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Structure And Function Of Living Organisms > Urinary systems > Flashcards

Urinary systems Flashcards

1
Q

What separates intracellular and interstitial fluid

A

cell membrane

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2
Q

hat separates interstitial fluid and blood plasma

A

endothelial cells in the capillary wall

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3
Q

Why is pH effected when you try and regulate electrolyte balance

A

due to the movement of H+

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4
Q

What are the 2 components of extracellular fluid

A

interstitial fluid (found between cells in ordinary tissues) and blood plasma (part of the blood apart from the red blood cells and white blood cells).

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5
Q

How much of a 70kg human is water

A

60%

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6
Q

How much water does ICF and ECF contain

A

ICF - 2/3 of total
ECF - 1/3 total

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7
Q

how much of the total volume of ECF does the interstitial fluid account for

A

3/4

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8
Q

What causes the total water % to vary

A

the amount of adipose tissues (lipid rich cells) present because it has a low water content

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9
Q

how is osmotic equilibrium between ICF and ECF maintained

A

movement of water between the 2

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10
Q

what is the movement of water between IF and plasma

A

isosmotic - water moves freely

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11
Q

How can capillaries achieve filtration or reabsorption

A

if the correct hydrostatic and osmotic pressure is present to pass through their thin walls

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12
Q

osmotic pressure in human plasma

A

300 mOsm

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13
Q

difference in osmotic pressure between IF and plasma

A

plasma is 1.5 mOsm high than IF - does not disturb osmotic state

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14
Q

can water move freely between ECF and ICF

A

no - osmolarity inside and outside cell is different so transporter is needed

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15
Q

Concentration of surrounding in freshwater animals

A

surroundings have a low concentration of solutes - hyperosmotic

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16
Q

where are the major sites of ion and water exchanges

A

skin (sweat), respiratory system (dry and wet during breathing), digestive tract (water and fluid absorption) and excretory system (urine, faecal matter).

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17
Q

What is osmoregulation

A

the movement of water and solutes to maintain an isosmotic state

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18
Q

How do sponges and cnidarians carry out osmoregulation

A

process with the lack of a circulatory system as they are in direct contact with water (bulk-flow), hence becomes easier for them to regulate and exchange.

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19
Q

What does the wall of a sponge contain to help with osmoregulation

A

full of pores that propel water into the spongocoel and out through the osculum.

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20
Q

What is the outer covering of a freshwater fish called

A

an integument

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21
Q

Why does an integument cause issues for osmoregulation

A

integument is impermeable to water, therefore lack direct contact and exchange with the external environment

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22
Q

Environment of freshwater fish

A

environment low in salt ions, however it has a higher concentration of salts in its body, and thus hyperosmotic to the environment

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23
Q

What happens to the salts from the freshwater fish

A

eventually lost to environment and water enters, via gills

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24
Q

How much water do goldfish take in a day

A

up to 30g/day, which is essentially 1/3rd of it body weight

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25
Q

Why do fish need to expel water

A

because they take up a lot, too much can dilute blood and cause other problems so energy is spent to expel water, salts are lost as a consequence

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26
Q

How do freshwater fish take up salts

A

via active transport. The transporters that are in place take up Na+ and Cl- and loose bicarbonate and H+ (electroneutral), with the help of ATP.

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27
Q

What are porins

A

similar to ion channels but permit the passage of large molecules.

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28
Q

What are aquaporins

A

Aquaporins are water channels in the plasma membrane, each aquaporin molecule transport 3 billion water molecules/second.

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29
Q

What happens if a membrane lacks aquaporins

A

water crosses the membrane 5-50 times slower.

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30
Q

Physiological roles of aquaporins

A

urine formation, production of aqueous humor of the eye, secretion of tears and sweat.

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31
Q

What are the 2 types of aquaporins

A

transcellular (through the cell membrane) or paracellular (across different compartments).

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32
Q

How do cells control their volume

A

transporting solutes across the plasma membrane, causing changes in osmotic pressure that induce movement of water.

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33
Q

What is the epithelium of a hummingbird

A

of a single layer of cells bearing microvilli on the apical membrane.

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34
Q

What must dissolved sugar molecules (e.g., glucose and fructose) do

A

cross the epithelium from the intestinal lumen to the blood.

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35
Q

What is ingested preformed water

A

water where the sugar molecules have been dissolved in

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36
Q

When is metabolic water formed

A

when organic food molecules are aerobically catabolized (e.g., glucose oxidation).

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37
Q

How is water gained

A

eating, drinking and cells produce it

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38
Q

Air entering the nose

A

warmed and humidified by heat. The nasal passages are cooled by evaporative water loss, leading to a flow of cool air.

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39
Q

What happens during expiration

A

the air is cooled and leads to a loss of water, wetting the nasal passage.

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40
Q

How else can water be excreted

A

through the faecal route, food is ingested that contains preformed water, and is excreted through this route.

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41
Q

How are desert kangaroo rats adapted to conserve water

A

More concentrated urea, less water loss and drier faeces

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42
Q

Lab rats v desert kangaroo rats experiment

A

where these rats were given 0 preformed water and they were given barley grain. They made metabolic water to survive. Desert kangaroo rats had a net gain of metabolic water compared to the lab rats.

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43
Q

What is osmotic regulation of blood plasma

A

is the regulation of osmotic pressure of an organism’s body fluids, detected by specialized receptors to maintain homeostasis of the organism’s water content

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44
Q

What is ionic regulation of blood plasma

A

Maintenance of the concentration of various ions in the bod fluids relative to one another. The urinary system plays a key role in this process.

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45
Q

What is volume regulation of blood plasma

A

Cell volume regulation is an important homeostatic function, defining not only cell shape but balance between the ICF and ECF.

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46
Q

What do obligatory responses cover

A

responses of an animal to factors that are beyond their physiological control (physical factors)

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47
Q

What are related responses

A

physiologically controlled and required for maintaining the internal homeostasis.

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48
Q

What is the linear line on a blood osmotic pressure v ambient osmotic pressure graph

A

isosmotic line

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49
Q

How does an osmotic conformer and an osmotic regulator differ on a graph

A

A perfect regulatory won’t follow the trend of the isosmotic line. However, the osmotic conformer will follow the trend of the isosmotic line

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50
Q

Osmotic pressure of osmotic conformers

A

have the same osmotic pressure as the externa environment

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51
Q

Osmotic pressure of osmotic regulators

A

keep osmolarity constant regardless of changes in the external environment.

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52
Q

What is the disadvantage of osmotic conformers

A

the cells may not have the ideal solute concentration for metabolism.

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53
Q

What is the disadvantage of osmotic regulators

A

they utilize too much to keep the internal solute concentration constant.

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54
Q

How do animals display features of both an osmotic conformer and a regulator

A

the regulation is limited to ranges of external osmotic pressure

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55
Q

Example of an osmotic regulator

A

shrimp

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56
Q

example of an osmotic conformer

A

mussel

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57
Q

When do crabs regulate and conform

A

when FW animals face brackish waters, they regulate in FW but conform in SW.

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58
Q

What is the extracellular space in animals dominated by

A

Na+ and Cl-

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59
Q

What is the extracellular space in SW dominated by

A

Na+ and Cl-, followed by reduced levels of K+, Mg2+ and Ca2+.

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60
Q

What ions dominate ionconformers

A

high levels of Na+ and Cl- like in SW

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61
Q

Ions present in ionregulators

A

low levels of Na+ and Cl-

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62
Q

What do both SW and osmoconformers have

A

have the same osmolarity but different solute profile

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63
Q

What is hemolymph

A

the circulating fluid in an open circulatory system that flows through blood vessels

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64
Q

Hemolymph in FW crabs

A

crabs is hyperosmotic to the surrounding water. Osmosis allows water to move in which is eventually lost as urine

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65
Q

Stability of animals in open ocean

A

they live in environment that are uniform and stable in their water-salt composition

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66
Q

Salinity of water calculation

A

number of grams of dissolved inorganic matter in a Kg of water.

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67
Q

Salinity and osmotic pressure of SW

A

34g/Kg, and its osmotic pressure is nearly 1000 mOsm

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68
Q

Salinity and osmotic pressure of FW

A

salinity less than 0.5g/Kg, and has an osmotic pressure of 0.5-15 mOsm.

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69
Q

How is volume regulation a challenge for FW animals

A

because there is a constant influx of water into the organism due to an osmotic gradient.

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70
Q

How is osmotic regulation an issue for FW animals

A

The water that enters, dilutes the blood and reduced osmotic pressure within the ECF.

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71
Q

How is ion regulation an issue for FW animals

A

Due to excretion of excess water ions are constantly lost to the external environment

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72
Q

Where do FW fish reabsorb ions and why

A

in their kidneys because the uptake of ions from a highly concentrated solution requires a lot of energy

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73
Q

What are freshwater animals to their environment

A

hyperosmotic to environment - gain of water, loss of ions

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74
Q

In FW, what are the consequences of rapid water uptake

A

the faster water is lost by diffusion and the more energy that is spent to counteract this

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75
Q

Wat 3 factors determine the rate of exchange

A

permeability, surface area to volume ratio and magnitude of gradient.

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76
Q

How do FW counteract that large water intake

A

by excreting copious amounts of urine

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77
Q

What does the rate of water influx in FW resemble

A

the rate of urinary excretion - because urine production balances osmotic water gain

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78
Q

What is the urine of FW fish compared to their blood

A

is hypoosmotic (low concentrations of Na+ and Cl-) to their blood. This is defined as the U:P ratio (Urine to plasma).

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79
Q

What does a U:P of less than 1 mean

A

that the blood osmotic pressure is high due to lots of urine production.

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80
Q

What does a U:P of less than 1 for an ion mean

A

that the large amounts of urine production tend to raise plasma concentrations for that particular ion

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81
Q

Function of the kidneys in FW animals

A

solve the problem of volume regulation by excreting urine but aid in ionic and osmotic regulation by maintaining high osmotic pressures and an increased ion concentration in the blood

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82
Q

Function of gills

A

active not only in gas exchange but also in ion transport, excretion of nitrogenous wastes, and maintenance of acid-base balance.

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83
Q

What does the epithelium which separates the blood from external water consist of

A

mucous cells, pavement cells and chloride cells

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84
Q

What does the epithelium of the lamella consist of

A

pavement cells and mitochondria - suited for respiratory exchange

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85
Q

What does the epithelium covering the gills contain

A

chloride cells, mitochondria and enzymes that assist with salt transport.

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86
Q

How do FW fish replenish lost Na+ and Cl-

A

active transport

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87
Q

Where does active ion transport occur and what does it require

A

the gills. Needs ATP

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88
Q

How does Cl- enter the blood from the environment FW fish

A

The Cl- pump typically exchanges HCO3 for Cl- (electroneutral).

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89
Q

How does Na+ enter the blood from the environment - FW fish

A

The Na+ pump exchanges H+ (protons) for Na+ or Nh4 (ammonium ions).

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90
Q

How are HCO3 and H+ produced in FW fish for ion exchange

A

produced by anaerobic catabolism, being formed by metabolically formed CO2 and H2O.

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91
Q

How is Na+ homeostasis maintained in mammals

A

through Na+ reabsorption via a variety of Na+ transport proteins with mutually compensating functions, which are expressed in the nephrons.

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92
Q

How is Na+ homeostasis achieve in FW fish

A

through the skin gill ionocytes, namely Na+/H+ exchangers. Expressing H+ ATPase rich cells and Na+ and Cl- Co-transporters.

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93
Q

What is the challenge in marine animals

A

osmotic gradient is higher, water moves in the opposite direction to fresh water fish

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94
Q

Movement of water in marine fish

A

sea water has a high salt concentration, causing high salt influx, when salt is expelled the water is lost so try to reabsorb as much water to maintain ICF osmotic pressure

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95
Q

movement of substances with respect to gills

A

substances can move in and out as they are permeable to water

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96
Q

How have organisms that live on land adapted to secrete salt

A

have glands e.g., sea birds have them in nasal passages

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97
Q

How have dogfish adapted

A

has a low conc of Na+ and Cl-, but urea and TMAO increase osmotic pressure causing influx of water from external environemnt. Salt lost through salt glands

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98
Q

Permeability of integuments

A

poorly penetrable to water

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99
Q

urine of marine fish

A

because they conserve water they form isosmotic urine

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100
Q

Role of kidneys in marine fish

A

get rid of excess salt

101
Q

What are stenohaline animals

A

tolerate a narrow range of salt concentration

102
Q

What are euryhaline animals

A

tolerate wide variation in osmolarities

103
Q

What are the functions of the urinary system

A
  1. Removal of waste products (produced by cellular metabolism)
  2. Regulation of volume and solute concentration of blood plasma, blood volume; pH
  3. Elimination of waste products into the environment
104
Q

Kidney function

A

urinary production, excretion and regulation

105
Q

Ureter function

A

urine transfer to bladder

106
Q

bladder function

A

urine storage, elimination

107
Q

urethra function

A

urine release, elimination

108
Q

Location of the kidneys

A

on either side of the middle on the posterior wall of the abdomen. Lie behind the parietal peritoneum = retroperitoneal. Surrounded by fat (adipose tissue - protection)

109
Q

Cortex of the kidney function

A

corticosteroids (aldosterone), sodium and water retention, increase blood pressure and volume.

110
Q

Medulla of the kidney function

A

adrenaline and noradrenaline. Fight or flight response

111
Q

Left v right kidney function

A

(T12-L3): the left kidney is located slightly higher than the right because of the liver (L =lumbar, T = thoracic)

112
Q

What protects the kidney

A

fat, fascia, ribs 11 and 12

113
Q

When does Floating kidney (wandering kidney or nephroptosis) occur

A

when collagen fibres and suspensory fibres that are holding kidney are damaged.

114
Q

What makes up the renal capsule and renal fascia

A

collagen

115
Q

Shape of kidney

A

Indented ovoid – bean shaped

116
Q

renal hilum structures (enter and exit site)

A

renal vein, renal artery and renal pelvis

117
Q

Blood supply of kidneys

A

20-25% of cardiac out put

118
Q

How are kidneys indented

A

small lobes have come together

119
Q

What is an anomolie of kidneys

A

horseshoe kidney

120
Q

Structures of the kidney

A

renal cortex, renal medulla, renal papilla, renal pyramids, renal column, renal artery/vein, renal pelvis

121
Q

What does the renal lobe contain

A

the nephron

122
Q

Structures of nephron in the cortex

A

Bowman’s capsule, proximal convoluted tubule, distal convoluted tubule

123
Q

Structures of nephron in the medulla

A

loop of henle, collecting duct, pelvis

124
Q

What are the ureters

A

hollow muscular tubes, propel urine from the kidneys to the bladder

125
Q

length of the ureters

A

25-30cm

126
Q

Location of ureters

A

in both abdomen and pelvis

127
Q

Anomolie of ureter

A

duplex ureter (bifid ureter) - 1 in 125 people

128
Q

How do ureters enter the bladder

A

obliquely

129
Q

Ureter when the bladder is full

A

prevents backflow of urine into the ureters. Compression closes off the ureters acting as a valve

130
Q

Apex of the bladder

A

points towards the public symphysis

131
Q

Fundus of the bladder

A

opposite the apex and formed by the posterior wall

132
Q

Capcity of the bladder

A

0.75 l

133
Q

Female urethra length

A

4-5cm

134
Q

Location of the female urethra

A

Passes through the pelvic floor and opens anterior to the vagina

135
Q

Male urethra length

A

20cm

136
Q

Male urethra shape

A

S-shaped

137
Q

Parts of the male urethra

A

pre-prostatic, prostatic, membranous, penile

138
Q

Male urethra flow

A

Urine flows down through catheter to empty the baldder of urine

139
Q

Internal male urethra sphincter

A

junction between the bladder urethra

140
Q

Male internal urethra sphincter function

A

prevents reflux of semen into the bladder

141
Q

Location of male urethral sphincter

A

inferior to the prostate

142
Q

Female internal urethral sphincter

A

Junction between the baldder and urethra ‘Debate’

143
Q

Female external urethral sphincter

A

immediately inferior to the internal urethra sphincter

144
Q

Function of mammalian kidney

A

regulate the composition of body fluids (osmotic balance), excretion of waste in the form of urine, pH balance, hormone production (kidneys produce a hormone that stimulate RBC production) and regulate blood pressure.

145
Q

What processes contribute to the formation of urine

A

filtration, reabsorption, secretion and excretion

146
Q

What happens to the water/solutes once they have left the arterioles into the kidney

A

they enter lumen of bowmans capsule forming an ultrafiltrate

147
Q

What are the renal tubes lined with

A

cells so ions and water can freely move, passing through this cell layer (reabsorbed)

148
Q

Where are certain types of molecules secreted from and to

A

From the IF into the proximal tubule to be excreted as waste

149
Q

What does the glomerular filtrate contain

A

contains all the constituents of the blood except blood cells and proteins.

150
Q

What % of water and solutes are removed from the plasma

A

15-25%

151
Q

At what rate is the filtrate produced

A

180L/day

152
Q

Function of afferent arteriole

A

transports blood towards the glomerulus

153
Q

Function of efferent arteriole

A

transports the blood away from the glomerulus

154
Q

Network of capillaries inside the glomerulus

A

with thin walls allowing easy movement of substances. These loops are also referred to as glomerular tufts. The key here is the constant blood supply.

155
Q

Layers of the glomerulus

A

Endothelial cells basement membrane and the podocytes. This is the filtration barrier.

156
Q

Function of filtration barrier

A

keep blood and protein into the body and allow the passage of small molecules into the urine

157
Q

What are the podocytes

A

modified epithelial cells that provide structural support

158
Q

Glomerulus size selectivity

A

molecules less than 1.8 nm can be easily filtered (water, sodium, insulin and glucose). Molecules more that 3.6 nm are not filtered (haemoglobin).

159
Q

Glomerulus charge selectivity

A

negatively charged molecules cannot pass that easily, as all the three layers shown above contain negatively charged glycoproteins.

160
Q

What does filtration of the blood depend on

A

hydrostatic and oncotic pressure

161
Q

What is hydrostatic pressure

A

is the pressure that the fluid exerts on the walls of the compartment, either the walls of the capillary or the Bowmans capsule (pushing force).

162
Q

What is oncotic presssure

A

is the pressure exerted by the plasma protein on the walls of the compartment in which they are contained (pulling force).

163
Q

What is the clearance

A

The amount of fluid cleared completely of a certain substance.

164
Q

What happens if the hydrostatic pressure is greater in the capillary than the Bowman’s capsule

A

fluid is pushed out

165
Q

Why does the blood have a greater osmotic pressure than the Bowman’s capsule

A

due to the presence of proteins

166
Q

Oncotic pressure present in capillaries

A
  • The oncotic pressure present in the capillaries tend to pull fluids back in. The balance between the forces influences rate and direction of fluid movement.
167
Q

What is the net filtration pressure

A

Pressure favouring filtration minus the pressures opposing filtration

168
Q

What is the net hydrostatic pressure

A

the glomerular capillary pressure (hydrostatic pressure within the capillaries) minus the Intracapsular pressure (hydrostatic pressure within the lumen of the Bowmans capsule).

169
Q

net filtration pressure formula

A

net hydrostatic pressure minus the colloid osmotic pressure (oncotic pressure). This will give you the net filtration pressure.

170
Q

Why do we calculate the glomerular filtration pressure

A

to identify if an individual is suffering from kidney problems.

171
Q

What is the juxtaglomerular apparatus (JGA)

A

a specialized region which is significant for sensing the blood pressure/flow into the kidney and producing hormones such as renin.

172
Q

What is renin

A

is a hormone, significant in blood pressure regulation and fluid balance.

173
Q

What comes into contact at the JGA

A

is a region where the afferent arterioles come into contact with the distal tubule.

174
Q

What is present on the outside of the afferent arterioles

A

JG cells that can sense blood pressure.

175
Q

What happens at the point of contact with the distal tubule

A

modified cells in the distal tubule, Macula densa cells sense changes in flow and an Na+ concentration of the intertubular fluid.

176
Q

What happens when systemic blood pressure decreases

A

a decreased stretch of the JG cells which release renin, renin will increase blood pressure back to normal.

177
Q

What happens when the filtrate has a decreased flow rate

A

the macula densa cells sense this, leading to vasodilation of the afferent arteriole and renin secretion by the JG cells. Renin will return flowrate back to normal

178
Q

What is the purpose of the JGA

A

connection between, blood pressure, osmolarity, blood flow and Na+ concentration

179
Q

Where does the filtrate go after the Bowman’s capsule

A

proximal tubule

180
Q

function of the proximal tubule

A

specialized for transport and is the area where most reabsorption occurs.

181
Q

How are epithelial cells of the tubule unique

A

are not very permeable to lots of substances -> they have lots of transport mechanisms on either side of the cell to help regulate the movement of ions.

182
Q

Function of the tight junctions in the tubule epithelial cells

A

prevent paracellular transport, and contain a certain polarity allowing certain substances to move across, such as proteins and pharmaceutical agents.

183
Q

What do the epithelia in the PT contain for reabsorption

A

epithelia have microvilli, lots of mitochondria and a large surface area.

184
Q

How much of the filtered fluid does the PT reabsorb

A

80%

185
Q

How much of the filtered fluid does the loop of henle reclaim

A

5-10%

186
Q

Loop of henle function

A

water conservation

187
Q

What does reabsorption maintain

A

fluid and electrolyte balance in the system.

188
Q

How else is urine modified

A

through secretion

189
Q

what does secretion use

A

transporters found in the epithelial cells that line the lumen of the PT.

190
Q

What substances move into the PT from the blood

A

H+, K+, toxins and pharmaceutical drugs. Requires energy

191
Q

osmolarity of the fluid at the end of the PT

A

300 mOsm - isosmotic to the IF and plasma

192
Q

How thick is the wall of the tubule

A

one cell layer thick

193
Q

How are the epithelial cells in the tubule specialised

A

for transport, bearing a dense pile of microvilli on their luminal (apical) surfaces.

194
Q

How are epithelial cells tied together

A

by leaky junctions

195
Q

What occurs in all sections of the kidney tubule

A

, Na+ diffuses into the epithelial cells from the tubular fluid because there is an electrochemical gradient favouring this movement.

196
Q

In the early PT how does most Na+ entry occur

A

occurs by means of co-transporters that bring about secondary active transport of glucose and amino acids because the fluid is rich in glucose and amino acids

197
Q

Permeability of the descending limb

A

is very permeable to water because it doesn’t have tight junctions.

198
Q

Epithelium cells of the descending limb

A

have no active transport of solutes, highly permeable to water and impermeable to ion and urea.

199
Q

Ascending limb characteristics

A

, impermeable to water, permeable to ions and impermeable to urea. The thick segment of the AL has active transport of ions.

200
Q

primary urine bicarbonate and proton concentration

A

urine concentration of bicarbonate is high but concentration of protons is low

201
Q

Reabsorption of bicarbonate ions

A

around 80% of bicarbonate takes place in the proximal convoluting tubule and continues in downstream sections of the nephron

202
Q

Movement of protons

A

moved in the opposite direction to bicarbonate ions, causing acidification of the intertubular fluid

203
Q

Where does the final tuning of urine acidification occur

A

distal tubule and the collecting duct

204
Q

What are alpha intercalated cells

A

acid-secreting

205
Q

What are beta intercalated cells

A

base-secreting

206
Q

What do alpha and beta secreted cells possess

A

various sensors for bicarbonate, CO2 or proton concentration

207
Q

What do signals from the bicarbonate, CO2 and proton concentration sensors do

A

modulate expression, abundance in the plasma membrane or activity of transporters, pumps and channels in these cells. These processes are also under hormonal control (aldosterone, angiotensin II, etc.)

208
Q

Purpose of counter current multiplication

A

to create concentrated urine with the loop of Henle (LOH).

209
Q

Water reabsorption in the decending limb

A

the osmolarity (concentration of Na+) in the IF is high, water will move out from the DL into the IF, equilibrating the osmotic pressure.

210
Q

Changes in the Na+ concentration in the descending limb

A

increases as water moves out

211
Q

How did Na+ enter the IF

A

active transport

212
Q

Movement of Na+ in the ascending limb

A

original high Na+ conc, Na+ pumped into IF

213
Q

What is the osmolarity difference between IF and tubular fluid

A

200mOsm

214
Q

Why is Na+ transported into the IF from the ascending limb

A
  • Therefore Na+ is transported out from the AL into the IF creating a 200 mOsm difference. Due to the transport of Na+, the IF has an osmolarity of 400 mOsm and the filtrate in the AL has an osmolarity of 200 mOsm (200 mOsm difference).
215
Q

Water movement out of the DL

A

Water will continuously move out of the DL until it equilibrates with the IF, this means that the osmolarity in the DL and IF will be the same (400 mOsm).

216
Q

Why does the DL and IF equilibriate

A

because when water moves out into the IF, the filtrate in the DL gets more concentrated (increased osmolarity).

217
Q

Effect on osmolarity of water reabsorption

A

no change in the IF

218
Q

Why does the movement from the DL to the AL take place

A

due to new isosmotic filtrate entering the DL from the PT.

219
Q

osmolarity of the filtrate in the DL and bottom of AL

A

is isosmotic to the IF, therefore there is no concentration gradient to transport Na+ passively so Na+ is transported to IF

220
Q

What happens to the Na+ present at the top of the AL

A

be transported into the IF, to create that 200 mOsm difference, and whatever is remaining will get transported into the collecting duct (CD).

221
Q

Osmolarity in the medulla

A

The osmolarity increases the deeper you move into the medulla, and this is because of counter current multiplication.

222
Q

Why is it called counter current multiplication

A

Counter current because the filtrate moves in opposite directions, and multiplication because of the flow and mechanisms involved to concentrate urine (gradient is multiplied).

223
Q

How does counter current multiplication aid water reabsorption in the collecting ducts

A

the IF will have an increased Na+ surrounding the CD, and thus water will move out into the IF due to a concentration gradient.

224
Q

How is the LOH show an increase in osmolarity

A

by the observing the size difference between juxtamedullary nephrons (JMN) and cortical. , where desert animals have a longer LOH than a lab rats, as evolution within than environment has favoured water conservation leading to more water reabsorption

225
Q

What are vasa recta

A

are specialized capillaries found around the JMN

226
Q

What do the capillaries in the vasa recta specialize in

A

creating this hyperosmotic environment to draw water out.

227
Q

Descending vasa recta

A

Blood coming down from the cortex into the medulla is in contact with increased osmolarity IF. The Na+ will diffuse from the surrounding IF into the vasa recta.

228
Q

Ascending vasa recta

A

concentrated blood (increased osmolarity) will move towards the AL and will lose that concentrated Na+ to the diluted IF

229
Q

Descending vasa recta - H2O

A

Dilute blood flowing from the cortex into the medulla will lose water to the concentrated IF (increased osmolarity).

230
Q

Ascending vasa recta - H2O

A

Concentrated blood flowing towards the AL will gain water from the IF due to its increased osmolarity in the capillary

231
Q

What does the increased concentration gradient across the nephron create

A

there is constant water reabsorption, which creates concentrated urine. benefits the CD, which promotes water reabsorption from the CD.

232
Q

Movement of urea

A

move freely across the membranes. Urea can move across the AL, CD and the IF. Due to this movement and the constant influx of newly filtered urea, creates a concentration gradient, promoting water reabsorption from the DL.

233
Q

Transport proteins in the collecting ducts

A

. UT-A1 and UT-A3, expressed by epithelial cells of the CD, aid in transport of urea from the CD to the IF.

234
Q

Affect of vasopressin

A

upregulates expression of UT-A1 and UT-A3, increasing the rate of urea transport.

235
Q

What does increased osmolarity detected by osmoreceptors cause

A

release of vasopressin

236
Q

Angiotensin II effects

A

acts on receptors in the hypothalamus, causing vasopressin release

237
Q

How does a decreased water content in the blood effect the heart

A

reduced venus return detected by baroreceptors leading to vasopressin release

238
Q

Mechanism of vasopressin

A

Vasopressin upregulates translocation of aquaporin (AQP-2) receptors on the apical side of the plasma membrane in the distal convoluted tubule and CD. On the basolateral side of the membrane, you always have presence of aquaporin-3 and 4. When osmolarity in the IF increases (decrease in water content), Vasopressin is released and upregulates translocation of AQP-2, leading to increased water reabsorption in the IF.

239
Q

What is renin

A

an enzyme secreted by JGA cells

240
Q

What cells are present when the Bowmans capsule meets the distal convoluted tubule

A

specialized cells e.g., JGA cells and macula densa

241
Q

Renin secretion - baroreceptor mechanisms

A

Baroreceptors can detect a change in pressure within your afferent arterioles. If the bp in the afferent arterioles decrease, the baroreceptors will send a signal to the JGA cells to release renin. Renin will carry out its function an increase blood pressure

242
Q

Renin secretion - sympathetic nervous system

A

There are certain nerves that stimulate renin release during sympathetic activity (fight/flight). Metabolism increases and hence renin is released.

243
Q

What do macula densa cells do

A

sense Na+ in the distal convoluted tubule

244
Q

What does increased Na+ mean about blood pressure

A

increased blood pressure

245
Q

Decreased Na+ - macula densa cells

A

Macula densa cells will stimulate the JGA cells to release renin, which will increase your blood pressure. The increase in blood pressure, will increase your GFR and net filtration, leading to an increase in Na+ reabsorption.

246
Q

How does renin work

A

Renin is an enzyme, which works on a substrate known as angiotensinogen, produced by the liver. Angiotensinogen gets into your blood stream. Renin breaks down angiotensinogen to angiotensin 1 which is converted by an enzyme (angiotensin converting enzyme) to angiotensin 2.

247
Q

What does angiotensin stimulate

A

aldosterone

248
Q

What does aldosterone do

A

Aldosterone increases sodium reabsorption and potassium secretion in the distal convoluting tubule and the collecting duct.Intensified sodium reabsorption followed by Intensified water reabsorption, which increases the volume of blood and consequently, further raise of blood pressure.

Structure And Function Of Living Organisms (10 decks)

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