chapter 27: fluid, electrolyte, pH balance Flashcards
what ions from dissociated compounds will conduct an electrical charge in the solution?
electrolyte
why, on average, does a male body contain more water than a female body?
males more muscle, which contains more water than adipose tissue
most of the water in your body is where?
inside cells (intercellular fluid)
what is the most common positively charged ion in the extracellular fluid?
sodium
water will always move between ICF and ECF by what?
osmosis
what does ‘high osmotic concentration’ mean?
many solutes, osmotic draw for water
antidiuretic hormone release is controlled by osmoreceptors where in the brain?
hypothalamus
a decline in the kidney filtrate osmotic concentration at the distal convoluted tubule can trigger the release of what from the adrenal gland?
aldosterone
someone with Addison’s disease will lose a lot of what 2 things in the urine?
NaCl & water
what are released in response to stretching of
the heart and will block the release of ADH & aldosterone?
natriuretic peptides
what is insensible perspiration?
evaporation through the skin (NOT beads of sweat from sweat glands, that’s sensible perspiration)
how do your cells make water?
dehydration synthesis reactions & aerobic cellular respiration
what is the condition of low sodium ions in the body fluids & can lead to water intoxication?
hyponatremia
how are sodium ions typically lost from the body?
urine & perspiration
why can consuming a bunch of salt increase your blood pressure?
water follows salt: salt absorbed into the blood from the digestive tract will become an osmotic draw for water to leave your cells & move to the blood thus increasing blood volume and then pressure
where are most of the potassium ions in your body located?
inside cells
what happens to the levels of potassium ions in your blood when your blood becomes acidic?
potassium ion levels will rise
what happens to the levels of potassium ions in your blood when you have a lot of aldosterone floating around?
potassium ions levels will fall
hyperkalemia can lead to flaccid paralysis & what else?
cardiac arrhythmia
what is the most abundant mineral in the body?
calcium
name the hormone that functions to lower blood calcium levels?
calcitonin
what function do Chloride ions have in the body?
there isn’t one, it’s just typically the other half of NaCl
what is a substance that dissociates to release protons?
acid
what functions to absorb protons to stabilize pH?
buffer
what enzyme in erythrocytes functions to create
bicarbonate ions?
carbonic anhydrase
excess protons are removed from the body either as water in the lungs or as
protons at what organ?
kidney
any condition that prevents lung function of the flow of blood to the lungs will lead to respiratory what?
acidosis
hyperventilation will cause respiratory what?
alkalosis
what illness/condition can lead to metabolic alkalosis?
extreme vomiting (or a steady diet of antacids)
extracellular fluid (ECF)
interstitial fluid, plasma, lymph, CSF, synovial fluid, serous fluid, etc.
intracellular fluid (ICF)
cysotol
fluid balance (stabilizing ECF & ICF)
must have equal gain (food & metabolism: water made by body chemistry) & loss (urine & perspiration) of water
electrolyte balance (stabilizing ECF & ICF)
must have equal gain (absorption in GI) & loss (urine in kidney & perspiration in skin)
electrolytes
ions from dissociated compounds that will conduct an electrical charge in solution
acid-base balance (stabilizing ECF & ICF)
the production of hydrogen ions by metabolism must be matched by loss of these H+ ions in the kidney (protons: H+) & lungs (carbonic acid)
fluid & electrolyte balance (water & ions move together):
- average male ~60% H2O (more muscle which can be ~75% H2O)
-average female ~50% H2O (more adipose which is only ~10% H2O)
-most of the water in body found in ICF (~2/3)
although different ions dominate, both fluid divisions have the same osmotic conc.:
-ions cant pass freely through cell membranes, but water can by osmosis & equilibrium
- solute/electrolyte concentrations of fluid divisions will directly impact water distribution
principal cation & anions in ECF:
principal cation = Na+
principal anions = Cl-, HCO3-
principal cation & anions in ICF:
principal cation = K+, Mg2+
principal anions = HPO4 & negatively charged proteins (phosphates)
all homeostatic mechanisms for fluid composition responds to changes in ECF (1st rule of regulation of fluids):
-receptors monitor the composition of plasma & CSF and trigger neural & endocrine mechanisms in response to change
- individuals cells cannot be monitored & thus ICF has no direct impact
no receptors directly monitor fluid or electrolyte balance (2nd rule of regulation of fluids):
only plasma volume & osmotic conc. are monitored, which gives an indirect measure of fluid or electrolyte levels
“water follows salt” (3rd rule of regulation of fluids):
-cells can’t move water by active transport
-water will always move by osmosis & this movement can’t be stopped
the body’s content of water or electrolytes rises & falls with gain & loss to and from environment (4th rule of regulation of fluids):
-too much intake = high content in body
-too much loss = low content in body
antidiuretic hormone (ADH) (primary regulatory hormone)
-osmoreceptors in hypothalamus monitor ECF & release ADH in response to high osmotic conc. (low water, high solute)
-↑ osmotic conc. = ↑ ADH levels
what are the primary effects of ADH? (primary regulatory hormone)
a) stimulate water conservation at kidneys
b) stimulate thirst center
aldosterone (primary regulatory hormone)
-released by adrenal cortex to regulate Na+ absorption & K+ loss in DCT & collecting system in kidney
-retention Na+ will result in H2O conservation
when is aldosterone released in response to? (primary regulatory hormone)
a) high K+ or low Na+ in ECF (renal circulation)
b) activation of renin-angiotensin system due to a drop in BP or blood volume
c) decline kidney filtrate osmotic conc. at the DCT (more water loss than solutes)
addison’s disease
hypoaldosteronism
-results in massive loss of NaCl & H2O in the urine; must adjust diet to compensate
natriuretic peptides (primary regulatory hormone)
- ANP (atrial) & BNP (brain) are released in response to stretching of heart wall
-function to reduce this & block release of ADH & aldosterone, resulting in diuresis
diuresis
fluid loss in kidney
fluid movement within the ECF (fluid balance)
two important divisions: plasma (~20%) & interstitial fluid (~80%)
what is the continuous flow between plasma & interstitial fluid? (fluid movement in ECF -> fluid balance)
a) hydrostatic pressure pushes water from the plasma into interstitial fluid
b) colloid osmotic pressure draws water leaves the plasma & accumulates in interstitial fluid
edema
abnormal amount of water leaves the plasma & accumulates in interstitial fluid
water loss (fluid exchange with environment -> fluid balance)
~2500 mL/day in urine, feces & insensible perspiration = obligatory water loss
- sensible perspiration: can reach up 4L/hr under extreme conditions
- fever: for each degree rise, insensible perspiration will increase by 200mL/day
water gains (fluid exchange with environment -> fluid balance)
-must match water losses or dehydration will result
-typical gain:
~1000 mL from drink
~1200mL from food
~300mL metabolic “waste”
-water not easily measure, so ion content, particularly Na+ is measured & regulated
when does metabolic generation of water occur?(water gains -> fluid exchange with environment -> fluid balance)
from dehydration synthesis reactions & aerobic respiration in mitochondria: water is the waste product of those reactions
hyponatremia
hypotonic hydration
-condition of low Na+ concentration (ie. excess water)
what causes hyponatremia?
1) ingestion of a large volume of freshwater or injection of hypotonic solution
2) inability to eliminate excess water at kidney
3) endocrine disorder (eg. too much ADH)
what is the result of hyponatremia?
cerebral edema & CNS dysfunction
-water moving from ECF to ICF causing cellular damage = “water detoxification”
hypernatremia
dehydration
-condition of high Na+ conc. (i.e., water depletion)
what is the result of hypernatremia?
decreased plasma volume & blood pressure that can lead to hypovolemic shock (inadequate circulation)
fluid shifts (fluid balance)
movement of water will occur between ECF & ICF due to changes in osmotic concentrations
water will always come to equilibrium (fluid shifts -> fluid balance):
-if osmotic conc. of ECF ↑ (hypertonic) due to loss of water but not electrolytes, water will leave ICF
-if osmotic conc. of ECF ↓ (hypotonic) due to gain of water but not electrolytes, water will enter ICF
total amount of water is greater in ICF than ECF (fluid shifts -> fluid balance):
this allows ICF to act as a reserve to accommodate changes in ECF until hormones can restore homeostasis
why is electrolyte balance important?
1) total electrolyte conc. directly affects water balance
2) conc. of individual electrolytes can affect cell functions
- 2 most important electrolytes are sodium & potassium
sodium balance (electrolyte balance)
-normal blood values: 130-145
-Na+ is the dominant cation in ECF
-90% of ECF osmotic conc. is due to sodium salts
-total mount of Na+ in ECF is due to balance between Na+ uptake in digestive system & Na+ excretion in urine & perspiration
what are the 2 sodium salts involved in ECF osmotic conc.?
NaCl & NaHCO3
overall sodium conc. in body fluid rarely changes because water always moves to compensate (sodium balance -> electrolyte balance):
high sodium levels in blood will cause retention of water to maintain the same Na+ conc., but this results in high blood volume (why salt is bad for hypertensive patients)
minor gains & losses of Na+ in ECF are compensated by water in ICF & later adjusted by hormonal activities (sodium balance -> electrolyte balance)
-ECF volume too low -> renin-angiotensin system activated to conserve water & Na+
-ECF volume too high -> natriuretic peptides released: block ADH & aldosterone resulting in water & Na+ loss
potassium balance (electrolyte balance)
-normal blood values: 3-5-5.5
-K+ dominant cation in ICF (98%)
-conc. of K+ in ECF depends on absorption in GI vs. excretion in urine
- exchange pump at kidney tubules secrete K+ (or H+) in order to reabsorb Na+
the rate of tubular secretion of K+ in kidney is controlled by three factors (potassium balance -> electrolyte balance):
- changes in K+ conc. of ECF
- ↑ K+ in ECF =↑ K+ secretion - changes in blood pH
-at low pH, H+ is used for Na+ reabsorption instead of K+ at exchange pump
- ↓ pH in ECF = ↓ K+ secretion - aldosterone levels
- ↑ aldosterone = ↑ Na+ reabsorption & ↑ K+ secretion
hypokalemia
low K+ conc. in ECF, will cause muscular weakness & mental confusion
what are the causes of hypokalemia?
- inadequate dietary K+ intake
- some diuretic drigs
- excessive aldosterone
- increased pH of ECF
hyperkalemia
high K+ conc. in ECF will cause cardiac arrhythmia & flaccid paralysis
what are the causes of hyperkalemia?
- renal failure
- diuretic that block Na+ reabsorption
- decline in pH
calcium balance (electrolyte balance)
-normal blood values: 4.5-5.8
-Ca2+ most abundant mineral in the body
-99% is located in the skeleton for structure
-Ca2+ homeostasis involves interplay between skeletal reserves, uptake at the GI, & loss at the kidney
-parathyroid hormone & calcitriol function to raise blood Ca2+ levels
-calcitonin functions to lower blood Ca2+ levels
why is calcium (Ca2+) so important? (electrolyte balance)
-muscular & neural cell activities
-blood clotting
-a cofactor for enzymes
-a second messenger (intercellular signaling)
hypercalcemia
-high Ca2+ concentration in ECF: can be due to
hyperparathyroidism or cancers
-can cause fatigue, confusion,
cardiac arrhythmia & calcification of organs
hypocalcemia
-low Ca2+ concentration in ECF: can be due to
hypoparathyroidism, VitD deficiency, or renal failure
-can cause muscle spasms, convulsions, weak heartbeats, reduced
clotting & osteoporosis
magnesium balance (electrolyte balance)
-normal blood values: 1.4-6
-most Mg 2+ is located in skeleton
-remainder is located in ICF
-Mg 2+ is important as a cofactor for enzymes & a structural component of the skeleton
-excess can cause lethargy & coma
-insufficient magnesium can cause convulsions
phosphate balance (electrolyte balance)
-normal blood values: 1-6
-free phosphate (HPO42- ) is found in ICF
-phosphate tends to accompany calcium, so physiological effects of
excess or deficiency are related to calcium levels
what is phosphate used for in the body? (electrolyte balance)
-mineralization of bone
-formation of high energy compounds (ATP)
-cofactors for enzymes
-synthesis of nucleic acids
chloride balance (electrolyte balance)
-normal blood values: 95-105
-Cl- is abundant anion in the ECF
-body has no use for it other than the fact that it travels with Na+
-excess can cause metabolic acidosis
-Deficiencies can cause metabolic alkalosis
acid
a substance that dissociates to release H+
base
a substance that dissociates to release OH- ions or absorbs H+ ions
pH
-potential of hydrogen
-water is neutral: H+ = OH-
-basic or alkaline solution (pH 7-14) has more OH - than H+
acid-base balance
-pH scale is used to measure the concentration of H+ ions in a solution
-strong acids or bases dissociate completely in solution (e.g. HCl → H + + Cl- )
-weak acids or bases do not completely dissociate: many molecules remain intact
(e.g. H 2 CO 3 )
what is the normal pH of the ECF? (acid-base balance)
-7.35 – 7.45.
-above or below this range will disrupt cell membranes & denature proteins
-acidosis = ECF pH below 7.35
alkalosis = ECF pH above 7.45
-acidosis more common problem since metabolism generates acid waste products
volatile acids (type of acid -> acid-base balance)
can leave solution and enter the atmosphere
-e.g. CO 2 + H 2 O ↔ H 2 CO 3 ↔ H + + HCO 3
-lungs -> blood
fixed acids (acid type -> acid-base balance)
remain in solution until they are excreted
-e.g. sulfuric acid, phosphoric acid
organic acids (acid type -> acid-base balance)
products of metabolism
-usually metabolized into other wastes, but can build up under anaerobic conditions or starvation
-e.g. Lactic acid, Ketone bodies
buffers (mechanism of pH control -> acid-base balance)
dissolved compounds that can remove H+ ions to stabilize pH
-buffers are a weak acid & its corresponding salt
-three major buffering systems: protein, carbonic acid-bicarbonate & phosphate systems
protein buffer system (buffer-> mechanisms of pH control -> acid-base balance)
proteins are used to regulate pH in ECF & ICF (most effective in ICF)
amino acids can be used to accept or release H+ ions (protein buffer system -> buffer-> mechanisms of pH control -> acid-base balance):
-at typical body pH, most carboxyl groups exist as COO- & can accept H+ ions if pH drops
-histidine & cysteine remain as COOH at normal pH & can donate H+ if pH rises
-most proteins provide some degree of buffering with carboxyl terminal
what are the effects of hemoglobin on blood pH? (hemoglobin (Hb) buffering system -> protein buffer system -> buffer-> mechanisms of pH control -> acid-base balance):
-most effective in ECF: blood
-in RBCs, the enzyme carbonic anhydrase converts CO2 into H2CO3 which then dissociates
-H+ remains inside RBC, but HCO3- enters plasma where its absorb excess H+
carbonic acid-bicarbonate buffer system (buffer-> mechanisms of pH control -> acid-base balance)
-most important buffer for ECF (in plasma or Hb)
-carbon dioxide & water from carbonic acid which dissociates into hydrogen ions & bicarbonate ions
-bicarbonate ions can be used to absorb H+ ion in ECF & can be released as CO2 & H2) at lungs
when does the carbonic acid-bicarbonate buffer system work? (buffer-> mechanisms of pH control -> acid-base balance)
- CO2 levels are normal
- respiration is functioning normally
- free bicarbonate ions are available
-bicarbonate ions can be generated from CO2 + H2O or NaHCO3- but have free HCO3-, H+ ions must be excreted at kidney
phosphate buffer system (buffer-> mechanisms of pH control -> acid-base balance)
-phosphate is used to buffer ICF & urine
-H2PO4 or NaPO4 can dissociate to generate HPO4-2, which can absorb H+ (as above, only as long as H+ is excreted at kidney)
maintenance of acid-base balance (acid-base balance)
buffering will only temporarily solve H+ problem: permanent removal as H2O at lungs or through secretion at kidney necessary to maintain pH near neutral
respiratory compensation (pH homeostasis -> maintenance of acid-base balance)
-respiration rate is altered to control pH
-↑ CO2 = ↓ pH
-↓ CO2 = ↑ pH
renal composition (pH homeostasis -> maintenance of acid-base balance)
-the rate of H+ & HCO3- secretion or reabsorption can be altered as necessary
- ↑ H+ = ↓ pH
- ↓ HCO3- = ↑ pH
factors that disturb the acid-base balance:
a) disorders of buffers, respiratory problems or renal function
b) cardiovascular conditions that alter blood flow to lungs & kidney
c) CNS disorders that effect cardiovascular or respiratory reflexes
respiratory acidosis (disturbance of acid-base balance)
respiratory system fails to eliminate all CO2 generated by peripheral tissues causing decline in pH
-caused by cardiac arrest, emphysema, CHF, pneumonia, pneumothorax, etc.
respiratory alkalosis (disturbance of acid-base balance)
lungs remove too much CO2 causing an ↑ in pH
-result of hyperventilation due to anxiety or pain: usually corrects itself
what are the 3 causes of metabolic acidosis (disturbance of acid-base balance)?
- production of fixed or organic acids: lactic acidosis & ketoacidosis
- impaired ability to excrete H+ at kidney (diuretics)
- severe bicarbonate loss eg. diarrhea: buffering agents from intestinal secretions are lost before they can be reabsorbed
lactic acidosis (metabolic acidosis -> disturbance of acid-base balance)
results from hypoxia & usually linked to respiratory acidosis
ketoacidosis (metabolic acidosis -> disturbance of acid-base balance)
results from starvation or diabetes mellitus
metabolic alkalosis (metabolic acidosis -> disturbance of acid-base balance)
-rare condition, caused by ↑ HCO3-
-secretion of HCl in stomach releases HCO3- in ECF
- severe vomiting causes continuous acid production & loss
-corresponding HCO3- then accumulates ECF
-also results from chronic & excessive use of antacids
age-related changes in fluid, electrolyte & acid-base balance
-↓ water content affects solute conc. (elderly ~40% H2O)
-↓ renal compensation (reduced kidney function)
-↓ mineral reserves (Ca2+, Mg2+, HOP42-)
-↓ respiratory compensation (reduced lung function)
