Session 4

Question 1

How does solute move across the PCT cells and enter interstitium

Answer 1

Solvent follows solute, solute transported primarily water follows passively

Question 2

Driver for movement of solute across PCT cells into interstitium

Answer 2

• Increased osmolarity of ICF as solute transported into PCT
• Water from nephron lumen moves down gradient into PCT until equilibrated
• Transient increase in ICF volume
• 3Na-2K-ATPase moves Na+ into interstitium and water follows

Question 3

What solute enters the cell across the luminal (apical) membrane

Answer 3

Sodium

Question 4

What is the Net effect on the osmolarity of the PCT epithelial cells to the movement of sodium

Answer 4

No change as increased osmolarity of PCT cells means water follows

Question 5

Which ions move in 3Na-2K-ATPase

Answer 5

3 Na+ out
2 K+ in

Question 6

Primary driving force in interstitium for movement of solute and solvent from interstitium into peritubular capillaries

Answer 6

Hydrostatic pressure increased

Question 7

Primary driving force in peritubular capillaries for movement of solute and solvent from interstitium into peritubular capillaries

Answer 7

Higher oncotic pressure (lower hydrostatic), left oncotic proteins behind

Question 8

What is the function of the tight junctions between tubule cells

Answer 8

Barrier to prevent diffusion of transporter, channel and pump proteins between apical and basolateral membrane. Maintain polarity

Question 9

Percentage and location of sodium iron reabsorption along nephron

Answer 9

PCT 67%
LOH asc 25%
LOH desc 0%
DCT 5%
CD 3%

Question 10

Percentage and location of sodium ions and water reabsorption along the nephron

Answer 10

PCT 65%
LOH asc 0%
LOH desc 10%
DCT 0%
CD 5%

Question 11

What causes release of renin

Answer 11

Fall in plasma sodium leads to fall in ECF volume

Question 12

Renin is released by

Answer 12

• increased sympathetic innervation (granular cells of JGA)
• Wall tension in afferent arterioles fall, granular cells detect this which stimulates renin release
• Decreased sodium to macula densa (if less NaCl reaches the macula densa, it i stimulated to secrete prostaglandins, acts on granular cells to simulate renin release)

Question 13

Angiotensin II effects

Answer 13

Directly vasoconstricts efferent arterioles within the glomerulus

Stimulates zona glumerulosa of adrenal cortex to release aldosterone

Question 14

What does aldosterone do

Answer 14

Directly increases Na+ reabsorption from DCT with ENAC channels

Releases ADH

Stimulate thirst

Question 15

Prostaglandin synthesis

Answer 15

Decrease in effective circulating volume stimulates cortical prostaglandin synthesis

Question 16

How does JGA respond if BP is high

Answer 16

ATP release

Question 17

How does JGA respond if there is a drop in BP

Answer 17

Renin release, prostaglandin release

Question 18

Prostaglandin synthesis occurs in

Answer 18

Cortex, medullary interstitial cells, collecting duct epithelial cells

Result in vasodilators and renin release

Question 19

What is ANP (atrial natureric peptide)

Answer 19

Produced by cardiac atrial cells in response to an increase in ECF volume (high bp)

Question 20

ANP acts to

Answer 20

-Inhibit Na+/K+/ATPase and close Na+ channels of CD and DCT, reducing Na+ reabsorption, water and Na+ excretion increased
- Vasodilate afferent arterioels increasing GFR
- Inhibit aldosterone secretion and ADH release
- Decrease renin release

Question 21

What happens in high blood pressure to hydrostatic and oncotic pressure

Answer 21

NaCl intake increases so ECF increases

Hydrostatic pressure increases and oncotic pressure decreases, NaCl and water reabsorption by the PCT decreases

Question 22

Effectors of change in renal sodium excretion when renal artery BP increases

Answer 22

Reduced Na-H antiporter and reduced Na-K-ATPase activity in PT

Reduction in sodium resorption in proximal tubule (Glomerular tubular balance)

Reduction in water Resorption in PT

Pressure natriuresis and diuresis

Question 23

Summary of increased BP

Answer 23

Inhibits Na-K-ATPase and reduce ENAC expression
Decreased Na resorption DCT/CD
Increase in hydrostatic pressure of peritubular capillaries (pressure natriuresis and diuresis)

Question 24

Summary of decreased BP

Answer 24

Prostaglandin release
RAAS activated (ANG II causes constriction of efferent arteriole and release of aldosterone)
Aldosterone increases expression of ENAC, stimulates ADH and thirst

Question 25

Hypoperfusion due to congestive cardiac failure leads to

Answer 25

Na+ and water retention by the kidneys, leading to oedema, kidneys sense as hypovolemia, resulting in compensation by retaining NaCL and water to increase CFV Stimulates low BP response

Question 26

Increased pulmonary venous pressure results in

Answer 26

Transudation from the capillaries in the lungs and in pulmonary oedema Management involves reducing the fluid load e.g. diuretics, ACE inhibitors, nitrates, vasodilators

Question 27

First line diuretic

Answer 27

Furosemide

Question 28

What is hypervolaemia

Answer 28

Fluid overload, XS of total body sodium and water, leads to expansion of ECF compartment

Question 29

Hypervolaemia due to

Answer 29

Kidney retention of sodium and water Reduced effective arterial volume e.g. CCF XS sodium or fluid intake Cirrhosis Hyperaldosteronism

Question 30

Hypovolemia can lead to

Answer 30

Shock

Question 31

What is shock

Answer 31

A medical emergency in which the vital organs are not adequately perfused Anaerobic metabolism and inefficient clearance of metabolites Tiredness, dizziness, thirst Vasodilation occurs in vital organs (heart lung brain) to maintain blood supply Leads to acute tubular necrosis in kidney

Question 32

A severe decrease in circulating volume stimulates sympathetic activity to maintain BP by

Answer 32

Tachycardia Peripheral vasoconstriction Increase in myocardial contractility

Question 33

To counteract excessive vasoconstriction in Hypovolemic shock what happens in kidneys

Answer 33

Prostaglandins are secreted, maintains adequate blood flow through kidney and sufficient GFR

Question 34

2 major consequences of loss of large amounts of fluid

Answer 34

Volume depletion (decreases tissue perfusion), electrolyte and acid-base disturbances

Question 35

What is hypertensive renal disease

Answer 35

Renal autoregulation maintains Renal function despite variations in systolic BP Arteriosclerosis of major renal arteries, hyalinization of small vessels with intimal thickening Can lead to chronic renal damage (hypertensive nephrosclerosis) and a reduction in the size of the kidneys

Question 36

Renal causes of secondary hypertension

Answer 36

Impaired Na+ and water excretion increasing blood volume Stimulation of renin release Renal artery stenosis, reduces perfusion of kidney, XS RAAS

Question 37

Negative feedback loop for ADH

Answer 37

Increased ADH causes decreased renal water excretion Decreased osmolarity inhibits ADH secretion Negative feedback loops that begin with the anterior hypothalamus

Question 38

Changes in BP have an effect on the

Answer 38

Response to changes in osmolarity (Volume is more important)

Question 39

Thirst is stimulated by

Answer 39

Increase in plasma osmolarity

Question 40

Symptoms of diabetes insipidus

Answer 40

Polyuria, polydipsia, low urine osmolality (dilute)

Question 41

Too little ADH in diabetes insipidus is

Answer 41

Inability to reabsorb water from the distal part of the nephron due to failure of secretion or action of ADH

Question 42

What is hypernatremia

Answer 42

Less prevalent clinically More than 140mmol/L

Question 43

Causes of hypernatremia

Answer 43

Osmotic diuresis Fluid loss without replacement Diabetes insipidus Incorrect intravenous fluid replacement Primary aldosteronism

Question 44

Features of hyponatremia

Answer 44

Low sodium very common in hospital patients Serum conc of Na lower than 130/135mmol/L Symptoms: neurological, agitation, nausea, focal neurology, coma

Question 45

Causes of hyponatraemia

Answer 45

Diuretics Water overload or retention Increase in ADH secretion Increased plasma osmolality Increased plasma osmolality Diuretics/renal failure Peritonitis/Burns D and V

Question 46

Hyponatraemia is generally caused by

Answer 46

Water loss than sodium directly

Question 47

Reference range of serum osmolality

Answer 47

275-295 mosm/kg

Question 48

How do you calculate osmolarity

Answer 48

2 Na + glucose + urea (all in mmol/L)

Question 49

What does hypovolemic hyponatremia tell us

Answer 49

Nonrenal loss e.g. GI, sweating, ascites, burns, cerebral salt-wasting syndrome

Question 50

People with inappropriate ADH secretion are generally

Answer 50

Uvoelemic

Question 51

Treatments for hyponatraemia

Answer 51

Fluid restriction Pontine demyelination can occur with rapid correction Infusion of hypertonic saline and furosemide