Salt and Water Balance and Nitrogen Excretion 40.
-
Upload
geoffrey-henry-logan -
Category
Documents
-
view
221 -
download
0
Transcript of Salt and Water Balance and Nitrogen Excretion 40.
![Page 1: Salt and Water Balance and Nitrogen Excretion 40.](https://reader031.fdocuments.net/reader031/viewer/2022032309/56649d0b5503460f949dde63/html5/thumbnails/1.jpg)
Salt and Water Balance and Nitrogen Excretion
40
![Page 2: Salt and Water Balance and Nitrogen Excretion 40.](https://reader031.fdocuments.net/reader031/viewer/2022032309/56649d0b5503460f949dde63/html5/thumbnails/2.jpg)
Chapter 40 Salt and Water Balance and Nitrogen Excretion
Key Concepts
• 40.1 Excretory Systems Maintain Homeostasis of the Extracellular Fluid
• 40.2 Excretory Systems Eliminate Nitrogenous Wastes
• 40.3 Excretory Systems Produce Urine by Filtration, Reabsorption, and Secretion
![Page 3: Salt and Water Balance and Nitrogen Excretion 40.](https://reader031.fdocuments.net/reader031/viewer/2022032309/56649d0b5503460f949dde63/html5/thumbnails/3.jpg)
Chapter 40 Salt and Water Balance and Nitrogen Excretion
Key Concepts
• 40.4 The Mammalian Kidney Produces Concentrated Urine
• 40.5 The Kidney Is Regulated to Maintain Blood Pressure, Blood Volume, and Blood Composition
![Page 4: Salt and Water Balance and Nitrogen Excretion 40.](https://reader031.fdocuments.net/reader031/viewer/2022032309/56649d0b5503460f949dde63/html5/thumbnails/4.jpg)
Chapter 40 Opening Question
How do excretory systems of animals maintain homeostasis of the interstitial fluid in the face of extreme challenges?
![Page 5: Salt and Water Balance and Nitrogen Excretion 40.](https://reader031.fdocuments.net/reader031/viewer/2022032309/56649d0b5503460f949dde63/html5/thumbnails/5.jpg)
Concept 40.1 Excretory Systems Maintain Homeostasis of the Extracellular Fluid
Excretory systems control volume, concentration, and composition of the extracellular fluid and excrete wastes.
Four excretory functions:
• Regulate fluid volume in the body
• Regulate solute concentrations, or osmolarity, of extracellular fluid
• Maintain individual solutes
• Eliminate nitrogenous wastes
Urine is the liquid waste product.
![Page 6: Salt and Water Balance and Nitrogen Excretion 40.](https://reader031.fdocuments.net/reader031/viewer/2022032309/56649d0b5503460f949dde63/html5/thumbnails/6.jpg)
Concept 40.1 Excretory Systems Maintain Homeostasis of the Extracellular Fluid
The osmolarity of a solution is the number of osmoles of active solutes per liter of solvent.
The osmolarity of the extracellular fluid must be maintained for cellular water balance.
If the osmolarity of the extracellular fluid is different than the cytoplasm, water will move into or out of the cells via osmosis, and cells may be damaged.
![Page 7: Salt and Water Balance and Nitrogen Excretion 40.](https://reader031.fdocuments.net/reader031/viewer/2022032309/56649d0b5503460f949dde63/html5/thumbnails/7.jpg)
Concept 40.1 Excretory Systems Maintain Homeostasis of the Extracellular Fluid
Animals in different environments face different osmolarity problems.
On land, salt and water must be conserved.
Terrestrial animals are osmoregulators and actively regulate the osmolarity of their extracellular fluid.
Freshwater animals have to conserve salts but excrete excess water, so are also osmoregulators.
![Page 8: Salt and Water Balance and Nitrogen Excretion 40.](https://reader031.fdocuments.net/reader031/viewer/2022032309/56649d0b5503460f949dde63/html5/thumbnails/8.jpg)
Concept 40.1 Excretory Systems Maintain Homeostasis of the Extracellular Fluid
Marine animals are exposed to the high osmolarity of the ocean:
Osmoconformers equilibrate their osmolarity with seawater.
Artemia (brine shrimp) can survive in varied environmental osmolarities:
• In high osmolarity, Cl– is actively transported out through the gills, Na+ ions follow.
• In low osmolarity, the transport of Cl– is reversed.
![Page 9: Salt and Water Balance and Nitrogen Excretion 40.](https://reader031.fdocuments.net/reader031/viewer/2022032309/56649d0b5503460f949dde63/html5/thumbnails/9.jpg)
Figure 40.1 Osmoconformity Has Limits
![Page 10: Salt and Water Balance and Nitrogen Excretion 40.](https://reader031.fdocuments.net/reader031/viewer/2022032309/56649d0b5503460f949dde63/html5/thumbnails/10.jpg)
Concept 40.1 Excretory Systems Maintain Homeostasis of the Extracellular Fluid
Most animals are ionic regulators, conserving some ions and excreting others to maintain ionic composition of extracellular fluid.
Ionic conformers allow their ionic composition, as well as their osmolarity, to match the environment.
Commonly regulated ions are Na+, Cl–, K+, Ca2+, H+, and HCO3
– (bicarbonate).
![Page 11: Salt and Water Balance and Nitrogen Excretion 40.](https://reader031.fdocuments.net/reader031/viewer/2022032309/56649d0b5503460f949dde63/html5/thumbnails/11.jpg)
Concept 40.1 Excretory Systems Maintain Homeostasis of the Extracellular Fluid
H+ concentration, or pH, is closely regulated—important to protein structure and function.
A buffer is a substance that can absorb or release hydrogen ions.
The major buffer in blood is bicarbonate (HCO3
–), which is formed from CO2.
Lungs eliminate CO2 from blood, and kidneys reabsorb HCO3
– and excrete H+ to maintain pH.
![Page 12: Salt and Water Balance and Nitrogen Excretion 40.](https://reader031.fdocuments.net/reader031/viewer/2022032309/56649d0b5503460f949dde63/html5/thumbnails/12.jpg)
Concept 40.2 Excretory Systems Eliminate Nitrogenous Wastes
Animals must eliminate metabolic waste products:
• Carbohydrates and fat end up as water and CO2 and are easily excreted
• Proteins and nucleic acids contain nitrogen, so metabolism produces nitrogenous waste
Ammonia (NH3) is the most common nitrogenous waste.
![Page 13: Salt and Water Balance and Nitrogen Excretion 40.](https://reader031.fdocuments.net/reader031/viewer/2022032309/56649d0b5503460f949dde63/html5/thumbnails/13.jpg)
Concept 40.2 Excretory Systems Eliminate Nitrogenous Wastes
Ammonia is soluble in water—aquatic animals who secrete NH3 through gills are ammonotelic.
Animals must convert NH3 to urea or uric acid.
Ureotelic animals mostly excrete urea. It is water-soluble but results in large water loss.
Uricotelic animals mostly excrete uric acid. It is insoluble in water and precipitates out of the urine with little water loss.
![Page 14: Salt and Water Balance and Nitrogen Excretion 40.](https://reader031.fdocuments.net/reader031/viewer/2022032309/56649d0b5503460f949dde63/html5/thumbnails/14.jpg)
Figure 40.2 Waste Products of Metabolism
![Page 15: Salt and Water Balance and Nitrogen Excretion 40.](https://reader031.fdocuments.net/reader031/viewer/2022032309/56649d0b5503460f949dde63/html5/thumbnails/15.jpg)
Concept 40.2 Excretory Systems Eliminate Nitrogenous Wastes
Most species secrete more than one nitrogenous waste.
Humans are ureotelic but also excrete:
• Uric acid—from metabolism of nucleic acids and caffeine
• Ammonia—regulates pH of extracellular fluid by buffering urine
![Page 16: Salt and Water Balance and Nitrogen Excretion 40.](https://reader031.fdocuments.net/reader031/viewer/2022032309/56649d0b5503460f949dde63/html5/thumbnails/16.jpg)
Concept 40.3 Excretory Systems Produce Urine by Filtration, Reabsorption, and Secretion
In most systems urine is produced by filtering extracellular fluid.
The resulting fluid is a filtrate—similar to blood plasma.
Filtrate flows through tubules and is modified by reabsorption or secretion of solutes.
The modified filtrate is excreted as urine.
![Page 17: Salt and Water Balance and Nitrogen Excretion 40.](https://reader031.fdocuments.net/reader031/viewer/2022032309/56649d0b5503460f949dde63/html5/thumbnails/17.jpg)
Concept 40.3 Excretory Systems Produce Urine by Filtration, Reabsorption, and Secretion
Annelids have segmented bodies, with a coelom in each segment.
In earthworms, blood pumped under pressure causes blood to filter across capillary walls.
Water, small molecules, and some waste products enter the coelom.
![Page 18: Salt and Water Balance and Nitrogen Excretion 40.](https://reader031.fdocuments.net/reader031/viewer/2022032309/56649d0b5503460f949dde63/html5/thumbnails/18.jpg)
Concept 40.3 Excretory Systems Produce Urine by Filtration, Reabsorption, and Secretion
Each earthworm segment contains a pair of metanephridia.
A metanephridium begins as a nephrostome, or opening, which leads into a tubule.
The tubule ends in a nephridiopore.
Fluid enters through the nephrostomes, and tubule cells reabsorb or secrete molecules into it.
![Page 19: Salt and Water Balance and Nitrogen Excretion 40.](https://reader031.fdocuments.net/reader031/viewer/2022032309/56649d0b5503460f949dde63/html5/thumbnails/19.jpg)
Figure 40.3 Metanephridia in Earthworms
![Page 20: Salt and Water Balance and Nitrogen Excretion 40.](https://reader031.fdocuments.net/reader031/viewer/2022032309/56649d0b5503460f949dde63/html5/thumbnails/20.jpg)
Concept 40.3 Excretory Systems Produce Urine by Filtration, Reabsorption, and Secretion
The insect excretory system consists of Malpighian tubules—blind-ended tubules that open into the gut.
Tubule cells actively transport uric acid, K+, and Na+ into the tubules.
Water follows the solutes and moves contents toward the gut.
Water and ions are recovered in the hindgut, and uric acid and other waste are excreted.
![Page 21: Salt and Water Balance and Nitrogen Excretion 40.](https://reader031.fdocuments.net/reader031/viewer/2022032309/56649d0b5503460f949dde63/html5/thumbnails/21.jpg)
Figure 40.4 Malpighian Tubules in Insects (Part 1)
![Page 22: Salt and Water Balance and Nitrogen Excretion 40.](https://reader031.fdocuments.net/reader031/viewer/2022032309/56649d0b5503460f949dde63/html5/thumbnails/22.jpg)
Figure 40.4 Malpighian Tubules in Insects (Part 2)
![Page 23: Salt and Water Balance and Nitrogen Excretion 40.](https://reader031.fdocuments.net/reader031/viewer/2022032309/56649d0b5503460f949dde63/html5/thumbnails/23.jpg)
Concept 40.3 Excretory Systems Produce Urine by Filtration, Reabsorption, and Secretion
Vertebrates are well-adapted to excrete excess water.
Kidney—the main excretory organ
Nephron—the main functional unit of the kidney, consisting of a renal tubule and the surrounding blood vessels
Nephrons filter large volumes of blood and achieve bulk reabsorption.
![Page 24: Salt and Water Balance and Nitrogen Excretion 40.](https://reader031.fdocuments.net/reader031/viewer/2022032309/56649d0b5503460f949dde63/html5/thumbnails/24.jpg)
Figure 40.5 The Vertebrate Nephron
![Page 25: Salt and Water Balance and Nitrogen Excretion 40.](https://reader031.fdocuments.net/reader031/viewer/2022032309/56649d0b5503460f949dde63/html5/thumbnails/25.jpg)
Concept 40.3 Excretory Systems Produce Urine by Filtration, Reabsorption, and Secretion
A nephron begins with Bowman’s capsule, which encloses the glomerulus.
Blood enters through the afferent arteriole and leaves through the efferent arteriole.
The glomerulus is highly permeable to water, ions, and small molecules, but impermeable to cells and large molecules.
![Page 26: Salt and Water Balance and Nitrogen Excretion 40.](https://reader031.fdocuments.net/reader031/viewer/2022032309/56649d0b5503460f949dde63/html5/thumbnails/26.jpg)
Figure 40.6 A Tour of the Nephron (Part 1)
![Page 27: Salt and Water Balance and Nitrogen Excretion 40.](https://reader031.fdocuments.net/reader031/viewer/2022032309/56649d0b5503460f949dde63/html5/thumbnails/27.jpg)
Figure 40.6 A Tour of the Nephron (Part 2)
![Page 28: Salt and Water Balance and Nitrogen Excretion 40.](https://reader031.fdocuments.net/reader031/viewer/2022032309/56649d0b5503460f949dde63/html5/thumbnails/28.jpg)
Concept 40.3 Excretory Systems Produce Urine by Filtration, Reabsorption, and Secretion
Filtration occurs when blood pressure drives water and solutes through fenestrations in glomerular capillaries.
Filtration slits in Bowman’s capsule are formed by podocytes—specialized cells with projections that wrap around capillaries.
Glomerular filtration rate is the rate of the filtered fluid entering the capsule.
![Page 29: Salt and Water Balance and Nitrogen Excretion 40.](https://reader031.fdocuments.net/reader031/viewer/2022032309/56649d0b5503460f949dde63/html5/thumbnails/29.jpg)
Concept 40.3 Excretory Systems Produce Urine by Filtration, Reabsorption, and Secretion
The filtrate entering the capsule is similar to blood plasma—its composition is adjusted as it passes along the renal tubule
Peritubular capillaries transport substances to and from the renal tubules.
![Page 30: Salt and Water Balance and Nitrogen Excretion 40.](https://reader031.fdocuments.net/reader031/viewer/2022032309/56649d0b5503460f949dde63/html5/thumbnails/30.jpg)
Concept 40.3 Excretory Systems Produce Urine by Filtration, Reabsorption, and Secretion
Marine bony fishes must conserve water in their high osmolarity environment.
They minimize water loss by producing very little urine.
Some ions are not absorbed in their gut—NaCl is excreted through the gills.
![Page 31: Salt and Water Balance and Nitrogen Excretion 40.](https://reader031.fdocuments.net/reader031/viewer/2022032309/56649d0b5503460f949dde63/html5/thumbnails/31.jpg)
Concept 40.3 Excretory Systems Produce Urine by Filtration, Reabsorption, and Secretion
Cartilaginous fishes convert nitrogenous wastes to compounds and retain large amounts in the extracellular fluid.
The fluid is similar in osmolarity to seawater so water is not lost by osmosis to the environment.
![Page 32: Salt and Water Balance and Nitrogen Excretion 40.](https://reader031.fdocuments.net/reader031/viewer/2022032309/56649d0b5503460f949dde63/html5/thumbnails/32.jpg)
Concept 40.3 Excretory Systems Produce Urine by Filtration, Reabsorption, and Secretion
Amphibians in dry environments reduce permeability of their skin to water.
Estivation is a state of low metabolic activity and low water turnover.
Some frogs fill a large bladder with dilute urine before estivation and gradually reabsorb it into the blood.
![Page 33: Salt and Water Balance and Nitrogen Excretion 40.](https://reader031.fdocuments.net/reader031/viewer/2022032309/56649d0b5503460f949dde63/html5/thumbnails/33.jpg)
Concept 40.3 Excretory Systems Produce Urine by Filtration, Reabsorption, and Secretion
Reptiles are amniotes and have three major adaptations that allow them to exist outside of water:
• Amniotic reproduction, shelled eggs
• Scaled epidermis that retards water loss
• Excretion of nitrogenous wastes as uric acid, with little water loss
![Page 34: Salt and Water Balance and Nitrogen Excretion 40.](https://reader031.fdocuments.net/reader031/viewer/2022032309/56649d0b5503460f949dde63/html5/thumbnails/34.jpg)
Concept 40.3 Excretory Systems Produce Urine by Filtration, Reabsorption, and Secretion
Mammals also have adapted to conserve water:
• Skin covering to reduce water loss
• Amniotic reproduction
• Evolution of a kidney to produce concentrated urine
![Page 35: Salt and Water Balance and Nitrogen Excretion 40.](https://reader031.fdocuments.net/reader031/viewer/2022032309/56649d0b5503460f949dde63/html5/thumbnails/35.jpg)
Concept 40.4 The Mammalian Kidney Produces Concentrated Urine
Mammals have kidneys that filter blood and produce urine.
In each nephron, there is a specialized feature: the loop of Henle.
Ion transport in this region creates an area of high osmolarity, so that water is able to be reabsorbed from the urine.
This concentrates the urine and reduces water loss.
![Page 36: Salt and Water Balance and Nitrogen Excretion 40.](https://reader031.fdocuments.net/reader031/viewer/2022032309/56649d0b5503460f949dde63/html5/thumbnails/36.jpg)
Concept 40.4 The Mammalian Kidney Produces Concentrated Urine
Ureter—a duct from the kidney that leads to the urinary bladder
Urethra—a tube for urine excretion leading from the urinary bladder, where urine is stored, to the outside of the body
The ureter, renal artery, and renal vein enter the kidney on the concave side.
![Page 37: Salt and Water Balance and Nitrogen Excretion 40.](https://reader031.fdocuments.net/reader031/viewer/2022032309/56649d0b5503460f949dde63/html5/thumbnails/37.jpg)
Figure 40.7 The Human Excretory System (Part 1)
![Page 38: Salt and Water Balance and Nitrogen Excretion 40.](https://reader031.fdocuments.net/reader031/viewer/2022032309/56649d0b5503460f949dde63/html5/thumbnails/38.jpg)
Figure 40.7 The Human Excretory System (Part 2)
![Page 39: Salt and Water Balance and Nitrogen Excretion 40.](https://reader031.fdocuments.net/reader031/viewer/2022032309/56649d0b5503460f949dde63/html5/thumbnails/39.jpg)
Concept 40.4 The Mammalian Kidney Produces Concentrated Urine
Kidneys have an outer cortex that covers the inner medulla.
The glomeruli and Bowman’s capsules are in the cortex.
Proximal convoluted tubules—the initial, twisted segments of the renal tubules, located in the cortex
![Page 40: Salt and Water Balance and Nitrogen Excretion 40.](https://reader031.fdocuments.net/reader031/viewer/2022032309/56649d0b5503460f949dde63/html5/thumbnails/40.jpg)
Figure 40.7 The Human Excretory System (Part 3)
![Page 41: Salt and Water Balance and Nitrogen Excretion 40.](https://reader031.fdocuments.net/reader031/viewer/2022032309/56649d0b5503460f949dde63/html5/thumbnails/41.jpg)
Concept 40.4 The Mammalian Kidney Produces Concentrated Urine
The renal tubule descends into the medulla and forms the loop of Henle, which is important for urine concentration.
After forming the loop, the tubule returns to the cortex.
The loop of Henle leads to the distal convoluted tubule.
The distal convoluted tubules join the collecting duct in the cortex.
Collecting ducts empty into the pelvis, which drains into the ureter.
![Page 42: Salt and Water Balance and Nitrogen Excretion 40.](https://reader031.fdocuments.net/reader031/viewer/2022032309/56649d0b5503460f949dde63/html5/thumbnails/42.jpg)
Concept 40.4 The Mammalian Kidney Produces Concentrated Urine
The vasa recta is a network of peritubular capillaries parallel to the loops of Henle and the collecting duct.
Blood plasma that does not enter Bowman’s capsule goes via the efferent artery to the peritubular capillaries.
These play an important role in secretion and reabsorption and in maintaining the high-osmolarity region.
![Page 43: Salt and Water Balance and Nitrogen Excretion 40.](https://reader031.fdocuments.net/reader031/viewer/2022032309/56649d0b5503460f949dde63/html5/thumbnails/43.jpg)
Concept 40.4 The Mammalian Kidney Produces Concentrated Urine
The proximal convoluted tubule (PCT) is responsible for the reabsorption of water and solutes—osmolarity does not change.
PCT cells actively transport Na+, glucose, and amino acids.
Water follows the transport of solutes.
Next steps in urine processing:
• Reabsorb salts, leaving urea
• Set up conditions for hypertonic urine production
![Page 44: Salt and Water Balance and Nitrogen Excretion 40.](https://reader031.fdocuments.net/reader031/viewer/2022032309/56649d0b5503460f949dde63/html5/thumbnails/44.jpg)
Concept 40.4 The Mammalian Kidney Produces Concentrated Urine
Concentration of urine is due to a countercurrent multiplier mechanism in the loops of Henle.
Tubule fluid flows in opposite directions in the two limbs of a loop of Henle.
The loops increase osmolarity of extracellular fluid in a graduated way.
![Page 45: Salt and Water Balance and Nitrogen Excretion 40.](https://reader031.fdocuments.net/reader031/viewer/2022032309/56649d0b5503460f949dde63/html5/thumbnails/45.jpg)
Figure 40.8 Concentrating the Urine
![Page 46: Salt and Water Balance and Nitrogen Excretion 40.](https://reader031.fdocuments.net/reader031/viewer/2022032309/56649d0b5503460f949dde63/html5/thumbnails/46.jpg)
Concept 40.4 The Mammalian Kidney Produces Concentrated Urine
Loop of Henle segments:
• Thick ascending limb—actively transports Na+ (Cl– follows) and raises its concentration in the interstitial fluid
• Thin descending limb—loses water to the neighboring interstitial fluid with high Na+ and Cl– concentration
![Page 47: Salt and Water Balance and Nitrogen Excretion 40.](https://reader031.fdocuments.net/reader031/viewer/2022032309/56649d0b5503460f949dde63/html5/thumbnails/47.jpg)
Concept 40.4 The Mammalian Kidney Produces Concentrated Urine
• Thin ascending limb—receives concentrated fluid from descending limb and allows diffusion of Na+ and Cl– into the interstitial fluid
Fluid reaching the distal collecting duct is less concentrated—solutes in the medulla create a concentration gradient.
![Page 48: Salt and Water Balance and Nitrogen Excretion 40.](https://reader031.fdocuments.net/reader031/viewer/2022032309/56649d0b5503460f949dde63/html5/thumbnails/48.jpg)
Concept 40.4 The Mammalian Kidney Produces Concentrated Urine
The concentration gradient is preserved by the vasa recta.
Blood flowing down the descending limb loses water and gains solutes.
Concentrated blood flowing up the ascending limb gains water and loses solutes—water is thus returned to the bloodstream.
![Page 49: Salt and Water Balance and Nitrogen Excretion 40.](https://reader031.fdocuments.net/reader031/viewer/2022032309/56649d0b5503460f949dde63/html5/thumbnails/49.jpg)
Concept 40.4 The Mammalian Kidney Produces Concentrated Urine
Water reabsorption and fine-tuning of ionic composition begins in the distal convoluted tubule.
Fluid that leaves the tubule and flows into the collecting duct as urine has different solute composition than blood plasma.
![Page 50: Salt and Water Balance and Nitrogen Excretion 40.](https://reader031.fdocuments.net/reader031/viewer/2022032309/56649d0b5503460f949dde63/html5/thumbnails/50.jpg)
Concept 40.4 The Mammalian Kidney Produces Concentrated Urine
In collecting duct the major solute in tubular fluid is urea.
Fluid flows down collecting duct and loses water to interstitial fluid because of concentration gradient established by loops of Henle.
Some urea also diffuses and adds to osmotic force—recycling this urea contributes to urine concentration.
![Page 51: Salt and Water Balance and Nitrogen Excretion 40.](https://reader031.fdocuments.net/reader031/viewer/2022032309/56649d0b5503460f949dde63/html5/thumbnails/51.jpg)
Concept 40.4 The Mammalian Kidney Produces Concentrated Urine
Renal failure results in:
• Salt and water retention (high blood pressure)
• Urea retention (uremic poisoning)
• Decreasing pH (acidosis)
Dialysis treatment passes blood through membrane channels bathed in a plasma-like solution to remove wastes.
![Page 52: Salt and Water Balance and Nitrogen Excretion 40.](https://reader031.fdocuments.net/reader031/viewer/2022032309/56649d0b5503460f949dde63/html5/thumbnails/52.jpg)
Concept 40.5 The Kidney Is Regulated to Maintain Blood Pressure, Blood Volume, and Blood Composition
A constant glomerular filtration rate (GFR) requires blood supplied to the kidneys under adequate pressure.
Autoregulatory mechanisms ensure blood supply and blood pressure.
Hormones released by other organs also help regulate the kidneys.
![Page 53: Salt and Water Balance and Nitrogen Excretion 40.](https://reader031.fdocuments.net/reader031/viewer/2022032309/56649d0b5503460f949dde63/html5/thumbnails/53.jpg)
Concept 40.5 The Kidney Is Regulated to Maintain Blood Pressure, Blood Volume, and Blood Composition
If GFR begins to fall, the first autoregulatory response is dilation of afferent renal arterioles—increases glomerular blood pressure.
Kidney releases renin if GFR still falls, this activates angiotensin.
![Page 54: Salt and Water Balance and Nitrogen Excretion 40.](https://reader031.fdocuments.net/reader031/viewer/2022032309/56649d0b5503460f949dde63/html5/thumbnails/54.jpg)
Concept 40.5 The Kidney Is Regulated to Maintain Blood Pressure, Blood Volume, and Blood Composition
Angiotensin:
• Constricts efferent renal arterioles
• Constricts peripheral blood vessels to raise blood pressure in the body
• Stimulates release of aldosterone to increase Na+ uptake
• Stimulates thirst to increase water ingestion to raise blood volume and pressure
![Page 55: Salt and Water Balance and Nitrogen Excretion 40.](https://reader031.fdocuments.net/reader031/viewer/2022032309/56649d0b5503460f949dde63/html5/thumbnails/55.jpg)
Figure 40.9 Renin-Angiotensin-Aldosterone System Helps Regulate GFR
![Page 56: Salt and Water Balance and Nitrogen Excretion 40.](https://reader031.fdocuments.net/reader031/viewer/2022032309/56649d0b5503460f949dde63/html5/thumbnails/56.jpg)
Concept 40.5 The Kidney Is Regulated to Maintain Blood Pressure, Blood Volume, and Blood Composition
The hypothalamus can stimulate release of antidiuretic hormone (ADH, also called vasopressin).
ADH increases the permeability of membranes to water.
Osmoreceptors that detect a rise in blood osmolarity will stimulate ADH release.
![Page 57: Salt and Water Balance and Nitrogen Excretion 40.](https://reader031.fdocuments.net/reader031/viewer/2022032309/56649d0b5503460f949dde63/html5/thumbnails/57.jpg)
Concept 40.5 The Kidney Is Regulated to Maintain Blood Pressure, Blood Volume, and Blood Composition
ADH causes aquaporins, or water channels, to be inserted in the membranes of cells in the collecting duct.
More water is reabsorbed and urine is more concentrated.
Alcohol inhibits release of ADH—excessive alcohol intake can cause substantial dehydration.
![Page 58: Salt and Water Balance and Nitrogen Excretion 40.](https://reader031.fdocuments.net/reader031/viewer/2022032309/56649d0b5503460f949dde63/html5/thumbnails/58.jpg)
Concept 40.5 The Kidney Is Regulated to Maintain Blood Pressure, Blood Volume, and Blood Composition
Atrial muscle fibers release atrial natriuretic peptide (ANP) when blood volume in the atria increases
ANP decreases the reabsorption of Na+ in the kidney.
Increased loss of Na+ and water decreases blood volume and pressure.
![Page 59: Salt and Water Balance and Nitrogen Excretion 40.](https://reader031.fdocuments.net/reader031/viewer/2022032309/56649d0b5503460f949dde63/html5/thumbnails/59.jpg)
Figure 40.10 ADH Induces Insertion of Aquaporins into Plasma Membranes (Part 1)
![Page 60: Salt and Water Balance and Nitrogen Excretion 40.](https://reader031.fdocuments.net/reader031/viewer/2022032309/56649d0b5503460f949dde63/html5/thumbnails/60.jpg)
Figure 40.10 ADH Induces Insertion of Aquaporins into Plasma Membranes (Part 2)
![Page 61: Salt and Water Balance and Nitrogen Excretion 40.](https://reader031.fdocuments.net/reader031/viewer/2022032309/56649d0b5503460f949dde63/html5/thumbnails/61.jpg)
Answer to Opening Question
Excretory systems include active transport of Na+, often with Cl–.
Ion transport creates osmotic concentration gradients that move water across membranes.
Depending on an animal’s environment, it will direct the absorption or secretion of solutes.
Sea birds ingest salt water and use a salt-secreting organ with special transporters that take up NaCl and secrete it.
![Page 62: Salt and Water Balance and Nitrogen Excretion 40.](https://reader031.fdocuments.net/reader031/viewer/2022032309/56649d0b5503460f949dde63/html5/thumbnails/62.jpg)
Figure 40.11 Salt Excretion in a Marine Bird