glucose,use of Ca2+and Na+to counteract K,bicarbonate infusion,ion-exchange resin,dialysis