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biology a level > 5.2 > Flashcards

5.2 Flashcards

1
Q

what is excretion

A

the removal of metabolic waste from the body

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2
Q

what is metabolic waste

A

defined as a substance that is produced in excess as a result of metabolic processes in cells

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3
Q

what is egestion

A

the process of removing undigested food

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4
Q

why is it important that metabolic waste substances are removed

A

need to be removed before they become too toxic

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5
Q

what does the lungs remove

A

co2

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6
Q

what does the liver remove

A

urea, hydrogen peroxide, detoxification of drugs and alcohol

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7
Q

what does the kidneys remove

A

urea

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8
Q

what does the skin remove

A

urea, uric acid and ammonia

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9
Q

what substance is excreted in the lungs, and why is it important for homeostasis

A

-removes CO2
-important for homeostasis because if CO2 builds up, the pH of tissue fluid changes which will disrupt the action of enzymes and other proteins

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10
Q

what substances are excreted in the liver, and why is it important for homeostasis

A

-removes excess amino acids ( converted to urea by removing the nitrogen containing parts with co2[demination]), urea, hydrogen peroxide, harmful substances, alcohol, drugs, unwanted hormones
-important for homeostasis because excess amino acids could change pH of cells as they are acids

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11
Q

what substance is excreted in the kidneys, and why is it important for homeostasis

A

-removes urea (removed as urine)
-important for homeostasis because it maintains water pot~~

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12
Q

what substance is excreted in the skin, and why is it important for homeostasis

A

-removes uric acid (produced from the breakdown of purines), urea and ammonia
-important for homeostasis because body temp needs to be maintained (sweating) and water pot needs to be maintained

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13
Q

what things act in the blood as buffers to resist change in pH

A

-proteins (such as haemoglobin)

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14
Q

what is respiratory acidosis and what is it caused by

A

-occurs when blood pH drops below 7.35 leading to a rapid heart rate and changes in blood pressure.
-respiratory acidosis can be caused by diseases or conditions that affect the lungs itself such as emphysema, asthma etc… Blockage of the airway can also cause it

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15
Q

amino acids contain almost as much energy as carbohydrates thus wasteful to simply excrete amino acids, what happens instead?

A

instead they are transported to the liver and the potentially toxic amino group is removed (demination)

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16
Q

in the body the amino group initially forms________, what is this then converted to and what does this lead to

A

in the body the amino group initially forms ammonia (this is very soluble and highly toxic), this is then converted to a less soluble and less toxic compound called urea, which can be transported to the kidneys for excretion

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17
Q

In amino acids, what can the remaining keto acid be used directly in?

A

can be used directly in respiration to release its energy or may be converted to a carbohydrate or fat for storage

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18
Q

state the equation of deamination

A

amino acid + oxygen -> keto acid + ammonia

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19
Q

how is urea formed ( equation)

A

ammonia + carbon dioxide -> urea + water

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20
Q

what are liver cells called

A

hepatocytes

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21
Q

the liver has many metabolic roles and is important in homeostasis, what does this mean it needs

A

a good supply of blood is needed

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22
Q

the internal structure of the liver ensures that as much blood as possible flows past as many liver cells as possible, what does this enable the liver to do

A

enables the liver cells to remove excess or unwanted substances from the blood to ensure concentrations are maintained

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23
Q

what two sources supply the liver with blood

A

-the hepatic artery
-the hepatic portal vein

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24
Q

state stuff about the hepatic artery which supplies blood to the liver
and why is the hepatic artery important to the liver

A

oxygenated blood from the heart travels from the aorta via the hepatic artery into the liver. this supplies oxygen which is essential for aerobic respiration. It is important that the liver gas a good supply of oxygen for aerobic respiration because the liver cells are very active as they carry out many metabolic processes, many of these processes require energy in the form of ATP

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25
Q

state stuff about the hepatic portal vein which supplies blood to the liver

A

deoxygenated blood from the digestive system enters the liver via the hepatic portal vein. This blood is rich in the products of digestion. The concentrations of various substances will be uncontrolled as they have just entered the body from the products of digestion in the intestines. The blood may also contain toxic compounds that have been absorbed from the intestine. It is important that such substances do not continue to circulate around the body before their concentrations have been adjusted

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26
Q

what does blood leave via in the liver and what is it connected to

A

blood leaves via the hepatic vein, the hepatic vein re-joins the vena cava and the blood returns to the body’s normal circulation

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27
Q

the 4th vessel connected to the liver is the bile duct, what is bile and what does the bile duct do?

A

-bile is a secretion from the liver which has functions in digestion and excretion. The bile duct carries bile from the liver to the fall bladder, where it is stored until required to aid the digestion of fats in the small intestine.

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28
Q

what does bile contain

A

some excretory products such as bile pigments like bilirubin, which will leave the body with the faeces.

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29
Q

how are the cells, blood vessels and chambers inside the liver arranged

A

they are arranged to ensure greatest possible contact between blood and the liver cells. The liver is divided into lobes which are further divided into lobules. The lobules are cylindrical

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30
Q

label the liver

A

pic

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31
Q

lable the liver cells

A

pic

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32
Q

label the cylindrical lobule

A

pic

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33
Q

what is the difference between the inter-lobular vessels and the intra-lobular vessels

A

inter lobular vessels are smaller branches of the hepatic portal vein and hepatic artery which run along between lobules.
intra lobular vessels are smaller branches of the hepatic vein.

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34
Q

what happens to to the vessels once the hepatic artery and hepatic portal vein enter the liver

A

they split into smaller vessels and run parallel to the lobules ( inter-lobular vessels)

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35
Q

what is a sinusoid and what’s its function

A

a special chamber that carries a mix of the blood from the intra and inter lobular vessels

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36
Q

what are Kupffer cells and what are their function

A

they are specialized macrophages that move about within the sinusoids. Their primary functions to breakdown and recycle old red blood cells

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37
Q

Kupffer cells break down old red blood cells, what is one of the products of hemoglobin breakdown?

A

hemoglobin breakdown forms bilirubin which is one of the bile pigments excreted as part of the bile.

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38
Q

bile is made in the _______ and released into the _______

A

1= liver
2= bile canaliculi

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39
Q

bile canaliculi join to form the ______

A

bile duct

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40
Q

what does the bile duct do

A

transports bile to the gall bladder

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41
Q

what has happened to the blood once it has reached the end of the sinusoid

A

the concentrations of many of its components have been modified and regulated

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42
Q

what is at the center of each lobule

A

at the center of each lobule is a branch of the hepatic vein known as the intra-lobular vessel.

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43
Q

what vessel do sinusoids empty into

A

the intra-lobular vessel

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44
Q

what joins together to form the hepatic vein and what does the hepatic vein do?

A

the hepatic vein is formed from branches of the hepatic vein from different lobules joining together.
-the hepatic vein drains blood from the liver

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45
Q

are liver cells specialized?

A

No- they are relatively unspecialized

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46
Q

state the shape of liver cells (hepatocytes) and what is on their surface

A

they have a simple cuboidal shape with many microvilli on their surface

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47
Q

liver cells have many metabolic functions, name some

A

-protein synthesis
-transformation and storage of carbohydrates
-synthesis of cholesterol and bile salts
-detoxification

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48
Q

liver cells have many metabolic functions, due to this, describe the nature of their cytoplasm

A

their cytoplasm must be very dense and is specialized in the numbers of organelles that it contains

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49
Q

the liver is metabolically very active, what functions does it carry out

A

-control of blood glucose levels, amino acid levels, lipid levels
-synthesis of bile, plasma proteins, cholesterol
-synthesis of red blood cells in the fetus
-storage of vitamins A, D and B12, iron, glycogen
-detoxification of alcohol, drugs
-breakdown of hormones
destruction of red blood cells

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50
Q

how does the liver store sugar (explain)

A

in the form of glycogen, the glycogen forms granules in the cytoplasm of hepatocytes

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51
Q

what substances should be detoxified in the liver

A

hydrogen peroxide or alcohol

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52
Q

what are the methods to render toxins as harmless in the liver

A

toxins are rendered harmless by oxidation, reduction, methylation or by combination with another molecule

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53
Q

what molecule allows liver cells to render toxins harmless

A

a great array of enzymes

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54
Q

what are the two enzymes in the liver that render toxins harmless

A
  • catalase
    -cytochrome P450
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55
Q

describe the role of catalase in the liver

A

converts hydrogen peroxide to oxygen and water. catalase has a particularly high turnover rate

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56
Q

describe the role of cytochrome P450 in the liver

A

its a group of enzymes used to breakdown drugs including cocaine and various medicinal drugs . The cytochromes are also used in other metabolic reactions such as electron transport during respiration. Their role in metabolising drugs can interfere with other metabolic roles and cause the unwanted side effects of some medicinal drugs.

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57
Q

order these from smallest to largest :
lobe, liver, lobule, hepatocyte

A

hepatocyte, lobule, lobe, liver

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58
Q

what are the two vessels supplying the liver and what do they carry

A

-hepatic portal vein- contains waste products- deoxygenated- contains products of digestion and toxins that have been absorbed by the intestine
-hepatic artery- comes from the aorta, the blood is oxygenated (from heart)

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59
Q

what’s the vein that takes blood away from the liver

A

the hepatic vein

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60
Q

what’s the 4th vessel connected to the liver

A

the bile duct

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61
Q

which enzyme converts ethanol into ethanal

A

ethanol dehydrogenase

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62
Q

which enzyme converts ethenal into ethanoic acid

A

ethenal deydrogenase

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63
Q

what else is made when converting ethanol to ethenal and ethanoic acid, what is this substance important for

A

forms reduced NAD (a coenzyme for respiration)

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64
Q

what else is made when converting ethanol to ethanol and ethanoic acid, what is this substance important for

A

forms reduced NAD (a coenzyme for respiration)

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65
Q

what is the last substance that is made in the detoxification of alcohol?

A

Acetyl coenzyme A

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66
Q

The last substance that is made in the detoxification of alcohol is acetyl coenzyme A, what is this used for

A

for respiration

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67
Q

how is reduced NAD formed

A

when 2H combines with NAD

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68
Q

NAD is used to break down fatty acids, if the liver has to detoxify too much alcohol, NAD is used up. what might happen to the fatty acids if the liver has insufficient NAD to deal with them? What might happen to the size of the liver as a result of this? What could this lead to?

A

fatty acids are converted to lipids and stored in hepatocytes as fat = enlarged liver (known as ‘fatty liver’)= hepatitis or cirrhosis

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69
Q

along with forming reduced NAD, what is NAD also required for

A

also required to oxidase and breakdown fatty acids for use in respiration.

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70
Q

what happens if the liver has to detoxify too much alcohol

A

it uses up stores of NAD and has insufficient left to deal with fatty acids

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71
Q

why cant excess amino acids be stored

A

becasue amino groups make them toxic

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72
Q

why would it be wasteful to excrete whole molecules of amino acids

A

because they contain a lot of energy

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73
Q

what treatments do excess amino acids undergo in the liver to remove and excrete the amino acid component

A

deamination followed by the ornithine cycle

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74
Q

describe the process of demination

A

-removal of amino group to produce ammonia
- a keto acid is also produced which can enter respiration directly to release its energy.
oxygen is added to the amino acid to produce keto acid and ammonia

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75
Q

describe the properties of ammonia

A

very soluble and highly toxic (this means it must be converted to a less toxic form very quickly)

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76
Q

why should urea be produced from ammonia instead of ammonia staying present

A

urea is both less soluble and and less toxic

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77
Q

once urea is formed from the ornithine cycle, where does it travel to

A

it can be passed back into the blood and transported around the body to the kidneys.

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78
Q

once urea reaches the kidneys, what happens to it?

A

at the kidneys, the urea is filtered out of the blood and concentrated in the urine. Urine can be stored in the bladder until released

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79
Q

what is the reaction summary in the ornithine cycle

A

ammonia + carbon dioxide –> urea + water

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80
Q

what is the ornithine cycle responsible for

A

for removing ammonia before it builds up

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81
Q

ornithine cycle:
what is ammonia combined with to make it less toxic, what does this produce

A

its combined with co2 and Ornithine to produce water and Citulline

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82
Q

ornithine cycle:
what is Citrulline then combined with

A

combined with nh3, producing h20 and Arginine

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83
Q

ornithine cycle: what occurs after the formation of Arginine

A

h20 is added, Arginine is then reconverted to Ornithine by the removal of urea ( urea is produced)

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84
Q

ornithine cycle:
once urea is produced in the liver, what does it do

A

the urea is transported to the kidneys by the blood in the hepatic vein. It is filtered out of the blood by the kidney’s and safely stored in the bladder.

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85
Q

what’s bigger, the hepatic portal vein or the hepatic artery?

A

the branch of hepatic portal vein

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86
Q

where is the kidney positioned in the body

A

each side of the spine just below the rib

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87
Q

how does urine pass from the kidney to the bladder

A

it passes out of the kidney down the ureter to the bladder where it can be stored

88
Q

the role of the kidneys is ______

A

excretion

89
Q

how is urine produced

A

when the kidneys remove waste products from the blood, urine is produced

90
Q

structure: what is the outer kidney surrounded by

A

a tough capsule

91
Q

in a longitudinal section what three regions of the kidney are present?

A

-the outer region (the cortex)
-the inner region (the medulla)
-the center which is the pelvis leading to the ureter.

92
Q

what does the bulk of the kidney consist of

A

consists of tiny tubules called nephrons

93
Q

where does each nephron start

A

each nephron starts in the cortex at the Bowman’s capsule

94
Q

where is the remainder of the nephron and what does it look like

A

the remainder of the nephron is a coiled tubule that passes through the cortex, forms a loop down the medulla and back to the cortex, before joining a collecting duct that passes back down into the medulla.

95
Q

the cortex is a mass of ______ and ______

A

tubules and glomeruli

96
Q

what does the renal artery split to form

A

splits to form many afferent arterioles

97
Q

what do the afferent arterioles lead to

A

lead to a knot of capillaries called the glomerulus

98
Q

where does the blood from the glomerulus continue to

A

continues to an efferent arteriole which carries the blood to more capillaries surrounding the rest of the tubule, these capillaries eventually flow together to form the renal vein

99
Q

what is each glomerulus surrounded by

A

by the Bowman’s capsule

100
Q

by what means is fluid from the blood is pushed into the Bowman’s capsule

A

via ultrafiltration

101
Q

what is the barrier called between the blood in the capillary and the lumen of the Bowman’s capsule

A

the filter

102
Q

what are the three layers of the filter between the blood in the capillary and the lumen of the Bowman’s capsule to enable ultrafiltration

A

-The endothelium of the capillary
-The basement membrane
-The epithelial cells of the Bowman’s capsule

103
Q

filtering of the liver: describe the endothelium of the capillary

A

there are narrow gaps between the cells of the endothelium and the capillary wall. The cells of the endothelium also contain pores, called fenestrations. The gaps allow blood plasma and the substances dissolved in it to pass out of the capillary.

104
Q

filtering of the liver: describe the basement membrane

A

membrane consists of a fine mesh of collagen fibers and glycoproteins. This mesh acts as a filter to prevent the passage of molecules with a relative molecular mass of around 69000. This means most proteins and all red blood cells are held in the capillaries of the glomerulus

105
Q

filtering of the liver: describe the epithelial cells of the bowman’s capsule

A

these are cells called podocytes have a specialized shape- they have many finger like projections, called major processes. Fluid from the blood in the glomerulus can pass between these cells into the lumen of the bowman’s capsule.

106
Q

describe major processes and what they allow for

A

on each major process is a minor process or foot processes that hold the cells away from the endothelium of the capillary. These projections ensure that there are gaps between cells

107
Q

the Bowman’s capsule leads to the rest of the tubule, which has three parts.

A

-proximal convoluted tubule
-loop of Henle
-distal convoluted tubule

108
Q

the fluid from many nephrons leads to what

A

the fluid from many nephrons enters the collecting ducts, which pass down through the medulla to the pelvis at the center of the kidney.

109
Q

what is ultrafiltration

A

filtration of the blood at a molecular level under pressure

110
Q

whats a nephron

A

the functional unit of the kidney- there are 1 million

111
Q

label the diagram

A
112
Q

what is ultrafiltration

A

filtering of the blood at the molecular level

113
Q

what is wider, the afferent arteriole or the efferent arteriole

A

the afferent arteriole is wider, so less of a pressure

114
Q

what has a higher pressure, the glomerulus or the pressure in the bowman’s capsule and what does this allow for

A

the glomerulus maintains a higher pressure, this allows for the pushing of fluid of the blood of the glomerulus into the bowman’s capsule

115
Q

what 5 substances does the blood plasma contain

A

water
amino acids
glucose
urea
inorganic mineral ions

116
Q

what is filtered out of the blood into the glomerular filtrate and why?

A

amino acids, urea, mineral ions, glucose, water* and small proteins (less than 69000 Da) because they are small enough

117
Q

what isn’t filtered out of the blood into the glomerular filtrate and why?

A

proteins larger than 69000 Da and red blood cells as they are too large

118
Q

what two substances are found in the glomerular filtrate but not the urine and why

A

amino acids and glucose because they are re-absorbed. some mineral ions are also re-absorbed

119
Q

why dos the concentration of urea in the urine higher than the concentration in the glomerular filtrate?

A

the conc. of urine increases due to the reabsorption of water

120
Q

there are many blood cells and proteins in the capillaries, what does this mean for the water potential. What does this ensure

A

the presence of proteins means the blood has a very low water potential, this ensures that fluid is retained in the blood and helps re-absorb water at a later stage

121
Q

as the fluid from the bowman’s capsule passes along the nephron tubule, what is its composition altered by?

A

by selective re-absorption

122
Q

state the selective re-absorption that occurs at the proximal convoluted tube

A

-All sugars, most minerals and some water is reabsorbed here.

123
Q

what is the tissue that lines the proximal convoluted tubule called

A

cuboidal epithelium

124
Q

the tissue that lines the proximal convoluted tubule is called the cuboidal epithelium, talk abt the cells here

A

the cells have a brush border which is a result of being highly folded which increases SA

125
Q

state the selective re-absorption that occurs at the descending limb of the loop of Henle

A

mineral ions are added here and water is removed. the water potential of the fluid is decreased

126
Q

state the selective re-absorption that occurs at the ascending limb of the loop of Henle

A

mineral ions are removed here. The water potential of the fluid is increased

127
Q

state the selective re-absorption that occurs at the collecting duct

A

more water is removed. The water potential of the fluid is decreased. The final product at the collecting duct is urine

128
Q

what does the process of selective reabsorption allow for urine to have

A

allows urine to have a low water potential ( has a high conc of solutes than blood and tissue fluid)

129
Q

what mechanisms does reabsorption involve

A

active transport
cotransport

130
Q

state specializations of the cell surface in contact with the tubule fluid to achieve this reabsorption

A

-its highly folded to form microvilli which increases SA for re-absorption
-contains special co-transporter proteins that transport amino acids r glucose with sodium ions from the tubule into the cell

131
Q

state specializations of the membrane in close contact with the capillaries and tissue fluid to achieve this reabsorption

A

highly folded to increase SA

132
Q

state specializations of the cell cytoplasm of the cells that line the proximal convoluted tubule to achieve this reabsorption

A

many mitochondria. This indicates that active/ energy requiring process is taking place because mitochondria produce a lot of ATP

133
Q

describe the process of secondary active transport for the mechanism of re-absorption

A

the sodium ions move into the cell by facilitated diffusion but they cotransport glucose or amino acids against their conc grad.

134
Q

what is the movement of sodium ions and glucose into the cell driven by in terms of the mechanism of reabsorption

A

driven by the concentration gradient created by pumping sodium ions out of the cell

135
Q

as substances move through to the blood, what substance follows and why

A

water follows as movement of these substances reduce the water potential of cells

136
Q

describe the mechanism of selective reabsorption (proximal convoluted tubule)

A
  1. Sodium ions are actively pumped out of the cells lining the tubule
  2. conc. of sodium ions in cell cytoplasm decrease creating a concentration gradient
  3. sodium ions diffuse into the cell through a cotransport protein- carrying glucose or an amino acid at the same time
  4. water moves into the cell by osmosis
  5. Glucose/ amino acids diffuse into the blood.
137
Q

what is the overall aim of the loop of Henle and due to this, what happens to the medulla.

A

to increase the conc of mineral ions in the tubule fluid, which has a similar effect upon mineral ions in the tissue fluid. This gives the tissue fluid in the medulla a very low (negative) water potential

138
Q

what do the descending and ascending limb of the loop of Henle set up

A

they set up a countercurrent multiplier mechanism

139
Q

what does the countercurrent multiplier mechanism allow for in the loop of Henle

A

the mechanism helps re-absorb water back into the blood by increasing the efficiency of transfer of mineral ions from the ascending limb into the descending limb

140
Q

describe the water potential in the descending limb as mineral ions enter

A

as mineral ions enter the descending limb, the conc of the fluid rises, meaning its water potential decreases. It becomes increasingly more negative the deeper the tubule extends into the medulla.

141
Q

is the upper portion of the ascending limb permeable or impermeable to water?

A

impermeable to water (water can’t leave, its thicker)

142
Q

what effect does the ionic movements in the ascending limb have?

A

creates a higher water potential in the fluid of the ascending limb, it also decreases the water potential of the tissue fluid in the medulla.

143
Q

towards the bottom of the loop of Henle, talk abt the water potential of the tissue fluid

A

The water potential of the tissue fluid becomes lower towards the bottom of the loop of Henle.

144
Q

what happens to the fluid passing down the collecting duct

A

passes through tissues with an ever-decreasing water potential. so, there is always a water potential gradient between the fluid of the collecting duct and that in the tissues. This allows water to be moves out of the collecting duct and into the tissue fluid by osmosis

145
Q

what is the arrangement of the loop of Henle known as

A

known as a hairpin countercurrent multiplier system.

146
Q

what is the overall effect of the hairpin countercurrent multiplier system

A

to increase the efficiency of transfer of mineral ions from the ascending limb to the descending limb, in order to create the water potential gradient seen in the medulla.

147
Q

state the order occurring during the reabsorption of water in the loop of Henle and the collecting duct (4)

A

1) Na+ and Cl- ions are actively pumped out into the medulla. This section is impermeable to water, so water remains in the tubule.
2) water moves out of the descending limb and into the medulla because there is a lower water potential in the medulla. The water in the medulla is reabsorbed back into the blood. The ions can’t diffuse out of the tubule.
3) ions diffuse out into the medulla near the bottom of the ascending limb. This section is impermeable to ions, permeable to water
4. the first 3 stages massively increase the ion conc od the medulla, causing water to move out of the collecting duct by osmosis and enter the blood.

148
Q

are the walls of the collecting duct permeable or impermeable to water

A

permeable to water

149
Q

why must the collecting duct pass through a region of low water potential

A

as it is passed through the region of low water potential, water is drawn out of the urine by osmosis. This conserves water and makes the urine more concentrated.

150
Q

why is it important for terrestrial animals to absorb as much water as possible

A

as they do not always have access to water- need to conserve water- water is a good solvent

151
Q

explain why the camel has very long loops of Henle

A

has a long loop to make the medulla slatier as there is more active removal of Na+ and Cl- so then more water then moves out into the collecting duct this allows the capillaries to gain more water which is advantageous as water is scarce

152
Q

explain why the conc of sodium stays constant as the fluid passes along the proximal convoluted tubule

A

both water and sodium are reabsorbed from the proximal tubule in equal amounts. sodium ions are reabsorbed by secondary active transport and water by osmosis.

153
Q

talk abt the water potential in the medulla in the tissue fluid as you move downwards

A

the water potential becomes even lower as you move down the medulla.

154
Q

concentration changes in the tubule fluid of glucose:

A

glucose decreases in conc as it is selectively reabsorbed from the proximal tubule

155
Q

concentration changes in the tubule fluid of sodium ions

A

sodium ions diffuse into the descending limb of the loop of Henle, causing the conc to rise. they are then pumped out of the ascending limb, so the conc falls.

156
Q

concentration changes in the tubule fluid of urea

A

the urea conc rises as the water is withdrawn from the tubule. urea is also actively moved into the tubule

157
Q

concentration changes in the tubule fluid of sodium ions with potassium ions

A

sodium ions are removed from the tubule, but their conc rises as water is removed from the tubule, and potassium ions increase the conc as water is removed. potassium ions are also actively transported into the tubule and removed in the urine.

158
Q

what is osmoregulation

A

osmoregulation is the control of water potential in the body. It involves controlling the water and salt levels in the body

159
Q

why is osmoregulation important to cells

A

to prevent the lysis or crenation of cells occurring

160
Q

what are the 3 ways in which we gain water

A

eating, drinking, respiration

161
Q

what are the 4 ways in which we lose water

A

sweating, urinating, breathing, faeces

162
Q

give an example of how a smaller volume of concentrated urine is made

A

increased sweating leads to more water loss thus a smaller vol of concentrated urine is made

163
Q

should gains and losses of water be balanced

A

yes

164
Q

what does the kidney act as and what does the kidney control

A

the kidney acts as an effector.
it acts an effector to control the water content of the body and the salt concentration in bodily fluids

165
Q

talk abt the volume of urine produced and how it’s made like this when you need to conserve less water (e.g. it’s a cool day and u have drank a lot of fluid)

A

a greater volume of urine will be produced. This is because the walls of the collecting duct will become less permeable, so less water is reabsorbed leading to this result.

166
Q

talk abt the volume of urine produced and how it’s made like this when you need to conserve more water (e.g., on a hot day or when you have drunk very little)*****

A

a smaller volume of urine will be produced. This is because the collecting duct walls are made more permeable so that more water can be reabsorbed into the blood.

167
Q

how can the kidneys alter the volume of urine produced

A

by altering the permeability of the collecting ducts, the walls of the collecting ducts can be made more or less permeable according to the needs of the body

168
Q

what do cells in the walls of the collecting duct respond to

A

cells in the walls of the collecting duct respond to the levels of antidiuretic hormone (ADH)

169
Q

State how the cell walls of the collecting duct are made more permeable to water

A

The ADH binds to the receptors that the cell has for ADH, this causes a chain of enzyme-controlled reactions inside the cell (an example of cell signaling). The end result of these reactions causes vesicles containing water-permeable channels (aquaporins) to fuse with the cell surface membrane. This makes the walls mor permeable to water.

170
Q

what occurs when the level of ADH in the blood rises.

A

1-more water permeable channels are inserted
2-this allows more water to be reabsorbed by osmosis, into the blood.
3-Less urine is being produced and the urine has a lower water potential

171
Q

what happens if the level of ADH in the blood falls and what effect does this have on the volume of urine

A

-if the level of ADH in the blood falls, then the cell surface folds inwards (invaginates) to create a new vesicle that remove water-permeable channels in the membrane. This makes the walls less permeable, and less water is reabsorbed, by osmosis into the blood. more water passes on down the collecting duct to form a greater volume of urine which is more dilute (higher water pot)

172
Q

the hypothalamus in the brain contains specialized cells called…

A

osmoreceptors

173
Q

what do osmoreceptors do

A

these sensory receptors detect the stimulus- they monitor the water potential of the blood. these cells respond to the effects of osmosis

174
Q

what do osmoreceptors do when the water potential of the blood is very low

A

the osmoreceptors lose water by osmosis and shrink. As a result, they stimulate neurosecretory cells in the hypothalamus.

175
Q

what are neurosecretory cells

A

specialized neurons (nerve cells) that produce and release ADH.

176
Q

where is ADH manufactured

A

manufactured by neurosecretory cells in the cell body, which lies in the hypothalamus.

177
Q

once ADH is manufactures, where does it move to and what is it stored in?

A

from the hypothalamus, it moves down the axon to the terminal bulb in the posterior pituitary gland, where it is stored in vesicles

178
Q

what happens once neurosecretory cells are stimulated by osmoreceptors

A

the neurosecretory cells carry action potentials down their axons and cause the release of ADH by exocytosis (this will be more or less depending on the water pot of the blood)

179
Q

simply when there is high ADH, what does this mean

A

high ADH= more water absorbed by osmosis in the blood= less urine and lower water pot (urine)

180
Q

state the 5-step pathway of negative feedback when the water potential of blood gets too high

A
  1. detected by osmoreceptors in hypothalamus
  2. less ADH released from posterior pituitary
  3. collecting duct walls less permeable
  4. less water reabsorbed into the blood (and more urine produced)
  5. decrease in water potential of the blood
181
Q

state the 5-step pathway of negative feedback when the water potential of blood gets too low

A
  1. detected by osmoreceptors in hypothalamus
  2. more ADH released from posterior pituitary
  3. collecting duct walls more permeable
  4. more water reabsorbed into the blood (and less urine produced)
  5. increase in water potential of the blood
182
Q

what does ADH enter that runs through the posterior pituitary gland

A

ADH enters the blood capillaries running through the posterior pituitary gland

183
Q

ADH is transported around the body, what does it act on

A

acts on the cells of the collecting ducts (its target cells)

184
Q

is ADH broken down quickly or slowly and what’s its half life

A
  • ADH is slowly broken down- it has a half life of about 20 minutes.
185
Q

what will happen when kidney failure occurs

A

-if the kidney fails completely they are unable to regulate the levels of water in electrolytes (substances that form charged particles in water) in the body or to remove waste products such as urea from the blood. This will rapidly lead to death.

186
Q

how can kidney function be assessed

A

kidney function can be assessed by estimating the glomerular filtration rate (GFR) and by analysing the urine for substances such as proteins.

187
Q

what do proteins in the urine indicate

A

that the filtration mechanism has been damaged

188
Q

what is the glomerular filtration rate (GFR) a measure of

A

GFR is a measure of how much fluid passes into the nephrons each minute.

189
Q

what is a normal reading of GFR

A

in the range of 90-120cm^3min^-1.

190
Q

if the GFR is below 60cm^3min^-1, what does this indicate

A

that there may be some form of chronic kidney disease

191
Q

if the GFR is below 15cm^3min^-1, what does this indicate

A

indicates kidney failure and and a need for immediate medical attention.

192
Q

what are the possible causes of kidney failure

A

-diabetes mellitus (both Type 1 and Type 2)
-heart disease
-hypertension
-infection

193
Q

what are the main treatments for kidney failure

A

-renal dialysis
-kidney transplant

194
Q

what is the most common treatment for kidney failure

A

-renal dialysis

195
Q

how does renal dialysis work to treat kidney failure

A

-waste products, excess fluid and mineral ions are removed from the blood by passing it over a partially permeable dialysis membrane that allows the exchange of substances between the blood and dialysis fluid.
The dialysis fluid contains the correct concentrations of mineral ions, urea, water and other substances found in the blood diffuse across the membrane into the dialysis fluid. Any substances that are too low in concentration diffuse into the blood from dialysis fluid.

196
Q

what are the two types of renal dialysis

A

-haemodialysis
-peritoneal dialysis (PD)

197
Q

what are the two treatments for treating kidney disease

A

-dialysis
-kidney transplant

198
Q

what could cause kidney failure

A

-kidney stones, infections, long term use pf medication, high blood pressure, high cholesterol, genetic disorders

199
Q

what could happen as a result of kidney failure

A

-tired
-stomach and pain swelling
-water pot of the body wont be regulated
-build up of urea

200
Q

renal dialysis: describe and explain haemodialysis

A

Blood from an artery or vein is passed into a machine containing an artificial dialysis membrane shaped to form many different artificial capillaries which increase the sa for exchange. any bubbles are removed before the blood is returned to the body via a vein.

201
Q

how often is haemodialysis carried out

A

carried out two or three times a week for several hours each session. some patients learn to carry it out at home

202
Q

what is the heparin pump for in haemodialysis

A

to prevent clotting

203
Q

renal dialysis: describe and explain peritoneal dialysis (PD)

A

the dialysis membrane is the body’s own abdominal membrane (peritoneum). First, a surgeon implants a permanent tube in the abdomen. Dialysis solution is poured through the tube and fills the space between the abdominal walls and organs. After several hours, the used solution can be drained from the abdomen. PD can be carried out at home or at work. Because the patient can walk around while having dialysis, the method is sometimes called ambulatory PD. Dialysis must be combined with a carefully monitored diet

204
Q

advantages of renal dialysis

A

+no risk from surgery
+keeps patient alive while waiting for a kidney donor
+can be carried out at home or at work(PD)
+removes excretory products e.g. urea
+maintains water pot of blood

205
Q

disadvantages of renal dialysis

A
  • time consuming (particularly haemodialysis)
  • need to carefully monitor diet (particularly PD)
    -risk of infection, especially PD
    -PD needs to be carried out daily
206
Q

describe and explain a kidney transplant

A

-involves major surgery. while the patient is under anaesthesia, the surgeon implants the new organ into the lower abdomen and attaches it to the blood supply and bladder. Patients are given immunosuppressant drugs to help prevent their immune system recognising the new organ as a foreign object and rejecting it.
-many patients feel immediately much better after a transplant
-old kidneys can remain unless infectious/causing pain

207
Q

name the advantages of a kidney transplant

A

+freedom from time consuming renal dialysis
+feeling physically fitter
+improved quality of life- able to travel
+improved self-image, no longer have a feeling of being chronically ill

208
Q

name the disadvantages of a kidney transplant

A

-need to take immunosuppressant drugs
-need for major surgery under general anaesthetic
-need for regular checks for signs for rejection
-side effects of immunosuppressant drugs: fluid retention, high blood pressure, susceptibility to infections

209
Q

how long do people wait for kidney transplants

A

around 3 years

210
Q

why/how can urine analysis take place

A

if molecules have a relative molecular mass smaller than 69,000, they can enter the nephron. This means any metabolic substance of product if it is small enough can pass into the urine if not reabsorbed.

211
Q

what can urine be tested for:

A

can be tested for:

-glucose in the diagnosis of diabetes
-alcohol to determine blood alcohol levels in drivers.
-many recreational drugs
-human chorionic gonadotrophin (hCG) in pregnancy testing
-anabolic steroids, to detect improper use in sporting competitions

212
Q

why can detection of pregnancy occur. What hormone allows for it

A

once a human embryo is implanted in the uterine lining, it produces a hormone called human chorionic gonadotrophin , it can be found in the urine with a molecular mass of 36700. Pregnancy testing kits use monoclonal antibodies which bind to hCG in urine.

213
Q

describe the 6 steps in how monoclonal antibodies work with a pregnancy test

A
  1. Urine poured onto a stick
  2. hCG binds to mobile antibodies attached to a blue bead
  3. mobile antibodies move down the test stick
  4. if hCG is present, it binds to antibodies holding the bead in place- a blue line forms
  5. mobile antibodies with no hCG attached bind to another fixed site to show the test is working.
214
Q

what do anabolic steroids do

A

anabolic steroid increase protein synthesis within cells, which results in the build-up of cell tissue, especially within the muscles.

215
Q

why are anabolic steroids controversial

A

because they can give advantage in competitive sport and have dangerous side effects

216
Q

why can anabolic steroids be detected in the urine

A

they remain in the blood for many days (half life of 16 hours). They are relatively small molecules so can enter the nephron easily and are not selectively reabsorbed. Testing for anabolic steroids involves analysing a urine sample in a laboratory using gas chromatography

217
Q

what is the difference in structure between the proximal convoluted tubule and the distal convoluted tubule

A

-the proximal convoluted tubule has a brush border
- the distal convoluted tubule doesn’t have a brush border

biology a level (17 decks)

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