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homeostasis and response (P2) Flashcards

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1
Q

Define homeostasis

A

the regulation of internal conditions to maintain a stable internal environment

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2
Q

Name the 3 things that homeostasis has to control to maintain a stable environment

A

1) water levels
2) body temperature
3) blood glucose concentration

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3
Q

Explain how negative feedback counteracts when levels of something (e.g water or temperature) are too high

A

RECEPTORS detect a a stimulus levels is too high

COORDINATION CENTRE receives and processes the information then organises a response.

EFFECTORS carry out response so levels drop which counteracts the change which restores optimum level.

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4
Q

Explain how negative feedback counteracts when levels of something (e.g water or temperature) are too high

A

RECEPTORS detect stimulus level is too low.

COORDINATION CENTRE receives and processes the information then organises a response..

EFFECTORS carry out response so levels decrease to counteract the change which restores optimum level.

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5
Q

What are receptors? give an example

A

The cells that detect stimuli.

e.g taste receptors on tongue
sound receptors in ears

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6
Q

What makes up the Central Nervous system in mammals?

A

Brain
Spinal cord

Connected to the body by:
Sensory neurones
Motor neurones

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7
Q

What are sensory neurones?

A

Neurones that carry information as electrical impulses from receptors to the CNS.

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8
Q

What are the motor neurones?

A

Neurones that carry information as electrical impulses from the CNS to the ffectors.

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9
Q

What are the effectors?

A

Muscles which contract in response to a nervous impulse or glands that secrete hormones in response.

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10
Q

Explain what happens in the nervous system when a bird sees a cat.

A

The receptors in the bird’s eye are stimulated.
Sensory neurones carry the information (as electrical impulses) from receptors to CNS.
CNS decides what to do about it.
The CNS sends information to the bird’s wings (the effectors) via motor neurones.
The muscles contract and the bird flies away to safety.

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11
Q

How does information moves between neurones?

A

Electrical impulse travels along to the end of neurone where it triggers the release of chemicals which diffuse across the synapse to the next neurones which then set of a new electrical impulse.

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12
Q

What are reflex actions?

A

Actions that are automatic and do not involve the conscious part of the brain.

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13
Q

Explain the stages of the reflex arc

A

A stimulus is detected by the receptors.
Impulses are sent along a sensory neurone which triggers chemicals to diffuse across synapse to the relay neurone (in CNS) to set of new electrical impulse.
When impulse reaches a synapse between relay neurone and motor neurone the same thing happens (electrical-chemical-electrical).
Impulse travel along motor neurone to the effector (e.g a muscle which contracts to pull limb away from danger).

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14
Q

Define:

cornea
iris
pupil
lens

A

Cornea- transparent outer layer that refracts light into eye

Iris- contains muscles that allow it to control the diameter of the pupil therefore how much light enters

Pupil- hole in middle of eye and allows light through

Lens- focuses light onto retina. It changes shape to see objects near and far.

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15
Q

What is the job of:

sclera
retina
ciliary muscles and suspensory ligaments
optic nerve

A

Sclera- tough, supporting wall of eye

Retina- contains receptors that are sensitive to light intensity and colour

Ciliary muscles and suspensory ligaments control the shape of the lens

Optic nerve- carries impulses from retina to the brain

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16
Q

How does the eye accommodate when focusing on a near object?

A

Ciliary muscles contract, which slacken suspensory ligaments. Lens becomes more curved which increases the amount by which it refracts light.

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17
Q

How does the eye accommodate when focusing on a far object?

A

The ciliary muscles relax, which allows suspensory ligaments to pull tight. Lens becomes less curved so it refracts light by a less amount.

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18
Q

What happens when bright light hits your eye?

A

When light receptors in the eye detect bright light, a reflex triggers the pupil to become smaller. The circular muscles in the iris contract and the radial muscles relax which reduces amount of light that can enter eye.

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19
Q

What does the eye do in dim light?

A

The opposite: The circular muscles relax and the radial muscles contract which makes the pupil wider (dilated)

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20
Q

Explain why some people are long sighted (hyperopia)?

A

The lens is the wrong shape and doesn’t refract enough or the eyeball is too short. The images of near objects are brought into focus behind the retina.

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21
Q

What glasses would people with long-sightedness (hyperopia) wear?

A

Convex lens (curves outwards) which refracts light rays so they focus on retina.

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22
Q

Explain why some people are short sighted (myopia)?

A

The lens is wrong shape and refracts too much or eyeball is too long. The images of distant objects are brought to focus in front of the retina.

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23
Q

What glasses would people with short-sightedness (myopia) wear?

A

Concave lens (curves inwards) so that light rays focus on the retina.

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24
Q

What new technologies are treatments for eye defects?

A

.Contact lenses
.Laser eye surgery
.Replacement lens surgery

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25
Compare hard and soft contact lenses.
Soft contact lenses are more comfortable but carry a higher risk of infection.
26
What are the benefits of contact lenses?
.Lightweight .Almost invisible .Convenient for activities like sport
27
How can laser eye surgery help myopia and hyperopia? Give 2 negatives.
For short sightedness, they slim down the shape of the cornea making it less powerful. For long sightedness, they change the shape of the cornea so that it's more powerful. Negatives: .infection .eyes react in a way that makes vision worse
28
What is replacement lens surgery? Give a negative.
Treats hyperopia. The natural lens of the eye is removed and replaced by and artificial lens made of clear plastic. Negative- possible damage to retina (could lead to loss of sight)
29
What is the function of the cerebral cortex?
Responsible for things like consciousness, personality, intelligence, memory, language
30
What is the function of the cerebellum?
Responsible for muscle coordination and balance.
31
What is the function of the medulla?
Responsible for unconscious activities like breathing, heartbeats
32
Describe the practical used for how caffeine affects reaction time.
1) The person being tested should sit with their arm resting on the edge of the table 2) Hold a ruler vertically between their thumb and forefinger (not touching). Thumb should be on 0 cm 3) Let o without warning and person has to catch as soon as possible 4) Measure reaction time by the distance from 0cm to where their thumb has caught it 5) Repeat 2 times to calculate a mean 6) Person tested drinks highly caffeinated drink and wait 10 mins. Then repeat 1-5.
33
Explain how negative feedback allows body temp to stay constant.
Temperature receptors pick up that body temp too high. Thermoregulatory centre receives info and triggers effectors automatically. Effectors (e.g sweat glands) produce a response to counteract change.
34
What 2 ways can your effectors decrease body temp when too hot?
. Sweat glands produce sweat which evaporates off the skin. This transfers energy to the surroundings. .Vasodilation (blood vessels dilate) near skin to allow more blood flow to surface of skin. Allows energy to be transferred to surroundings.
35
What 3 ways can effectors increase body temp when too cold?
. Hairs stand up to trap an insulating layer of air .Vasodilation of blood vessels supplying blood to skin to close of skin's blood supply. .Muscles contract automatically to shiver. This requires respiration which transfers some energy to warm the body.
36
Describe the difference between the response of nerves and hormones.
Nerves: .Quick action .Act for a short time .Act in a precise area Hormones: .Slow action .Acts for long time .Acts in more general way
37
What is type 1 diabetes? How do you control it?
= pancreas produces little or no insulin -Insulin therapy= several injections of insulin throughout the day -Limiting intake of simple carbohydrates (causes blood glucose to rise rapidly) -Regular exercise (removes excess glucose from blood)
38
What is type 2 diabetes? How do you control it?
= body cells don't respond properly to it's own insulin -carbohydrate-controlled diet -regular exercise
39
What causes glucose to levels in blood to rise in a normal body?
Eating carbohydrates
40
How does the endocrine system control high concentrations of blood glucose?
Pancreas releases insulin. Insulin causes glucose to enter liver/ muscle cells. Insulin causes glucose to be converted to glycogen. So blood glucose level falls causing glucagon to be secreted.
41
How does the endocrine system control low concentrations of blood glucose?
Pancreas releases glucagon into bloodstream. Glucagon triggers liver cells to convert glycogen into glucose. Glucose is released into bloodstream which increase blood glucose level.
42
What is a risk factor for type 2 diabetes?
Obesity
43
How does the body take in water?
Food/drink
44
How does the body lose water?
.Breathing out (water loss can't be controlled) .Sweating (no way to control loss of waste products) .Urine via kidney (waste products can be controlled)
45
What is removed in sweat?
Water, ions (e.g sodium), urea
46
What are the 3 functions of the kidneys?
. Osmoregulation (regulation of water levels) . Selective reabsorption (reabsorption of useful substances into blood) . Filtration (waste substances are filtered out of blood as it passes through the kidneys)
47
Why might blood levels fall?
-Sweating -Breathing rate increases
48
How does the endocrine system control high concentrations of blood water levels?
Pituitary gland stops releasing ADH. Less water is reabsorbed into blood by the kidneys. So more urine is produced allowing blood water levels to fall.
49
How does the endocrine system control low concentrations of blood water levels?
Pituitary gland releases ADH. ADH causes kidneys to reabsorb more water into the bloodstream from kidney tubules. As blood water levels return to normal, the pituitary gland stops releasing ADH.
50
How does a dialysis machine work?
1) Patient's blood passes over a partially permeable membrane. It allows water, ions and urea through. Doesn't allow larger molecules such as proteins and blood cells. 2) On the other side of the membrane, there is dialysis fluid. It contains normal levels of water and ions. But contains no urea allowing a concentration gradient. 3) Urea diffuses from the blood into the dialysis fluid. Dialysis fluid is constantly refreshed to allow a high concentration gradient. 4) Some water molecules and ions diffuse from blood into dialysis fluid.
51
What are the inconveniences of a dialysis machine?
.Sessions 3 times a week for 3-4 hours .Expensive for NHS to run .Patient has to eat a controlled diet as to not produce too much urea
52
What are the advantages and disadvantages of a kidney transplant?
Advantage: . Cheaper . Less time consuming Disadvantage: . Long waiting lists . Can be rejected
53
Why might a kidney be rejected?
Kidney cells would have different antigens to those of patient. So, immune system would produce matching antibodies. The kidney would be destroyed.
54
Give a male and female example of secondary sexual characteristics.
Male: facial hair Female: breasts
55
What is the main reproductive hormones in males and where is it produced? Same for female.
Males- testosterone made in the testes. Females- oestrogen made in the ovaries.
56
Explain the four stages of the menstrual cycle.
Stage 1) Menstruation starts. Uterus lining breaks down for around 4 days. Stage 2) From day 4-14, lining builds up into a thick layer full of blood vessels ready to receive fertilised egg. Stage 3) Day 14- ovulation. Egg is released. Stage 4) Wall is maintained until day 28. If no fertilised egg lands on the uterus wall, the lining starts to break down and cycle starts again.
57
Explain, in order, the role of hormones in the menstrual cycle.
1) FSH .produced in the pituitary gland .causes egg to mature in a follicle -stimulates ovaries to release oestrogen 2) Oestrogen .produced in the ovaries .causes lining of uterus to grow -stimulates release of LH -inhibits release of FSH 3) LH .produced in the pituitary gland .stimulates release of an egg 4) Progesterone .produced in the ovaries .maintains lining of uterus .when progesterone levels fall, the lining breaks down -inhibits release of FSH and LH
58
Explain 2 non-hormonal forms of contraception.
1. Condom . worn over penis to prevent sperm getting inside vagina - only form to protect against STDs 2. Diaphragm . shallow plastic cup fitted over cervix to form a barrier . used with spermicide to kill sperm.
59
Explain DRASTIC ways to avoid pregnancy including the negatives.
Sterilisation= cutting or tying fallopian tubes or sperm duct - It's a permanent procedure Natural methods= avoiding having sexual intercourse while woman is most fertile - Not very effective
60
Explain ways that hormones are used in controlling fertility. Include positives and negatives.
The pill= oral contraceptive using progesterone and oestrogen. +99% effective -Has side effects like nausea -Might forget to take The progesterone only pill +99% effective + fewer side effects -Might forget to take them IUD= T-shaped device inserted into uterus .Plastic IUD release progesterone .Copper IUDs prevent prevent sperm surviving in uterus - don't protect against STDs
61
What will women struggle to do if they have low levels of FSH?
Get pregnant as they can't get their eggs to mature.
62
What can be done to stimulate ovulation in a woman? What are the negatives?
Can be given FSH and LH in a fertility drug. -Doesn't always work and doing it multiple times can be expensive -Too many eggs could be stimulated resulting in multiple pregnancies
63
Write the steps of IVF.
.Mother is given FSH and LH to stimulate the maturation of several eggs .Eggs are collected and fertilised by sperm from father in a laboratory .Fertilised eggs develops into embryos .Once embryos are tiny balls of cells, one or two embryos are inserted into mother's uterus
64
What are the negatives of IVF
. Success rate not very high . Can lead to multiple births (can be risk to mother)
65
What is adrenaline for? How does it work?
Gets body ready for 'fight or flight' by triggering mechanism that increase supply of oxygen and glucose to the brain and muscles For example, it increases heart rate.
66
Where is adrenalin produced?
In the adrenal glands.
67
What does thyroxine do?
Regulates basal metabolic rate. Also stimulates protein synthesis for growth and development.
68
How does negative feedback control levels of thyroxine?
If the brain detects thyroxine levels are too low, the pituitary gland releases TSH into the bloodstream. TSH triggers the thyroid gland to release thyroxine into the blood. This is detected by the brain which prevents the pituitary gland from releasing TSH
69
Explain the process of how shoots grow towards the light.
1. Auxin accumulates on the shaded part of the tip of the plant 2. Auxin stimulates growth so the cells on the shaded part grow faster than the part exposed to light 3. So the shoot bends towards the light
70
Explain the process of how shoots grow away from gravity.
1. When a shoot is growing sideways, gravity causes auxin to accumulate more on the lower side of the tip 2. This causes the lower side cells to grow faster so the shoot bends upwards
71
Explain the process of how roots grow towards gravity.
1. When a root is growing sideways, gravity causes auxin to accumulate more on the lower side of the tip 2. In a root tip, extra auxin inhibits growth 3. So, cells on top grow faster and the root bend downwards
72
What 2 other chemicals in plants regulate their behaviour? What do they do?
Gibberellins- important in starting germination of seeds Ethene- controls cell division and the ripening of fruits
73
Describe the practical to investigate how light intensity affects growth.
1. Put cotton wool in 3 petri dishes and soak it with the same volume of water 2. Place 10 mustard seeds in each dish 3. Leave in a warm place and allow the seeds to germinate, watering them the same amount every day 4. Check all dishes have the same number of seedlings and measure their height with a ruler (hold seedling upright) 5. Place one dish in full sunlight, one in partial sunlight and one in complete darkness 6. Measure heights of each seedlings for consecutive days and plot in a results table 6. Calculate a mean for each day.
74
Describe the practical to investigate the effect of gravity on seedlings.
1. Place a dish of seedlings on it's side in the dark 2. Shoots will have grown away from direction of gravity and roots will have grown towards direction of gravity.
75
What are the commercial uses of auxin?
1. weedkillers 2. rooting powder 3. promoting growth in tissue culture
76
What are the commercial uses of gibberellins?
1. Force a seed to germinate earlier 2.Encourage plants to flower 3. Make fruits grow larger
77
What is the commercial use of ethene ?
Fruits (e.g bananas) are usually harvested before ripe and are transported long distances. Ethene is then used to trigger fruits to ripen just before sold in the UK.

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