Renal Physiology part 6

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What is renin and where is it produced?
It is an enzyme and is produced by the juxtaglomerular apparatus
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When is renin released via the renin-angiotensin system?
It is released into plasma when the body's sodium is reduced however the stimulus which is detected is effective circulating volume (sodium determines this)
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If there is a decrease in sodium content what happens?
There is an increased sympathetic activity, a decrease in arteriolar pressure and a decrease in sodium at macula densa so renin is released into the circulation
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What does renin do once it's in the circulation?
Renin reacts with angiotensinogen (released from the liver) and makes angiotensin I which reacts with angiotensin converting enzyme (in the lungs) which makes angiotensin II
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What does angiotensin II do?
Causes vasoconstriction, increases aldosterone, increases anti-diuretic hormone, increases thirst, increases sodium reabsorption and decrease in GFR
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Where is atrial natriuretic peptide released?
ANP is synthesised and released from cardiac atrial cells
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When is ANP released?
When atrial stretch is detected
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What does ANP do?
Decrease in sodium reabsorption, inhibition of aldosterone production, reduction of renin release and vasodilation of afferent arteriole and an increase in GFR
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What does ANP secretion result in?
Increased sodium excretion and reduction in ECV
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Where do angiotensin II, aldosterone and ANP effect in the nephron of the kidney?
Angiotensin affects the proximal tubule, aldosterone affects the distal tubule and ANP affects the distal tubule and collecting duct
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How is potassium regulated?
Distal tubule and collecting duct variable secretion/reabsorption according to dietary intake
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How does aldosterone affect potassium regulation?
It promotes potassium secretion in the collecting duct
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What substances increase calcium reabsorption in the distal tubule?
Parathyroid hormone and the active form of vitamin D
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How do proximal tubule diuretics work?
They are osmotic diuretics which increase osmolarity in tubule so less water is reabsorbed or they act as carbonic anhydrase inhibitors which blocks reabsorption
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How do loop diuretics work?
They inhibit sodium re-uptake in the thick ascending limb, decrease solute in the medulla and decrease osmolarity of urine
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How do distal tubule diuretics work?
They block sodium transporters so sodium stays in the tubule therefore increasing osmolarity in the tubule
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How do collecting duct diuretics work?
They act as aldosterone antagonists, decreasing reabsorption of sodium and secretion of potassium from principle cells OR by blocking sodium channels
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Does urine composition remain the same on leaving the renal pelvis?
Yes (exception is horse)
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Describe the filling phase of the bladder
Tonic sympathetic activity meaning bladder is relaxed and internal sphincter is closed, tonic somatic activity means external sphincter is also closed
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Describe the emptying phase of the bladder
Bladder is full, increasing pressure, increasing activity in sensory neurones which stimulates the reflex of emptying. There's an increase in parasympathetic activity, the bladder contracts, there's decrease in somatic activity to ext sphincter
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Can the bladder emptying reflex be over ridden?
Yes- inhibition of reflex from higher centres causes voluntary micturition
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Other cards in this set

Card 2

Front

When is renin released via the renin-angiotensin system?

Back

It is released into plasma when the body's sodium is reduced however the stimulus which is detected is effective circulating volume (sodium determines this)

Card 3

Front

If there is a decrease in sodium content what happens?

Back

Preview of the front of card 3

Card 4

Front

What does renin do once it's in the circulation?

Back

Preview of the front of card 4

Card 5

Front

What does angiotensin II do?

Back

Preview of the front of card 5
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