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GCSE BIOLOGY > P2- Homeostasis and response > Flashcards

P2- Homeostasis and response 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

Two examples of automatic control systems

A

Chemical (hormonal) and Nervous sytem

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3
Q

Examples of internal body conditions

A

Body temperature, blood sugar levels, blood pH, water concentration

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4
Q

What are the three main components of the automatic control system?

A

Receptor, effector and coordination centre

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5
Q

What is a receptor?

A

A cell that detects a stimulus

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6
Q

What is the coordination centre?

A

Receives and processes the information and organises a response

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7
Q

What is an effector?

A

The muscle (nervous) or gland (chemical) that produces a response to restore the optimum level by counteracting the change

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8
Q

What is a stimulus?

A

A change in environment

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9
Q

What are hormones?

A

Chemical messengers which are used in the body by the endocrine system, co-ordinate our organs and are produced by the glands.

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10
Q

What is the endocrine system?

A

Composed of glands which secrete hormones directly into the bloodstream

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11
Q

What is the blood’s role in the endocrine system?

A

Carry the hormones to a target organ where it produces an effect

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12
Q

Examples of what hormones control

A

Growth, sexual development, sugar levels, mood, metabolism

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13
Q

Which gland in the brain is the ‘Master Gland’?

A

Pituitary gland

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14
Q

What does the nervous system allow us to do?

A

The nervous system allows us to detect and react to changes in the environment. Humans can react to their surroundings and coordinate their behaviour

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15
Q

What are the 4 parts of the Nervous system?

A

Central nervous system (CNS), Sensory neurone, motor neurone and effector

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16
Q

What is the role of the Central Nervous (CNS)?

A

A coordination centre which receives information from the receptor and coordinates a response (which is carried out by the effector)

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17
Q

What is the Central Nervous system (CNS) made up of?

A

Brain and spinal cord only

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18
Q

What is the role of the sensory neurone?

A

Carry information as electrical impulses from the receptors to the CNS

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19
Q

What is the role of the motor neurone?

A

Carry information electrical impulses from the CNS to the effectors

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20
Q

What is a synapse?

A

The connection between two neurones where the impulses need to pass through

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21
Q

How does a synapse work?

A

1) When an electrical impulse reaches the end of an axon entering the synapse, the axon releases chemicals.
2) The chemicals diffuse across the gap.
3) These chemicals then set off a new electrical signal in the next neurone

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22
Q

What are reflexes?

A

Rapid, automatic responses to certain stimuli that don’t involve the conscious part of the brain

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23
Q

What is a benefit of having reflexes?

A

They can reduce the chances of injury

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24
Q

Give an example of one of your body’s reflexes that reduce injury

A

Your pupils automatically get smaller when bright light is shone on them to prevent the pupils getting damaged

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25
Q

What is the Reflex Arc?

A

The passage of information in a reflex

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26
Q

Stages of the Reflex Arc (full)

A

1) The stimulus (e.g a pin prick)
2) Pain receptors in the skin are stimulated
3) Nerve impulse travels along sensory neurone
4) Nerve impulse enters spinal cord
5) Nerve impulse passes across synapse into a relay neurone
6) Nerve impulse passes into motor neurone and travels along this, out of the spinal cord
7) When nerve impulse reaches finger, muscle (effector) contracts, pulling the finger away (response)

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27
Q

Stages of the reflex arc (words)

A

Stimulus- Receptor- Sensory neurone- Synapse- Relay neurone- Motor neurone- Effector- Response

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28
Q

What is reaction time?

A

The time it takes to respond to a stimulus

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29
Q

Examples that can affect reaction time?

A

Age, gender, drugs (e.g caffeine)

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30
Q

What is the role of the brain?

A

It controls complex behaviour, is part of the Control nervous system (CNS), made up of billions of interconnected neurones

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31
Q

Role of the cerebral cortex/cerebrum in the brain?

A

(Outer wrinkly bit) Responsible for conscious activity like memory, language/speech, thoughts, vision, intelligence

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32
Q

Where is the cerebral cortex/cerebrum located in the brain?

A

The top of your brain

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33
Q

Role of the cerebellum in the brain?

A

Resposible for muscle coordination and movement

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34
Q

Where is the cerebellum located in the brain?

A

Lower back of the brain

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35
Q

Role of the medulla (oblongata) in the brain?

A

Responsible for unconscious activity like your heart rate and breathing rate

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36
Q

Where is the medulla located in the brain?

A

Base/bottom part of the brain (connected to spinal cord)

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37
Q

Role of the hypothalamus?

A

To control the centre monitoring brain and helps maintain homeostasis

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38
Q

Where is the hypothalamus located?

A

In the brain

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39
Q

Role of the pituitary (master) gland?

A

Responsible for regulating many body functions and the activity of other glands

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40
Q

Where is the pituitary gland located?

A

In the brain

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41
Q

3 ways of treatment to study the brain

A

1) Studying patients with brain damage
2) Electrically stimulating different parts of the brain
3) Using MRI (magnetic resonance imaging) scanning techniques

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42
Q

What is the eye?

A

The eye is a sense organ containing receptors that are sensitive to light intensity and colour.

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43
Q

What is accommodation?

A

The process of changing the shape of the lens to focus on near or distant objects.

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44
Q

What is the retina in the eye?

A

A layer of cells at the back of the eye

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45
Q

Role of the retina in the eye

A

Contains receptors that are sensitive to light intensity and colour

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46
Q

Role of the sclera in the eye

A

The tough white outer layer of the eye which helps protect the eye from injury

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47
Q

Role of the cornea in the eye

A

The transparent outer layer at the front of the eye which refracts light (light bends as it enters the eye)

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48
Q

Role of the iris in the eye

A

Contain muscles which control the diameter/size of the pupil and therefore how much light enters the pupil

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49
Q

Role of the lens in the eye

A

Focuses the light onto the retina

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50
Q

Role of the ciliary muscles in the eye

A

Contracts or relaxes to move the suspensory ligaments

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51
Q

Role of the suspensory ligaments in the eye

A

Pulls the lens thin or allows the lens to widen

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52
Q

Role of the optic nerve in the eye

A

Carries impulses between the eye and the brain

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53
Q

What are the two types of muscles in the eye?

A

Circular muscles and radial muscles

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54
Q

Where are the circular and radial muscles found?

A

Iris

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55
Q

What happens to the eye in dim/low light?

A

1) Circular muscles in the iris relax
2) Radial muscles in the iris contract
3) Pupil dilates
4) More light enters the eye

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56
Q

What happens to the eye in bright light?

A

1) Circular muscles in the iris contract
2) Radial muscles in the iris relax
3) Pupil constricts
4) Less light enters the eye

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57
Q

What happens if a person’s lens cannot refract the light by the right amount?

A

They are either short or long sighted

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58
Q

Long sighted people are unable to focus on…

A

Near objects

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59
Q

What is the scientific name for long-sightedness?

A

Hyperopia

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60
Q

What happens in the lens of someone who is long-sighted (hyperopia)?

A

Their eyeball is too short/ lens cannot be thickened enough. The light rays aren’t refracted enough and the image of near focus objects are brought into focus behind the retina

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61
Q

How is being long-sighted (hyperopia) fixed?

A

Using convex lenses

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62
Q

How does the eye focus on near objects?

A

1) Ciliary muscles contract and have a smaller diameter
2) Suspensory ligaments loosen
3) Lens is then thicker, becomes more convergent which refracts light rays strongly onto the retina

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63
Q

Short sighted people are unable to focus on…

A

Distant objects

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64
Q

What is the scientific name for short-sightedness?

A

Myopia

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65
Q

What happens in the lens of someone who is short-sighted (myopia)?

A

Their eyeball is too wide/lens overthickens. The light rays refract too much and focus infront of the retina

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66
Q

How is being short-sighted (myopia) fixed?

A

Using concave lenses

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67
Q

How does the eye focus on distant objects?

A

1) Ciliary muscles relax and have a wider diameter
2) Suspensory ligaments pulled tight
3) Lens is then pulled thin, becomes more divergent which only slightly refracts light rays onto the retina

68
Q

4 treatments for people with vision defects

A

1) Spectacle lenses (Glasses/ convex or concave)
2) Contact lenses (hard or soft)
3) Laser eye surgery (change shape of cornea)
4) Replacement lens surgery (artificial lens inserted)

69
Q

What is a human’s optimum body temperature and why?

A

37 degrees as its the optimum temperature for enzymes to work in the body

70
Q

What is the thermoregulatory centre?

A

Acts as a coordination centre, contains receptors that are sensitive to the temperature of blood flowing through the brain, receive impulses from temperature receptors in the skin

71
Q

Where is the thermoregulatory centre located in the brain?

A

In the hypothalamus which is in the brain

72
Q

What happens if body temperature is too high?

A

1) Temperature receptors decect body is too hot
2) Thermoregulatory centre receives info from receptors and triggers effectors automatically
3) Effectors (e.g sweat glands) produce a response to counteract the change

73
Q

How do the effectors respond when you’re too hot?

A

1) Sweat produced by sweat glands and evaporates from skin which transfers energy to the surroundings
2) Vasolidation- Blood vessels supplying the skin dilate so more blood flows closer to surface of the skin

74
Q

How do the effectors respond when you’re too cold?

A

1) Hairs stand up to trap an insulating layer of air
2) No sweat produced
3) Vasoconstriction- Blood vessels supplying capillaries constrict to close off skin’s blood supply
4) Respiration is needed when you shiver which transfers some energy to warm the body

75
Q

6 examples of glands that make up the endocrine system

A

1) Pituitary (master) gland
2) Thyroid gland
3) Ovaries (females only)
4) Testes (males only)
5) Adrenal gland
6) The pancreas

76
Q

Role of the thyroid gland

A

Produces thyroxine which regulates things like metabolic rate, heart rate and temperature

77
Q

Role of the adrenal gland

A

Produces adrenaline, preparing the body for ‘fight or flight’

78
Q

Role of the ovaries

A

Produces oestrogen which is involved in the menstrual cycle

79
Q

Role of the testes

A

Produces testosterone which controls puberty and sperm production in males

80
Q

Role of the pancreas

A

Produces insulin which regulates the blood glucose level

81
Q

3 differences between nerves (N) and hormones (H)

A

1) N: Very fast action, H: Slower action
2) N: Act for short time, H: Act for long time
3) N: Act on precise area, H: Act in more general way

82
Q

What two hormones control blood glucose levels?

A

Insulin and glucagon

83
Q

How are blood glucose monitored and controlled?

A

By the pancreas, using insulin and glucagon, in a negative feedback cycle

84
Q

What is a negative feedback cycle?

A

The correction process to maintain optimum internal body conditions

85
Q

What happens if the blood glucose level is too high?

A

1) Insulin is secreted by the pancreas into the blood
2) Insulin + glucose move from blood into liver and muscles
3) Insulin makes liver turn glucose into glycogen
4) Blood glucose is reduced, levels back to normal

86
Q

What is the role of insulin?

A

Remove glucose from the blood

87
Q

What happens if blood glucose is too low?

A

1) Glucagon is secreted by the pancreas into the blood
2) Glucagon+glycogen move from blood to liver and muscles
3) Glucagon makes liver turn glycogen into glucose
4) Blood glucose is increased, levels back to normal

88
Q

What is the role of glucagon?

A

Increases your blood glucose level and prevents it from dropping too low

89
Q

What is diabetes?

A

A condition that affects YOUR ability to control YOUR blood glucose level.

90
Q

What is Type 1 Diabetes?

A

-Pancreas fails to produce sufficient insulin
-Uncontrolled high blood glucose levels
-Need several insulin injections throughout the day to make sure glucose is removed quickly once food has digested to stop the levels getting too high
-Amount of insulin injected depends on a person’s diet and activity
-Limit intake of food rich in simple carbohydrates (sugars)
-Regular excercise

91
Q

What is Type 2 Diabetes?

A

-Person becomes resistant to their own insulin
-Body cells no longer respond to the insulin produced by the pancreas
-Controlled by eating a carbohydrate-controlled diet and regular exercise
-Obesity is a major risk factor of type 2 diabetes

92
Q

What is the role of the kidneys?

A

They make urine by taking/filtering waste products out of your blood. This process is called filtration.

93
Q

What is selective reabsorption?

A

Useful substances like glucose, some ions and the right amount of water are absorbed back into the blood whilst the waste products are filtered out

94
Q

3 substances removed from the body in the urine

A

Urea
Ions
Water

95
Q

How and why is urea filtered out by the kidneys? (6 steps)

A

1) Proteins and amino acids can’t be stored in the body
2) Any excess amino acids are converted into fats and carbohydrates, which can be stored
3) This occurs in the liver and involves a process called ‘Deamination’
4) Ammonia is produced as a waste product from this process
5) Ammonia is toxic, converted to urea in the liver
6) Urea transported to kidneys where its filtered and excreted

96
Q

How and why are ions filtered out by the kidneys? (4 steps)

A

1) Ions like sodium are taken into body by food and then absorbed into the blood
2) If ion (or water) content of the body is wrong, it could upset the balance between ions and water meaning too much/little is drawn into cells by osmosis
3) Having the wrong amount of water can damage cells or mean they don’t work as well
4) The right amount of ions is reabsorbed into the blood after filtration and the rest is removed from the body in urine

97
Q

How and why is water filtered out by the kidneys?

A

1) Body has to constantly balance water coming in against water going out
2) We lose water from the skin in sweat and from the lungs when breathing out
3) We can’t control how much we lose in these ways, so the amount of water is balanced by the amount we consume and the amount removed by the kidneys in the urine

98
Q

What hormone controls the concentration of urine?

A

Anti-diuretic hormone (ADH)

99
Q

Where is ADH released from?

A

Pituitary gland

100
Q

What happens if a person’s water content/level is too high?

A

1) The receptor detects high water level
2) The coordination centre coordinates a response
3) Pituitary gland releases less ADH, so less water is reabsorbed from the kidney tubules

101
Q

What happens if a person’s water content/level is too low?

A

1) The receptor detects low water level
2) The coordination centre coordinates a response
3) Pituitary gland releases more ADH, so more water is reabsorbed from the kidney tubules

102
Q

2 treatments for a kidney failure

A

1) Dialysis treatment
2) Kidney transplant (the only cure)

103
Q

Why does dialysis have to be done regularly? (2)

A

1) To keep the concentrations of dissolved substances in the blood at normal levels
2) To remove waste substances

104
Q

How does a dialysis machine work? (3 steps)

A

1) The person’s blood flows between partially permeable membranes surrounded by dialysis fluid
2) Dialysis fluid has the same concentration of dissolved ions and glucose as healthy blood meaning they won’t be lost from the blood during dialysis
3) Only waste substances and excess ions and water diffuse across the barrier

105
Q

3 negatives of kidney dialysis

A

1) They happen 3 times a week for 3-4 hrs each
2) May cause blood clots or infections
3) It is expensive for the NHS to run

106
Q

1 positive of kidney dialysis

A

It can buy a patient valuable time until a donor organ is found

107
Q

2 risks of kidney transplants

A

1) It can be risky if the person donating one of their kidneys is still alive (infection, blood clots)
2) The donor kidney could be rejected by the person’s immune system

108
Q

Why are kidney transplants better than kidney dialysis?

A

They are cheaper in the long run

109
Q

What is the menstrual cycle?

A

The monthly hormonal cycle a female’s body goes through to prepare for pregnancy

110
Q

What is the main reproductive hormone for men?

A

Testosterone

111
Q

Where is testosterone produced?

A

Testes

112
Q

What does testosterone do?

A

Stimulates sperm production

113
Q

What is the main reproductive hormone for women?

A

Oestrogen

114
Q

What happens in Stage 1 of the menstrual cycle?

A

Day 1- menstruation starts where the uterus lining breaks down for about 4-6 days

115
Q

What happens in Stage 2 of the menstrual cycle?

A

The uterus lining builds up again (from day 4 to 14) into a thick spongy layer full of blood vessels, ready to receive a fertilised egg

116
Q

What happens in Stage 3 of the menstrual cycle?

A

Ovulation- An egg develops and is released from the ovary at day 14

117
Q

What happens in Stage 4 of the menstrual cycle?

A

The wall is then maintained from about day 14 to 28. If no fertilised egg has landed on the uterus wall by 28, the lining starts to break down and the cycle repeats

118
Q

What 4 hormones control the menstrual cycle?

A

1) FSH (Follicle-stimulating hormone)
2) Oestrogen
3) LH (Luteinising hormone)
4) Progesterone

119
Q

Which gland produces FSH?

A

Pituitary gland

120
Q

Where is the target of FSH?

A

Ovary

121
Q

What are the 2 actions of the target of FSH?

A

1) Causes an egg to mature
2) Starts releasing oestrogen

122
Q

Which gland produces oestrogen?

A

Ovary

123
Q

Where is the target of oestrogen?

A

Uterus

124
Q

What are the 2 actions of target of oestrogen?

A

1) Thickens the uterus lining
2) Tells pituitary to inhibit FSH and secrete LH instead

125
Q

Which gland produces LH?

A

Pituitary gland

126
Q

Where is the target of LH?

A

Ovary

127
Q

What are the 2 actions of target of LH?

A

1) Ovulation (Stimulates release of an egg)
2) Starts progesterone

128
Q

Which gland produces progesterone?

A

Ovary

129
Q

Where is the target of progesterone?

A

Uterus

130
Q

What are the 2 actions of target of progesterone?

A

1) Maintains uterus lining (during 2nd half of cycle)
2) When oestrogen and progesterone levels drop, period starts and also tells the pituitary to start releasing FSH again

131
Q

How can oestrogen actually prevent the release of an egg?

A

If oestrogen is taken daily to keep the level permanently high, it inhibits the production of FSH, and after a while, egg development production stop and stay stopped

132
Q

How can progesterone reduce fertility?

A

By stimulating the production of thick mucus which prevents any sperm getting through to reach an egg

133
Q

What is ‘The pill’?

A

An oral contraceptive containing oestrogen and progesterone

134
Q

2 negative of taking the pill?

A

1) Can cause headaches and nausea
2) Doesn’t protect against STD’s

135
Q

What is the contraceptive patch?

A

A small patch stuck to the skin containing oestrogen and progesterone. Each patch lasts a week

136
Q

What is the contraceptive implant?

A

An implant inserted under the skin. Releases a continuous amount of progesterone to stop the ovaries releasing the egg, harder for sperm to swim , and stops any fertilised egg implanting in the uterus. Can last 3 years.

137
Q

What is the contraceptive injection?

A

An injection containing progesterone lasting 2-3 months

138
Q

What is an Intrauterine device (IUD)?

A

A T-Shaped device inserted into the uterus to kill sperm and prevent implantation of a fertilised egg.

139
Q

What are the two main types of IUDs?

A

1) Plastic IUDs releasing progesterone
2) Copper IUDs preventing sperm surviving in uterus

140
Q

4 examples of non-hormonal methods of contraception?

A

1) Condoms
2) Diaphragms
3) Copper IUDs
4) Spermicides

141
Q

What is a diaphragm?

A

A shallow plastic cup that fits over the cervix to form a barrier. Has to be used with a spermicide.

142
Q

What is the only form of contraception that prevents STDs

A

Condoms

143
Q

What is sterilisation?

A

Cutting/tying fallopian tubes in a female, or the sperm duct in a male. This is a permanent procedure

144
Q

What are natural methods of avoiding pregnancy?

A

Avoiding sexual intercourse when the women is most fertile in her menstrual cycle. Not very effective.

145
Q

What is abstinence in avoiding pregnancy?

A

Not having intercourse

146
Q

Why can’t some women get pregnant?

A

Their FSH levels are too low to cause their eggs to mature meaning no egg is released

147
Q

What is the fertility drug?

A

A drug containing the hormones FSH and LH to stimulate ovulation

148
Q

What does IVF stand for?

A

In Vitro Fertilisation

149
Q

Explain the stages of IVF

A

1) Eggs collected from woman’s ovaries, fertilised in a lab with man’s sperm
2) Fertilised egg grown into embryos in lab incubator
3) Once embryos are tiny balls of cells, 1 or 2 are transferred to woman’s uterus
4) FSH and LH given before egg collection to stimulate several eggs to mature

150
Q

3 negatives of IVF

A

1) Multiple births (higher risk of miscarriage, stllbirth)
2) Success rate is low
3) Physically stressful (vomiting, dehydration)

151
Q

2 reasons why some are against IVF

A

1) Unused embryos are eventually destroyed
2) Genetic testing could lead to selecting preferred characteristics

152
Q

Why and how is adrenaline released?

A

In response to stressful or scary situations- your brain detects stress and sends nervous impulses to the adrenal glands which then secrete adrenaline

153
Q

What does adrenaline trigger?

A

‘Fight or flight’ mode, increases supply of oxygen and glucose to the brain and muscles

154
Q

Why is thyroxine released?

A

To regulate basal metabolic rate and stimulating proteinsynthesis for growth and development

155
Q

When the level of thyroxine in the blood is too high, what happens?

A

The secretion of the Thyroid Stimulating hormone (TSH) released from the pituitary gland is inhibited

156
Q

What is the role of plant hormones?

A

They make sure that plants grow in the right direction

157
Q

What is auxin?

A

A plant hormone that controls growth near the tips of the shoots and roots of a plant. It moves backwards to stimulate the cell elongation process which occurs in cells just behind the tips

158
Q

What does auxin control the growth of a plant in response to?

A

1) Light (phototropism)
2) Gravity (gravitropism/geotropism)

159
Q

What happens if the tip of a shoot in a plant is removed?

A

No auxin is available and the shoot may stop growing

160
Q

What happens when a shoot tip is exposed to light/grows towards light?

A

1) More auxin accumulates on the side that’s in the shade than the side in the light
2) This makes the cells grow/ elongate faster on the shaded side so the shoot bends towards the light

161
Q

What happens when a shoot grows away from gravity and roots grow towards gravity?

A

1) When a shoot grows sideways, gravity produces unequal distribution of auxin in the tip, with more auxin on the lower side
2) Causes lower side to grow faster, bending the shoot up
3) A root growing sideways will also have more auxin on its lower side
4) In a root, the extra auxin inhibits growth meaning cells on top elongate faster, so root bends downwards

162
Q

3 uses of auxin

A

1) Killing weeds
2) Growing from cuttings with rooting powder
3) Growing cells in tissue culture

163
Q

3 uses of Gibberellin

A

1) End seed dormancy
2) Promotes/induces flowering
3) Increases/ grows larger fruits

164
Q

2 uses of Ethene

A

1) Influences the growth of plants by controlling cell division
2) Controls/speeds up the ripening of fruits

165
Q

3 examples of plant growth hormones

A

1) Auxin
2) Gibberellin
3) Ethene

GCSE BIOLOGY (7 decks)

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