Water Balance, Diabetes Insipidus And Hyopnatraemia 08.12.23

Question 1

What is diabetes insipidus now called?

Answer 1

Arginine vasopressin deficiency - AVP Deficiency
Arginine vasopressin resistance - AVP Resistance

Question 2

Where is vasopressin sysnthesised?

Answer 2

Paraventricular and supraoptic nuclei

Question 3

Where is ADH secreted from?

Answer 3

Post. Pituitary

Question 4

What signals to the paraventricular and supraoptic nucleus to release ADH?

Answer 4

Osmoreceptor

Question 5

Where does AVP/ADH bind to in the body?

Answer 5

V1a receptors —> vasculature (inc. vasoconstriction)
V2 receptors —> in kidney (reabsorption of water under influence of vasopressin)
V1b receptors —> in pituitary (when vasopressin binds it causes the release and synthesis of ACTH)

Question 6

% of water in humans

Answer 6

TOTAL —> 42L

Intracellular —> 28L
Extracellular —> 14L : Intravascular —> 3.5L
Interstitial —> 10.5L

Question 7

Is cation positive or negative?

Answer 7

Positive!!!!! Must remember

Question 8

What is the major extracellular cation?

Answer 8

Na+

Question 9

What is the major extracellular anion?

Answer 9

Cl-

Question 10

What is the major intracellular cation?

Answer 10

K+

Question 11

Explain water balance feedback loop (start with drinking water)

Answer 11

Ingestion of water —> decreased plasma osmolality —> inc. cellular hydration —> lower thirst + lack of vasopressin secretion —> increased urine water excretion by kidneys therefore total body water decreased

WATER LEVEL THEN BACK TO NORMAL

Question 12

Explain water balance feedback loop (start with dehydration)

Answer 12

Dehydration—> increased plasma osmolality —> decreased cellular hydration —> higher thirst + increased of vasopressin secretion —> decreased urine water excretion by kidneys therefore total body water increased

WATER LEVEL THEN BACK TO NORMAL

Question 13

What part of the nephron does vasopressin act on?

Answer 13

Collecting ducts

Question 14

How is urine concentration changed in the nephron?

Answer 14

Fluid goes through glomerulus and does down the loop of Henle —> Water then exits the descending loop and Na+ exits the ascending loop —> then if ADH binds to V2 receptors which triggers intracellular cascade and aquaporin II channels and synthesised, water is allowed to be reabsorbed into body and the rest is excreted

Question 15

What is osmolality units?

Answer 15

Conc per kilo

Question 16

In osmolality is the size or number of molecules important?

Answer 16

The number of molecules is important (size does not matter)

Question 17

What are 3 diseases associated with post. Pituitary?

Answer 17

1. lack of vasopressin - AVP deficiency
2. Resistance to action of vasopressin - AVP resistance
3. Too much vasopressin release when it should be released - Syndrome of anti-diuretic hormone secretion (SAID)

Question 18

What are the 5 causes of cranial diabetes insipidus (lack of vasopressin)

Answer 18

Idiopathic
Trauma
Tumours
Genetics
Vascular - aneurysms, infarction

Question 19

Define hyponatraemia

Answer 19

Serum sodium <135mmol/l

Question 20

Define severe hyponataemia

Answer 20

<125mmol/l

Question 21

Define normal serum sodium

Answer 21

137-144mmol/l

Question 22

Signs and symptoms of hyponatraemia

Answer 22

Headache
Lethargy
Anorexia and abdominal pain
Weakness
Confusion/hallucinations

Question 23

Tests for hyponatraemia

Answer 23

Plasma osmolality
Urine osmolality
Plasma glucose
Urine sodium
Cortisol