Osmoregulation Flashcards
Why is osmoregulation essential
Dehydration slows or stops metabolism.
Overhydration can cause haemolysis and dilution of ions and nutrients.
Water must be balanced to maintain cellular function and homeostasis.
What is osmoregulation
Regulation of water potential in body by balancing water intake and loss to maintain a stable optimum
How is water grained and lost
Gained: From drinks, food, and metabolic water (respiration)
Lost: Through urine, sweat, breath, and faeces
What detects changes in blood water potential
Osmoreceptors in hypothalamus detect blood osmotic pressure and water potential
How does hypothalamus respond to low water potential in blood
Osmoreceptors signal neuroendocrine cells to produce ADH
ADH travels to and is released from the posterior pituitary gland
ADH increases kidney permeability to water, restoring water potential
What does ADH do in kidney
Binds to receptors in collecting ducts and late distal tubule
Increases permeability to water by inserting aquaporins into luminal membranes
Water is reabsorbed into blood via osmosis (due to low water potential in medulla)
What happens to ADH levels when blood water potential is high
ADH release is suppressed, collecting duct becomes less permeable, and excess water is excreted in dilute urine.
What is diuresis and what causes it
Diuresis is the production of dilute urine.
Caused by low ADH levels or substances like alcohol and caffeine that inhibit ADH.
What is the Renin-Angiotensin-Aldosterone System (RAAS)?
A hormone system activated by low blood volume/pressure:
Renin → activates angiotensin → stimulates aldosterone
Aldosterone increases sodium reabsorption → water follows by osmosis → raises blood volume & pressure
What is diabetes insipidus
A condition where ADH secretion or response is impaired, leading to production of large volumes of dilute urine and dehydration.
What causes DI in domestic animals
Malfunction of posterior pituitary gland
Kidney insensitivity to ADH
Causes include congenital defects, trauma, tumors, or idiopathic origins
How is DI diagnosed
Urinalysis (low specific gravity, dilute urine)
Blood glucose to rule out Diabetes Mellitus
Complete blood count and imaging if needed
How is DI treated
Central DI: ADH replacement (injections, nasal spray, skin patches)
Diet: Low salt intake to reduce water loss
Ensuring constant water access to prevent dehydration
