Homeostasis Flashcards
Animal’s bodies respond to changes in what 2 things?
The external environment
and their own internal environment
Metabolic activity of cells
Require O2, nutrients, and salts
Produce metabolic wastes
Changes in the internal environment arise from what 5 things
O2 concentration
Temperature
pH
salinity
humidity
Homeostasis means
The tendency to remain internally stable in the face of external fluctuations
Animals exhibit what 3 types of homeostasis?
What 2 matter here?
Thermoregulation
Osmoregulation*
Excretion*
What does the graph show?
Shore crab can survive in a wider range of salinities
Spider crab can survive in a smaller range of salinities
Open ocean def’n
examples?
respiratory surfaces are what?
Marine, open ocean
Spider crab and jellyfish
Permeable to water and salt
Osmotic conformers
total salinity of body fluids = total salinity of seawater by concentration
Stenohaline
Inability to withstand significant osmotic changes with respect to salinity
(narrow, salt or sea)
Brackish water def’n
problem for the invertebrates?
What 2 solutions to overcome the problem
The next level from marine, where it is somewhat salty but not as much as the open ocean
Passive salt loss and water gain
Salt-secreting glands in gills actively transport salt from environment into body
Green gland removes excess water via active transport
What is a hyperosmotic regulator
Organisms with higher concentration of body fluid than the environment (i.e. saline)
Shore crabs are euryhaline. What does this mean?
They can exist in a wide range of salinities
Earliest fishes lived in…
Earliest bony fishes lived where…
Marine environments
Evidence supports freshwater environments
FW bony fishes evolved to become…
More dilute in body concentration
Freshwater fish problem
Gills
Salt is passively lost, water is passively gained
Gills exacerbate salt loss and water gain
FW fish solutions
3 solutions
Effective hyperosmotic regulators
Excess water pumped out by kidney, forming dilute urine
Special salt-absorbing cells move salt from water into the blood (actively transported)
Food eaten by fish contains salts
Marine bony fishes origin
Evolved from freshwater ancestors and re-invaded the sea
Salinity of bony fishes
180 mM
Brackish water invertebrate salinity
~550 mM, same as open ocean invertebrates
Marine bony fish problem
2 solutions
Water loss, salt gain
Drink seawater->
Absorb water and salt from intestine into bloodstream->
Salt is carried by blood to gills, where it is actively transported out of the body
kidney secretes a very concentrated urine
Major source of water loss in terrestrial animals
3 kinds
evaporation from respiratory surfaces/body surface
urine excretion
feces elimination
Water loss recoup of terrestrial animals
air, food, and what else?
Drinking water (if available)
Harvesting water vapor from air
Free water in food
Metabolic water (oxidation of stores carbs and fats produces water)
Terrestrial animal water loss minimization?
Concentrated urine
Dry feces
Convert Nitrogenous waste to urea or uric acid
Amino acids to energy creates what?
Nitrogenous wastes
Ammonia
What uses this form of nitrogenous waste?
Qualities?
Aquatic animals
Highly soluble, toxic, quickly flushed if enough water is available
500 mL water to 1g of nitrogen waste
Fish are not concerned with water conservation mostly
Urea
What uses this?
Qualities?
Amphibians, mammals
Fairly simple compound, relatively nontoxic, soluble
50 mL water to 1g of Nitrogen waste
Requires energy to convert ammonia to urea (15% of energy gained by amino acids is spent doing this)
Ureotelic
Urea excreting in urine
Uric acid
What uses this?
Qualities?
Birds, insects, reptiles
More complex than urea
More energetically expensive to produce than urea
highly insoluble in water
<10 mL of water per 1 gram of Nitrogen wasteW
Why do birds use uric acid
Keeps body-weight low and conserves water
Many animals have excretory organs for urea and uric acid but why doesn’t ammonia require one (some still have them even if they make ammonia)
Ammonia is a small enough molecule to diffuse out of the body via respiratory membranes or body surfaces
Label this
Pathway of filtrate through nephron
Bowman’s capsule -> p conv tubule -> loop of henle -> distal conv tubule -> collecting duct -> renal pelvis -> ureter
Renal corpuscle
Glomerulus and bowman’s capsule
Cortex vs Medulla
Cortex is outer, Medulla is inner
Urine is composed of
Water, Urea, Excess ions
Kidneys receive _ % cardiac output
Kidneys filter _ liters of blood
20-25
200 liters of blood
Nephron blood supply
Aorta -> renal artery -> afferent arteriole -> glomerulus -> efferent arteriole -> renal vein -> inferior vena cava
4 steps of urine formation
Glomerular filtration
tubular reabsorption
tubular secretion
water excretion/concentration of urine
Glomerular filtrations
occurs because…
___ slits….
Produces…
What kind of process is it?
Occurs due to hydrostatic pressure in the glomerulus
Filtration slits allow water and small ions to leave
Produces protein-free filtrate
Non-selective (200L is formed daily)
Tubular reabsorption
Reclamation?
Primarily occurs where? to what?
_% reabsorbed?
what is reclaimed nearly entirely?
Happens due to _
What does water do?
Reclamation of valuable materials from the filtrate to peritubular capillaries
Primarily occurs in the prox conv tubule
~60%
glucose, amino acids, vitamins
Active transport (unique ion pumps gather ions)
Water passively follows the osmotic gradient with active reabsorption of solutes
Tubular secretion
Primarily occurs where?
Materials end up where?
-Nephron secretes materials into the filtrate (reverse of tubular reabsorption)
-Occurs in dist conv tubule
-Active transport of hydrogen ions,
potassium ions, and drugs
In the urine
Water excretion/Conservation
Kidney closely regulates the solute concentration of the blood
When fluid intake is high/low?
high - dilute urine
low - conc urine
Mammalian adaptation?
descending/ascending permeability?
Collecting duct permeability
Loop of henle
Descending is permeable to water, not NaCl
Ascending is permeable to salt, not NaCl
Variably permeable to water depending on ADH; permeable to urea
Conc gradient of nephron
Cortex is low osmolarity
Medulla gets extremely concentrated osmolarity as it gets lower towards the descending loop of henle
Two ways of concentrating urine
Increasing solute concentration
Decreasing water concentration (decreasing solvent concentration)
Sodium moves out of the ascending loop via…. in the upper portion
lower portion
upper portion, via active transport
lower portion, via diffusion
What happens if water diffuses out of collecting duct
What is fluid entering the collecting duct
What does urea diffusing out of CD do
Urine becomes more concentrated
Dilute
Increases solute concentration of interstitial fluid
ADH
increases permeability of collecting ducts to water, causing water retention
Water gain for kangaroo rats, humans?
Water loss?
Metabolic water vs. Drinking
Evaporation (lungs and skin) vs. Urine
Why do marine fishes have a body fluid salinity that is so much lower than that of the surrounding environment?
They evolve from freshwater fishes, who have a body salinity of 180 mM
Where do nitrogenous wastes come from?
Why is it important to rid of them?
Amino acid metabolism. It is important to get rid of nitrogenous wastes because buildup in the body can cause toxicity.
Describe osmoregulatory challenges of these 5 organisms, explain how they meet those challenges
Spider crab in 200 mM water (op ocean invert)
Blue crab (brackish water crab) in 200 mM water
Modern freshwater bony fish in FW 5 mM
Marine bony fish in normal seawater 550 mM
Desert lizard on land
Spider crab dies because it is stenohaline
Blue crab (550 mM in brackish) - (passive salt loss, water gain) Green glands move water out, Salt-secreting glands take salt in from the environment
Modern freshwater bony fish - (passive salt loss, water gain) Dilute urine, Eating foods with salts, Salt-absorbing cells move salts in
Marine bony fish - (passive salt gain, water loss) Drink seawater and retain the water while excreting the salt, Concentrated urine
Desert lizard on land - (water loss to evaporation, urine excretion, feces excretion) - Absorb water vapor, concentrated uric acid, retain water well from metabolism
Terrestrial animals convert ammonia to urea or uric acid. Mammals primarily excrete nitrogenous wastes in the form of urea, whereas birds, reptiles, and terrestrials insects excrete most nitrogenous waste in the form of uric acid. Why do you support that there is a diversity of strategies? Why don’t all animals convert nitrogenous wastes to uric acid?
Some animals can afford to spend more water and have a more soluble option in their excretion pathway rather than having a very insoluble uric acid that costs a lot of energy to generate. Also, birds need to be lightweight so they need to minimize water loss. Uric acid is a great way to minimize water loss, so if that is a survival characteristic, then it would be necessary; however, that is not always the case.
Define/Relate
Homeostasis/ Osmoregulation
Stenohaline/Osmoconformer
Euryhaline, hyperosmotic regulator
Homeostasis - the tendency to remain stable internally in the face of external fluctuations
Osmoregulation - the maintenance of constant osmotic pressure in the fluids of an organism by the control of water and salt concentrations
Osmoregulation is a system of regulating salt and water balance that maintains homeostatic conditions, thus maintaining homeostasis.
Stenohaline - Able to survive in a narrow range of salinities
Osmoconformer - The ability to maintain an osmolarity internally that is in sync with the environment
These are both describing the ability to survive in an environment which requires relative osmolarities to be a key factor in survival. One is an inability to regulate osmolarity to the point where it cannot survive big changes, whereas the other is describing the ability to conform its internal environment to mimic that of the external environment.
Euryhaline - Euryhaline is the ability to survive a cross a wide range of salinities
Hyperosmotic regulator - The ability to maintain a high internal osmolarity in a low osmolarity environment
These are both describing the ability to survive in an environment which requires relative osmolarities to be a key factor in survival, and both of these characteristics are describing an ability to survive in waters where external environments are different relative to one’s internal environment. For example, euryhaline could survive a significant change in its external environment and still survive since it can survive in a wide range of salinities. Hyperosmotic regulators work to survive in an external environment that is different from its own internal environment constantly.
Nearly 200 liters (50 gallons) of filtrate are formed each day by the average human’s kidneys,
yet we urinate considerably less urine than that. How is the filtrate modified before it leaves
the body as urine?
Filtrate is reabsorbed and concentrated with wastes in the nephron. In the proximal convoluted tubule, vital nutrients are reabsorbed along with a lot of water passively going down its concentration gradient with the actively transporting ions/molecules. Water is reabsorbed in the descending loop of Henle down its concentration gradient. Water is also reabsorbed in the collecting duct when ADH is present.
Describe the role of each of the following parts of the nephron:
a. distal convoluted tubule
b. loop of Henle
c. proximal convoluted tubule
d. glomerulus
e. Bowman’s capsule
Distal convoluted tubule - tubular reabsorption - where 60% of filtrate is reabsorbed
Loop of henle - Water is reabsorbed as well as NaCl
Proximal convoluted tubule - tubular secretion occurs here where waste products are placed in the filtrate from the interstitial fluid (protein-free)
Glomerulus - Where a big blood vessel meets a little blood vessel, causing hydrostatic pressure to shoot filtrate into the bowman’s capsule
Bowman’s capsule - allows a place for filtrate to be collected, as it is being released from the glomerulus
Together, the glomerulus and Bowman’s capsule create the renal corpuscle
What is meant by tubular reabsorption? Why is this an important process?
Tubular reabsorption is the reabsorption of water, amino acids, and sugar from the filtrate, and it is done in the proximal convoluted tubule via active transport. This process is important because reclamation of important materials from the filtrate enables us to actively filter out waste products more effectively and not waste valuable nutrients.
What is meant by tubular secretion? Why is this an important process?
Tubular secretion is important because this is an opportunity for the filtrate to be concentrated with waste products from the body. Without this process, H+, K+, and drugs would not be incorporated in this step.
Why do some desert animals (such as the kangaroo rat) have such long loops of Henle?
Desert animals have longer loops of henle to limit the amount of water and salt that they lose, so its increased length allows the loop of henle to extend deeper into the medulla, where more water and salt can be pulled out of the filtrate.
Why does drinking too much alcohol result in dehydration? (Hint: think about the role of
antidiuretic hormone here.)
Alcohol inhibits ADH, thus not allowing it to act on the collecting duct and make it permeable to water. As a result, water loss is more extreme while it is inhibited and dehydration is exacerbated.
