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BIOLOGY A LEVEL > CHAPTER 15 - HOMEOSTASIS > Flashcards

CHAPTER 15 - HOMEOSTASIS Flashcards

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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

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2
Q

What is Homeostasis

A

A dynamic equilibrium, with small fluctuations over a narrow range of conditions

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3
Q

What do sensory receptors do

A

Detect changes in the internal and external environment of an organism

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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

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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

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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)

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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)

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8
Q

What is an example of negative feedback

A

Temperature control
Water balance

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9
Q

What are some examples of positive feedback

A

Blood clotting cascade
Childbirth (pg 407)

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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

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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

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12
Q

What is homeostasis

A

The maintenance of a dynamic equilibrium

within narrow ranges in the body

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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

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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

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15
Q

What is thermoregulation

A

The maintenance of a relatively constant core body temperature to maintain optimum enzyme activity

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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

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17
Q

What are ectotherms

A

Organisms that use their surroundings to warm their bodies

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18
Q

What does ectotherm directly translate to

A

Outside heat - hence regulate heat from outside

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19
Q

What are some examples of ectotherms

A

All invertebrates as well as Fish, Amphibians and reptiles

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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.

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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

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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

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23
Q

What does endotherm directly translate to

A

Inside heat

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24
Q

What do behavioural responses in ectotherms do

A

Allows the organism to increase or reduce the radiation they absorb from the sun

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25
Q

How do many ectotherms warm up and why - behaviourally

A

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

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26
Q

Why do lizards need to bask in the sun

A

To get to the temperature to warm up their metabolic processes to move fast and to hunt prey

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27
Q

Why do Insects need to bask in the sun

A

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

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28
Q

As well as Basking in the sun, how else do ectotherms warm up behaviourally

A

Thermal conduction by pressing their bodies against hot ground

Warmer through metabolic processes

Contracting and vibrating muscles to warm them up

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29
Q

How do ectotherms cool their body temperature

A

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

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30
Q

What other responses to regulate temperature to ectotherms have, besides behavioural

A

Physiological

Anatomical

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31
Q

How does colour of the skin help lizards to regulate body temperature physiologically

A

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

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32
Q

How else do ectotherms regulate their temperature physiologically, besides skin colour

A

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

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33
Q

How are ectotherms better adapted than endotherms

A

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

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34
Q

Example of an ectotherm

A

Namaqua Chameleon - model ectotherm - pg 410 LOOK UP

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35
Q

What is an ectotherm

A

Animals that use heat from their surroundings to warm their bodies

so their core body temperature is heavily dependent on their environment

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36
Q

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

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

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37
Q

In any homeostatic system, what are needed to detect a change in the internal environment

A

Receptors

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38
Q

Where are the peripheral temperature receptors located

A

The Skin

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39
Q

What is the temperature receptor in the body which detects blood temperature in the body

A

Hypothalamus

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40
Q

What is the job of the hypothalamus

A

Maintain dynamic equilibrium within 1 degrees celsius of 37 degrees

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41
Q

What do endotherms use their internal exothermic metabolic activities to do

A

Keep them warm

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42
Q

What do endotherms use energy-requiring physiological responses to do

A

Cool down

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43
Q

What behavioural responses do endotherms have to regulate body temperature

A

Basking in the sun
Pressing themselves into warm surfaces
Wallowing in water and mud to cool down
Digging burrows
Hibernation and Aestivation

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44
Q

What behavioural adaptations do humans have to maintain body temperature

A

Clothes are worn to stay warm
Houses are built then heated up or cooled down

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45
Q

What are the physiological responses endotherms have to overheating

A

Vasodilation
Increased sweating
Reducing insulation of hair or feathers

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46
Q

What is Vasodilation and how does it help cool down an endotherm

A

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)

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47
Q

How does increased sweating cool down an endotherm

A

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

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48
Q

How does reducing the insulating effect of hair or feathers cool an organism down

A

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

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49
Q

What anatomical adaptations do endotherms living in warm climates have to cool down

A

Large surface area: Volume ratio to maximise cooling (eg. include large ears and wrinkly skin)

pale fur or feathers to reflect radiation

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50
Q

What are the physiological responses endotherms have to help warm up

A

Vasoconstriction
Decreased sweating
Rising the body hair or feathers
Shivering

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51
Q

How does vasoconstriction help keep an endotherm warm

A

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

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52
Q

How does decreased sweating help warm up an endotherm

A

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.

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53
Q

How does shivering help warm an endotherm up

A

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.

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54
Q

What anatomical adaptations do endotherms living in cold climates have to keep warm

A

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

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55
Q

Example of an endotherm in a hot climate

A

Desert (Fennec) fox, Camel etc..

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56
Q

Example of an endotherm living in a cold climate

A

Polar bear, Whale etc…

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57
Q

What are the complex homeostatic mechanisms controlled by

A

Hypothalamus

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58
Q

What are the two control centres in the hypothalamus called

A

Heat loss centre, Heat Gain centre

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59
Q

How does the Heat loss centre work

A

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

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60
Q

How does the Heat gain centre work

A

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

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61
Q

Read the feedback diagram on page 414 - fairly basic but give it a read

A

do it preferably now pls

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62
Q

Why is the temperature so important to both ectotherms and endotherms

A

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

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63
Q

Explain how the role of evaporation of water in thermoregulation differs between ectotherms and endotherms

A

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

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64
Q

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

A

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

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65
Q

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

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

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66
Q

What is Excretion

A

The removal of the waste products of the metabolism from the body

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67
Q

What are the main metabolic waste products in mammals, what are they the products of and how are they excreted

A

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

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68
Q

Is the liver fast or slow growing

A

Fast growing, damaged areas can generally regenerate very quickly

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69
Q

Does the liver have a high or low blood supply

A

Very high - 1 dm3 of blood flows through it per minute

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70
Q

How is the liver supplied with oxygenated blood

A

Hepatic artery - From heart
Hepatic portal vein - From Intestines

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71
Q

What is the name of the blood vessel that returns blood to the heart from the liver

A

Hepatic vein

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72
Q

What is carried in the blood of the hepatic portal vein

A

The products of digestion straight from the intestines to the liver

Starting point for many metabolic activities in the liver

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73
Q

What are liver cells also called

A

Hepatocytes

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74
Q

What are some features of hepatocytes

A

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

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75
Q

Where does the blood from the hepatic artery and hepatic portal vein mix

A

Sinusoids - channels/ spaces surrounded by hepatocytes

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76
Q

Why does the blood from the hepatic artery and the hepatic portal vein mix in the sinusoids

A

It increases the oxygen content in the blood of the hepatic portal vein, applying the hepatocytes with enough oxygen for their needs

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77
Q

Where are Kupffer cells found and what do they do

A

Found in the sinusoids in the liver, acts as resident macrophages of the liver, ingesting foreign particles and helping protect against disease

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78
Q

Where do the hepatocytes secrete bile from the breakdown of blood into

A

Spaces in between sinusoids called canaliculi, which drain into the bile duct which takes it to the gall bladder

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79
Q

What are some functions of the liver (~500)

A

Carbohydrate metabolism
Deamination of excess amino acids
Detoxification

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80
Q

How does the liver regulate carbohydrate metabolism

A

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

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81
Q

What is transamination and where does it happen

A

The conversion of one amino acid into another, in the liver

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82
Q

What is deamination

A

The removal of an amine group from a molecule

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83
Q

Can the body store excess proteins or amino acids?

A

No, it is deaminated and the molecule (minus -NH2/3) is sent to respiration

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84
Q

What happens to the ammonia after deamination occurs

A

Converted to urea, which is highly toxic in high concentrations so it will be excreted in urine

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85
Q

What is the ornithine cycle

A

The ammonia produced from the deamination of proteins converted into urea by a set of enzyme-controlled reactions

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86
Q

Describe the events in the Ornithine cycle

A

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

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87
Q

What toxins are commonly broken down in the liver

A

Alcohol and drugs

Or other potentially poisonous substances, usually formed from metabolic pathways

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88
Q

What is an example of the liver breaking down a by-product of a metabolic pathway

A

Breakdown of Hydrogen Peroxide, by enzyme catalase, converting it into oxygen and water
2H2O2 –> 2H2O + O2

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89
Q

What is an example of the liver detoxifying a substance

A

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

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90
Q

Many people use the term excretion to describe defecation. Why is this not entirely accurate?

A

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

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91
Q

Read page 418 on understanding pictures of the liver and 419 on cirrhosis of the liver

A

Urgent do it

92
Q

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) 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
Q

Explain how the structure of the liver is adapted for its function in the body

A

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
Q

Why do you think the liver is particularly affected by excess drinking

A

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
Q

Why is a build-up of fatty tissue a common symptom of excess drinking

A

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
Q

Where are the kidneys located

A

Back of the abdominal cavity

97
Q

What are the kidneys surrounded by

A

A layer or thick protective fat and a layer of fibrous tissue

98
Q

What homeostatic roles does the kidney have in the body

A

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
Q

What blood vessel supplies the Kidney with blood

A

The renal arteries which branch off from the abdominal aorta

100
Q

Which blood vessel does blood that has circulated through the kidneys leave from

A

Renal Vein, into the inferior vena cava

101
Q

How much blood does the kidney filter per day

A

180 dm3

All of the body’s blood passes through the kidneys in an hour

102
Q

How much urine does the kidney produce per day

A

1-2 dm3 (depending on many factors)

103
Q

What are the filtering units in the kidney

A

Nephrons (millions of them)

104
Q

What is the sterile liquid produced by the kidney tubules called?

A

Urine

105
Q

What tubes does urine pass out of the kidneys from

A

Ureters

106
Q

What is the muscular sac that collects the urine

A

The bladder - stores 400-600 cm3 of urine

107
Q

What happens when the bladder is full

A

The sphincter at the exit to the bladder opens and the urine passes out of the body down the urethra

108
Q

What are the 3 main areas of the kidney

A

Cortex (not in middle ironically),
medulla (in middle) and
pelvis (latin for basin)

(pgs 420 and 421)

109
Q

What is the renal cortex

A

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
Q

What is the Renal medulla

A

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
Q

What is the renal pelvis

A

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
Q

What happens in the nephrons

A

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
Q

How long is each nephron and how many are there in each kidney

A

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
Q

What is a nephron comprised of

A

Glomerulus
Bowmans capsule
Proximal convoluted tubule
Loop of Henle
Distal Convoluted tubule
Collecting duct

115
Q

Where are nephrons located in the kidney

A

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
Q

What is the Bowmans capsule

A

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
Q

What is the glomerulus

A

A tangle of capillaries in the nephrons, with blood entering it from the renal artery

118
Q

What is the blood supply to a glomerulus and what does It leave by

A

Blood from branch of renal artery enters glomerulus through the afferent arteriole and leaves via the efferent arteriole

119
Q

What is the Proximal convoluted tubule

A

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
Q

What is a loop of Henle

A

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
Q

What is the distal convoluted tubule

A

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
Q

What is the collecting duct

A

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
Q

How does blood leave the nephron site

A

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
Q

What is the blood composition like after it has left the kidney

A

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
Q

What is ultrafiltration

A

The first stage in the removal of nitrogenous waste and osmoregulation of the blood

126
Q

What is formed due to the structure of the glomerulus and Bowmans capsules

A

tissue fluid in the capillary beds of the body

127
Q

Describe how the first stage of ultrafiltration works in the glomerulus

A

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
Q

What do the Bowmans capsule have behind their basement layer

A

Podocytes, which act as an additional filter

129
Q

What do podocytes have which make them specialised

A

Extensions called pedicels that wrap around the capillaries forming slits

130
Q

What is the job of podocytes

A

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
Q

What does the filtrate that enters the Bowmans capsule contain

A

Glucose, salt, urea and other substances in exactly the sae concentrations as they are in the blood plasma

132
Q

What is the glomerular filtration rate

A

The volume of blood that is filtered through the kidneys in a given time

133
Q

What is the ultra filtrate compared to the blood plasma

A

Hypotonic - less concentrated than

134
Q

What is the main function of the nephron after the bowman’s capsule

A

To return most of the filtered substances back into the blood

135
Q

What is moved back into the body, where and how

A

Glucose, amino acids, vitamins and hormones

In the proximal convoluted tubule

By active transport

136
Q

How are Sodium chloride (ions) reabsorbed - process

A

Sodium ions removed back into the blood by active transport and chloride ions and water follow passively down concentration gradients

137
Q

What adaptions do the cells lining the proximal convoluted tubule have

A

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
Q

Where do substances diffuse to after they are removed from the nephron

A

The extensive capillary network which surrounds the tubules down steep concentration gradients

139
Q

How are the steep concentration gradients maintained in the capillaries of the lungs

A

Constant flow of blood

140
Q

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

A

Isotonic - same concentration

141
Q

What does the loop of Henle allow for

A

The production of more concentrated urine than their own blood

142
Q

What is essential to how the loop of hence functions

A

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
Q

What are the changes that take place in the descending limb of the loop of henle dependant on

A

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
Q

Where dos the balancing of water take place

A

The distal convoluted tubule and the collecting duct

145
Q

What does the permeability of the walls of the collecting duct and DCT depend on

A

Levels of ADH in the body

146
Q

How are the cells that line the distal convoluted tubule adapted to their function

A

Many mitochondria to carry out active transport

147
Q

If the body lacks salt, how does the DCT respond to counteract this

A

Sodium ions will be actively pumped out of the tubule with chloride ions following down an electrochemical gradient

148
Q

Where is the concentration and volume of the urine produced determined

A

Collecting Duct

149
Q

How does water move out of the collecting duct and what is the result on the urine concentration

A

Leaves my diffusion/osmosis as it passes through renal medulla,

More concentrated urine

150
Q

As a result of water leaving the collecting duct, what are the knock on effects

A

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
Q

What is the general trend with the loop of henle and an animals ability to produce concentrated urine

A

The longer the loop of henle, the more concentrated the urine can be produced

152
Q

Give 3 examples of how the kidneys are well adapted for their functions in the body

A

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
Q

How much blood is filtered over 24 hours through the kidneys, and what percentage of this filtrate is lost to the body as urine

A

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
Q

What is ultrafiltration?

A

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
Q

What would you expect to see in a normal glomerular filtrate?

A

Water, urea, glucose, amino acids, mineral ions – the same concentrations as the blood without the red blood cells and the large plasma proteins

156
Q

Kidney infections can damage the lining of the Bowmans capsule. How might this result in protein appearing in the urine.

A

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
Q

Approximately how much more urea is there in urine than in blood

A

There is around 1000 times more urea in the urine than in the blood

158
Q

Suggest 3 possible factors that might affect the amount of urea in the urine

A

Amount of protein eaten, amount of exercise done, blood pressure levels,
activity of the kidneys etc…

159
Q

Why do the factors that affect the urea concentration in urine not affect the urea concentration of the blood

A

Because urea is constantly removed from the blood by the kidneys

160
Q

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)

A

Active transport of substances back into capillaries

water follows by osmosis

through permeable walls up to 80% of the filtrate reabsorbed

161
Q

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)

A

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
Q

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)

A

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
Q

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)

A

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
Q

Explain the main stages of how the kidney tubules produce urine the is more concentrated than the blood in the Collecting Duct (5/5)

A

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
Q

What is the main organ of osmoregulation

A

Kidney

166
Q

What type of feedback is the controlling of urine concentration/water loss

A

Negative feedback

(pg 429)

167
Q

Where is ADH produced and where is it secreted into to be stored

A

Produced by Hypothalamus

Secreted and stored in posterior Pituitary gland

168
Q

What does ADH do

A

Increases the permeability of the distal convoluted tubule and collecting duct to water

169
Q

What does ADH bind to, where does it bind, and what is the knock on effect

A

Binds to receptors, on the cell membrane, causing the formation of cAMP to act as a second messenger

170
Q

What are the events that occur after ADH has bound to its receptor and cAMP is formed and relays the received signal

A

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
Q

What is the trend between ADH levels and number of aquaporins inserted into cell membrane

A

More ADH present, the more aquaporins are inserted into the cell membranes

172
Q

What happens when levels of ADH fall

A

Levels of cAMP also fall, Water channels are removed from tubule cell membranes and enclosed in vesicles again so no water can leave

173
Q

Is ADH produced in water scarcity or water surplus

A

Water scarcity - produces more concentrated urine to conserve water

174
Q

What are the receptors that control negative feedback of water concentrations and how does it work

A

Osmoreceptors

Sensitive to the concentration of inorganic ions in the blood and are linked to the release of ADH

175
Q

Describe the events in the renal system when water is in short supply

A

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
Q

Describe the events in the renal system when water is in excess/surplus

A

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
Q

Read page 430

A

do it

178
Q

In cool weather, you may produce more urine than on a similar day in hot weather. Suggest a reason for this

A

In cool weather you sweat less

so less water lost to keep coo

179
Q

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

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
Q

What is found in urine

A

Water, urea, mineral salts, chemicals, hormones and any toxins

181
Q

If a person has type 1 or type 2 diabetes, what will be present in their urine which is a symptom

A

Glucose

182
Q

If a person has muscle damage, what will be present in their urine

A

Large amounts of creatinine

183
Q

What is the hormone that is produced when the human embryo implants in the uterus

A

human chorionic gonadotrophin - hCG

184
Q

Describe how pregnancy was tested until the 1960s

A

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
Q

What are the new pregnancy tests relying on

A

Monoclonal antibodies, still tests for hCG in urine

Can be detected within hours of implantation

186
Q

Describe the events in how monoclonal antibodies are made

A

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
Q

What are the main stages in a pregnancy test

A

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
Q

What do anabolic steroids do

A

Mimic the action of male sex hormone - testosterone - and they stimulate growth of muscles

189
Q

How can scientists test for an athlete or body builder using anabolic steroids

A

Steroids excreted by urine

Test urine using gas chromatography and mass spec

190
Q

How can scientists test if a person has used drugs eg. alcohol, cannabis etc…

A

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
Q

Why is urine so useful for diagnostic tests

A

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
Q

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)
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
Q

What are some reasons why a kidney may fail

A

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
Q

What are some symptoms that a kidney is infected or affected by high blood pressure

A

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
Q

What are symptoms that kidneys have failed completely

A

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
Q

What is the Glomerular Filtration rate (GFR) used for

A

To indicate kidney disease

197
Q

How is GFR measured

A

Indirectly - Test shows the levels of creatinine in the blood

198
Q

What is creatinine

A

A breakdown product of muscle and is used to give an estimated glomerular filtration rate (eGFR)

199
Q

What are the units for eGFR

A

cm3/min-1

200
Q

What do rising levels of creatinine in the urine show

A

Kidneys are failing

201
Q

What factors need to be taken into account in measuring healthy GFR

A

Age
Gender (men have more muscle than women so they have more creatinine)
etc…

202
Q

At what GFR for what period of time indicates moderate to severe chronic kidney disease

A

lower than 60 for more than 3 months

203
Q

Even for very elderly people, what is the lowest threshold a GFR should be for a healthy kidney

A

70

204
Q

What is indicated by a GFR of below 15

A

Kidney failure

205
Q

How is kidney failure treated?

A

Renal Dialysis
Transplant

206
Q

What are the two types of dialysis

A

Haemodialysis and peritoneal dialysis

207
Q

How does haemodialysis work

A

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
Q

What must patients on dialysis do

A

Repeat regularly several times a week for many hours

Monitor diets carefully - eating relatively little protein and salt and monitoring fluid intake

209
Q

How does Peritoneal dialysis work

A

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
Q

What happens in a kidney transplant

A

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
Q

What is the main issue with transplanted organs

A

Rejecting the organ

212
Q

What happens during an organ rejection

A

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
Q

How can the risk of rejecting an organ transplant

A

Match the antigens and tissue type as close as possible

Given immunesuppressant drugs

214
Q

What is the disadvantage for taking immunosuppressant drugs to help reduce the risk of rejecting an organ transplant

A

On them for rest of their lives

Prevent patients from responding effectively to infectious diseases

215
Q

If a transplanted kidney fails, which most do after around 10 years, what happens to the patient

A

They return to dialysis and wait until another suitable replacement is found

216
Q

Positives for dialysis

A

More readily available

Allows patients to live relatively normal life

217
Q

Negatives for dialysis

A

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
Q

Positives for transplant

A

Free from restrictions that come with regular dialysis sessions and dietary monitoring

219
Q

Negatives of transplants

A

Lack of donors
Many Fail after a few years
Operations
immunosuppressant drugs
Rejection of organ

220
Q

What is the main source of donor kidneys in the UK

A

People who die suddenly eg. from road accidents, strokes and heart attacks

Online donor register/ donor card

221
Q

What was one solution that scientists have developed to possibly ease the demand for transplants

A

Growing functioning embryonic kidney tissue from stem cells

222
Q

Why is kidney failure such a threat to life

A

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
Q

On what process does dialysis depend

A

Diffusion

224
Q

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

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
Q

Explain the importance of dialysis fluid containing no urea and normal plasma levels of salt, glucose and minerals

A

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
Q

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

A

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
Q

Why can patients with kidney failure eat and drink what they like during the first few hours of dialysis

A

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

BIOLOGY A LEVEL (24 decks)

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