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Forbes-AP Bio- Physiology 5: Thermoregulation & Osmoregulation

5 of 11 of my Physiology Unit. 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
by

Shani Forbes

on 26 February 2014

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Transcript of Forbes-AP Bio- Physiology 5: Thermoregulation & Osmoregulation

Thermoregulation
Osmoregulation
Regulation: An Introduction
Animals Only
Plants
Animals
Animals are really the only organisms who are able to regulate their temperature.

Even among animals, there is a wide diversity of abilities to regulate temperature.

Many animals are
ecotothermi
c, which essentially makes them
thermoconformers
(though even ectotherms can affect their termperature by changing their environment.
Endotherms & Ectotherms
Endotherms
:
Able to maintain internal temperature at a different level than ambient temperature
Birds and mammals


Ectotherms
:
Internal temperature conforms to ambient temperature
All other animals.
Metabolic activity is the major source of heat production in organisms.

Endothermic organisms have a higher metabolic rate than ectothermic organisms.
Heat is exchanged between an organism and the environment in 4 major ways.
Controlling Heat Exchange
Measuring Metabolism
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
The
skin
is the major mechanism of heat exchange between animals and the environment
Organisms that live in pronounced heat sink environments (like the ocean) utilize countercurrent exchange to decrease heat loss in extremities.
Mammals utilize circulatory, integumentary (skin), and muscular processes to maintain temperature within a homeostatic range.

Too Cold:
Shivering
& constriction of skin capillaries.

Too Hot:
Sweating
& dilation of skin blood vessels.
Some examples of heat exchange strategies:
Metabolsim can be measured in organisms by measuring heat exchange and metabolic indicators (respiratory rate, heart rate, etc.)
Basal Metabolic Rate
: the minimum metabolic rate of an endotherm at rest (not correlated to temperature).

Basal Metabolic Rate (
BMR
) is a function of body size, with larger organisms consuming more oxygen per hour than smaller organisms (note the logarithmic scales)....
However, when adjusted for metabolism as a function of mass, it becomes apparent that smaller animals consume exponentially more oxygen per unit of mass than larger animals...
In Endotherms:
Why?
Why?
In Ectotherms:
Metabolic rate is a function of temperature. The higher the ambient temperature, the greater an animal's metabolic rate.

Standard metabolic rate
: The metabolic rate of an ectotherm at rest at a particular temperature.
Hippopotamus- Endothermic
Dragonfly-
Ectothermic
Energy Budgets
Comparrison of energy requirements for three different endotherms and an ectotherm.
Notice that the ectotherm (snake) has to spend no energy on thermoregulation. Also notice that compared to the comparatively sized endotherm (penguin), the ectotherm has a greatly reduced energy requirement.
Torpor
Refers to a state of decreased activity and metabolism, which enables organisms to expend less energy during times when food acquisition is unfavorable or dangerous.

Common in small endotherms (usually during the night)

Hibernation
: Long-term winter torpor.

Estivation
: Long-term summer torpor.
Data from an experiment monitoring RNA levels of two "clock genes" (Per2 & Bmal1) involved in regulating daily activity ("
circadian rhytms
") in active (
euthermic
) and hibernating European hamsters.
Hibernating Doormice
Harbor Seal- Endothermic
Lizard- Ectothermic
What's the Strategy?
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 controling 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 specialized
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.
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 temperature and their internal osmolarity.

Compare the thermoregulatory strategies of ectotherms and endotherms.

Explain the advantages of ectothermy and endothermy.

Explain how metabolism is measured in ectotherms and endotherms.

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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Keeping the balance
animal body needs to coordinate many systems all at once
temperature
blood sugar levels
energy production
water balance & intracellular waste disposal
nutrients
ion balance
cell growth
maintaining a “steady state” condition
Homeostasis
conformer
regulator
thermoregulation
conformer
Two evolutionary paths for organisms
regulate internal environment
maintain relatively constant internal conditions
conform to external environment
allow internal conditions to fluctuate along with external changes
Conformers vs. Regulators
osmoregulation
regulator
Diffusion too slow!
O2
CHO
aa
CH
aa
O2
NH3
NH3
NH3
NH3
NH3
NH3
NH3
NH3
CO2
CO2
CO2
CO2
CO2
CO2
CO2
CO2
CO2
CO2
aa
O2
CH
O2
aa
NH3
CO2
CH
aa
aa
CHO
CHO
O2
Animal systems evolved to support multicellular life
extracellular waste
intracellular waste
very little
 CO2 + H2O + P + N
lots!
 CO2 + H2O + N
Animals poison themselves from the inside by digesting proteins and
nucleic acids!
 CO2 + H2O
 CO2 + H2O
What waste products?
what do we digest our food into…
carbohydrates = CHO
lipids = CHO
proteins = CHON
nucleic acids = CHOPN
Intracellular Waste
Aquatic organisms
can afford to lose water
ammonia
most toxic
Terrestrial
need to conserve water
urea
less toxic
Terrestrial egg layers
need to conserve water
need to protect embryo in egg
uric acid
least toxic
Full transcript