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GCSE Biology Paper 2 > Homeostasis and Response > Flashcards

Homeostasis and Response Flashcards

1
Q

What is homeostasis?

A

The regulation of conditions in the body and cells to maintain a stable internal environment

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2
Q

What are the body’s two main communication systems for homeostasis?

A

The nervous and hormonal communication systems

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3
Q

What are the three components of all our automatic control systems?

A

Receptor cells, coordination centres (e.g. the brain, spinal chord and pancreas) and the effectors

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4
Q

What is negative feedback?

A

The control systems’ mechanism of recognising that something (e.g. temperature) is too high or too low and bringing it back to normal

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5
Q

How does the body use negative feedback in response to something being too high or too low?

A

receptor detects a stimulus —> coordination centre recieves and processes the information and then organises a response —> effector produces the response and counteracts the change

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6
Q

How the process of negative feedback sometimes cause the opposite problem?

A

The effector will continue producing the response as long as the coordination centre stimulates it which means it can sometimes go to far and cause the opposite problem, starting the cycle over again

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7
Q

What is the central nervous system (CNS) and what is it made up of?

A

A coordination centre. In vertebrates, made up of the brain and spinal cord. Connected to the body by sensory neurones and motor neurones

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8
Q

What do sensory neurones do?

A

Carry information as electrical impulses from the receptors to the CNS

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9
Q

What do motor neurones do?

A

Carry electrical impulses from the CNS to the effectors

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10
Q

What are the effectors?

A

All muscles and glands, which respond to nervous impulses and bring about a change. E.g. muscles contract and glands secrete hormones

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11
Q

What are receptors?

A

Cells that detect stimuli. There are many different types like taste (on the tongue) and sound (in the ears). They form parts of larger organs like the light receptors that make up the retina of the eye.

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12
Q

What is a synapse and how are nerve signals transferred across it?

A

The connection between two neurones. Nerve signals are transferred by chemicals which diffuse across it, setting off a new signal in the next neurone

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13
Q

What are reflexes?

A

Rapid, automatic responses to certain stimuli that don’t involve the conscious part of the brain, they can reduce the chance of being injured. e.g. pupils shrinking in bright light

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14
Q

What is a reflex arc?

A

The passage of information from the receptor to effector in a reflex

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15
Q

What is the process of a reflex arc?

A

Exposure to a stimulus —> Stimulation of the receptor —> impulses travel along sensory neurone —> impulse passed onto relay neurone —> impulse travels along motor neurone —> impulse reaches effector and it reacts

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16
Q

How can you measure a reaction time using a ruler?

A
  • person sits with arm resting on table
  • someone holds a ruler between their thumb and forefinger
  • let go without notice and the person tries to grab the ruler as quickly as possible
  • measure the time by how high up they caught the ruler
  • repeat several times and calculate a mean
  • they should then drink a caffeinated drink and repeat the experiment
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17
Q

How can you measure reaction time using a computer? Why is this considered more precise?

A

by having someone press a mouse or a key when the screen changes colour. It’s considered more accurate because it removes the possibility of human error, record the time in seconds and predict when someone will respond.

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18
Q

What is the cerebral cortex responsible for?

A

consciousness, intelligence, memory and language.

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19
Q

What does the medulla in the brain do?

A

Control unconscious activities e.g. breathing and the heartbeat.

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20
Q

What is the cerebellum in the brain responsible for?

A

Muscle coordination

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21
Q

What three methods do scientists use to study the brain? Say a bit about each one.

A
  • Studying brain damage - seeing what effect damage in a certain part of the brain has on a patient can tell you what that part of the brain does.
  • Electrical stimulation - electrode put into brain tissue, stimulating it to see what that part does.
  • MRI scans - produces detailed pictures of the brain’s structure.
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22
Q

What are the risks of experiments and treatment on the brain?

A

Could cause physical damage on the brain or increased problems with brain function.

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23
Q

What are the 9 different parts of the eye and what do they do?

A
  • Sclera - tough, supporting wall
  • Cornea - transparent outer layer at the front, refracts light
  • Iris - contains muscles that control the diameter of the pupil
  • Pupil - controls how much light gets into the eye
  • Lens - focuses light into the retina
  • Retina - contains receptor cells for light and colour
  • Ciliary Muscles and Suspensory Ligaments - control the shape of the lens
  • Optic Nerve - carries impulses from the receptors to the brain
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24
Q

How does the reflex work that the eyes use to react to bright light, protecting the retina?

A
  • light receptors in the eye detect the bright light
  • triggers reflex
  • circular muscles in the iris contract and the radial muscles relax
  • less light gets into the eye
  • opposite happens in dim light
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25
Q

What happens in the eye to look at near objects?

A
  • ciliary muscles contract
  • suspensory ligaments slacken
  • lens becomes fat
  • increases refraction of light
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26
Q

What happens in the eye to look at distant objects?

A
  • ciliary muscles relax
  • suspensory ligaments pull tight
  • lens becomes thin
  • decreases the refraction of light
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27
Q

What causes hyperopia (long-sightedness)?

A

The lens is the wrong shape and doesn’t refract the light enough. This means near objects are brought into focus behind the retina. This can be fixed with a convex lens which curves outwards.

28
Q

What cause myopia (short-sightedness)?

A

The lens is the wrong shape and refracts light too much. Distant objects are brought into focus in front of the retina. Can be fixed with a concave lens which curves inwards.

29
Q

What are the three treatments for vision defects? What are advantages and disadvantages?

A
  • contact lenses - lightweight and convenient. Can be hard (less risk of infection) or soft (more comfortable)
  • laser eye surgery - vaporises tissue, changing the shape of the cornea. Very precise. Risk of complications.
  • Replacement lens surgery - natural lens replace for an artificial one. High risk.
30
Q

How does the body react when it’s core temperature is too high or too low?

A

Temperature receptors detect that it’s too hot —> thermoregulatory centre receives the information and triggers the effectors —> effectors like sweat glands responf to counteract the change

31
Q

What does it mean if effectors work antagonistically?

A

That they work against each other to achieve and maintain a very precise result. E.g. some cool and heat up to maintain a precise temperature.

32
Q

What are the effectors that react when the body is too hot?

A
  • sweat is produced and evaporates, tranferring heat to the environment
  • blood vessels dilate so more blood flows closer to the skin (vasodilation)
33
Q

What are the effectors that react when the body is too cold?

A
  • hairs stand up to trap an insulating layer of air
  • stops the production of sweat
  • blood vessels constrict to close off the skin’s blood supply (vasoconstriction)
  • shivering uses respiration which transfers energy
34
Q

What are hormones?

A

Chemical molecules released directly into the blood and carried around the body to their target organs. They are produced by endocrine glands which make up the endocrine system

35
Q

What does the pituitary gland do?

A

It produces many hormones that act on other glands, directing them to release their own hormones

36
Q

What does the thyroid do?

A

Produces thyroxine which regulates things like the rate of metabolism, heart rate and temperature

37
Q

What does the pancreas do?

A

It produces insulin which is used to regulate blood glucose levels

38
Q

What is the difference between nerve responses and hormone responses?

A

Nerve responses are very fast and act on a precise area for a very short time. Hormone responses are slower but they act for a longer time in a more general way.

39
Q

How does the body use a negative feedback cycle to handle blood glucose level being too high?

A

insulin is secreted by the pancreas —> the glucose is removed from the blood, into the liver and muscle cells –> The insulin makes the liver turn the glucose into glycogen to be stored.

40
Q

How does the body use a negative feedback cycle to handle blood glucose level being too low?

A

glucagon is secreted by the pancreas —> glucagon tells the liver to release more glucose —> liver turns glycogen into glucose and releases it into the blood

41
Q

What is type 1 diabetes and how is it treated?

A

When the pancreas produces little or no insulin so the blood glucose can reach fatal levels. They have to take insulin injections for it, different amounts depending on their diet and exercise.

42
Q

What is type 2 diabetes and how is it treated?

A

When a person becomes resistant to their own insulin which can cause dangerous blood glucose levels. This can be controlled with a monitored diet and regular exercise.

43
Q

What are the waste substances that the kidneys remove from the body in urine using selective reabsorption? Say a bit about each one.

A
  • UREA - proteins and amino acids are converted into fats and carbohydrates through deamination. This produces ammonia, a toxic waste product.
  • IONS - some, like sodium are taken in through food. Need a balanced amount in the body. Some are lost in sweat but the kidneys have to regulate it.
  • WATER - lost from sweat and in the lungs from breathing in and out. This isn’t regulated so the kidneys balance it out
44
Q

What hormone regulates the concentration of urine?

A

Anti-diuretic hormone (ADH). When the coordination centre in the brain senses that in-balanced water content and tells the potuitary gland which then either increases or decreases the amount of ADH being released.

45
Q

How does dialysis work?

A
  • blood flows through partially permeable membranes surrounded by dialysis fluid
  • the fluid has the same concentration of ions and glucose as healthy blood which establishes a concentration gradient
  • only waste substances diffuse across the membrane
46
Q

What are the pros and cons of dialysis?

A

It takes 3-4 hours and has to be done 3 times a week, very time consuming. Can be painful and expensive. But it gives people time to find a donor

47
Q

What are the pros and cons of a kidney transplant?

A

Small risk to those donating, if alive. Can be rejected by the recipient’s immune system. Long waiting list. But they are cheaper than dialysis and provide a permanent cure.

48
Q

What are the reproductive hormones in men and women and where are they produced?

A
  • MEN - testosterone - produced in testes
  • WOMEN - oestrogen - produce in ovaries
49
Q

What are the 4 stages of the menstrual cycle?

A
  • Day 1 - menstruation starts
  • Day 4-14 uterus lining builds up into a thick spongy layer full of blood vessels
  • Day 14 - Egg developed and released (ovulation)
  • Day 14-28 - if egg not fertilised, uterus lining starts to break down again
50
Q

What are the four hormones involved in the menstrual cycle? Where are they produced? What do they do?

A
  • FSH - pituitary gland - matures egg in the follicle in the ovaries - stimulates ovaries to produce oestrogen
  • LH - pituitary gland - stimulates ovulation
  • Oestrogen - ovaries - grows uterus lining and stimulates the release of LH
  • Progesterone - ovaries by the remains of the follicle - maintains uterus lining and inhibits the release of LH and FSH
51
Q

The contraceptive pill contains oestrogen and progesterone. How do this work?

A
  • taking oestrogen everyday inhibits FSH production, which eventually stops egg development and production
  • progesterone stimulates the production of a thick mucus which stops the sperm from getting to the egg
52
Q

What are some of the other contraceptive methods? How does each one work?

A
  • the patch - contains oestrogen and progesterone, sticks to the skin, lasts one week
  • implant - put into the arm, releases continuous progesterone, lasts three years
  • injection - contains progesterone, lasts 2 to 3 months
  • IUD - put into uterus, kills sperm
53
Q

What are the non-hormonal method of contraception? How does each one work?

A
  • condoms - worn over the penis, female ones worn inside the vagina, protect against STDs
  • diaphragms - shallow plastic cup that goes over the cervix
  • spermicide - a substance that disable of kills sperm, can be used on its own or with one of the others
54
Q

What are some of the non-contraceptive ways to avoid pregnancy?

A
  • Sterilisation - cutting or tying the fallopian tubes or sperm ducts
  • Planning and Timing - finding out when the menstrual cycle is at its most fertile and avoiding sex
  • Abstinence - not having inctercourse
55
Q

How can hormones be used to increase fertility in women?

A

By taking a fertility drug containing FSH and LH to stimulate ovulation. But this can be expensive and could result in twins or triplets.

56
Q

What is the IVF process?

A
  • eggs collected from ovaries
  • Intra-Cytoplasmic Sperm Injection (ICSI) where sperm is injected into the egg
    -fertilised eggs grown into embryos in a lab incubator
  • one or two embryos transferred to the uterus
57
Q

What are the negatives of IVF treatment?

A
  • multiple births, which can be risky
  • low success rate, very stressful and upsetting
  • the hormones can result in some severe side effects
  • unused embryos are destroyed which many see as immoral and unethical
58
Q

How does adrenaline ready the body for fight or flight?

A

It triggers mechanisms that increase the supply of oxygen and glucose to the cells in the brain and muscles.

59
Q

What is the basal metabolic rate?

A

The speed of the chemical reaction of the body while it is at rest.

60
Q

How does thyroxine regulate the metabolism?

A

Thyroid stimulating hormone (TSH) released by the pituitary gland —> thyroxine released —> negative feedback maintains level of thyroxine in the blood

61
Q

What is auxin and where is it produced?

A

A plant hormone that controls growth near the tips and shoots and roots, controlling the growth of a plant in response to light (phototropism) and gravity (gravitropism or geotropism). It’s produced in the tips of the shoot.

62
Q

How is the growth of a plant shoot affected by exposure to light?

A

More auxin accumulates on the side in the shade, making the cells on that side grow faster so the shoot bends towards the light

63
Q

How is the growth of a plant shoot affected by gravity?

A

When it’s growing sideways, gravity pulls the auxin down. This means the lower side grows faster, bending the root upwards. But in the roots auxin inhibits growth so the roots will bend downwards.

64
Q

How can you investigate plant growth responses?

A
  • put 10 cress seeds into three different Petri dishes lined with moist filter paper
  • shine light from above on one of them and different directions on the other two
    -leave them alone for a week and they will have grown towards the light
65
Q

What are some of the uses of auxins?

A
  • Killing weeds - can be targeted to stop the growth of specific plants
  • Growing from cuttings with rooting powder
  • Growing cells in tissue culture - grows clones of a plant from its cells
66
Q

What are the uses of Gibberellins within a plant?

A
  • controlling dormancy - to make seeds germinate at a time of the year when they usually wouldn’t
  • inducing flowering - helps plants flower without changes to their environment
  • growing large fruit - can help seedless versions of fruit (which are normally smaller) grow to the normal size
67
Q

How is ethene produced and what is it used for?

A

Produced by aging parts of a plant. Controls cell division, influencing growth. Stimulates enzymes that cause ripening.

GCSE Biology Paper 2 (3 decks)

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