2. Changes in isovolaemia and isoosmosis. R regulations of water balance and water balance disorders Flashcards
Define homeostasis
Maintenance of stability in the internal environment of the organism which is a precondition of life.
List the elements of homeostasis
- Isovolemia
- Isoosmosis
- Isoionia
- Isohydria
Give the aim of restoring homeostasis
- Restoring volume relations
- Restoring the other elements of homeostasis
Draw osmoregulation (by direct feedback via ADH)
Osmolarity is measured with which device?
Osmometer
Give the osmolarity of body fluids
300 mOsmol/l
Calculate the osmolar gap (OG)
OG = Measured serum osmolality - Calculated osmolality
Calculate the ‘calculated osmolality’
CO = 2 x Na + Glucose mmol/L + Urea mmol/L
A normal osmol gap is…
< 10 mOsm/kg
Alcohols affecting osmolar values in the body
- Ethanol intoxication
- Methanol ingestion
- Ethylene glycol ingestion
- Acetone ingestion
- Isopropyl alcohol ingestion
Sugars affecting osmolar values in the body
- Sorbitol
- Mannitol
Lipid affecting osmolar values in the body
Hypertriglyceride
Protein affecting osmolar values in the body
Hypergammaglobinemia
Draw the regulation of water balance
Give the pathway in the incidence of hyperosmosis
- Hyperosmosis
- Osmoreceptors
- Neurohypophysis
- ADH-release
- H2O ↑
Give the pathway in the incidence of hypovolaemia
- Baroreceptors (volume receptors)
- J.G. renin-release
- Angiotensin I, II, III
- Adrenal cortex: Aldosterone release
- Na↑ + H2O↑ (Indirect)
Give the location of the arterial baroreceptors
- Aortic curve
- Sinus caroticus
Which receptors detect hypovolaemia?
Atrial stretch receptors
Vagus Nerve
Carotid sinus nerve → Glossopharyngeal nerve
Restoring isovolemia is a priority in order to prevent…
Hypovolaemic shock
As a result of water loss and subsequent hyperosmosis, there is a….which ensures homeostasis
Dual compensation process
What makes up the dual compensation process of osmoregulation?
- Endogenous compensation
- Exogenous compensation
Endogenous compensation of osmolarity
- Osmoreceptors - Sense the decreased osmolarity
- ↑ ADH secretion → ↑ Water absorption in the kidney tubules
Exogenous compensation of osmolarity
- Thirst centre in the hypothalamus is triggered, causing:
- Sensation of thirst → Water intake ↑
Endogenous + exogenous compensation leads to…
- Decreased osmolarity of plasma
- This leads to the reverse of the compensation processes
- ADH secretion ↓ and thirst sensation ↓
Give the process of volume regulation
- JGA detects hypovolemia + ↓ BP
- Renin release from JGA granular cells
- Angiotensin I → Angiotensin II in pulmonary and renal epithelium
Give the actions of angiotensin II
- 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
Disorders of water balance: Dehydration/Hyperhydration
Dehydration
- Hypertonic: H2O loss, hyperosmotic
- Hypotonic: NaCl loss, hypoosmotic
- Isotonic
Hyperhydration
- Hypotonic: H2O overload, hypoosmotic
- Hypertonic: NaCl overload, hyperosmotic
Disorders of water balance: Diabetes insipidus
Involved with an ADH deficiency
Can be:
- Central: Due to hypothalamic or pituitary damage
- Peripheral: Nephron unresponsive to ADH
