Renal Physiology Flashcards
(92 cards)
1
Q
osmolarity (2)
Unit _ what
A
- Number of osmoles (Osm) per liter = Osm/L
- Measurement of total dissolved solutes, solute concentration
2
Q
Cells and organisms need to function in varied environments. Strategies include (2):
A
- Maintaining tight control of internal environment. Organisms that maintain internal environment (Na+, Cl- balance) despite external environment also known as regulators.
- Maintain cellular function while matching the environment. This means they change internal environment to match external and are known as conformers.
3
Q
Osmotic regulation
A
The process by which organisms control the concentration of total dissolved solutes (Na+, Cl-, Ca2+, urea) in their internal fluids to maintain homeostasis.
4
Q
Ionic regulation
A
Control specific ions (Na+ outside, K+ outside)
5
Q
Volume Regulation
A
Certain organisms that bring in excess salt to inflate body (crab) to control volume/size of body via H2O.
6
Q
what is the difference between osmolarity and tonicity?
A
osmolarity refers to both penetrating and non-penetrating solutes, tonicity refers to only non-penetrating solutes
Penetrating solutes can cross the cell membrane freely, either by simple diffusion or through facilitated transport. These solutes do not contribute to the long-term movement of water because they equilibrate across the membrane.
Non-penetrating solutes cannot freely cross the membrane and stay in their respective compartments. Since they cannot move across, they create an osmotic gradient that drives water movement.
7
Q
Osmosis (2)
What + known as a —- process
A
- Diffusion/movement of water from areas of high osmotic pressure (hyperosmotic - more concentrated relative to some other solution) to areas of low osmotic pressure (hypo-osmotic)
- passive process
8
Q
isosmotic
A
no difference in osmotic pressure
Same number of dissolved solute
9
Q
What is the difference between osmotic regulators and conformers?
A
Osmotic regulators maintain a strict constant blood osmolarity regardless of what the external environment looks like, conformers follow isosmotic line (blood osmotic pressure = ambient osmotic pressure)
10
Q
Talk about green crab, mussel, and shrimp in terms of regulator vs conformers (3).
A
Green crab: Relative osmoregulator until extreme then it conforms.
Mussels: isoconformer
Shrimp: Osmotic regulator. Internal osmotic pressure doesnt change very much even though external pressure is increasing.
11
Q
ion regulator
A
Maintenance of a constant concentration of inorganic ions in blood plasma (control specific ions such as Na+ outside)
12
Q
ionic conformer
A
allows concentration of a particular ion species in blood plasma to match the concentration in environment
13
Q
Challenges to freshwater regulators (4)
Situation + challenges (2) + what does result in?
A
- external environment is hypo-osmotic to internal environment
- constantly taking in water through osmosis
- Constantly losing ions (diffusion favour ions from inside to outside)
These two challenges make more dilute and decreases osmotic pressure on inside of organism.
14
Q
Challenges to marine regulators (4)
Environment + 3 challenges
A
- external environment is hyperosmotic to internal environment
- constantly losing water (faces dessication/constant water loss)
- constantly drinking seawater to compensate for water loss (this also causes a load up on ions that needs to be removed)
- Constantly loading ions via high concentration of Na+ and Cl- that diffuse down the gradient
15
Q
Organs of Salt/Water Balance: Gills (3)
Morphology + problem + animals
A
- Has large SA due to folds and very permeable. This benefits to gas exchange (take O2 out of water). O2 is very low and there is lots of contact with water where O2 can be drawn. Amount of O2 in water is low so you need fins.
- Counterproductive for water-salt balance (bad to maintain). Large SA increases osmosis of water. Permeability allows for movement of ions. Doesnt prevent ion leaving and large SA permeability promotes it.
- Animals with high O2 demands (salmon swim rapidly have highly developed gill system) must deal with high water-salt exchange.
16
Q
Gill Anatomy (2)
WHat is on + helps with
A
- MRC or chloride cell sitting on gill epothelia, pavement cells are adjacent to MRC (majority on gill).
- MRC helps deal with challenges presented by having big permeability + SA.
17
Q
Solutions for challenges faced by freshwater regulators (2)
A
- copious amounts of dilute urine counters water uptake (leads to ionic loss)
- MRC active uptake of ions through gills (active transport) to counter ionic loss/dilution
18
Q
Solutions for challenges faced by Marine regulators (2)
A
- MRC move ions out (Push into environment)
- Water loss countered by drinking (take ion in as well)
19
Q
What are the cell types in freshwater gills (2)?
A
1) Pavement cells: 90% of gill epithelium, principally responsible for oxygen uptake
2) Mitochondria rich cells (MRCs): uptake of chloride, sodium, and calcium in freshwater due to some ions diffusing out so MRC uptakes the ions; partially under hormonal control to determine excretion or not, density and type can be changed in varying conditions
20
Q
MRC’s in very “soft” freshwater (low calcium)?
A
This increases osmotic pressure for water to enter fish and dilute ionic concentrations (ion loss), thus MRC density is upregulated and more bigger MRC to counter challenges of ionic loss.
21
Q
What is the goal for MRC in freshwater Gills?
A
Get ions across surface of gill down into blood.
22
Q
Apical membrane and basolateral membrane location
A
- Apical is on the external environment side
- Basolateral membrane is on the blood side.
23
Q
Freshwater Gills
V-type (vacuolar) ATPase
A
Located on apical membrane of MRCs in freshwater gills. Transports H+ out of the cell which leaves the cell with a net negative charge. That attracts + charge ions in the environment like Na+. Once Na+ in MRC, Na/K+ pumps on basolateral get them into bloodstream.
24
Q
Freshwater Gills
Sodium channels
A
Located on apical membrane of MRCs in freshwater gills. Passive movement of Na+ due to electrical attraction.
-negative charge of MRCs due to V-type ATPase attracts cations into the cell passively
25
# Freshwater Gills
Na+ - K+ pump/ATPase
Located on the basolateral membrane of MRCs in freshwater gills, pumps 2Na+ out of MRC and 3K+ into MRC. K+ eventually leaves MRC through K+ leak channels on the basolateral membrane. Transport Na+ ions across basolateral to blood.
26
# Freshwater Gills
Potassium leak channels
Located on the basolateral membrane of MRCs in freshwater gills, helps maintain negative charge of MRC and low intracellular K+ concentration
27
# Freshwater Gills
Electroneutral anion exchanger (3)
| Location + exchanges + mechanism of action
- Found on apical membrane of pavement cells and MRC's.
- Exchanges a bicarbonate ion (-) for a chloride ion (-)
- Driven by buildup of bicarbonate (by-product of metabolism) which causes a driving force for bicarbonate efflux. Bicarbonate binds to intracellular part of protein co-transportor and there is an increased affinity in binding on external side where Cl- binds. HCO3- is released out and Cl- is brought inside. Cl- builds up inside of cell and diffuse due to DF to move out to blood across basolateral membrane via Cl- channels.
28
# Freshwater Gills
Cystic fibrosis transmembrane regulator (CFTR)
- Found on pavement cells and basolateral membrane of MRC's, allows chloride ions to move from cells into the bloodstream
29
Mutations in CFTR results in: (5)
- Results in cystic fibrosis
- Reduces chloride clearance from cells, less Cl- move across membrane into these various cells.
- Maintains a higher than normal electronegative potential in the cells due to less Cl- clearance.
- Reduces extracellular removal of cations (cations also build up inside the cells). This is because inside of the cell more - bc less Cl- leaving so there is strong electromotive force that draw cations to the cell.
- Increased mucosal buildup (higher osmotic pressure because less Cl- and Na+ movement causes water to enter cells) - leads to respiratory and digestive difficulties
30
# Freshwater Gills
Calcium co-transporter and calcium-ATPase (3)
| gradient set up + the 2 channels
- Electronegativity of MRC attract cation (Ca2+) from the water and inside MRC by passing through open channel on apical membrane.
- Calciumm Co-Transporter use DF for sodium to move Na+ into cell and Ca2+ from inside the cell to blood. It exchanges 1 ion for another moving in different directions. DF for Na+ is low in the MRC and higher in the blood so there is a DF to go into the cell. Na+ is futher removed from MRC to blood via Na/K ATPase.
- Calcium ATPase use ATP to bring Ca2+ across the basolateral membrane to blood.
31
What are the effects of drinking seawater?
- water in the gut will be hyperosmotic to blood plasma (will cause water to be drawn out of the blood plasma by osmosis and sodium and chloride ion diffusion into blood plasma due to concentration differences). Net result is very concentrated blood plasma
32
Why can't us humans drink saltwater?
If we drink saltwater it draws H2O from our body into out gut. We need to reverse that so we have to move the ions and then H2O follows so we can get H2O from gut. 1st thing we do is pump a bunch of Na/Cl- from inside gut into the body. We are not good at getting ion to redistribute to blood/body. Marine animals have ability to move ion to plasma via active transport.
33
What are the adaptations of marine fish for the effects of drinking seawater? (3)
- Later parts of the intestine actively transport sodium and chloride ions out of the gut into the blood. This creates a gradient that favours water retention
- 50-85% of water is reabsorbed into the blood
- This means 97% of Na and Cl must be absorbed and removed.
34
How are excess ions removed for marine animals that drink seawater to rehydrate (4)?
| where + 3 ways
Excess ions are removed in the gills. We are trying to get these ions from the blood moved out across the cell and deposited into the environment.
1. NKCC cotransporter on basolateral has high affinity binding site for Na+, K+ and 2 Cl- ions which is abundant in blood. It uses the Na+ DF to move the 4 ions from blood to cell by changing conformation. Chloride buildup in MRC to produce a driving force for chloride to leave the cell. Na+ doesnt accumulate as Na+/K+ pump and K+ leak out so only Cl- build up.
2. Accessory cells adjacent to MRC allows paracellular pathway for the movement of some ions between MRC and accesory cell because negative charge in MRC attracts + ions to the apical membrane which exit to environment out of blood and cell.
3. Active transport of Na+/Cl- out of gut but not for Ca2+. Event though drinking Ca2+ in they are not absorbing it in the same way they do with Na+/Cl-. Calcium Co-transporter and Calcium ATPase help cotransport or actively transport Ca2+ into the blood after it goes through a channel on the apical membrane.
35
Challenges faced by marine birds/reptiles
| Organisms that live in close proximity to salt water
- Blood is hypo-osmotic to seawater
- Faces water loss and salt loading due to ingestion of hyperosmotic water (must remove excess solutes)
36
How do marine birds/reptiles remove excess solutes + decrease water loss (2)?
- Salt glands (secretory cell uses NKCC and paracellular pathway to converge salt ions into lumen of secretory tubule for excretion)
- They have less permeable integument (skin surface) which decreases water loss. Fish and amphibians have very permeable integment for osmosis and O2 through skin.
37
Explain how the salt glands in marine birds work (2):
- The salt glands are located on the forehead then there is connecting ducts for the salt glands to the nostrils where excess Na+ and Cl- is excreted out (rather then the gills). Allows the removal of excess Na+ and Cl- concentration as they drink salt water and get food from environment.
- There is vasculature that surround the secretory cell of transport epithelium (barrier btween the vasculature and inside of salt gland). The goal is to get the Na+ and Cl- from blood into lumen of salt gland. This is done by NKCC co-transporter which use the DF for Na+ (more Na+ in blood then inside cell bc Na+/K+ pump always ensuring that low Na+ is inside of cell) and changes conformation when Na+ binds to deposit all the ions inside the cell (Na+,K+,2Cl-). Cl- builds up and passively move out of the secretory cell of transport epithelium to the lumen. Na+/K+ pump pumps Na+ out and K+ in but K+ leaks out so no buildup. Because buildup of Cl-, the cell potential is negative and cations are drawn due to EMF from blood through paracellular pathways into the secretory tubule/lumen. Bunch of tubule will converge down to the central duct and travel outside at the nostril.
38
Marine Osmoconformers (3)
| who + what + by....
- E.g. sharks, rays, skates (Elasmobranchii)
- Match blood osmotic pressure to marine environment
- Produces high concentrations of organic solutes (urea and TMAO) to match osmopressure without the issue of water loss. They dont just passively bring in all the Na+/Cl- but instead, they load up on other slouts so it matches the environment. There is no net force to move free H2O and less gradient for movement of other solutes.
39
Salmon (3)
| Environment + Behaviour elements + Physiological elements
- Born in freshwater and migrate to seawater to grown, then return to freshwater to reproduce.
- Behvaiour elements that help it transition include spending time in brackish water (mixture of fresh+salt water) before going to SW and reducing the amount of water consumed when it returns to freshwater. This is because freshwater they are constantly taking in water via osmosis.
- Physiological elements that help it transition includes kidney function changes. There will be high volume of dilute urine in FW and little urine in SW. The gills that take up ions in FW will remove them in SW. This is done by upregulating/inserting MRC that are able to deal with SW and removing MRC from the surface of the gill that are best adapted to FW.
40
The greatest challenge to terrestrial organisms is water loss. Sources of water loss (3):
1. Respiratory water loss
2. Evaporative water loss (EWL)
3. Excretory water loss
41
Excretory Water loss (3)
| Importance + composition + water loss source
- Nescessary for getting rid of wate product from metabolism such as nitrogen from catabolism of proteins (urea).
- Composition of urine can be modified. If we have a bunch of wate products that are constantly being produced and we want to lose as little H2O as possible we can load them in a small volume of urine.
- 2nd most abundant source of water loss
42
Evaporative water loss (EWL) (2)
| Determined by + water loss source
- Determined by body size. Smaller animals have higher SA:V ratio, higher metabolisms/respiration rates, higher EWL
- Most abundant source of water loss
43
Urine Concentration modification
1. During times of drought
2. During times of water loading
- During times of drought, water is retained by production of highly concentrated urine (load up waste products in little volume of water)
- During times of water loading, excess water is removed by production of large amounts of dilute urine
44
U/P > 1
- Urine is hyperosmotic and concentrated. Urine produced during times of drought/low water in body system
45
U/P < 1
Dilute urine produced during times of water loading/too much water in body system. Urine is more dilute then blood plasma and you are trying to get rid of excess H2O.
46
U/P = 1
urine is isosmotic to plasma
47
Human UP ratios
- U/P ratio from 0.1 (urine 10x less concentrated then blood plasma) to 4 (urine 4x more concentrated then blood plasma)
48
Talk about the Nephron (3):
| Amount + blood + U/P ratio
- There are around 1 million nephrons per kidney.
- There are vasculature blood flow going to each from the renal artery. The renal atery bring blood to the kidney and the diameter is bigger relative to size of the kidney. The nephorn sit in the renal pyramid, filters blood and reabsorbing ions.
- The ability to have different U/P ratio is due to the function of nephron in renal pyramids.
49
The nephron structure:
50
Which part of nephron in cortex which in medulla?
Cortex:
Connecting tubule, proximal tubule, distal tubule, BC, cortical collecting tubule
Medulla:
Loop of Henle, medullary collecting tubule, collecting duct
51
Glomerulus (2)
| Consist of + structure
- Consist of Bowman's capsule + vasculature surrounding Bowman's capsule.
- Very large arteries comming in and they are diverging quite a bit making contact with multiple places across BC surface.
52
There is a net fluid movememt from blood to BC fluid. Explain why:
There are 3 forces that contributes:
1. Blood pressure in glomerular capillary which is pressure in blood vessel when the heart contracts and favour movement of solute to BC (+6.7 kPa)
2. Colloid osmotic pressure where large plasma proteins that are too large to pass increases osmotic pressure in blood favouring water movement to blood. (-3.5kPa)
3. Capsular fluid hydrostatic pressure. BC have fluid already when you want to add fluid to it, there is resistance. (-1.9kPa)
53
What forms the ultra-filter in Bowman's capsule (3)?
- Capillaries (single endothelial layer with fenestrations aka gaps inbetween cells to allow small solutes to pass)
- Basement membrane (collagen protein that anchor for vessel to be close to BC)
- Podocytes (specialized epithelial cells with branching processes that extend out and make a mesh like lattice to filter larger plasma protein)
54
What contributes to the large hydrostatic pressure outside the tubule?
pressure created by systole
55
Primary urine (2)
| What + blood plasma
- Aqueous solution first introduced into kidney tubules, dissolved solutes nearly identical to the blood (H2O, urea, Na+, Cl-, K+) does not contain large plasma proteins (blood osmotic pressure is higher than capsular fluid bc large proteins do not pass) *Anything that enters BC*
- Nearly isosmotic to blood plasma
56
Definitive urine
- The urine that is excreted, makeup is very different from primary urine
57
Glomerular filtration rate (GFR) (3)
| What + full blood volume + does not affect
- Rate of production of primary urine (fluid from blood to nephron) (120mL/min)
- Full blood volume filtered every 30 minutes (5L of blood in humans)
- GFR cannot change the concentration of definitive urine. Only nephrons do this.
58
What affects GFR?
- Amount the kidney is filtering is relatively constant, and GFR can fluntuate slightly. BP is the main driver (cardiac contraction). Increase BP will increase GFR and decrease BP will decrease GFR.
59
Chronic hypertension/diabetes mellitus
We initially get increase in GFR but you can actually damage the basement membrane that makes the ultrafilter leading to decrease in GFR thats produced.
60
Loops of Henle (2)
| Function + Max urine concentration correlates with
- Renal component that allows for concentration of urine
- Max urine concentration (U/P ratio) correlates with abundance of long loops of Henle
61
Long loop nephron vs short loop nephrons
- Long loop nephron are loop of Henley that stretch to inner renal medulla
- Short loop nephrons dont contribute to the ability to change definitive urine.
62
Renal Medullary Thickness
Increased loop of henley that stretch farther into renal medulla means increased ability to concentrate urine.
| Longer LOH = more ability to concentrate
63
# Loop of Henle
Descending thin segments
- Highly permeable to water, moderately permeable to most solutes
64
# Loop of Henle
Ascending thin segment
Impermeable to water, moderately permeable to most solutes (solutes that are passing through either into the nephron or out of the nephron in thin portion)
65
Ascending thick segment
Impermeable to water, active transport of sodium chloride (through the cell in the wall of thick ascending limb) to the intersitutium outsid ethe nephron.
66
Explain how active transport works in the thick ascending limb:
- NKCC co-transporter (apical) uses DF for Na+ to cycle and bring 1 Na+ and 1K+ and 2 Cl- ion from inside the nephron lumen to the nephron cell wall. Cl- adds negativity to the cell and Na/K+ on the basolateral membrane will pull Na+ out of the cell and K+ in. K+ wil however leak out of leak chanels and this will create a negative potential on the inside of the cell. Evebtually Cl- will move out to the interstitium.
67
Explain how the single effect works:
- Active transport moves Na+/Cl- out of ascending limb to interstitium. This causes concentration in interstitium to go up and Na+/Cl- will move down the concentration gradient from interstitium to the descending limb. H2O from descending limb will move to interstitium because descending limb is permeable to H2O and increase concentration in solute in interstitium than the descending limb draws free H2O.
68
In single effect, the initial change in pressure occurs because of -------. This creates a ----- osmotic pressure gradient relative to the loop of Henle meaning there will be areas of high osmotic pressure and areas of low across this orientation.
- active transport (Na+/K+ pump)
- transverse (horizontal)
69
Countercurrent multiplication is when osmotic pressure differences are multipled due to -------- and there is ------ osmotic pressure gradient relative to the loop of Henle.
- fluids moving in opposite directions
- an axial (vertical/parallel)
70
Countercurrent multiplication
osmotic pressure differences are multiplied due to fluids moving in opposite directions - creates axial osmotic gradient
71
The three segments of the loops of Henle have different characteristics that enable countercurrent multiplication:
1. The thin descending limb is passively permeable to both water and small solutes such as sodium chloride and urea. As active reabsorption of solutes from the ascending limb of the loop of Henle increases the concentration of solutes within the interstitial space (space between cells), water and solutes move down their concentration gradients until their concentrations within the descending tubule and the interstitial space have equilibrated. As such, water moves out of the tubular fluid and solutes to move in. This means, the tubular fluid becomes steadily more concentrated or hyperosmotic (compared to blood) as it travels down the thin descending limb of the tubule.
2. The thin ascending limb is passively permeable to small solutes, but impermeable to water, which means water cannot escape from this part of the loop. As a result, solutes move out of the tubular fluid, but water is retained and the tubular fluid becomes steadily more dilute or hyposmotic as it moves up the ascending limb of the tubule.
3. The thick ascending limb actively reabsorbs sodium, potassium and chloride. This segment is also impermeable to water, which again means that water cannot escape from this part of the loop. This segment is sometimes called the “diluting segment”.
72
Explain how countercurrent multiplication works:
Countercurrent multiplication moves sodium chloride from the tubular fluid into the interstitial space deep within the kidneys. Although in reality it is a continual process, the way the countercurrent multiplication process builds up an osmotic gradient in the interstitial fluid can be thought of in two steps:
- The single effect. The single effect is driven by active transport of sodium chloride out of the tubular fluid in the thick ascending limb into the interstitial fluid, which becomes hyperosmotic. As a result, water moves passively down its concentration gradient out of the tubular fluid in the descending limb into the interstitial space, until it reaches equilibrium.
- Fluid flow. As urine is continually being produced, new tubular fluid enters the descending limb, which pushes the fluid at higher osmolarity down the tube and an osmotic gradient begins to develop.
As the fluid continues to move through the loop of Henle, these two steps are repeated over and over, causing the osmotic gradient to steadily multiply until it reaches a steady state. The length of the loop of Henle determines the size of the gradient - the longer the loop, the greater the osmotic gradient.
73
As we go into the deepest part of the inner medulla we get the ---- concentrations.
Highest
74
We always have active transport out of the ----- so the osmotic pressure in this point of the nephron is actually ------ than it is when it entered BC.
- ascending limb
- less concentrated
75
A bunch of ------ converge to become the ureter which drains to bladder.
Collecting ducts
76
Antidiuresis (2)
| What occurs + when
- Kidney producing concentrated urine by increasing the permeability of the collecting duct. As the fluid travels down the collecting duct it encounters more and more concentrated interstition and H2O leaks out due to osmosis. Solutes stay in the duct.
- During times of drought.
77
Diuresis
- The kidney produces dilute urine and excrete excess water. Results from decreased permeability of collecting duct to water (water cannot be reabsorbed) but urea continues moving out of collecting duct into interstitial
78
Antidiuretic hormone (ADH) (5)
| AKA+ produced + release stimulation + Detected by + function
- aka arginine vasopressin, vasopressin
- Produced in hypothalamus and released from posterior pituitary
- Release is stimulated by low levels of blood plasma and increase in blood osmolality
- Detected by baroreceptors and osmoreceptors
- Modulates permeability of collecting ducts to water by insertion/deletion of an aquaporin
79
Baroreceptors (2)
| what + locations
- Detect blood volume
- Located in pulmonary venous system, cardiac atria, aortic arch, and carotid sinus
80
Osmoreceptors (3)
| What + location+ mechanism of action
- Detect changes in osmolarity
- Located in hypothalamus
- Cell will shrink or swell and that changes the amount of ADH. Shrinkage of the osmoreceptor cells causes them to fire action potentials to stimulate the release of ADH
81
What does more ADH mean?
Water needs to be conserved (less urine)
82
ADH control of Aquaporin2 (AQP2) density:
ADH increases aquaporin and taking ADH out will decrease aquaporin.
Pre-ADH there is a slow amount of H2O passing through the CD wall. When we give ADH the permeability increases because more H2O channel in place.
83
Explain how Aquaprin 2 (AQP2) is upregulated (4):
AQWCV = aquaporin water channel containing vesicle
1. There are vasopressin receptors in the cell wall that binds vasopressin/ADH when it is present.
2. This will activate G-protein coupled 2nd messenger cascade which activates adenylyl cyclase which increases cAMP and PKA
3. AQWCV will be trafficked and move to the walls of the apical membrane of collecting duct to insert aquaporin via exocytosis of AQWCV.
4. Increase fluid movement out of collecting duct to produce concentrated urine
84
Urea (2)
| Produced by + BC
- Produced by oxidation of amino acids not used in protein synthesis and as a byproduct of nitrogenous metabolism (which produces ammonia but is then converted to urea because amonia critically raise cellular PH)
- Freely passes into the capusular fluid in BC (amount in blood = amount in BC as primary urine)
85
What are areas with low permeability to urea (3)?
- Distal convoluted tubule
- Thick ascending segment of Loop of Henle
- Cortical and outer renal medulla
86
What are areas with high permeability to urea?
Collecting duct and the inner renal medulla, contains UT-A1
87
Urea transporter protein UT-A1 (3)
| What + controled under + mechanis of action
- Facilitates diffusion from collecting duct into interstitial fluid
- Under hormonal control: up-regulated by ADH
- Increase concentration of urine to conserve H2O. This will causes greater concentration of urea in interstitium which means more of it is loaded up in the ascending/descending lumbs of LOH so we get even greater concentration as it leaves the CD. We will conserve water.
88
Vasa recta (2)
| What + how it minimizes distrupting osmotic gradient
- Vasculature that supplies the renal medulla, goes from cortex down into medulla and back up to cortex.
- Does not destroy osmotic pressure gradients in kidney because:
1. There it is very little blood flow (only 1-2% to total renal blood flow, 98% is to the glomerolus)
2. Acts as a countercurrent exchanger (minimizes washout of solutes). As blood descends into the medulla, it loses water and gains solutes due to the hypertonic interstitial environment. As blood ascends back toward the cortex, it reabsorbs water and loses solutes. This passive exchange helps prevent the dissipation of the medullary osmotic gradient, which is necessary for water reabsorption in the collecting ducts.
89
So in fresh water there's going to be ----- of water. Osmosis is favoring water moving ------ because the osmotic pressure inside the organism is ------ than it is in the surrounding environment. So free water is going to move ------.
There's going to be ----- of ions. Again, there's a ------ concentration of ions inside the organism than there is outside the organism. So those ions are going to want to move --------
- an influx
- into the organism
- higher
- into the into the organism
- a loss
- higher
- down their concentration gradient and leave the organism into the environment
90
In salt water. It's the exact opposite. Animals are going to be constantly ---- water, because again, more free water in the ------. So it's going to move towards the -----. And you're going to get an ------ of ions because the ions ----------
- losing
- organism than there is in the environment
- environment
- influx
- in the environment are going to move down their own concentration gradient and load up inside the organism.
91
Explain drinking seawater between us and other marine animals:
If we drink salt water, it draws water from our body into our gut. We need to reverse that we want a net gain of water. So what we have to do is we have to move the ions so the water can follow so we can get water from the gut. 1st thing that we do is we pump, pump a bunch of the sodium and chloride from inside the gut out into the body. This is why we can't drink sea water is because we are not good at getting sodium and chloride from inside the gut out into the body. So if we drink seawater, it actually dehydrates us because a bunch of water from our body leaves and goes into the gut, and then eventually, we just we just excrete it right. But marine organisms that are drinking a lot of salt water have the ability to move large amounts of sodium and chloride from inside the gut into the blood plasma. This is going to be active transport.
92
Orgins of life
- Began in a SW environment
- As organisms began to move, they encountered different environments
