Bio ch. 44
Which of the following statements best describes the actions of the hormone ADH of the nephron?
ADH causes the collecting duct to increase water reabsorption by the surrounding tissue under conditions of dehydration
Increases water reabsorption
ADH secretion, dehydration due to inadequate water intake, sweating, eating salty food
B
Filtrate is formed as fluid is forced through the walls of the glomerulus and, initially, collects in the structure indicated by the letter
The distal tubule regulates the
K+ and NaCl concentrations of body fluids, the controlled movement of ions contributes to pH regulation
The two primary solutes affecting osmolarity are
NaCl and urea
E
The urethra is identified by the letter
Glucose is removed from filtrate by
active transport
Increases both water and Na+ reabsorption
aldosterone release, blood loss, severe diarrhea
Freshwater fish excrete nitrogenous wastes as
ammonia
Animals that excrete nitrogenous wastes as
ammonia need access to lots of water
Nitrogenous wastes excreted depend on
an animal's evolutionary history, habitat, environment of the animal egg
A decrease in the volume of urine excreted would be expected following
an increase in aquaporin channels in collect duct
Urine is hypersomotic to
body fluids
Reabsorption of water continues through
channels formed by aquaporin proteins
Antidiuretic hormone (ADH) makes the____permeable to water
collecting duct
Urea diffuses out of the
collecting duct as it traverses the inner medulla
The renin-angiotensin-aldosterone system (RAAS) is part of a
complex feedback circuit that functions in homeostasis
Birds have shorter loops of Henle but
conserve water by excreting uric acid instead of urea
The mammalian kidneys ability to
conserve water is a key terrestrial adaptation
The outer part of the kidney is the
cortex
Does not increase water or Na+ reabsorption
diabetes insipidus, alcohol consumption, caffeine consumption
Urea and NaCl form the osmotic gradient that
enables the kidney to produce urine that is hyper osmotic to the blood
Uric acid is more
energetically expensive produce than urea
Osmoregulators expend
energy to control water uptake and loss in a hyper osmotic or hypo osmotic environment
Osmoregulators must
expend energy to maintain osmotic gradients
The collecting duct carries
filtrate through the medulla to the renal pelvis
In the proximal tubule,
filtrate volume decreases but its osmolarity remains the same
The movement of substances out of the glomerulus and into Bowman's capsule is referred to as
filtration
Kidneys, the excretory organs of vertebrates
function in both excretion and osmoregulation
Osmoregulation in marine fish
gain of water and salt ions from food through mouth; excretion of salt ions from gills; osmotic water loss through gills and other parts of body surface; excretion of salt ions and small amounts of water in scanty urine from kidneys
Osmoregulation in a freshwater fish
gain of water and some ions in food; uptake of salt ions by gills, osmotic water gain through gills; excretion of salt ions and large amounts of water in dilute urine from kidneys
The counter current multiplier system in the nephrons of mammalian kidneys allows the development of a concentration gradient of salt and urea in the medullary fluid that is
high enough to develop hyper osmotic urine
Movement is driven by the
high osmolarity of the interstitial fluid, which is hyper osmotic to the filtrate
What is the driving force for the filtration of blood by the renal corpuscle?
higher pressure in glomerular capillaries than in surrounding Bowman's capsule
Marine bony fishes are
hypo osmotic compared with their environment; their kidneys have small glomeruli and some lack glomeruli entirely; filtration rates are low, and very little urine is excreted
Molecules are transported actively and passively from the filtrate into the
interstitial fluid and then capillaries
Osmoconformeers are
isoosmotic with their surroundings and do not regulate their osmolarity
A drop in blood pressure near the glomerulus causes the
juxtaglomerular apparatus (JGA) to release the enzyme renin
The juxtamedullary nephron is
key to water conservation in terrestrial animals
Mammals in dry environment have
long loops of Henle
In which region of the nephron is a steep osmotic gradient created?
loop of Henle
As the filtrate passes through the proximal tubule
materials to be excreted become concentrated
Under the influence of antidiuretic hormone (ADH), _____ is produced
more concentrated urine
As filtrate moves down the loop of Henle, the surrounding interstitial fluid becomes____ concentrated than the filtrate, so____leaves the filtrate
more...water
Osmolarity determines the
movement of water across a selectively permeable membrane
What is the functional unit of a kidney?
nephron
The osmolarity of the urine is regulated by
nervous and hormonal control
Adaptations of desert animals do not likely include
nitrogenous waste excreted as ammonia
Renin triggers the formation
of the peptide angiotensin 2
Other reptiles have
only optical nephrons but also excrete nitrogenous waste as uric acid
Atrial natriuretic peptide (ANP)
opposes the RAAS; ANP is released in response to an increase in blood volume and pressure and inhibits the release of renin
Terrestrial animals are
osmoregulators that must obtain water from the environment
Antidiuretic hormone (ADH) increases the
permeability of the collecting duct epithelium to water; water osmolarity increases, this triggers the release of ADH, which helps to conserve water
Hyperosmotic urine can be
produced only using energy to transport solutes against concentration gradients
Pros and Cons of Urea
pros: less toxic, requires less water cons: energetically expensive
An aquatic animal with an internal solute concentration of 500 mOsm/L is placed in a fluid with solute concentration of about 700 mOsm/L. To osmoregulate and survive, the animal must
pump out salts to keep tissue at 500 mOsm/L.
Angiotensin 2
raises blood pressure and decreases blood flow to the kidneys; stimulates the release of the hormone aldosterone, which increases blood volume and pressure
Birds, insects, and many reptiles excrete nitrogenous waste in the form of uric acid, which
reduces water loss compared to other nitrogenous wastes, but requires more metabolic energy to produce
The kidneys are paired organs that
regulate water and electrolyte balance in terrestrial vertebrates
Uric acid is
relatively nontoxic and does not dissolve readily in water
Mammals in fresh water have
relatively short loops
The____are the major blood vessels transporting blood to the kidneys
renal arteries
Which regions of the nephron function independently of hormonal control for the most part?
renal corpuscle, proximal tubule, and loop of Henle
What is the correct sequence of flow through the nephron?
renal corpuslce>proximal tubule>loop of Henle>distal tubule>collecting duct
Urine formed by a kidney collects in the ___before being drained from the kidney by the___and transported to the____
renal pelvis....ureter....urinary bladder
What is able to diffuse from the tubule into the interstitial fluid
salt but not water; filtrate becomes increasingly dilute
Freshwater fishes conserve
salt in their distal tubules and excrete large volumes of dilute urine
Osmoregulatory mechanisms of freshwater fish include
salt uptake in gills and water excretion in urine
The filtrate produced in Bowman's capsule contains
salts, glucose, amino acids, vitamins, nitrogenous wastes, and other small molecules
The fluid with the highest osmolarity is
seawater in a tidal pool
Some toxic materials are actively
secreted into the filtrate
The movement of substances from the blood into the proximal tubule is known as
secretion
What is reabsorbed from filtrate?
sodium chloride, glucose, water and amino acids
Osmoregulation regulates
solute concentrations and balances the gain and loss of water
Excretory systems regulate
solute movement between internal fluids and the external environment
The amount of nitrogenous waste is coupled to
the animal's energy budget
An appropriate group of animals to examine to observe a Malpighian tubule would be
the insects
Mammals and most adult amphibians convert ammonia to
the less toxic urea; produced in the liver and carried to the kidneys
The countercurrent multiplier system involving
the loop of Henle maintains a high salt concentration in the kidney
Considerable energy is expended to maintain
the osmotic gradient between the medulla and cortex
The two solute model explaining urine production in the nephron states that
the transport epithelium in the ascending loop of Henle is relatively impermeable to water
The collecting duct conducts filtrate
through the osmolarity gradient, and more water exits the filtrate by osmosis
Kidney function in amphibians is similar
to freshwater fishes
Water balance is affected by
type of wastes, quantity of waste products
The most abundant solute in urine is
urea (and other nitrogenous wastes)
The primary nitrogenous waste excreted by mammals is
urea, which is less toxic than ammonia
Insects, land snails, and many reptiles including birds mainly excrete
uric acid
What nitrogenous waste has the greatest number of nitrogen atoms?
uric acid
Most excretory systems produce
urine by refining a filtrate derived from body fluids
As a result of the non-selectivity of the kidney's filtration of small molecules
useful substances must be selectively reabsorbed
ADH and RAAS both increase
water reabsorption, but only RAAS will respond to a decrease in blood volume