Osmoregulation in Animals Flashcards
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What are freshwater fish at risk of? (relating to water content)
Inundation of water and loss of salts
What is the osmotic pressure of freshwater?
5 mOsm
Are freshwater fish hyperosmotic or hypo-osmotic to their environment?
Hyperosmotic
What does a ‘diluting’ kidney refer to in a freshwater fish?
Produces a large quantity of very dilute urine
Are loops of Henle present in freshwater fish?
No
What methods are used in freshwater fish to reabsorb salt?
-Additional salts are taken up by the gills
-Salts are reabsorbed in the proximal tubules of the nephrons
Do freshwater fish drink?
NO
Are saltwater bony fish hyperosmotic or hypo-osmotic to their environment?
hypo-osmotic
What are saltwater bony fish at risk of? (relating to water content)
in danger of gaining salts and dehydrating
Do marine fish drink seawater?
Yes, constantly
How do marine fish desalinate?
excreting monovalent ions (eg Na+,Cl-) at the gills. The gills perform more osmoregulation than the kidneys
What do marine fish nephrons lack?
glomeruli and Bowman’s capsules
What are the main functions of the nephrons in marine fish?
produce small volume of urine to regulate divalent ions Ca2+, Mg2+
What is the osmotic pressure of saltwater?
1100 mOsm
What is the osmotic pressure in marine fish bodies?
600 mOsm
What is the osmotic pressure in freshwater fish bodies
500 mOsm
What is the stimulus for the control system for dehydration in mammals?
rise in osmolarity of plasma
Where are the receptors and control centre for the dehydration control system in mammals?
The hypothalamus and the carotid artery
What is the effector for dehydration control in mammals?
Antidiuretic Hormone (ADH) which is released from the posterior pituitary gland
What is the ADH equivalent in reptiles, birds, fish and amphibians?
arginine vasotocin
Where does ADH binds to in the Kidney?
receptors on the basal membrane of the collecting ducts
What protein insertion does ADH trigger?
aquaporins (from vesicles which deliver info from host cells to recipient cells) onto the apical membranes. These serve as water channels and lead to formation of hyperosmotic urine.
What is the apical membrane
wall of the tubule to the lumen
What is the dehydration regulatory system in mammals called? And what kind of feedback does it use?
-Thirst Control Centre
-Negative feedback loop
How do reptiles conserve water?
At the epithelium of cloaca (urogenital opening) water is reabsorbed and a concentrated uric paste is secreted
What kind of urine do reptiles have?
Isosmotic
What nephrons do reptiles have?
Only cortical nephrons
What are the specific features of nephrons in desert mammals?
Only juxta-medullary nephrons to produce very concentrated urine. Have thick medullas. Very long loops of Henle - lots of NaCl pumps
What is the osmotic pressure of kangaroo rat urine?
5500 mOsm
What are some features of desert animals to help them not overheat?
-Most animals gain water in food and are nocturnal
-Kangaroo rat lives in burrows to combat the heat – often seal the entrances
-Long eared jerboas and fennec foxes have large ears to help dump heat
-Long loops of Henle aid in water retention in desert mammals
How do vampire bats use their kidneys after feeding?
-After feeding they are then so heavy that they need to produce a lot of dilute urine to reduce their weight so they can fly.
-produce concentrated urine - 4,600mOsm/L.
