Physiology Flashcards by Anna Crawford

what is osmolarity

concentration of osmotically active [articles in a solution

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what are the units of osmolarity

mosmol/l

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what 2 things are needed to work out the osmolarity

molar concentration and number of osmotically active particles

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what is the equation for osmolarity

molar concentration x number of active molecules

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what is tonicity

the effect a solution has on a cell

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what does hypotonic solutions do to the cell

makes the cell burst- increases cell volume due to water rushing into cell so that the solution and cell ar ebalanced

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What happens in a hypertonic solution

higher solute concentration outside cell, so water moves out of the cell to balance the solute concentration causing a shrinkage in cell volume

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what 2 parts makes up the total body water in a human

intracellular fluid and extracellular fluid

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what 3 things make up the extracellular fluid

plasma, lymph, interstitial fluid (80%)

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what do we use to help us measure total body fluid compartments

tracers

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what tracers are used for the following 3 things: TBW, ECF, Plasam

TBW: 3H2O, ECF: inulin, Plasma: labelled albumin

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what is the equation for measuring the volume of distribution

V (litres)= Dose (D) / Sample Concentration (C)

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Is Na higher in ECF or ICF

ECF

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Is K higher in ECF or ICF

ICF

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Is Cl higher in ICF or ECF

ECF

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Is HCO3 higher in ICF or ECF

ECF

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what would happen to ICF if the osmotic concentration of ECF increases

it would decrease

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what would happen to ICF if the osmotic concentration of ECF decreased

increased

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if there was a gain or loss of isotonic fluid, would there be a change in fluid osmolarity?

no, only a change in ECF volume

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why is regulation of ECF important?

vital for long term regulation of blood pressure

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what ion makes up most of the osmotic concentration of ECF

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what is measuring K important for?

establishing membrane potential

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what can small changes in K balance lead to?

muscle paralysis and cardiac arrest

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what is the arterial supply (3) to the glomerulus

renal artery- afferent arteriole- efferent arteriole

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what is the juxtaglomerular junction

when part son the proximal tubule pass between the afferent and efferent arterioles

what are the 2 types of nephrons called?

juxtamedullary and juxtacortical

which is more common, juxtamedullary or cortical

cortical

what is the difference between juntamedullary and cortical nephrons

1) loop of henle is longer and thinner in juxtamedullary | 2) blood supply to the medullary loop of henle is via vasa recta

what is urine

modified filtrate of blood

what is the equation for rate of excretion

rate of filtration + rate of secretion - rate of reabsorption

what is the equation for the rate of filtration of a substance

concentration of X x GFR

what is the equation for rate of secretion

concentration of urine x urinary flow rate Vu

what is the rate of reabsorption equation

rate of filtration- rate of excretion

how much of the plasma is filtered into urine

20%

what are 3 filtration barriers in glomerulus

glomerular capillary endothelium (barrier to RBC) basement membrane (plasma protein barrier) Slit processes of podocytes (plasma protein barrier)

what 3 layers make up the glomerular membrane

endothelial cell, basement membrane, podocytes

what is the glomerular capillary blood pressure

55mmHg

what is the bowmans capsule hydrostatic pressure

15mmHg

what is the capillary oncotic pressure

30 mmHg

what is the bowman capsule oncotic pressure

0mmHg

What is GFR

rate at which protein free plasma is filtered from glomeruli into the bowmans capsule per unit time

what is the equation for glomerular filtration rate

GFR= Kf (filtration coefficient) x net filtration pressure

what is the normal GFR

125ml/min

what is the major determinant of GFR

glomerular capillary blood pressure

how is GFR regulated extrinsically

by sympathetic control via baroreceptor reflex

how is GFR controlled intrinsically

myogenic mechanism and tubuloglomerular feedback mechanism

if blood pressure falls, what will happen to GFR?

it will decrease

what happens in myogenic autoregulation

if vascular smooth muscle is stretched, arterial pressure increases, the arteriole then contract and constrict

What happens in tubuloglomerular feedback

involves juxtaglomerular apparatus, if GFR rises, more NaCl flows through tubule leading to constriction of afferent arterioles

what is plasma clearance

a measure of how effective the kidneys can clean the blood of a substance

what is the plasma clearance equation

rate of excretion/ plasma concentration OR (urine conc of X x urine flow rate X) / conc plasma

what substance can be used to determine GFR

inulin

what is the clearance in a substance like glucose which is completely reabsorbed?

what would the clearance look like in urea which is only partially reabsorbed

clearance

what happens if clearance

substance reabsorbed

what happens if clearance= GFR

substance neither reabsorbed or secreted

what happens when clearance > GFR

substance is secreted into tubule

what is used to measure renal plasma flow

para amino hippuric acid

what is the filtration fraction

fraction of plasma flowing through glomeruli that gets filtered into tubules

what is the equation for filtration fraction

GFR/ renal plasma flow

roughy how much filtered fluid will reabsorb back into the proximal tubule

80ml/min

what 5 things are reabsorbed in the proximal tubule

sulphate, lactate, sugars, amino acids, phosphate

what 7 things are secreted in the proximal tubule

H, hippurates, neurotransmitters, bile pigments, uric acid, drugs, toxins

what type of reabsorption occurs

paracellular and transcellular

what is primary active transport

energy is required to move the substrate and carrier against concentration gradient

what is secondary active transport

carrier molecule is transported coupled to concentration gradient of an ion

what is facilitated diffusion

passive carrier mediated transport of a substance down its concentration gradient

what kind of reabsorption occurs at basement membrane

primary active transport

what kind of reabsorption occurs in proximal tubule

secondary active transport

what is reabsorbed in ascending limb of loop of henle

Na and Cl

what is reabsorbed in descending limb of loop of henle

WATER WATER WATER

what do loop diuretics block

triple transporter- Na, Cl, K

what type of osmotic is the fluid leaving the proximal tubule?

iso osmotic

what type of osmotic enters the distal tubule

hypo osmotic