Physiology 1-3 Flashcards
Define osmolarity?
concentration of osmotically active particles present in a solution
What is the equation for osmolarity?
molar concentration x number of osmotically active particles
What does tonicity mean?
effect a solution has on cell volume
What is the average osmotic concentration of the ECF and ICF?
300
What is the osmolarity of an isotonic solution?
300 - same
What is the osmolarity of an hypotonic solution?
<300 - cell swells
What is the osmolarity of an hypertonic solution?
> 300 - cell shrinks
What also needs to be taken into account for tonicity?
cell membrane permeability
What percentage of total body is water for males and females?
males = 60% females = 50%
Why do females have less total body water than males?
they have more fat and fat doesnt like water
What is the ECF made up of?
20% plasma
80% interstitial fluid
How are body fluid compartments measured?
tracers
What tracer can be used to measure total body water?
3H2O
What tracer can be used to measure ECF?
inulin
What tracer can be used to measure plasma?
labelled albumin
How is total body weight calculated?
ICF + ECF
How is volume of distribution measured?
dose / sample concentration
Does Na have a higher concentration in the ICF or ECF?
ECF
Does K have a higher concentration in the ICF or ECF?
ICF
What would happen to the ECF when it had an increased osmotic concentration?
lose water but not salt
become hypertonic so decrease in cell size
What would happen to the ECF when it had an decreased osmotic concentration?
would gain water, not salt
become hypotonic so increase in cell size
Is Na in the ICF?
NO
What happens to the osmolarity of the ECF and ICF if the ECF gains NaCl?
ECF increases
ICF decreases
What happens to the osmolarity of the ECF and ICF if the ECF loses NaCl?
ECF decreases
ICF increases
What can intracellular K leakages lead to?
muscle weakness
cardiac irregularities
What is the role of erythropoietin?
makes the blood thinner
RBC production
How does the kidney affect vitamin D?
converts it into its active form calcitrol
What are the two types of nephron?
juxtamedullary
cortical
What are the characteristics of juxtamedullary nephrons?
produce more concentrated urine
have a vasa recta
What are the characteristics of cortical nephrons?
shorter loops of henle
have peritubular networks of capillaries
What is the juxtaglomerular apparatus?
where the afferent and efferent arterioles form a fork coming out of the glomerulus
Does the afferent or efferent arteriole have a greater diameter?
afferent
What type of muscle makes up the afferent and efferent arterioles?
smooth muscles
What happens when the afferent arterioles contract?
less blood flows into the glomerulus
What makes up the glomerular basement membrane?
type 4 collagen
protoglycans
lamina
Where are granular and macula densa cells found?
juxtaglomerular apparatus
What is the role of the granular cells?
secreting renin
What is the role of macula densa cells?
sense the amount of NaCl in the tubular fluid as it passes through the juxtaglomerular apparatus
What percentage of plasma that enters the glomerulus is not filtered?
80%
What percentage of plasma that enters the glomerulus is filtered?
20%
What is the equation for rate of filtration?
[X]plasma x GFR
What is the equation for rate of excretion?
[X]urine x Vu (urine production rate)
What is the equation for rate of secretion?
rate of excretion of X - rate of filtration of X
What are the 3 glomerular filtration barriers?
glomerular capilary endothelium - barrier to RBCs
basement membrane - plasma protein barrier
slit process of Podocytes - plasma protein barrier
What is the net filtration pressure for filtration between bowmans capsule and the glomerulus?
10
What are the forces going into bowmans capsule?
glomerular capillary blood pressure - 55mmHg
bowmans capsule oncotic pressure - 0mmHg
What are the forces going into the glomerulus?
bowmans capsule hydrostatic fluid pressure - 15mmHg
capillary oncotic pressure - 30mmHg
What is GFR?
the rate at which protein free plasma is filtered from the glomeruli into Bowmans capsule per unit time
What is the GFR equation?
Kf (filtration coefficient) x net filtration pressure
What is a major determinant of GFR?
glomerular capillary fluid pressure
How is blood flow and glomerular filtration regulated extrinsically?
sympathetic control via baroreceptor reflex
How is blood flow and glomerular filtration regulated intrinsically?
auto regulation via myogenic mechanisms and tubular feedback mechanisms
What is the affect of increased arterial blood flow on the glomerulus?
increased blood flow to the glomerulus
increased capillary blood pressure which increases net filtration pressure which increases GFR
What happens to urine volume when there is a fall in BP?
urine volume decreases to compensate
What are the myogenic mechanisms that do intrinsic auto regulation?
vascular smooth muscle is stretched because arterial pressure is increased so it contracts and then constricts the arteriole
What are the tubuloglomerular feedback mechanisms that do intrinsic auto regulation?
involves the juxtaglomerular apparatus
if GFR rises, more NaCl will flow through the arterioles leading to constriction of the afferent arteriole
What is the equation of plasma clearance?
rate of excretion / plasma concentration
What is the clearance of glucose? Why?
0 = it is not secreted at all
What is the clearance of urea? Why?
What is the clearance of H? Why?
> GFR = it is secreted but not reabsorbed
What is used clinically to measure renal plasma flow?
para-amino hippuric acid (PAH)
Why is PAH used to measure renal plasma flow?
freely filtered at the glomerulus
secreted into the tubule
then completely cleared from plasma
What is the filtration fraction?
GFR / renal plasma flow
