controlling the internal environment (kidneys) Flashcards
what are the two ways that animals can manage their internal environment
they either conform or regulate
what is a regulator
an animal that uses internal mechanisms to control internal change in the face of external fluctuation
what is a conformer
an animals who’s internal conditions change in accordance with external changes
can an animal regulate some internal conditions while allowing others to conform to the environment
yes - e.g. largemouth bass conforms to the temperature of the surrounding water but it regulates the solute concentrations in its blood and interstitial fluid
the steady temperature of a river otter and the stable concentration of solutes in a bass are examples of what
homeostasis
what does homeostasis mean
the maintenance of a constant internal environment
what are examples of homeostasis in humans
temperature regulation
blood pH regulation
blood glucose concentration regulation
what is the normal range of blood glucose concentration per 100ml blood
70-110mg glucose
what does homeostasis require
control system
in homeostasis the response reduces/dampens the stimulus what kind of feedback response is this
negative feedback
are physiological responses to stimuli instantaneous
no - homeostasis moderate but does not eliminate changes in the internal environment
what would positive feed back involve
amplification of the stimulus - generally not in animal homeostasis but in other processes e.g. giving birth - stimulus drives completion of process
in all mammals and plants, certain cyclic alterations in metabolism reflect what
a circadian rhythm
what is a circadian rhythm
a set of physiological changes that occur every 24 hours - e.g. the body clock
which hormone is secreted at night
melatonin
can external stimuli reset the biological clock
yes - but it takes a while, this is why we get jet lag
what is jet lag
a miss match between the circadian rhythm and local environment that persists until the clock fully resets
acclimatization can alter homeostasis, what is it
an animals physiological adjustment to changes in its external environment e.g. when an elk moves up into the mountains from sea level, the lower oxygen concentration stimulates the animal to breathe more rapidly and deeply. As a result more CO2 is lost through exhaling, raising the blood pH above its normal range
is acclimatization a permanent or temporary change
temporary
how is the fluid balance of tissues maintained
relative concentrations of water and solutes are kept within fairly narrow limits. ions must be maintained at concentrations that permit normal activity of muscles, neurons and other body cells
homeostasis requires osmoregulation, what is this
the processes by which animals control solute concentration and balance water gain and loss
in order to safeguard their body fluids freshwater animals must deal with what toxic metabolite
ammonia
which process remove nitrogenous waste and other metabolic waste products
excretion
if water uptake to cells is excessive what happens to them
they can burst
if water loss from cells is substantial what can happen to them
they shrivel and die
what is the ultimate driving force for the movement of water and solutes
a concentration gradient of one or more solutes across the plasma membrane
water enters and leaves cells by which process
osmosis
what is the unit of measurement for solute concentration
osmolarity (the number of moles of solution per litre of solution)
what is the osmolarity of human blood
300mOsm/L
two solutions with the same osmolarity are said to be what
isosmotic
what is a hyperosmotic solution
the solution with the higher concentration of solutes
low free H2O concentration
what is a hypoosmotic solution
the solution with the lower concentration of solutes
high free H2O concentration
in which direction does water flow by osmosis:
hyperosmotic to hypoosmotic
hypoosmotic to hyperosmotic
hypoosmotic to hyperosmotic - reducing the concentration difference in solutes and free water
what are the two ways that an animal can maintain water balance
either by being an osmoconformer or an osmoregulator
which term defines the relationship between the osmolarity of the an osmoconformer to its surroundings
isosmotic - internal osmolarity is the same as that of the external environment
many osmoconformers life in an environment that has a stable composition so they will have a stable internal environment
what does an osmoregulator do
control their internal osmolarity, independent of that of the external environment
can osmoconformers move between freshwater and marine (sea water) environments
no they are all marine animals
can osmoregulators move between freshwater and marine (sea water) environments
yes
in a hypoosmotic environment an osmoregulator must discharge/take in water
discharge - the water is going to flow into them so in order to maintain a constant internal environment they need to combat this by discharging the excess water
in a hyperosmotic environment an osmoregulator must discharge/take in water
take in - the water is going to flow out of them so in order to maintain a constant internal environment they need to combat this by taking in water
what does it mean if an organism is stenohaline
they cannot tolerate substantial changes in external osmolarity
what does it mean if an organism is euryhaline
it can survive large fluctuations in external osmolarity
most marine invertebrates are osmoconformers/regulators
osmoconformers
invertebrate marine osmoconformers have not trouble in water balance but they must actively transport specific solutes that establish what
levels in haemolymph (circulatory fluid) different form those in the ocean
marine bony fish constantly lose water by osmosis, they balance water loss by drinking a lot of sea water. how are the excess salts ingested eliminated
through the gills and the kidneys
osmoregulation is frequently coupled to elimination of what
nitrogenous waste products e.g. urea
why must urea be eliminated
high concentrations can denature proteins and thus disrupt cellular functions
sharks have high concentrations of urea in their body. how do they survive
trimethylamine oxide (TMAO) is produced by sharks and it protects proteins from the denaturing effect of urea
as well as protecting sharks from the effects of urea, what else is TMAO responsible for
osmoregulation
how does TMAO participate in osmoregulation
sharks have a lower salt content than sea water
salt tends to diffuse into their bodies, especially across the gills
the combination of TMAO with salts and urea results in sharks having a high solute concentration
water then slowly enters the shark by osmosis (they don’t drink)
the body fluids of freshwater animals must be hyperosmotic/hypoosmotic
hyperosmotic
why do the body fluids of freshwater animals need to be hyperosmotic
animal cells cannot tolerate salt concentrations as low as that of lake or river water
freshwater animals have internal fluids with an osmolarity higher/lower than that of their surroundings
higher
why do freshwater animals face problems gaining water by osmosis
because the osmolarity of internal fluids is greater than that of their surroundings their solute concentration is greater and their water concentration is lower leading to and influx of water. this means they have to balance water content to stabilise the influx
how do freshwater organisms with the influx of water into their bodies
they excrete large amounts of very dilute urine and they drink almost all water. slats lost by diffusion and in urine are replenished by eating and uptake across their gills
what is another word for extreme dehydration
desiccation
when ponds dry up what is the dormant stage that animals enter without water
anhydrobiosis
what adaptations does anhydrobiosis require
ones that keep cell membranes intact or else they would shrivel up and die
adaptations that reduce/increase water loss are key to survival on land
reduce
how do land animals maintain water balance
by drinking and eating moist foods and by producing water metabolically through cellular respiration
in most animals, osmoregulation and metabolic waste disposal rely on what for moving particular solutes in controlled amounts in specific directions
transport epithelia
what is transport epithelia
one or more epithelial cells specialized for moving particular solutes in controlled amounts in specific directions
why do humans become dehydrated when they drink salt water
they must use a greater volume of water to excrete the salt load so there is a net loss of water from the body
even though drinking sea water brings a lot of salt, the salt glands enable marine invertebrates to achieve a net gain/loss of water
gain
what functions does the kidney have
osmoregulation and excretion
what do the kidneys consist of
tubules , ducts and other structures
how are kidney tubules arranged
in an organised manner and are closely associated with a network of capillaries
are kidneys typically segmented or non segmented
non segmented
how many kidneys are in the body
2
urine produced in the kidneys exits through a duct called the ……………..
ureter
where to the 2 ureters coming from the kidneys drain into
the urinary bladder
during urination, the urine is expelled through a tube called the ……………, which empties to the outside of the body
urethra
what structure regulates urination
sphincter muscles near the junction of the urethra and bladder
each kidney has an outer ………… ……….. and an inner …….… …………
renal cortex
renal medulla
what are the outer renal cortex and inner renal medulla supplied with blood by
the renal artery
what are the outer renal cortex and inner renal medulla drained by
the renal vein
what structures are packed inside the cortex and the medulla
tightly packed excretory tubules and associated blood vessels
what do the excretory tubules do
carry and process a filtrate produced form the blood entering the kidney
nearly all of the fluid in the filtrate is reabsorbed into the surrounding ………. ………. and exits the kidney in the renal vein
blood vessels
the remaining fluid in the excretory tubules leaves as ..……..
urine
the urine is collected in the inner …………. ………… and exits the kidney via the ureter
renal pelvis
weaving back and forth across the renal cortex and medulla are the …………….
nephrons
what structures are the functional units of the vertebrate kidneys
nephrons
85% of the nephrons are ……………… nephrons which reach only a short distance into the medulla and the remainder are …………………. nephrons which extend deep into the medulla
cortical
juxtamedullary
juxtamedullary nephrons are essential for production of urine that is hyper/hypoosmotic to body fluids, key for water conservation
hyperosmotic
what does a nephron consist of
a single long tubule and a ball of capillaries called the glomerulus
the blind end (a cavity open at one end) of the tubule forms a cup shaped swelling known as the ……………
Bowman’s capsule
what does the Bowman’s capsule surround
the glomerulus
When Is filtrate formed in the nephrons
when blood pressure forces fluid from the blood in the glomerulus into the lumen of Bowman’s capsule
how is the filtrate processed
as it passes through the 3 major regions of the nephron: the proximal tubule, the loop of henle (a hairpin turn with a descending limb and an ascending limb) and the distal tubule
what are the 3 major regions of the nephron
proximal tubule
loop of henle
distal tubule
what receives the processed filtrate from the nephrons and transports it to the renal pelvis
collecting duct
each nephron is supplied with blood by an …………. arteriole, an offshoot of the renal artery that branches and forms the capillaries of the glomerulus
afferent
as the capillaries leave the glomerulus, they converge, forming the …………. arteriole
efferent
branches of the efferent arteriole form the …………….. capillaries
peritubular
peritubular capillaries surround the ……………… and …………….. tubules
proximal
distal
other branches of the peritubular capillaries extend downward to the loop of henle and form the ……….. …….….
vasa recta
what are the vasa recta
hairpin shaped capillaries that serve the renal medulla, including the loop of henle of juxtamedullary nephrons
the glomerular capillaries and specialized cells of the bowman’s capsule retain blood cells and large molecules, such as plasma proteins, but are permeable to ……. and small …………
water
solutes
the filtrate produced in the Bowman’s capsule contains what
salts, glucose, amino acids, vitamins, nitrogenous waste and other small molecules - the concentration of these molecules id the same in the initial filtrate as in the blood plasma because they all pass freely between the glomerular capillaries and the Bowman’s capsule
reabsorption in the proximal tubule is critical for the recapture of what form the large volume of the initial filtrate
ions, water and valuable nutrients
NaCl in the filtrate enters the cells of the transport epithelium by ………. ………… and cotransport mechanisms . it is then transferred to the interstitial fluid by ……….. …………..
facilitated diffusion
active transport
the transport of positive charge out of the tubule drives the passive transport of what
chlorine ions
as salt moves from the filtrate to the interstitial fluid, what follows, resulting in a considerable reduction in filtrate volume
water follows by osmosis
the salt an water that exit the filtrate, diffuse from the interstitial fluid into what
the peritubular capillaries
what other substances as well as salt and water are also transported from the filtrate to the interstitial fluid into the peritubular capillaries
glucose, amino acids, potassium ions etc.
processing of the filtrate in the proximal tubule helps maintain a relatively constant ……… in the body fluids
pH
how is pH controlled
cells of the transport epithelium secrete H ions into the lumen of the proximal tubule and also synthesise and secrete ammonia which acts as a buffer to trap H ions in the form of ammonium ions
the more acidic the filtrate is, the more…………the cells produce and secrete and the animals urine usually contains some ammonia from this source (even though most nitrogenous waste is excreted as urea
ammonia
the proximal tubules also absorb about 90% of what from the filtrate, contributing further to pH balance in body fluids
buffer bicarbonate
as the filtrate passes through the proximal tubule, the materials to be excreted become ………….
concentrated
what can be secreted into the filtrate from the surrounding tissues
drugs and toxins that have been processed in the liver can pass from the peritubular into the interstitial fluid then secreted by the transport epithelium into the lumen of the proximal tubule
where does the filtrate g after leaving the proximal tubule
the loop of henle
what happens to the filtrate in the loop of henle
filtrate volume is reduced via distinct stages of water and slat movement
what is the first portion of the loop of henle called and what happens here
the descending limb
numerous water channels formed by aquaporin proteins make the transport epithelium freely permeable to water. In contrast there are almost no channels for salt and other small solutes, resulting in very low permeability for these substances
for water to move out of the tubule by osmosis, what must the osmolarity of the interstitial fluid bathing the tubule be compared to the filtrate
hyperosmotic
the osmolarity of the interstitial fluid increases/decreases progressively form the cortex through the medulla
increases - as a result the filtrate loses water and increases in solute concentration along its journey down the descending limb
where is the osmolarity of the filtrate highest
at the elbow of the loop of henle
once the filtrate reaches the tip of the loop where does it return to
the cortex via the ascending limb
unlike the descending limb, the ascending limb has a transport epithelium that lacks what type of protein
water channels
the epithelium membrane that faces the filtrate in the ascending limb is permeably to what
water
what are the two specialised regions of the ascending limb
a thin segment near the loop tip and a thicker segment adjacent to the distal tubule
as the filtrate ascends in the thin segment of the ascending limb what diffuses out of the permeable tubule and into the interstitial fluid
NaCl
in the thicker segment of the ascending limb NaCl movement out of the tubule also occurs but in what way is the movement different from that in the thin segment
the NaCl is actively transported instead of passively diffusing
what essentially happens to the filtrate in the ascending limb of the loop of henle
the filtrate loses salt but not water and so the filtrate becomes more dilute as it moves up to the cortex in the ascending limb
what does the distal tubule play a key role in regulating
the concentration of potassium ions and NaCl in the body fluids
also pH regulation
how does the distal tubule regulate potassium ion and NaCl concentration
it can vary the amount of potassium secreted into the filtrate as well as the amount of NaCl reabsorbed from the filtrate
what is the role of the collecting duct
it processes the filtrate coming the distal tubule into urine which it carries to the renal pelvis
in the collecting duct the filtrate becomes increasingly …….……., losing more water by osmosis to the hyper/hypoosmotic interstitial fluid
concentrated
hyperosmotic
in the inner medulla the collecting duct becomes permeable to what
urea
urine is hyper/hypoosmotic to the general body fluids
hyperosmotic
what is the presence of water channels in the collecting duct epithelium controlled by
hormones that regulate blood pressure, volume and osmolarity
filtrate passing from Bowman’s capsule to the proximal tubule has the same osmolarity as what
the blood
what is reabsorbed from the filtrate as it flows through the proximal tubule in the renal cortex
salt and water - the filtrate volume decreases but the osmolarity remains the same
as the filtrate flows from the cortex to the medulla via the ………….. …………… water leaves the tubule by osmosis
descending limb
what does the reabsorption of water in the descending limb result in
solutes become more concentrated increasing the osmolarity of the filtrate
where is diffusion of salt out of the loop of henle at its maximal
at the elbow of the loop
the ascending limb of the loop of henle is permeable to ..………. but not ……………
salt - this helps maintain a high osmolarity in the interstitial fluid of the renal medulla
water
what is the countercurrent system
the loop of henle and the surrounding capillaries act as a type of countercurrent system too generate the steep osmotic gradient between the medulla and the cortex
the transport of NaCl in the upper thick part of the ascending limb is passive/active
active - this transport maintains a high salt concentration in the interior of the kidney enabling it to form concentrated urine
countercurrent multiplier systems expend ………… to create a ………….. ………….
energy
concentration gradients
the ascending and descending vessels of the vasa recta carry blood in ………… …………. through the kidneys osmolarity gradient
opposite directions
the kidney has one of the highest/lowest metabolic rates or any organ
highest
dues to active transport of NaCl out of the ascending limb the filtrate is hypo/hyperosmotic to body fluids by the time it reaches the distal tubule
hypoosmotic
the collecting duct is permeable to …….. but not to …….…..
water
salt
animals that excrete the most hyperosmotic urine have many ………………. nephrons that extend deep into the medulla
juxtamedullary
aquatic animals have mostly cortical nephrons which results in production of dilute/concentrated urine
dilute
in mammals, urine volume and osmolarity are adjusted depending on what
he animals water and salt balance and its rate of urea production
describe the urine produced when an animal’s salt intake is high but its water availability is low
excretion of small volumes of hyperosmotic urine with minimal water loss (this is how the urea and salt are removed form the body)
describe the urine produced when an animal’s salt intake is low but its water availability is high
excretion of large volumes of hypoosmotic urine (the excess water is eliminated with little salt loss)
what manages the osmoregulatory function of the kidney
a combination of nervous and hormonal controls
what is the key hormone of the kidneys
Antidiuretic hormone (ADH)
where is ADH released from
the posterior pituitary
What does ADH activate
it binds to active membrane receptors on the surface of the collecting ducts. the receptors then initiate a signal transduction cascade that directs insertion of aquaporin proteins into the membrane lining the collecting duct.
more aquaporin channels result in more water recapture. what is the effect on the volume of urine
because the water is reabsorbed by the body the volume of urine decreases and we are left mainly with a concentrated mixture of solutes
what is the response when osmolarity rises above the normal range
osmoreceptor cells in the hypothalamus trigger release of ADH from the posterior pituitary
water reabsorption in the collecting duct is increased
the result is increased concentration urine, decreased urine volume and decreased blood osmolarity back the set point.
what is the response when osmolarity goes below the normal range
a negative feedback mechanism reduces the activity of the osmoreceptor cells in the hypothalamus and ADH secretion is reduced
how does alcohol affect ADH release
it inhibits its release, leading to excessive urinary water loss and dehydration - causing a hangover
what is the disorder called that results in no ADH production or inactivated ADH receptors (dues to mutations in genes that render them inactive)
diabetes insipidus - it causes severe dehydration and solute imbalance due to production of huge volumes of very dilute urine
what is heterothermy
when some parts of the body are warmer than others
what would be an example of behavioural temperature regulation in ectotherms
lizards basking in the sun
A solution with few solutes in it will have lower/higher osmotic pressure than one with many solutes.
lower
water will move from a low/high to a high/low osmotic pressure system
low
high
what is ammonia secreted as in birds
uric acid/guano
what is ammonia released as in fish
ammonia/ammonium
what is ammonia released as in mammals
urea
where are the kidneys
located against the back wall of the abdomen on either side of the body
what is hydrostatic force
the force a liquid exerts on the walls of its container
what are the steps in countercurrent heat exchange
- Arteries carrying warm blood are in close contact with veins carrying cooler blood.
- Heat from the artery is absorbed by the vein
- As the blood in the veins nears the centre it is almost as warm as the body core
what is another name for ADH
vasopressin
what is countercurrent multiplication
Countercurrent multiplication is the process of using energy to generate an osmotic gradient that enables reabsorption of water from tubular fluid, leading to production of concentrated urine. The ascending limb of the loop of Henle helps to maintain a gradient of salt concentration in the kidney interior.
