B5 Flashcards
(93 cards)
1
Q
What is homeostasis?
A
The regulation of conditions inside the body to maintain a stable internal environment in response to changes in both internal and external conditions
2
Q
What things do automatic control systems regulate? (3)
A
Body temperature and blood glucose level and water content
3
Q
What are the three main components that work together in automatic control systems? (3)
A
Receptors, coordination centres (brain and spine and pancreas) and effectors
4
Q
What does negative feedback do?
A
When the level of something in the body is too high or low, the body uses negative feedback to bring it back to normal
5
Q
How does negative feedback work? (4)
A
- Receptor detects a stimulus - level is too high or low. 2. Coordination centre receives and processes the information, then organises a response. 3. Effector produces a response and restores the optimum level. 4. The effectors will continue to produce this response for as long as they are being stimulated by a coordination centre. This sometimes leads to the opposite problem occuring, in which case the negative feedback process starts again.
6
Q
What makes up the nervous system?
A
The central nervous system (CNS) and sensory neurones and motor neurones and effectors
7
Q
What is the central nervous system?
A
The brain and the spinal chord, connected to the body by sensory neurones and motor neurones
8
Q
What are sensory neurones?
A
The neurones that carry information as electrical impulses from the receptors to the CNS
9
Q
What are motor neurones?
A
The neurones that carry electrical impulses from the CNS to effectors
10
Q
What are effectors?
A
Muscles and glands which respond to nervous impulses. Muscles could contract and hormones could be released.
11
Q
What are synapses and what do they do?
A
They are the connections between two neurones. The nerve signal is transferred by chemicals (neurotransmitters) which diffuse across the gap and set off a new electrical signal in the next neurone
12
Q
What are reflexes?
A
Rapid, automatic responses to stimuli that don’t involve the conscious part of the brain
13
Q
How does a reflex arc work? (4)
A
- Stimulus is detected by receptors, causing impulses to be sent along a sensory neurone to a relay neurone in the CNS. 2. Impulses reach a synapse between sensory neurone and relay neurone, causing neurotransmitters to be released, which diffuse across the gap and cause an impulse to be sent down the relay neurone. 3. The same thing happens when the impulses reach a synapse between the relay neurone and the motor neurone. 4. The impulses travel down the motor neurone to the effector, which produces a response.
14
Q
How would you investigate reaction times?
A
Ruler drop test or computer test
15
Q
Required practical 7 - reaction times. (5)
A
- Person A holds their thumb and finger at the bottom of the ruler. 2. Person B drops it randomly. 3. Repeat 10 times. 4. Repeat with different independent variable e.g. caffeine noise. 5. Draw a table and compare.
16
Q
What is the brain made up of?
A
Millions of neurones.
17
Q
What is the cerebral cortex?
A
The outer layer of the brain which is responsible for consciousness; intelligence; memory and language
18
Q
What is the medulla?
A
It controls unconscious activities such as breathing and is at the point where the spinal cord meets the brain
19
Q
What is the cerebellum?
A
At the back of the brain, it is responsible for muscle coordination
20
Q
How do scientists study the brain?
A
Studying patients with brain damage, electrically stimulating the brain and MRI scans
21
Q
How has research into the brain helped people?
A
Developed treatment of disorders of the nervous system. For example, electrical stimulation can reduce muscle tremors caused by Parkinson’s
22
Q
What are the risks of researching the brain?
A
Physical damage to the brain or increased problems with brain function
23
Q
What are the different parts of the eye? (7)
A
- Sclera - tough supporting wall of the eye. 2. Cornea - transparent outer layer at the front of the eye which refracts light into the eye. 3. Iris - muscles that control the diameter of the pupil and therefore how much light enters the eye. 4. Lens - focuses light onto the retina. 5. Retina - contains receptor cells sensitive to light intensity and colour. 6. Ciliary muscles and suspensory ligaments - control shape of the lens. 7. Optic nerve - carries impulses from the receptors on the retina to the brain.
24
Q
What is accommodation?
A
The process by which the eye’s lens changes shape to focus near or far objects on the retina
25
How does the eye respond to light intensity?
In bright light - reflex is triggered that causes the circular muscles in the iris to contract and the radial muscles to relax, making the pupil smaller. Opposite in less light.
26
How does the eye focus on near objects?
The ciliary muscles contract which slackens the suspensory ligaments making the lens fatter and more curved - increasing the amount by which it refracts light.
27
How does the eye focus on distant objects?
The ciliary muscles relax allowing the suspensory ligaments to pull tight making the lens thinner and less curved - decreasing the amount by which it refracts light.
28
What is hyperopia?
Long-sightedness
29
What causes hyperopia and how can it be corrected?
It occurs when the eyeball is too short or the lens doesn't refract light enough causing images of near objects to focus behind the retina. It can be corrected by glasses with convex lenses to refract the light more so that images form behind the retina
30
What is myopia?
Short-sightedness
31
What causes myopia and how can it be corrected?
It occurs when the lens is the wrong shape so that it refracts light too much or when the eyeball is too long, which causes the images of distant objects to be focused in front of the retina. It can be corrected by glasses with concave lenses
32
How can vision defects be treated?
Glasses. Contact lenses. Laser eye surgery. Replacement lens surgery
33
What are contact lenses?
Thin lenses that sit on the surface of the eye and are shaped to compensate for the fault in focusing. They are lightweight and almost invisible. They are more convenient than glasses for sports. There are hard lenses and soft lenses - soft lenses are more comfortable but carry a higher risk of eye infections than hard lenses.
34
What is laser eye surgery?
A laser vaporises tissue; changing the shape of the cornea and how strongly it refracts light into the eye. It can treat both long-sightedness and short-sightedness. Like all surgical procedures; there are risks of complications; such as infection or the eye reaction in a way that makes vision worse.
35
What is replacement lens surgery?
Removing the natural lens and replacing it with an artificial plastic lens. It involves work inside the eye so has more risks that laser eye surgery including possible damage to the retina (which could lead to sight loss).
36
How does the body detect extreme temperature and react to it?
Temperature receptors in the skin and in the thermoregulatory centre detect that the core body temperature is too high or low. The thermoregulatory centre acts as a coordination centre - it receives information from temperature receptors and triggers effectors automatically. Effectors produce a response to counteract the change.
37
What do effectors do in response to the core body temperature being too high?
Sweat is produced by sweat glands and evaporates from the skin - transferring thermal energy to the environment. Vasodilation - blood vessels supplying the skin dilate so more blood flows close to the surface of the skin, transferring thermal energy from the skin to the environment.
38
What do effectors do in response to the core body temperature being too low?
Hairs stand up to trap an insulating layer of air. No sweat is produced. Vasoconstriction - blood vessels supplying the skin capillaries constrict to close of the blood supply to the skin - meaning less thermal energy is lost from the skin into the environment. Shivering (automatic muscle contractions) needs respiration which transfers some energy to warm the body
39
What are hormones?
Chemical messengers sent in the blood to target organs to affect and control them. They control things in organs and cells that need constant adjustment. They have relatively long-lasting effects but are slower.
40
What makes up the endocrine system?
The pituitary gland. The thyroid. The adrenal gland. The pancreas. The ovaries in females and the testes in males.
41
What does the pituitary gland do?
It produces many hormones that regulate body conditions. Called "the master gland" because the hormones it produces act on other glands, directing them to release hormones that bring about change. In the brain.
42
What does the thyroid do?
Produces thyroxine which is involved in regulating things like the rate of metabolism heart rate and temperature. In the neck.
43
What does the adrenal gland do?
Produces adrenaline which is used to prepare the body for a "fight or flight" response. In the top of each kidney.
44
What does the pancreas do?
Produces insulin which is used to lower blood glucose level.
45
What do the ovaries do?
Produces oestrogen which is involved in the menstrual cycle
46
What do the testes do?
Produce testosterone which controls puberty and sperm production
47
What is the difference between a hormonal and a nervous response?
Hormones act more slowly and for a long time in a general way. Nerves act very quickly for a short time on a precise area
48
What happens when blood glucose level is too high?
Blood has too much glucose - insulin is secreted by the pancreas and glucose moves from the blood into the liver and muscle cells. Insulin causes the liver to turn glucose into glycogen so blood glucose is reduced.
49
What happens when blood glucose level is too low?
Blood has too little glucose - glucagon is secreted by the pancreas - glucagon causes liver to turn glycogen into glucose. Liver releases glucose into blood - blood glucose is increased
50
What is type 1 diabetes?
When the pancreas produces little or no insulin, meaning the person's blood glucose level can rise to a level that can kill them. People with type 1 diabetes need insulin therapy - which is several injections of insulin throughout the day - to make sure glucose is removed from the blood quickly once the food has been digested. They also need to limit their intake of food which is rich in simple carbohydrates and get regular exercise. You are born with the condition.
51
What is type 2 diabetes?
Where a person becomes resistant to their own insulin. This causes blood sugar levels to rise to a dangerous level. Being overweight can increase your chance of getting type 2 as obesity is a major risk factor in the development of the disease. It can be controlled by eating a carbohydrate-controlled diet and getting regular exercise. You develop this type over time by poor life choices
52
What do the kidneys do?
They make urine by taking waste products out of the blood. Substances are filtered out of the blood as it passes through the kidneys (filtration). Useful substances like glucose, ions and water are then absorbed back into the blood (selective reabsorption).
53
What is urea?
Ammonia is produced as a waste product of deanimation (excess amino acids being converted into fats and carbohydrates in the liver). It is toxic so is converted into urea in the liver. It is then transported to the kidneys, where it is filtered out of the blood and excreted from the body in urine
54
Why are ions in urine?
If the ion content of the body is wrong, this could upset the balance between ions and water - meaning too much or too little water is drawn into the cells by osmosis - which can damage cells and mean they don't work as well as normal. The kidneys determine how much ions are reabsorbed into the blood after filtration and what amount is removed from the body in the urine
55
Why is water in the urine?
The body needs to balance the amount of water coming into the body against water coming out. We lose water from the skin in sweat and from the lungs when breathing out. 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 urine
56
How is concentration of urine changed to control water content in the body?
A receptor in the brain detects that the water content is too high or low. The coordination centre in the brain receives the information and coordinates a response. The pituitary gland releases more or less ADH so more or less water is reabsorbed from the kidney tubules
57
What does ADH do?
Controls the concentration of the urine. The more ADH there is, the more water is reabsorbed. Controlled by negative feedback.
58
What is kidney failure and how can it be treated?
It is where the kidneys don't work properly and you lose the ability to control the level of ions and water in your body. This eventually results in death. It can be treated by dialysis or a kidney transplant.
59
What is dialysis?
Treatment by dialysis restores the concentrations of dissolved substances in the blood to normal levels and has to be carrried out on patients at regular intervals
60
What are kidney transplants?
It is the only cure for kidney failure. A healthy kidney is taken from a live doner or someone who has died. There is a risk that the donor kidney could be rejected by the immune system. It is cheaper than dialysis and stops the inconvenience of dialysis - but there are long waiting lists for kidneys
61
What happens during puberty?
The body starts releasing sex hormones that trigger secondary sexual characteristics and cause eggs to mature in women. In men; the main sex hormone is testosterone which is produced by the testes and stimulates sperm production. In women; the main sex hormone is oestrogen which is produced in the ovaries.
62
What are the stages of the menstrual cycle?
Day 1 - Menstruation starts. The uterus lining breaks down for about four days. Day 4 to Day 14 - the uterus lining builds up again into a thick spongy layer full of blood vessels ready to receive a fertilised egg. Day 14 - An egg develops and is released from the ovary (ovulation). Day 14 to Day 28 - The wall is maintained and if no fertilised egg has landed on the uterus wall by Day 28, the spongy lining breaks down and the cycle starts again.
63
What do hormones do in the mentrual cycle? (4)
1. FSH is produced by the pituitary gland and causes an egg to mature in one of the ovaries; in a follicle. It stimulates the ovaries to produce oestrogen. 2. Oestrogen causes the lining of the uterus to grow and stimulates the release of LH and inhibits the release of FSH. 3. LH is produced by the pituitary gland and stimulates the release of an egg. 4. Progesterone is produced in the ovaries. It maintains the lining of the uterus during the second half of the cycle; so when the level of it falls; the lining breaks down. It inhibits the release of LH and FSH.
64
What hormones are used to reduce fertility (contraception)?
Oestrogen - if taken every day inhibits the production of FSH and after a while egg development and production stop and stay stopped. Progesterone stimulates the production of thick mucus which prevents and sperm getting through and reaching an egg. Inhibits FSH and LH - stopping egg maturation and release
65
How do barriers reduce fertility (contraception)?
1. Condoms and female condoms prevent sperm entering the vagina - prevent against sexually transmitted diseases. 2. Diaphragm is a shallow plastic cup that fits over the cervix to form a barrier. It has to be used with spermicide. Spermicide can be used alone as a form of contraception but is only 70-80% effective.
66
Which hormones are in a contraceptive patch?
Contraceptive patch contains oestrogen and progesterone and is stuck under the skin. Each one lasts one week
67
What other ways are there of preventing pregnancy?
Sterilisation - Cutting or tying the fallopian tubes in a female or the sperm duct in a male. This is permanent; however there is a very small chance that the tubes can rejoin. 'Natural' methods - Not having sex when the woman is most fertile. Popular with those who who think that hormonal or barrier contraceptives are unnatural; it is not very effective. Abstinence - Not having intercourse
68
How can hormones be used to increase fertility?
FSH and LH can be given to women in a fertility drug to stimulate ovulation. However; it doesn't always work and can be quite expensive, and too many eggs could be stimulated; resulting unexpected multiple pregnancies
69
How does IVF work?
The mother is given FSH to mature eggs in her ovaries. The mature eggs are then removed and fertilised in a petri dish. Once the embryo(s) are large enough they can be implanted back into the mother.
70
What are the disadvantages of IVF? (4)
Multiple births can happen if more than one embryo grows which is risky for mothers and babies as there is a higher chance of miscarriage or stillbirth. Low success rate - making the process stressful and upsetting. Physically stressful for the woman. Reactions to the hormones can include abdominal pain; vomiting; dehydration
71
Why are some people against IVF?
It often results in unused embryos that are eventually destroyed - unethical because each embryo is a human being. Genetic testing of embryos before implantation raises ethical issues - could lead to the selection of preferred characteristics e.g. gender
72
What does adrenaline do?
It gets the body ready for "fight or flight" by triggering mechanisms that increase the supply of oxygen and glucose to cells in the brain and muscles. For example; it increases heart rate
73
What does thyroxine do?
It regulates the basal metabolic rate - which is the speed at which chemical reactions in the body occur while the body is at rest. It is also responsible for stimulating protein synthesis for growth and development.
74
What is auxin?
A plant hormone that controls growth near the tips of shoots and roots in response to light (phototropism) and gravity (gravitropism/geotropism). It is produced in the tips and moves backwards to stimulate cell elongation which occurs in cells just behind the tips
75
How does phototropism work?
When a shoot tip is exposed to light; more auxin accumulates on the side that's in the shade; making the shoot grow faster on the shaded side and bend towards the light
76
How does gravitropism (or geotropism) work in a shoot?
When a shoot is growing sideways, gravity produces an unequal distribution of auxin in the tip; with more auxin on the lower side. This causes the shoot to bend upwards.
77
How does gravitropism (or geotropism) work in roots?
A root growing sideways will also have more auxin on its lower side. But in a root auxin inhibits growth; meaning cells at the top elongate faster and the root bends downwards.
78
What do gibberellins do?
Promote seed germination and growth of stems
79
What does ethene do?
Controls cell division and ripening of fruits during storage and transport.
80
Required practical 8 - investigate effect of light or gravity on newly germinated seedlings. (6)
1. Put cotton wool into three petri dishes and add the same volume of water to each dish. 2. Add ten seeds to each dish and place them in a warm place. 3. Allow the seeds to germinate and add more water if the cotton wool dries out. 4. One petri dish will sit in full light on a windowsill, the second will be in a dark cupboard, and the final dish will be placed in partial light. 5. Every day for one week measure the height of each seedling and record the results in a table. You must record the height of the individual seedlings on each day. 6. Calculate the mean of the seedlings each day and compare the mean heights in the three different locations.
81
How is auxin used commercially?
1. Killing weeds. 2. Rooting powder (for cloning). 3. Growing cells in tissue culture.
82
How are gibberellins used commercially?
1. Controlling dormancy - make seeds germinate at times of the year they wouldn't normally. It also helps to make sure that all seeds in a batch germinate at the same time. 2. Promote flowering - if these are treated with gibberellins, they will flower regardless. Gibberellin can also be used to grow bigger flowers. 3. Growing larger fruit.
83
How is ethene used commercially?
It is used to speed up the ripening of fruits by controlling cell division and stimulating enzymes that cause the fruit to ripen. This means that fruit can be picked when it is unripe and therefore less easily damaged, and made to ripen just as they go on sale.
84
Which hormones are in "the pill"?
"The pill" contains oestrogen and progesterone and is 99% effective at preventing pregnancy. It can cause side effects such as headaches and doesn't protect against STIs. There is a progesterone-only pill which has fewer side effects and is just as effective as the pill
85
Which hormones are in a contraceptive implant?
Contraceptive implant releases continuous progesterone. Can last 3 years.
86
Which hormones are in a contraceptive injection?
Contraceptive injection contains progesterone. Lasts 2 to 3 months
87
Which hormones are in an IUD?
Intrauterine device (IUD) is a T-shaped device that is inserted into the uterus to kill sperm and prevent egg implantation. There are plastic IUDs that release progesterone and copper ones that prevent sperm surviving
88
What is the first step of blood filtration?
Filtration of glucose; urea; ions and water from the blood
89
What is the second step of blood filtration?
Selective reabsorption of ALL glucose; some ions and some water into the blood.
90
What is the third step of blood filtration?
Excretion of ALL urea; excess ions and excess water into the urine
91
What are two disadvantages of kidney transplants?
Must take immune-suppressant drugs which increase the risk of infection and a shortage of organ doners
92
What are two advantages of kidney transplants?
Patients can lead a more normal life without having to watch what they eat and drink and it's cheaper for the NHS
93
What are two disadvantages to kidney dialysis?
Patient must limit their salt and protein intake between dialysis sessions and it is expensive for the NHS
