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Animal Physiology > Ion + Water Balance > Flashcards

Ion + Water Balance Flashcards

1
Q

What can environment refer to in animal physiology?

A

the external world for the entire organism

the extracellular fluid for a cell

the cytoplasm for intracellular enzymes

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2
Q

What are the 3 homeostatic processes of body fluid regulation?

A

osmotic regulation
ionic regulation
nitrogenous waste excretion

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3
Q

What is osmotic regulation?

A

regulation of the osmotic pressure of body fluids

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4
Q

What is ionic regulation?

A

the regulation of specific ion concentrations in body fluids

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5
Q

What is nitrogenous waste excretion as a process of body fluid regulation?

A

the excretion of urea and uric acid (end products of protein metabolism) from the body

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6
Q

What are the major ions in salt and freshwater?

A

sodium
chloride
magnesium
sulfate
calcium
potassium
bicarbonate

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7
Q

Which major ions are most highly concentrated in seawater vs. freshwater?

A

seawater:
- Na
- Cl
- Mg
- Sulfate

fresh:
- bicarbonate
- Ca
- Na

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8
Q

How does the concentration of Na compare in seawater to freshwater?

A

seawater 470 mM > 0.35 mM fresh

sea > > fresh

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9
Q

How does the concentration of Cl compare in seawater to freshwater?

A

sea > > fresh

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10
Q

How does the concentration of bicarbonate compare in seawater to freshwater?

A

sea > fresh

sea = 2, fresh = 1.72

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11
Q

T or F: all of the major ions are concentrated more heavily in seawater than fres h

A

true

bicarbonate is the only one that comes close in freshwater to seawater concentrations

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12
Q

How does the osmolarity of seawater compare to that of freshwater?

A

seawater > > freshwater

sea ~1100 mOsm/L
fresh 0.5-10 mOsm/L

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13
Q

What is osmolarity?

A

the number of solute particles per 1L of solvent

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14
Q

How does the RATIO of concentration of major ions (Na, Cl, K) in the intracellular and extracellular fluid of squid axons compare to mammalian muscles?

A

squid axons have lower ratios of ions in/out than mammals

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15
Q

How does the osmolarity of major ions (Na, Cl, K) in the intracellular and extracellular fluid of squid axons compare to mammalian muscles?

A

squid axons have much higher osmolarity than mammalian muscles

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16
Q

What osmotic and ionic challenges do animals face in marine environments?

A

the environmental conditions (high osmolarity) make it easy to gain salts and easy to lose water

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17
Q

What osmotic and ionic challenges do animals face in freshwater environments?

A

the low osmolarity conditions make it easy to lose salts and easy to gain water

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18
Q

What osmotic and ionic challenges do animals face in terrestrial environments?

A

less water outside body than inside = easy to lose water

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19
Q

What is the osmoregulatory and ionoregulatory strategy of marine arthropods?

A

isosmotic
no ionoregulation

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20
Q

What is the osmoregulatory and ionoregulatory strategy of marine molluscs (ex. squid)?

A

slightly hyperosmotic
ionoregulation

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21
Q

What is the osmoregulatory and ionoregulatory strategy of marine fish, amphibians, reptiles, mammals, birds?

A

hyposmotic
ionoregulation

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22
Q

What is the osmoregulatory and ionoregulatory strategy of freshwater arthropods?

A

hyperosmotic
ionoregulate

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23
Q

What is the osmoregulatory and ionoregulatory strategy of freshwater molluscs (ex. clams)?

A

slightly hyperosmotic
ionoregulate

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24
Q

What is the osmoregulatory and ionoregulatory strategy of freshwater fish, amphibians, reptiles, mammals, birds?

A

hyperosmotic
ionoregulate

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25
Q

generally, all aquatic animals except ____ have strategies for ionoregulation

A

except marine arthropods and hagfish

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26
Q

What is hyposmotic?

A

when the organism has lower internal osmotic pressure than the external environment

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27
Q

What is hyperosmotic?

A

when the animal has higher internal osmotic pressure than the external environment

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28
Q

What is isosmotic?

A

when the animal has the same internal osmotic pressure as the external environment (does not regulate)

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29
Q

generally, all aquatic animals except ____ have a strategy for osmoregulation

A

except marine arthropods

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30
Q

Most freshwater animals are ___osmotic?

A

hyperosmotic (higher osmolarity internally)

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31
Q

What are the 2 strategies for overcoming osmotic challenges?

A

osmoconformer
osmoregulator

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32
Q

What is an osmoconformer? give an example

A

animals that do not regulate their internal osmotic pressure and internal osmolarity matches the external environment

ex. marine invertebrates (arthropods)

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33
Q

What is an osmoregulator? give an example

A

animals that regulate internal osmolarity to be different than that of the external environment

ex. most vertebrates

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34
Q

Most marine vertebrates are ____osmotic?

A

hyposmotic (lower internal osmolarity than external)

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35
Q

What are the 2 strategies for ionic regulation?

A

ionoconformer
ionoregulator

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36
Q

What is an ionoconformer? give an example

A

animals that don’t regulate their ionic concentrations and match that of the external environment

ex. marine invertebrates (marine organisms only)

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37
Q

What is an ionoregulator? give an example

A

animals that maintain ionic concentrations different from that of the external environment

ex. most vertebrates

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38
Q

Organisms in what environment are the only examples of ionoconformers?

A

only marine animals

ex. many marine invertebrates

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39
Q

T or F: some freshwater animals are ionoconformers

A

false, only some marine animals are known to be ionoconformers

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40
Q

What is ECF?

A

extracellular fluid

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41
Q

How do cells control cell volume?

A

water is moved in and out of cells via osmosis (follows solutes) through aquaporins

cells transport solutes in and out of ECF and water follows solutes

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42
Q

What is osmosis?

A

the flow of water from an area of low solute concentration to high solute concentration

basically, water follows the flow of solutes

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43
Q

How does water move through the hydrophobic cell membrane?

A

through aquaporins

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44
Q

Why do animal cells need to regulate the composition of ECF?

A

to provide cells with an external solution that allows them to have the right cell volume

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45
Q

What causes a change in cell volume?

A

environmental osmotic stress

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46
Q

What happens to cells in hypotonic environments?

A

HYPOtonic = external environment has lower solute concentration than in cells

water follows concentration of solutes= water flows into the cell

cell swells and can explode

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47
Q

What happens to cells in hypertonic environments?

A

HYPERtonic = external environment has higher solute concentration than inside cells

water flows out of cells causing cells to shrink and die

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48
Q

How do cells control their volume?

A

by regulating solutes across their membrane

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49
Q

How do cells regulate volume increase?

A

by importing ions

import of ions brings influx of water

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50
Q

How do cells regulate volume decrease?

A

by exporting ions

export of ions allows efflux of water

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51
Q

What ion channels or transporters are involved in regulatory volume increase?

A

to swell cells:

Cl- and Na+ channels open (influx)

Na+, K+, 2Cl- cotransporter brings in these ions

Na+/H+ exchanger brings in Na+ in exchange for H+

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52
Q

What ion channels or transporters are involved in regulatory volume decrease?

A

to shrink cells

K+ and Cl- channels open = efflux

K+/Cl- cotransporter active

3Na+ / Ca2+ exchanger pumps out 3 Na+ for 1 Ca2+

Na+/K+ ATPase pumps out 3 Na+ for 2 K+

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53
Q

Who won the Nobel Prize for chemistry in 2003 for the discovery of water channels (aquaporins)?

A

Peter Agre, Johns Hopkins

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54
Q

What is the function of epithelial tissues? what is an example?

A

they are the outermost layer of an animal and they form a barrier between the animal’s internal environment and an external environment

external surfaces: ex. integument
internal surfaces: ex. lumen of digestive system, kidney, respiratory tract

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55
Q

What physiological functions do epithelial tissues have?

A

respiratory
digestive
ion and water regulation

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56
Q

How do animals limit water movement across body surface?

A
  1. by limiting permeability of the epithelial tissues (integument)
  2. layers of hydrophobic molecules on external surfaces
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57
Q

By what factor do aquaporins increase water permeability of a membrane?

A

by 100x

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58
Q

How do animals limit permeability of integument to water?

A

reducing concentration of aquaporins on the integument

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59
Q

What type of hydrophobic molecules might animals use to layer integument to reduce water flux?

A

mucus cells

Cornified stratum corneum with keratin

cuticle made of chitin

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60
Q

What are examples of animals that use mucus cells to create a protective hydrophobic barrier around their integument?

A

lungfish
frogs

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61
Q

What are examples of animals that use cornified stratum corneum with keratin to create a protective hydrophobic barrier around their integument?

A

animals with skin

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62
Q

What is the cornified stratum corneum?

A

a hydrophobic barrier composed of keratin and lipids

(skin)

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63
Q

What are examples of animals that use a cuticle to create a protective hydrophobic barrier around their integument?

A

animals with chitin exoskeletons such as insects, spiders, crustaceans

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64
Q

What composes an arthropods cuticle layer?

A

chitin

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65
Q

Describe the structure of an epithelial cell

A

apical membrane (faces external environment) has ion transporters

between epithelial cells, tight junctions prevent water from moving between cells

within cell, many mitochondria

basolateral membrane (faces internal environment) has ion transporters and contacts basement membrane

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66
Q

T or F: epithelial cells play an important role in ion transport

A

true for digestive tract, kidneys, gills

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67
Q

What are the 4 major features of epithelial cells involved in ion transport?

A
  1. asymmetrical membrane transporters
  2. tight junctions between cells
  3. high cell diversity within tissue
  4. abundant mitochondria
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68
Q

What is important about the asymmetry of transporters on epithelial cells?

A

solutes are transported selectively across the membrane

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69
Q

What is important about the tight junctions between epithelial cells?

A

this forms an impenetrable sheet of tissues and prevents leakage between cells

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70
Q

What is important about the high abundance of mitochondria in epithelial cells?

A

they have a large energy supply

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71
Q

What are the 2 main routes of ion transport for epithelial cells?

A

transcellular
paracellular

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72
Q

Describe transcellular transport

A

movement of ions through a cell across membranes

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73
Q

describe paracellular transport

A

movement of ions between cells through leaky or tight gap junctions

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74
Q

what 4 types of transporters exist on epithelial cells?

A

Na/K ATPase and other ATPases
ion channels (Cl, K, Na)
electroneutral cotransporters
electroneutral exchangers

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75
Q

T or F: epithelial cells are massive consumers of ATP - why/why not?

A

true because they have a high abundance of mitochondria so they need a lot of ATP

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76
Q

What are the 2 types of epithelial cells in fish gills?

A

chloride cells

pavement cells

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77
Q

What are chloride cells? describe them

A

a type of epithelial cell on fish gills

they are large mitochondria-rich cells

aka PNA+ cells

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78
Q

What is PNA?

A

peanut lectin agglutin

a glycoprotein that binds carbohydrates on chloride cells

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79
Q

What type of cells in fish gills have PNA?

A

only the chloride cells

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80
Q

Which fish gill cells are PNA+? PNA-?

A

chloride cells are PNA+
pavement cells are PNA- (no PNA)

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81
Q

What are pavement cells? describe them

A

a type of epithelial cell found on fish gill surfaces

flatter, smaller cells usually with less mitochondria than chloride cells
do NOT have PNA

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82
Q

What are the functions of the chloride and pavement cells in fish gills?

A

to mediate transport of ions

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83
Q

T or F: all pavement cells are mitochondria rich, but not all are PNA-

A

false

all pavement cells are PNA-
some are mitochondria-rich
some are mitochondria-poor

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84
Q

Which of the epithelial cells in fish gills are more likly to do ion transport?

A

mitochondria rich chloride and mitochondria-rich pavement cells

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85
Q

What does the direction of ion transport depend on?

A

water salinity

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86
Q

Describe the direction of ion transport across a freshwater fish gill via mitochondria-rich pavement and chloride cells

A

pavement cells:
- ions (ex. Na+) are transported across the apical membrane from the external environment inside the pavement cells
- Na+

pavement cells:
- low external salinity, Na+ ions transported across apical membrane into cell
- basolateral side: Na+ and HCO3- transported across basolateral membrane, K+, Cl-, CO2 transported into cell

chloride cells:
- Ca2+ and Cl- transported across apical membrane into cell
HCO3- transported to external environment
- Ca+ x2, Na+, H+ transported across basolateral membrane out of cell
- Na+, K+, CO2 transported across basolateral membrane into cell

87
Q

What ions are transported into the pavement cells across the apical membrane of freshwater fish?

A

Na+

from the environment

88
Q

What ions are transported into the pavement cells across the basolateral membrane of freshwater fish?

A

K+
Cl-
CO2

from internal environment

89
Q

What ions are transported out of the pavement cells across the basolateral membrane of freshwater fish?

A

Na+
HCO3-

from inside the cell to the internal environment

90
Q

What ions are transported into the chloride cells across the apical membrane of freshwater fish?

A

Ca2+
Cl-

from external environment

91
Q

What ions are transported out of the chloride cells across the apical membrane of freshwater fish?

A

HCO3- from inside the cell to the external environment

92
Q

What ions are transported into the chloride cells across the basolateral membrane of freshwater fish?

A

Na+
K+
CO2

from internal environment into the cell

93
Q

What ions are transported out of the chloride cells across the basolateral membrane of freshwater fish?

A

Ca+ x2
Na+
H+

from inside cell to internal environment

94
Q

What ions are transported out the pavement cells across the apical membrane of freshwater fish?

A

H+

from inside cell to external environment

95
Q

What ions are transported into the chloride cells across the apical membrane of marine fish?

A

NONE

only influx transport across basolateral membrane

96
Q

What ions are transported out of the chloride cells across the apical membrane of marine fish?

A

Cl-

from inside cell to external environment

97
Q

What ions are transported into the chloride cells across the basolateral membrane of marine fish?

A

2K+
Na+
2Cl-

from internal environment into cell

98
Q

What ions are transported out of the chloride cells across the basolateral membrane of marine fish?

A

Na+
K+

from inside cell to internal environment

99
Q

What ions are transported from internal environment directly to external without membrane transporters? how?

A

Na+ can diffuse out of the internal environment between chloride and pavement cells of fish gills

100
Q

What is a diadromous animal?

A

an animal that can migrate between seawater and freshwater throughout its life

101
Q

What is anadromous? what is an example?

A

when the animal spends most of its adult life in marine environment and returns to freshwater to spawn and die

ex. salmon

102
Q

How do juvenile salmon adapt their physiology to prepare for the change from freshwater to seawater?

A

smoltification

103
Q

What is smoltification?

A

the process of reorganizing the ion-pumping properties to prepare juvenile salmon for entering seawater from freshwater

and changes to the GI tract and kidney to adjust ion-water balance regulation

104
Q

What mediates smoltification in salmon?

A

a growth hormone, insulinlike growth factor 1 and cortisol mainly

105
Q

What happens to adult salmon gills when preparing to migrate into different salinity?

A

transitions from ion-secreting to ion-absorbing epithelium for moving into freshwater or vice versa for moving into salt water

genes coding for Na/K ATPase change in isoform

a1a increase for freshwater (ion-absorption)
a1b increase for saltwater (ion secretion)

106
Q

Where are water and salts from drinking and food transported?

A

across digestive epithelial cells

107
Q

What type of transport is involved in digestive epithelium?

A

transcellular and paracellular

108
Q

What happens to the water and salts that are transported across digestive epithelia?

A

they enter bloodstream

109
Q

What organ is key for maintaining ion and water balance in vertebrates?

A

the kidney

110
Q

What are the 6 major homeostatic roles of vertebrate kidneys?

A

ion balance
osmotic and water balance
blood pressure
pH balance
excretion of nitrogenous wastes and toxins
hormone production

111
Q

describe the structure of the mammalian kidney

A

bean shaped

112
Q

What are the layers of the mammalian kidney?

A

renal cortex: outermost
renal medulla: inner layer

113
Q

What are the structures within the mammalian kidney?

A

renal cortex - outermost layer
renal medulla - inner layer consisting of the renal pyramids and renal papilla

renal pelvis
minor calyx
major calyx
renal artery and vein
ureter - tube that drains kidney into urinary bladder

114
Q

What drains urine into the ureters from the kidneys? where does that urine drain to?

A

minor calyxes drain urine into major calyx which drains urine into a ureter which drains into the bladder

115
Q

How many kidneys do mammals have?

A

2

= 2 ureters drain into 1 bladder and 1 urethra

116
Q

What is the functional unit of the kidney?

A

nephrons

117
Q

~how many nephrons per kidney?

A

~1 million

118
Q

What composes the nephron?

A

renal corpuscle (composed of the Glomerulus, Bowman’s capsule)

renal tubules

119
Q

What composes the renal corpuscle of a nephron?

A

Glomerulus and Bowman’s capsule

120
Q

What is the Glomerulus?

A

a ball of capillaries within the Bowman’s capsule = the renal corpuscle of a nephron

121
Q

What is the Bowman’s capsule?

A

a capsule lined with epithelial cells that surround the capillary ball (glomerulus) in the nephrons of a kidney

122
Q

What are the renal tubules?

A

part of a nephron

they are lined with transport epithelial cells and are segmented with specific transport functions

123
Q

What layer of the kidney are Bowman’s capsule and glomerulus located?

A

in the renal cortex

124
Q

What part of a nephron is located in the renal medulla?

A

the loop of Henle and collecting duct

125
Q

What are the 4 functions of neurons (ie, renal processes)?

A

filtration of blood

reabsorption of filtrate

secretion of wastes and toxins

excretion of nitrogenous waste

126
Q

Where in the nephron does the filtration of blood occur?

A

blood filtrate formed at glomerulus (in Bowman’s capsule)

127
Q

How much blood is filtered per day in an adult human?

A

~180 L/day

~7.5L/hr

128
Q

What do nephrons reabsorb?

A

the filtrate is reabsorbed after specific molecules have been removed

129
Q

How much filtrate is reabsorbed by nephrons?

A

~99% (including water)

130
Q

What is secreted by nephrons?

A

the specific molecules removed from blood are added to the filtrate

ex. K+, H+, NH4+, urea, phamaceuticals, drugs, toxins

131
Q

What is excreted by nephrons?

A

nitrogenous wastes - urine

132
Q

How much urine is excreted by nephrons?

A

75 ml/hr

~1% of the filtrate

133
Q

Describe filtration in nephrons

A

liquid components of blood flow into the bowman’s capsule through the glomerulus (coated in capillaries)

water and small solutes transport across glomerular wall but NOT blood cells or large macromolecules

podocytes and foot processes on outside of capillaries form filtration structure

filtrate flows from Bowman’s into proximal tubule

134
Q

What controls the blood pressure and filtration within the glomerulus?

A

mesangial cells

135
Q

T or F: glomerular capillaries are very leaky

A

true

they are only coated with spread out podocytes and foot processes which allow filtrate to leak out of glomerulus

136
Q

What type of solutes cross the glomerular wall into the bowman’s capsule?

A

water and small solutes

NOT blood cells or macromolecules

137
Q

Where does the filtrate that leaked from the glomerulus into the Bowman’s capsule go next?

A

to the proximal tubule

138
Q

What type of transporters is the proximal tubule epithelia rich in?

A

Na/K ATPAse
ion transporters (Na+, glucose)
some ion channels (Cl-)

139
Q

Does the apical membrane of a nephron face tubular fluid or peritubular space?

A

tubular fluid (inside the nephron)

140
Q

Does the basolateral membrane of a nephron face tubular fluid or peritubular space?

A

peritubular space

141
Q

what is the renal threshold?

A

the saturation limit of the transporters on epithelial cells of a nephron

142
Q

Describe the renal threshold graph for plasma [glucose] x vs. glucose flux y

A

as glucose levels increase in the blood:

amount of glucose filtered by kidneys = the amount of glucose reabsorbed by kidneys (linear increase)

until saturation (renal threshold)
at which point,

glucose will continue to be filtered but reabsorption will plateau and the concentration of glucose in urine will increase

143
Q

What happens to glucose flux when reabsorption of glucose is less than the filtration of glucose?

A

if glucose concentration increases past the renal threshold

the transporters are saturated and no more glucose can be reabsorbed by the nephrons of the kidney, so more glucose is filtered out and enters the urine

= higher glucose levels in urine

144
Q

What is primary urine?

A

the initial filtrate that is filtered in the Bowman’s capsule which is isosmotic to blood (same ion concentrations)

145
Q

Describe reabsorption

A

most of the water, salt and glucose in the primary urine is reabsorbed via transport proteins and energy

each segment of a nephron has specific transporters for specific solutes

146
Q

T or F: reabsorption of water, salts and glucose from primary urine requires energy input

A

true

147
Q

What limits the rate of reabsorption by nephrons?

A

the number of transporters on the epithelial cells

148
Q

What are the 4 segments of the nephron involved in reabsorption?

A

proximal tubule
loop of Henle
distal tubule
collecting duct

149
Q

What does the proximal tubule of a nephron reabsorb?

A

most of the solute (salt, glucose) and water

150
Q

What does the loop of Henle of a nephron reabsorb?

A

the descending limb reabsorbs water

the ascending limb reabsorbs ions

151
Q

What does the distal tubule of a nephron reabsorb?

A

completes the reabsorption of solutes and water

152
Q

What is the function of the collecting duct?

A

it regulates the final urine composition
it collects urine from multiple nephrons and drains into the renal pelvis of the kidney

153
Q

T or F: there’s only one nephron per collecting duct

A

false, multiple nephrons can drain into a single collecting duct

154
Q

Where does the collecting duct bring urine to?

A

the renal pelvis of the kidney to be drained through the ureter into the bladder

155
Q

What allows for the differences in transport and permeability along a nephron’s tubule?

A

the different epithelial cells lining the tubule

156
Q

Where does most of the reabsorption in the tubules of a nephron occur?

A

in the proximal tubule

157
Q

What type of transporters are on the epithelial cells of the proximal tubule? what kind of solutes do they transport?

A

Na+ contransporters of:

glucose
lactate
AAs
water-soluble vitamins
phosphates

water follows these by osmosis

158
Q

What molecules does the proximal tubule secrete?

A

organic anions (ex. cAMP)
organic cations (ex. norepinephrine, ACh)
drugs and toxins

absorb from the blood stream and secrete into the lumen of the nephron to be moved with filtrate

159
Q

What is the descending limb permeable to? / what does it reabsorb?

A

water

160
Q

What occurs in the descending limb of henle?

A

water is reabsorbed = the volume of primary urine in the nephron lumen decreases and becomes more concentrated

161
Q

What is the ascending limb permeable to?

A

ions

162
Q

What happens in the ascending limb of henle?

A

ions are reabsorbed

primary urine in the lumen of a nephron becomes dilute

water does not move, this limb is impermeable to water

163
Q

What happens as the reabsorbed ions accumulate in the interstitial fluid via the ascending limb of the loop of henle?

A

it creates an osmotic gradient in the renal medulla to allow for the reabsorption of water

164
Q

Describe the osmotic gradient created by the loop of henle

A

it is counter current

as tubular fluid enters the proximal tubule and drains down the descending limb, the osmolarity is low

as tubular fluid flows down the descending limb and water is reabsorbed from the primary urine, osmolarity increases (more concentrated urine)

as tubular fluid flows up the ascending limb and ions are reabsorbed but no flow of water, the tubular fluid becomes more dilute

the tubular fluid that enters the distal tubule is more diluted

165
Q

How does the osmolarity of the tubular fluid compare at the proximal tubule v. the Loop of Henle v. the distal tubule?

A

at the proximal tubule, the primary urine is both high in water and ion concentration = low osmolarity

at the bottom of the loop of henle, water has been reabsorbed = very high osmolarity

at the distal tubule, ions have been reabsorbed, = low osmolarity

166
Q

Where does the loop of henle occur?

A

in the renal medulla

167
Q

Where are the proximal and distal tubules?

A

in the renal cortex

168
Q

What occurs in the distal tubule?

A

more reabsorption of salts and water from primary urine

secretion of potassium into primary urine

169
Q

What regulates the transport in distal tubules and collecting ducts?

A

hormones:

parathormone
aldosterone
vassopressin

170
Q

What does parathormone do?

A

increase Ca2+ reabsorption by the distal tubule and collecting duct

171
Q

What does aldosterone do?

A

increase Na+ reabsorption and K+ secretion by the distal tubule and collecting duct

172
Q

What does vassopressin do?

A

increase water reabsorption by the distal tubule and collecting duct

173
Q

What type of response (slow/fast) do steroid hormones have on kidney function?

A

steroid hormones like aldosterone have a slow response on kidney function because they affect transcription and translation

174
Q

What type of response (slow/fast) do peptide hormones have on kidney function?

A

peptide hormones like vassopressin and parathormone have a rapid response on kidney function

175
Q

Which of the 3 hormones mentioned that affect kidney function have fast responses? slow?

A

fast: vassopressin and parathormone
slow: aldosterone

176
Q

What part of the kidney do hormones (vasopressin, parathormone, aldosterone) effect?

A

distal tubules and collecting duct

177
Q

What determines the filtration rate of the glomerulus (GFR)?

A

the pressure across the glomerular wall

178
Q

What are the 3 main forces that cause pressure changes to the glomerular wall which effect GFR?

A

glomerular capillary hydrostatic pressure

bowman’s capsule hydrostatic pressure

oncotic pressure = osmotic pressure created by protein concentration in blood

179
Q

What is hydrostatic pressure?

A

the pressure exerted by a fluid at equilibrium due to gravity

180
Q

What are the regular directions and pressures of the GFR?

A

the blood pressure in the glomerulus is at 60 mmHg

the fluid in the bowman’s capsule lumen has hydrostatic pressure of 15 mmHg

= blood filtrate is pushed out of glomerulus into lumen of bowman’s capsule

= fluid in lumen is pushed out of bowman’s capsule into glomerulus

the glomerulus has protein (oncotic) pressure of 30 mmHg and filtrate pumped into lumen has lower oncotic pressure than blood so it is pumped into the glomerulus

181
Q

What is the net GFR?

A

60 out of glomerulus
30 + 15 in glomerulus

net = 15

182
Q

What direction does the blood filtrate flow between glomerulus and BC?

A

filtrate is pumped out of glomerulus into bowman’s capsule

183
Q

What direction does fluid in the lumen of the BC flow between that and the glomerulus?

A

fluid in lumen pumped into glomerulus

184
Q

what are the 3 pathways for intrinsic regulation of GFR?

A

myogenic
tubuloglomerular feedback
mesangial control

185
Q

Describe myogenic regulation of GFR

A

constriction and dilation of afferent arterioles control hydrostatic pressure and flow of fluids

186
Q

Describe tubuloglomerular feedback of GFR

A

in the juxtaglomerular apparatus:
- macula densa cells in the distal tubule
- juxtaglomerular cells in the afferent arteriole

macula densa cells control the diameter of the afferent arteriole

187
Q

Describe mesangial regulation of GFR

A

mesangial cells alter the permeability of the glomerulus

they also increase/decrease of flow into glom by stretching or constricting capillaries

188
Q

Both myogenic and tubuloglomerular feedback involve changes in ________, whereas mesangial control involves changes to ____ of the filter

A

filtration pressure

surface area

189
Q

How are mesangial cells involved in the negative feedback of GFR?

A

when arterial blood pressure increases
mesangial cells in the capillaries around the glomerulus stretch = causes them to contract

contraction reduces SA of the filter = brings GFR back to normal

stretch = contract = decreased GFR

190
Q

What type of feedback are the intrinsic pathways of regulating GFR?

A

negative feedback to create a narrow range of blood pressure

191
Q

describe tubuloglomerular feedback in the distal tubule

A

macula densa sense increased urine flow in distal tubule and signal juxtaglomelular cells of the afferent arteriole to cause vasoconstriction = decreased hydrostatic pressure = decreased GFR

vasoconstriction = decreased pressure = decreased GFR

192
Q

describe myogenic regulation of GFR

A

increased arterial blood pressure will raise GFR

increased BP stretches smooth muscle cells in the afferent arteriole = stretch-sensitive ion channels activated = depolarization = contraction of smooth muscles = vasoconstriction = decreased blood flow = decreased hydrostatic pressure = decreased GFR

193
Q

Which hormone is antidiuretic?

A

vasopressin (ADH)

194
Q

What other peptide hormones can affect urinary function?

A

renin-angiotensin - can be slow or rapid

195
Q

How does vasopressin affect kidney function?

A

increases water reabsorption by the collecting ducts and distal tubules by increasing number of aquaporins

196
Q

Where is vasopressin produced? where is it released?

A

hypothalamus and released by posterior pituitary

197
Q

Describe the steps of vasopressin increasing water absorption in the distal tubules and collecting ducts

A

hypothalamus receives signal of increased osmolarity = produces ADH (vasopressin)

posterior pituitary gland releases ADH

ADH binds to G-protein coupled receptor on nephron epithelial cells to activate it

triggers adenylate cyclase, cAMP, PKA pathway

cytoskeletal and vesicle proteins are phosphorylated

translocation of vesicles to the cells for the membrane to be inserted with aquaporins

198
Q

T or F; the collecting duct does not normally absorb water

A

true

199
Q

What stimulates the release of vasopressin?

A

osmoreceptors of the hypothalamus receive signal of increased plasma osmolarity

200
Q

What inhibits the release of vasopressin?

A

increased blood pressure detected by the stretch receptors of the atria and baroreceptors in the carotid and aortic bodies

201
Q

What is aldosterone?

A

a mineralcorticoid that controls ion excretion

202
Q

What produces aldosterone?

A

adrenal cortex

203
Q

How does aldosterone affect kidney function in the distal and collecting duct?

A

it stimulates Na+ reabsorption from urine and K+ secretion into urine

stimulates production of Na/K ATPase for the basolateral membrane

stimulates production of Na+ and K+ channels for the apical membrane

204
Q

What are the steps of aldosterone increasing Na+ reabsorption?

A

the adrenal cortex is stimulated by:
- angiotensin II
- High K+
- ACTH
- decreased BP detected by stretch receptors in atria

to release aldosterone

aldosterone diffuses across cell membrane and binds to transcription factors in the nucleus

aldosterone activates transcription factor and stimulates transcription of genes for Na+ transporters

new transporters are made in the ER and transported to cell membrane via vesicles

205
Q

describe the RAA (renin-angiotensin-aldosterone) pathway

A

juxtaglomerular cells secrete the enzyme renin

206
Q

What enzyme do juxtaglomerular cells secrete?

A

renin

207
Q

What 3 ways is renin secretion regulated?

A

baroreceptors
sympathetic neurons
macula densa

208
Q

How do baroreceptors in the juxtaglomerular cells regulate renin secretion?

A

they stimulate the release of renin when there’s low BP

209
Q

How do sympathetic neurons regulate renin secretion?

A

in the cardiovascular control center (medulla oblongota) stimulate secretion in response to low BP

210
Q

How do macula densa cells regulate renin secretion?

A

in the distal tubule, the macula densa release paracrine signal to stimulate juxtaglomerular cells to release renin when BP is low

211
Q

when is renin secreted?

A

when BP is low or GFR is low

212
Q

What happens after renin is released?

A

renin catalyzes the conversion of angiotensinogen (released by liver) to angiotensin I

angiotensin I is cleaved by angiotensin converting enzyme (ACE) on the endothelial cells of blood vessels into angiotensin II

213
Q

What happens when angiotensin II is produced?

A

release of aldosterone from adrenal cortex

release of vasopressin

vasoconstriction of arterioles

binds to GPCR

all of this brings BP back to normal rates

Animal Physiology (13 decks)

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