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Biology > Topic 5: Homeostasis and Response > Flashcards

Topic 5: Homeostasis and Response Flashcards

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1
Q

Define ‘homeostasis’

A

The regulation of 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 3 things have to be maintained in the human body?

A

Blood glucose concentration, body temperature and water levels

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3
Q

What are the 3 components of your automatic control system?

A

Receptors, coordination centres and effectors

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4
Q

What do receptors do?

A

Detect stimuli

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5
Q

What do coordination centres do?

A

Receive and process information from receptors

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6
Q

What do effectors do?

A

Bring about responses to restore optimum levels

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7
Q

How are nerve cells adapted to carry electrical impulses?

A

Long, thin and have branched connections

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8
Q

Explain how electrical impulses move between neurons [3]

A
  1. Connection between 2 neurons is called a synapse
  2. Nerve signal is transferred by chemicals which diffuse across the gap
  3. Chemicals then set off a new electrical signal to the next neuron
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9
Q

Describe the reflex arc [8 steps]

A

Stimuli, receptor, sensory neurone, CNS, relay neurone, motor neurone, effector, response

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10
Q

Why are reflexes important?

A

They protect us from harm

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11
Q

Where is the Cerebral cortex located?

A

Top of the brain

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12
Q

MILC

What is the Cerebral cortex responsible for?

A

Memory, intelligence, language and consciousness

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13
Q

Where is the Cerebellum located?

A

Back of the brain

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14
Q

What is the Cerebellum responsible for?

A

Muscles coordination

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15
Q

Where is the Medulla located?

A

Bottom of brain/by spinal cord

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16
Q

What is the Medulla responsible for?

A

Unconscious activities (breathing and heartbeat)

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17
Q

What 3 methods are used to study the brain?

A
  1. Studying patients with brain damage
  2. Electrically stimulating the brain
  3. MRI scans
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18
Q

Why is investigating the brain so difficult?

A

Due to its complexity and delicacy

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19
Q

What is the job of the sclera?

A

Supports the eye

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20
Q

What is the job of the cornea?

A

Refracts light into the eye

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21
Q

What is the job of the iris?

A

Controls how much light can enter the pupil

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22
Q

What is the job of the lens?

A

Refracts and focuses light onto the retina

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23
Q

What is the job of the retina?

A

To capture the light and colour which enters the eye

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24
Q

What do the ciliary muscles and suspensory ligaments do?

A

Control the shape of the lens

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25
Q

What does the optic nerve do?

A

Carries impulses from the receptors of the retina to the brain

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26
Q

What happens to your pupil in bright light and how?

A
  1. Your pupil gets smaller
  2. The circular muscles contract
  3. The radial muscles relax
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27
Q

Why does you pupil constrict in bright light?

A

To reduce the amount of light that can enter the eye - protects retina

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28
Q

What happens to your pupil in dim light and how?

A
  1. Your pupil gets bigger
  2. The radial muscles contract
  3. The circular muscles relax
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29
Q

Why does your pupil dilate in dim light?

A

To allow more light to enter the eye

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30
Q

What happens to focus on near objects?

A
  1. The ciliary muscles contract
  2. The suspensory ligaments slacken
  3. The lens is thicker and refracts light rays strongly
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31
Q

What happes to focus on distant objects?

A
  1. The ciliary muscles relax
  2. The suspensory ligaments become taught
  3. The lens is thinner and only slightly refracts light
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32
Q

What causes long-sightedness?

A

The lens doesn’t refract the light enough - image appears behind the retina

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33
Q

How can long-sightedness be fixed?

A

Use glasses with convex lenses - increases the refraction

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34
Q

What is the medical term for long-sightedness?

A

Hyperopia

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35
Q

What causes short-sightedness?

A

The lens refracts light too much - image appears before the retina

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36
Q

How can short-sightedness be fixed?

A

Use glasses with concave lenses - counteracts the over-refraction

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37
Q

What is the medical term for short-sightedness?

A

Myopia

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38
Q

Pros of contact lenses

A

More convenient than glasses for sports etc

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39
Q

Cons of contact lenses

A

Risk of eye infections

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40
Q

Pros of laser eye surgery

A

Can fix hyperopia and myopia

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41
Q

Cons of laser eye surgy [2]

A
  1. Risk of infection
  2. Making vision worse than before
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42
Q

Pros of replacement lens surgery

A

Can fix hyperopia

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43
Q

Cons of replacement eye surgery

A

Can cause damage to retina

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44
Q

What does the body do when it’s too hot? [3]

A
  1. Hairs lie flat
  2. Blood vessels expand (vasodilate)
  3. Sweat
45
Q

How does vasodilation cool you down?

A

More blood flows close to the skin’s surface, so heat energy is transferred to the surroundings

46
Q

How does sweating cool you down?

A

As sweat evaporates, it transfers heat energy to the surroundings

47
Q

What does the body do when it’s too cold? [3]

A
  1. Blood vessels constrict (vasoconstrict)
  2. Hairs stand on end
  3. Shiver
48
Q

How does vasoconstriction warm you up?

A

Less blood flows close to the skin’s surface, so less heat energy is lost

49
Q

How do hairs standing on end warm you up?

A

Traps a layer of insulating air, so harder to lose heat from skin

50
Q

How does shivering warm you up?

A

Requires respiration which creates heat energy as waste

51
Q

Which part of the brain controls body temperature?

A

Hypothalamus

52
Q

Describe the pathway of the endocrine system [3]

A
  1. Glands secrete hormones into bloodstream
  2. Blood carries hormone to target organs
  3. An effect is produced
53
Q

What is the brain’s ‘master gland’?

A

Pituitary gland

54
Q

What does the pituitary gland do?

A

Produces hormones which act on other glands to secrete their hormones

55
Q

What does the thyroid produce?

A

Thyroxine

56
Q

What does thyroxine do?

A

Regulates metabolism

57
Q

What does the adrenal gland produce?

A

Adrenaline

58
Q

What does adrenaline do?

A

Prepares your body for a ‘fight or flight’ response

59
Q

What does the pancreas produce?

A

Insulin

60
Q

What does insulin do?

A

Regulates blood glucose levels

61
Q

What do the testes produce?

A

Testosterone

62
Q

What does testosterone do? [2]

A

Controls puberty and sperm production

63
Q

What do the ovaries produce?

A

Oestrogen

64
Q

What does oestrogen do? [2]

A

Controls puberty and menstrual cycle

65
Q

3 characterists of the nervous system

A
  1. Fast action
  2. Short-lasting
  3. Precise
66
Q

3 characteristics of endocrine system

A
  1. Slower action
  2. Long-lasting
  3. General
67
Q

Describe what happens when blood glucose levels are too high [5]

A
  1. Blood has too much glucose
  2. Pancreas secretes the hormone insulin
  3. Causes glucose to move from the blood into liver and muscle cells
  4. This glucose is then converted into glycogen for storage
  5. Blood glucose levels reduced
68
Q

Describe what happens when blood glucose levels are too low [5]

A
  1. Blood has too little glucose
  2. Pancreas secretes the hormone glucagon
  3. Causes glycogen in cells to be converted into glucose
  4. Glucose released into blood
  5. Blood glucose levels increased
69
Q

Effect of too little blood glucose

A

Won’t be enough glucose for tissue cells to respire

70
Q

Effect of too much blood glucose

A

Damages tissues

71
Q

What is type 1 diabetes?

A

The pancreas produces little or no insulin

72
Q

How is type 1 diabetes treated?

A

Insulin injections

73
Q

What precautions should people with type 1 diabetes take and why? [2]

A
  1. Limiting sugar-rich foods (which causes blood glucose levels to rise)
  2. Regular exercise (helps to remove excess glucose from the body)
74
Q

What is type 2 diabetes?

A

Body cells no longer respond to insulin produed by the pancreas

75
Q

How is type 2 diabetes regulated? [2]

A
  1. Healthy diet
  2. Regular exercise
76
Q

What are the 2 jobs of the kidneys?

A
  1. Remove waste products
  2. Regulate levels of useful things
77
Q

Filtration, selective reabsorption

Explain how the kidneys remove waste and regulate useful substances [5]

A
  1. Kidneys how around 1 million structures called nephrons
  2. As blood passes through, the tubules absorb anything small
  3. This is known as filtration
  4. The blood then reabsorbs the useful things from the tubules
  5. This is known as selective reabsorption
78
Q

Proteins, amino acids, ammonia

What is urea? [3]

A
  1. The digestion of proteins from our diet results in excess amino acids
  2. In the liver, these amino acids are deaminated to form ammonia
  3. Ammonia is toxic so is converted into urea for safe excretion
79
Q

How are ions and water lost in the body? [2]

A

Sweat and during exhalation

80
Q

Why must water levels be regulated?

A

Our cells can be damaged (swell and pop or shrink)

81
Q

ADH

What hormone controls the concentration of urine?

A

ADH

82
Q

Where is ADH released from?

A

Pituitary gland

83
Q

Describe what happens when water levels are too low? [6]

A
  1. Water levels are too low
  2. A signal is sent to the pituitary gland
  3. Pituitary gland releases ADH into the bloodstream
  4. ADH reaches kidneys and tells the tubules to reabsorb more water back into the blood
  5. Amount of water in bloodstream increases
  6. We produce less urine
84
Q

Describe what happens when water levels are too high? [6]

A
  1. Water levels are too high
  2. Signals stop sending to the pituitary gland
  3. Less ADH released
  4. Less ADH reaches kidneys
  5. Tubules reabsorb less water into bloodstream
  6. We produce more urine
85
Q

What are the consequences of kidney failure? [2]

A
  1. Waste substances build-up in blood stream
  2. Unable to regulate water and ion levels
86
Q

Write on paper and check!!!

Describe how dialysis works [7]

A
  1. Person’s blood supply connected to dialysis machine
  2. The person’s blood can pass into the machine, through the circuit and back out again
  3. Whilst in the machine, the person’s blood comes into contact with dialysis fluid, separated by a partially permebale membrane
  4. Only things like ions and water can diffuse across, not cells and proteins
  5. Dialysis fluid is a mixture with the same concentration of water and other molecules as healthy blood
  6. This means that only waste substances (such as urea) and excess ions and water diffuse across. This is because there is a concentration gradient
  7. The patient’s blood levels are back to normal
87
Q

Problems with dialysis [5]

A
  1. Time-consuming - 3-4 times a week for 3-4 hours each time
  2. Can cause blood clots and infections
  3. Unpleasant experience
  4. Expensive
  5. People will have to have it for the rest of their life
88
Q

Problems with kidney transplant [2]

A
  1. Rejection
  2. Not enough organs available
89
Q

Describe the 4 stages of the menstrual cycle

A
  1. Menstruation starts - uterus lining breaks down for about 4 days
  2. Uterus lining builds up again, from day 4 to 14, ready to receive a fertilised egg
  3. Ovulation - an egg develops and is released from the ovary on day 14
  4. Wall is maintained until day 28 - if no fertilised egg lands on the uterus wall, the lining breaks down and cycle starts again
90
Q

Describe how the 4 hormones control the menstrual cycle [5]

A
  1. FSH stimulates an egg to mature and stimulates the ovaries to produce oestrogen
  2. Oestrogen causes the lining of the uterus to grow, inhibits FSH and stimulates LH
  3. LH stimulates the release of an egg on day 14
  4. Progesterone maintains the lining of the uterus and inhibits LH and FSH
  5. Oestrogen also maintains the uterus lining
91
Q

What hormones can be given to women to increase fertility?

A

FSH and LH

92
Q

Cons of increasing fertility with hormones [2]

A
  1. Doesn’t always work
  2. Too many eggs can be stimulated - multiple births
93
Q

Describe how IVF works [4]

A
  1. A woman is given FSH and LH to stimulate egg maturation
  2. Eggs are collected and fertilised by sperm from a man in a lab
  3. The fertilised egg develops into embryos
  4. One or two of the embryos are inserted into the woman’s womb
94
Q

Cons of IVF [3]

A
  1. Low success rates
  2. Emotionally and physically stressful
  3. Lead to multiple births - higher chance of complications
95
Q

How have developments in microscopy helped IVF?

A

Single cells can be removed from the embryo for genetic testing - to see if healthy

96
Q

What are the ethical issues regarding IVF? [2]

A
  1. Unused embryos destroyed - destroying potential life
  2. Genetic testing could lead to designer babies
97
Q

What does adrenaline increase? [4]

A
  1. Heart rate
  2. Blood pressure
  3. Blood supply to muscles
  4. Blood sugar levels
98
Q

What happens when thyroxine levels are too high? [3]

A
  1. Thyroxine will inhibit the pituitary gland from producing TSH
  2. Less TSH means the thyroid gland won’t produce as much thyroxine
  3. Thyroxine levels go back to normal
99
Q

What happens when thyroxine levels are too low? [3]

A
  1. Pituitary gland will release TSH
  2. This stimulates the thyroid gland to release thyroxine
  3. Thyroxine levels increase to normal
100
Q

Phototropism, geotropism

What is an auxin?

A

A plant hormone which controls growth in the tips of shoots and roots, in response to phototropism and geotropism

101
Q

What do auxins do in the shoots?

A

Promote growth

102
Q

What do auxins do in the roots?

A

Inhibit growth

103
Q

THINK: auxins

Explain how a shoot grows towards light [3]

A
  1. When a shoot tip is exposed to light, more auxin accumulates on the side in the shade
  2. This makes the cells grow faster on the shaded side
  3. So the shoot bends towards the light
104
Q

THINK: auxins

Explain how shoots grow away from gravity [3]

A
  1. When a shoot is growing sideways, gravity causes more auxin to accumulate on the lower side
  2. This causes the lower side to grow faster
  3. So the shoot bends upwards
105
Q

THINK: auxins

Explain how roots grow towards gravity [3]

A
  1. When a root grows sideways, it will have more auxin on its lower side
  2. However, in the root, it inhibits growth
  3. This means that the cells on the top grow faster and the root bends downwards
106
Q

What are auxins used for? [3]

A
  1. Killing weeds
  2. Rooting powders
  3. Growing cells in tissue culture
107
Q

What is Gibberellin used for? [3]

A
  1. Controlling dormancy
  2. Inducing flowering
  3. Growing larger fruit
108
Q

What is ethene used for?

A

Control the ripening of fruit

Biology (7 decks)

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