Acid-Base Notes PDF

Body fluids and fluid compartments - Aqueous fluids are required for chemical reactions - Water moves across membranes via osmosis a. Water moves in/out of cells and tissue depending on concentrations of water and solutes b. Homeostasis requires maint...

Body fluids and fluid compartments - Aqueous fluids are required for chemical reactions - Water moves across membranes via osmosis a. Water moves in/out of cells and tissue depending on concentrations of water and solutes b. Homeostasis requires maintenance of fluids Fluid balance: maintaining appropriate volume and concentrations of body’s intracellular and extracellular fluids - Study of water balance - Water gain= water loss *water helps with the transfusion of diffusion of solutes form the blood to the cells/tissue and vise versa* review Cell transport: Passive: - No atp - Diffusion (high concentration to low) >1. osmosis - 2.facilitated (channel proteins) - 3.filtration (relying on hydrostatic pressures) active : - Endocytosis(form vesicle so it can move inside the cell) - Exocytosis (excreting it by a vesicle outside of the cell) - Facilitated active transport (moves through membrane using atp) Body water content 1. Infants : 73% more water (low body fat, and low bone mass) 2. Adult males: 60% water 3. Adult females: 50% water (higher fat content, less skeletal muscle mass) - Adipose tissue is the least hydrated of all - Water content declines to 45% in old age Fluid compartments - Total body water = 40L *blood is about 5L* 2 main fluid compartments 1. Intracellular fluid (ICF) compartment: ⅔ in cells (25L) 2. Extracellular fluid (ECF) compartment: ⅓ outside cells (15L) - plasma : 3L - Interstitial fluid (IF): 12L in spaces between cells a. Usually considered part of IF: lymph, CSF, humors of eye, serous fluid, gastrointestinal secretion Composition of body fluids - Water: universal solvent - solutes : what is dissolved in water *mixture of a solute and solvent* Classified as nonelectrolytes and electrolytes - Nonelectrolytes: most organic a. They do not dissociate in water ex: glucose, lipids, creatinine, urea b. No charged particles created (2) Electrolytes - Dissociate into ions in water ex:inorganic salts, all acids/bases, some proteins a. Ions conduct electrical current *they are ionic bonds* - Greater osmotic power than nonelectrolytes a. Greatest ability to cause fluid shifts *they move a lot easier* *each area has different membranes and proteins in the membrane for eye or digestive* Extracellular and intracellular fluids Each fluid compartment has distinctive patterns of electrolytes ECF: - Major cations: Na+ - Major anions: Cl- Except: higher proteins, lower Cl- content of plasma*not important* *talking about the charge difference it was making in the muscle fibers and neuron axons, with the electrolytes bc it was rich outside with Na+ and Cl- making it positive outside* ICF: - Low in Na+ and Cl- - Major cation: K+ - Major anion: HPO4 More soluble proteins than in plasma (2) - Electrolytes are the most abundant solutes in body fluids; and determine most chemical and physical reactions - Bulk of dissolved solutes are: proteins, phospholipids, cholesterol and triglycerides a. 90% in plasma b. 60% in IF c. 97% in ICF Fluid movement among compartments 2 things regulate continuous exchange(waste, nutrients, gasses) and mixing of fluids: *in 4 areas it will help: capillary level, nephron level,respiratory capillary, digestive capillary* 1. Osmotic pressure 2. Hydrostatic pressures - Water moves freely in osmotic gradient - All body fluids osmolarity almost always equal  - Change in solute concentration in either compartment= net water flow a. Inc. ECF osmolarity > water leaves cell b. Dec. ECF osmolarity > water enters cell *in solutes inside cell is 10% and h2O is 90% and outside cell ECF is 5% solutes and 95% H2O they will go from high to low to balance the cell out* (2) Between plasma and IF across capillary walls - Fluid leaks from arteriole capillary reabsorbed in the venule side, and lymphatic picks up remaining and return to blood Between IF and ICF across cell membrane - 2 way osmotic flow of water - Ions move selectively; nutrients, waste, glasses unidirectional *in the lungs we need CO2 and O2 to be unidirectional and nutrients within the digestive system(but need to play with H2O and ions to move unidirectional. In the kidney we also want to be able to excrete waste and that is due to the help of renal gradients in the medulla to help with that transportation* Water balance and ECF osmolarity Water intake must=water output 2500mL/day Water intake: beverages, food, metabolic water Water output: urine (60%) insensible water loss (loss through skin and lungs), perspiration, and feces comorbidities : one or more additional conditions that are occurring with primary conditions - Can lead to additional water loss - diarrhea , vomiting, over sweating Maintenance of body fluid osmolarity Osmolarity is maintained at 280-300 mOsm *osmolarity is the number of solutes* Rise in osmolarity(more solute): - Stimulates thirst - ADH release *reads it by the amount of solute concentration at the moment, ADH will help retain water to balance* Decrease in osmolarity(inside cell more fluid): - Thisrt inhibition - ADH inhibition Regulation of water intake *epinephrine and norepinephrine helps with the regulation of bf more than retention* - Thirst mechanism driving force for water intake - Governed by hypothalamic thirst center a. Hypothalamic osmoreceptors detect ECF osmolarity; activated by: - Inc plasma osmolarity of 1-2% - Dry mouth - Dec urine volume or pressure - Angiotensin 11 or baroreceptor input cause : - drinking water inhibits thirst center - Inhibitory feedback signals include a. Relief dry mouth b. Activation of stomach and intestinal stretch receptors (bc you drink water stomach will expand and can communicate with the hypothalamus) *notes of the flowchart* We know that an increased osmolality, will cause the thirst mechanism to activate as well as a drop in bv which causes a drop in bp that will activate the RAAS system and the angiotensin will bind with the whole process Regulation of water output Obligatory water losses - Insensible water loss from lungs and skin(cannot stop sweating) - Feces - Minimum daily water loss 500ml in urine to excrete wastes ADH will help in water output depending on what it detects in osmolarity to inc absorption or decrease. With the help of hypothalamic receptors *ADH adds aquaporins to DCT and collecting duct to absorb more water* *ADH is triggered because of measured solutes NaCl with the help of macula densa(osmoreceptors), and ADH helps to regulate thirst and retain fluids* What can trigger ADH release: - Decrease Bp will inc ADH and activate RAAS - Decreases in bv can also stimulate ADH - Factors lowering Blood volume: sweating, vomiting, blood loss Disorders of water balance Principal abnormalities of water balance - Dehydration - Hypotonic hydration*drinking too much water* - Edema *not moving correctly from IF to ICF* Disorders of water balance: dehydration Negative fluid balance - ECF water loss: due to hemorrhage, burns, vomiting, diarrhea, endocrine imbalances (post pit or hypothalamus that produce hormones) Signs and symptoms: - Cottony oral mucosa, thrist, dry skin, oliguria (less than 500mL of urine) Can lead to: - Weight loss, fever, confusion, loss of electrolytes Consequences of dehydration: 1. Excessive H2O loss from ECF 2. ECF osmotic pressure rises 3. Cells lose H2O to ECF, cells shrink Disorders of water balance: hypotonic hydration - Overhydration, or water intoxication - Occurs w renal insufficiency, or rapid excess water ingestion - ECF osmolarity decreases> hyponatremia >net osmosis into tissue cells> swelling of cells> severe metabolic disturbances (nausea, muscle cramps)> death - Treated with hypertonic saline Consequences of hypotonic hydration 1. Excessive H2O enters ECF 2. ECF osmotic pressure falls 3. H2O moves into cell by osmosis; cells swell Disorders of water balance: Edema Atypical accumulation of IF> tissue swelling - Results of increases fluid out of blood or decrease fluid into blood - Increase fluid out of blood caused by a. Increased capillary hydrostatic pressure or permeability - Capillary HP increased by incompetent venous valves, blockage of Blood vessels, congestive heart failure - Capillary permeability increased by ongoing inflammatory response (2)Also be caused by the decrease of fluid returning to blood - Imbalance in colloid osmotic pressures; hypoproteinemia (decreased plasma protein levels>low colloid osmotic pressure) a. Fluids fail to return at venous end of capillary beds b. Results from protein malnutrition, liver disease or glomerulonephritis (3) - Also caused by blocked (or surgically removed) lymphatic vessels a. Cause leaked proteins to accumulate in IF b. Increase colloid osmotic pressure of IF draws fluid from blood - Increases diffusion distance for nutrients and oxygen - Results in low blood pressure and severely impaired circulation Electrolyte balance What are electrolytes: - Salts, acids, bases, some proteins  - Electrolyte balance: usually refers only to salt balance - Salts control fluid movement, provide minerals for excitability, secretory activity, membrane permeability - Salts enter body by ingestion and metabolism; lost via perspiration, feces, urine, vomit *hydrostatic pressure caused by water, and osmotic pressure is caused by proteins and electrolytes* Central role of sodium Most abundant cation in ECF - Only cation exerting significant osmotic pressure a. Controls ECF volume and water distribution b. Changes in Na+ levels affect plasma volume, bp, and IF volumes (2) - Na leaks into cells; pumped out against its electrochemical gradient *when Na goes into tube to cause AP, Na needs to be pumped out to maintain balance* *they will leak because they are permeabile, and you might have to use ATP to push Na out* - Na moves back and forth between ECF and body secretions (digestive secretions) - Renal acid-base control mechanisms are coupled to sodium ion transport *uses DCT and collecting duct to reabsorb NaCl and urea* *Na is used to help transport H ions to and from to help with the blood pH and if the levels of sodium change this changes the ability to transport the H and affecting the pH* Regulation of sodium balance - No known receptors that monitor Na levels in body fluids (compartments) - Na water balance is linked to blood pressure and blood volume control mechanisms - Changes in bp or volume trigger neural and hormonal controls to regulate Na content *primarily the hormones being secreted so that the DCT and collecting duct can become more efficient at absorbing Na* Regulation of sodium balance: aldosterone Regardless of aldosterone presence - 65% Na reabsorbed in PCT; 25% reclaimed in nephron loops - Na never secreted into filtrate Water in filtrate follows Na if ADH is present (affects DCT and collecting duct) - Inc Na in urine > increase water loss *all retain fluids* Regulation of sodium balance: ANP Released by atrial cells in response to stretch (inc bp) effects : - Dec bp and bv - Dec ADH, renin, and aldosterone production - Increase excretion of Na and water - Promotes vasodilation directly and also by decreasing production of angiotensin 11 Influence of other hormones: Female sex hormones Estrogen: - inc NaCl reabsorption (like aldosterone)  - It will retain H2O during menstrual cycles and pregnancy progesterone : - Dec Na reabsorption (block aldosterone) - Promotes Na and h2o loss Glucocorticoids - Inc Na reabsorption and promote edema (cushing's syndrome, moon face, too much Na retention) Cardiovascular baroreceptors They alert the brain of increases in blood volume and pressure - Sympathetic nervous system impulses to kidneys decline a. Afferent arterioles dilate b. GFR increases c. Na and water output increases d. Reduced bv and bp Regulation of potassium balance Importance of potassium - Affects RMP(resting membrane potential) in neurons and muscle cells (especially cardiac muscle) - Inc ECF(k)> dec RMP > depolarization >reduced excitability (Ap will occur) - Dec ECF(k)>hyperpolarization and nonresponsiveness hyperkalemia : too much K+ hypokalemia : little K+ Both can disrupt electrical conduction in heart and muscles *Ca+ also can affect the heart, because it affects the heart* (2) Influence of aldosterone - Stimulates K secretion (and Na reabsorption) by principal cells - Adrenal cortical cells directly sensitive to K+ content of ECF a. Increased K in adrenal cortex causes release of aldosterone > K secretion Abnormal aldosterone levels severely influences K+ levels *so in the cause of aldosterone and potassium, what happens is when there is inc levels of K+ aldosterone will be released to get rid of excess K+ in the urine tubules and be excreted as urine, while sodium is being reabsorbed to help with water regulation volume and pressure* Regulation of calcium * hormone regulating Ca, parathyroid(hormone)* 99% of body's calcium in bones - Calcium phosphate salts Ca in ECF important for - Blood clotting - Cell membrane permeability - Secretory activities - Neuromuscular excitability- most important, excitability for neurons and muscles Hypercalcemia: increased Ca+, inhibits neuron and muscles cells hypocalcemia : decreased Ca+ Regulation of anions - Cl- is major anion in ECF a. Help maintain osmotic pressure of blood b. 99% of Cl- reabsorbed under normal pH conditions - When acidosis occurs, fewer chloride ions are reabsorbed - Other anions have transport maximums and excesses are excreted in urine Acid base balance *co2, H are acidic and we can use buffers to balance this* - pH affects all functional proteins and biochemical reactions, so closely regulated - Normal pH of body fluids a. Arterial blood : 7.45 b. Venous blood and IF: 7.35 c. ICF: 7.0 alkalosis or alkalemia: arterial pH greater than 7.45 Acidosis or acidemia: arterial pH less than 7.35 (2) - Most H+ produced by metabolism All produce acids: a. Phosphorus containing protein breakdown releases phosphoric acid into ECF b. Lactic acid from anaerobic respiration of glucose c. Fatty acids and ketone bodies from fat metabolism d. H+ liberated when co2 converted to HCO3- in blood hydrogen ions regulated by: - Chemical buffer systems: rapid; first line of defense - Brainstem respiratory centers: act within 1-3 mins - Renal mechanism: most potent, but require hours to days to effect pH changes Chemical buffer systems System that act to resist pH changes when strong acid or base added - Bind H+ if pH drops; release H+ if pH rises 1. Bicarbonate buffer system(extracellular) 2. Phosphate buffer system (intracellular) 3. Protein buffer system (intracellular/extracellular) Abnormalities of acid base balance All classed as respiratory or metabolic - Respiratory acidosis and alkalosis a. Caused by failure of respiratory system to perform pH balancing role b. Single most important indicator is blood pco2 - Metabolic acidosis and alkalosis a. All abnormalities other than those caused by pco2 levels in blood; indicated by abnormal HCO3- levels Respiratory acidosis and alkalosis Most important indicator of respiratory function if pco2 level - Common cause of acid base imbalances acidosis :  - Due to decrease in ventilation or gas exchange - Co2 accumulates in blood - Characterized by falling blood pH and rising Pco2 Alkalosis: - Common result of hyperventilation often due to stress or pain - Co2 eliminated faster than produced Metabolic acidosis and alkalosis Metabolic acidosis: Low blood pH and HCO3- causes : - Ingestion too much alcohol - Excessive loss of HCO3- - Accumulation of lactic acid, ketosis in diabetic crisis, starvation and kidney failure Metabolic alkalosis: Much less common than metabolic acidosis - Indicated by rising blood pH and HCO3- - Causes include vomiting of acid content of stomach or by intake of excess base Effects of acidosis and alkalosis - Blood pH below 6.8 - depression of CNS- come -death - Blood pH above 7.8-excite of nervous system-muscle tetany, extreme nervousness, convolution, death