L23 - Renal Function 2: Filtration & Clearance Flashcards
Why is inulin the ideal substance for determining glomerular filtration rate?
it is not reabsorbed, it is not secreted, it is exogenous and it is not metabolised
If there are 4 units of inulin in 100 mL of plasma and 4 units per minute are appearing in the urine, how much plasma is being filtered every minute?
100 mL of plasma is being filtered every minute
What is renal clearance?
rate of urinary excretion of a substance, relative to its plasma concentration
If plasma concentration of urea was 4/100 mL, GFR was 100 mL/min and 50% of the urea was reabsorbed, then urea clearance would be:
50 mL/min
If the clearance of X is less than GFR, then (X is being secreted by the nephron / X is being reabsorbed by the nephron, more X is being secreted than reabsorbed / non of the above)
X is being reabsorbed by the nephron
What normally happens to GFR if mean arterial pressure increases from 90 to 110 mmHg?
it doesn’t change
Why doesn’t GFR change when arterial pressure increases from 90 to 110 mmHg?
autoregulation maintains a nearly constant GFR when mean arterial blood pressure is between 80 and 180 mmHg
Which components are involved in autoregulation of GFR?
myogenic response and tubuloglomerular feedback
How does the Macula densa respond to increased GFR?
releases a paracrine that results in constriction of the afferent arteriole
What is the Macula densa?
structure found in the nephron through which the afferent arteriole travels before reaching the glomerulus
What is tubuloglomerular feedback and how does it respond to GFR?
response of the Macula densa to increased GFR
results in release of a paracrine which constricts the afferent arteriole and decreases hydrostatic pressure in the glomerulus
What can renal excretion be altered by?
renin-angiotensin system, sympathetic nervous system, atrial natriuretic peptide and vasopressin
Is the sympathetic nervous system activated when blood pressure increases or decreases?
when blood pressure decreases
Will the renin-angiotensin system and the sympathetic nervous system be used to excrete or reabsorb sodium?
reabsorb sodium
Will atrial natriuretic peptide be used to excrete or reabsorb sodium?
excrete sodium
When is the renin-angiotensin-aldosterone system activated?
when there is a drop in blood pressure
What happens when renin is released from granular cells?
renin travels around the body until it comes into contact with the liver which releases angiotensinogen -> angiotensin I is formed which comes into contact with the lungs and is converted by ACE into angiotensin II
What does angiotensin II do to arterioles?
constricts arterioles to increase blood pressure
What happens when angiotensin II interacts with the adrenal gland?
adrenal gland releases aldosterone which assists in regulating sodium balance
Where does aldosterone act on the nephron?
aldosterone acts on the collecting duct which results in increased sodium reabsorption
Will angiotensin II receptors most likely be located in the afferent or efferent arteriole of the nephron in order to maintain GFR?
efferent arteriole as angiotensin II will result in constriction and therefore regulation of GFR
How does noradrenaline affect the afferent arteriole?
constricts the afferent arteriole to reduce renal blood flow which decreases GFR
How is GFR maintained during exercise?
RAAS is activated and angiotensin II constricts the efferent arteriole + effect of all other regulation systems
Is renal function a priority of the sympathetic nervous system?
no
