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Homeostasis Flashcards

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1
Q

What is Homeostasis

A

Homeostasis is the regulation of the internal conditions of a cell or organism to maintain optimum conditions for function in response to internal and external changes

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2
Q

What does homeostasis include control of in the human body

A

Blood glucose concentration
Body temperature
Water levels

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3
Q

What are the features of an automatic control system

A

Receptor cells detect a stimulus in the environment
Coordination centres such as the brain receive and process information from receptors
Effectors, muscles or glands, bring about responses which restore optimum levels

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4
Q

Describe how the reflex arc works when touching a hot object

A

The stimulus which is the heat is detected by the receptor which is the skin
Electrical impulses now pass from the receptor along a sensory neurons to the central nervous system
At the end of a sensory neurons a chemical is released at the synapse
This chemical diffuses across to a relay neurons in the cns
This triggers an electrical impulse
The electrical impulse passes across the relay neurone to another synapse where a chemical is released
This chemical triggers an electrical impulse in a motor neurone
The electrical impulse now passes down the motor neurone to an effector which is the muscle
The muscle now contracts and pulls the hand away from the heat

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5
Q

Explain how reflexes protect us from danger

A

In reflexes there is no decision making by the conscious part of the brain this makes reflexes automatic and rapid

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6
Q

What is the function of the cerebral cortex

A

This is the outer part of the brain
It’s functions include language, memory, and consciousness

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7
Q

What is the function of the cerebellum

A

This controls our balance and coordinates our movements

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8
Q

What is the function of the medulla

A

The medulla controls our heart rate and breathing rate

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9
Q

Explain difficulties of investigating brain function and treating brain damage and diseases

A

The brain is protected by the skull making it difficult to access
The structures of the brain are extremely complex so it’s difficult to work out which parts of the brain carry out specific functions
The brain is extremely delicate and easy to damage

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10
Q

Explain how scientists use patients with brain damage to investigate the brain

A

Many scientists look at patients with 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

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11
Q

Explain how scientists stimulate the brain in order to investigate it

A

Electrically stimulating different parts of the brain can be done to see the effects on a persons behavior
That allows us to narrow down specific regions to their functions

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12
Q

Explain how MRI scans are used to investigate the brain

A

We can use MRI scanning to look at which parts of the brain are most active during different activities

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13
Q

What are the ways scientists use to investigate the brain

A

Patients with Brain damage
Electrical Stimulation
MRI scans

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14
Q

What is the eye

A

A sense organ that contains receptors sensitive to light intensity and color

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15
Q

Explain how the eye detects light

A

Light rays pass through the transparent front of the eye, this is called the cornea
The light rays then pass through the pupil in the center of the iris
The light rays now pass through the lens which focuses the light rays onto the back of the eye
The light rays are now focused on the retina, this contains receptor cells for light
The receptor cells in the retina now send electrical impulses down the optic nerve to the brain

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16
Q

What is the function of the cornea

A

The transparent front of the eye
This starts the focusing of the light rays

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17
Q

What is the function of the lens

A

To focus the light rays onto the back of the eye
The lens can change its shape allowing us to focus on distant or near objects, this is called accommodation

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18
Q

What is the function of the retina

A

Contains receptor cells for light
These receptor cells allow us to detect light intensity and light colour

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19
Q

What is the sclera

A

The white part of the eye
This tough outer structure protects the eye

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20
Q

What are the ciliary muscles and suspensory ligaments

A

They work with the lens to allow us to focus on distant or near objects

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21
Q

What is the iris

A

The colored part of the eye
It controls the size of the pupil

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22
Q

What is the pupil

A

The space in the centre of the iris which light passes through

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23
Q

Explain how low light intensity affects the size of the pupil

A

In a dark room light intensity is low
This is sensed by light receptors in the retina which send electrical impulses to the brain
The brain then sends electrical impulses to specific muscles in the iris
These muscles contract, causing the pupil to become larger
This allows more light to enter the eye
This is a reflex action as it doesn’t involve the conscious part of the brain

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24
Q

Explain how high light intensity affects the size of the pupil

A

The muscles contract causing the pupil to become smaller
This reduces the amount of light entering the eye and protects it from damage

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25
Q

What is accommodation

A

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

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26
Q

Explain how the eye focuses on distant objects

A

The ciliary muscles relaxes
Suspensory muscles are pulled tight
The lens is pulled thin
So light rays are refracted less
So light rays are focused on the retina

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27
Q

Explain how the eye focuses on near objects

A

Ciliary muscles contract
Suspensory ligaments loosen
The lens thickens so light is refracted more
So light rays are focused on the retina

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28
Q

What is hyperopia

A

People who are long sited
They can focus on distant objects
They cannot focus on nearby objects

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29
Q

Causes of hyperopia

A

The eyeball is too short so light focuses at a point behind the retina
In the elderly, the lens becomes less elastic, so the lens cannot become thick enough to focus on near objects

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30
Q

How can Hyperopia be treated

A

Convex lenses
These partially focus the light before it enters the eye

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31
Q

What is myopia

A

People who are Short Sighted
They can focus on nearby objects
They cannot focus on distant objects

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32
Q

Causes of Myopia

A

The eyeball can be too long so light is focused at a point in front of the retina
Or the lens is too thick so the light is focused infront of the retina

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33
Q

Treatment for Myopia

A

Concave lenses
This partially unfocuses the light before it enters the eye

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34
Q

What is the thermoregulatory centre

A

This is in the brain
It controls and monitors body temperature
The thermoregulatory centre contains receptors sensitive to temperature of the blood
The skin contains temperature receptors and sends nervous impulses to the thermoregulatory centre

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35
Q

When the body temperature gets too high how does the body respond

A

Sweat glands release sweat into the surface of the skin
The sweat evaporates and this takes energy from the body, cooling the body down
Blood vessels supplying the capillaries dilate (vasodilation)
This means more blood flows through the capillaries
Heat can now transfer out of the blood

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36
Q

When the body temperature gets too low how does the body respond

A

Blood vessels supplying the capillaries constrict (vasoconstriction)
Less blood now flows through the capillaries and less heat is lost from the body
Our muscles contract and relax rapidly using energy from an increased rate of respiration
This causes us to shiver and releases heat
We stop sweating when body temperature drops

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37
Q

What is the endocrine system

A

The endocrine system is composed of glands which secrete chemicals called hormones directly into the bloodstream.
The blood carries the hormones to a target organ where it produces an effect

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38
Q

Differences between the endocrine system and the nervous system

A

The nervous system uses electrical impulses which travel down neurones whereas the endocrine system uses hormones which are chemicals that are carried in the blood stream
The endocrine system produces a much slower effect than the nervous system
The endocrine system effect is more long lasting than the nervous system

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39
Q

What are the glands in the endocrine system

A

Pituitary gland
Thyroid gland
Adrenal gland
Pancreas
Ovaries
Testes

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40
Q

What is the function of the pancreas

A

Releases hormones involved in controlling the concentration of glucose in the blood

41
Q

Function of the thyroid gland

A

Releases hormones involved in growth and in regulating the body’s basic metabolic rate
Fight or flight

42
Q

Function of adrenal gland

A

Releases adrenaline which is produced in times of stress or fear

43
Q

Function of Pituitary Gland

A

Located in the brain
The master gland
Releases a number of different hormones into the blood depending on the conditions
These hormones act on other glands and cause other hormones to be released

44
Q

Function of ovaries and testes

A

Release hormones involved in puberty and in reproduction

45
Q

Describe how insulin is used to control blood glucose concentration

A

After a meal rich in carbohydrates the concentration of glucose in the blood can rise
This is sensed by the pancreas
The pancreas produces the hormone insulin
Insulin travels in the bloodstream all around the body and triggers body cells to take up glucose from the blood
Insulin also triggers liver cells to store excess glucose as glycogen.
This causes the concentration of glucose in the blood to return to its normal level

46
Q

Describe how type 1 diabetes works

A

The pancreas does not produce enough insulin
So when a carbohydrate reach meal is consumed the blood glucose concentration remains high as insulin is not produced

47
Q

How is type 1 diabetes controlled

A

If their blood glucose concentration rises too much they inject themselves with insulin

48
Q

What is type 2 diabetes

A

The body cells stop responding to insulin produced by the pancreas
This causes blood glucose levels to rise too high

49
Q

How is type 2 diabetes treated

A

A diet containing a controlled level of carbohydrates
This prevents the blood glucose level from rising too high
They are also advised to exercise

50
Q

What is a risk factor of type two diabetes

A

Obesity

51
Q

What happens when the blood glucose concentration falls too low

A

The pancreas releases the hormone glucagon into the bloodstream
Glucagon triggers liver cells to convert the glycogen stores back to glucose
This glucose is released into the blood causing blood glucose concentration to return to normal

52
Q

What are the ways the body loses water

A

Breathing-exhalation
Sweat- water, ions and urea are lost from the skin
Urinating-excess water,ions and urea are removed via the kidneys in the urine

53
Q

Explain how the kidneys work

A

Blood containing urea enters the kidney through an artery
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 does not contain urea anymore

54
Q

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

A

The blood passes through capillaries
Here small molecules are filtered out of the blood
These include urea, ions and water and 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

55
Q

Describe how the body deals with excess amino acids

A

We often eat more protein than the body needs
So the liver breaks down the amino acids and produces the chemical ammonia
This process is called deamination
Ammonia is toxic so the liver converts it into urea
The urea can be safely excreted by the kidneys

56
Q

Explain what happens when the blood becomes too concentrated/water levels fall

A

Pituitary gland releases the hormone ADH into the bloodstream
ADH travels to the kidneys
It causes the kidney tubules to become more permeable to water
This means more water is reabsorbed from the tubules back into the blood
Because of this less urine is produced and the amount of water in the blood rises back to its normal level
This causes the pituitary gland to stop releasing ADH

57
Q

Explain what happens when the blood becomes too dilute/ water levels rise

A

If the concentration of water in the blood rises the pituitary gland stops releasing ADH
This means that the kidneys reabsorbed less water into the blood
Now more urine is produced and the concentration of water in the blood returns back to normal

58
Q

What is kidney dialysis

A

When someone has kidney failure
If this happens the levels of water, ions and urea need to be adjusted using a machine

59
Q

Describe how kidney dialysis works

A

The patients blood passes over a semi-permeable membrane allowing urea, ions and water through
But it will not allow larger molecules such as proteins to pass through
On the other side of the membrane there is dialysis fluid
This contains normal concentrations of water and ions but it does not contain any urea
This allows 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
This means that some of the water and some of the ions will diffuse from the blood into the dialysis fluid
Because of this, the concentrations of water and ions in the patient’s blood will return to normal

60
Q

Disadvantages of Kidney Dialysis

A

It can be inconvenient as patients have to visit a hospital several times a week
They also have to eat a controlled diet so they do not produce too much urea

61
Q

Describe what a kidney transplant is

A

The diseased kidney is replaced with a healthy kidney from a donor.

62
Q

Disadvantages of kidney transplants

A

The donated kidney may be rejected by the patient’s immune system

63
Q

Compare the advantages and disadvantages of kidney transplant and dialysis

A

In dialysis there is no shortage of dialysis machines whereas in kidney transplant there is a shortage of donors.

With dialysis patients require frequent treatments and a controlled diet whereas a transplant allows patient to lead a normal life .

Dialysis is expensive in the long term whereas kidney transplant is only expensive initially.

Kidney transplant patients have to take anti rejection drugs for the rest of their lives

64
Q

What does testosterone do

A

Stimulates the testes to produce sperm

65
Q

What is ovulation

A

The ovary releases an egg every 28 days

66
Q

Describe the menstrual cycle

A

The uterus lining thickens and becomes spongy
The egg makes its way down to the uterus
If sperm is present the egg can be fertilized
If the egg does not get fertilized then both the egg and uterus lining are released

67
Q

What is the function of FSH

A

Follicle Stimulating hormone causes an egg to mature in the ovary

68
Q

What is the function of LH

A

Luteinising hormone causes this egg to be released, in other words ovulation

69
Q

What is the function of oestrogen and progesterone

A

Oestrogen and progesterone are involved in maintaining the uterus lining

70
Q

Explain how hormones interact in the menstrual cycle

A

In the first stage, FSH is released by the pituitary gland
FSH travels in the blood to the ovaries where it causes an egg to mature
FSH triggers the ovaries to make oestrogen
Oestrogen causes the lining of the uterus to become thick
Oestrogen stops the pituitary gland from releasing any more FSH
The pituitary gland now releases LH
LH triggers ovulation so the mature egg is released
Once the egg is released the ovary now produces progesterone
Progesterone stops the pituitary gland from releasing FSH and LH
Progesterone keeps the lining of the uterus thick in case a fertilized egg implants
If fertilisation does not take place, levels of progesterone falls
The uterus lining and the egg are now released and the women has a period

71
Q

What is contraception

A

Ways to prevent fertilization

72
Q

What are contraceptive methods

A

Contraceptive pill
Implant
Skin patch
Injection
Condom
IUD
Sterilization

73
Q

Explain how a contraceptive pill works

A

These contain hormones which prevent the body from producing FSH
This prevents any eggs from maturing

74
Q

Evaluate the contraceptive pill

A

One advantage of the contraceptive pill is that it’s highly effective if it’s taken correctly
A disadvantage is that it must be taken everyday. If a woman forgets to take it there is a risk of pregnancy
Some pills have a risk of side effects such as an increased risk of cancer or blood clots

75
Q

Explain the use of an implant, skin patch, or an injection in contraception

A

These contain progesterone
The progesterone stops eggs from maturing or being released

76
Q

Evaluate the use of a skin patch, injection, or implant in contraception

A

The advantage of these is that they are more convenient than taking a daily pill
However, these can have side effects like any other form of hormonal contraception
None of these protect against STI’s

77
Q

What is a barrier method in contraception

A

These include a condom or a diaphragm
These prevent the sperm from reaching an egg
They are an effective form of contraception if used correctly

78
Q

Evaluate barrier methods of contraception

A

An advantage is that because they do not use hormones they don’t have side effects
Condoms can reduce the risk of STI’s
However a disadvantage of a condom is that they can break or slip off

79
Q

Explain what spermicide gel does in contraception

A

Spermicides kill or disable sperm and they reduce the chances of fertilization

80
Q

Explain what an IUD is in contraception

A

These can prevent an embryo from implanting
Some coils also release hormones to reduce the chances of fertilisation

81
Q

Evaluate an IUD in contraception

A

It’s highly effective and can prevent pregnancy for up to ten years
They have very few side effects
However, an IUD doesn’t protect against sexually transmitted infections

82
Q

Explain sterilisation/surgical forms of contraception

A

This is called sterilisation
In women this prevents the egg from reaching the uterus
In men this prevents the sperm from leaving the penis

83
Q

Evaluate sterilization in contraception

A

They are highly effective
However, they are very difficult to reverse so a person has to be certain they never want children
They do not protect against STI’s

84
Q

Evaluate abstaining from intercourse in contraception

A

This is a natural form of contraception
The problem is that it’s very hard to tell when a woman has ovulated making it difficult
This doesn’t protect from STI’s

85
Q

What is a fertility drug

A

FSH and LH are given to a woman causing her to ovulate more than usual increasing her chance of becoming pregnant

86
Q

What is IVF

A

In-vitro fertilization
Fertilisation takes place outside the body
During IVF the mother is first treated with FSH and LH
this causes several eggs to mature
These eggs are then collected from the mother
Sperm from the father is collected and used to fertilize the eggs in the laboratory
The fertilized eggs then develop into embryos
Once the embryos are tiny balls of cells these are inserted into the mothers uterus
These embryos can then develop inside the mother

87
Q

Evaluate IVF

A

It gives the woman a chance to have a baby of her own
However the success rates are low
IVF is emotionally very stressful for the parents
It’s physically demanding on the mother
IVF can lead to multiple births which is risky for both the babies and the mother
Not all the embryos created will be transferred into the mother
This means that they are destroyed and some people find it unethical
IVF is also expensive

88
Q

Explain the role of adrenaline in the body

A

During times of fear or stress the adrenal glands produce adrenaline
This is released into the blood
This increases the heart rate
Because the heart is beating faster more oxygen and glucose are delivered in the blood to the brain and muscles
Both oxygen and glucose are needed for aerobic respiration
This prepares the body to either fight or run away
This is called fight or flight

89
Q

Explain the role of thyroxine in the body

A

The thyroid gland releases thyroxine
Thyroxine stimulates the body’s basal metabolic rate meaning it makes the body’s chemical reactions take place at a faster rate
Thyroxine plays an important role in growth and in development.

90
Q

Explain negative feedback of thyroxine

A

The level of thyroxine in the blood it monitored by the brain .
When the thyroxine levels falls the pituitary gland releases the hormone TSH into the bloodstream
TSH triggers the thyroid gland to release more thyroxine into the blood
The increased level of thyroxine is now detected by the brain
This prevents the pituitary gland from releasing TSH
As the TSH level falls the thyroid gland releases less thyroxine
This is called a negative feedback cycle

91
Q

What is phototropism

A

When plants shoot grow towards the light

92
Q

Describe how plant use hormones to respond to light

A

Auxin is produced at the very tip of the shoot
In shoots auxin triggers cell growth
Light causes auxin to concentrate on the darker side of the shoot tip
Cells on the darker side grow faster than cells on the lighter side
This causes the shoot to grow towards the light

93
Q

What is gravitropism

A

When plant roots grow towards the force of gravity

94
Q

Describe how plant use hormones to respond to gravity

A

Auxin is produced in the root but gravity causes the auxin to concentrate on the lower side
In roots auxin inhibits cell growth
So the lower side grows more slowly than the upper side
This causes the roots to grow towards the force of gravity

95
Q

What is Giberellins

A

Giberellins are important in starting the germination of seed

96
Q

What is ethene

A

The chemical ethene controls cell division and the ripening of fruits

97
Q

Uses of auxin

A

Weedkillers eg in gardens
Used as rooting powders
Promoting growth in tissue culture

98
Q

Uses of Gibberellins

A

Can be used to end seed dormancy
Can be used to encourage plants to flower
Can be used to make fruit grow larger

99
Q

Uses of ethene

A

Ethene is used to trigger bananas to ripen just before they are sold in the UK

Biology (10 decks)

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