extracellular fluid Flashcards
what is ECF
all the fluids outside the cells
(in constant motion thru body)
extracellular fluid
what does extracellular fluid contain
- ions and nutrients to maintain life
what 5 things are found in the phospholipid bilayer + (percentage make up)
- proteins 55%
- phosphloipids 25%
- cholesterol 13%
- other lipids 4%
- carbs 3%
what is the role of lipids in the phospholipid bilayer
- provide barrier preventing movement of water and water-soluble substances
role of proteins in phospholipid bilayer?
provide specific pathways for passage of substances
what are the 3 means of transport through a membrane
active transport
facilitated trasnport
diffusion
describe active transport, facilitated diffusion, diffusion
active transport = against conc gradient, movement of ions using Na+/K+ pump and sodium/glucpse symport protein (protein carriers) uses ATP
facilitated diffusion = down conc gradient, ion movement with help of channel/carrier protein
diffusion = movement of molecules down conc gradient
What criteria of molecules can diffuse thru membranes
- small hydrophobic e/g o2
- small uncharged e.g h10
why can glomerulus allow passage of molecules with slightly bigger size compare to regular cell membran
has bigger pores allowing passage of substances with Mol WT of up to 55-60000
define osmolarity
concentration of a solution expressed as the total number of solute particles per litre.
(a number of osmoles per kg of solvent)
( number of active particles per unit volume (not size))
what is osmosis
a process by which molecules of a solvent tend to pass through a semipermeable membrane from a less concentrated solution into a more concentrated one till equilibrium is reached
quantifying osmolairt:
number of osmoles of substance in 1L of solution
1 mole provides 1 osmole if the molecules remain unchanged in solution
80% of the total osmolarity of the interstitial fluid and plasma is due to what
Na+ and Cl- (NaCl)
if the solute dissociates into ions, they each become osmotically active
plasma osmolarity is 280-290 mOsm/L, how does this effect administration of IV fluids
most fluids that are administered via IV must have same osmolarity as plasma to prevent water movement/shifting
how is a cell affected if placed in isotonic, hypertonic or hypotonic solution
isotonic = no change
hypertonic = shrinks
hypotonic = swells
what percentage of human body is fluid and what fraction of this is intracellular or extracellular fluid
60%
2/3 = intracellular
1/3 = extracellular
(remaining 40% = bones and tissue)
For a 70kg person:
ICF = 25L
IF = 12L
Plasma = 3L
these proportions change with age, gender and degree of obesity
how much water is lost thru the skin and lungs dailyq
700ml
fluid composition differs in interstitial, plasma and intracellular fluid.
What is the majority 2 ionic components found in each of them
interstitial = Na+ (140g/L) and Cl- (115)
plasma = Na+, Cl-
intracellular = K+ (140) and HPO4 2- (100)
(vast majority of osmolarity in ECF made by NaCl)
compare fluid composition of ECF and ICF
ECF = NaCL, bicarbonate, o2, glucose, fatty acids and amino acids
ICF = K+, Mg2+ and phosphate ions
what structure responds as a result of too high or low osmolarity
hypothalamus
- repsons to changes of 2-3 moles or 350ml
what is osmoregulation Brought about by
Osmoregulation is the active regulation of the osmotic pressure of an organism’s body fluids, detected by osmoreceptors, to maintain the homeostasis of the organism’s water content;
- alterations in WATER content of urine
- changing degree of thirst
what hormone is used in osmoregulation
ADH (vasopressin)
urine can vary form 300ml/day (very concentrated) to 10L/day (very dilute)
what 2 hypothalamic osomoreceptors are involved in osmolarity homeostasis
supraoptic and paraventricular nuclei
and
lateral preoptic area
how does the supraoptic and parventricular nuclei (hypothalamic osmoreceptor) work to increase water absorption when there is high ECF osmolarity
- ADH released from posterior pituitary
- collecting duct made water permeable
- water retention by kidney
how does the lateral preoptic area work to increase water absorption when there is high ECF osmolarity
- makes you thirsty
- drink water
how does the supraoptic and parventricular nuclei (hypothalamic osmoreceptor) work to decrease water absorption when there is low ECF osmolarity
- ADH release supressed
- Collecting duct made impermeable
- water excretion by kidney
how does the lateral preoptic area work to decrease water absorption when there is low ECF osmolarity
thirst surpassed
where is ADH made and what releases its
- made in hypothalamus
- pituitary gland releases it into bloodstream
what 2 other things can stimulate ADH release besides osmoreceptors
- nicotime
- angiotensin II (apart of shock response)
what 2 things can inhibit ADH release
- alcohol
- ANP Atrial natriuretic peptide
what is ANP/atrial natriuretic peptide
a cardiac hormone that regulates salt-water balance and blood pressure by promoting renal sodium and water excretion and stimulating vasodilation.
the volume of ECF is determined by the total quantity of solute (mainly Nacl) so the regulation of ECF fluid is all about?
sodium balance
note where Na+ leads, water follows
Glomerular filtration is used as a major regulator of what 2 tings
- cardiovascular system
- body fluid volume
the juxtaglomerular apparatus is located between afferent arteriole and distal convoluted tube,
decrease in pressure in afferent arteriole and decrease tubular Na+ flow in DCT is sensed by what in each stucute
afferent arteriole : decrease in pressure sensed by GRANULAR CELLS
DCT : decrease tubular Na+ flow sensed by MACULA DENSA cells
what is the juxtaglomerular apparatus innervated by
sympathetic fibres (part of baroreceptor response)
what hormone increase Na+ reabsorption in DCT (and gut, sweat/salivary glands)
aldosterone
where is aldosterone produced
adrenal glands
what 2 thing does aldosterone stimulate
- channel synthesis (increase Na+ reabsorption/ K+ excretion)
- pump activity (to keep intracellular Na+)
besides aldosterone, what is the other volume sensor
atrial natriuretic peptide
How exactly does atrial natriuretic peptide work to overall increase Na+ excretion
- increased blood volume stretches the atria causing ANP release
- this increases GFR,
- decreases aldosterone secretion
- decreases renin release
- decreases ADH release
0verall increase Na+ secretion
what is hyponataemia
low sodium due to Na+ depletion or excess H20
leads to cerebral odema
what is hypernatraemia
high sodium due to h20 depletion
(lethargy –> drowsiness –> coma)
what is hypokalaemia
low potassium due to diet, GI disorder or diuretics
causes muscle weakness
what is hypocalcaemia
low calcium due to hyperthyroidism or kidney failure or hyperventilation
can form muscle spasms or paraesthesia (thinking)
what is ionised calcium
calcium in blood not attached to proteins
what is hypercalcaemia
high calcium due to hyperthyroid or malignancy
can lead to coma,
what system is activated due to long term low bp
RAAS
what nephron structure does RAAS use to detect low bp
macula densa
