Body Fluid Volume and Osmoregulation

Question 1

What is another name for ADH?

Answer 1

ADH = anti diuretic hormone

Vasopressin

Question 2

Where is ADH synthesised?

Answer 2

In the hypothalamus

Question 3

Where is ADH released?

Answer 3

From the terminals of hypothalamic neurones found within the posterior pituitary

Question 4

What does ADH increase the expression of?

Answer 4

AQP2

Question 5

How does ADH increase the expression of AQP2?

Answer 5

ADH interacts with V2 receptor
Triggering adenylyl cyclase to produce cAMP
cAMP promotes nucleus transcription and PKA (protein kinase A)

Question 6

Describe osmolality across the nephron

Answer 6

High in the proximal tubule
Highest in the loop of Henle
Lower in the collecting duct

Question 7

Describe flow rate in the nephron with no ADH present

Answer 7

Highest at the start of the proximal tubule and then decreasing

Question 8

Describe osmolality in the nephron

Answer 8

High in the proximal tubule
Highest in the loop of Henle
Lower in the convoluted tubule
Then increasing to be as high as the loop of Henle

Question 9

Compare flow in the nephron with ADH and without

Answer 9

With ADH present flow decrease across the nephron in the same way but to a much greater extent

Question 10

How do cells survive the very high osmolality in the nephron?

Answer 10

They have adapted to have a range of organic osmolytes within the cells
This includes sorbitol, inositol, glycerophosphororylchlorine and betaine

Question 11

What is diabetes insipidus?

Answer 11

Loss of ADH secretion or loss of kidney sensitivity to ADH

Question 12

What would cause a loss of sensitivity to ADH?

Answer 12

Nephrogenic diabetes insipidus

Problem with the V2 receptors

Question 13

What are the symptoms of diabetes insipidus?

Answer 13

Unable to produce concentrated urine
Polyuria
Dehydration

Question 14

What is central diabetes insipidus?

Answer 14

Caused by head injury, tumours or infection
Treated with desmopressin (ADH analogue)
Some treatment with thiazides

Question 15

What causes nephrogenic diabetes insipidus?

Answer 15

Toxicity
Hyperglycaemia
Genetic mutations

Question 16

How is nephrogenic diabetes insipidus treated?

Answer 16

Thiazide diuretic

Low salt diet

Question 17

What is SIADH?

Answer 17

Syndromes in inappropriate ADH

Question 18

What cause SIADH?

Answer 18

Most commonly a head injury

Question 19

What are the symptoms of SIADH?

Answer 19

Inappropriately high levels of ADH

Concentrated urea

Question 20

How is SIADH treated?

Answer 20

With Urea

Question 21

What is the body’s mechanism against thirst?

Answer 21

Increase of osmolality of the plasma
Osmolality detected by anteroventral third ventricle AV3V
AV3V neurones extend into the hypothalamus, increasing thirst

Question 22

What happens if you drink sea water?

Answer 22

Dehydration

1kg of sea water require 1.4L of water to clear

Question 23

What is the maximum urine concentration?

Answer 23

1400mOsm

Question 24

How much urine must be produced to secrete 1400 mOsm?

Answer 24

1 litre

Question 25

What is a hyperosmolar hyperglycaemic state?

Answer 25

Hyperosmolality caused by high blood glucose levels Leads to strong thirst Can also cause altered mental status, seizures and increases blood viscosity

Question 26

What does the body regulate with regards to volume of water?

Answer 26

The effective circulating volume

Question 27

What is the juxtaglomerular apparatus?

Answer 27

The complex of late distal tubule and renal different arteriole

Question 28

What is the macula densa?

Answer 28

Thickening of the wall of the early distal tubule

Question 29

What system increases the effective circulating volume?

Answer 29

Renin-angiotensin-aldosterone system

Question 30

What are the two triggers for aldosterone release?

Answer 30

Angiotensin II | Hyperkalaemia

Question 31

What is spironolactone?

Answer 31

Blocks the effect of aldosterone

Question 32

How is the renin angiotensin system inhibited?

Answer 32

ACE inhibitors AT1 receptor antagonists Aldosterone receptor antagonists Renin inhibition

Question 33

What is the main receptor for angiotensin II?

Answer 33

AT1 receptor

Question 34

What is the AT1 receptor coupled to?

Answer 34

Gq

Question 35

What are the five actions of angiotensin II on circulating volume?

Answer 35

Vasoconstriction Increase Na+/H+ exchange in the proximal tubule Increase in aldosterone release from the adrenal cortex, increasing distal Na+ absorption Cause ADH release Cause thirst

Question 36

What produces renin?

Answer 36

Granule cells

Question 37

What regulates renin production?

Answer 37

Sympathetic innervation of granule cells

Question 38

What are the effects of activating sympathetic innervation of the afferent arteriole?

Answer 38

Vasoconstriction upstream of granule cells causes decreased pressure sensed by them, results in a fall in blood pressure Direct stimulation of renin release by granule cells Afferent arteriole vasoconstriction reduces GFR

Question 39

What is the neurotransmitter in the nerves of the afferent arteriole?

Answer 39

Noradrenaline

Question 40

What causes vasoconstriction?

Answer 40

Alpha 1 adrenoreceptors that are Gq coupled

Question 41

What receptors are found on the granule cells?

Answer 41

Beta 1 adrenoreceptors that are Gs coupled

Question 42

What is another stimulus of renin release?

Answer 42

Decreased Na+ delivery to the distal tubule | A result of decreased venous tone and greater fluid loss from the filtrate

Question 43

What is atrial natriuretic peptide?

Answer 43

ANP Released in response to increased venous return Decreases the activity of Na+/K+/ATPase Increases renal excretion of Na+

Question 44

What works the same as atrial natriuretic peptide?

Answer 44

Renal natriuretic, produced in the kidney

Question 45

What is the primary effect of ADH?

Answer 45

To drop osmolality