Osmoregulation Flashcards
HOMEOSTASIS
Maintenance of a desired state
HYPOOSMOTIC
When there is too little solutes present.
Functions of excretory organs in arthropods
FILTRATION: pressure filtering of body fluids take place where water and small solutes travel across a membrane and are filtrated in the lumen of the excretory organ. This is Driven by hydrostatic pressure or concentration gradients.
PRODUCTION OF URINE: Reabsorption of specific solutes which are transported back into the body. Secretion of specific solutes which are transported into the lumen.
MALPIGHIAN TUBULES
The main organs of excretion and osmoregulation in insects and some arthropods.
It is an outgrowth (surrounds) of the alimentary canal. It is thin tubules with a blind-ending lumen which produces primary urine which is emptied at the junction of the midgut and the hindgut.
ALIMENTARY CANAL
The whole passage along which food passes through the body from mouth to anus during digestion.
LUMEN
A lumen is the inside space of a tubular structure.
URICOTELIC ORGANISM
An organism whose main way to excrete excess nitrogen is by uric acid. Uric acid is the least toxic and requires the least amount of water but it has a high energy cost.
HEMOLYMPH
A fluid equivalent to blood in most invertebrates, occupying the hemocoel.
Function of Malpighian Tubules
Filters out solutes from the hemolymph (active secretion), which makes up the primary urine. The primary urine is isosmotic to the hemolymph and are ironically dissimilar.
It also modifies the primary urine in the hind gut. Selective reabsorption of water and certain solutes into the hemolymph takes place. The rectal pads recover chlorine ions through hormonal stimulation which creates electrical and osmotic gradients and thus reabsorption occurs (water, ions, amino acids, acetate). This results in hyper-osmotic urine. There is the elimination of other solutes (organic wastes) via the urine, through active transport into the Malpighian tubules lumen.
CONTROL OF URINE VOLUME AND CONCENTRATION
The control of urine volume and concentration differs from terrestrial animals & marine mammals and fresh water invertebrates & vertebrates. Terrestrial animals and marine mammals conserve water therefore have hyper-osmotic urine. Insects have Malpighian tubules and a hind gut which is used for active transport of salts out of the tubes resulting a in water being reabsorbed through osmosis. Terrestrial animals and marine mammals also have counter current multiplier systems where the concentration gradients allow even more water to be reabsorbed. Fresh water invertebrates and vertebrates need to get rid of excess water therefore they have hypo-osmotic urine. Their pumps transports salts out of tubes but it is near impermeable so water cannot follow passively therefore water is excreted from the tube.
Ultrafiltration
Ultrafiltration is a mostly non selective process where there is movement of fluid due to hydrostatic pressure or osmotic pressure. In complex invertebrates the occurs in the metanephridia whilst in mammals, birds and amphibians this occurs in the kidney.
Active Secretion
Active secretion, as used in insects, is where potassium is secreted into the main segments lumen and chlorine is transported in due to attraction (+- charges) which then results in water being brought in due to osmosis.
Processes that allow an organisms to obtain homeostasis.
Processes that allow an organism to obtain homeostasis includes nutrition which is the concentration of energy rich molecules, respiration and circulation, excretion, osmoregulation, and thermal regulation. All these processes need hormones.
AMMONOTELISM
The excretion of ammonium ions. Ammonia has the lowest energy cost but has the highest toxicity and it requires lots of water.
UREOTELIC ORGANISM
One whose main way to excrete excess nitrogen is via urea. Urea uses a moderate amount of energy and has low toxicity, with little water required.
