CHAPTER 15 - HOMEOSTASIS Flashcards
1
Q
What is Dynamic equilibrium
A
All processes occur at the same rate, leading to no change in the system, and no change in concentration
2
Q
What is Homeostasis
A
A dynamic equilibrium, with small fluctuations over a narrow range of conditions
3
Q
What do sensory receptors do
A
Detect changes in the internal and external environment of an organism
4
Q
What are effectors
A
The muscles or glands that react to the motor stimulus to bring about a change in response to a stimulus
5
Q
Where does the information from the sensory receptors get transmitted to
A
To the brain, sent along motor neurones to the effectors to bring about change
6
Q
What is negative feedback
A
They work to reverse the initial stimulus
eg. water levels in the body decrease, response is to raise levels, water levels increase, response to lower levels occurs
(pg 407)
7
Q
What is positive feedback
A
A change is detected and the effectors are stimulated to reinforce and increase the response, eg. blood clotting
(pg 407)
8
Q
What is an example of negative feedback
A
Temperature control
Water balance
9
Q
What are some examples of positive feedback
A
Blood clotting cascade
Childbirth (pg 407)
10
Q
Suggest three different types of receptors explaining what changes they detect
A
Pacinian corpuscle /mechanoreceptor detects changes in pressure.
Photoreceptors detect changes in light,
chemoreceptors detect chemical changes e.g., pH.
Thermoreceptors detect temperature change
11
Q
Suggest two different types of effector and give an example of what they do
A
Muscles – move limbs, squeeze gut, squeeze chemicals from glands.
Glands – secrete hormones and enzymes
12
Q
What is homeostasis
A
The maintenance of a dynamic equilibrium
within narrow ranges in the body
13
Q
Why are both receptors and effectors important in homeostasis
A
body needs sensory receptors to monitor changes in the internal environment
effectors to respond to those changes
and restore the original balance
14
Q
Suggest why effective homeostasis depends on negative rather than positive feedback systems
A
In a negative feedback system, when a change takes place systems in the body act to return the situation to normal
– they inhibit the change
in a positive feedback system, when a change takes place systems in the body act to reinforce the change
In homeostasis, the body seeks to maintain a dynamic equilibrium
if there is a change, the need is to inhibit it and return things to the original state
this is possible with negative feedback systems but not with positive feedback systems
15
Q
What is thermoregulation
A
The maintenance of a relatively constant core body temperature to maintain optimum enzyme activity
16
Q
What factors affect an organisms temperature
A
Exothermic chemical reactions
Latent heat of evaporation (objects cool as water evaporates from surface)
Radiation
Convection
Conduction
17
Q
What are ectotherms
A
Organisms that use their surroundings to warm their bodies
18
Q
What does ectotherm directly translate to
A
Outside heat - hence regulate heat from outside
19
Q
What are some examples of ectotherms
A
All invertebrates as well as Fish, Amphibians and reptiles
20
Q
Why do many aquatic ectotherms not need to thermoregulate (eg. fish)
A
High heat capacity of water means that the temperature of their environment doesn’t change much.
21
Q
What issue do land-dwelling ectotherms have due to changing air temperature
A
Temperature varies dramatically during the day and across seasons
As a result, evolved a range of strategies to cope
22
Q
What is an endotherm
A
An organism that relies on their metabolic processes to warm up which means they have stable core temperature
23
Q
What does endotherm directly translate to
A
Inside heat
24
Q
What do behavioural responses in ectotherms do
A
Allows the organism to increase or reduce the radiation they absorb from the sun
25
How do many ectotherms warm up and why - behaviourally
Conduction and Basking in the sun, so that they become warm enough to to reach the temperature at which their metabolic processes happen so they can be active
26
Why do lizards need to bask in the sun
To get to the temperature to warm up their metabolic processes to move fast and to hunt prey
27
Why do Insects need to bask in the sun
To get the temperature to warm up their bodies to allow their metabolic processes to start so they can get warm enough to fly - spread wings to increase SA
28
As well as Basking in the sun, how else do ectotherms warm up behaviourally
Thermal conduction by pressing their bodies against hot ground
Warmer through metabolic processes
Contracting and vibrating muscles to warm them up
29
How do ectotherms cool their body temperature
Finding shelter, hiding in cracks or rocks or digging burrows
Press their bodies against cool earth or into water/mud - evaporation occurs
Minimum surface area exposed to sun
Minimal movements to reduce metabolic heat generated
30
What other responses to regulate temperature to ectotherms have, besides behavioural
Physiological
Anatomical
31
How does colour of the skin help lizards to regulate body temperature physiologically
Dark colours absorb more radiation than lighter colours
Lizards living in colder climates tend to be darker coloured than lizards in hotter climates so that they get warmer
32
How else do ectotherms regulate their temperature physiologically, besides skin colour
Altering heart rate, to increase or decrease the metabolic rate
Inflating/deflating body
holds close/far away from surface - convection
Can open/close its mouth and pants
33
How are ectotherms better adapted than endotherms
They need less food as they use less energy regulating their temperatures - so they can survive in difficult habitats where food is in short supply
34
Example of an ectotherm
Namaqua Chameleon - model ectotherm - pg 410 LOOK UP
35
What is an ectotherm
Animals that use heat from their surroundings to warm their bodies
so their core body temperature is heavily dependent on their environment
36
Give an example of an ectotherm warming up or cooling down by interaction with the environment by
A) radiation
B) Conduction
C) Convection
D) Evaporation
A) When an ectotherm such as a lizard basks in the Sun - it gains heat by radiation from the sunlight
B) When an ectotherm such as a lizard presses against the hot earth - it gains heat by conduction
C) When an ectotherm such as a lizard stands up as high as it can off the ground - it will lose heat by convection currents in the air around it
D) When an ectotherm such as a lizard wallows in mud or water - it loses heat by evaporation of the water from the surface of the skin
37
In any homeostatic system, what are needed to detect a change in the internal environment
Receptors
38
Where are the peripheral temperature receptors located
The Skin
39
What is the temperature receptor in the body which detects blood temperature in the body
Hypothalamus
40
What is the job of the hypothalamus
Maintain dynamic equilibrium within 1 degrees celsius of 37 degrees
41
What do endotherms use their internal exothermic metabolic activities to do
Keep them warm
42
What do endotherms use energy-requiring physiological responses to do
Cool down
43
What behavioural responses do endotherms have to regulate body temperature
Basking in the sun
Pressing themselves into warm surfaces
Wallowing in water and mud to cool down
Digging burrows
Hibernation and Aestivation
44
What behavioural adaptations do humans have to maintain body temperature
Clothes are worn to stay warm
Houses are built then heated up or cooled down
45
What are the physiological responses endotherms have to overheating
Vasodilation
Increased sweating
Reducing insulation of hair or feathers
46
What is Vasodilation and how does it help cool down an endotherm
When the arterioles near the surface of the skin dilate when the temperature rises
Vessels connecting arterioles and venues (arteriovenous shunt vessels) constrict
This forces the blood through the capillary networks close to the surface of the skin. The skin flushes and cools as a result of increased radiation
If skin is pressed against cool surfaces, then cooling results from conduction (pg 412)
47
How does increased sweating cool down an endotherm
As core temperature starts to increase, rates of swearing also increase
Sweat spreads out across the surface of the skin, from sweat glands all over the body (in some mammals)
Sweat evaporates from skin, heat is lost, cooling the blood below the surface
In some animals, sweat glands are restricted to the less hairy areas of the body, such as the paws
These animals open their mouths and pant, losing heat as the water evaporates
Kangaroos and cats often lick their front legs to keep cool in high temperatures
48
How does reducing the insulating effect of hair or feathers cool an organism down
As body temperature begins to increase, the erector pili muscles in the skin relax, hair or feathers flatten to the skin
Avoids trapping layer of insulating air
49
What anatomical adaptations do endotherms living in warm climates have to cool down
Large surface area: Volume ratio to maximise cooling (eg. include large ears and wrinkly skin)
pale fur or feathers to reflect radiation
50
What are the physiological responses endotherms have to help warm up
Vasoconstriction
Decreased sweating
Rising the body hair or feathers
Shivering
51
How does vasoconstriction help keep an endotherm warm
Arterioles near the surface of the skin constrict
Arteriovenous shunt vessels dilate, so very little blood flows through capillaries close to skin
Skin looks pale and little radiation takes place
Warm blood is kept well below the surface
52
How does decreased sweating help warm up an endotherm
As coach of falls, the rate of sweating decreases and the rate of sweat production will stop entirely.
This reduces cooling by the evaporation of water from the surface of the skin, although some evaporation from the lungs still continues.
53
How does shivering help warm an endotherm up
As the core temperature falls, the body begins to shiver
This is the involuntary contracting and relaxing of the large voluntary muscles in the body.
The metabolic heat from the exothermic reaction is warming up the body instead of moving it is an effective way of raising core temperature.
54
What anatomical adaptations do endotherms living in cold climates have to keep warm
Small SA:V (eg. small ears)
Thick layer of fat underneath skin eg. Blubber in whales and seals
Hibernation - build up fat stores, well insulated shelter and lower their metabolic rate so they pass the worst of the cold weather
Black skin to absorb heat radiation
55
Example of an endotherm in a hot climate
Desert (Fennec) fox, Camel etc..
56
Example of an endotherm living in a cold climate
Polar bear, Whale etc...
57
What are the complex homeostatic mechanisms controlled by
Hypothalamus
58
What are the two control centres in the hypothalamus called
Heat loss centre, Heat Gain centre
59
How does the Heat loss centre work
When temperature of the blood flowing through the hypothalamus increases, it send impulses through the autonomic motor neurones to effectors in the skin and muscles, triggering responses that act to lower the core temperature
60
How does the Heat gain centre work
This is activated when the temperature of the blood flowing through the hypothalamus decreases, It sends impulses through the autonomic nervous system to effectors in the skin and muscles, triggering responses that act to raise the core temperature
61
Read the feedback diagram on page 414 - fairly basic but give it a read
do it preferably now pls
62
Why is the temperature so important to both ectotherms and endotherms
Reactions of respiration etc are controlled by enzymes
and have an optimum temperature
if temperature of an organism is too low – reactions are very slow
so there is not enough energy for muscle contraction for movement etc
if temperature is too high, enzymes are denatured,
cells of the body die which can lead to death
63
Explain how the role of evaporation of water in thermoregulation differs between ectotherms and endotherms
Ectotherms do not sweat
they can cool down using evaporation of water only if they wallow or submerge in water
when they emerge from the water or mud they cool down as the water evaporates from their skin surface
endotherms sweat as the core body temperature increases
the evaporation of the water in sweat lowers the skin surface temperature
which in turn lowers temperature of blood by conduction
64
Explain the difference in the role of the peripheral temperature receptors and the temperature receptors in the hypothalamus in the regulation of the core body temperature in an endotherm
Peripheral temperature receptors are in the skin and detect changes in surface temperature
receptors in the hypothalamus detect blood temperature within the body
the peripheral receptors respond to environmental stimuli while receptors in the hypothalamus respond directly to changes in core temperature
65
Endotherms that live in very hot climates are often pale coloured
A) Why is this
B) Why might you expect endotherms that live in very cold environments to be dark coloured
C) In fact, very few endotherms that live in cold environments are dark coloured. Suggest reasons for this
A)
Pale colours reflect
light
and therefore heat
so they reduce the amount of heat absorbed from sunlight
B)
Dark colours absorb more heat
therefore help to increase the body temperature
C)
Cold places tend to have a lot of ice and snow
dark colours show up against the white
makes animals very visible to predators
increased risk of being eaten is a stronger evolutionary driver than advantage of heat absorption
66
What is Excretion
The removal of the waste products of the metabolism from the body
67
What are the main metabolic waste products in mammals, what are they the products of and how are they excreted
Carbon dioxide - cellular respiration; excreted from the lungs
Bile pigments - Breakdown of haemoglobin; excreted by liver in the bile and out through faeces
Nitrogenous waste products (urea) - breakdown of excess Amino acids; excreted by kidneys in urine
68
Is the liver fast or slow growing
Fast growing, damaged areas can generally regenerate very quickly
69
Does the liver have a high or low blood supply
Very high - 1 dm3 of blood flows through it per minute
70
How is the liver supplied with oxygenated blood
Hepatic artery - From heart
Hepatic portal vein - From Intestines
71
What is the name of the blood vessel that returns blood to the heart from the liver
Hepatic vein
72
What is carried in the blood of the hepatic portal vein
The products of digestion straight from the intestines to the liver
Starting point for many metabolic activities in the liver
73
What are liver cells also called
Hepatocytes
74
What are some features of hepatocytes
Large Nuclei, Prominent Golgi apparatus and many mitochondria
Shows they are metabolically active
Divide and replicate, even if 65% of the liver is lost, it will regenerate in a matter of months
75
Where does the blood from the hepatic artery and hepatic portal vein mix
Sinusoids - channels/ spaces surrounded by hepatocytes
76
Why does the blood from the hepatic artery and the hepatic portal vein mix in the sinusoids
It increases the oxygen content in the blood of the hepatic portal vein, applying the hepatocytes with enough oxygen for their needs
77
Where are Kupffer cells found and what do they do
Found in the sinusoids in the liver, acts as resident macrophages of the liver, ingesting foreign particles and helping protect against disease
78
Where do the hepatocytes secrete bile from the breakdown of blood into
Spaces in between sinusoids called canaliculi, which drain into the bile duct which takes it to the gall bladder
79
What are some functions of the liver (~500)
Carbohydrate metabolism
Deamination of excess amino acids
Detoxification
80
How does the liver regulate carbohydrate metabolism
When blood glucose levels rise, insulin levels rise and stimulate hepatocytes to convert glucose to the storage of glycogen
When blood sugar levels start to fall, hepatocytes convert the glycogen back to glucose under the influence of a different hormone - glucagon
81
What is transamination and where does it happen
The conversion of one amino acid into another, in the liver
82
What is deamination
The removal of an amine group from a molecule
83
Can the body store excess proteins or amino acids?
No, it is deaminated and the molecule (minus -NH2/3) is sent to respiration
84
What happens to the ammonia after deamination occurs
Converted to urea, which is highly toxic in high concentrations so it will be excreted in urine
85
What is the ornithine cycle
The ammonia produced from the deamination of proteins converted into urea by a set of enzyme-controlled reactions
86
Describe the events in the Ornithine cycle
Amino acid/protein is deaminated, NH3 enters ornithine cycle, rest of the molecule is sent to respiration
The NH3 is joined to ornithine with a CO2 molecule, losing a molecule of water in the process, forming a compound called citruline
Citruline is then joined by a second NH3 group rom deamination, losing another water molecule and forming an Arginine molecule
Water is then added to Arginine, forming urea (NH2 - C=O - NH2) , which leaves the cycle, and regenerating a molecule of ornithine
87
What toxins are commonly broken down in the liver
Alcohol and drugs
Or other potentially poisonous substances, usually formed from metabolic pathways
88
What is an example of the liver breaking down a by-product of a metabolic pathway
Breakdown of Hydrogen Peroxide, by enzyme catalase, converting it into oxygen and water
2H2O2 --> 2H2O + O2
89
What is an example of the liver detoxifying a substance
Detoxification of ethanol, by enzyme alcohol dehydrogenase, converting ethanol into ethanal
C2H5OH ---> C2H4O + H2
Ethanal is often converted into ethanoate which is used to build up fatty acids or is used in cellular respiration
90
Many people use the term excretion to describe defecation. Why is this not entirely accurate?
Excretion is the removal of the waste products of metabolism from the body
including carbon dioxide, urea, and bile
defecation is largely the removal of undigested food, dead cells, and bacteria from the body
but some excretion takes place as bile produced from the breakdown of haemoglobin from old red blood cells
is removed from the body in the faeces
91
Read page 418 on understanding pictures of the liver and 419 on cirrhosis of the liver
Urgent do it
92
Hepatocytes make up 70-85% of the livers mass.
A) What is a hepatocyte
B) Hepatocytes have large nuclei, lots of Golgi and many mitochondria. What does this tell you about the cells
A) A Type of cell that makes up most of the liver
and carries out most of the homeostatic functions in the liver
B) Large nuclei – indicates active DNA transcription
Lots of Golgi apparatus indicates high level of protein packaging and modification
likely to make many proteins that are modified for different uses
many mitochondria hepatocytes very active
high production of ATP for cell reactions
93
Explain how the structure of the liver is adapted for its function in the body
Blood from hepatic portal vein brings products of digestion and cell metabolism to the liver
blood from hepatic artery brings oxygenated blood to liver
blood from the HPV and HA combine in the sinusoids, providing raw materials and oxygen for hepatocytes
hepatocytes line sinusoids and absorb digested food, toxins, and oxygen from blood, also break down toxins, convert glucose to glycogen, deaminate amino acids
Kupffer cells act as macrophages and engulf and digest foreign cells and debris
bile secreted into canaliculi as haemoglobin broken down in hepatocytes
hepatic vein removes deoxygenated blood carrying products of detoxification e.g., urea away from the liver
94
Why do you think the liver is particularly affected by excess drinking
Ethanol from alcoholic drinks is absorbed and concentrated in the liver
to be detoxified
hepatocytes detoxify ethanol using the enzyme alcohol dehydrogenase
forming ethanal
that is further modified to form ethanoate
So an excess of toxic ethanol would affect the cells of the liver first
95
Why is a build-up of fatty tissue a common symptom of excess drinking
Ethanoate produced as ethanol is detoxified in the liver
can be fed into the pathway synthesising fatty acids
and so lipids
if there is a lot of alcohol a lot of fat is likely to build up in the hepatocytes as a result of the detoxification process
96
Where are the kidneys located
Back of the abdominal cavity
97
What are the kidneys surrounded by
A layer or thick protective fat and a layer of fibrous tissue
98
What homeostatic roles does the kidney have in the body
Excretion and osmoregulation
E: Filter nitrogenous waste out of the blood, especially urea
O: Maintains water balance and pH of the blood, hence tissue fluid that surrounds all the cells
99
What blood vessel supplies the Kidney with blood
The renal arteries which branch off from the abdominal aorta
100
Which blood vessel does blood that has circulated through the kidneys leave from
Renal Vein, into the inferior vena cava
101
How much blood does the kidney filter per day
180 dm3
All of the body's blood passes through the kidneys in an hour
102
How much urine does the kidney produce per day
1-2 dm3 (depending on many factors)
103
What are the filtering units in the kidney
Nephrons (millions of them)
104
What is the sterile liquid produced by the kidney tubules called?
Urine
105
What tubes does urine pass out of the kidneys from
Ureters
106
What is the muscular sac that collects the urine
The bladder - stores 400-600 cm3 of urine
107
What happens when the bladder is full
The sphincter at the exit to the bladder opens and the urine passes out of the body down the urethra
108
What are the 3 main areas of the kidney
Cortex (not in middle ironically),
medulla (in middle) and
pelvis (latin for basin)
(pgs 420 and 421)
109
What is the renal cortex
The cortex is the dark outer layer of the kidney.
This is what filtering of the blood takes place, and it has a very dense capillary network, carrying the blood from the renal artery to the nephrons
110
What is the Renal medulla
The middle section of the kidney, which is lighter in colour. It contains the tubules of the nephron that form the pyramids of the kidneys and the collecting ducts
111
What is the renal pelvis
The pelvis (which is latin for basin) of the kidney is the central chamber where the urine collects before passing out down the ureter
112
What happens in the nephrons
The blood is filtered and then the majority of the filtered material is returned to the blood, removing nitrogenous waste and balancing the mineral ions and water
113
How long is each nephron and how many are there in each kidney
3 cm long and there are 1.5 million per kidney, Maning the body has several kilometres of tubules for the reabsorption of water, glucose salts and other substances back into the blood
114
What is a nephron comprised of
Glomerulus
Bowmans capsule
Proximal convoluted tubule
Loop of Henle
Distal Convoluted tubule
Collecting duct
115
Where are nephrons located in the kidney
between the cortex and medulla
Top half eg. Glomerulus, Bowmans capsule and convoluted tubules are in the cortex
Bottom half eg. ascending and descending limbs, loop of henle and the collecting duct are in the medulla
(pg 421)
116
What is the Bowmans capsule
A cup-shaped structure that contains the glomerulus, a tangle of capillaries.
More blood goes into the glomerulus than leaves it due to the ultrafiltration processes that take place
117
What is the glomerulus
A tangle of capillaries in the nephrons, with blood entering it from the renal artery
118
What is the blood supply to a glomerulus and what does It leave by
Blood from branch of renal artery enters glomerulus through the afferent arteriole and leaves via the efferent arteriole
119
What is the Proximal convoluted tubule
The first coiled region of the tubule after the Bowmans capsule, found in the cortex of the kidney.
This is where many of the substances needed by the body reabsorbed into the blood
120
What is a loop of Henle
A lump of tubule that creates a region with a very high solute concentration in the tissue fluid deep in the kidney medulla. The descending loop runs down from the cortex through the medulla to a hairpin bend at the bottom of the loop. The ascending limb travels back up through the middle to the cortex.
121
What is the distal convoluted tubule
Second twisted tubule were the fine-tuning of the water balance of the body takes place.
The permeability of the walls to water varies in response to the levels of anti-diuretic hormone (ADH) in the blood.
Further regulation of the ion balance and pH of the blood. Also it takes place in this tubule.
122
What is the collecting duct
The urine passes down the collecting duct through the medulla to the pelvis.
More fine tuning of the water balance takes place – the walls of this part of the tubule are also sensitive to ADH.
123
How does blood leave the nephron site
After ultrafiltration occurs, the blood will lead into a network of capillaries that lead into a venue then into the renal vein, out of the kidney
124
What is the blood composition like after it has left the kidney
Blood that the kidney has greatly reduce levels of urea, but the levels of glucose and other substances such as amino acids are needed by the body are almost the same as when the blood enters the kidneys (maybe slightly less as some glucose would have been used for selective reabsorption - active process)
The mineral concentration in the blood has also been restored to ideal levels
125
What is ultrafiltration
The first stage in the removal of nitrogenous waste and osmoregulation of the blood
126
What is formed due to the structure of the glomerulus and Bowmans capsules
tissue fluid in the capillary beds of the body
127
Describe how the first stage of ultrafiltration works in the glomerulus
Enters via a relatively wide afferent (incoming) arteriole from branch of renal artery
Blood leads through a narrow efferent (outwards) arteriole and as a result there is high pressure in the capillaries of the glomerulus
This forces blood out through the capillary wall - which acts like a sieve
The fluid passes through the basement membrane (outside membrane of Bowmans capsule) - which is made up of collagen fibres and other proteins that act as a second sieve
Most plasma contents can pass through the basement membrane but the blood cells and many proteins are retained in the capillary because of their size
128
What do the Bowmans capsule have behind their basement layer
Podocytes, which act as an additional filter
129
What do podocytes have which make them specialised
Extensions called pedicels that wrap around the capillaries forming slits
130
What is the job of podocytes
To make sure that any cells, platelets or large plasma proteins that have managed to get through the epithelial cells and the basement membrane don't get through to the tubule itself
131
What does the filtrate that enters the Bowmans capsule contain
Glucose, salt, urea and other substances in exactly the sae concentrations as they are in the blood plasma
132
What is the glomerular filtration rate
The volume of blood that is filtered through the kidneys in a given time
133
What is the ultra filtrate compared to the blood plasma
Hypotonic - less concentrated than
134
What is the main function of the nephron after the bowman's capsule
To return most of the filtered substances back into the blood
135
What is moved back into the body, where and how
Glucose, amino acids, vitamins and hormones
In the proximal convoluted tubule
By active transport
136
How are Sodium chloride (ions) reabsorbed - process
Sodium ions removed back into the blood by active transport and chloride ions and water follow passively down concentration gradients
137
What adaptions do the cells lining the proximal convoluted tubule have
Covered with microvilli, greatly increasing the surface area over which substances can be reabsorbed
Have many mitochondria to provide the ATP needed in active transport systems
138
Where do substances diffuse to after they are removed from the nephron
The extensive capillary network which surrounds the tubules down steep concentration gradients
139
How are the steep concentration gradients maintained in the capillaries of the lungs
Constant flow of blood
140
At the end of the proximal convoluted tubule, at the loop of hence, what is the concentration of filtrate compared to blood and tissue fluid
Isotonic - same concentration
141
What does the loop of Henle allow for
The production of more concentrated urine than their own blood
142
What is essential to how the loop of hence functions
That different areas of the loop have different permeabilities,
acts as a countercurrent, using energy to produce concentration gradients that result in the movement of substances such as water from one area to another
143
What are the changes that take place in the descending limb of the loop of henle dependant on
The high concentration of sodium and chloride ions in the tissue fluid of the medulla that are the result of events in the ascending limb of the loop
144
Where dos the balancing of water take place
The distal convoluted tubule and the collecting duct
145
What does the permeability of the walls of the collecting duct and DCT depend on
Levels of ADH in the body
146
How are the cells that line the distal convoluted tubule adapted to their function
Many mitochondria to carry out active transport
147
If the body lacks salt, how does the DCT respond to counteract this
Sodium ions will be actively pumped out of the tubule with chloride ions following down an electrochemical gradient
148
Where is the concentration and volume of the urine produced determined
Collecting Duct
149
How does water move out of the collecting duct and what is the result on the urine concentration
Leaves my diffusion/osmosis as it passes through renal medulla,
More concentrated urine
150
As a result of water leaving the collecting duct, what are the knock on effects
Sodium ions in the surrounding tissue fluid increases through the medulla from the cortex to the pelvis
So more water can be removed all the way along the length of the collecting duct
Producing very hypertonic urine when the body needs to conserve water
Controlled by ADH
151
What is the general trend with the loop of henle and an animals ability to produce concentrated urine
The longer the loop of henle, the more concentrated the urine can be produced
152
Give 3 examples of how the kidneys are well adapted for their functions in the body
Layer of fat
to protect against mechanical damage
good blood supply
to ensure diffusion gradients maintained
different sized blood vessels going into and out of the glomerulus
to give high blood pressure for ultrafiltration
153
How much blood is filtered over 24 hours through the kidneys, and what percentage of this filtrate is lost to the body as urine
180 Litres or dm3
1–2 litres of urine produced in 24 hours
mean urine production in 24 hours is around 1.5 litres therefore percentage filtrate lost is 1.5/180 × 100 = 0.83%
154
What is ultrafiltration?
The forcing of liquid out from the blood capillaries
into the Bowman’s capsule
due to the high blood pressure in the glomerulus
resulting from the fact that the arteriole feeding into the knot of capillaries is wider than the arteriole leaving the glomerulus
155
What would you expect to see in a normal glomerular filtrate?
Water, urea, glucose, amino acids, mineral ions – the same concentrations as the blood without the red blood cells and the large plasma proteins
156
Kidney infections can damage the lining of the Bowmans capsule. How might this result in protein appearing in the urine.
Podocytes provide an extra filter
preventing any large proteins forced out of capillaries from getting into filtrate in tubule
if the podocytes are damaged by infection, the structure will break down
and proteins can get through into the kidney tubules
they are not reabsorbed in the tubules
so will be lost in the urine
157
Approximately how much more urea is there in urine than in blood
There is around 1000 times more urea in the urine than in the blood
158
Suggest 3 possible factors that might affect the amount of urea in the urine
Amount of protein eaten, amount of exercise done, blood pressure levels,
activity of the kidneys etc...
159
Why do the factors that affect the urea concentration in urine not affect the urea concentration of the blood
Because urea is constantly removed from the blood by the kidneys
160
Explain the main stages of how the kidney tubules produce urine the is more concentrated than the blood in the proximal convoluted tubule (1/5)
Active transport of substances back into capillaries
water follows by osmosis
through permeable walls up to 80% of the filtrate reabsorbed
161
Explain the main stages of how the kidney tubules produce urine the is more concentrated than the blood in the Descending limb of the loop of Henle (2/5)
Water leaves by osmosis into concentrated tissue of medulla
sodium and chloride ions move into the tubule by diffusion down concentration gradients
from the tissue fluid of the medulla
as concentration of tissue increases through medulla, diffusion gradients maintained all the way along the descending limb
so contains very concentrated solution at hairpin
(pg 425)
162
Explain the main stages of how the kidney tubules produce urine the is more concentrated than the blood in the Ascending limb of the loop of Henle (3/5)
Chloride ions removed from filtrate into tissue fluid of medulla by active transport
sodium ions follow down electrochemical gradient
but walls of ascending limb are impermeable to water
so water cannot follow by osmosis
results in very high concentration of mineral ions in the tissue fluid of the medulla
(pg 425)
163
Explain the main stages of how the kidney tubules produce urine the is more concentrated than the blood in the Distal Convoluted Tubule (4/5)
Permeability of the walls of the distal tubule varies with the levels of ADH
sodium ions may be actively pumped out
with chloride ions following down an electrochemical gradient
further concentrating the medulla; water may leave by osmosis concentrating the urine
if the walls of the tubule are permeable in response to ADH
other substances may be actively secreted into the distal tubule concentrating the urine
164
Explain the main stages of how the kidney tubules produce urine the is more concentrated than the blood in the Collecting Duct (5/5)
Permeability of the collecting duct to water is also controlled by the level of ADH
if walls are permeable water moves out by osmosis into the concentrated tissue fluid of the renal medulla
urine becomes more concentrated
water can be removed by osmosis along the length of the collecting duct
as the concentration of the tissue fluid of the medulla increases from cortex to pyramids maintaining a concentration gradient
this produces urine very hypertonic to blood
165
What is the main organ of osmoregulation
Kidney
166
What type of feedback is the controlling of urine concentration/water loss
Negative feedback
(pg 429)
167
Where is ADH produced and where is it secreted into to be stored
Produced by Hypothalamus
Secreted and stored in posterior Pituitary gland
168
What does ADH do
Increases the permeability of the distal convoluted tubule and collecting duct to water
169
What does ADH bind to, where does it bind, and what is the knock on effect
Binds to receptors, on the cell membrane, causing the formation of cAMP to act as a second messenger
170
What are the events that occur after ADH has bound to its receptor and cAMP is formed and relays the received signal
Vesicles in cells lining collecting duct fuse with cell membrane of the cells with the tissue fluid in the medulla
Membranes of these vesicles contain protein-based water channels (aquaporins) and when they are inserted into the cell surface membrane, they make it permeable to water
This provides a route for water to move out of the tubule cells into the tissue fluid of the medulla and the capillaries by osmosis
171
What is the trend between ADH levels and number of aquaporins inserted into cell membrane
More ADH present, the more aquaporins are inserted into the cell membranes
172
What happens when levels of ADH fall
Levels of cAMP also fall, Water channels are removed from tubule cell membranes and enclosed in vesicles again so no water can leave
173
Is ADH produced in water scarcity or water surplus
Water scarcity - produces more concentrated urine to conserve water
174
What are the receptors that control negative feedback of water concentrations and how does it work
Osmoreceptors
Sensitive to the concentration of inorganic ions in the blood and are linked to the release of ADH
175
Describe the events in the renal system when water is in short supply
Concentration of inorganic ions in the blood rises and water potential of blood and tissue fluid becomes more negative
Detected by osmoreceptors in hypothalamus
Sends nerve impulses to posterior pituitary gland which in turn releases stored ADH into the blood
ADH binds to receptors of cells lining DCT and collecting duct, increasing the permeability of the tubules to water
Water leaves the filtrate in the tubules and passes into the blood in the surrounding capillary network
Small volume of Concentrated urine is produced
176
Describe the events in the renal system when water is in excess/surplus
Concentration of inorganic ions in the blood decreases, blood becomes more dilute and its water potential becomes less negative
Change is detected by osmoreceptors in hypothalamus
Nerve impulses to the posterior pituitary gland are reduced or stopped and so the release of ADH by the pituitary gland is inhibited
Little reabsorption of water can take place because the walls of the collecting duct remain impermeable to water
Concentration of blood is maintained,
Large amount of dilute urine is produced
177
Read page 430
do it
178
In cool weather, you may produce more urine than on a similar day in hot weather. Suggest a reason for this
In cool weather you sweat less
so less water lost to keep coo
179
There is a rare condition called diabetes insipidus where the body doesnt make ADH (or the kidneys do not respond to ADH)
A) what do you expect the symptoms to be
B) Explain what is happening in the kidney tubules in a patient with diabetes insipidus
C) Suggest how you might treat mild diabetes insipidus (when some ADH is made) and severe diabetes insipidus (where no ADH is made)
A)
Production of large quantities of very dilute urine
dehydration of body tissues
osmotic effects on cells constant thirst
B)
Kidney tubules impermeable to water
protein-based water channels remain in vesicles
no ADH means no second messengers so no cascade to place water channels in membrane
therefore no water moves out of distal convoluted tubule or collecting duct by osmosis
all fine control over osmoregulation lost
C)
managing water intake to conditions and activities
so don’t need any fine control of
water in body
severe – artificial ADH to replace the natural hormone
180
What is found in urine
Water, urea, mineral salts, chemicals, hormones and any toxins
181
If a person has type 1 or type 2 diabetes, what will be present in their urine which is a symptom
Glucose
182
If a person has muscle damage, what will be present in their urine
Large amounts of creatinine
183
What is the hormone that is produced when the human embryo implants in the uterus
human chorionic gonadotrophin - hCG
184
Describe how pregnancy was tested until the 1960s
Injecting urine into an African clawed toad
if she was pregnant, the hCG triggered egg production in the toad within 8-12 hours of the injection - couldn't be used until woman was several weeks pregnant
185
What are the new pregnancy tests relying on
Monoclonal antibodies, still tests for hCG in urine
Can be detected within hours of implantation
186
Describe the events in how monoclonal antibodies are made
Mouse is injected with hCG to make the appropriate antibody
The Beta cells make the required antibody are then removed from mouse and fused with a myeloma (type of cancer cell) so it divides rapidly
Produces a hybridoma, which reproduce rapidly resulting in millions of living factories making the desired antibody
Antibodies are then collected, purified and used in a variety of ways
187
What are the main stages in a pregnancy test
The wick is soaked in the first urine passed in the morning - this will have the highest levels in hCG
Test contains mobile monoclonal antibodies that have very small coloured beads attached to them. They will only bind to hCG. if a woman is pregnant the hCG in the urine binds to the mobile monoclonal antibodies and forms a complex
Urine caries on along the test structure until it reaches a window
Here there are immobilised monoclonal antibodies arranged in a line or a pattern such as a +
Urine continues up through the test to a second window
Another line of immobilised monoclonal antibodies that bind only to the mobile antibodies regardless of whether they are bound to hCG or not. Coloured line forms regardless of whether the woman is pregnant or not
Woman is pregnant if two coloured paterns appear, if she isnt pregnant, only one appears
188
What do anabolic steroids do
Mimic the action of male sex hormone - testosterone - and they stimulate growth of muscles
189
How can scientists test for an athlete or body builder using anabolic steroids
Steroids excreted by urine
Test urine using gas chromatography and mass spec
190
How can scientists test if a person has used drugs eg. alcohol, cannabis etc...
Drugs and metabolites (breakdown products of drugs) are filtered through the kidney and stored in the bladder, so traces can be found in urine
Sample taken will be split into two. One will be tested by an immunoassay, using monoclonal antibodies to bind to the drug or breakdown product
If this is positive, sample will be run through gas chromatograph and mass spec
191
Why is urine so useful for diagnostic tests
Urine samples easy to get
non-invasive
urine contains drugs or metabolites excreted from
the kidney and stored in bladder so concentrated and can show up some time after drug use (they are
removed relatively rapidly from the blood
192
The professional bodies of different sports carry out random urine testing both during training and competition. The winning athletes always have their urine tested.
A) Urine samples are divided into two and only one of them is tested initially. Explain why
B) Why do you think urine tests are carried out at random during training as well as at competitions
A)
a Allows confirmation tests to be done
if immunoassay indicates an illegal substance, a second
urine sample taken at exactly the same time is available
allows further testing using a different
technique – usually gas chromatography or mass spectrometry
to confirm the initial finding
B)
Drugs can be used to improve performance/build muscles/increase RBC count etc during training
and then stopped long enough before a major competition to disappear from the system
while the
anatomical and physiological benefits remain
Random testing reduces likelihood that athlete will
use illegal substances as they don’t know when they will be tested, also more likely to be caught if
they are cheating
193
What are some reasons why a kidney may fail
Infections - where structure of podocytes and the tubules themselves may be damaged or destroyed
Raised blood pressure - can damage structure of epithelial cells and basement membrane of the Bowmans capsule
Genetic conditions - such as polycystic kidney disease where the healthy kidney tissue is replaced by fluid-filled cysts or damaged by pressure from cysts
194
What are some symptoms that a kidney is infected or affected by high blood pressure
Protein in the urine - If the basement membrane of the Bowman's capsule are damaged, they no longer act as filters and large plasma proteins can pass into the filtrate and are passed out in the urine
Blood in the urine - Symptom filtering process isnt working
195
What are symptoms that kidneys have failed completely
Concentrations of urea and mineral ions build up - effects include
Loss of electrolyte balance - body cannot excrete excess sodium, potassium and chloride ions. This causes osmotic imbalances in the tissues and eventual death
Buildup of toxic urea in the blood - if the kidneys fail, the body cannot get rid of urea and it can poison the cells
High blood pressure - kidneys play an important role in controlling the blood pressure by maintaining the water balance of the blood. If the kidneys fail, the blood pressure increases and this can cause a range of health problems including heart problems and strokes
Weakened bones - calcium/phosphorus balance in the blood is lost
Pain and stiffness in joints as abnormal proteins build up in the blood
Anaemia - the kidneys are involved in the production of a hormone called erythropoietin that stimulates the formation of red blood cells. The kidneys fall it can reduce the production red blood cells causing tiredness and lethargy
196
What is the Glomerular Filtration rate (GFR) used for
To indicate kidney disease
197
How is GFR measured
Indirectly - Test shows the levels of creatinine in the blood
198
What is creatinine
A breakdown product of muscle and is used to give an estimated glomerular filtration rate (eGFR)
199
What are the units for eGFR
cm3/min-1
200
What do rising levels of creatinine in the urine show
Kidneys are failing
201
What factors need to be taken into account in measuring healthy GFR
Age
Gender (men have more muscle than women so they have more creatinine)
etc...
202
At what GFR for what period of time indicates moderate to severe chronic kidney disease
lower than 60 for more than 3 months
203
Even for very elderly people, what is the lowest threshold a GFR should be for a healthy kidney
70
204
What is indicated by a GFR of below 15
Kidney failure
205
How is kidney failure treated?
Renal Dialysis
Transplant
206
What are the two types of dialysis
Haemodialysis and peritoneal dialysis
207
How does haemodialysis work
Blood leaves the patients body from an artery and flows into the dialysis machine, where it flows between partially permeable dialysis membranes
Membranes mimic basement membrane of the bowmans capsule
On the other side of the membrane is the dialysis fluid. During dialysis it is vital that patients lose the excess urea and mineral ions that have built up in the blood. It is equally important that they do not lose useful substances such as glucose and mineral ions
Contains normal plasma levels of glucose to ensure no net movement occurs
Contains normal plasma levels of mineral ions so any excess mineral ions diffuse out of the blood
Dialysis takes 8 hours, repeated regularly and relies on diffusion down conc. gradients, no active transport
(pg 434)
208
What must patients on dialysis do
Repeat regularly several times a week for many hours
Monitor diets carefully - eating relatively little protein and salt and monitoring fluid intake
209
How does Peritoneal dialysis work
Makes use of the natural dialysis membrane is formed by the lining of the abdomen - the peritoneum
It is normally done at home, while patients carry on with a normal life will it takes place.
The dialysis fluid is introduced into the abdomen using a catheter. It is left for several hours for dialysis to take place across the peritoneal membranes, so that urea and excess mineral ions pass out of the blood capillaries into the tissue fluid and out across the peritoneal membrane into the dialysis fluid.
The fluid is then drained off and discarded, leaving the blood balanced again and the Urea and excess minerals removed.
(pg 435)
210
What happens in a kidney transplant
A single healthy kidney from a donor is placed within the body.
Blood vessels are joined and the ureter of the new kidney is inserted into the bladder
(pg 436)
211
What is the main issue with transplanted organs
Rejecting the organ
212
What happens during an organ rejection
The antigens on the donor organ differ from the antigens on the cells of the recipient and the immune system is likely to recognise this
This will lead to the immune system attacking and destroying the kidney
213
How can the risk of rejecting an organ transplant
Match the antigens and tissue type as close as possible
Given immunesuppressant drugs
214
What is the disadvantage for taking immunosuppressant drugs to help reduce the risk of rejecting an organ transplant
On them for rest of their lives
Prevent patients from responding effectively to infectious diseases
215
If a transplanted kidney fails, which most do after around 10 years, what happens to the patient
They return to dialysis and wait until another suitable replacement is found
216
Positives for dialysis
More readily available
Allows patients to live relatively normal life
217
Negatives for dialysis
Expensive in the long-term
Regular sessions needed on the machine
Patients need to monitor diet carefully
Can damage the body in the long term
218
Positives for transplant
Free from restrictions that come with regular dialysis sessions and dietary monitoring
219
Negatives of transplants
Lack of donors
Many Fail after a few years
Operations
immunosuppressant drugs
Rejection of organ
220
What is the main source of donor kidneys in the UK
People who die suddenly eg. from road accidents, strokes and heart attacks
Online donor register/ donor card
221
What was one solution that scientists have developed to possibly ease the demand for transplants
Growing functioning embryonic kidney tissue from stem cells
222
Why is kidney failure such a threat to life
Kidneys remove toxins and maintain water and electrolyte balance
if they fail, toxins are not removed and may cause damage
if water or electrolyte balance is too far away from normal cells may suffer osmotic damage
223
On what process does dialysis depend
Diffusion
224
Sometimes a live donor, usually a close family member, or donate a kidney. These transplants have a higher rate of success than normal transplants from dead unrelated donors.
A) suggest two reasons why life transfers from a close family member have a high success rate, the normal transplants
B) why do you think that live donor transplants are still the minority?
A)
Live organ taken straight from donor to recipient
alive all the time so no risk of tissue damage
tissue match likely to be close
B)
Family members not necessarily close tissue match
living donors donating to strangers rare
involves risk of surgery for donor
and risk if they ever have kidney problems as they are left with only one functioning kidney
225
Explain the importance of dialysis fluid containing no urea and normal plasma levels of salt, glucose and minerals
Important to set up diffusion gradients between blood and dialysis fluid so excess salt, minerals, urea, etc move out of the blood into the fluid across the dialysis membrane
glucose, salt, and minerals present in plasma so want levels to equilibrate with dialysis fluid
hence normal plasma levels in dialysis fluid
as much urea as possible needed to be removed so the steepest possible diffusion gradient is required to ensure urea moves out of blood
226
Both blood and dialysis fluid are constantly circulating through the dialysis machine. Explain why it is important that the blood and dialysis fluid flow in opposite directions and that there is a constant circulation of dialysis fluid
Maximises exchange by maintaining the best possible diffusion gradients
flowing in opposite directions maintains a countercurrent exchange,
where the exchange continues all the way along the membrane because there is always a gradient between the plasma and the dialysis fluid
227
Why can patients with kidney failure eat and drink what they like during the first few hours of dialysis
Any urea formed, salt taken in etc, will pass into blood and be removed during dialysis session
however as dialysis session progresses, excess protein will not be processed in body in time to be converted into urea and removed before dialysis session ends
