Homeostasis Flashcards
(75 cards)
1
Q
What is homeostasis?
A
The regulation of conditions inside the body to maintain a stable internal environment so the body can respond to conditions.
2
Q
Explain negative feedback. (4 steps)
A
- Receptor detects a stimuli is too high/ low
- The coordination centre organizes a response to raise/ lower it
- Effector produces a response which counteracts the stimuli
- The response carries on until the level changes too much and the opposite problem occurs, meaning the negative feedback reverses
3
Q
Name 2 types of effector
A
- Muscles
- Glands
4
Q
How do synapses work? (3 steps)
A
- The electrical nerve signal transforms into a chemical message in the pre-synaptic neurone
- Neurotransmitters diffuse across the synaptic cleft
- A new electrical signal is set off in the post-synaptic neurone
5
Q
What is a reflex action?
A
Automatic responses which don’t involve the conscious part of the brain
6
Q
State the 7 parts of a reflex action.
A
Stimuli, Receptor, Sensory neurone, Relay neurone in the CNS, Motor neurone, Effector, Response.
7
Q
- Where is the cerebral cortex?
- What does it do?
A
- Near the front at the top
- Consciousness, memory, language
8
Q
- Where is the medulla?
- What does it do?
A
- Near the spinal cord
- Unconscious activities
9
Q
- Where is the cerebellum
- What does it do?
A
- At the back
- Muscle co-ordination
10
Q
State 3 ways the brain can be studied.
A
- Studying patients with brain damage
- Electrically stimulating certain parts
- MRI scans
11
Q
State 2 risks of brain investigation.
A
- Physical damage to the brain
- Increased problems with its function
12
Q
What does the sclera do?
A
Acts as a tough, supportive outer wall
13
Q
What does the cornea do?
A
The thin outer layer of the eye which refracts light as it enters
14
Q
What does the iris do?
A
Controls the diameter of the pupil, controlling the amount of light that enters the eye
15
Q
What does the lens do?
A
Focuses light onto the retina
16
Q
What happens to eye in bright light?
A
- Circular muscles in the iris contract
- Radial muscles relax
- To contract the pupil
17
Q
What happens to the eye in dim light?
A
- Circular muscles in the iris relax
- Radial muscles contract
- To dialate the pupil.
18
Q
State how the eye responds to near objects.
A
- Ciliary muscles contract, suspensory ligaments relax
- Lens becomes more fat
- Light is refracted more
19
Q
State how the eye responds to far objects.
A
- Ciliary muscles relax, while suspensory ligaments contract
- The lens goes thin
- Light is refracted less
20
Q
How does myopia (short-sightedness) occur?
A
Light is refracted too much and and objects are brought into focus in front of the retina.
21
Q
How does hyperopia (long-sightedness) occur?
A
Light is not refracted enough and the object comes into focus behind the retina.
22
Q
How is myopia combatted?
A
Concave lens
23
Q
How is hyperopia combatted?
A
Convex lens
24
Q
State 3 other options for combatting eye problems other than glasses.
A
- Contact lenses
- Laser eye surgery
- Replacement lens surgery
25
How does the body detect and correct irregular body temperature? ( 3 steps)
1. Temperature receptors detect body temperature is too high/low
2. The thermoregulatory centre triggers effectors
3. Effectors establish appropriate responses
26
State 3 responses to the body being too cold.
1. Vascoconstriction causes blood vessels to constrict to redirect blood deeper to prevent excessive heat loss
2. Hair stands on end to trap an insulating layer of air
3. No sweating to reduce evaporation
27
State 3 responses to the body being too hot.
Vasodilation means blood vessels dilate to allow more blood to get close to the surface and dissipate heat to the surroundings
2. Hair lays flat to allow air to escape
3. Increased sweating increases evaporation
28
What hormone do the ovaries release?
Oestrogen
29
What hormone do testes produce?
Testosterone
30
What hormone does the thyroid release?
Thyroxine
31
What hormone does the adrenal gland produce?
Adrenaline
32
What hormone does the pancreas produce?
Insulin
33
State 3 difference between nerves and hormones.
1. Nerves are fast, hormones are slow
2. Nerves act for a short time, hormones a long time
3. Nerves act on a precise area, hormones are more general
34
# Not insulin
How is glucose removed from the blood?
Metabolism from cells and vigorous exercise
35
How and where is excess glucose stored?
As glycogen in the liver and muscles
36
When does insulin act and what does it do?
When blood glucose level is too high, insulin makes liver turn glucose into glycogen for storage
37
When does glucagon act and what does it do?
When blood glucose level is too low, glucagon makes liver turn glycogen back into glucose.
38
What does type 1 diabetes mean?
The pancreas produces little or no insulin, meaning blood glucose can rise too high
39
How is type 1 diabetes treated?
Insulin therapy
40
What does type 2 diabetes mean?
A person's body has become resistant to the insulin it creates.
41
What happens to proteins in the liver?
Excess amino acids which can't be stored are converted into fats and carbohydrates by the liver to be stored
42
What is urea?
Toxic ammonia which has been converted in the liver and sent to the kidneys to be filtered
43
What is ammonia?
A waste product from amino acids being converted into fats and carbohydrates
44
How do the kidneys regulate ion levels?
To keep the ion water balance steady, the right amount is reabsorbed back into the blood and the rest is excreted
45
How do kidneys regulate water levels?
Excrete excess water in urine
46
How is water lost? (2 ways)
1. Sweat
2. Exhaling
47
Why is the water to ion level important?
The wrong amount of water could be brought into the cells through osmosis, which could damage cells.
48
Which hormone regulates concentration of urine?
Anti-diuretic hormone
49
Explain dialysis treatment in 4 steps.
1. A person's blood flows through partially permeable membranes (permeable only to ions and waste substance) surrounded by dialysis fluid
2. The dialysis fluid has the same concentration of dissolved ions and glucose as healthy blood
3. This means useful dissolved ions and glucose won't be lost
4. Only waste substances like urea, excess ions and water diffuse across the barrier.
50
Give 2 problems with dialysis treatment.
1. Can lead to blood clots or infections
2. Expensive for the NHS to run
51
Give 2 problems with kidney transplants.
1. There is risk for the donor
2. The kidney could be rejected
52
Explain the 4 stages of the menstrual cycle.
1. Uterus lining breaks down for usually 4 days
2. The uterus builds up again to receive an egg from day 4-14
3. An egg is released from the ovary at day 14
4. The wall is maintained for 14 days until the cycle repeats
53
Explain how hormones control the menstrual cycle in 3 steps.
1. FSH is released by the pituitary which stimulates the ovaries to produce oestrogen
2. As oestrogen increases, FSH decreases and LH is produced by the pituitary
3. When LH reaches a peak, an egg is released
54
What does progesterone do? (2)
1. If a fertile egg is implanted, it inhibits FSH
2. Produces a thick mucus to prevent sperm reaching the uterus
55
What does FSH do?
Causes an egg to mature (prepare to be released)
56
What does oestrogen do?
Causes the lining of the uterus to build up
57
What does LH do?
Stimulates release of an egg
58
What hormones make up the combined oral contraceptive pill?
Oestrogen and progesterone
59
Give 3 hormonal methods of contraception
1. Contraceptive patch
2. Contraceptive implant
3. Contraceptive injection
60
Give 2 barrier contraceptives.
1. Condom
2. Diaphragm
61
Give 3 drastic ways to avoid pregnancy.
1. Sterilisation of reproductive organs
2. Avoiding sexual intercourse on fertile days of the cycle
3. Abstinence
62
Why can't some women get pregnant?
Their FSH levels are too low for an egg to mature
63
Cons of giving infertile women hormones? (2)
1. It doesn't always work leading to wasted money
2. Too many eggs could be stimulated
64
3 cons of IVF?
1. Multiple births could happen if more than one embryo develops
2. Success rate is low
3. Emotionally and physically stressful
65
2 ethical issues with IVF?
1. Unused embryos are destroyed
2. Child's characteristics could be chosen
66
Which hormone triggers thyroxide production?
Thyroid stimulating hormone
67
What is the name for a plant's growth in response for light?
Phototropism
68
What is the name for a plant's growth responding to gravity?
Geotropism
69
Describe the movement of auxin in a plant
Produced at the tips and moves backwards to stimulate elongation just behind the tips
70
Explain phototropism (2)
1. When a shoot is exposed to light, auxin gathers on the shaded side
2. This increases growth on that side causing the shoot to bend towards the light
71
Explain geotropism in a shoot (2)
1. When a root grows sideways, gravity causes more auxin to accumulate on the lower side
2. The lower side grows faster, bending the shoot upwards
72
Explain geotropism in a root.
1. A root growing sideways has more auxin on the lower side
2. The extra auxin inhibits growth on that side, causing the root to bend downwards
73
Give 3 ways auxins are useful.
1. Selective weedkillers targeting broad leaves
2. In rooting powder which can grow cuttings of plants
3. Tissue culture
74
Give 3 uses of gibberellin.
1. Alter a plants dormancy period so they germinate at certain times of the year
2. Inducing flowering in plants in harsh climates
3. Growing larger fruit
75
How is ethene used commercially?
Delaying or speeding up ripening of fruit.
