Animal Osmoregulation - C6 Flashcards
What is the function of the kidney?
Essential to homeostasis. creates and excretes urine, regulates water and salt concentration in the blood, maintains balance between waste disposal and an animal’s need for water and salts
What is ammonia?
Nitrogenous waste from protein metabolism
Highly toxic
Must be removed or converted within the body (this is dependent on an animal’s access to water)
How do animals with lots of water excrete ammonia?
Excrete directly as Ammonium Ion (NH4+)
Most toxic form, but can be released and diluted into water quickly
How do animals with less water excrete ammonia
Converted from ammonia to urea by the liver
Less toxic = can be held in the body for longer
How do animals with least water excrete ammonia?
Convert twice into Uric Acid
Insoluble in water = does not need a lot of water to excrete
Uses most energy of all processes
What is the function of the Proximal Convoluted Tubule?
The start of osmoregulation
Organic solutes like glucose or amino acids are reabsorbed here
Also recaptures some salts and water
What is the Loop of Henle?
Passes through two layers of kidney (the Renal Cortex - outer and the Medulla - inner and hypertonic and very salty)
Most reabsorption happens here
Extracts water on the way down to the Medulla (as it is so salty, the membrane is highly permeable to H2O)
Pumps out salt (Na+ and Cl-) on the way back up to the cortex
Is the medulla hyper or hypotonic?
Hyper, in comparison to the filtrate which causes the water in the filtrate within the descending loop to continue being filtered out into the medulla
What is the function of the Distal Convoluted Tubule and the Collecting ducts?
Regulates salts (Na+, K+ and CA2+)
Actively pumps these back into the blood if needed
Within the collecting ducts, the nephron tube goes back into the salty medulla and ADH instructs the collecting ducts on how porous to make their membranes (how much water needs to be reabsorbed)
What is the function of the Ureter?
Two tubes that drain from the kidneys to the bladder
Smooth muscle walls that contract (peristalsis)
What is the function of the Bladder?
Sac that holds urine (up to 1L)
Stretch receptors in walls detect when full
What is the function of the Urethra
Tube from bladder
Has two sphincters (internal urethral - autonomic and the external urethral - somatic)
What is ADH?
Anti Diuretic Hormone, tells kidneys to reabsorb water in collecting ducts
Give an example of osmoregulation in dehydration
Stimulus: Low blood water
Receptor/Control center: Hypothalamus
Effector 1: Pituitary gland releases more ADH
Effector 2: Collecting duct becomes more permeable to water
Response: More water is released into blood so blood water rises = a small amount of concentrated urine
