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GCSE AQA TRIPLE SCIENCE - Biology > GCSE AQA Biology - Topic 5 - HOMEOSTASIS AND RESPONSE > Flashcards

GCSE AQA Biology - Topic 5 - HOMEOSTASIS AND RESPONSE Flashcards

1
Q

What is homeostasis

A

The regulation of the internal conditions of a cell or organism to maintain optimum conditions for functions in response to internal and external changes

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2
Q

Identify 3 ways which the body uses homeostasis to maintain optimal conditions for enzyme action and cell functions

A
  • Control of blood glucose concentration - Control of body temperature - Control of water levels
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3
Q

Homeostasis consists of automatic control systems; what is the function of automatic control systems

A

They recognise when there is a change from optimal conditions, and so they send a signal to reverse that change, so that the levels go back to normal

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4
Q

What 2 responses do automatic control systems have

A
  • Nervous responses - Chemical responses
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5
Q

Identify 3 features of an automatic control system

A
  • Receptor cells - Co-ordination centre - Effector
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6
Q

What is the function of receptor cells

A

Detect changes in the environment (stimulus)

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7
Q

What is a stimulus

A

A change in the environment

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8
Q

What is the function of the coordination centre

A

It receives and processes the information from the receptor cells

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9
Q

Identify 3 examples of coordination centres

A
  • Spinal cord - The brain - The pancreas
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10
Q

What is an effector and what is its function

A

A muscle or a gland which carries out the response to restore the optimum level

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11
Q

Identify 2 methods of cell signalling in an automatic control system

A
  • The nervous system - The endocrine system
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12
Q

What is the function of the nervous system

A

The nervous system allows the body to react to its surroundings and coordinate actions in response to to stimuli

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13
Q

What are the 2 components of the nervous system

A
  • Central Nervous System (CNS) - Peripheral Nervous System (PNS)
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14
Q

What is the central nervous system

A

The brain and the spinal cord

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15
Q

What is the function of the central nervous system

A

It receives information from receptors and then coordinates a response

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16
Q

What is the peripheral nervous system

A

Nerves that cover the body, which run to and from the central nervous system

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17
Q

What is the function of a neurone/nerve cell

A

Carries electrical impulses from one point to another

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18
Q

Describe and explain how the nervous system works

A
  1. Receptor cells convert a stimulus into an electrical impulse 2. This electrical impulse travels along cells called sensory neurons to the central nervous system 3. Here, the information is processed and the appropriate response is coordinated, resulting in an electrical impulse being sent along motor neurons to effectors 4. The effectors carry out the response
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19
Q

Identify 2 examples of effectors

A
  • Muscles (contract) - Glands (releases hormones)
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20
Q

In the nervous system, which part is the coordination centre

A

The central nervous system

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21
Q

What is a reflex

A

An automatic response which takes place before you have time to think

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22
Q

What is a reflex action

A

A protective response to a stimulus where an impulse travels directly to the spinal cord and sends a message to the brain so that less damage occurs to the body

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23
Q

How is the decision making of a reflex different to decision making of other responses in the nervous system

A

There is no decision making by the conscious part of the brain, making them automatic and rapid

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24
Q

Why are reflex actions important

A

They are rapid and automatic, so the body can respond to stimuli quickly, which helps to avoid injuries

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25
Q

What is a reflex arc

A

The nerve pathway that underlies our unconscious reflexes, allowing vital responses to take place quickly

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26
Q

Describe the structure of a reflex arc

A
  1. A stimulus is detected by receptors 2. Electrical impulses pass from the receptor along a sensory neurone to the central nervous system 3. At the end of the sensory neurone there is a junction called a synapse, where a chemical is released and diffuses across to a relay neurone in the CNS, where it triggers an electrical impulse 4. The electrical impulse now passes across the relay neurone and reaches another synapse where another chemical is released, triggering an electrical impulse in a motor neurone 5. The electrical impulse passes down the motor neurone to an effector 6. The impulse reaches an effector resulting in the appropriate response
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27
Q

Describe the reflex arc when your finger touches a hot flame

A
  • The stimulus, which is the heat from the flame, is detected by the receptor in the skin - Electrical impulses pass from the receptor along a sensory neurone to the central nervous system - The electrical impulse passes through the synapse, where a chemical diffuses across to a relay neurone in the CNS and triggers an electrical impulse - The electrical impulse passes across the relay neurone and reaches another synapse, where a chemical is released and triggers an electrical impulse in a motor neurone - The electrical impulse passes down the motor neurone to the effector, which is a muscle - The response is the muscle contracting and pulling away from the heat
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28
Q

What is a synapse

A

The connection between two neurones

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29
Q

How does a nerve signal move across a synapse

A

The nerve signal is transferred by chemicals which diffuse across the gap, and set off a new electrical signal in the next neurone

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30
Q

Describe the practical which can be used to measure a person’s reaction time

A
  1. Person 1 sits on a chair with good upright posture, and then places the forearm of their dominant arm across the table, with their hand overhanging the edge 2. Person 2 holds a ruler vertically; the 0cm mark should be between person 1’s thumb and first finger 3. Person 2 drops the ruler at a random time 4. Person 1 has to catch the ruler with their thumb and first finger as quickly as possible when it drops 5. Person 2 records the measurement on the ruler that is level with the top of person 1’s thumb 6. The test is then repeated several times and a mean is calculated; you can convert these results to a reaction time by using a conversion table 7. This is then repeated but with person 1 testing the reaction time of person 2, so person 2 will catch the ruler
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31
Q

What is the independent, dependent, and control variable of the practical to find someone’s reaction time

A

IV; the person having their reaction time tested DV; the reaction time CV; starting distance between the thumb and the first finger, measuring the ruler at the top of the thumb, keep the conditions in the room the same (lighting and level of background noise)

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32
Q

In the experiment of measuring reaction time, what other independent variables could you investigate

A
  • The effect of practise; one person would catch the ruler a large number of times, and then you would look to see if the reaction time changes depending on the number of tries - Whether the reaction time depends on the hand catching the ruler; you would carry out the test with the dominant hand and then with the non dominant hand of the same person - Whether certain chemicals affect reaction time, such as caffeine, where you would drink a caffeinated substance 30 minutes before the experiment, then compare this reaction time with their normal reaction time
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33
Q

Identify the 3 different parts of the brain

A
  • Cerebral cortex - Cerebellum - Medulla
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34
Q

What are the functions of the cerebral cortex

A
  • Controls language - Controls memory - Controls consciousness
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35
Q

Where is the cerebral cortex

A

It is the outer part of the brain

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36
Q

What are the functions of the cerebellum

A
  • Controls balance - Co-ordinated movement
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37
Q

Where is the cerebellum

A

It is the rounded structure towards the back of the brain

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38
Q

What are the functions of the medulla

A
  • Controls heartrate - Controls breathing rate
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39
Q

Where is the medulla

A

In the brain stem in front of the cerebellum

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40
Q

Identify 3 reasons why studying the brain/treating brain damage is extremely difficult

A
  • The brain is protected by the skull and so it very tricky to access - The structures of the brain are extremely complex, so it is difficult to work out exactly which parts of the brain carry out specific functions - The brain is very delicate and easy to damage
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41
Q

Identify 3 ways that scientists use to investigate the brain

A
  • Studying patients who have suffered brain damage; by looking to see where the damage has taken place, they can try to link that part of the brain to its function - Electrically stimulating different parts of the brain to look at the effects on the persons behaviour, allowing you to narrow down specific regions to their functions - Use MRI scanning to look at which parts of the brain are most active during different activities
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42
Q

What is the eye

A

A sense organ containing receptors sensitive to light intensity and colour

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43
Q

What are the two functions of the eye

A
  • Accommodation to focus on near or distant objects - Adaptation to dim light
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44
Q

Identify 9 parts of the eye and where they are

A
  • Lens - Cornea - Suspensory ligaments - Ciliary muscles - Pupil - Optic nerve - Retina - Iris - Sclera
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45
Q

What is the cornea and what is its function

A

It is the transparent, curved layer at the front of the eye, which initially refracts light as it enters

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46
Q

What is the pupil and what is its function

A

It is the opening in the eye which allows light to enter

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47
Q

What is the iris and what is its function

A

The coloured part of the eye which controls the size of the pupil

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48
Q

What is the function of the lens

A

It is able to change shape to focus light onto the retina

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49
Q

What is the retina and what is its function

A

The layer of light sensitive cells found at the back of the eye, which is where light is focussed in the eye; it contains receptor cells (rod and cone cells) which allow us to detect light intensity and light colour

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50
Q

What two types of receptor cells make up the retina

A

Light sensitive rod and cone receptor cells

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51
Q

What are cone cells

A

Cells found in the retina that are sensitive to the colour of light, so allow us to see in colour, but they do not work well in low light conditions

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52
Q

What are rod cells

A

Cells in the retina that are more sensitive to light, but only allow us to see in black and white

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53
Q

What is the fovea

A

A point on the retina which is full of only cone cells

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54
Q

What is the optic nerve and what is its function

A

A nerve that leaves the eye and leads to the brain, which sends nerve signals from the rod and cone cells in the retina to the brain

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55
Q

What is the sclera and what is its function

A

The tough, white outer layer which supports the structures inside the eye; it is strong to prevent some damage to the eye

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56
Q

What are the ciliary muscles and what is their function

A

They attach the suspensory ligaments to the eye; they contract or relax to make the suspensory ligaments go slack or tight respectively

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57
Q

What are the suspensory ligaments and what is their function

A

They attach the lens to the ciliary muscles; they slacken or tighten to help change the shape of the lens

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58
Q

What is the function of the suspensory ligaments and ciliary muscles together

A

They allow us to focus on distant or near objects

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59
Q

Explain how the eye detects light

A
  1. Light rays pass through the cornea, which light is refracted 2. The light rays then pass through the pupil in the centre of the iris 3. The light rays then pass through the lens, which focusses the light rays onto the retina 4. The light rays are now focussed on the retina, and the receptor cells in the retina now send electrical impulses down the optic nerve to the brain, allowing you to detect light
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60
Q

What is the pupil reflex

A

When the size of the pupil changes in response to bright or dim light

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61
Q

What changes occur in the eye when in bright light and why

A
  • Circular muscles contract - Radial muscles relax - This makes the pupil constricted, reducing the amount of light entering the eye, which helps to avoid damage to the retina
62
Q

What changes occur in the eye when in dim light and why

A
  • Circular muscles relax - Radial muscles contract - This makes the pupil dilated, allowing more light to enter the eye to create a better image
63
Q

What is accommodation

A

The ability to change the shape of the lens to focus on near or distant objects

64
Q

How does accommodation work

A
  • The lens is surrounded by a circular muscle called the ciliary muscle. The ciliary muscle is connected to the lens by fibres which are called suspensory ligaments - By contracting or relaxing, the ciliary muscle can change the thickness of the lens - When the ciliary muscle contracts, the suspensory ligaments loosen, so the lens becomes thicker and refracts light rays more strongly - When the ciliary muscle relaxes, the suspensory ligaments are pulled tight, and so the lens is now pulled thin and only slightly refracts light rays
65
Q

Explain how the eye focuses on distant objects

A
  • The ciliary muscles relax - The suspensory ligaments are pulled tight - The lens is now pulled thin and is less rounded, so light rays are only slightly refracted - This enables light to focus correctly on the retina
66
Q

Explain how the eye focuses on near objects

A
  • Ciliary muscles contracts - This causes the suspensory ligaments to loosen - The lens becomes thicker and more rounded, and so refracts the light rays more strongly - This enables light rays to focus correctly on the retina
67
Q

What is myopia

A

Short sightedness, meaning they can focus on nearby objects but cannot focus on distant objects

68
Q

What 2 things can cause myopia/short sightedness

A
  • The eyeball is too long so the light is focused at a point in front of the retina - the lens is the wrong shape and so refracts light too much and so the light is focused at a point in front of the retina
69
Q

How can you treat myopia/short sightedness

A
  • It is corrected by using glasses with concave (diverging) lenses - This refracts light outwards and counteracts the over refraction of the eye lens, so that the light rays focus correctly on the retina
70
Q

What is hyperopia

A

Long sightedness, meaning they can focus on distant objects, but cannot focus on nearby objects

71
Q

What 2 things can cause hyperopia/long sightedness

A
  • The eyeball is too short, so the light is focused at a point behind the retina - The lens is the wrong shape and doesn’t refract the light enough so light is focused at a point behind the retina
72
Q

How can you treat hyperopia/long sightedness

A
  • It is corrected using glasses with a convex (converging) lens - The lens refracts the light rays so they can focus correctly on the retina
73
Q

Identify and explain 3 alternative methods for treating vision defects

A
  • Contact lenses; these lenses sit on the eyeball and refract the light in the same way as glasses - Laser eye surgery; changes the shape of the cornea so it refracts the light to a greater or lesser extent - Replacement lens surgery; the lenses inside the eyes can be replaced using an artificial lens
74
Q

What is negative feedback

A

A mechanism in the body where changes to conditions cause an action to reverse the change, to keep conditions stable

75
Q

What 2 things can occur in negative feedback

A
  • If the level of something rises, control systems reduce it again - If the level of something falls, control systems raise it again
76
Q

Identify 3 things in the body controlled by negative feedback mechanisms

A
  • Water concentration - Body temperature - The glucose concentration in the blood
77
Q

What is the normal human body temperature

A

37 degrees

78
Q

Where is the thermoregulatory centre

A

In the hypothalamus, a part of the brain

79
Q

What is the thermoregulatory centre

A

The part of the brain that monitors and controls body temperature

80
Q

What 2 things in the body detects a change in body temperature

A
  • The thermoregulatory centre in the hypothalamus contains receptors which are sensitive to the temperature of the blood flowing through the brain - The skin contains temperature receptors which send electrical impulses down sensory neurones to the thermoregulatory centre
81
Q

What does the body do when body temperature becomes too high, and how does this help to decrease body temp

A
  • Sweat glands release sweat onto the surface of the skin; the sweat evaporates which removes heat energy from the body, thus cooling the body down - Blood vessels that supply the capillaries under the surface of the skin dilate (vasodilation), which allows more blood to flow through the capillaries and so more heat can transfer out of the blood through radiation, so the body temperature returns to its normal level - Hair erector muscle relaxes, lowering the hair so it lies flat on the skin and so less air is trapped for insulation
82
Q

What does the body do when body temperature becomes too low, and how does this help to increase the body temperature

A
  • Blood vessels that supply the capillaries under the surface of the skin constrict (vasoconstriction), and so less blood flows through the capillaries therefore less heat is lost from the body - We shiver, and so muscles contract, and to generate energy for this contraction the muscle cells increase their rate of respiration, which releases heat, and warms the body so body temperature returns to its normal level - Hair erector muscles contract and so hairs stand up to trap an insulating layer of air, which means it is harder to lose heat from the skin - No sweat is produced, so less heat is lost from the body
83
Q

What is vasodilation

A

When blood vessels dilate

84
Q

What is vasoconstriction

A

When blood vessels constrict

85
Q

What is the endocrine system

A

A system in the body composed of glands which secrete hormones into the bloodstream

86
Q

What are hormones

A

Chemical messengers produced in one area of the body that have an effect on the function of another area in the body

87
Q

What are endocrine glands

A

Areas where hormones are produced and released into the bloodstream

88
Q

Identify 3 differences between the nervous system and the endocrine system

A
  • In the nervous system, messages are carried around the body using electrical impulses which travel down neurones, whereas in the endocrine system, messages are carried around the body in the blood using hormones - In the nervous system, it usually takes fractions of a second for the message to take effect, whereas the endocrine system tends to produce a much slower effect - In the nervous system, the effects last for a shorter time whereas in the endocrine system, effects usually last a longer time
89
Q

How does the endocrine system work

A
  • The endocrine system consists of a number of glands - These glands secrete hormones directly into the bloodstream - The blood carries the hormones all around the body, and each hormone only acts on specific target organs, where it produces an effect
90
Q

Identify 6 key glands in the endocrine system

A
  • Pancreas - Ovaries - Testes - Thyroid gland - Adrenal gland - Pituitary gland
91
Q

What hormones does the pancreas secrete

A

insulin and glucagon

92
Q

What is the target organ of hormones secreted by the pancreas (insulin and glucagon)

A

The liver

93
Q

What is the role of hormones secreted by the pancreas

A
  • Insulin lowers blood sugar levels - Glucagon raises blood sugar levels - Together they control the concentration of glucose in the blood
94
Q

What hormones are secreted by the ovaries

A

Oestrogen and Progesterone

95
Q

What are the target organs of oestrogen

A

Ovaries, uterus, pituitary gland

96
Q

What is the target organ of progesterone

A

uterus

97
Q

What are the roles of the hormones secreted by the ovaries

A
  • Oestrogen controls puberty and the menstrual cycle in females - Progesterone maintains the lining of the womb
98
Q

Where is the thyroid located

A

The base of the neck

99
Q

What hormone is secreted by the thyroid

A

Thyroxine

100
Q

What is the target organ of thyroxine

A

no specific organs; most body cells

101
Q

What is the role of thyroxine

A
  • Controls the rate of metabolism, so it makes the body’s chemical reactions take place at a faster rate - Involved in growth and development
102
Q

What are thyroxine levels controlled by in the body

A

Negative feedback

103
Q

Describe how thyroxine levels are controlled by negative feedback

A
  • If the pituitary gland detects low levels of thyroxine, then it will release TSH (thyroid stimulating hormone) into the bloodstream, which will stimulate the thyroid to produce more thyroxine into the blood, which will bring the level of thyroxine back to normal. The increased level of thyroxine is then detected by the brain which then prevents the pituitary gland from producing TSH - If the level of thyroxine becomes too high, events are triggered to bring it back down
104
Q

Where are adrenal glands located

A

on top of the kidneys

105
Q

What hormone is released by the adrenal gland

A

Adrenaline

106
Q

When is adrenaline produced

A

In times of fear or stress

107
Q

What are the target organs of adrenaline

A

Vital organs such as the liver and the heart

108
Q

What is the role of adrenaline

A

It increases the heart rate, which means more oxygen and glucose, needed for aerobic respiration, are delivered in the blood to the brain and muscles, which prepares the body for action, and so prepares the body for fight or flight

109
Q

What hormone is secreted by the testes

A

testosterone

110
Q

What is the target organ of testosterone

A

male reproductive organs

111
Q

What is the role of testosterone

A

Controls male puberty

112
Q

Where are the pituitary glands located

A

In the brain

113
Q

What name is the pituitary gland often referred to as

A

A ‘master gland’

114
Q

What hormones are secreted by the pituitary glands

A

Multiple different hormones

115
Q

What is the role of hormones secreted by the pituitary gland

A

They act on other glands and they cause other hormones to be released, which can trigger a range of different effects in the body. The hormones released can help regulate growth, blood pressure, water balance, temperature, and sex organ functions

116
Q

Which organ monitors and controls blood glucose concentration

A

The pancreas

117
Q

Why do we need a controlled concentration of blood glucose

A

So that body cells have a constant supply of glucose which they can use for respiration, and if the concentration becomes too high then it can damage tissues

118
Q

What is type 1 diabetes

A

A disorder where the pancreas fails to produce sufficient insulin, or does not produce insulin at all, which means the person’s blood glucose level can rise to a level that makes them feel ill or can kill them

119
Q

How is type 1 diabetes treated

A

They monitor their blood glucose concentration and inject themselves with insulin if their blood glucose rises too much

120
Q

What 2 things does the amount of insulin injected by a diabetic depend on

A
  • Diet; those who eat more carbohydrates will need more insulin - How much exercise they do; more exercise means muscles absorb more glucose from the blood, and so they would need less insulin
121
Q

What is type 2 diabetes

A

When the body cells become resistant to insulin, and so they stop responding to insulin produced by the pancreas, therefore their cells will not take in glucose from the bloodstream, and so blood glucose levels can rise too high

122
Q

How is type 2 diabetes treated

A

With a diet containing a controlled level of carbohydrates, in order to prevent the blood glucose concentration from rising too high, and also exercising regularly

123
Q

What is the main risk factor for type 2 diabetes

A

Obesity

124
Q

Compare type 1 and type 2 diabetes

A
  • In both types, patients cannot regulate their blood glucose properly - Type 1 is generally diagnosed in childhood, whereas type 2 is often diagnosed in older people, mainly over 30, who have had unhealthy diets for a long time - Type 1 is caused when the pancreas stops producing insulin, or only produces small amounts, whereas in type 2, the body becomes resistant to insulin and so body cells stop responding to insulin - Type 1 is not associated with excess body weight, whereas type 2 is associated often with excess body weight - Type 1 is treated with insulin injections, whereas type 2 is generally treated without medication, and so they are advised to keep a carbohydrate-controlled diet, and to exercise regularly
125
Q

Describe what happens when the blood glucose concentration is too high

A
  1. When blood glucose concentration is too high, this is sensed by the pancreas 2. The pancreas produces the hormone insulin 3. Insulin travels in the bloodstream all around the body and it triggers body cells to take up glucose from the blood 3. Insulin also triggers liver and muscle cells to store excess glucose as a storage molecule called glycogen 4. Because glucose is now being taken out of the blood and stored, the concentration of glucose in the blood returns to its normal level; homeostasis has taken place
126
Q

Describe what happens if blood glucose concentration becomes too low

A
  1. If the blood glucose concentration is too low, this is detected by the pancreas 2. The pancreas releases the hormone glucagon into the bloodstream 3. Glucagon triggers liver cells to convert glycogen stores back to glucose; this glucose is released into the blood 4. This causes the blood glucose concentration to return to normal
127
Q

Describe how the blood glucose concentration is kept constant in a human without diabetes

A
  • Blood glucose concentration will rise slightly and fall slightly throughout the day - This is because the blood glucose concentration is controlled by a balance between insulin and glucagon - If the glucose concentration rises, then the pancreas releases insulin, causing the glucose concentration to fall - When the glucose concentration falls to a certain level, the pancreas releases glucagon and this causes the glucose concentration to rise again - Because insulin and glucagon have opposite effects on the blood glucose concentration, it forms a negative feedback cycle
128
Q

What is the difference between glucose, glycogen, and glucagon

A
  • Glucose is sugar - Glycogen is a storage molecule of glucose - Glucagon is a hormone which increases blood glucose levels
129
Q

Why is it important that the body keeps the level of water in the blood at a constant level

A
  • Because if the blood becomes too dilute, then water moves into cells by osmosis - If the blood becomes too concentrated, then water moves by osmosis out of cells - If body cells gain or lose too much water by osmosis then they do not work efficiently
130
Q

How does the body take in water

A
  • Food - Drink - Respiration
131
Q

How can the body lose water

A
  • We lose water via the lungs when we exhale - When we sweat, we lose water through the skin; sweat also contains ions, such as the sodium ion, and the waste product urea - Via the kidneys in urine
132
Q

Which methods of water loss can the body control, and not control; explain why

A
  • We cannot control the water we lose via the lungs when we exhale - We cannot control how much water, ions, or urea is lost by sweating, because sweating is part of the body’s temperature control system - The body can control how much water is lost in urine, so if the blood is too dilute the kidneys remove the excess water, and they produce a greater volume of urine
133
Q

What 3 things are removed in urine

A
  • Excess water from the body - Urea - Excess ions
134
Q

What is osmoregulation

A

Controlling the amount of dissolved substances in the blood and tissue fluid

135
Q

What excretory organs are involved in osmoregulation

A
  • Kidneys - Lungs - Skin
136
Q

Describe how the kidneys maintain the concentration of substances in the blood

A
  • Blood enters the kidney through an artery, and this blood contains the waste product urea - The kidney removes this urea as well as excess ions and excess water - These leave the kidney as urine and this is stored in the bladder - Blood now leaves the kidney through a vein, and now contains no urea
137
Q

Explain how the kidneys adjust the level of molecules in the blood

A
  • The blood passes through the capillaries, where small molecules are filtered out of the blood; these include urea, ions, and water, as well as the sugar glucose - These pass into a tube - Now, all of the glucose, some of the ions, and some of the water is reabsorbed back into the blood; this is called selective reabsorption - Urea, excess ions, and excess water are released as urine - Therefore, after the blood has passed through the kidneys, the concentration of glucose does not change; this is because the kidneys filter glucose out of the blood but then reabsorb it all back into the blood - The concentration of ions in the blood after passing through the kidneys decreases, as the kidneys filter ions out of the blood but then reabsorb a certain amount of ions back into the blood, depending on the needs of the body - The concentration of urea in the blood after passing through the kidneys falls to virtually zero because the kidneys filter out all of the urea and do not reabsorb it - The kidneys carry out homeostasis
138
Q

What is selective reabsorption

A

When the kidneys reabsorb certain useful molecules from the blood

139
Q

Describe the process of deamination

A
  • When we digest protein, amino acids pass into the blood; excess protein and amino acids cannot be stored in the body as it is poisonous - We often eat more protein than the body needs, so the liver breaks down the excess amino acids and produces the chemical ammonia
140
Q

How does the body deal with excess amino acids

A
  • Ammonia, produced by the liver from excess amino acids, is a very toxic chemical so the liver immediately converts it to urea - The urea can be safely excreted by the kidneys
141
Q

What does ADH stand for

A

Anti-diuretic hormone

142
Q

Which gland releases ADH

A

The pituitary gland

143
Q

By what process is the concentration of water in blood controlled by

A

Negative feedback

144
Q

Describe what happens when the concentration of water in the blood becomes too low

A
  • If the blood becomes too concentrated, this means the level of water in the blood falls, then this means the concentration of blood starts to increase - This is detected by special cells in the hypothalamus - These cells cause the pituitary gland to release more of the hormone ADH into the bloodstream - ADH travels in the blood to the kidneys, and causes the kidney tubules to become more permeable to water - This means more water can now pass out of the kidney tubules, therefore more water is reabsorbed from the tubules back into the blood - This makes the urine more concentrated, and less of it is produced, and the blood becomes more dilute, therefore the amount of water in the blood rises back to its normal level - As the level of water in the blood returns to normal, the pituitary gland stops releasing ADH
145
Q

Describe what happens when the concentration of water in the blood is too high

A
  • When there is a high concentration of water in the blood, the blood becomes more dilute, and so the concentration of blood starts to decrease - This is detected by special cells in the hypothalamus - These cells cause the pituitary gland to release less ADH, therefore less ADH travels in the blood to the kidney - This means the kidney tubules become less permeable to water, therefore less water is reabsorbed back into the blood - This produces more urine, and the urine becomes more dilute, allowing the blood to become more concentrated, therefore the concentration of water in the blood returns to normal
146
Q

Identify 2 ways of treating kidney failure

A
  • Kidney dialysis - Kidney transplant
147
Q

Describe how kidney dialysis works

A
  • When a patient has kidney failure, their blood will contain a higher concentration of water, ions, and urea than it should - In kidney dialysis, the patient’s blood passes over a partially permeable membrane, which allows urea, ions, and water through, but will not allow larger molecules such as proteins to pass through - Blood cells are also too large to pass through the membrane - On the other side of the membrane there is dialysis fluid; this contains the normal concentrations of water and ions, but does not contain any urea. This creates a concentration gradient for urea, so the urea diffuses from the blood into the dialysis fluid; the dialysis fluid is constantly refreshed, ensuring that there is always a large concentration gradient for urea - The dialysis fluid also contains the normal concentrations of water and ions, which means that some of the water and some of the ions will diffuse from the blood and into the dialysis fluid, as there is a lower concentration of water and ions in the dialysis fluid than in the blood, which creates a concentration gradient. Because of this, the concentrations of water and ions in the blood will return to normal - This therefore does the job of the kidney for the patient
148
Q

What are the disadvantages of using kidney dialysis

A
  • It is inconvenient; patients have to visit a hospital several times a week - Patients have to eat a controlled diet so they do not produce too much urea - Needs to be used for the rest of your life unless a transplant is found
149
Q

What is a kidney transplant

A

When a diseased kidney is replaced with a healthy kidney from a donor

150
Q

What are the disadvantages of using a kidney transplant

A
  • The donated kidney may be rejected by the patient’s immune system - It is not widely available; as there may be a shortage of donors, or not a donor with your blood type - Life long immunosuppressants
151
Q

Compare the use of dialysis to the use of a kidney transplant

A
  • In dialysis, there is no shortage of dialysis machines, whereas there is a shortage of kidney donors - Dialysis requires frequent treatment and a controlled diet, whereas a kidney transplant allows a patient to lead a normal life - Kidney dialysis is expensive in the long term, whereas a transplant is only expensive initially - Kidney transplant patients have to take anti-rejection drugs for the rest of their life, whereas dialysis patients do not

GCSE AQA TRIPLE SCIENCE - Biology (9 decks)

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