Renal Physiology Flashcards
(127 cards)
1
Q
What is the kidney?
A
Bilateral bean-shaped organ which is reddish-brown in colour, is retroperitoneal and located in the posterior abdomen at T12-L3 which is responsible for filtration, excretion and blood pressure control.
2
Q
What vertebral level is the kidney situated at?
A
T12-L3
3
Q
What are the physiological functions of the kidney?
A
- Regulation of body fluid volume and osmolality
- Maintenance of ion balance
- Acid-base balance
- Waste excretion
- Vitamin D hydroxylation (25-hydroxycholecalficerol + 1a hydroxylase 1,25 a hydroxycholecalciferol (calcitriol))
- EPO
- Renin production
4
Q
Define blood pressure.
A
pressure exerted by ventricles (circulatory system) against arterial walls
5
Q
Give the equation for Blood Pressure.
A
BP = CO x TPR
6
Q
Which factors affect arteriolar radius.
A
- Neural controls: SNS vs NO-releasing nerves
- Hormonal controls: AGT/Adrenaline/AVP vs Adrenaline/ANP
- Local controls: Myogenic response/Endothelin-1 vs Hypoxia/Potassium/Carbon Dioxide/Acid/Adenosine/Nitric Oxide/Bradykinin
7
Q
List 4 hormonal controls responsible for vasoconstriction and vasodilation of blood vessels.
Which variable of the cardiac output equation does this affect?
A
Hormonal controls: AGT/Adrenaline/AVP vs Adrenaline/ANP
TPR
8
Q
List 4 local controls responsible for vasoconstriction and vasodilation of blood vessels.
Which variable of the cardiac output equation does this affect?
A
Myogenic response/Endothelin-1 vs Hypoxia/Potassium/Carbon Dioxide/Acid/Adenosine/Nitric Oxide/Bradykinin
9
Q
What is cardiac output?
A
rate of blood pumped out of LV into systemic circulation (L/min)
10
Q
List the variables for Cardiac Output and the factors for each.
A
• Heart Rate:
- PSNS (Brake)
- SNS (Accelerator)
- Adrenaline
- Drugs
• Stroke Volume:
- SNS (increased)
- EDV (SNS veins/ BV/ skeletal muscle pump/ respiratory pump -> venous pressure -> venous return)
11
Q
In the case of hypovolemia, outline how the RAAS mediates homeostatic changes.
A
• Hypovolemia ± low osmotic pressure -> reduced BP + increased Na+ -> macula densa detects elevated salts -> reduced baroreceptor firing = reduced SNS drive (= NA) -> renin release (kidney) = angiotensinogen (liver) -> angiotensin I + ACE (lungs) -> angiotensin II…
- Arteriolar vasoconstriction (TPR increases)
- Efferent glomerular arteriole vasoconstriction (maintain GFR and salt reabsorption)
- ADH secretion (AGT II binds posterior pituitary)
- Salt + water reabsorption via aldosterone release (AGT II binds zona glomerulosa of adrenal cortex = aldosterone release)
12
Q
What mnemonic can be used to remember the effects of Angiotensin II?
A
Mnemonic: ‘Pressure to get 5 As’
Aldosterone release (zona glomerulosa)
Arteriolar vasoconstriction
Arteriole (glomerular efferent) vasoconstriction
ADH release (posterior pituitary)
Absorption (re-absorption): Proximal tubule
13
Q
Outline the role of ADH in low blood pressure?
Is ADH more responsive to:
A. Hypovolemia
B. Osmotic pressure (increased osmolarity)
C. Hypervolemia
A
• Low osmotic pressure (increased osmolarity) ± reduced blood volume -> reduced BP -> hypothalamic osmoreceptors detect ∆ -> neuronal afferents to posterior pituitary gland = ADH/AVP released:
- Increased water permeability (renal collecting ducts) = increased blood volume + reduced urinary output
- Vasoconstriction = increased TPR
- Dipsogenic: Hypothalamic thirst center
B. Osmotic pressure (increased osmolarity)
14
Q
What 3 main effects does ADH have to mediate changes in blood pressure?
A
Mnemonic: People Value Dipsogenesis
Permeability
Vasoconstriction
Dipsogenic
15
Q
Outline how ANP functions in response to raised blood pressure.
A
• Increased osmotic pressure/increased blood volume -> increased BP -> detected by atrial cardiopulmonary baroreceptors in atrial cardia = increased baroreceptor firing -> ANP release -> afferent arteriole vasodilation + increased flow through vasa recta (reduce osmolarity of medullary interstitium) + increase collecting duct Na+ excretion -> reduce blood volume = reduce BP
- Natriuresis:
- Arteriole (afferent) vasodilation
- Aldosterone reduced (zona glomerulosa)
- Vasodilation (vascular)
- Fibrosis (anti-fibrotic)
16
Q
State the mnemonic used to remember the effects ANP has on blood pressure.
A
Mnemonic: FAVourite NA
Fibrosis reduced
Arteriole (afferent) vasodilation
Vasodilation
Natriuresis
Aldosterone reduced
17
Q
Outline the effect PGs have on renal control of blood pressure.
A
• Reduced BP -> Prostacyclin (PGI2) and PGE2 released -> afferent arteriole vasodilation -> increased GFR -> reabsorption of ions across nephron -> increase BP
18
Q
Outline the effect EPO has on mediating blood pressure control.
Include the drive for EPO production.
State the site of production of EPO.
A
• Reduced blood volume (hypovolemia) -> reduced O2 availability ≈ Hypoxia -> HIF-2 -> EPO enhancer -> EPO production (kidney) -> increased erythropoiesis ≈ increased Hematocrit (increased MCV; reduced MCHC?) = increased BP
Kidney
19
Q
Define Mean Cell Volume.
Give the equation for MCV.
State the three classifications for MCV.
A
• Average volume of RBCs
MCV = Hct/ RBC
- Microcytic (60-80fl): iron deficiency, thalassemia
- Normocytic (80-100fl): blood loss, chronic disease anaemia, renal impairment
- Macrocytic (100-120fl): megaloblastic anaemia, B12/folate deficiency, myelodysplasia
20
Q
Should a patient have a MCV of 70fl, what MCV category is this?
A
Microcytic (60-80fl)
21
Q
Should a patient have a MCV of 90fl, what MCV category is this?
A
Normocytic (80-100fl)
22
Q
Should a patient have a MCV of 110fl, what MCV category is this?
A
Macrocytic (100-120fl)
23
Q
What is MCH? Give the equation.
A
MCH = Hb/RBC
• Average mass of Hemoglobin per red blood cell
24
Q
What is MCHC? Give the equation.
A
MCHC = Hb/Hct
• Average concentration of Hemoglobin per volume of red blood cells
25
Give the two divisions/classifications of MCHC (Hb/Hct).
- Normochromic: Cells with normal [Hb]
| - Hypochromic: Cells with low [Hb]
26
Describe the connective tissue layers and state their function generally.
1) Fibrous capsule
Layer of collagen fibres that covers outer surface of entire organ
Surrounds the adrenal gland but there is a septum between the 2 structures to separates them
2) Perinephric fat
Thick layer of adipose tissue that surrounds fibrous capsule
Adipose tissue acts as shock absorber and provides protection
3) Renal fascia
Dense, fibrous outer layer that anchors kidney to surrounding structures
Posteriorly, renal fascia fuses with deep fascia surrounding muscles of the body wall
Anteriorly, renal fascia forms thick layer that fuses with peritoneum
27
Outline the neurovasculature of the kidney.
Arteries
- Renal arteries (abdominal aorta)
- Renal hilum
- Segmental branches —> interlobular arteries —> arcuate arteries —> vasa rata —> afferent arterioles —> capillary network
Veins:
- Renal veins
- Leave hilum anteriorly, crossing abdominal aorta and empties into IVC ; L longer than R as IVC on RHS of body
28
Which vein is longer and why, left renal vein or right renal vein?
L is longer than R, as IVC is on RHS of body
29
What are the tributaries to the renal veins?
Left gonadal and left suprarenal veins drain into L renal vein; Right gonadal and right suprarenal veins drain into R renal vein
30
What is the outermost renal area termed?
A. Medulla
B. Cortex
C. Renal pelvis
D. Major Calyx
B. Cortex
31
What is the innermost renal area termed?
A. Medulla
B. Cortex
C. Renal pelvis
D. Major Calyx
A. Medulla
32
What is the region of the cortex bearing the majority of the nephrons termed?
A. Medulla
B. Renal pyramids
C. Renal pelvis
D. Major Calyx
B. Renal pyramids
33
What is the region of the extending from the cortex into the renal medulla termed?
A. Medulla
B. Renal pyramids
C. Renal columns
D. Major Calyx
C. Renal columns
34
What is the region of the kidney whereby the renal pyramids empty into the medulla termed?
A. Medulla
B. Renal pyramids
C. Renal papilla
D. Major Calyx
C. Renal papilla
35
What is the region of the kidney whereby urine is received from the renal papilla and transferred to the major calyx termed?
A. Medulla
B. Minor Calyx
C. Renal papilla
D. Major Calyx
B. Minor Calyx
36
What is the region of the kidney whereby urine is received from the minor calyx and transferred to the renal pelvis termed?
A. Medulla
B. Minor Calyx
C. Renal papilla
D. Major Calyx
D. Major Calyx
37
What is the region of the kidney whereby urine is received from the major calyx and ureter termed?
A. Medulla
B. Minor Calyx
C. Renal pelvis
D. Major Calyx
C. Renal pelvis
38
What is the term for the point at which the renal pelvis joins with the ureter?
Pelviureteric junction
39
List the order of connective tissue layers around the kidney.
- Fibrous capsule
- Perinephric fat
- Renal fascia (Gerota's fascia)
40
Which connective tissue layer of the kidney fuses with the peritoneum anteriorly and deep fascia posteriorly?
Renal fascia (Gerota's Fascia)
41
What is the eponymous term for Renal Fascia?
Gerota's Fascia
42
Which vessel gives rise to the afferent arteriole.
A. Interlobular vein
B. Interlobular artery
C. Intertubular capillary
D. Intersegmental artery
B. Interlobular artery
43
Outline the flow of blood from the aorta to the glomerulus.
Ascending aorta --> Desceding Aorta --> Renal artery (L1/L2) --> Intersegmental artery --> Interlobular artery --> Afferent arteriole
44
Outline the flow of blood to and from the glomerulus.
Intersegmental artery --> Interlobular artery --> Afferent arteriole --> Peritubular capillary bed --> Interlobular vein --> Descending and Ascending Vasa Recta --> Intersegmental vein
45
What is the term for the continuation of peritubular capillaries.
A. Vasa recta
B. Intertubular capillary bed
C. Interlobular artery
D. Interlobular vein
A. Vasa recta
46
What are the two types of nephron?
i) Superficial nephron: Glomeruli in outer cortex, shorter LoH dipping into outer medulla
ii) Juxtamedullary nephron: Glomeruli near corticomedullary border with larger glomeruli and higher GFR; LoH deeper into inner medulla and papilla which concentrate urine more
47
What is the term for a nephron with its glomeruli situated in the outer cortex.
A. Juxtamedullary nephron
B. Standard Nephron
C. Peritubular Nephron
D. Superficial nephron
D. Superficial nephron
48
What is the term for a nephron with its glomeruli situated in the medulla.
A. Juxtamedullary nephron
B. Standard Nephron
C. Peritubular Nephron
D. Superficial nephron
A. Juxtamedullary nephron
49
What type of nephron concentrates urine more?
A. Juxtamedullary nephron
B. Standard Nephron
C. Peritubular Nephron
D. Superficial nephron
A. Juxtamedullary nephron
50
Describe the glomerulus.
A. Ball of blood vessels with intersegmental arteriole entering then efferent arteriole leaving
B. Ball of blood vessels with afferent arteriole entering then efferent arteriole leaving
C. Ball of blood vessels with efferent arteriole entering then afferent arteriole leaving
D. Double-walled capsule contiguous with glomerulus bearing parietal SSE.
B. Ball of blood vessels with afferent arteriole entering then efferent arteriole leaving
51
Describe the Bowman's Capsule.
double-walled capsule contiguous with glomerulus bearing parietal (SSE) and visceral (podocytes + pedicles) layer of epithelia
52
What is the primary role of the PCT?
A. Concentration of salt
B. Water flows out
C. Reabsorption of ions by active transport and secondary active transport by the Na+, K+-ATPase at the apical membrane
D. Reabsorption of ions by active transport and secondary active transport by the Na+, K+-ATPase at the basolateral membrane
D. Reabsorption of ions by active transport and secondary active transport by the Na+, K+-ATPase at the basolateral membrane
53
What is the primary role of the LoH?
A. Concentration of salt
B. Water flows out
C. Reabsorption of ions by active transport and secondary active transport by the Na+, K+-ATPase at the apical membrane
D. Reabsorption of ions by active transport and secondary active transport by the Na+, K+-ATPase at the basolateral membrane
A. Concentration of salt
54
What is the primary role of the Descending Limb of LoH?
A. Reabsorption of water
B. Water flows out
C. Concentration of interstitium/filtrate by reabsorption of water
D. Dilution of filtrate by reabsorption of ions
C. Concentration of interstitium/filtrate by reabsorption of water
55
The following statement is false. The descending limb of the Loop of Henle is:
A. Immediately before the Ascending Loop of Henle in the Nephron
B. Is permeable to water
C. Is permeable to salt ions
D. Contributes to salt concentration
C. Is permeable to salt ions
The descending limb of the Loop of Henle is impermeable to salt ions, hence how it concentrates salt ions
56
The following statement is false. The ascending limb of the Loop of Henle is:
A. Immediately after the Descending Loop of Henle in the Nephron
B. Is permeable to water
C. Is permeable to salt ions
D. Contributes to salt concentration
B. Is permeable to water
The ascending limb of the Loop of Henle is impermeable to water. It concentrates filtrate by extruding Na+ via AT to generate hypertonic interstitium.
57
What is the primary role of the collecting ducts?
Permeable to water in presence of ADH thus water moves by osmosis determining concentration of urine
58
What duct passes urine from the Collecting Ducts to the Minor Calyx?
Ducts of Bellini (Papillary Duct)
59
What is the eponymous term for the Papillary Ducts?
Ducts of Bellini
60
What is the functional unit of the kidney? List its components.
Nephron, consisting of a glomerulus + tubule
i) Glomerulus: Cluster of blood vessels
ii) Tubule: Epithelial structure with subdivisions converting filtrate into urine;
- Bowman’s capsule with Bowman’s space inside, contiguous with lumen of tubule ≈ filtrate passes from lumen of tubule to vascular system;
- PCT
- LoH
- DCT
- CD
61
What are the two types of nephron? Compare and contrast these two.
1) Superficial Cortical Nephrons: Glomeruli in outer cortex
- Smaller glomeruli ≈ lower GFR
- Shorter LoH ≈ outer medulla
- Operate under normal conditions
2) Juxtamedullary Nephrons: Glomeruli near corticomedullary border
- Larger glomeruli ≈ higher GFR
- LoH deeper into medulla ≈ concentrate urine
- Increased use in periods of high activity/strain
62
What is the renal corpuscle?
Site of formation of glomerular filtrate composed of glomerulus, Bowman’s Capsule and Bowman’s space
63
List the 5 major processes occurring in the nephron and the region they occur at.
1) Glomerulus: Filtration
2) PCT: Reabsorption and secretion
3) LoH: Generation of osmotic gradient
4) DCT: Regulated absorption + secretion
5) CD: Regulation of water uptake by CD
64
What is Glomerular filtration? Outline how the process occurs.
Process of blood in the glomerulus delivered via afferent arteriole at high pressure (≈ 50mmHg) against Bowman’s Capsule (endothelial + BM + Podocytes) causing transudation and filtrate in Bowman’s space to be removed by proximal tubule
• Blood into glomerulus via afferent arteriole @ 50mmHg
• Blood forced against Bowman’s Capsule + Glomerulus (Renal corpuscle)
i) Endothelial cells (SSE w/ fenestrations + glycocalyx) = filtration + negative
ii) Glomerular basement membrane: Type IV collagen + heparin sulphate = negatively charged
iii) Podocytes (Epithelial of Bowman’s Capsule): filtration slits + negative = filtration electrostatic repulsion
65
Outline the three structural features facilitating Glomerular Filtration.
• Blood into glomerulus via afferent arteriole @ 50mmHg
• Blood forced against Bowman’s Capsule + Glomerulus (Renal corpuscle)
i) Endothelial cells (SSE w/ fenestrations + glycocalyx) = filtration + negative
ii) Glomerular basement membrane: Type IV collagen + heparin sulphate = negatively charged
iii) Podocytes (Epithelial of Bowman’s Capsule): filtration slits + negative = filtration electrostatic repulsion
66
What is the relationship between filterability and molecular radius and charge?
Relative filterability increases as molecular size decreases and increases for cations or neutral molecules
67
What are the key variables/aspects to glomerular filtration?
* RBF = amount of blood traversing renal artery or vein per unit time (≈ 1100ml/min)
* RPF = amount of plasma traversing renal artery or vein per unit time (≈600ml/min)
- Haematocrit
68
List the mechanisms responsible for autoregulation of glomerular function.
Intrinsic:
1) Myogenic
2) Tubuloglomerular feedback
Extrinsic:
1) Hormones:
- AGT II
- Adrenaline
- NE
- ANP
- PGs
69
Outline the mechanism for myogenic autoregulation of glomerular filtration.
Myogenic autoregulation: Arteries/arterioles react to change of flow via myocyte contraction to keep flow and pressure constant
• Pressure -> Stretch receptors -> Depolarisation -> Local feedback (autocrine) -> Contraction -> Reduced flow (Poiseulle’s Law – Q = Pπr4/8nl)
70
Outline the mechanism for tubuloglomerular feedback of glomerular filtration.
Tubuloglomerular feedback: GFR adapted to concentration of salt in tubular fluid at macula densa
• Elevated GFR/hypernatremia -> reabsorption in PT but excess ions remain in filtrate -> Macula Densa: DCT meets afferent and efferent arterioles; Na+ enters MD cells via NKCC2 + water follows (hypertonic solution) -> hyperosmotic thus cell swells = Vg-anion channels ≈ ATP released ≈ binds purine receptors (juxtacrine signaling) --> JG cells: ATP binds to cell ≈ [Ca2+]i rises ≈ contraction ≈ constriction of afferent arteriole reduced GFR + reduced renin from JGA cells
71
Which group of kidney cells detect a change in blood pressure in autoregulation of glomerular filtration?
A. Endothelial
B. JGA cells
C. MD cells
D. Mesangial cells
C. MD cells
72
Which group of kidney cells produce renin in response to a change in blood pressure in autoregulation of glomerular filtration?
A. Endothelial
B. JGA cells
C. MD cells
D. Mesangial cells
B. JGA cells
73
What is the link between renal blood flow, arterial blood pressure and glomerular filtration rate generally and why?
Increasing arterial blood pressure (mmHg) increases renal blood flow which increases glomerular filtration rate. Renal blood flow and glomerular filtration rate maintained regardless of increasing arterial blood pressure due to auto regulatory mechanisms of myogenic or tubuloglomerular feedback ≈ ∆ afferent arteriole ≈ ∆ GFR
74
Which proximal tubular transport protein is responsible for reabsorption of Sodium and Potassium? Is this an apical or basolateral transporter?
A. Na+,K+-ATPase
B. SGLT1/2
C. NHE
D. GLUT2
E. H+ATPase
A. Na+,K+-ATPase
Basolateral
75
Which proximal tubular transport protein is responsible for reabsorption of Sodium and Glucose? What type of transport does this use?
A. Na+,K+-ATPase
B. SGLT1/2
C. NHE
D. GLUT2
E. H+ATPase
B. SGLT1/2
Facilitated diffusion
76
What is the major difference between SGLT1/2?
SGLT1: 2Na+ cf 1 Glucose
SGLT2: 1Na+ cf 1 Glucose
Both via facilitated infusion
77
Which proximal tubular transport protein is responsible for reabsorption of Sodium with H+ secretion? What type of transport does this use?
A. Na+,K+-ATPase
B. SGLT1/2
C. NHE
D. GLUT2
E. H+ATPase
C. NHE
Anti-port used in luminal acidification
78
Which proximal tubular transport protein is responsible for reabsorption glucose? What type of transport does this use?
A. Na+,K+-ATPase
B. SGLT1/2
C. NHE
D. GLUT2
E. H+ATPase
GLUT2
79
Which proximal tubular transport protein is responsible for excretion of H+ only? What type of transport does this use? Is this an apical or basolateral transporter?
A. Na+,K+-ATPase
B. SGLT1/2
C. NHE
D. GLUT2
E. H+ATPase
E. H+ATPase
Apical
80
Which proximal tubular transport protein is responsible for reabsorption of sodium and excretion of bicarbonate? What type of transport does this use? Is this an apical or basolateral transporter?
A. Na+,K+-ATPase
B. SGLT1/2
C. NHE
D. GLUT2
E. NBCe1 (SLC4A4)
E. NBCe1 (SLC4A4)
Basolateral
81
List the proximal tubule cells which are involved in sodium movement.
Na,K-ATPase
SGLT1/2
NBCe1 (SLC4A4)
NHE
82
Which ion is used in the production of 'new' bicarbonate?
HPO4-
83
List the transporters of the Thick Ascending Limb.
1. Na+,K+-ATPase: Na+ out and K+ in electrogenic (3:2) at basolateral membrane into blood ≈ create electrochemical gradient
2. NHE: Na+ in and H+ out in antiport via facilitated diffusion ≈ Na+ follows electrochemical gradient
3. NKCC2: Na+ in, 2Cl- following electrochemical gradient via apical membrane
4. K+-channels: Basolateral and apical K+ channels ≈ K+ out into lumen or interstitium
5. Claudins: Paracellular diffusion of cations and water from tubular lumen into interstitial fluid (interstitium)
84
Give a type of blood pressure drug that acts at the thick ascending limb. Give examples and how it works.
Loop diuretics e.g. Furosemide or Bumetanide
Binds to NKCC2 to reduce activity thus reduced reabsorption + elevated tubular luminal ion concentration ≈ osmotic gain ≈ fluid loss
85
Which two types of cells exist in the Distal Convoluted Tubule (DCT).
Principal cells (H20 + Sodium)
Intercalated cells (K+ and excrete H+)
86
What blood pressure drug acts in the early distal convoluted tubule and what is the mechanism of action?
Thiazide diuretics
MOA: Block NCC ≈ reduced sodium and chloride ≈ increase luminal ion concentration ≈ osmotic gain ≈ water out ≈ diuresis
87
List some types of drugs targeting the nephron.
* Loop Diuretics: NKCC2 (TAL) (Furosemide, Bumetanide)
* Thiazide Diuretics: NCC (DCT)
* Aldosterone antagonists: Aldosterone-specific Na+,K+-ATPase (Spironolactone, Eplerenone)
* Na+-channel blockers: Block apical Na+-channel (Amiloride, Triamterene)
88
What are the sites of action of AGT II. State its effects.
PCT, TAL, DCT, CDT
- Increase Na+, Cl-, H2O reabsorption
- Increase H+ secretion
89
What are the sites of action of PTH. State its effects.
PT, TAL, DCT
- PO43- excretion/reduced reabsorption
- Ca2+ reabsorption
90
What are the sites of action of ADH. State its effects.
DCT, CT, CD
- Increase H20 reabsorption
91
What are the sites of action of ANP. State its effects.
DCT, CT, CD
- Reduce NaCl reabsorption
92
What are the sites of action of Aldosterone. State its effects.
CT, CD
- Increase NaCl reabsorption
- Increase K+ secretion
93
Which of the following hormones are responsible for reabsorption of sodium, chloride and H+ secretion?
A. AGT II
B. PTH
C. ADH
D. ANP
A. AGT II
94
Which of the following hormones are responsible for reabsorption of sodium, chloride and K+ secretion?
A. AGT II
B. PTH
C. ADH
D. Aldosterone
D. Aldosterone
95
Which of the following hormones are responsible for reabsorption of Calcium?
A. AGT II
B. PTH
C. ADH
D. Aldosterone
B. PTH
96
Which of the following hormones are responsible for excretion of Phosphate?
A. AGT II
B. PTH
C. ADH
D. Aldosterone
B. PTH
97
Which of the following hormones are responsible for reabsorption of water?
A. AGT II
B. PTH
C. ADH
D. Aldosterone
C. ADH
98
What is angiotensin II? Outline the influences it has on the kidney, giving the MOA?
Peptide hormone derived from angiotensinogen which is processed via RAAS which causes sodium reabsorption in the PCT, TAL, DCT and CDT.
MOA: AGT II binds AT1R ≈ Gaq ≈ PLC ≈ DAG + IP3 ≈ Increased activity of Na+, K+-ATPase on basolateral side of tubule cell; Increased activity of NHE on apical membrane ≈ increased electrochemical gradient of Na+ + increased H+ secretion
- Na+, Cl- and H20 in; H+ out
- Aldosterone release from adrenal cortex
- Vasoconstriction of afferent or efferent arterioles in glomerulus
- Release of ADH/AVP from Posterior Pituitary
99
What is ADH/AVP? Outline the influences it has on the kidney, giving the MOA?
Anti-diuretic hormone/Arginine Vasopressin is a peptide hormone synthesised in the hypothalamus and transported via magnocellular neurone axons to the posterior pituitary gland released by HPA axis stimulation via parvocellular neurones into the portal venous system
MOA: ADH binds ADHr ≈ Gas ≈ cAMP ≈ PKA ≈ phosphorylation of AQP2 ≈ AQP2 translocation ≈ insertion into apical membrane ≈ water in ≈ water out at basolateral membrane via AQP3 channel ≈ H20 reabsorption
Effect:
- H20 reabsorption
100
What is ANP? Outline the influences it has on the kidney, giving the MOA?
Peptide hormone secreted by cardiac atria upon distension due to increased blood volume (hypervolaemia) ≈ inhibit reabsorption of sodium and water by renal tubules in DCT, CT and CD thus natriuresis + diuresis
MOA: ANP binds receptor ≈ reduce Na+,K+-ATPase activity ≈ reduced electrochemical gradient + water ≈ natriuresis + diuresis ≈ reduce blood volume
101
What is PTH? Outline the influences it has on the kidney, giving the MOA?
Peptide hormone secreted by chief cells of parathyroid gland ≈ Gaq ≈ PLC ≈ PIP2 -> DAG + IP3 ≈ PKC + IC Ca++ ≈ calcium reabsorption + phosphate excretion/reduced reabsorption
102
How may the SNS change blood pressure regarding sodium?
- Constrict renal arterioles ≈ reduce GFR ≈ reduce Na+ extrusion
- Increase renin release ≈ RAAS ≈ angiotensin II
- Adrenal stimulation ≈ aldosterone
103
List the two components of the Nephron.
Renal corpuscle (Glomerulus + Bowman's Capsule)
Renal tubule (PCT, PST, TDL, TAL, CD)
104
Which substances are transported most across the PT?
A. NaCl by AT
B. NaCl by diffusion
C. Urea
D. H20
A. NaCl by AT
105
Which substances are transported most across the TDL of LoH?
A. NaCl by AT
B. NaCl by diffusion
C. Urea
D. H20
D. H20
106
Which substances are transported most across the ThAL (Thin Ascending Limb) of LoH?
A. NaCl by AT
B. NaCl by diffusion
C. Urea
D. H20
C. Urea
D. H20
107
Which substances are transported most across the TAL (Thick Ascending Limb) of LoH?
A. NaCl by AT
B. NaCl by diffusion
C. Urea
D. H20
A. NaCl by AT
108
Which substances are transported most across the DCT?
A. NaCl by AT
B. NaCl by diffusion
C. Urea
D. H20
A. NaCl by AT
D. H20
109
Which substances are transported most across the Collecting Duct (inner Medullary)?
A. NaCl by AT
B. NaCl by diffusion
C. Urea
D. H20
C. Urea
D. H20
110
What is the Counter-Current Multiplier mechanism in the kidney?
process of using energy to generate an osmotic gradient enabling reabsorption of water from tubular filtrate and production of concentrated urine
111
Outline the process of the Counter-Current Multiplier Mechanism.
1. Fluid from PCT to LoH @ 300mOsm/L (≈ plasma)
2. AT of Na+ ions against gradient from TAL @ 200mOsm/L and medullary interstitium of 400mOsm/L
• AT against Na+ gradient
• Urea reabsorption
• No H20 movement
3. Passive Na+ ion movement out of ThAL + No H20 Movement
• Na+ out by simple diffusion
• No Urea movement
• No H20 movement
4. Water out of TDL into medullary interstitial fluid --> Tubular fluid in TDL equilibrates with interstitial fluid as water moves out of descending limb into medullary interstitial fluid
5. Fluid from PCT to LoH moves fluid on
• Urea joins via recirculation from medullary interstitium to contribute to osmolarity of tubular filtrate
6. Ions pumped out of TAL again to medulla until 200mOsm/L gradient established
• Interstitial osmolarity: 500mOsm/L
• Ascending tubule: 300mOsm/L
7. Water movement out of descending limb of LoH to reach osmotic equilibrium with medullary interstitial fluid.
8. Repeat steps: Osmolarity of deepest part of medulla rises to 1200-1400mOsm/L
9. DCT removes ions via AT of NaCl so osmolarity continues to fall + ADH-dependent water reabsorption in cortex preserve osmotic gradient in medulla
• High urea concentration in medullary collecting ducts causes urea to diffuse from CD to medullary interstitial fluid via ADH-activated urea transporter
• Urea moved back into tubule at inner medullary section of LoH thus recirculates through tubule
112
What is the osmolarity of tubular filtrate at the PCT?
A. 250mOsm/L
B. 300mOsm/L
C. 350mOsm/L
D. 400mOsm/L
B. 300mOsm/L
113
What is the osmolarity of tubular filtrate at the TAL after Na+ leave?
A. 250mOsm/L
B. 200mOsm/L
C. 300mOsm/L
D. 350mOsm/L
B. 200mOsm/L
114
Which region of the nephron tubule is permeable to water?
A. PCT
B. TDL
C. ThAL
D. TAL
B. TDL
115
What contributes to fluid flow throughout the nephron tubule the most.
A. Fluid from PCT to LoH
B. Fluid from ThAL to TAL
C. Fluid from LoH to PCT
D. Fluid in the Collecting Duct being excreted
A. Fluid from PCT to LoH
116
Where in the nephron tubule are ions actively pumped out to produce/initiate the counter-current multiplier?
A. ThAL
B. TAL
C. PCT
D. DCT
B. TAL
117
Which animal is most likely to be able to concentrate urine to the greatest osmolarity?
A. Fish
B. Human
C. Camel
D. Lion
C. Camel
118
Outline the physiological mechanism by which dehydration requires ADH to control water reabsorption.
Dehydration ≈ increase [ECF] osmolarity ≈ detected by osmoreceptors in the hypothalamus ≈ magnocellular neurones conduct from paraventricular nuclei in hypothalamus ≈ secreted into bloodstream ≈ plasma ADH increases ≈ increases H20 permeability in distal tubules and collecting duct ≈ increases cortical water reabsorption ≈ reduced diuresis ≈ concentrated urine ≈ redress hyperosmolar ECF
119
List 3 examples which may cause an increase in ADH.
Plasma osmolarity increased
Hypovolemia
Hypotension
Nausea
Hypoxia
Drugs: Morphine/Nicotine/Cyclophosphamide
120
List 3 examples which may decrease ADH.
Reduced plasma osmolarity
Hypervolemia
Hypertension
Drugs: Alcohol/Clonidine/Haloperidol
121
Which of the following are most likely to reduce ADH?
A. Increased plasma osmolarity
B. Hypotension
C. Hypervolemia
D. Hypovolemia
C. Hypervolemia
122
Which of the following are most likely to reduce ADH?
A. Increased plasma osmolarity
B. Hypotension
C. Hypertension
D. Hypovolemia
C. Hypertension
123
Which of the following are most likely to reduce ADH?
A. Increased plasma osmolarity
B. Hypotension
C. Clonidine
D. Hypovolemia
C. Clonidine
124
Which of the following are most likely to reduce ADH?
A. Increased plasma osmolarity
B. Haloperidol
C. Hypotension
D. Hypovolemia
B. Haloperidol
125
Which of the following are most likely to increase ADH?
A. Reduced plasma osmolarity
B. Hypovolemia
C. Hypervolemia
D. Hypertension
B. Hypovolemia
126
Which of the following are most likely to increase ADH?
A. Alcohol
B. Haloperidol
C. Cyclophosphamide
D. Clonidine
C. Cyclophosphamide
127
Which of the following are most likely to decrease ADH?
A. Nicotine
B. Haloperidol
C. Cyclophosphamide
D. Morphine
B. Haloperidol
