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AP Bio- Regulation 3: Osmoregulation

3 of 7 of my Regulation Domain. Image Credits: Biology (Campbell) 9th edition, copyright Pearson 2011, & The InternetProvided under the terms of a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported License. By David Knuffke
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David Knuffke

on 26 June 2015

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Transcript of AP Bio- Regulation 3: Osmoregulation

Osmoregulation
Plants
Animals
Due to their inability to move, plants are essentially
osmoconformers
.

However, internal osmolarity has serious consequences for plant physiology.
The Vertebrate Excretory System
Control
The Kidney
Osmoconformers vs. Osmoregulators
To Review:
There is an inverse relationship between solute concentration and water concentration.

Osmolarity
- Total solute concentration expressed as (moles of solute/liters of solution)

Ex. Human Blood is ~300 milliOsmoles/liter (mOsm/L). Seawater is ~1000 mOsm/L.
animals that remain isoosmotic with their surroundings.

Must be surrounded by saltwater
animals that regulate their internal osmolarity.

Can live in many different environments.
Cnidarians are osmoregulators
The osmoregulatory adaptations of marine and freshwater fish accomplish opposite purposes.
Salmon can tolerate both freshwater and marine environments ("
euryhaline
").

Most animals can only tolerate a narrow range of external osmolarities ("
stenohaline
")
Tardigrades live in environments that are only hydrated temporarily (drops of water, seasonal ponds). To allow for survival in these kinds of environments, they can survive in a dormant, dehydrated state for decades ("
anhydrobiosis
")
Terrestrial animals constantly lose water to the atmosphere.
A comparison of the daily water balance of a kangaroo rat (dessert inhabitant) and a human demonstrates some interesting differences.
Osmoregulation, Osmolarity & Excretion
Animals regulate their osmolarity by controlling the amount of solute that they retain in their bodily fluids.

Inake of water, Excretion of fluid and dissolved solute is the major way that animals control internal osmolarity.
Nitrogenous Waste
Excretory systems depend on speicalized
transport epithelia
to move specific solutes either in to or out of bodily fluids.
The production of salt secretions in the nasal glands of the albatross allow it to survive by drinking seawater.
Waste molecules produced by cells from the breakdown of proteins and nucleic acids.
Three Major Kinds:
Ammonia
: Most toxic. Only produced by aquatic animals

Urea
: Formed by combining ammonia with carbon dioxide. Not as toxic, so it can be tolerated at higher concentrations than ammonia, and released with less water.

Uric Acid
: Least soluble. Can be excreted with the least amount of water. More energetically expensive to produce than Urea.
The form of an animal's nitrogenous waste reflects its phylogeny and habitat.
Excretory Systems
Bird guano is a commercially valuable source of nitrogen. Wars have been fought over the stuff.
All Excretory systems involve 4 major processes:
Filtration
: Initial movement of fluid and solutes from the body to the system ("
filtrate
")
Reabsorption
: Water and desirable solutes are reclaimed by transport epithelim.
Secretion
: Excess waste solute is sent to the filtrate.
Excretion
: The modified filtrate ("
urine
") is expelled from the body.
Protonephridia:
Platyhelminthes
Metanephridia:
Annelids
Malpighian Tubules:
Arthropods
Interstitial fluid moves in to the protonephridia.

The filtrate is produced through the action of ciliated "
Flame Bulb
" cells.

Filtrate then leaves the animal through openings in the body wall.
Fluid from the
coelom
moves into the
metanephridium
.

Reabsorption and secretion are accomplished by transport epithelium that line the border of the metanephridium and the capillary network.

Stored urine can be excreted through external openings.
Filtrate moves from
hemolymph
into the
malpighian tubules
.

From the tubules, filtrate is combined with undigested food and eliminated from the body through the rectum.
All excretory systems utilize
tubules
for collection of filtrate.
Kidneys:
Ureters:
Bladder:
Urethra:
Filtrate collection and urine production
Transport urine to the bladder
Urine storage
Urine Excretion
The organ responsible for filtration and urine production.

Contain ~1,000,000 filtration units ("
nephrons
")
Nephrons
The interface between the circulatory system and the excretory system
Responsible for filtration, reabsorption and secretion.

A tube surrounded by capillaries:
Glomerulus
: ball of capillaries that passes filtrate into the nephron at the "
Bowmans capsule
"
Proximal tubule
: Reabsorption of water, salt, and bicarbonate ions.
Loop of Henle
: Reabsorption of water (
descending
) and salt (
ascending
).
Distal tubule
: Reabsorption of water, salt and urea.
Collecting Duct
: Excretion of concentrated urine.
By actively transporting salt ions, the nephron creates a hyperosmotic environment that leads to the passive transport of water from the filtrate and results in the production of hyperosmotic, concentrated urine.

This is called the
"Two-Solute" Model
of nephron function.
ADH:
The RAAS System:
When blood osmolarity increases, the pituitary gland releases
antidiuretic hormone
(
ADH
), which increases water reabsorption in the collecting duct of the nephron.

ADH also triggers a
thirst response
in the animal.

These effects decrease osmolarity.
ADH triggers a cellular response in collecting duct cells which leads to an increase in the number of
aquaporins
in cell membranes, increasing water reabsorption.
When blood volume or blood pressure decreases, a region of the nephron (the "
juxtaglomerular apparatus
") releases the hormone
renin
.

Renin production results in the conversion of
angiotensinogen
to
angiotensin II
.

Angiotensin II
causes arterioles to constrict, and causes the adrenal glands to produce
aldosterone
.

Aldosterone
triggers increased reabsorption of sodium ions and water in the distal tubule of the nephron.

The effects of the RAAS system increase blood volume (and blood pressure).
Adaptations:
Dialysis:
The Vampire Bat
Feeds at night on large animals.

Drinks a lot of blood per feeding.
To compensate for the massive influx of fluid, the vampire bat excretes up to 25% of it's body mass in urine per hour while feeding.
For individuals with kidney failure. Do the same thing that your kidneys do, but:
more expensive.
Time consuming.
Not a long-term solution for kidney falure.
Big Questions:
Make Sure You Can:
Why do organisms need to regulate their internal conditions?

How is regulation accomplished?
"Pee side"
"I Drink your blood, and then I pee on you!"
Explain why organisms need to regulate their internal osmolarity.

Describe the similarities and differences of the osmoregulatory/nitrogenous waste excretion systems of different lineages of animals.

Describe the structure and function of the mammalian excretory system in general and the nephron in specific.

Explain how all of the hormonal controls discussed in this presentation work to maintain osmoregulatory homeostasis in mammals.
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Full transcript