5.2 Flashcards
(217 cards)
1
Q
what is excretion
A
the removal of metabolic waste from the body
2
Q
what is metabolic waste
A
defined as a substance that is produced in excess as a result of metabolic processes in cells
3
Q
what is egestion
A
the process of removing undigested food
4
Q
why is it important that metabolic waste substances are removed
A
need to be removed before they become too toxic
5
Q
what does the lungs remove
A
co2
6
Q
what does the liver remove
A
urea, hydrogen peroxide, detoxification of drugs and alcohol
7
Q
what does the kidneys remove
A
urea
8
Q
what does the skin remove
A
urea, uric acid and ammonia
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
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
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~~
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
13
Q
what things act in the blood as buffers to resist change in pH
A
-proteins (such as haemoglobin)
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
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)
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
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
18
Q
state the equation of deamination
A
amino acid + oxygen -> keto acid + ammonia
19
Q
how is urea formed ( equation)
A
ammonia + carbon dioxide -> urea + water
20
Q
what are liver cells called
A
hepatocytes
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
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
23
Q
what two sources supply the liver with blood
A
-the hepatic artery
-the hepatic portal vein
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
25
state stuff about the hepatic portal vein which supplies blood to the liver
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
26
what does blood leave via in the liver and what is it connected to
blood leaves via the hepatic vein, the hepatic vein re-joins the vena cava and the blood returns to the body's normal circulation
27
the 4th vessel connected to the liver is the bile duct, what is bile and what does the bile duct do?
-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.
28
what does bile contain
some excretory products such as bile pigments like bilirubin, which will leave the body with the faeces.
29
how are the cells, blood vessels and chambers inside the liver arranged
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
30
label the liver
pic
31
lable the liver cells
pic
32
label the cylindrical lobule
pic
33
what is the difference between the inter-lobular vessels and the intra-lobular vessels
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.
34
what happens to to the vessels once the hepatic artery and hepatic portal vein enter the liver
they split into smaller vessels and run parallel to the lobules ( inter-lobular vessels)
35
what is a sinusoid and what's its function
a special chamber that carries a mix of the blood from the intra and inter lobular vessels
36
what are Kupffer cells and what are their function
they are specialized macrophages that move about within the sinusoids. Their primary functions to breakdown and recycle old red blood cells
37
Kupffer cells break down old red blood cells, what is one of the products of hemoglobin breakdown?
hemoglobin breakdown forms bilirubin which is one of the bile pigments excreted as part of the bile.
38
bile is made in the _______ and released into the _______
1= liver
2= bile canaliculi
39
bile canaliculi join to form the ______
bile duct
40
what does the bile duct do
transports bile to the gall bladder
41
what has happened to the blood once it has reached the end of the sinusoid
the concentrations of many of its components have been modified and regulated
42
what is at the center of each lobule
at the center of each lobule is a branch of the hepatic vein known as the intra-lobular vessel.
43
what vessel do sinusoids empty into
the intra-lobular vessel
44
what joins together to form the hepatic vein and what does the hepatic vein do?
the hepatic vein is formed from branches of the hepatic vein from different lobules joining together.
-the hepatic vein drains blood from the liver
45
are liver cells specialized?
No- they are relatively unspecialized
46
state the shape of liver cells (hepatocytes) and what is on their surface
they have a simple cuboidal shape with many microvilli on their surface
47
liver cells have many metabolic functions, name some
-protein synthesis
-transformation and storage of carbohydrates
-synthesis of cholesterol and bile salts
-detoxification
48
liver cells have many metabolic functions, due to this, describe the nature of their cytoplasm
their cytoplasm must be very dense and is specialized in the numbers of organelles that it contains
49
the liver is metabolically very active, what functions does it carry out
-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
50
how does the liver store sugar (explain)
in the form of glycogen, the glycogen forms granules in the cytoplasm of hepatocytes
51
what substances should be detoxified in the liver
hydrogen peroxide or alcohol
52
what are the methods to render toxins as harmless in the liver
toxins are rendered harmless by oxidation, reduction, methylation or by combination with another molecule
53
what molecule allows liver cells to render toxins harmless
a great array of enzymes
54
what are the two enzymes in the liver that render toxins harmless
- catalase
-cytochrome P450
55
describe the role of catalase in the liver
converts hydrogen peroxide to oxygen and water. catalase has a particularly high turnover rate
56
describe the role of cytochrome P450 in the liver
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.
57
order these from smallest to largest :
lobe, liver, lobule, hepatocyte
hepatocyte, lobule, lobe, liver
58
what are the two vessels supplying the liver and what do they carry
-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)
59
what's the vein that takes blood away from the liver
the hepatic vein
60
what's the 4th vessel connected to the liver
the bile duct
61
which enzyme converts ethanol into ethanal
ethanol dehydrogenase
62
which enzyme converts ethenal into ethanoic acid
ethenal deydrogenase
63
what else is made when converting ethanol to ethenal and ethanoic acid, what is this substance important for
forms reduced NAD (a coenzyme for respiration)
64
what else is made when converting ethanol to ethanol and ethanoic acid, what is this substance important for
forms reduced NAD (a coenzyme for respiration)
65
what is the last substance that is made in the detoxification of alcohol?
Acetyl coenzyme A
66
The last substance that is made in the detoxification of alcohol is acetyl coenzyme A, what is this used for
for respiration
67
how is reduced NAD formed
when 2H combines with NAD
68
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?
fatty acids are converted to lipids and stored in hepatocytes as fat = enlarged liver (known as 'fatty liver')= hepatitis or cirrhosis
69
along with forming reduced NAD, what is NAD also required for
also required to oxidase and breakdown fatty acids for use in respiration.
70
what happens if the liver has to detoxify too much alcohol
it uses up stores of NAD and has insufficient left to deal with fatty acids
71
why cant excess amino acids be stored
becasue amino groups make them toxic
72
why would it be wasteful to excrete whole molecules of amino acids
because they contain a lot of energy
73
what treatments do excess amino acids undergo in the liver to remove and excrete the amino acid component
deamination followed by the ornithine cycle
74
describe the process of demination
-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
75
describe the properties of ammonia
very soluble and highly toxic (this means it must be converted to a less toxic form very quickly)
76
why should urea be produced from ammonia instead of ammonia staying present
urea is both less soluble and and less toxic
77
once urea is formed from the ornithine cycle, where does it travel to
it can be passed back into the blood and transported around the body to the kidneys.
78
once urea reaches the kidneys, what happens to it?
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
79
what is the reaction summary in the ornithine cycle
ammonia + carbon dioxide --> urea + water
80
what is the ornithine cycle responsible for
for removing ammonia before it builds up
81
ornithine cycle:
what is ammonia combined with to make it less toxic, what does this produce
its combined with co2 and Ornithine to produce water and Citulline
82
ornithine cycle:
what is Citrulline then combined with
combined with nh3, producing h20 and Arginine
83
ornithine cycle: what occurs after the formation of Arginine
h20 is added, Arginine is then reconverted to Ornithine by the removal of urea ( urea is produced)
84
ornithine cycle:
once urea is produced in the liver, what does it do
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.
85
what's bigger, the hepatic portal vein or the hepatic artery?
the branch of hepatic portal vein
86
where is the kidney positioned in the body
each side of the spine just below the rib
87
how does urine pass from the kidney to the bladder
it passes out of the kidney down the ureter to the bladder where it can be stored
88
the role of the kidneys is ______
excretion
89
how is urine produced
when the kidneys remove waste products from the blood, urine is produced
90
structure: what is the outer kidney surrounded by
a tough capsule
91
in a longitudinal section what three regions of the kidney are present?
-the outer region (the cortex)
-the inner region (the medulla)
-the center which is the pelvis leading to the ureter.
92
what does the bulk of the kidney consist of
consists of tiny tubules called nephrons
93
where does each nephron start
each nephron starts in the cortex at the Bowman's capsule
94
where is the remainder of the nephron and what does it look like
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
the cortex is a mass of ______ and ______
tubules and glomeruli
96
what does the renal artery split to form
splits to form many afferent arterioles
97
what do the afferent arterioles lead to
lead to a knot of capillaries called the glomerulus
98
where does the blood from the glomerulus continue to
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
what is each glomerulus surrounded by
by the Bowman's capsule
100
by what means is fluid from the blood is pushed into the Bowman's capsule
via ultrafiltration
101
what is the barrier called between the blood in the capillary and the lumen of the Bowman's capsule
the filter
102
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
-The endothelium of the capillary
-The basement membrane
-The epithelial cells of the Bowman's capsule
103
filtering of the liver: describe the endothelium of the capillary
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
filtering of the liver: describe the basement membrane
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
filtering of the liver: describe the epithelial cells of the bowman's capsule
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
describe major processes and what they allow for
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
the Bowman's capsule leads to the rest of the tubule, which has three parts.
-proximal convoluted tubule
-loop of Henle
-distal convoluted tubule
108
the fluid from many nephrons leads to what
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
what is ultrafiltration
filtration of the blood at a molecular level under pressure
110
whats a nephron
the functional unit of the kidney- there are 1 million
111
label the diagram
112
what is ultrafiltration
filtering of the blood at the molecular level
113
what is wider, the afferent arteriole or the efferent arteriole
the afferent arteriole is wider, so less of a pressure
114
what has a higher pressure, the glomerulus or the pressure in the bowman's capsule and what does this allow for
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
what 5 substances does the blood plasma contain
water
amino acids
glucose
urea
inorganic mineral ions
116
what is filtered out of the blood into the glomerular filtrate and why?
amino acids, urea, mineral ions, glucose, water* and small proteins (less than 69000 Da) because they are small enough
117
what isn't filtered out of the blood into the glomerular filtrate and why?
proteins larger than 69000 Da and red blood cells as they are too large
118
what two substances are found in the glomerular filtrate but not the urine and why
amino acids and glucose because they are re-absorbed. some mineral ions are also re-absorbed
119
why dos the concentration of urea in the urine higher than the concentration in the glomerular filtrate?
the conc. of urine increases due to the reabsorption of water
120
there are many blood cells and proteins in the capillaries, what does this mean for the water potential. What does this ensure
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
as the fluid from the bowman's capsule passes along the nephron tubule, what is its composition altered by?
by selective re-absorption
122
state the selective re-absorption that occurs at the proximal convoluted tube
-All sugars, most minerals and some water is reabsorbed here.
123
what is the tissue that lines the proximal convoluted tubule called
cuboidal epithelium
124
the tissue that lines the proximal convoluted tubule is called the cuboidal epithelium, talk abt the cells here
the cells have a brush border which is a result of being highly folded which increases SA
125
state the selective re-absorption that occurs at the descending limb of the loop of Henle
mineral ions are added here and water is removed. the water potential of the fluid is decreased
126
state the selective re-absorption that occurs at the ascending limb of the loop of Henle
mineral ions are removed here. The water potential of the fluid is increased
127
state the selective re-absorption that occurs at the collecting duct
more water is removed. The water potential of the fluid is decreased. The final product at the collecting duct is urine
128
what does the process of selective reabsorption allow for urine to have
allows urine to have a low water potential ( has a high conc of solutes than blood and tissue fluid)
129
what mechanisms does reabsorption involve
active transport
cotransport
130
state specializations of the cell surface in contact with the tubule fluid to achieve this reabsorption
-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
state specializations of the membrane in close contact with the capillaries and tissue fluid to achieve this reabsorption
highly folded to increase SA
132
state specializations of the cell cytoplasm of the cells that line the proximal convoluted tubule to achieve this reabsorption
many mitochondria. This indicates that active/ energy requiring process is taking place because mitochondria produce a lot of ATP
133
describe the process of secondary active transport for the mechanism of re-absorption
the sodium ions move into the cell by facilitated diffusion but they cotransport glucose or amino acids against their conc grad.
134
what is the movement of sodium ions and glucose into the cell driven by in terms of the mechanism of reabsorption
driven by the concentration gradient created by pumping sodium ions out of the cell
135
as substances move through to the blood, what substance follows and why
water follows as movement of these substances reduce the water potential of cells
136
describe the mechanism of selective reabsorption (proximal convoluted tubule)
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
what is the overall aim of the loop of Henle and due to this, what happens to the medulla.
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
what do the descending and ascending limb of the loop of Henle set up
they set up a countercurrent multiplier mechanism
139
what does the countercurrent multiplier mechanism allow for in the loop of Henle
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
describe the water potential in the descending limb as mineral ions enter
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
is the upper portion of the ascending limb permeable or impermeable to water?
impermeable to water (water can't leave, its thicker)
142
what effect does the ionic movements in the ascending limb have?
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
towards the bottom of the loop of Henle, talk abt the water potential of the tissue fluid
The water potential of the tissue fluid becomes lower towards the bottom of the loop of Henle.
144
what happens to the fluid passing down the collecting duct
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
what is the arrangement of the loop of Henle known as
known as a hairpin countercurrent multiplier system.
146
what is the overall effect of the hairpin countercurrent multiplier system
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
state the order occurring during the reabsorption of water in the loop of Henle and the collecting duct (4)
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
are the walls of the collecting duct permeable or impermeable to water
permeable to water
149
why must the collecting duct pass through a region of low water potential
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
why is it important for terrestrial animals to absorb as much water as possible
as they do not always have access to water- need to conserve water- water is a good solvent
151
explain why the camel has very long loops of Henle
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
explain why the conc of sodium stays constant as the fluid passes along the proximal convoluted tubule
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
talk abt the water potential in the medulla in the tissue fluid as you move downwards
the water potential becomes even lower as you move down the medulla.
154
concentration changes in the tubule fluid of glucose:
glucose decreases in conc as it is selectively reabsorbed from the proximal tubule
155
concentration changes in the tubule fluid of sodium ions
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
concentration changes in the tubule fluid of urea
the urea conc rises as the water is withdrawn from the tubule. urea is also actively moved into the tubule
157
concentration changes in the tubule fluid of sodium ions with potassium ions
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
what is osmoregulation
osmoregulation is the control of water potential in the body. It involves controlling the water and salt levels in the body
159
why is osmoregulation important to cells
to prevent the lysis or crenation of cells occurring
160
what are the 3 ways in which we gain water
eating, drinking, respiration
161
what are the 4 ways in which we lose water
sweating, urinating, breathing, faeces
162
give an example of how a smaller volume of concentrated urine is made
increased sweating leads to more water loss thus a smaller vol of concentrated urine is made
163
should gains and losses of water be balanced
yes
164
what does the kidney act as and what does the kidney control
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
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 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
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 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
how can the kidneys alter the volume of urine produced
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
what do cells in the walls of the collecting duct respond to
cells in the walls of the collecting duct respond to the levels of antidiuretic hormone (ADH)
169
State how the cell walls of the collecting duct are made more permeable to water
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
what occurs when the level of ADH in the blood rises.
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
what happens if the level of ADH in the blood falls and what effect does this have on the volume of urine
-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
the hypothalamus in the brain contains specialized cells called...
osmoreceptors
173
what do osmoreceptors do
these sensory receptors detect the stimulus- they monitor the water potential of the blood. these cells respond to the effects of osmosis
174
what do osmoreceptors do when the water potential of the blood is very low
the osmoreceptors lose water by osmosis and shrink. As a result, they stimulate neurosecretory cells in the hypothalamus.
175
what are neurosecretory cells
specialized neurons (nerve cells) that produce and release ADH.
176
where is ADH manufactured
manufactured by neurosecretory cells in the cell body, which lies in the hypothalamus.
177
once ADH is manufactures, where does it move to and what is it stored in?
from the hypothalamus, it moves down the axon to the terminal bulb in the posterior pituitary gland, where it is stored in vesicles
178
what happens once neurosecretory cells are stimulated by osmoreceptors
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
simply when there is high ADH, what does this mean
high ADH= more water absorbed by osmosis in the blood= less urine and lower water pot (urine)
180
state the 5-step pathway of negative feedback when the water potential of blood gets too high
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
state the 5-step pathway of negative feedback when the water potential of blood gets too low
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
what does ADH enter that runs through the posterior pituitary gland
ADH enters the blood capillaries running through the posterior pituitary gland
183
ADH is transported around the body, what does it act on
acts on the cells of the collecting ducts (its target cells)
184
is ADH broken down quickly or slowly and what's its half life
- ADH is slowly broken down- it has a half life of about 20 minutes.
185
what will happen when kidney failure occurs
-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
how can kidney function be assessed
kidney function can be assessed by estimating the glomerular filtration rate (GFR) and by analysing the urine for substances such as proteins.
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what do proteins in the urine indicate
that the filtration mechanism has been damaged
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what is the glomerular filtration rate (GFR) a measure of
GFR is a measure of how much fluid passes into the nephrons each minute.
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what is a normal reading of GFR
in the range of 90-120cm^3min^-1.
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if the GFR is below 60cm^3min^-1, what does this indicate
that there may be some form of chronic kidney disease
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if the GFR is below 15cm^3min^-1, what does this indicate
indicates kidney failure and and a need for immediate medical attention.
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what are the possible causes of kidney failure
-diabetes mellitus (both Type 1 and Type 2)
-heart disease
-hypertension
-infection
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what are the main treatments for kidney failure
-renal dialysis
-kidney transplant
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what is the most common treatment for kidney failure
-renal dialysis
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how does renal dialysis work to treat kidney failure
-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.
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what are the two types of renal dialysis
-haemodialysis
-peritoneal dialysis (PD)
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what are the two treatments for treating kidney disease
-dialysis
-kidney transplant
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what could cause kidney failure
-kidney stones, infections, long term use pf medication, high blood pressure, high cholesterol, genetic disorders
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what could happen as a result of kidney failure
-tired
-stomach and pain swelling
-water pot of the body wont be regulated
-build up of urea
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renal dialysis: describe and explain haemodialysis
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.
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how often is haemodialysis carried out
carried out two or three times a week for several hours each session. some patients learn to carry it out at home
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what is the heparin pump for in haemodialysis
to prevent clotting
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renal dialysis: describe and explain peritoneal dialysis (PD)
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
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advantages of renal dialysis
+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
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disadvantages of renal dialysis
- time consuming (particularly haemodialysis)
- need to carefully monitor diet (particularly PD)
-risk of infection, especially PD
-PD needs to be carried out daily
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describe and explain a kidney transplant
-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
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name the advantages of a kidney transplant
+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
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name the disadvantages of a kidney transplant
-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
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how long do people wait for kidney transplants
around 3 years
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why/how can urine analysis take place
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.
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what can urine be tested for:
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
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why can detection of pregnancy occur. What hormone allows for it
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.
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describe the 6 steps in how monoclonal antibodies work with a pregnancy test
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.
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what do anabolic steroids do
anabolic steroid increase protein synthesis within cells, which results in the build-up of cell tissue, especially within the muscles.
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why are anabolic steroids controversial
because they can give advantage in competitive sport and have dangerous side effects
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why can anabolic steroids be detected in the urine
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
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what is the difference in structure between the proximal convoluted tubule and the distal convoluted tubule
-the proximal convoluted tubule has a brush border
- the distal convoluted tubule doesn't have a brush border
