lecture 18 - fluids/electrolytes n shit Flashcards
body fluid definition
fluid produced by body and is made up of water and dissolved solutes
what needs regulating in terms of body fluids to maintain homeostasis
volume
distrubution
concentration and pH
% of fluid in adults
55-60%
where is body fluid present? (2)
inside cells (2/3)
outside cells (1/3)
- 80% ISF, 20% blood plasma
only two places for exchange between fluid compartments
plasma membranes of cells
blood vessel walls
fluid balance definition
whenr required amounts of water and solute are present and in correct porportions in body compartments
what main organ maintains fluid balance
kidneys
processes that allow exchange of water and solutes between body fluid compartments
filtration, reabsorption, diffusion, osmosis
how can the body gain water
ingestion
metabolic synthesis (cellular respiration)
water loss should also =
water gain in the body
how can the body lose water
urine
sweat
lungs via water vapour
feces elimination
regulation of body water gain
regulated mainly by the bodies intake of water
if water loss > water gain, what happens
dehydration
what happens during dehydration (4)
osmoreceptors detect increased blood osmolarity
atrial volume receptors detect decreased blood volume
baroreceptors in blood vessels detect decreased blood pressure
(this will trigger the RAA pathway)
neurons in the mouth detect dryness
all of these factors will stimulates the hypothalamus thirst center, which attempts to drive water intake to decrease blood osmolarity, and increase vol and pressure
regulation of water loss in the body
mainly regulated by urine
why does loss of NaCl determine body fluid volume
because water follows solute by osmosis
which hormone mainly regulates water loss
ADH
what 3 hormones regulated renal excretion of sodium and chloride
aldosterone, angiotensin 2, ANP
what happens when water is lost in the body (4)
increased blood osmolarity stimulates osmoreceptors
decreased blood vol stimulates atrial receptors
decreased BP stimulates baroreceptors in vessels
other factor such as pain stress or nausea as well can lead to this:
all of these lead to increased ADH production which causes cells in DCT and collecting duct to be more water permeable, increasing water reabsorption
RAA pathway
decreased BP stimulates kidneys to release renin
renin converts angiotensin from the liver to angiotensin 1
angiontensin 1 is converted to ag2 in teh lungs by angiotensin converting enzyme
stimulates aldosterone production which increases reabsorption of Na and secretion of K in the DCT and collecting duct
angiotensin 2 function
increase Na reabsorption in PCT
stimulate aldosterone production
aldosterone function
increase Na reabsorption and K secretion in DCT/collecting duct
ANP function
decrease Na reabsorption in PCT and collecting duct resulting in increase Na and water excretion to lower BP
natriuresis
increase Na excretion in urine
diuresis
increased water excretion in urine
hypertonic ECF
if teh ECF increases in osmolarity, fluid will leave the ISF and cells with shrink
hypotonic ECF
is ECF decreases in osmolarity, fluid will move into ISF and cells with swell
what happens in teh ECF and ICF after eating a salty meal
cells may crenate
what happens in the ECF and ICF after drinking a lot of water
cells may lyse
water intoxication is caused when
water consumption is faster thatn kidneys can excrete it
or ADH secretion is too high
hyponatremia
the lowering of Na concentration in plasma and interstitial fluid
water intoxication causes:
water ot move into cells via osmosis becuase osmolarity of ECF falls.
causes cells to swell and burst
can lead to seizures or comas is neuronal cells are effected
treated by saline solution
pathway of a typical situation of water intoxication
excessive blood loss, sweating, vomiting, etc
leads to hyponatremia of extracellular fluid (ISF and plasma)
decreased osmolarity of ECF
osmosis of water form ECF into ICF
water intoxication (cells swell)
mental confusion, seizures, coma, possibel death
4 main purposes of electrolytes in the body
control osmosis of water
maintain acid base balance required for normal cellular activites
carry electrical current allowing for action potentials and secretion of hormones and NTs
cofactors required for optimal activities of some enzymes
Na is mainly present in:
plasma and ISF (ECFs)
not much in ICF
K is mainly present in:
ICF
not much in ECFs
mg is present mainly in:
ICF (not a lot but mainly found here)
very low in ECFs
Cl is mainly found:
in ECFs (plasma/ISF)
low in ICF
major ions in ECF are (2)
Na and Cl
major ions in ICF are(2)
K and HPO4
what does blood plasma contain a lot of that ISF contains little of
protein anions
most abundant extracellular ion that accounts for most of the osmolarity of the ECF
sodium
why is it importatn that sodium is abundant in the ECF
critical for action potentials
edema
abnormal accumulation of interstitial fluid
could be due to renal failure (cant excrete Na) or hyperaldosteronism (too much Na reabsorption)
hypovolemia
low blood volume
could be due to inadequate secretion of aldosterone or excessive intake of diuretics
second major extracellular ion
chloride
chloride function in the body (2)
regulate electrical balance across red blood cell membranes
plays a role in forming HCI in stomach
regulation of Cl in the blood
processes that regulate reabsorption o fNa in kidneys indirectly regulate reabsorption of Cl due to na/cl symporters
mostly regulated by aldosterone indirectly
most abundant cation in intracellular fluid
potassium
K function in the body (3)
helps establish resting membrane potential and repolarizes nerve and muscle tissues
helps maintain amount of intracellular fluid
helps regualte pH (transported in exchagne for H)
how is K regualted in the body
mainly thru aldosterone by Na/K pumps
this decreases K as it is secreted by the pumps
abmornal K levels can affect
cardiac and neuromuscular function - can be fatal
called blood hyperkalemia
bicarbinate (HCO3) is present in;
mainly ECF plasma
Bicarbinate function
plasma acid base buffer system (major role)
main regulator of HCO3 levels (how)
kidneys
form more HCO if blood levels are too low and excrete excess in urine if too high
calcium is mainly found:
in ECF
most abundant mineral in the body
functions of Ca (2)
stuctural component of bones and teeth
important role in clotting, NT release, muscel tone and function, and enzyme activity
regulation of Ca in the blood (2)
(what hormones?)
parathyroid hormone
- osteoclast stimulation
- calcitriol production
- increase Ca reabsorption
calcitonin
- inhibits osteoclasts
phosphate in the body
85% exists as calcium phosphate in adults
15% ionized (HPO4,PO4, H2PO)
phostphate functions (2)
present in bones/teeth, phospholipids, ATP, protein, carbs, DNA, RNA
HPO4 acts as a buffer of H in body fluids and urine
phosphate regulation
plasma levels are regulated by PTH and calcitriol
PTH
- stimulate reabsorption of bone which releases phosphate
calcitriol
- increases GI absorption of phosphate
Mg is mainly found
in ICF
Mg functions in the body (3)
important part of bones
activated several enzymes in carb/protein metabolism
important in neuromuscular activity, neural transmission within CNS, and myocardial function
how is Mg regulated in the body
kidneys excrete Mg into urine
overall acid base balance of the body is maintained by controlling what?
the H concentration of body fluids (expecially ECF)
homeostasis of H concentration is vital to
cellular function
normal plasma pH
7.35-7.45
3 major mechanism that regulate pH
buffer systems in body fluids
exhalation of CO2
kidney excretion of H
non volatile acids are a product of
metabolic reactions
these acids must be eliminated
- only way is by kidney excretion other than carbonic acid
method of pH regulation - kidney excretion
slowest
excreted non volatile acids
only way to eliminate acids other than carbonic acid
- important role played by intercalated cells in collecting duct and tubular cells in PCT
kidney regulation of pH
kidneys have Na/H antiporters as well as H pumps which secrete H ions into filtrate
syntehsize new HCO3 and reabsorp filtered HCO3 to keep levels up
overall
- low pH = excrete H
- high pH = excrete HCO3
what cells secrete HCO3 in teh kidneys
tubular cells in PCT and Intercalated cells in collecting duct
acidosis
blood pH below 7.35
alkalosis
blood pH above 7.45
respiratory acidosis and alkalosis are
disorders of Pco2 in systemic arterial bloodm
metabolic acidosis and alkalosis are
disorders of bicarbonate concentration in systemic arterila blood
respiratory vs metabolic acidosis and alkalosis
respiratory
- disorder of Pco2
metabolic
- disorders of bicarbonate concentration
compensation refers to
physiological response to an acid base imbalance that attempts to normalize pH
respiratory compensation
hyperventilation or hypoventilation to correct pH due to metabolic imbalance
renal compensation
changes in secretion or reabsorption of H and HCO3 due to respiratory imbalance
respiratory compenstation can correct altered blood pH due to
metabolic causes
renal compensation can correct blood pH changes due to
respiratory causes
respiratory acidosis
cause is elevation of Pco2 above 45mmHg
due ot lack of removal of CO2 form blood, decreasing pH
possible causes of respiratory acidosis
emphysema, pulmonary edema, brain injury to respiratory centres, airway blockage
how does renal compensation fix respiratory acidosis
by increasing secretion of H and reabsorption of HCO3 to increase blood pH
treatment of respiratory acidosis
ventilation therapy to increase exhalation of CO2
IV administration of bicarbonate
metabolic acidosis
when arterial HCO3 concentration is too low, decreasing pH
causes of metabolic acidosis
excessive loss of HCO via kidney dysfunction
accumulation of acid
kidney failing to remove H ions
how does respiratory compensation fix metabolic acidosis
hyperventilation
this gets rid of CO2 to increase blood pH
metabolic alkalosis
arterial HCO3 conc too high, increasing blood pH
possible causes of metabolic alkalosis
vomiting (loss of HCl)
gastric suctioning
excessive intake of alkaline drugs
how does respiratory compensation fix metabolic alkalosis
hypoventilation
treatment for metabolic alkalosis
fluid and electrolyte therapy
RIch MDs acronym
RIch MDs
respiratory = inversely proportional
metabolic = directly
metabolic acidosis characteristic on table
directly proportional
low pH
low HCO3
overproduction/ingestion of H+
respiratory acidosis characteristic on table
inversely proportional
low pH
high HCO3
hypoventilation
- inhibition of respiratory centre
- airway obstruction
- gas exchange disorder
metabolic alkalosis characteristic on table
directly proportional
high pH
hihg HCO3
loss of H, gain of HCO3
respiratory alkalosis characteristic on table
inversely proportional
high pH
low HCO3
hyperventilation
- stimulation of respiratory centre
- mechanical ventilation
