Urinary Tract: Regulation of GFR, Potassium + Blood Pressure

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  • Created by: Bhickling
  • Created on: 21-04-21 14:14
What does GFR stand for?
Glomerular Filtration Rate
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What happens if GFR is too low?
- too little filtrate
- reduced flow of filtrate
- certain waste products may not be excrete so will accumulate in the body
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What happens if GFR is too high?
- too much filtrate
- increased urine production
- increased flow = too little time for reabsorption so substances lost in urine
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What does autoregulation do?
maintains GFR during short term + moderate variations in mean arterial pressure by changing the afferent arteriole resistance
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What will happen to GFR if blood flow to the afferent arteriole is restricted?
- filtration will be decreased due to reduced blood flow = reduced hydrostatic pressure
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Name the two mechanisms of autoregulation
1. myogenic response
2. tubuloglomerular feedback
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Describe the myogenic response in the afferent arteriole
Intravascular pressure elevated:
- GFR increases
- vasoconstriction of afferent arteriole
- reduces blood flow + hydrostatic pressure in glomerulus to prevent rise in GFR
Intravascular pressure reduced:
- GFR decreases
- vasodilation of afferent arteriole
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Describe the tubuloglomerular feedback mechanism of autoregulation
- macula densa cells in nephron detect actual changes in GFR
- send paracrine signal to adjacent myocytes afferent arteriole
- vasoconstriction/ vasodilation
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Why is it dangerous to have an increased potassium concentration in the body?
More potassium on outside of cells = depolarisation of inside cells- slows heart rate, causing lots of dysrhythmias + eventually stops heart
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What does aldosterone do?
- directly detects changes in K+ concentration
- stimulates principle cells in the DCT + collecting duct to secrete more K+ into filtrate
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Describe the neural regulation of systemic blood pressure
Baroreceptor reflex:
- regulates SV
- regulates HR
- regulates TPR via tone of vasculature
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Describe the hormonal regulation of systemic blood pressure
Angiotensin II:
- long-term regulation
- regulates SV
- regulates TPR via tone of vasculature
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Where does angiotensin II come from + what does it do (apart from regulating systemic blood pressure)?
- comes from a cascade of reactions that start with the release of renin from JG cells in juxtaglomerular apparatus
- increases blood pressure by increasing blood volume
- increases Na absorption
- effects hypothalamus (increases thirst + ADH)
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What does renin do?
- released from JG cells in response to a decrease in blood pressure
- converts angiotensinogen to angiotensin I
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What does angiotensin converting enzyme (ACE) do?
converts angiotensin I to angiotensin II
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Why is aldosterone important?
- increases reabsorption of Na+
- this increases water reabsorption = increases blood volume, venous return + SV
- increases blood pressure
- decreases K+ concentration
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What is aldosterone secretion stimulated by?
- decreased blood pressure
- increased K+ concentration
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What effects does angiotensin II and noradrenaline have on the afferent/ efferent arteriole?
- constrict afferent arteriole = decreases blood flow to glomerular, reduces hydrostatic pressure = decreases GFR
- constrict efferent arteriole = decreases blood flow to glomerular capillaries, increases hydrostatic pressure to help preserve GFR= small d
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Which two regulators will over-ride autoregulation?
1. sympathetic system
2. angiotensin II
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What is angiotensin II secretion stimulated by?
decrease in blood pressure
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What happens if blood pressure is increased?
natriuretic peptides are released- decrease blood pressure + increase GFR by:
- vasodilation of afferent arteriole
- decrease in aldosterone secretion
- decrease in Na + water reabsorption
- decrease in ADH secretion
- stimulation of reflexes to decrease
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Other cards in this set

Card 2

Front

What happens if GFR is too low?

Back

- too little filtrate
- reduced flow of filtrate
- certain waste products may not be excrete so will accumulate in the body

Card 3

Front

What happens if GFR is too high?

Back

Preview of the front of card 3

Card 4

Front

What does autoregulation do?

Back

Preview of the front of card 4

Card 5

Front

What will happen to GFR if blood flow to the afferent arteriole is restricted?

Back

Preview of the front of card 5
View more cards

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