Filtration and Clearance Flashcards
What does the glomerular filtration rate do when the afferent arteriole dilates?
Increases
More blood enters glomerulus
Why does glomerular filtration rate increase with a dilated afferent arteriole?
Decrease in vascular resistance (more blood flow)
Increase in intraglomerular pressure (efferent arteriole doesn’t dilate)
What is glomerular filtration rate?
Volume of plasma filtered by glomerulus per unit time
Why is inulnin and ideal substance for determining glomerular filtration rate?
It isn’t reabsorbed or secreted
It’s exogenous
It isn’t metabolised
Normal glomerular filtration rate
100mL/minute
Renal clearance
Amount of plasma cleared of a compound per unit time
Which blood pressures can GFR be kept constant?
Between 80mmHg and 180mmHg
Normal GFR
180L/day
How is glomerular filtration rate regulated?
Autoregulation
Myogenic response
Tuboglomerular feedback
Myogenic response
1) Arterioles, capillaries detect stretch from increased blood pressure
2) Constrict to resist stretch
What is the macula densa?
Part of the juxtaglomerular apparatus
Detects changes in sodium chloride levels in the distal convoluted tubule
What does the macula densa do if it detects a drop in distal tubular sodium chloride levels?
1
2
1) Relaxes afferent arteriole
2) Stimulates renin release from the juxtaglomerular cells of the afferent and efferent arterioles
What does the macula densa do if it detects a rise in distal tubular sodium chloride levels?
1
2
1) Constricts afferent arteriole
2) Inhibits renin release from juxtaglomerular cells of the afferent and efferent arterioles
What is the juxtaglomerular apparatus?
1) Situated between distal convoluted tubule, renal corpuscle
2) Made up of juxtaglomerular cells, macula densa cells, smooth muscle
3) Regulates glomerular filtration rate
Location of macula densa cells
Distal convoluted tubule part of juxtaglomerular apparatus
Location of juxtaglomerular smooth muscle
Afferent arteriole
Function of juxtaglomerular cells
Secrete renin
Glomerular filtration rate homeostasis 1 2 3 4 5 6 7 8
1) GFR increases
2) Flow in the distal convoluted tubule increases
3) Macula densa detects this
4) Paracrine form macula densa diffuses to afferent arteriole
5) Afferent arteriole constricts
6) Increase in resistance in afferent arteriole
7) Decrease in glomerular hydrostatic pressure
8) GFR decreases
Tubuloglomerular feedback
GFR maintained by macula densa cells
What is the feedback system mediated by macula densa cells called?
Tubuloglomerular feedback
Ways to alter renal excretion
1) Renin-angiotensin system
2) Sympathetic nervous system
3) Atrial natriuretic peptide
4) Increase or decrease cardiac output
5) Vasopressin (antidiuretic hormone)
Where does atrial natureitic peptide come from?
The heart
When is atrial natriuretic hormone released?
When the atrial cells detect stretch form too much blood in the heart
Function of atrial natriuretic hormone
Kidneys excrete more salt and water
