Kidney Function 4

?
  • Created by: LBCW0502
  • Created on: 18-03-19 18:30
What is the normal range of plasma osmolality?
285-295 mosmol/kg
1 of 50
What is hyperkalaemia?
Plasma concentrations of potassium higher than 5.5 mM
2 of 50
Where are ROMK channels expressed?
Principal cells of the collecting duct
3 of 50
What happens when a person experiences water deprivation, solute ingestion, diarrhoea?
Increased ECF osmolarity. Detected by osmoreceptors (located in supraoptic and paraventricular nuclei) which stimulate release of ADH from posterior pituitary. ADH binds to V2 receptors (cAMP, insert AQP2), makes CD water permeable (retention)
4 of 50
What happens when the osmolality is above 290 mosm/L?
Detected by osmoreceptors of lateral preoptic area (thirst, want to drink water)
5 of 50
What happens when there is excessive fluid ingestion?
Decreased ECF osmolarity (detected by osmoreceptors in supraoptic/paraventricular nuclei), suppress ADH release, CD made water impermeable, water excretion (diuresis). Lateral preoptic area (thirst suppressed)
6 of 50
Describe features of volume regulation
Osmolarity of ECF tightly controlled. Volume of ECF determined by total quantity of solute (NaCl). Regulation of ECF volume is all about Na balance
7 of 50
What is the dietary salt intake?
Varies 0.05 - 25 g/day (kidney can cope with high salt intake). Average salt intake is 2.3 g/day
8 of 50
How does the total amount of Na in ECF dictate volume of ECF?
1 g/L NaCl dissolved in water. Add 0.2 g NaCl. Increased concentration to 1.2 g NaCl dissolved in 1 L. Cells more permeable to water than salts. Maintain osmolality of 1g/L, water leaves cells (volume of ECF increased)
9 of 50
Why is it important to maintain ECF osmolality?
If volumes changed dramatically, this could have serious consequences in confined spaces e.g. brain
10 of 50
Describe features of plasma volume (1)
Important determinant of BP in veins, cardiac chambers and arteries. So low total body Na leads to low plasma volume which leads to low CV pressures
11 of 50
Describe features of plasma volume (2)
ECF consists of plasma and interstitial fluid (4L, 10L, half of volume contained inside cells - intracellular water, 28 L). Na (mainly osmotically active solute in ECF). K (mainly osmotically active solute inside cells)
12 of 50
Describe features of plasma volume (3)
Body directly controls osmolarity and volume of ECF in vascular system. Affects osmolarity and volume of other compartments. Osmolarity is maintained at expense of volume (osmoreceptors control H2O). Renal excretion (alter ADH release). Thirst
13 of 50
How does the kidney handle sodium?
Sodium excreted in urine = sodium filtered - sodium reabsorbed. Kidney regulates sodium filtered and controls sodium reabsorption. Little evidence for regulatory Na appetite in humans (unless low Na levels)
14 of 50
GFR depends on which factors?
Starling forces (hydrostatic and colloid osmotic pressures), hydraulic permeability and surface area (regulated by both neural and hormonal input)
15 of 50
What happens when the afferent arteriole is constricted?
Reduce flow into glomerular capillaries. Reduce hydrostatic pressure. Reduce hydrostatic pressure gradient (from capillary lumen to Bowman's space). Reduce GFR
16 of 50
How is GFR controlled?
Extrinsic control (external to kidney) maintains arterial BP. Intrinsic control (internal to kidney) protects renal capillaries from hypertensive damage and maintains a healthy GFR (autoregulation)
17 of 50
Describe features of extrinsic control of GFR (1)
To maintain systemic BP. If there is low BP, it is detected by baroreceptors in carotid sinus and aortic arch, causes activation of sympathetic NS
18 of 50
Describe features of extrinsic control of GFR (2)
Decrease activity of parasympathetic NS. Sympathetic nerves innervate afferent arteriole, causing vasoconstriction, less flow into glomerular capillaries, reduce hydrostatic pressure, reduce GFR
19 of 50
Describe features of extrinsic control of GFR (3)
Also reduce SA of filtration barrier via mesengial cells (innervated by sympathetic NS and contain smooth muscle actin which contract) to reduce GFR
20 of 50
Describe features of extrinsic control of GFR (4)
Reduction in GFR will conserve Na/H2O and increase blood volume/pressure.
21 of 50
Describe features of intrinsic control of GFR (1)
Protects renal capillaries from hypertensive damage and maintains a healthy GFR (autoregulation). Can control afferent arteriole constriction
22 of 50
Describe features of intrinsic control of GFR (2)
Mechanisms - myogenic response by renal smooth muscle cells that surround arterioles (vasoconstriction in response to stretch), tubuloglomerular feedback by juxtaglomerular apparatus (controls vasoconstriction/renin release-linked to Na reabsorption)
23 of 50
Describe features of autoregulation-intrinsic mechanisms (1)
Afferent arterioles constrict when BP is raised and dilate when BP is lowered thus maintaining constant capillary pressure and glomerular blood flow
24 of 50
Describe features of autoregulation-intrinsic mechanisms (2)
As a result, the renal blood flow and GFR remains constant for arterial pressures between 90-200 mmHg
25 of 50
Describe features of autoregulation-intrinsic mechanisms (3)
Purpose - to protect glomerular capillaries from hypertensive damage and maintain a healthy GFR
26 of 50
Describe the multiple regulatory pathways controlling sodium reabsorption - sensors (1)
Affect renin and natriuretic peptide release. Tubular fluid NaCl concentration receptors within macula densa. Pressure receptors in central arterial tree (carotid/aortic arch baroreceptors)
27 of 50
Describe the multiple regulatory pathways controlling sodium reabsorption - sensors (2)
Pressure receptors in renal afferent arterioles (intrarenal baroreceptors). Volume receptors in cardiac atria and intrathoracic veins
28 of 50
Describe the multiple regulatory pathways controlling sodium reabsorption - effector pathways
Renal sympathetic nerves (stimulate renin release). Direct pressure effect on kidney (affects renin release). Renin/angiotensin II/aldosterone (stimulate Na reabsorption). Natriuretic peptides/dopamine (cause natriuresis, inhibits Na reabsorption)
29 of 50
What is the effector pathway?
Activation of sympathetic NS. Vasoconstricts afferent arteriole (reduce GFR). Reduce SA of filtration barrier via mesengial cells (reduce GFR). Stimulates renin release (secreted by granular cells)
30 of 50
Outline the extrinsic control of renin release
Sympathetic nerves of granular cells receive signals from baroreceptors in central arterial tree via CV centre. Renal corpuscle, afferent arteriole (wall has granular renin containing juxtaglomerular cells for release).
31 of 50
Outline the intrinsic control of renin release (1)
Tubuloglomerular feedback. Increase NaCl delivery to macula densa, Na-Cl-K transporter moves more Na into cells. Cause more Na reabsorption across basolateral membrane (Na-K ATPase pump)
32 of 50
Outline the intrinsic control of renin release (2)
ATP hydrolysis results in higher levels of adenosine (bind to A1 receptors - cause decrease in renin release/vasoconstriction of renal afferent arteriole, reduce GFR)
33 of 50
Outline features of renin release (1)
Effector pathway. Renin may be release by sympathetic activity (central arterial tree baroreceptors response to low BP), reduce Na delivery to macula densa
34 of 50
Outline features of renin release (2)
Reduce wall tension in afferent arteriole (intrarenal baroreceptor e.g. drop in mean/pulse pressure). Renin release can be caused by low blood volume (hypovolemia)
35 of 50
Outline how renin forms angiotensin II (1)
Plasma angiotensinogen (synthesised in liver, released into blood in excess) breaks down to form angiotensin I (10-peptide) - presence of renin is the rate limiting step. Ang I to Ang II - 8-peptide (presence of ACE)
36 of 50
Outline how renin forms angiotensin II (2)
ACE found on luminal membrane of lung capillaries (in excess)
37 of 50
What are the effects of angiotensin II?
Stimulates proximal tubule Na reabsorption. Stimulates ADH release. Causes aldosterone secretion. Causes thirst. Vasoconstricts small arterioles
38 of 50
What are the actions of angiotensin II at the level of the proximal tubule?
Angiotensin II binds to receptors on basolateral and luminal membrane. Increases activity of Na-H exchanger and Na-K ATPase pump (direct increase of Na reabsorption)
39 of 50
How does angiotensin II stimulate the release of ADH?
Ang II binds to ang II receptors on OVLT/MPN/SFO (where osmoreceptors are expressed). Stimulate ADH release from posterior pituitar and cause thirst
40 of 50
How does angiotensin II stimulate the release of aldosterone? (1)
Aldosterone is released from the adrenal cortex. Aldosterone increases Na reabsorption in DCT and CD
41 of 50
How does angiotensin II stimulate the release of aldosterone? (2)
Aldosterone affects Na-K ATPase pump on basolateral membrane and increases activity of Na channel on luminal membrane on CD. Osmoregulation, expansion of ECF, restoration of volume (BP normal)
42 of 50
What are the effects of aldosterone? (1)
Increases Na reabsorption in DCT/CD and from sweat glands and salivary glands. Increases Na absorption from gut
43 of 50
What are the effects of aldosterone? (2)
Secreted by zona glomerulosa in adrenal cortex due to ang II and increase K+ concentration. Aldosterone binds to nuclear receptors, stimulates protein synthesis (slow action compared to ADH)
44 of 50
What are the effects of aldosterone? (3)
Main action on principal cells of CD where it stimulates Na reabsorption by stimulating production of Na-K pumps and epithelial Na channels (ENaC). Water follows Na
45 of 50
Describe the sequences of events as a result of a decrease in plasma volume (1)
Increase activity of sympathetic nerves, reduce arterial pressure, reduce GFR (reduce flow to macula densa cells), reduce NaCl delivery to macula densa cells
46 of 50
Describe the sequences of events as a result of a decrease in plasma volume (2)
Increases renin release (renal juxtaglomerular cells). Increase plasma renin/ang II/aldosterone/sodium and water reabsorption, reduce Na/H2O excretion
47 of 50
When are natriuretic peptides released?
When the heart is stretched (due to high BP and high blood volume). A type secreted from atrial myocardium (ANP). B type secreted from ventricular myocardium (BNP)
48 of 50
What are the actions of ANP and BNP? (1)
Natriuretic (acts on CD cells to inhibit Na entry through ENaC, inhibits renin release and aldosterone production, synergism with dopamine to inhibit Na-K ATPase activity is proximal tubule)
49 of 50
What are the actions of ANP and BNP? (2)
Diuretic (inhibits ADH release). Hypotensive effects (decreases BP by systemic vasodilation, increases GFR by dilating renal afferent arterioles)
50 of 50

Other cards in this set

Card 2

Front

What is hyperkalaemia?

Back

Plasma concentrations of potassium higher than 5.5 mM

Card 3

Front

Where are ROMK channels expressed?

Back

Preview of the front of card 3

Card 4

Front

What happens when a person experiences water deprivation, solute ingestion, diarrhoea?

Back

Preview of the front of card 4

Card 5

Front

What happens when the osmolality is above 290 mosm/L?

Back

Preview of the front of card 5
View more cards

Comments

No comments have yet been made

Similar Pharmacy resources:

See all Pharmacy resources »See all Kidney Function 4 resources »