B5 : Seneca Flashcards
(97 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?
A
Body temperature, blood glucose level and water content
3
Q
What are the three main components that work together in automatic control systems?
A
Receptors, coordination centres 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?
A
Receptor detects a stimulus - level is too high or low. Coordination centre receives and processes the information, then organises a response. Effector produces a response and restores the optimum level.
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, sensory neurones, 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
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?
A
Stimulus is detected by receptors, causing impulses to be sent along a sensory neurone to a relay neurone in the CNS. 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. The same thing happens when the impulses reach a synapse between the relay neurone and the motor neurone. 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
What is the cerebral cortex?
A
The outer layer of the brain which is responsible for conciousness, intelligence, memory and language
16
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
17
Q
What is the cerebellum?
A
At the back of the brain, it is responsible for muscle coordination
18
Q
How do scientists study the brain?
A
Studying patients with brain damage, electrically stimulating the brain and MRI scans
19
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
20
Q
What are the risks of researching the brain?
A
Physical damage to the brain or increased problems with brain function
21
Q
What are the different parts of the eye?
A
Sclera - tough supporting wall of the eye;
Cornea - transparent outer layer at the front of the eye which refracts light into the eye;
Iris - muscles that control the diameter of the pupil and therefore how much light enters the eye;
Lens - focuses light onto the retina;
Retina - contains receptor cells sensitive to light intensity and colour;
Ciliary muscles and suspensory ligaments - control shape of the lens;
Optic nerve - carries impulses from the receptors on the retina to the brain
22
Q
How does the eye respond to light intensity?
A
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.
The opposite happens in low light
23
Q
How does the eye focus on near objects?
A
The ciliary muscles contract, which slackens the suspensory ligaments, making the lens fatter and more curved, increasing the amount by which it refracts light
24
Q
How does the eye focus on distant objects?
A
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
25
What is hyperopia?
Long-sightedness
26
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
27
What is myopia?
Short-sightedness
28
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
29
How can vision defects be treated?
Glasses, contact lenses, laser eye surgery, replacement lens surgery
30
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
31
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
32
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)
33
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
34
What is meant by effectors working antagonistically?
In some cases, one effector heats and another cools at the same time to achieve a very precise temperature. This mechanism allows a more sensitive response
35
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
36
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
37
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
38
What makes up the endocrine system?
The pituitary gland, the thyroid, the adrenal gland, the pancreas and the ovaries in females and the testes in males
39
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
40
What does the thyroid do?
Produces thyroxine, which is involved in regulating things like the rate of metabolism, heart rate and temperature
41
What does the adrenal gland do?
Produces adrenaline which is used to prepare the body for a "fight or flight" response
42
What does the pancreas do?
Produces insulin which is used to regulate the blood glucose level
43
What do the ovaries do?
Produces oestrogen, which is involved in the menstrual cycle
44
What do the testes do?
Produce testosterone, which controls puberty and sperm production
45
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
46
What happens when blood glucose level is too high?
Blood has too much glucose, insulin is secreted by the pancreas, glucose moves from the blood into the liver and muscle cells, insulin causes the liver to turn glucose into glycogen, blood glucose is reduced
47
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
48
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
49
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
50
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. This is called filtration. Useful substances like glucose, ions and water are then absorbed back into the blood. This is called selective reabsorption
51
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
52
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
53
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
54
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
55
What does ADH do?
Controls the concentration of the urine. The more ADH there is, the more water is reabsorbed.
56
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
57
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
58
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
59
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
60
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. This is 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
61
What do hormones do in the mentrual cycle?
Follicle stimulating hormone (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.
Oestrogen causes the lining of the uterus to grow and stimulates the release of luteinising hormone (LH) and inhibits the release of FSH.
LH is produced by the pituitary gland and stimulates the release of an egg.
Progesterone is produced in the ovaries by the remains of the follicle after ovulation. 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
62
What hormones are used to reduce fertility?
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
63
How do barriers reduce fertility?
They stop sperm reaching the egg.
Condoms and female condoms are worn during intercourse to prevent sperm entering the vagina. They are the only form of contraception that will prevent against sexually transmitted diseases.
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
64
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
65
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
66
What are the disadvantages of IVF?
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
67
How has IVF developed?
Advances in microscope techniques, developments of micro-tools and the development of time-lapse imaging in incubators have meant that IVF has become more successful
68
Why are some people against IVF?
It often results in unused embryos that are eventually destroyed - unethical because each embryo is a potential human being. Genetic testing of embryos before implantation raises ethical issues - could lead to the selection of preferred characteristics e.g. gender, eye colour, etc
69
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
70
What does thyroxine do?
It has an important role in regulating 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
71
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
72
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
73
How does gravitropism work?
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. 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
74
How can you investigate plant growth responses?
Grow cress seeds in petri dishes under a light
75
How is auxin used commercially?
Killing weeds - Selective weedkillers have been developed using auxins that disrupt growth patterns in broad-leaved plants, which most weeds are in contrast to most grasses and grains, and kills them.
Growing from cuttings with rooting powder - If you add auxins to cuttings of plants and plant them, they will rapidly produce roots and become a new plant. This enables clones to be produced very quickly.
Growing cells in tissue culture - Hormones such as auxins need to be added to a growth medium to stimulate plants cells in it to divide to produce a clone
76
How are gibberellins used commercially?
Controlling dormancy - Seeds can be treated with gibberellins to alter dormancy and 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.
Inducing flowering - There are some plants that require certain conditions to flower. If these are treated with gibberellins, they will flower regardless. Gibberellin can also be used to grow bigger flowers.
Growing larger fruit - Gibberellin can be used to make seedless varieties of fruit grow larger than they normally would
77
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.
Alternatively, chemicals can be added to fruits in storage that block ethene's ripening effect or reduce the amount of ethene that a fruit can produce. There are also some chemicals that react with ethene to remove it from the air
78
Which hormones are in a contraceptive patch?
Contraceptive patch contains oestrogen and progesterone and is stuck under the skin. Each one lasts one week
79
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
80
Which hormones are in a contraceptive implant?
Contraceptive implant releases continuous progesterone. Can last 3 years.
81
Which hormones are in a contraceptive injection?
Contraceptive injection contains progesterone. Lasts 2 to 3 months
82
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
83
What is the first step of IVF?
1) Collecting eggs from the woman's ovaries and fertilising them in a lab using the man's sperm, or it can be done by Intra-Cytoplasmic Sperm Injection, where the sperm is injected directly into the egg. This is useful when the man has a low sperm count
84
What is the second step of IVF?
2) The fertilised eggs are then grown into embryos in a laboratory incubator
85
What is the third step of IVF?
3) Once the embryos are matured enough, one or two of them are transferred to the woman's uterus. FSH and LH are given to the woman before egg collection to stimulate several eggs to mature
86
What is the first step of blood filtration?
Filtration of glucose, urea, ions and water from the blood
87
What is the second step of blood filtration?
Selective reabsorbtion of ALL glucose, some ions and some water into the blood
88
What is the third step of blood filtration?
Excretion of ALL urea, excess ions and excess water into the urine
89
What does isotonic mean?
Same concentration on both sides of membrane
90
Which ions are present in the body?
Sodium, potassium, calcium, nitrogen
91
What does hypotonic mean?
More dilute outside the membrane than the solution in the cell
92
What is cytoplasm largely made of?
Water
93
What does hypertonic mean?
More concentrated outside the membrane than the solution in the cell
94
What are deaminated amino acids called?
Ammonia
95
What is ammonia converted to?
Urea
96
What are two disadvantages of kidney transplants?
Must take immune-suppressant drugs which increase the risk of infection and a shortage of organ doners
97
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
