Osmoregulation in terrestrial animals Flashcards
What are humidic animals?
Animals that need to live in a humid, wet environment
What are xeric animals?
Animals that can tolerate dry climates
What are the two primary osmoregulation organs in terrestrial animals?
Salt glands and kidneys
What animals have salt glands?
Marine reptiles and birds
What is the structure of the salt glands of birds?
Many loops with many secretory channels that deposit a salt solution into a central canal
Is bird urine hypo, iso, or hyperosmotic to their blood?
Isosmotic. Their kidneys can’t concentrate it any more
What sort of system do the salt glands use to concentrate the salt out of the blood?
Countercurrent between the blood and secretory tubules. The blood gives up NaCl into the ISF and the salt enters the gland cells and goes into the secretory fluid
What is the osmolarity between the the blood and ISF at the closed end of the tubule of the salt gland?
Low osmolarity
What is the osmolarity between the the blood and ISF at the central canal of the salt gland?
High osmolarity
How are the salt glands in birds under the control of the neuroendocrine system?
Osmoreceptors in the heart and brain sense increased osmolarity in the blood after the bird drinks seawater, and cause the release of ACTH. ACTH activates corticosterone, and that along with arginine vasotocin cause Na and Cl channels to open in the salt gland cells and vasodilation in the gland vessels
Why will the salt glands of birds enlarge if constantly challenged by high salts?
Larger glands are able to concentrate the salts better, so are able to get rid of more
What are the 3 hormones involved in the neuroendocrine regulation of the salt glands in birds?
ACTH, corticosterone, arginine vasotocin
Why can’t we drink seawater?
Ion levels in seawater are much higher than our blood, so we lose more water trying to process the salts and just end up more dehydrated
