Ch 44 Flashcards
Where do physiological systems of animals operate
fluid environment
Relative concentrations of water and solutes must be?
Maintained within fairly narrow limits
What is osmoregulation?
Controlling solute concentrations and balancing water gain and loss
What do desert and marine animals face?
Desiccating environments that can quickly deplete body water
How do freshwater animals survive?
Conserving solutes and absorbing salts from their surroundings
What is excretion?
Rids the body of nitrogenous metabolites and other waste products
What is the driving force for movement of water/solutes?
Concentration gradient of one or more solutes across the plasma membrane
What is osmolarity?
Solute concentration of a solution, determines the movement of water across a selectively permeable membrane
What happens if two solutions are isoosmotic?
Water molecules will cross the membrane at equal rates in both directions
If two solutions differ in osmolarity, the net flow of water is?
From hypoosmotic to hyperosmotic solution
Hypoosmotic
Less concentrated
Hyperosmotic
More concentrated
Osmoconformers
Isoosmotic with their surroundings and do not regulate their osmolarity
Osmoregulators
Expend energy to control water uptake and loss in a hyperosmotic or hypoosmotic environment
Stenohaline
Cannot tolerate substantial changes in external osmolarity
Steno
narrow
Haline
salt
Euryhaline
Can survive large fluctuations in external osmolarity
Eu
true
Most marine invertebrates are
Osmoconformers (isoosmotic)
Marine vertebrates are
Osmoregulators
Marine bony fishes are _____ to seawater
Hypoosmotic, water flows from their bodies into the sea water
How do marine bony fishes balance water loss? (2)
1) Must drink large amounts of seawater
2) Eliminate salts through their gills and kidneys
Osmoregulation is frequently coupled with?
elimination of nitrogenous waste products like urea
Sharks have high concentration of what in their bodies?
Urea
How do sharks protect themselves from the high amounts of urea in their bodies?
they contain trimethylamine oxide that protects them from its denaturing effect
Explain how sharks osmoregulate (2)
1) Take in water by osmosis and food
2) Excess water and salt are disposed in urine
Why do freshwater animals constantly intake water?
because of osmosis from their hypoosmotic environment
Freshwater animals osmoregulate in terms of salt?
1) They lose salt by diffusion and have to maintain balance by drinking NO water and excreting large amounts of dilute urine
2) Salt gets replaced by food uptake and across the gills
Anhydrobiosis
Lose all their body water and survive in dormant state
An
without
Hydro
water
bios
living
Tardigrades
Dehydrate from about 85 percent water to 2 percent water in dehydrated, inactive state
Land animals traits to reduce water loss (4)
1) Body coverings of most terrestrial animals prevent dehydration
2) Desert animals get major water saving from anatomical features and nocturnal lifestyle
3) Eating moist food
4) Producing water metabolically through cellular respiration
Osmoregulators must expend _____ to maintain osmotic gradients
energy
What determines the amount of energy usage (3)
1) animals osmolarity compared to its surroundings its surroundings
2) efficiency of water and solute movement across the animal’s surface
3) The work required to pump solutes across the membrane
What is Transport epithelia?
Epithelial cells specialized for controlled movement of solutes in specific directions
How are transport epithelia usually arranged
In complex tubular networks
Ex. Nasal glands of marine birds
What is the most significant waste?
Nitrogenous breakdown products of proteins and nucleic acids
What are the 3 different forms of waste?
ammonia, urea, uric acid
Differ in toxicity and energy cost of producing
Characteristics of Ammonia
energy required for production: none
amount of water for excretion: high
toxicity of waste: high
ex) Most aquatic animals; invertebrates will release ammonia across whole body surface
Traits of Urea
energy required for production: moderate
amount of water for excretion: moderate
toxicity of waste: low
In vertebrates, where is urea produced?
the liver, then its taken to the kidneys via circulatory system
Traits of Uric Acid
energy required for production: high
amount of water for excretion: low
toxicity of waste: low
ex) birds and reptiles
What can mammals produce as a metabolic byproduct?
gout: painful joint inflammation
Key functions of most excretory systems (4)
1) Filtration: Filtering of body fluids
2) Reabsorption: Reclaiming valuable solutes
3) Secretion: Adding nonessential solutes and wastes to the filtrate
4) Excretion: Processed filtrate containing nitrogenous wastes is released from the body
Protonephridium (2)
1) Network of dead-end tubules that branch throughout the body, contain flame bulbs
2) excrete dilated fluid and functions in osmoregulation
Metanephridia
1) Consist of tubules that collect coelomic fluid
2) Produce dilute urine for excretion
ex) earthworm
Malpighian tubules (2)
1) Removes nitrogenous waste from hemolymph
2) excretes uric acid
Kidneys (2)
1) The excretory organs of vertebrates
2) Functions in both excretion and osmoregulation
The filtrate produced in Bowman’s capsule contains?
hydrogen, bicarbonate, water, salts, glucose, amino acids, vitamins, nitrogenous wastes
explain filtrate movement through the Proximal Tubule
1) Reabsorption of bicarbonate, water, K+, salt, glucose, and amino acids
2) secretion of toxins and drugs, H+ and waste
3) exchange between peritubular capillaries and proximal tubule
How does filtrate volume and solute concentration change in the proximal tubule?
1) Filtrate volume decreases as water and salt are reabsorbed
2) Osmolarity stays the same
explain filtrate movement through the Descending limb of the Loop of Henle
Reabsorption of water continues through channels formed by aquaporin proteins
How does solute concentration change in the descending limb of the loop of Henle?
Solute concentration increases
explain filtrate movement through the lower part of the Ascending limb of the Loop of Henle
Salt but not water is able to diffuse from the tubule into the interstitial fluid (passively)
explain filtrate movement through the upper part of the Ascending limb of the Loop of Henle
Salt is actively transported out of the filtrate
How does solute concentration change in the ascending limb of the loop of Henle?
Filtrate becomes more dilute
- reabsorption of salt maintains high osmolarity in interstitial fluid
explain filtrate movement through the Distal Tubule
1) reabsorption of salt and water
2) reabsorption of bicarbonate and excretion of H+ maintain pH
3) secretion of K+, drugs and poison
explain filtrate movement through the Collecting Duct
reabsorption of salt, and water
Urea filters out of the duct and water follows
Hyperosmotic urine can only be produced
With considerable energy since it transports solutes against concentration gradients
Characteristics of the countercurrent multiplier system
1) Maintains a high salt concentration in the kidney
2) Allows the vasa recta to supply the kidney with nutrients without interfering with the osmolarity gradient
Urine produced is ______ to the interstitial fluid of the inner medulla, but ____ to blood and interstitial fluids elsewhere in the body
Isoosmotic, and hyperosmotic
Juxtamedullary nephron
Key to water conservation in terrestrial mammal animals
Mammals that inhibit dry environements have long or short loops of Henle
Long
characteristics of Birds kidney
Shorter loops of Henle but excrete uric acid instead of urea
characteristics of reptile kidney
Reptiles only have cortical nephrons but reabsorb water from waste in cloaca
characteristics of freshwater fish kidney
Conserve salt in their distal tubules and excrete large volumes of very dilute urine
characteristics of amphibian osmoregulation (2)
1) Conserve salt in their distal tubules and excrete large volumes of very dilute urine
2) Amphibians conserve water by reabsorbing water from the bladder
Marine Bony Fishes osmoregulation (4)
1) Fewer and smaller nephrons
2) Lack distal tube
3) Have small glomeruli or lack it
4) have chloride cells in gills
What controls the osmoregulatory functions of mammalian kidney
Nervous and Hormonal
Contribute to homeostasis for blood pressure and volume
What is ADH
Antidiuretic hormone, also known as vasopressin
Released from the posterior pituitary bind to and activate membrane receptors on collecting duct cells
Initiates signal cascade leading to insertion of aquaporin proteins
Recaptures water which reduce urine volume
Where is ADH released and what does it activate?
Released from the posterior pituitary and binds to and activates membrane receptors on collecting duct cells
Osmoreceptor cells in the hypothalamus do what?
Monitor blood osmoloarity and regulate release of ADH from the posterior pituitary
When osmolarity rises above its set point what happens?
ADH release into the bloodstream increases
What is alcohol?
a diuretic that inhibits the release of ADH
What does RAAS stand for?
Renin-angiotensin-aldosterone-system
What does RAAS do?
a part of a complex feedback circuit that functions in homeostasis in response to BP and volume
How does the Juxtaglomerular apparatus work?
Drop in blood pressure near the GLOMERULUS causes the JGA to release the enzyme renin
What does renin do
Triggers the formation of the peptide angiotensin 1 which is activated into angiotensin 2 by ACE
What does Angiotensin 2 do? (2)
1) Raises blood pressure and decreases blood flow to kidneys
2) Stimulates the release of the hormone aldosterone from the adrenal gland
What does aldosterone do? (2)
1) increase blood volume and pressure
2) increases sodium reabsorption in distal nephron through increasing gene expression of ENaC
Difference between ADH and RAAS
Both increase water reabsorption but RAAS will respond to a decrease in blood volume
What does ANP stand for?
atrial natriuretic peptide
Where is Atrial natriuretic peptide produced
Found in the atria of the heart
What does the atrial natriuretic peptide respond to? and what does it do?
released in response to an increase in blood volume/pressure
inhibits the release of renin
