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GCSE Biology > B5 - Homeostasis & Response > Flashcards

B5 - Homeostasis & Response Flashcards

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1
Q

What is kept the same in the human body?

A
  • Water levels
  • Temperature
  • Glucose levels
  • Salt levels
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2
Q

What is a stimulus?

A

A change in external environment.

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3
Q

What is a reflex?

A

An automatic and instantaneous nervous response which does not require conscious thought and helps prevent injury.

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4
Q

What is the name given to the part of the nervous system which contains only nerves?

A

The peripheral nervous system.

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5
Q

What is the hormone system called and what does it do?

A

The endocrine system - sends hormones around the body through the blood.

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6
Q

What are hormones produced by?

A

Endocrine glands.

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7
Q

What are hormones? (3 points)

A

Chemical messengers which control things that need constant adjustment in organs and cells. They have long lasting effects and act in a general way.

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8
Q

Why is homeostasis important for the body?

A

Cells need the right conditions to function properly, e.g. enzyme action.

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9
Q

What is negative feedback?

A

Receptors detect stimuli, like levels of a hormone being to high. The coordination centre organises a response and the effector produces a response which counteracts the change. The optimum level is restored.

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10
Q

Where is the pituitary gland?

A

At the base of the brain.

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11
Q

Where is the thyroid?

A

Along the front of the windpipe.

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12
Q

Where are the ovaries?

A

In the lower abdomen.

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13
Q

Where are the adrenal glands?

A

One above each kidney.

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14
Q

Where are the testes?

A

In the scrotum.

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15
Q

Where is the pancreas?

A

Behind the stomach.

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16
Q

What is the role of the pituitary gland?

A

Produces many hormones which regulate body conditions. Some of these hormones act on other glands, which produce other hormones.

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17
Q

What is the role of the thyroid?

A

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

The pituitary gland produces TSH (thyroid-stimulating hormone), which regulates production of these hormones.

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18
Q

What is the role of the adrenal glands?

A

Produce adrenaline in stressful/scary situations, to prepare for a fight or flight response.

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19
Q

What is the function of adrenaline?

A

Triggers mechanisms which increase the supply of oxygen and glucose to cells in the brain and muscles, to prepare for a fight or flight response. E.g. triggers an increased heart rate.

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20
Q

What is the role of the pancreas?

A

Monitors and control blood glucose levels: produces insulin and glucagon. Also produces enzymes.

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21
Q

How does a nervous response compare to an endocrine one?

A

Nervous: faster, short-lasting action on a precise area. Endocrine: slower, longer lasting response on a general area.

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22
Q

What are the food groups?

A

Carbohydrates, lipids and proteins.

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23
Q

What are lipids made of?

A

Glycerol and fatty acids.

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24
Q

What are the types of carbohydrates and what are they all made of?

A

All made of strings of glucose molecules:

In plants: fibre, starch, cellulose.

Animals: glycogen.

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25
Q

What are amino acids made of?

A

Glucose and nitrate.

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26
Q

What happens when blood glucose levels are too high?

A

Insulin is secreted by the pancreas and is carried by the blood to the liver. Here, the insulin triggers the liver to turn excess glucose into glycogen, which is stored in the liver and muscle cells.

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27
Q

What happens when blood glucose levels are too low?

A

Glucagon is secreted by the pancreas and is carried by the blood to the liver. Glucagon triggers the liver to convert stored glycogen into glucose, which is released back into the blood.

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28
Q

What is type 1 diabetes?

A

The pancreas produces little or no insulin, so glucose can rise to dangerous levels.

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29
Q

How is type 1 diabetes controlled and treated?

A

1) Regulation of simple carbohydrate consumption and regular exercise. 2) Insulin therapy used, involving several insulin injections per day, usually at mealtimes, to stop sugar levels getting too high. The amount of insulin needed depends on diet and activity.

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30
Q

What is type 2 diabetes?

A

Although insulin is produced, body cells don’t respond properly to, and become resistant to, the body’s own insulin. Causes blood glucose levels to rise dangerously.

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31
Q

How can type 2 diabetes be controlled?

A

Regulation of simple carbohydrate consumption and regular exercise.

If not enough, then tablets and sometimes even insulin.

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32
Q

What is the role of thyroxine?

A

Regulates basal metabolic rate, heart rate and temperature. Also stimulates protein synthesis for growth and development.

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33
Q

What stimulates thyroxine to be produced?

A

Thyroid-stimulating hormone (TSH)

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34
Q

What is thyroxine made of?

A

Iodine and amino acids.

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35
Q

What is the function of the cerebral cortex?

A

Responsible for consciousness, intelligence, memory and language.

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36
Q

What is the function of the medulla?

A

Controls unconscious activities, e.g. breathing and heartbeat.

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37
Q

What is the function of the cerebellum?

A

Responsible for muscle coordination and balance.

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38
Q

Why is it difficult to: 1) investigate brain function? 2) treat brain damage/disease?

A

The brain is very complex and delicate.

1) Many processes involve neurons in different areas.
2) Treatment carries risks such as physical damage to the brain, or functional problems, e.g. speech impairment.

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39
Q

What is the sclera?

A

The tough white outer layer of the eye.

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40
Q

What is the cornea?

A

The transparent outer layer at the front of the eye which refracts light.

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41
Q

What is the iris’ function?

A

Controls the diameter of the pupil, and therefore how much light enters the eye, so that there is enough to stimulate, but not damage, the cones.

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42
Q

What is the function of the lens?

A

Focuses and fine-tunes light onto the retina.

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43
Q

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

A

Alter the shape of the lens.

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44
Q

What is the function of the optic nerve?

A

Carries images from receptors, on the retina, to the brain.

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45
Q

How have neuroscientists studied people with brain damage to better understand the brain?

A

Matching changes in behavior/memory with a damaged area of the brain has helped scientists to map the functions of certain areas.

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46
Q

How do neuroscientists use electrical stimulation to investigate brain function?

A

By inserting an electrode into brain tissue, they can observe the effects of stimulating certain areas, and map their functions.

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47
Q

How do neuroscientists use MRI scanners to investigate brain function?

A

These produce a detailed image of the brain, showing which areas are active when people are thinking certain things. This helps map the functions of certain areas.

(Like other types of scanners, they show the brain’s anatomy well, so can be used to map areas of damage to their function.)

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48
Q

How does the eye respond to bright light?

A

1) Light receptors detect bright light.
2) Circular muscles in iris contract
3) Radial muscles relax.
4) Makes pupil smaller, reducing amount of light entering eye.
5) Protects retina = iris reflex

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49
Q

How does the eye respond to dim light?

A

1) Light receptors detect dim light.
2) Circular muscles in iris relax.
3) Radial muscles contract
4) Makes pupil larger, increasing amount of light entering eye
5) Lets more light in so can see well = iris reflex

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50
Q

What is accommodation?

A

The ability of the eye to alter its focus between near and distant objects.

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51
Q

How does the eye accommodate to focus on near objects?

A

1) Ciliary muscles contract.
2) So suspensory ligaments slacken.
3) Lens becomes more convex (fat).
4) Increases amount by which it refracts light.

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52
Q

How does the eye accommodate to focus on distant objects?

A

1) Ciliary muscles relax.
2) So suspensory ligaments tighten.
3) Lens becomes less convex (less fat).
4) Decreases amount by which it refracts light.

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53
Q

What is hyperopia?

A

Long-sightedness: inability to focus on near objects.

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54
Q

What is myopia?

A

Short-sightedness: inability to focus on distant objects.

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55
Q

Explain the cause of hyperopia.

A

1) Lens isn’t convex enough, so doesn’t refract light enough / eyeball is too shallow. 2) Images of close objects are focused behind the retina.

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56
Q

How can hyperopia be corrected?

A

Wearing glasses with a convex lens (curves outwards) which refracts light to focus on the retina.

57
Q

Explain the cause of myopia.

A

1) Lens is the wrong shape and refracts light too much / eyeball is too deep. 2) Images of distant objects are focused in front of the retina.

58
Q

How can myopia be corrected?

A

Wearing glasses with a concave lens (curves inwards) which refracts light to focus on the retina.

59
Q

Give three alternatives to glasses for correcting vision defects.

A

1) Contact lenses
2) Laser eye surgery
3) Replacement lens surgery

60
Q

What is osmoregulation?

A

The control of water and salt levels in the body.

61
Q

How do the kidneys produce urine?

A

By the filtration of the blood and the selective reabsorption of useful substances such as glucose, some ions and a certain amount of water.

62
Q

Name three substances excreted from the body in urine.

A

1) Urea 2) Ions 3) Water

63
Q

What is urea?

A

A substance converted from ammonia, which is a toxic waste product from deamination.

64
Q

Ammonia is created as a waste product of what process?

A

Deamination in the liver.

65
Q

What happens during deamination?

A

The digestion of proteins from the diet results in excess amino acids which need to be excreted safely. In the liver, these amino acids are deaminated to form ammonia. Ammonia is toxic, so is immediately converted to urea for safe excretion.

(The amine group is removed from the amino acid and converted to ammonia. The rest of the amino acid is made up of mostly carbon and hydrogen, and is recycled or oxidized for energy.)

66
Q

What happens to urea once it’s converted from ammonia?

A

Urea is transported to the kidneys via the blood, where it’s filtered out and excreted from the body in urine. A small amount of urea is also lost through sweat.

67
Q

How do ions end up in the body?

A

They are ingested in food and then absorbed into the blood.

68
Q

What happens when the ion-water balance in the body is wrong?

A

Too much or little water is drawn into cells by osmosis, meaning that cells can be damaged or don’t work as well.

69
Q

In what two ways are ions lost from the body?

A

1) Sweat (which can’t be regulated)

2) Urine (which is regulated)

70
Q

How is ion balance regulated in the body?

A

Kidneys regulate the ion balance; the right amount is absorbed back into blood after filtration, and the rest is lost through urine.

71
Q

In what ways is water lost from the body?

A

1) Sweating
2) Exhalation
3) Urine

72
Q

What hormone controls water balance in the body?

A

ADH (antidiuretic hormone).

73
Q

Where is ADH produced?

A

The pituitary gland.

74
Q

What organ monitors urine concentration?

A

The brain.

75
Q

What happens when the blood is too dilute?

A

1) Receptors in hypothalamus detect water content is too high
2) Pituitary gland releases less ADH into blood
3) Kidneys receive less ADH
4) Less water reabsorbed from kidney tubes
5) So more water released in urine

76
Q

What happens when the blood is too concentrated?

A

1) Receptors in hypothalamus detect water content is too low
2) Pituitary gland releases more ADH into blood
3) Kidneys receive more ADH
4) More water reabsorbed from kidney tubes
5) So less water released in urine

77
Q

What two treatments are available for kidney failure?

A

1) Regular dialysis 2) Transplants

78
Q

How do dialysis machines filter a patient’s blood?

A

1) Blood flows between partially permeable membranes surrounded by dialysis fluid.
2) Membranes permeable to things like ions and waste substances, but not large molecules.
3) Fluid has the same ion and glucose concentration as healthy blood, so useful substances in the blood aren’t lost from the blood.
4) Only waste substances (e.g. urea) and excess ions and water diffuse across the membrane and out of the blood.

79
Q

Why does dialysis have to be done regularly?

A

To keep the concentrations of dissolved substances at healthy, normal levels, and to remove waste substances.

80
Q

What are the disadvantages of dialysis?

A

1) Many patients have to have it 2-3 times a week, and a session lasts 3-4 hours.
2) It can cause blood clots and infections.
3) Being on a dialysis machine isn’t pleasant.
4) It’s expensive for the NHS to run.

81
Q

What is the main advantage to dialysis?

A

It can buy a patient with kidney failure valuable time until an organ donor is found.

82
Q

What are the advantages of kidney transplants?

A

1) They can come from people who are alive.
2) They are cheaper than dialysis in the long term.
3) They stop the patient needing to spend hours of their life on dialysis machines.

83
Q

What are the disadvantages of kidney transplants?

A

1) If the donor is alive, there is a small risk to them.
2) The donor kidney could be rejected by the patient’s immune system, despite drugs aimed to prevent this.
3) There are long waiting lists for suitable kidneys.

84
Q

What happens at puberty?

A

The body starts releasing sex hormones which trigger secondary sexual characteristics and cause eggs to mature in women.

85
Q

What are the primary sex hormones for males and females?

A

Males: testosterone.

Females: oestrogen and progesterone.

(Oestrogen and testosterone are produced by both sexes).

86
Q

Give 2 examples of secondary sexual characteristics.

A

Development of facial hair in men and breasts in women.

87
Q

What is the function of testosterone?

A

Controls puberty and sperm production in males.

88
Q

What four hormones control the menstrual cycle?

A

FSH, LH, oestrogen and progesterone.

89
Q

How many days long is the menstrual cycle (usually)?

A

28 days

90
Q

What happens in stage 1, day 1-4, of the menstrual cycle?

A

Menstruation: uterus lining breaks down.

91
Q

What happens in stage 2, day 4-14, of the menstrual cycle?

A

Uterus lining builds up into a thick layer ready to receive a fertilised egg.

92
Q

What happens in stage 3, day 14, of the menstrual cycle?

A

Ovulation: an egg is released from the ovary.

93
Q

What happens in stage 4, day 14-28, of the menstrual cycle?

A

The uterus lining is maintained. If no fertilised egg lands on the uterus wall by day 28, the lining breaks down and the cycle repeats.

94
Q

What do FSH and LH stand for?

A

1) Follicle-stimulating hormone.

2) Luteinising hormone.

95
Q

Where is FSH produced?

A

In the pituitary gland

96
Q

What is the function of FSH?

A

1) Causes the maturation of an egg in an ovary, in a structure called a follicle.
2) Stimulates the ovaries to produce oestrogen.

97
Q

Where is oestrogen produced?

A

In the ovaries.

98
Q

What is the function of oestrogen?

A

1) Involved in the repairing and thickening of the uterus lining.
2) Stimulates release of LH.
3) Inhibits release of FSH.

99
Q

Where is LH produced?

A

In the pituitary gland.

100
Q

What is the function of LH?

A

Stimulates ovulation (the release of an egg) at day 14.

101
Q

Where and how is progesterone produced?

A

In the ovaries, after ovulation, by the remains of the follicle.

102
Q

What is the function of progesterone?

A

1) Maintains the lining of the uterus (during 2nd half of cycle).
2) When progesterone levels fall, lining breaks down.

3) Inhibits release
of both LH and FSH.

103
Q

Why is oestrogen used in hormonal contraception?

A

It inhibits production of FSH, so egg development and production is stopped.

104
Q

How is progesterone useful in hormonal contraception?

A

1) Stimulates the production of thick mucus, which prevents sperm reaching an egg.
2) Inhibits release of FSH and LH (so eggs are not matured and released).
3) Stops a fertilised egg being implanted in the uterus

105
Q

List six hormonal methods of contraception

A

1) Combined oral pill
2) Progesterone pill
3) Patch
4) Implant
5) Injection
6) The IUD (intrauterine device, or the coil)

106
Q

What does the combined oral contraceptive pill contain?

A

Oestrogen and progesterone

107
Q

Describe the contraceptive patch

A

1) Small patch stuck to the skin.
2) Contains oestrogen and progesterone.
3) Lasts one week

108
Q

How does the contraceptive implant work?

A

1) Inserted under the skin of the arm.
2) Lasts up to 3 years.
3) Releases a continuous amount of progesterone.

109
Q

1) What does the contraceptive injection contain?

2) How long does one dose last?

A

1) Progesterone.

2) 2-3 months

110
Q

What is the intrauterine device? There are 2 main types; describe how each works.

A

T-shaped device which is inserted into the uterus.

2 main types:

1) plastic IUDs release progesterone, preventing implantation of a fertilised egg.
2) copper IUDs prevent sperm surviving in the uterus.

111
Q

What are the two categories of non-hormonal contraceptives?

A

1) Barriers

2) More drastic methods

112
Q

List 3 barrier methods of contraception.

A

1) Condoms/femidoms
2) Diaphragms
3) Spermicides

113
Q

__ are the only form of contraception that protect against STIs.

A

Condoms

114
Q

How do diaphragms work?

A

1) Shallow plastic cups that fit over the cervix (entrance to the uterus) to form a barrier.
2) Have to be used with spermicides.

115
Q

1) How do spermicides work?

2) How effective are they?

A

1) Substances which disable/kill sperm.

2) Only 70-80% effective.

116
Q

List 3 more drastic non-hormonal methods of contraception.

A

1) Sterilisation
2) Natural method
3) Abstinence

117
Q

What does sterilisation involve?

A

The fallopian tubes (which connect the ovaries to the uterus) or the sperm duct (the tube between the testes and penis) are cut or tied.
This is permanent procedure, but there is a very small chance that the tubes can rejoin.

118
Q

What is the natural method of contraception?

A

Pregnancy may be avoided by avoiding sexual intercourse on the days a woman is most fertile in the menstrual cycle. The method is not very effective.

119
Q

Why can’t some women get pregnant?

A

They have FSH levels too low to cause their eggs to mature. No eggs are released - they cannot be fertilised.

120
Q

Name two options that help a woman get pregnant if she has fertility problems.

A

1) LH and FSH can be taken in a fertility drug to stimulate ovulation.
2) If that doesn’t work, IVF.

121
Q

What are the cons of the fertility drug containing LH and FSH?

A

1) Doesn’t always work - repeating it gets expensive.

2) Too many eggs can be fertilised, resulting in unexpected multiple pregnancies.

122
Q

Describe the process of IVF treatment.

A

1) A woman takes FSH and LH, so that several eggs mature in her ovaries.
2) The eggs are collected and fertilised with a man’s sperm.
3) Alternatively, if the man has a low sperm count, ICSI (intracytoplasmic sperm injection) is used: the sperm is directly injected into the egg.
4) The fertilised eggs are grown into embryos in a laboratory incubator.
5) Once the embryos become tiny balls of cells, 1 or 2 are transferred to the woman’s uterus, to hopefully impregnate her.

123
Q

Give 3 cons of IVF treatment.

A

1) Multiple births are possible, which risk miscarriages or stillbirths.
2) Success rate is low.
3) Some women react strongly to the hormones, e.g. abdominal pain, vomiting or dehydration.

124
Q

How have advances in technology improved the techniques of IVF treatment?

A

1) There have been advances in microscope techniques and micro tools, used for genetic testing (checking an embryo is healthy).
2) Time lapse imaging has been invented. The growth of embryos is monitored to determine those that are more likely to result in a successful pregnancy.

125
Q

Why are some people against IVF treatment?

A

1) It often results in unused embryos being destroyed - this is considered unethical because they are potential human lives.
2) The genetic testing of embryos before implantation raises ethical issues, as it risks leading to the selection of preferred characteristics.

126
Q

What is auxin and what is its function?

A

A plant hormone which controls growth in response to light in the tips of shoots (phototropism) and in response to gravity in the tips of roots (gravitropism).

An uneven distribution of auxin causes an unequal growth rate of regions of cells within shoots/roots, causing them to bend in the right direction.

127
Q

Where is auxin produced?

A

The tips of shoots.

128
Q

What may happen to a shoot if the tip is removed?

A

Auxin is produced here, so removing the shoot means no auxin is available. Auxin is responsible for plant growth; the shoot may stop growing.

129
Q

Explain how and why vertical shoots grow towards light.

A
  • When a shoot’s tip is exposed to light, more auxin accumulates in the shaded side than in the side in the light.
  • The imbalance of auxin causes cells in the shaded side to elongate more.
  • This makes the shoot bend towards light.
  • This is called phototropism.
130
Q

Explain how and why horizontal shoots grow away from gravity.

A
  • When a shoot grows sideways, gravity produces an unequal distribution of auxin in the tip; more accumulates in the lower side.
  • The imbalance of auxin causes cells in the lower side to elongate faster.
  • This makes the shoot bend away from gravity and towards light.
  • This is called gravitropism.
131
Q

Explain how and why horizontal roots grow towards gravity.

A
  • When a root grows sideways, gravity produces an unequal distribution of auxin in the tip: more accumulates in the lower side.
  • The imbalance of auxin inhibits growth of cells in the lower side - they elongate slower than in the upper side.
  • This makes the root bend towards gravity.
  • This is called gravitropism.
132
Q

Explain why the tropic responses of shoots and roots are important in the lives of plants.

A

When seeds are dispersed, they can fall any way up in the soil. Tropic responses ensure that, when the seed starts to germinate:

  • the roots grow downwards (to anchor the plant and take up water and minerals)
  • the shoots grow towards light (maximum photosynthesis).
133
Q

What is the role of ethene as a plant hormone?

A

Controls growth (cell division) and ripening of fruits.

134
Q

What is the role of gibberellin as a plant hormone?

A

Important in initiating seed germination; stimulates stem growth and flowering.

135
Q

How are auxins used in agriculture and horticulture? Give 3 examples.

A
  • used as weed killers (in selective herbicides which are sprayed onto leaves to disrupt growth patterns. Weeds are mostly broad-leafed, with high surface areas, so these absorb more herbicide and are killed)
  • used as rooting powders (to make cuttings produce roots and grow into plants, enabling rapid cloning of good plants)
  • used for promoting growth in tissue culture cloning (added to growth mediums to stimulate cell division)
136
Q

How are gibberellins used in agriculture and horticulture?

A

Used to:

  • alter seed dormancy (makes them germinate at times of year that they naturally wouldn’t, and makes all the seeds in one batch germinate at once)
  • promote flowering (some plants need certain conditions to flower - gibberellin makes them flower without any changes in environment. Also used to grow bigger flowers)
  • increase fruit size (used in seedless varieties of fruit which don’t tend to grow as large)
137
Q

How is ethene used in the food industry?

A
  • speeds ripening of fruit whilst on plants, and during storage and transport
  • fruit can be picked when unripe, then ripened with ethene during transport for optimal ripeness in supermarkets
  • ripening can be delayed during storage by using chemicals which block the effect of ethene, inhibit ethene production or remove it from the air
138
Q

How does how the everyday use of hormones as weed killers have an effect on biodiversity?

A

Selective weedkillers only kill broad-leaved plants, leaving grasses and crops with narrow leaves untouched. Therefore, biodiversity is reduced as some types of plant are killed.

GCSE Biology (7 decks)

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