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Biology 2312 > Chapter 50 > Flashcards

Chapter 50 Flashcards

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1
Q

Water in a multicellular animal’s body is distributed between

A

the intracellular and extracellular compartments

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2
Q

What kind of cells facilitate the exchange of water and electrolytes between the body and the environment?

A

specialized epithelial cells

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3
Q

What is the major cation in extracellular fluids?

A

Na+

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4
Q

What is the major anion in extracellular fluids?

A

Cl-

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5
Q

What are three other important ions?

A

Ca2+; Mg2+; K+

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6
Q

What is osmosis?

A

diffusion of water across a semipermeable membrane

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7
Q

What is osmotic pressure?

A

measure of a solution’s tendency to take in water by osmosis; is the amount of pressure needed to balance the pressure created by water movement

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8
Q

What is the relationship between the concentration of a solution and its osmolarity?

A

solution with higher concentration exerts more osmotic pressure

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9
Q

What is osmolarity?

A

number of osmotically active moles of solute per liter solution

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10
Q

How does osmolarity differ from molarity?

A

if a substance dissociates in solution, there are multiple osmotically active particles - ex 1 M NaCl is 2 Osm because of Na+ and Cl-

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11
Q

What is the tonicity of a solution?

A

measure of solutions’ ability to change the volume of a cell by osmosis

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12
Q

Give two examples of isotonic solutions used in medical settings.

A

normal saline; 5% dextrose

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13
Q

Normal saline and 5% dextrose are what kind of solution?

A

isotonic solutions

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14
Q

What are normal saline and 5% dextrose used for?

A

used to bathe exposed tissue

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15
Q

Describe the osmolarity of body fluids in marine invertebrates.

A

same as that of seawater (except Mg2+ concentrations aren’t the same)

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16
Q

What is the consequence of marine invertebrate body fluids having the same osmolarity as seawater?

A

no osmotic gradient exists, so therefore no net movement of water

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17
Q

What are osmoconformers?

A

animals that maintains the osmotic concentration of its body fluids at the same level of the medium in which they live

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18
Q

Which vertebrates are strict osmoconformers?

A

primitive hagfish

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19
Q

Are sharks/Chondrichthyes osmoconformers?

A

they are isotonic to seawater even though their blood NaCl level is lower than that of seawater

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20
Q

How do Chondrichthyes make up the difference in NaCl between their blood and the surrounding seawater?

A

made up by retaining urea

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21
Q

What are osmoregulators?

A

animals that maintain relatively constant blood osmolarity in any environment

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22
Q

Which animals are osmoregulators?

A

all other vertebrates other than primitive hagfish

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23
Q

Describe the osmolarity of freshwater vertebrates.

A

hypertonic to environment

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24
Q

What is the consequence of hypertonicity of freshwater vertebrates?

A

water tends to enter their bodies, so they have adapted ways to eliminate excess water

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25
Q

Freshwater vertebrates tend to lose what particles?

A

tend to lose inorganic ions to environment, so they must actively transport these ions back into their bodies

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26
Q

Describe the osmolarity of marine vertebrates.

A

most are hypotonic to environment; body fluids are 1/3 the osmolarity of surrounding water

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27
Q

What is the consequence of the hypotonicity of marine vertebrates?

A

water tends to leave their bodies, so they have adapted ways to retain water

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28
Q

How exactly do marine vertebrates retain water/avoid excessive water loss?

A

they drink seawater and eliminate excess ions through kidneys and gills

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29
Q

Describe the osmolarity of terrestrial vertebrates.

A

hypertonic to environment

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30
Q

What is the consequence of the hypertonicity of terrestrial vertebrates?

A

tend to lose water to air by evaporation from skin and lungs

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31
Q

The catabolism of amino acids and nucleic acids produces

A

nitrogen-containing by-products called nitrogenous waste

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32
Q

What is the immediate by-product of amino acid/nucleic acid catabolism?

A

ammonia

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33
Q

In bony fishes/aquatic vertebrates, ammonia is converted to

A

ammonia isn’t converted into anything, but is eliminated directly

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34
Q

Ammonia is eliminated directly in

A

bony fishes/aquatic vertebrates

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35
Q

In mammals, amphibians, and cartilaginous fish, ammonia is converted to

A

urea

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36
Q

Ammonia is converted to urea in

A

mammals, amphibians, cartilaginous fish

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37
Q

Draw the structure of urea.

A

draw

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38
Q

In reptiles, birds, and insects, ammonia is converted to

A

uric acid

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39
Q

Ammonia is converted to uric acid in

A

reptiles, birds, insects

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40
Q

Draw the structure of uric acid.

A

draw

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41
Q

Why does ammonia have to be quickly removed?

A

because it is toxic

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42
Q

How do bony fishes/aquatic vertebrates eliminate ammonia?

A

eliminate most of it by diffusion through the gills, less through excretion in very dilute urine

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43
Q

Is urea more or less toxic than ammonia?

A

Urea is less toxic than ammonia.

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44
Q

Describe the solubility of urea.

A

urea is soluble in water

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45
Q

What is the consequence of urea being water-soluble?

A

large amounts can be excreted in urine

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46
Q

Where is urea synthesized in mammals?

A

liver

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47
Q

Describe the solubility of uric acid.

A

slightly soluble in water

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48
Q

What is the consequence of the solubility of uric acid?

A

uric acid precipitates

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49
Q

What is guano?

A

pasty white material in bird droppings that is made of uric acid

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50
Q

Describe the energetics of synthesizing uric acid.

A

Costs animal energy to synthesize uric acid, but this is offset by the conservation of water

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51
Q

Why is the insolubility of uric acid important for embryonal development?

A

as a solid precipitate, uric acid is unable to affect the embryo’s development even though it’s still in the egg

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52
Q

(T/F) Mammals do not produce uric acid.

A

False, mammals do produce uric acid.

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53
Q

In what context do mammals produce uric acid?

A

waste product of purine nucleotide degradation (not from amino acids)

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54
Q

How do most mammals deal with uric acid?

A

uricase converts uric acid into allantoin, which is more soluble

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55
Q

Which mammals lack uricase?

A

humans, apes, Dalmatian dog

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56
Q

How do mammals that lack uricase deal with uric acid?

A

directly excrete uric acid

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57
Q

What is gout?

A

excessive accumulation of uric acid in the joints

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58
Q

In animals, the removal of water/salt is coupled to

A

the removal of metabolic wastes through the excretory system

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59
Q

How do single-celled protists get rid of excretory waste?

A

contractile vacuoles

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60
Q

How do sponges get rid of excretory waste?

A

contractile vacuoles

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61
Q

What are the excretory tubules found in flatworms?

A

protonephridia

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62
Q

Where are protonephridia found?

A

flatworms

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63
Q

Protonephridia branch throughout the flatworm’s body into

A

bulblike flame cells

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64
Q

Flatworm flame cells are open to

A

the outside, but are not open to the inside of the flatworm’s body

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65
Q

How are substances brought into the inside of the flatworm’s body?

A

movement of cilia within the flame cells draw in bodily fluids

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66
Q

Which organism has tubules that open to the outside but are closed to the inside?

A

flatworms

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67
Q

What are the excretory tubules in earthworms?

A

nephridia

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68
Q

How do nephridia obtain fluid from the body?

A

fluid is filtered through nephrostomes

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69
Q

Nephridia are found in

A

earthworms

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70
Q

What are nephrostomes?

A

funnel-shaped structures that filter bodily fluids into nephridia

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71
Q

Why is the term “filtration” used?

A

fluid is formed under pressure passes through small openings such that molecules larger than a certain size are excluded

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72
Q

Describe the concentration of the filtered fluid in earthworms.

A

filtered fluid is isotonic to coelom fluid

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73
Q

What happens to the filtered fluid in earthworms as it passes through the nephridia tubules?

A

NaCl is removed from fluid via active transport

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74
Q

Most invertebrates have what kind of excretory tubules?

A

nephridia

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75
Q

Define reabsorption.

A

transport out of tubule and into the surrounding body fluids

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76
Q

What are antennal glands?

A

excretory organs of crustaceans

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77
Q

What organ in the mollusks produce urine?

A

kidneys of mollusks

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78
Q

What is the excretory organ in insects?

A

Malphigian tubules

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79
Q

What are Malphigian tubules?

A

extensions of the digestive tract that branch off anterior to the hindgut

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80
Q

(T/F) Urine is formed in insects in the Malphigian tubules.

A

False, urine is NOT formed in the Malphigian tubules.

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81
Q

Why can’t urine be formed by filtration in the Malphigian tubules?

A

there is no pressure difference between the blood in the body cavity and the Malphigian tubule

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82
Q

If urine/waste isn’t formed in the Malphigian tubule, how does it get into the Malphigian tubule?

A

waste and K+ ions are secreted into the Malphigian tubule by active transport

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83
Q

What type of transport is used to transport waste into the Malphigian tubules?

A

active transport

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84
Q

How does the flatworm expel waste that is brought into protonephridia?

A

expelled through pores that open to outside of body

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85
Q

Most invertebrates have which type of excretory tubules?

A

most invertebrates use nephridia

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86
Q

What is the opposite of reabsorption?

A

secretion

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87
Q

What is secretion in the context of insect Malphigian tubules?

A

ions/molecules are transported from body fluid into Malphigian tubule

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88
Q

What causes osmosis in Malphigian tubules?

A

secretion of K+ into tubules creates osmotic gradient that draws water into tubules via osmosis

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89
Q

What happens to most of the water/K+ brought into the Malphigian tubules?

A

reabsorbed into circulatory system through epithelium of hindgut

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90
Q

What kinds of wastes are ultimately excreted from an insect?

A

small molecules; waste products; feces

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91
Q

Generally speaking, what do the kidneys of vertebrates do?

A

create a tubular fluid by filtering blood under pressure

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92
Q

Which biomolecule is too large to be filtered from blood plasma?

A

proteins

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93
Q

Why would vertebrates filter everything except proteins from blood and then spend energy to reabsorb it?

A

because selective reabsorption provides great flexibility and allows vertebrates to reabsorb molecules that are especially valuable in certain conditions

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94
Q

What is the main unit in the vertebrate kidney?

A

nephrons

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95
Q

Describe the overall flow of fluid in the vertebrate kidney.

A

capillaries > glomerulus > Bowman’s capsule > proximal arm > loop of Henle > distal arm > collecting duct

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96
Q

What is considered the beginning of the tubule system in the vertebrate kidney?

A

Bowman’s capsule

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97
Q

The glomerulus retains

A

blood cells; proteins; most other large molecules

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98
Q

The glomerulus lets which molecules pass into the nephron?

A

water; small molecules dissolved in the water; wastes dissolved in the water

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99
Q

What kinds of transport mechanisms are used in the nephron?

A

active and passive transport

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100
Q

Draw out the Figure 50.6 on page 1043, which is titled “Organization of the vertebrate nephron.”

A

draw

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101
Q

Describe the concentration of glomerular filtrate relative to blood in vertebrates.

A

original glomerular filtrate is isotonic to blood

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102
Q

Describe the possible concentrations of urine relative to blood in vertebrates.

A

urine is isotonic to blood because of reabsorption of water/ions in equal proportions; urine is hypotonic to blood by reabsorbing less water

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103
Q

(T/F) Vertebrates cannot produce urine that is hypertonic to blood.

A

False, birds and mammals can produce urine that is hypertonic to blood.

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104
Q

Which vertebrates can produce urine hypertonic to blood?

A

birds, mammals

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105
Q

How do birds/mammals produce urine that is hypertonic to blood?

A

by reabsorbing more water

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106
Q

Kidneys are thought to have evolved among the

A

freshwater teleosts = bony fishes

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107
Q

Describe the concentration of body fluids in freshwater fish relative to the surrounding water.

A

body fluids of freshwater fish are hypertonic to surrounding water

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108
Q

What are the two problems that freshwater fish face with regards to their urinary systems?

A

water tends to enter body from environment; solutes tend to leave the body and enter environment

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109
Q

How do freshwater fish solve the problem of water entering their body from the environment?

A

by not drinking water and excreting a large volume of dilute urine

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110
Q

Describe the urine excreted by freshwater fish.

A

hypotonic to their body fluids

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111
Q

How do freshwater fish solve the problem of solutes leaving their bodies?

A

reabsorb ions across nephron tubules (from the glomerular filtrate back into blood); actively transport ions across gill surface from surrounding water into blood

112
Q

What is another name for marine bony fishes?

A

teleosts

113
Q

Where did teleosts evolve from?

A

freshwater ancestors

114
Q

Describe the concentration of body fluids of marine bony fishes relative to surrounding water.

A

body fluids are hypotonic to seawater

115
Q

What is the problem that marine bony fishes face with regards to their urinary systems?

A

water tends to leave their bodies across gills

116
Q

How do marine bony fishes solve their major problem?

A

by drinking large amounts of seawater

117
Q

What happens to divalent ions in seawater that is consumed by marine bony fishes?

A

remain in the digestive tract and are eliminated through the anus

118
Q

What kinds of ions are reabsorbed in marine bony fishes?

A

some divalent ions and some monovalent ions like K+/Na+/Cl-

119
Q

How are monovalent ions excreted in marine bony fishes?

A

actively transported across gill surfaces

120
Q

How are divalent ions excreted in marine bony fishes?

A

secreted into nephron tubules and excreted through urine

121
Q

Describe the concentration of the urine excreted by marine bony fishes relative to its body fluids.

A

urine is isotonic relative to body fluids

122
Q

Describe the concentration of the urine excreted by marine bony fishes relative to the urine produced by freshwater fishes.

A

urine of marine bony fishes is MORE concentrated than urine of freshwater bony fishes

123
Q

Describe the concentration of the urine excreted by marine bony fishes relative to the urine produced by birds/mammals.

A

urine of marine bony fishes is LESS concentrated than urine of birds/mammals

124
Q

Describe the glomerulus in freshwater fish.

A

large glomerulus

125
Q

Describe the glomerulus in marine fish.

A

glomerulus is reduced or absent

126
Q

Generally speaking, what happens in the nephrons of freshwater fish?

A

active tubular reabsorption of Na+ and Cl-

127
Q

Generally speaking, what happens in the kidneys of freshwater fish?

A

excretion of dilute urine

128
Q

Generally speaking, what happens in the gills of freshwater fish?

A

active absorption of Na+ and Cl-; water enters osmotically

129
Q

Generally speaking, what happens in the nephrons of marine fish?

A

active tubular secretion of Mg2+ and SO42-

130
Q

Generally speaking, what happens in the stomach of marine fish?

A

passive reabsorption of water, Na+, Cl-

131
Q

Generally speaking, what happens in the gills of marine fish?

A

active secretion of Na+, Cl-; water loss

132
Q

Generally speaking, what happens in the kidneys of marine fish?

A

excretion of urea, little water, Mg2+, SO42-

133
Q

What are the intestinal wastes produced by marine fish?

A

Mg2+, SO42-, feces

134
Q

What are the most common types of Chondrichthyes?

A

sharks, rays

135
Q

How do elasmobranchs solve the osmotic problem?

A

instead of continuously drinking seawater for hypotonic body fluids, they reabsorb urea from nephron tubules to maintain blood urea concentration that is 100x that of mammals

136
Q

What is the blood urea concentration in elasmobranchs?

A

100x that of mammals

137
Q

What is the consequence of elasmobranchs reabsorbing urea?

A

makes elasmobranchs’ blood isotonic to surrounding sea, which prevents water loss; no need to drink seawater; kidneys and gills don’t have to get rid of large amounts of ions

138
Q

What needed to evolve in elasmobranchs to tolerate high urea concentrations?

A

enzymes and tissues of cartilaginous fish have evolved to tolerate high urea concentrations

139
Q

What were the first terrestrial vertebrates?

A

amphibians

140
Q

The amphibian kidney is identical to

A

the kidney of the freshwater fish

141
Q

Amphibians spend most of their time in what kind of water?

A

freshwater

142
Q

Amphibians produce what kind of urine?

A

very dilute urine

143
Q

How do amphibians compensate for Na+ loss?

A

by actively transporting Na+ across skin from the surrounding water

144
Q

Marine reptiles face what problem?

A

they tend to lose water and take in salts

145
Q

(T/F) Marine reptiles drink seawater.

A

True

146
Q

What kind of urine do marine reptiles produce?

A

isotonic urine

147
Q

How do marine reptiles get rid of excess salt?

A

through salt glands located near the nose/eye

148
Q

What is a cloaca?

A

common exit of the digestive and urinary tracts

149
Q

How do terrestrial reptiles adapt to dry environments in terms of reabsorption?

A

they reabsorb most of the salt and water in their nephron tubules

150
Q

What kind of urine do terrestrial reptiles produce?

A

urine cannot be more concentrated than blood plasma

151
Q

How do terrestrial reptiles excrete urine?

A

urine isn’t excreted, instead it is emptied into cloaca where additional water is reabsorbed, then waste is excreted with feces

152
Q

In humans, how much more concentrated can urine be relative to plasma?

A

Urine can be up to 4.2 times as concentrated as blood plasma

153
Q

Which mammals produce the most concentrated urine, and how much more concentrated is it relative to their blood plasma?

A

camels - 8x; gerbils - 14x; pocket mice - 22x

154
Q

Which mammal has the most efficient kidney system?

A

kangaroo rats/Dipodomys

155
Q

(T/F) Kangaroo rats drink water.

A

False, they don’t even need to drink water because they get everything they need from food and cellular respiration

156
Q

In which organisms is the loop of Henle found?

A

only in mammals and birds

157
Q

What produces hypertonic urine in mammals/birds?

A

loop of Henle

158
Q

What is the relationship between the urine concentration and the loop of Henle?

A

the degree of urine concentration depends on the length of the loop of Henle

159
Q

Describe the nephrons found in birds.

A

very few/no nephrons with long loops

160
Q

What is the consequence of birds not having nephrons with long loops?

A

they can’t produce urine that is as concentrated as that of mammals - at max, urine is 2x more concentrated than blood

161
Q

How do marine birds solve the problem of water loss?

A

drinking salt water and then excreting excess salt from salt glands near eyes

162
Q

How is urine eliminated from the bird?

A

urine is delivered to cloaca along with feces, additional water is reabsorbed, white paste/pellet is left behind and excreted

163
Q

Where are the kidneys located in humans?

A

lower back

164
Q

Each kidney receives blood from which structure?

A

renal artery

165
Q

From the kidney, where does urine go?

A

drains out of kidney through ureter, which carries urine to urinary bladder, and urine is passed out of body via urethra

166
Q

What is the urethra?

A

tube that carries urine from the bladder to the exterior of mammals

167
Q

What are the three basic functions of the kidney?

A

filtration; reabsorption; secretion

168
Q

What happens during filtration in the mammalian kidney?

A

fluid in blood, which contains most solutes except large proteins and cells; is filtered into tubule system

169
Q

What is reabsorption in the mammalian kidney?

A

selective movement of important solutes (e.g. glucose, AAs, inorganic ions) back into the bloodstream

170
Q

What kinds of transport mechanisms are used in reabsorption in the mammalian kidney?

A

active or passive transport mechanisms

171
Q

What happens in secretion in the mammalian kidney?

A

movement of substances from blood to extracellular fluid, then into filtrate in tubule system

172
Q

How are reabsorption and secretion different?

A

reabsorbed substances from the tubules are sent back into the bloodstream; secreted substances into the tubules are excreted along with wastes

173
Q

Which structure carries blood into the glomerulus?

A

afferent arteriole

174
Q

Which structure carries blood out of the glomerulus?

A

efferent arteriole

175
Q

The kidney contains about how many nephrons?

A

1 million nephrons

176
Q

What are the two types of nephrons in mammalian kidneys?

A

juxtamedullary nephrons; cortical nephrons

177
Q

Describe juxtamedullary nephrons.

A

have long loops that dip deeply into medulla

178
Q

Describe cortical nephrons.

A

shorter loops

179
Q

What is the glomerulus?

A

cluster of capillaries enclosed by Bowman’s capsule

180
Q

What is the Bowman’s capsule?

A

bulbous unit of nephrons that surrounds the glomerulus

181
Q

What happens to blood components (i.e. proteins, cells) that are not filtered into the glomerulus?

A

blood is drained into efferent arteriole, which empties into the peritubular capillaries

182
Q

What are the peritubular capillaries?

A

bed of capillaries that surrounds the tubules

183
Q

What structure surrounds the loop of Henle?

A

vasa recta

184
Q

What is the vasa recta?

A

capillaries that surround the loop of Henle

185
Q

Why are the peritubular capillaries needed?

A

needed for secretion and reabsorption

186
Q

From the Bowman’s capsule, where does the filtrate go?

A

enters the proximal convoluted tubule

187
Q

Where is the proximal convoluted tubule located in the kidney?

A

located in the cortex of the kidney

188
Q

In a cortical nephron, where does the filtrate go after the proximal convoluted tubule?

A

filtrate flows through loop of Henle

189
Q

In cortical nephrons, the loop of Henle

A

dips only minimally into the medulla before ascending back to the cortex

190
Q

Contrast water reabsorption in juxtamedullary and cortical nephrons.

A

more water can be reabsorbed from juxtamedullary nephrons than in cortical nephrons

191
Q

In juxtamedullary nephrons, the loop of Henle

A

extends much deeper into the medulla before ascending back to the cortex

192
Q

After leaving the loop of Henle, where does the fluid go?

A

fluid goes to the distal convoluted tubule

193
Q

Where is the distal convoluted tubule located in the kidney?

A

cortex

194
Q

After leaving the distal convoluted tubule, where does the fluid go?

A

fluid drains into collecting duct

195
Q

Where does the collecting duct lead to?

A

descends into medulla where it merges with other collecting ducts to empty urine into renal pelvis

196
Q

In humans, how much blood passes through the kidneys each day?

A

2000 L of blood

197
Q

In humans, how much water leaves blood and enters the glomerulus as filtrate each day?

A

180 L

198
Q

Water is first reabsorbed by which structure in the nephron?

A

proximal convoluted tubule

199
Q

How is water reabsorbed in the collecting duct?

A

water reabsorption in the collecting duct is driven by an osmotic gradient created by the loop of Henle

200
Q

The reabsorption of biomolecules such as glucose and amino acids is driven by what transport mechanism?

A

glucose/AA reabsorption is driven by active transport/secondary active transport

201
Q

Where are renal glucose carriers located?

A

proximal convoluted tubule

202
Q

When does saturation of the renal glucose carriers occur?

A

saturation occurs when [glucose] in blood is at 180mg/100mL

203
Q

What happens if a person has a blood [glucose] greater than 180 mg/100 mL?

A

glucose remaining in filtrate is expelled in urine; indicative of untreated diabetes mellitus

204
Q

What is a diagnostic test used to diagnose diabetes mellitus?

A

testing for glucose presence in urine

205
Q

Why does penicillin have to be administered in high doses/several times per day?

A

because it is secreted rapidly into the nephrons and is eliminated in one pass

206
Q

(T/F) Urine has a low H+ concentration because it is basic.

A

False, urine has a high H+ concentration and its pH is between 5 and 7.

207
Q

Why is urine’s high H+ concentration important?

A

helps maintain acid-base balance of blood within the pH range of 7.35 to 7.45.

208
Q

What is the relationship between volume of urine and blood pressure?

A

the larger the volume of urine excreted, the lower the blood volume, and the lower the BP

209
Q

Virtually all nutrient molecules are reabsorbed into the bloodstream via what structure?

A

proximal convoluted tubule

210
Q

What fraction of NaCl and water that is filtered into the Bowman’s capsule is reabsorbed by the proximal convoluted tubule?

A

2/3 of NaCl and water are immediately reabsorbed by the proximal convoluted tubule

211
Q

What drives the reabsorption of water in the proximal convoluted tubule?

A

active transport of Na+ out of filtrate means Cl- follows passively because of chemical attraction and water follows because of the concentration difference

212
Q

The water remaining after reabsorption by the proximal convoluted tubule is reabsorbed by

A

the collecting duct

213
Q

What fraction of water is reabsorbed by the collecting duct?

A

1/3 - 2/3 of it was already reabsorbed by the proximal convoluted tubule

214
Q

What is the primary function of the loop of Henle?

A

to create a gradient of increasing osmolarity from the cortex to the medulla

215
Q

The gradient created by the loop of Henle allows for

A

water to be reabsorbed by osmosis in collecting duct as it runs down into the medulla past the loop of Henle

216
Q

How do the descending and ascending portions of the loop of Henle differ?

A

differ in structure and in permeability to ions/water

217
Q

Which part of the loop of Henle is impermeable to water?

A

entire ascending limb is impermeable to water

218
Q

The ascending limb of the loop of Henle is impermeable to

A

water

219
Q

What does the thick portion of the ascending limb do?

A

active transport of Na+ out of tubule and Cl- passively follows

220
Q

What does the thin portion of the ascending limb do?

A

permeable to both Na+ and Cl-, which move out by diffusion

221
Q

Is the descending limb thick or thin?

A

The descending limb is thin.

222
Q

Describe the permeability of the descending limb.

A

permeable to water; impermeable to NaCl

223
Q

In which part of the loop of Henle are ions lost?

A

ascending limb

224
Q

In which part of the loop of Henle is water lost?

A

descending limb

225
Q

Why/how does water leave from the descending limb?

A

Because ions are leaving from the ascending limb which creates an osmotic gradient, so water leaves, too

226
Q

Compare the osmolarity of the interstitial fluid and the fluid in the descending limb.

A

Osmolarity of interstitial fluid is higher because Na+ and Cl- ions are coming into the interstitial fluid

227
Q

What is the consequence of water loss on the concentration of fluid in the loop of Henle as we move from the descending to the ascending loop?

A

the concentration multiplies/increases; in humans, the [filtrate] at the top is 300 mOsm whereas at the bottom of the loop it is >1200 mOsm

228
Q

What is the relationship between the length of the loop of Henle and the concentration of fluid in the loop of Henle.

A

longer loop of Henle means greater total concentration that can be achieved

229
Q

What happens to the Na+/Cl- pumped out of the ascending limb?

A

reabsorbed into the loops of the vasa recta

230
Q

What kind of exchange is used in the vasa recta?

A

countercurrent exchange

231
Q

Why is countercurrent exchange important in the vasa recta?

A

prevents flow of blood through its capillaries from destroying the loop of Henle’s osmotic gradient

232
Q

What is the countercurrent multiplier system?

A

action of loop of Henle creating a hypertonic renal medulla

233
Q

Which substances contribute to the overall “saltiness”/osmolarity of the renal medulla?

A

Na+, Cl-, and urea

234
Q

Which structures of the nephron are permeable to urea?

A

Descending limb and collecting duct are permeable to urea

235
Q

Describe the concentration nature of the fluid that arrives at the distal convoluted tubule.

A

hypotonic, with a concentration of 100 mOsm

236
Q

What happens after the fluid reaches the distal convoluted tubule?

A

fluid plunges down into the medulla via the collecting duct

237
Q

What happens to the fluid while in the collecting duct?

A

the interstitial fluid is hypertonic, so an osmotic gradient pulls water out of the collecting tubule

238
Q

What controls the permeability of the distal convoluted tubule and collecting duct?

A

antidiuretic hormone (ADH)

239
Q

What happens hormonally if an animal needs to conserve water?

A

more ADH is secreted, which increases the number of water channels in the collecting duct cells - increases permeability

240
Q

Describe the relationship between ADH levels and the need for water conservation.

A

If more water needs to be conserved, more ADH will be secreted.

241
Q

What secretes ADH?

A

posterior pituitary gland

242
Q

Where is K+ reabsorbed?

A

proximal convoluted tubule

243
Q

Where is K+ secreted?

A

distal convoluted tubule

244
Q

Why is K+ reabsorbed and then secreted?

A

to maintain homeostasis

245
Q

How do kidneys maintain acid-base balance?

A

by excreting H+ into urine and reabsorbing HCO3-

246
Q

Where is HCO3- reabsorbed?

A

proximal convoluted tubule

247
Q

Where is H+ secreted?

A

distal convoluted tubule

248
Q

What does aldosterone do, generally?

A

controls reabsorption of NaCl in the distal convoluted tubule and collecting duct

249
Q

The reabsorption of NaCl in the distal convoluted tubule and collecting duct is controlled by

A

aldosterone

250
Q

Which two hormones influence the distal convoluted tubule/collecting duct?

A

antidiuretic hormone and aldosterone

251
Q

What produces ADH?

A

hypothalamus

252
Q

What is the primary stimulus for ADH secretion?

A

increase in osmolarity of blood plasma

253
Q

ADH stimulating water reabsorption is what kind of feedback loop?

A

negative feedback loop

254
Q

What is the name for the water channels present in the cells of the distal convoluted tubule/collecting duct?

A

aquaporins

255
Q

On a molecular level, how does ADH stimulate water reabsorption?

A

stimulates fusion of vesicle membrane with plasma membrane such that aquaporins are in place to allow water to flow through

256
Q

When secretion of ADH is reduced, what happens on a molecular level?

A

plasma membrane pinches in to form new vesicle that contains aquaporins; aquaporins no longer in place

257
Q

Under conditions of maximal ADH secretion, how much concentrated urine is released by a person?

A

600 mL of highly concentrated urine per day

258
Q

What is diabetes insipidus?

A

condition characterized by a lack of ADH due to pituitary damage

259
Q

What are the effects of diabetes insipidus?

A

severe dehydration; low blood pressure

260
Q

What two common drugs also inhibit ADH?

A

ethanol; caffeine

261
Q

What is the major solute in blood plasma?

A

Na+

262
Q

If blood [Na+] falls, what else falls?

A

blood osmolarity also falls

263
Q

A drop in blood Na+ is compensated for by

A

aldosterone

264
Q

What secretes aldosterone?

A

adrenal cortex

265
Q

What senses decreased blood flow?

A

juxtaglomerular apparatus

266
Q

What is the juxtaglomerular apparatus?

A

a group of cells that recognize decreased blood flow

267
Q

Where is the juxtaglomerular apparatus located?

A

between the distal convoluted tubule and afferent arteriole

268
Q

In response to low blood flow, what does the juxtaglomerular apparatus do?

A

secretes renin

269
Q

What does renin do?

A

catalyzes production of angiotensin I from angiotensinogen

270
Q

What does angiotensin I do?

A

is converted to angiotensin II, which stimulates blood vessel constriction and the secretion of aldosterone

271
Q

Homeostasis of blood volume/pressure can be maintained by activating the

A

renin-angiotensin-aldosterone system

272
Q

What else does aldosterone do, in addition to Na+ reabsorption?

A

stimulates K+ secretion into the distal convoluted tubule and collecting duct

273
Q

Which hormone opposes aldosterone?

A

atrial natriuretic hormone (ANH)

274
Q

ANH is secreted by

A

the right atrium of the heart

275
Q

What does ANH do? (2)

A

promotes excretion of salt and water in urine; lowers blood volume

Biology 2312 (11 decks)

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