2. Changes in isovolaemia and isoosmosis. R regulations of water balance and water balance disorders

Question 1

Define homeostasis

Answer 1

Maintenance of stability in the internal environment of the organism which is a precondition of life.

Question 2

List the elements of homeostasis

Answer 2

1. Isovolemia
2. Isoosmosis
3. Isoionia
4. Isohydria

Question 3

Give the aim of restoring homeostasis

Answer 3

• Restoring volume relations
• Restoring the other elements of homeostasis

Question 4

Draw osmoregulation (by direct feedback via ADH)

Answer 4

Question 5

Osmolarity is measured with which device?

Answer 5

Osmometer

Question 6

Give the osmolarity of body fluids

Answer 6

300 mOsmol/l

Question 7

Calculate the osmolar gap (OG)

Answer 7

OG = Measured serum osmolality - Calculated osmolality

Question 8

Calculate the ‘calculated osmolality’

Answer 8

CO = 2 x Na + Glucose mmol/L + Urea mmol/L

Question 9

A normal osmol gap is…

Answer 9

< 10 mOsm/kg

Question 10

Alcohols affecting osmolar values in the body

Answer 10

• Ethanol intoxication
• Methanol ingestion
• Ethylene glycol ingestion
• Acetone ingestion
• Isopropyl alcohol ingestion

Question 11

Sugars affecting osmolar values in the body

Answer 11

• Sorbitol
• Mannitol

Question 12

Lipid affecting osmolar values in the body

Answer 12

Hypertriglyceride

Question 13

Protein affecting osmolar values in the body

Answer 13

Hypergammaglobinemia

Question 14

Draw the regulation of water balance

Answer 14

Answer 15

Question 16

Give the pathway in the incidence of hyperosmosis

Answer 16

1. Hyperosmosis
2. Osmoreceptors
3. Neurohypophysis
4. ADH-release
5. H₂O ↑

Question 17

Give the pathway in the incidence of hypovolaemia

Answer 17

1. Baroreceptors (volume receptors)
2. J.G. renin-release
3. Angiotensin I, II, III
4. Adrenal cortex: Aldosterone release
5. Na↑ + H₂O↑ (Indirect)

Question 18

Give the location of the arterial baroreceptors

Answer 18

• Aortic curve
• Sinus caroticus

Question 19

Which receptors detect hypovolaemia?

Answer 19

Atrial stretch receptors

Question 20

Answer 20

Vagus Nerve

Question 21

Answer 21

Carotid sinus nerve → Glossopharyngeal nerve

Question 22

Restoring isovolemia is a priority in order to prevent…

Answer 22

Hypovolaemic shock

Question 23

As a result of water loss and subsequent hyperosmosis, there is a….which ensures homeostasis

Answer 23

Dual compensation process

Question 24

What makes up the dual compensation process of osmoregulation?

Answer 24

• Endogenous compensation
• Exogenous compensation

Question 25

Endogenous compensation of osmolarity

Answer 25

• Osmoreceptors - Sense the decreased osmolarity
• ↑ ADH secretion → ↑ Water absorption in the kidney tubules

Question 26

Exogenous compensation of osmolarity

Answer 26

• Thirst centre in the hypothalamus is triggered, causing:
  
  • Sensation of thirst → Water intake ↑

Question 27

Endogenous + exogenous compensation leads to…

Answer 27

• Decreased osmolarity of plasma
• This leads to the reverse of the compensation processes
• ADH secretion ↓ and thirst sensation ↓

Question 28

Give the process of volume regulation

Answer 28

1. JGA detects hypovolemia + ↓ BP
2. Renin release from JGA granular cells
3. Angiotensin I → Angiotensin II in pulmonary and renal epithelium

Question 29

Give the actions of angiotensin II

Answer 29

• Aldosterone secretion (from adrenal gland)
  
  • Causes H₂O and Na⁺ retention in kidney
  • ↑ plasma volume, ↑ osmotic conc.
• Angiotensin III secretion (in lungs)
  
  • Vasoconstriction of small arteries
  • ↑ BP

Question 30

Disorders of water balance: Dehydration/Hyperhydration

Answer 30

Dehydration

• Hypertonic: H₂O loss, hyperosmotic
• Hypotonic: NaCl loss, hypoosmotic
• Isotonic

Hyperhydration

• Hypotonic: H₂O overload, hypoosmotic
• Hypertonic: NaCl overload, hyperosmotic

Question 31

Disorders of water balance: Diabetes insipidus

Answer 31

Involved with an ADH deficiency

Can be:

• Central: Due to hypothalamic or pituitary damage
• Peripheral: Nephron unresponsive to ADH