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OCR GATEWAY GCSE BIOLOGY > B3 Organism level systems > Flashcards

B3 Organism level systems Flashcards

1
Q

What is the nervous system?

A

-The nervous system uses electrical impulses to cause fast, but short-lived responses.
-These responses enable organisms to react to their surroundings and coordinate their behaviour.

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2
Q

What is the Central Nervous system?

A

-Consists of the brain and the spinal cord.
-Coordinates how and where the electrical impulses are transmitted next to allow us to understand our surroundings and respond in order to survive.

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3
Q

What is the peripheral nervous system?

A

Consists of neurones that carry information to or from the CNS.

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4
Q

Why is the nervous system required?

A

To move, control and communicate internal processes and to carry out higher order functions like thinking and memory.

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5
Q

What are neurones?

A

Highly specialised nerve cells that are required to transmit fast but short-lived electrical impulses around the nervous system.

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6
Q

What are sensory neurones?

A

They send electrical impulses from the receptor (sense organs) to the CNS.

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7
Q

What are relay neurones?

A

They send electrical impulses from the sensory neurone to the motor neurone within the CNS.

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8
Q

What are motor neurones?

A

They send electrical impulses from the CNS to the effector (muscles/glands).

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9
Q

What are sensory receptors?

A

They detect a stimulus and stimulate electrical impulses in response.

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10
Q

What are sense organs?

A

Contain groups of receptors that respond to specific stimuli.

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11
Q

What is a stimulus?

A

A change in environment.

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12
Q

What are reflexes?

A

-Involuntary responses that occur without conscious thought to protect the body from harm.
-They are very fast (0.2s) and the same every time.

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13
Q

What are voluntary responses?

A

When you consciously decide to do something.

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14
Q

What is a reflex arc?

A

The pathway taken by an impulse as a subconscious response to a dangerous stimuli during the reflex action.

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15
Q

Why do we need a reflex arc?

A

Sometimes an extremely quick response is needed and the body doesn’t have time to go to the conscious part of your brain.

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16
Q

Direction of Reflex arc:

A

Stimulus -> receptor -> sensory neurone -> spinal cord -> relay neurone -> motor neurone -> effector -> response.

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17
Q

Describe process of the reflex arc: (5 steps)

A
  1. Sensory receptors detect a stimulus.
  2. Electrical impulses are sent along a sensory neurone.
  3. In the spinal cord of the CNS: the electrical impulses are sent along to the sensory neurone.
  4. The relay neurone sends the electrical impulses along the motor neurone.
  5. The motor neurone sends the electrical impulses to an effector which produces a response.
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18
Q

What is a synapse?

A

A gap between 2 neurones and as electrical impulses cannot travel through the synapse, neurotransmitters diffuse across this gap.

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19
Q

Why do we need a synapse?

A

Allows a neurone to pass electrical impulses to the next neurone as neurones aren’t directly connected to each other.

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20
Q

What are neurotransmitters?

A

-Chemical messengers released when the electrical impulse reaches the dendrites at the end of the axon.
-This stimulates the 2nd neurone to transmit an electrical impulse along its axon so that the electrical impulse has been carried from one neurone to the next.

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21
Q

How do we use light to see?

A

The eye contains 2 types of receptor cells: rods and cones.

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22
Q

What are rods?

A

They respond to different light intensities.

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23
Q

What are cones?

A

They respond to different wavelengths of light (red, green and blue).

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24
Q

How does the eye make an image?

A
  1. The stimulus, light, is detected by the receptor.
  2. The stimulus is converted by the cells into an electrical impulse.
  3. This then passes into the optic nerve and is carried to the brain.
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25
Q

What is the function of the cornea?

A

Transparent outer part of the eye which refracts light to reach the retina and light passes through here before passing through the pupil.

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26
Q

What is the function of the pupil?

A

Small hole at the centre of the iris where light enters the eye.

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27
Q

What is the function of the lens?

A

Transparent, bioconvex disc that attaches to ciliary muscles by suspensory ligaments and focuses light onto the retina.

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28
Q

What is the function of the retina?

A

-Receives images and sends them as electric signals through the optic nerve to the brain.
-Also contains both types of light receptors.

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29
Q

What is the function of the optic nerve?

A

A nerve that leaves the eye and leads to the brain which carries the impulses from the retina to the brain to create an image.

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30
Q

What is the function of the ciliary muscles?

A

They hold the lens in place, controlling its shape by contracting to focus on a near object and relaxing to focus on a far object.

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31
Q

What is the function of the suspensory ligaments?

A

Hold the lens in place, controlling its shape by slackening to focus on a near object and tightening to focus on a far object.

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32
Q

What is the function of the fovia?

A

A region of retina with highest cone density where the eye sees very good detail.

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33
Q

What is the function of the iris?

A

Controls the size of the pupil and therefore the amount of light falling on the retina.

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34
Q

How do muscles work?

A

-Can contract (muscle fibres shorten).
-Can relax (muscle fibres lengthen).

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35
Q

How does the pupil work?

A

-Can constrict (close up and become smaller).
-Can dilate (open up and become bigger).

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36
Q

What if there’s too much light on the eye?

A

This damages the light sensitive cells of the retina.

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37
Q

What if there’s too little light on the eye?

A

There’s not enough stimulus to the cells for the eye to make an image.

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38
Q

What is the pupil reflex?

A

This reflex action is controlled by the iris muscles and changes the pupil size in response to bright or dim light, therefore controlling the amount of light entering the eye.

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39
Q

How do the iris muscles work?

A

-There are 2 types, radial and circular muscles, which have antagonistic effects.
-Contraction of radial muscles causes pupil to dilate.
-Contraction of circular muscles causes pupil to constrict.

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40
Q

What is refraction?

A

The bending of light rays.

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41
Q

How does the eye focus light?

A
  1. Light enters the eye where it’s refracted by the cornea and the lens.
  2. The light rays have to be refracted precisely so that they are focused on the fovia of the retina.
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42
Q

Why does the lens change shape?

A

Light needs to be refracted more to focus on a near object and light needs to be refracted less to focus on a far object.

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43
Q

Accommodation to focus on a near object:

A
  1. The cilliary muscles contract.
  2. The suspensory ligaments slacken.
  3. The lens is thicker and more convex.
  4. This means light is refracted more.
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44
Q

Accommodation to focus on a far object:

A
  1. The cilliary muscles relax.
  2. The suspensory ligaments tighten.
  3. The lens becomes thinner and less convex.
  4. This means light is refracted less.
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45
Q

What is short sightedness?

A

The uncorrected image forms in front of the retina so the eyes cannot focus on distant objects but can focus on nearby objects.

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46
Q

What causes short sightedness?

A

-The ciliary muscles can’t make the lens thin enough to focus.
-The eyeball is too long.
-The lens is too powerful.

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47
Q

How do you correct short sightedness?

A

The concave (negative) lens in the glasses / contact lenses diverges (bends the light rays out) before they enter the eye.

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48
Q

What is long sightedness?

A

Uncorrected image forms behind retina so the eyes cannot focus on nearby objects but can focus on distant objects.

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49
Q

What causes long sightedness?

A

-The eye lens cannot thicken enough to form the image on the retina.
-The eyeball is too short.
-The lens is too weak.

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50
Q

How do you correct long sightedness?

A

The convex (positive) lens in the glasses / contact lenses converges (bends the light rays in) before they enter the eye.

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51
Q

What is focal length?

A

The distance a lens requires to bring an image to focus.

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52
Q

What is the formula for lens power?

A

Lens power (D) = 1 / focal length (m)

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53
Q

What is the formula for total power?

A

Ptotal = P1 + P2

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54
Q

What happens if your nervous system gets damaged?

A

This prevents impulses from being passed effectively through the nervous system.

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55
Q

What does damage to the PNS affect?

A

The sensory and motor neurones.

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56
Q

What can nervous system damage can result from?

A

-Injury
-Disease
-Genetic condition
-Ingesting a toxic substance

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57
Q

What are the effects of damage to the PNS?

A

-Inability to detect pain
-Numbness
-Loss of coordination

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58
Q

What are the effects of damage to the CNS?

A

-Loss of control of body systems
-Partial / complete paralysis
-Memory loss / processing difficulties

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59
Q

Can damage to the PNS be reversed?

A

-The PNS has limited ability to regenerate.
-Minor nerve damage often self-heals and symptoms gradually decrease.
-More severe nerve damage can be treated through surgery.

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60
Q

Can damage to the CNS be reversed?

A

-The CNS cannot regenerate.
-Any damage is permanent unless it can be corrected through surgery.

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61
Q

Why is it difficult to repair the CNS?

A

-The spinal cord consists of 31 pairs of nerves where each pair contains many nerve fibres.
-Extremely difficult to identify and repair damage to an individual nerve fibre without damaging others as the spinal cord is 1.5cm in diameter.

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62
Q

Why is brain damage difficult to diagnose?

A

-High risks of brain damage during research due to its delicacy.
-Limited understanding of the brain due to its complex structure.
-Unethical issues if the patient is unable to consent.
-Accidental damage could lead to permanent speech / motor issues or changes in personality.

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63
Q

How can we diagnose brain damage?

A

-MRI / CT scans to build up an image of the damage sight.
-Study people with brain damage to see how they’ve been impacted mentally and physically.
-Deep brain stimulation: inserting electrodes to stimulate brain function.

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64
Q

What are the treatments available for some brain conditions?

A

-Radiotherapy and chemotherapy to treat a brain tumour.
-Surgery to remove damaged brain tissues.

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65
Q

What is the function of the corpus callosum?

A

Connects the cerebral hemispheres to allow left and right sides of the brain to communicate.

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66
Q

What is the function of the pituitary gland?

A

Stores and releases important hormones.

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67
Q

What is the function of the medulla?

A

A part of the brainstem involved with automatic (unconscious) activities:
-Heart rate
-Breathing rate
-Blood pressure
-Vomiting

68
Q

What is the function of the hypothalamus?

A

Regulates body temperature and water balance in homeostasis.

69
Q

What is the function of the cerebrum?

A

Largest part of the brain which contains of 2 cerebral cortex and is also involved with conscious activities:
-Behaviour
-Learning
-Conscious thought
-Memory

70
Q

What are the functions of the 2 cerebral cortex (folded hemispheres)?

A

-Right hemisphere controls all the actions in the left side of the body.
-Left hemisphere controls all the actions in the right side of the body.

71
Q

What is the function of the cerebellum?

A

The 2nd largest part of brain which contributes to:
-Coordination
-Precision (learned and fine movements)
-Posture
-Balance

72
Q

What are the effects of cerebral damage?

A

Human disorders in:
-Movement
-Balance
-Posture
-Motor learning

73
Q

What is the endocrine system?

A

-Contains a series of glands that secrete hormones into the bloodstream to travel around the body.
-This allows different parts of the body to communicate with each other.

74
Q

What are hormones?

A

Small chemical messengers transported throughout the body in the plasma by the blood.

75
Q

How do hormones work?

A
  1. They cause a response in target cells by diffusing out of the blood and binding to their specific receptors.
  2. Once bound to specific receptors, the hormones stimulate the target cells to produce a response.
76
Q

What are target cells?

A

-Cells with the specific receptor for a hormone that produces an effect when the hormone binds.
-Found on the membranes / cytoplasm of cells in the target organs.

77
Q

What are features of the endocrine system?

A

-Relies on hormones secreted by the glands and transported by the blood.
-Slow as process ends when hormone breaks down.
-Long term effects.
-Hormones are sent all around the body and are more general.

78
Q

What are features of the nervous system?

A

-Relies on electrical impulses transferred along neurones.
-Very fast.
-Short term effects.
-Nerve impulses are sent to specific areas and are more precise.

79
Q

What is the master gland?

A

The pituitary gland which secretes hormones and tells other glands to secrete hormones.

80
Q

What is thyroxine?

A

-Regulates the metabolic rate.
-TSH is released by the pituitary gland.
-Metabolic rate increases when TSH stimulates the thyroid gland to release more thyroxine.
-This allows cells to transfer additional energy.

81
Q

What is metabolic rate?

A

How much energy is available to cells.

82
Q

What is negative feedback?

A

-A small change in one direction is detected by the sensory receptors.
-The efforts work to reverse the change and restore the conditions to base levels.

83
Q

What is adrenaline?

A

-Prepares the body for intensive action.
-Triggers the fight of flight response.
-Adrenal glands stop producing adrenaline when stress is removed as signals stop so affected body systems will return to previous state.

84
Q

What happens when adrenaline is released?

A

-Increases breathing rate (increases rate of ATP production).
-Hairs stand erect.
-Increases heart rate.
-Dilates pupils.
-Increases blood glucose levels.

85
Q

What is the development of follicle stage in the menstrual cycle? And what is it stimulated by?

A

-Days 0-14.
-Stimulated by FSH.
-Stage 1: Menstruation (days 0-5). Period of bleeding as the uterus lining breaks down.
-Stage 2: (days 5-14). Building up of the uterus lining, thickens with blood vessels and glands due to oestrogen hormone.

86
Q

What happens in day 14 of the menstrual cycle? And what is it stimulated by?

A

-Oestrogen levels peak and cause the pituitary gland to release LH which stimulates ovulation.
-Ovulation: the nature follicle bursts and releases the egg from the ovaries, into the oviduct.

87
Q

What is the development of corpus luteum stage in the menstrual cycle?

A

-Days 14-28.
-Follicle cells remain on the ovary surface and form corpus luteum which releases progesterone.
-Progesterone maintains the uterus lining for pregnancy or stops at day 28 and the menstrual cycle repeats. Depends on whether there is a fertilised egg.

88
Q

What happens if there is no fertilised egg after day 28 of the menstrual cycle?

A

The egg dies and the menstrual cycle repeats.

89
Q

What happens if there is a fertilised egg after day 28 of the menstrual cycle?

A
  1. Before implanting, the egg fell divided by mitosis and forms an embryo.
  2. The embryo implants into the uterus lining.
  3. The menstrual cycle stops and the uterus lining is maintained.
90
Q

What is an embryo?

A

A ball of cells.

91
Q

What is menopause.

A

When woman stop having their menstrual cycle and usually occurs at ages 45-55.

92
Q

What is FSH?

A

-Follicle Stimulating Hormone.
-Released from the pituitary gland at the start of the cycle.
-Stimulates follicle development from days 0-14 of menstrual cycle.
-Stimulates production of oestrogen.

93
Q

What is oestrogen?

A

-Produced in the first half of the cycle and released by the follicle cells surrounding the egg.
-Causes the uterus lining to repair and thicken.
-Inhibits the production of FSH.
-Increases through first 14 days and peaks to stimulate the release of LH.

94
Q

What is LH?

A

-Luteinising hormone.
-Released by pituitary gland at day 14 as a short, sharp peak.
-Causes ovulation (the release of an egg).

95
Q

What is progesterone?

A

-Released by corpus luteum (yellow body) in the second half of the cycle.
-Maintains the uterus lining and stays high during pregnancy for the embryo to implant itself.
-High from days 14-27 and decreases one day before menstruation unless the person is pregnant.
-Inhibits production of LH and FSH.

96
Q

What are hormonal methods of contraception?

A

-They release either oestrogen, progesterone or both.
-Oestrogen: inhibits the the production of FSH so no egg will be developed / released.
-Progesterone: stimulates the production of thick mucus to the cervix to prevent sperm from reaching the egg.

97
Q

What is the cervix?

A

The entrance to the uterus.

98
Q

How does the combined oral contraceptive pill work?

A

-Contains both oestrogen and progesterone.
-99% effective.
-Can have detrimental side effects.

99
Q

How does the progesterone only pill work?

A

-99% effective.
-Less side effects than combined oral contraceptive pill.

100
Q

How does the contraceptive patch on arm work?

A

-Releases progesterone and oestrogen slowly.
-Lasts one week.

101
Q

How does the contraceptive injection work?

A

-Releases progesterone slowly.
-Lasts 2-3 months.

102
Q

How does the contraceptive implant under skin work?

A

-Slowly releases progesterone.
-Lasts 3 years.

103
Q

How does an IUD work?

A

-Only plastic IUD involves hormones.
-Releases progesterone.
-Lasts more than 3 years.

104
Q

What are examples of hormonal methods of contraception?

A

-Combined oral contraceptive pill.
-Progesterone only pill.
-Contraceptive patch on arm.
-Contraceptive injection.
-Contraceptive implant under skin.
-Plastic IUD.

105
Q

What are non-hormonal methods of contraception?

A

They physically prevent the sperm meeting the egg and don’t involve hormones.

106
Q

How does a condom work?

A

-Goes over penis / vagina (depends whether it’s a male or female condom).
-Traps sperm.
-Protects against STDs.
-One time use.
-Cheap.
-Readily available.
-Easy to use.
-Breakable.

107
Q

How does a diagram work?

A

-Fits over cervix and blocks sperm from entering the uterus.
-Unreliable so has to be used with a spermicide.

108
Q

What is a spermicide?

A

Kills sperm.

109
Q

How does sterilisation work?

A

-Permanent form of contraception.
-Hysterectomy: female sterilisation. The oviducts are cut / tied.
-Vasectomy: male sterilisation. The tubes that link to the urethra are cut / tied.

110
Q

How do natural methods of contraception work?

A

-Sex at certain times.
-Stop sex before ejaculation.
-These two methods are unreliable and not recommended.
-Or you can abstain from sex.

111
Q

What are FSH injections?

A

-Used when infertility is due to lack of FSH so ovulation doesn’t occur.
-Injected (instead of pill) as higher levels will be targeted in the correct places.
-Can lead to multiple births.

112
Q

How do FSH injections work?

A

They stimulate follicle development as this correlates to egg development, maturation and oestrogen production.

113
Q

What is IVF?

A

-In Vitro Fertilisation.
-Used when oviducts are damaged so fertilisation can’t occur.

114
Q

What is the process of IVF?

A
  1. Female treated with FSH pill (stimulates egg development) and then LH.
  2. Eggs are collected from the woman’s ovaries and fertiliser by father’s sperm in a laboratory.
  3. Eggs placed into incubator to grow into embryos.
  4. 1 or more embryos inserted into mother’s uterus where they grow into foetuses.
115
Q

What happens if the man has a low sperm count during IVF?

A

-An ICSI (Intra Cytoplasmic Sperm Injection) can be done.
-The sperm is injected into an egg cell with a really small needle.

116
Q

Why are embryos placed into an incubator during the process of IVF?

A

To provide an optimum temperature for enzymes and therefore cell growth.

117
Q

What are pros of IVF?

A

Allows infertile couples to have babies.

118
Q

What are cons of IVF?

A

-Designer babies.
-Extra leftover embryos are destroyed.
-Expensive.
-Side effects: abdominal pain + vomiting.
-Can result in multiple births and associated risks.

119
Q

What is a tropism / tropic response?

A

-Plants detect stimuli in the environment and respond by growth in a specific direction (to / away from stimuli).
-Positive tropism: to stimuli.
-Negative tropism: away from stimuli.

120
Q

What is a phototropism?

A

A response to light.

121
Q

What is a gravitropism?

A

Response to gravity.

122
Q

What happens during a positive phototropism?

A
  1. The plant is exposed to light on one side.
  2. Auxins move and accumulate in the shaded side of the shoot.
  3. Auxins stimulate faster cell elongation here.
  4. This causes the shoot to bend towards the light.
  5. The plant recurves more light, allowing photosynthesis to occur at a faster rate.
123
Q

What happens during a negative gravitropism?

A
  1. Auxins move and accumulate in the lower side of the shoot due to gravity.
  2. This stimulates cell elongation as there are more auxins here.
  3. This makes the shoot bend and grow away from the ground.
  4. This is beneficial as light levels are likely to be higher and further from ground.
124
Q

What happens during a positive gravitropism?

A
  1. In plant roots, auxins inhibit growth. They move and accumulate on lower side.
  2. Cell elongation happens more on the side with less auxins so it stimulates cells to grow on the upper side. This makes the root bend and grow downwards.
  3. This is beneficial as there are more likely to be increased levels of water and mineral ions lower down, and it provides stability for the plant.
125
Q

What are uses of auxins?

A

-Rooting powders to produce roots for cut plants and stimulate growth.
-Selective herbicides to overstimulate the plant so that it grows too quickly and dies.

126
Q

What are uses of giberellins?

A

-Alter dormancy by inducing germination so all plants continue to grow despite the time of year which results in multiple crops per year.
-Inducing flowering which results in more and bigger flowers (these usually require certain conditions).
-Used in parthenocarpic fruit development as seedless fruit tend to grow small and slowly however they instead grow faster and larger.

127
Q

How is the plant hormone ethene used?

A

Stimulates the ripening of fruit by stimulating the enzyme.

128
Q

How does ethene work?

A
  1. Fruits are picked unripe (still hard) so they don’t get damaged during transport and storage.
  2. When needed, ethene is used to ripen fruit so that it’s soft for consumers.
129
Q

What is tissue culture?

A

Technique used to grow whole new plants from small sections of a parent plant.

130
Q

What is homeostasis?

A

-The maintenance of a stable internal environment despite fluctuations in internal and external body conditions.
-Allows metabolic reactions to occur at appropriate times.

131
Q

What are the 3 conditions that need to be controlled in the body?

A

-Temperature.
-Water potential.
-Blood glucose.

132
Q

How is temperate controlled in the body?

A

-Monitored by some or the receptors in the hypothalamus contained in the thermoregulatory centre.
-Cools the body down / keeps the body warm.
-A constant body temperature of 37 degrees celsius must be maintained so that enzymes don’t denature.

133
Q

How is water potential controlled in the body?

A

The kidneys maintain the water balance of the body.

134
Q

How is blood glucose controlled in the body?

A

Pancreas secretes insulin to regulate blood glucose levels.

135
Q

What is thermoregulatory centre?

A

-Contained in the hypothalamus of the brain.
-Has receptors that monitor the temperature of the blood flowing through it.
-Also received information from temperature receptors in the skin.

136
Q

What does the thermoregulatory centre do if a change in external temperature is detected?

A

-Impulses are sent to the effectors to restore body temperature to normal.
-If the body is too hot / too cold, this can lead to hyperthermia.

137
Q

How does the human body cool down?

A

-Sweating: sweat glands in skin produce more sweat which evaporated from the skin’s surface, cooling the body.
-Vasodilation: arterioles supplying blood to the capillaries in the surface of the skin dilate, increasing blood supply in the skin so that more heat is lost by radiating.
-Hair erection: hair erector muscles relax, allowing the hair to lie flat so less still air is trapped and therefore less insulation.

138
Q

How does the human body become warmer?

A

-Shivering: muscles contract which requires energy so there’s more respiration and this releases more heat which helps to raise blood temperature.
-Vasoconstriction: arterioles constrict to reduce blood flow to the capillaries in the skin’s surface which reduces the heat loss by radiation to protect vital organs.
-Hair erection: Erector muscles contract, raising hairs and trapping a layer of insulating air.

139
Q

How does the human body regulate blood glucose levels?

A
  1. Change detected by receptors in pancreas.
  2. Insulin (too high levels) / glucagon (too low levels) secreted by pancreas.
  3. Insulin: higher cellular uptake of glucose from blood in liver and muscles to use in respiration and liver and muscle cells convert excess glucose into glycogen.

Glucagon: liver and muscle cells break down glycogen into glucose.

140
Q

What is glycogen?

A

Strong carbohydrate made of a long chain of glucose molecules.

141
Q

What is the purpose of urine samples?

A

-Assist in the diagnosis,monitoring + treatment of lots of diseases.
-Blood in urine: kidney disease.
-Protein in urine: kidney disease and signs of damage from long-lasting diabetes.
-Sugar in urine: indicates diabetes.

142
Q

What is type 1 diabetes?

A

-Inherited and auto-immune disease.
-Usually from a young age and lifelong.
-Can’t secrete any / enough insulin so glucose isn’t absorbed into blood.

143
Q

How is type 1 diabetes treated?

A

-Insulin injections before meals.
-High blood pressure: insulin and low blood pressure: eat.
-Monitor diet and exercise regularly.

144
Q

What is type 2 diabetes?

A

-Originates from old age and obesity.
-Can be treated.
-Secrete insulin but resistant to effects of it (don’t respond).

145
Q

How can type 2 diabetes be treated?

A

-Drugs to make insulin more effective.
-Monitor diet (reduce carbs and sugar).
-Lose weight and exercise regularly.

146
Q

What is the gross structure of the kidney?

A

-Contains a correct and a medulla.
-Renal arteries: transport blood to kidney.
-Renal veins: transport blood away from the kidney.
-Made of over a million tubules called nephrons / renal tubules.
-An excretory pair of organs: the ureter carries fluid away from the kidneys to the bladder.

147
Q

What is the structure of a renal tubule / nephron?

A

Contains:
-Glomerulus: small knot of capillaries.
-Bowman’s capsule.
-PCT.
-DCT.
-Loop of henle.
-Collecting duct.

148
Q

What is deamination?

A

-Body converts amino acids into lipids / carbohydrates as they are in excess.
-They can be stored as an energy source for later.

149
Q

What happens after deamination?

A
  1. The process produces ammonia which is highly toxic.
  2. Ammonia is converted to the waste product urea to be safe.
  3. Urea has to be excreted by the kidneys through urine.
150
Q

What is the order of events inside the kidney?

A
  1. Ultrafiltration (from glomerulus until bowman’s capsule).
  2. Selective reabsorption (all throughout and starts from PCT).
  3. Ion balance (occurs in DCT).
  4. Osmoregulation (in loop of henle and collecting duct).
151
Q

What happens in ultrafiltration?

A

-Blood enters the glomerulus under high pressure.
-Small molecules (water, glucose, amino acids and urea) are forced out of the glomerulus, through the pores in the endothelium, into bowman’s capsule.

152
Q

What happens in selective reabsorption?

A

The following are re absorbed into blood:
-All amino acids and glucose.
-Some water.
-Some ions (depends on how many in body already).
-No urea.

153
Q

What happens in ion balance?

A

-Ions are reabsorbed into blood depending on the body’s requirements.
-Lots of sweat: want to lose less ions.
-Lots of salt: want to lose more ions.

154
Q

What happens in osmoregulation?

A

-Loop of henle creates a lower water potential in the medulla so water can be reabsorbed into the collecting duct by osmosis down a water potential gradient.
-More water is absorbed in the collecting duct: smaller and more concentrated volume of urine.
-Less water is absorbed in the collecting duct: larger and more dilute volume of urine.

155
Q

How is water potential regulated using ADH in the kidneys?

A
  1. Change is detected by receptors in hypothalamus.
  2. Less / more ADH secreted by pituitary gland if high / low water potential in blood.
  3. This is transported to target tissues (collecting ducts in kidney).
  4. Collecting ducts are less / more permeable to water.
  5. Less / more water is reabsorbed from the tubules into the blood.
  6. Lower / higher water potential in blood and more / less water excreted as urine.
156
Q

What happens if an animal cell is in a solution of lower water potential?

A

The cell will shrink (crenate).

157
Q

What happens if an animal cell is in a solution of higher water potential?

A

Water will move into the cell and it will burst (lyse).

158
Q

What happens if an animal cell is in a solution of equal water potential?

A

No net movement of water will happen.

159
Q

What is dehydration?

A

-Result of decrease in water potential in blood.
-Body loses more fluid than consumed.
-Can cause severe kidney damage.

160
Q

What are symptoms of dehydration?

A

-Small volume of dark coloured, strong smelling urine.
-Thirst.
-Light-headed.
-Tired.
-Dry mouth.

161
Q

What is over-hydration?

A

-Result of increase in water potential in blood and lower blood sodium.
-Can be athletes who drink too much and reduce blood sodium by sweating.
-Can cause brain to swell: possibly leading to confusion, seizures and coma.

162
Q

What are symptoms of over hydration?

A

-Nausea.
-Vomiting.
-Headache.

163
Q

What is the thirst response?

A

The hypothalamus has a thirst centre with receptors monitoring blood ions and when required, sends out a strong message of thirst.

164
Q

What are examples of changes the thirst response detects?

A

-Extra sweating -> low blood ions -> more water required.
-Salty snacks -> high blood sodium ions -> less water required.
-Exercise -> sweat more and respire more -> loss water and ions and glucose.

165
Q

Why do sports drinks have high sodium and low sugar?

A

-High sodium: replenishes water lost in sweat so less water is required.
-Low sugar: decreases urination as less water transfer.

OCR GATEWAY GCSE BIOLOGY (6 decks)

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