ACID BASE BALANCE Flashcards
WHAT ARE THE BODY WATER CONTENTS OF INFANTS, ADULT MALES AND FEMALES
INFANTS= 73%
adult females= 50% (due to higher fat content and less skeletal muscle mass)
adult males= 60%
WHAT ARE THE MAJOR FLUID COMPARTMENTS, FLUID VOLUMES, AND SOLUTE CONCENTRATIONS
intracellular fluid compartment (ICF): 2/3 contains 25L of fluid
- main cation: K+
- main anion: HPO4 2-
- more soluble proteins than plasma
- inside cells
extracellular fluid compartment (ECF): 1/3
is split into 2 further sections, but has a total fluid volume if 15 L.
- interstitial fluid: 12L, 80% of ECF
- plasma: 3 L, 20% of ECF, contains more proteins and less Cl- content
- main cation: Na+
- main anion: Cl-
WHAT ARE ELECTROLYTES AND NON-ELECTROLYTES, WHAT ARE THEIR AFFECTS ON FLUID SHIFTS
Nonelectrolytes: are substances that do not dissociate in water and create ions. ex. glucose, lipids, creatinine, urea
electrolytes: can dissociate into water and create ions. ex. most acids and bases, inorganic salts, some proteins
electrolytes have an increased power to create fluid shifts because they can create 2 or more ions
EXPLAIN EXCHANGE BETWEEN INTERSTITIAL FLUID AND PLASMA, WHERE DOES IT OCCUR?
- occurs across capaillary walls
- bulk flow
- lymphatics pick up reamaining fluid
EXPLAIN FLUID EXCHANGE ACROSS INTERSTITIAL FLUID AND INTRACELLULAR FLUID COMPARTMENTS. WHERE DOES IT OCCUR? DOES WATER MOVE IN 1 OR 2 WAYS? WHAT ABT IONS AND WASTES?
- happens across cell membrane
- 2 way osmotic flow of water
- ions move selectivley
- nutrients, wastes, and gasses have unidirectional flow
WHAT IS THE RELATIONSHIP BETWEEN WATER INTAKE AND OUTPUT? WHAT CAUSES EACH OF THEM
- water intake must equal water output (2500ml)
- water intake: injested foods and beverages, little amounts from metabolism
- water output: urine (60%), insensible water loss (skin, lungs), perspiration, and feces
WHAT LEVEL IS OSMOLARITY USUALLY MAINTAINED? WHAT DO INCREASES AND DECREASES IN IT CAUSE?
- Is maintained arouns 280-300 oMsm
- rise: thirst and ADH release
- decrease: inhibits thirst and ADH release
HOW IS WATER INTAKE REGULATED? WHAT STIMULATES IT AND WHAT ARE THE EFFECts?
hint: osmo…
- it is regulated by the hypothalamic thirst center.
- osmoreceptors detect ECF osmolality and are triggered by: increased plasma osmolarity (1-2%), dry mouth, decreased blood volume or pressure, angiotensin II or baroreceptor input
drinking water inhibits the thirst center and causes: releif of dry mouth, and activation of stomach and intestinal strech receptors
WHAT ARE OBLIGATORY WATER LOSSES
- they explain why we cannot live long without water
- includes **insensible water losses **through skin, lungs, and feces and sensible water losses through urinating to excrete wastes (depends on urine excreted, solute conc., diet, and water loss in other ways)
WHAT IS INFLUENCE OF ADH ON THE COLLECTING DUCTS AND URINE? how do osmoreceptors relate?
- water reabsorption in collecting ducts is proportional to ADH release
- decreased ADH=dilute urine and drop of body fluid volume lvls
- increased ADH= concentrated urine and increase of body fluid volume lvls
- hypothalmic osmoreceptors detect ECF solute concentration and regulate ADH accordingly
- large changes in blood volume and blood pressure can also impact ADH release
WHAT IS ELECTROLYTE BALANCE? WHAT ARE THE MAIN FACTORS THAT INFLUENCE SODIUM BALANCE. how does salt enter and leave the body
electrolyte balance: often referes to salt balance because they play a crucial role in fluid movements, action potentials, secretions and membrane permeability.
- salt enters by injestion and metabolism and are lost via perspiration, feces, urine, and vomitting
- main factors are influence of aldosterone and angiotesin II, atrial natriuretic peptide, female sex gormones, and cardiovascular baroreceptors
EXPLAIN INFLUENCE OF ALDOSTERONE. WHEN ITS LOW, HIGH, AND NOT THERE
- plays biggest role in Na regulation in kidneys (however if it’s not there 65% is still reabsorbed, and 25% is reclaimed in nephron loops. IS NEVER SECRETED INTO FILTRATE)
-High aldosterone: Na absorbed into DCT and CD, water follows so ECF volume increase - low aldosterone: Na is not activley reabsorbed and is lost in the urine alongside increase loss of water
aldosterone also triggered by high K+, its affects r slow (hours to days
EXPLAIN THE EFFECTS OF ANGIOTENSIN II
Hint: think back to causes for release of renin from granular cells
- is the main trigger for aldosterone release
- remember, granular cells secrete in response to strech, sympathetic stimulation, or low Nacl content
- renin causes production of angiotensin II, which releases aldosteron, whuch increase Na reabsorption in kidneys
AFFECT OF ATRIAL NATRIUETEIC HORMONE, WHAT ITS REELEASED BY AND IT’S EFFECTS
- released by atrial cells in response to strech caused by increased BP
- decreased blood pressure and volume by inhibiting ADH
- causes excretion of NA+ and water
- promotes vasodilation directly and by also decreasing production of angiotensin II
EXPLAIN INFLUENCES FROM FEMALE SEX HORMONES (estrogen, progesterone, glucocorticoids)
Estrogen: increased Nacl absorption (like aldosterone) to have increase water retention during periods and pregnancy
progesterone: blocks aldosterone, causing decreased Na+ reabsorption and H2O loss
glucocorticoids: increase Na+ reabsorption and promotes edema
EXPLAIN CARDIOVASCULAR BARORECEPTORS IMPACT ON Na
- baroreceptots increase blood volume and pressure
- sympathetic impulses to kidneys decline causing: affarent arterioles dilate, GFR increase, increased NA and H2O output, and reduced blood volume and pressure
WHY IS IT IMPORTANT THAT POTASSIUM IS BALANCED? WHAT IS IT CALLED IF THERE IS TOO MUCH OR TOO LITTLE OF IT
- balancing pottasium is important to maintain RMP
- increased K+=hyperkalemia=decreased RMP causing depolarizations and reduced excitability
- decreased K+=hypokalemia=hyperpolarization and nonreponsiveness
disruption of K+ can interfere with the hearts electrical conduction and cause sudden death!
HOW DOES K+ REGULATE PH?
K+ maintains cation balance when H+ shifts in and out of cells.
- ECF K+ levels rise with acidosis
- ECF K+ levels drop with alkanosis (interferes with excitability of cells)
WHERE IS K+ SECRETIONS AND ABSORPTION REGULATED? IS IT EFFICENT IN THE KIDNEYS?
- regulate in the collecting ducts of cortical nephrons
- high K+ in ECF=secretion of K+
- low K+ in ECF= reduce secretion of K+as much as possible
- however, kidneys have a limited ability to retain K+ and much of it is lost, so it may lead to defiency if not taken in with diet
WHAT IS THE BIGGEST INFLUENCE OF K+ IIN THE BODY? HOW DOES DIET IMPACT IT?
- concentration of K+ in the ECF is the most important factor affeting it’s secretion
- High K+ diet=increased K+ in ECF=K+ enters cell and secretion is increased
- Low K+ diet or accelerated K+ loss reduces it’s secretion and promotes its limited reabsorption
WHAT IS THE INFLUENCE OF K+ FROM ALDOSTERONE? and adrenal cortex
- aldosterone promotes K+ secretion
- adrenal cortex cells are sensitive to K+ in ECF, so it will release aldosterone and increase K+ secretion
HOW IS REGULATION OF CALCIUM AND PHOSPHATE DONE? WHERE IS MOST OF IT FOUND
- most calcium is found in the bones and in calcium phosphate salts
- calcium balance is controlled by **parathyroid hormone ** (eats at bones) which means low calcium causes increases PTH
WHAT IS CALCIUM IMPORTANT FOR? WHAT IS AN INCREASE AND DECREASE IN CALCIUM LVLS CALLED?
- blood clotting
- cell membrane permeability
- secretory activities
- neuromuscular activities MOST IMPORTANT
Hypocalcemia: increasd excitability in muscles=tetanus
hypercalcemia: inhibits neurons and muscle cells and may cause arrythmias
WHAT IS THE NORMAL PH OF BODY FLUIDS? WHAT IS CLASSIFIED AS ACIDOSIS AND ALKANOSIS
ARTERIAL AND VENOUS BLOOD, ICF
Arterial blood: Ph 7.4
venous blood: ph 7.35
ICF: 7.0
alkanosis: PH>7.45
acidosis: ph<7.35
WHAT ARE THE 3 MAIN BUFFER SYSTEMS IN THE BODY
- chemical buffers: 1st line of defense
- brain stem respiratory centers: act within 1-3 mins
- renal mechanisms: most potent but take hours or days to take effect
WHAT ARE THE 3 CHEMICAL BUFFER SYSTEMS
- Bicarbonante buffer system
- phosphate buffer system
- protein buffer system
HOW DOES THE PHOSPHATE BUFFTER SYSTEM WORK WHAT IS IT MOST EFFECTIVE AT BUFFERING
- works similar to bicarbonate
- weak acid is H2PO4-
- weak base is HPO42-
- it is unimportant for buffering plasma and is better at buffering urine and ICF where phosphate concentrations are high
EXPLAIN RESPIRATORY REGULAITON OF H+, SPECIFICALLY DURING CO2 LOADING AND UNLOADING
- acts slower than chemical buffers but is more potent.
- also uses the bicarbonate buffer system formula
- H2O+ CO2 = H2CO3 = HCO3- + H+
- during Co2 unloading the reaction shifts to the left
- during co2 loading reaction shifts to the right
HOW DOES PCO2 AND H+ INCREASING AFFECT THE REACTION
rising PCO2 triggers medullary chemoreceptors, and rising H+ (acidosis) triggers peripheral chemoreceptors. this increases rate of depth of breathing, which means more CO2 is being removed so the reaction shifts to the left reducing H+ concentration.
HOW DOES ALKANOSIS, HYPER AND HYPO VENTILATION IMPACT ACID-BASE BALANCE
alkanosis: depresses resp centers letting H+ accumulate
hyperventilation: ** respiratory alkanosis**
hypoventilation: **respiratory acidosis **
HOW DO KIDNEYS REGULATE ACID BASE BALANCE?
- by adjusting the amount of bicarbonate in the vlood by either conserving or reabsorbing HCO3 or excreting it.
getting rid of 1 HCO3 is = to gaining 1 H+
HOW IS ALKALINE RESERVE MAINTAINED IN THE KINDEYS?
because tubular cells are impermeable to HCO3 but are permeable to CO2, HCO3 can take a short cut and CO2, once back in the cell it can convert back into HCO3 or just leave the cell of CO2. mechanism is coupled with H+ secretion.
HOW CAN THE KIDNEY GENERATE NEW BICARBONATE IONS
- excretion of buffered H+ via HPO4 2-
- via glutamine metabolism and NH4+ secretion
HOW DOES EXCRETION OF BUFFERED PH GENERATING NEW BICARBONATE IONS WORK?
- most important urine buffer in system
- Collecting duct cells secrete H+ into urine which is buffered by phosphates, new HCO3 and moves into interstsitial space via cotransport system, and then moves passively into peritubular blood
HOW DOES GENERATING NEW BICARBONATE IONS VIA GLUTAMINE METABOLISM AND NH4 SECRETION WORK
- most important system for excreting acid
- involves metabolism of glutamine: produces 2 NH4+ and 2 “New” HCO3-. the HCO3 will move into the blood and NH4+ into the urine. this replenishes alkaline reserve in the blood
WHEN THE BODY IS IN ALKANOSIS WHAT CAN THE CD CELLS DO?
- secrete HCO3- or recalim H+ to acidify blood. mechanism is oposite to bicarbonate ion reabsorption
WHAT IS RESPIRATORY ACIDOSIS AND ALKANOSIS? WHAT CLASSIFIES BOTH OF THEM
RESP ACIDOSIS AND ALKANOSIS: faliure of respiratory system to be a buffer. main determinenent is blood PCO2
acidosis: PCO2 above 45 mm/hg. usually caused form acid-base imbalancr or decreased ventilaiton or gas exchange (pneumonia, cystic fibrosis, etc)
alkanosis: PCO2 below 35 mm/hg. usually caused by hyperventilation (stress or pain). CO2 is eliminated faster than it can be produced.
WHAT IS METABOLIC ACIDOSIS AND ALKANOSIS? WHAT CLASSIFIES BOTH OF THEM
- all abnormalities other than those caused by PCO2 lacking being a buffter. is indicated by HCO3 levels.
acidosis: low ph and HCO3, can be caused by alcohol (acetic acid), diarreah causing alot of HCO3 loss, and accumulation of lactic acid, ketosis, starvation, and kidney faliure
alkanosis: rising ph and HCO3. vomitting acid content of stomach or excessive base intake (antacids)
WHAT ARE RESPIRATORY COMPENSATIONS FOR ACIDOSIS AND ALKANOSIS
metabolic acidosis: increasing rate and depth of breathing to let out more CO2. indicated by < 7.35 ph and PCO2 > 45
metabolic alkanosis: decreasing breathing to shallow breathing to let CO2 accumulate. indicated by ph >7.45, and PCO2 < 35
WHAT ARE SOME RENAL COMPENSATIONS FOR ACIDOSIS AND ALKANOSIS
** respiratory acidosis**: absorbing more HCO3 and secreting more H+. indicated by < 7.35 ph and PCO2 > 45
respiratory alkanosis: kidneys excrete more HCO3. indicated by ph >7.45, and PCO2 < 35
WHAT ARE SOME THINGS BOTH SYSTEMS CANNOT COMPENSATE FOR
respiratory system cannot compensate for respiratory acidosis or alkanosis. renal system can only compensate for resp alkanosis and acidosis
