TOPIC 5 - HOMEOSTASIS AND RESPONSE Flashcards
(132 cards)
1
Q
What is homeostasis?
A
Maintaining a stable internal environment.
The conditions inside your body need to be kept steady , even when the external environment changes. This is really important because your cells need the right conditions in order to function properly, including the right conditions for enzyme action.
2
Q
What is homeostasis (simple)?
A
The regulation of the conditions inside your body (and cells) to maintain a stable internal environment, in response to changes in both internal and external conditions.
3
Q
Give examples of some automatic control systems.
A
Nervous and hormonal communication.
4
Q
What are the three components that your automatic control systems are made of?
A
Cells called receptors
Coordination centres (brain, spinal cord, pancreas)
Effectors
5
Q
What is negative feedback?
A
Negative feedback counteracts changes. When the levels of something gets too low or too high your body uses negative feedback to bring it back to normal.
6
Q
What happens when a receptor detects a stimulus - level is too high?
A
The coordination centre recieve and processes the information, then organising a response.
Effectors produces a response, which counteracts the change and restores to optimum level - the level decreases.
7
Q
How long will effectors continue to produce a response?
A
As long as they are stimulated by the coordination centre. This could cause the opposite problem - making a level change too much, away from the ideal.
However, the receptor detects if the level becomes too different and negative feedback starts again.
8
Q
What is the CNS (central nervous system)
A
In vertebrates this consists of the brain and the spinal cord only.
In mammals, the CNS is connected to the body by sensory neurones and motor neurones.
9
Q
What are sensory neurones?
A
The neurones that carry information as electrical impulses from the receptors to the CNS.
10
Q
What are motor neurones?
A
The neurones that carry electrical impulses from the CNS to effectors.
11
Q
What are effectors?
A
All your muscles and glands, which respond to nervous impulses. Egmuscles contract in response to a nervous impulse, whereas glands secrete organs. They respond to nervous impulses and bring about a change.
12
Q
What are receptors?
A
Receptors are cells that detect stimuli. There are many, eg taste receptors on the tongue and sound receptors in the ear. They can also form part of larger, complex organs eg the retina in the eye is covered in light receptor cells.
13
Q
What does the CNS do?
A
Coordinates the response. It receives information from the receptors and then coordinates a response. The response is carried out by receptors.
14
Q
What are synapses?
A
The connection between two neurones is called a synapse. The nerve signal is transferred by chemicals which diffuse (move) across the gap. These chemicals then set off a new electrical signal in the next neurone.
15
Q
Why are reflexes important?
A
They help to prevent injury.
16
Q
What are reflexes?
A
They are rapid, automatic response to certain stimuli that don’t involve the conscious part of the brain. The passage of information in a reflex (from receptor to effector) i called a reflex arc.
17
Q
Explain the reflex arc.
A
The neurone in reflex arcs go through the spinal cord, or through an unconscious part of the brain.
When a stimulus is detected by receptors, impulses are sent along a sensory neurone to a relay neurone in the CNS.
When impulses reach a synapse between the sensory neurone and the relay neurone, they trigger chemicals to be released. These chemicals cause impulses to be sent along the relay neurone.
When the impulse reach a synapse between the relay neurone and a motor neurone, the same thing happens. Chemicals are released and cause impulses to be sent along the motor neurone.
The impulses then travel along the motor neuone to the effector.
18
Q
What is the brain responsible for?
A
Complex behaviours.
19
Q
What is the cerebral cortex?
A
Outer wrinkly bit. It is responsible for things like consciousness, intelligence, memory and language.
20
Q
What is the medulla?
A
Controls unconscious activities such as breathing and your heart beat.
21
Q
What is the cerebellum?
A
Responsible for muscle coordination.
22
Q
How do neuroscientists study people with brain damage?
A
If a small part of the brain has been damaged, the effect this has on the patient can tell you a lot about what the damaged part of the brain does. Eg if the area at the back of the brain was damaged by a stroke and the patient went blind, you know that that area had something to do with vision.
23
Q
How can doctors electrically stimulate the brain?
A
The brain can be stimulated electrically by pushing a tiny electrode into the tissue and giving it a small zap of electricity. By observing what stimulating different parts of the brain does, it is possible to get an idea of what those parts do. Eg when a certain part of the brain (known as the motor area) is stimulated, it causes muscle contraction and movement.
24
Q
What is the sclera?
A
Tough supporting wall of the eye.
25
What is the cornea?
Transparent outer layer found at the front of they eye. It refracts light into the eye.
26
What is the iris?
Contains muscles that allow it to control the diameter of the pupil and therefore how much light enters the eye.
27
What is the lens?
Focuses the light onto the retina.
28
What is the retina?
Contains receptor cells sensitive to light intensity and colour.
29
How is the shape of the lens controlled?
Ciliary muscles and suspensory ligaments.
30
What is the optic nerve?
Carries impulses from the receptors on the retina to the brain.
31
How does the eye adjust for bright light?
When light receptors in the eye detect a very bright light, a reflex is triggered that makes the pupil smaller.
The circular muscles in the iris contract and the radial muscles relax.
32
How does the light adjust for dim light?
The radial muscles contract and the circular muscles relax. This makes the pupil wider.
33
What is accomodation?
The way that the eye focuses light on the retina by changing the shape of the lens.
34
How does the eye look at near objects?
The ciliary muscles contract, which slackens the suspensory ligaments. The lens becomes more curved. This increases the amount by which it refracts light.
35
How does the eye look at distant objects?
The ciliary muscles relax, which allows the suspensory ligaments to pull tight.
This makes the lens go less curved.
So it refracts light by a smaller amount.
36
What is the medical term for long-sightedness?
Hyperopia.
37
What does it mean if a person is long sighted?
They are unable to focus on near objects.
This occurs when the lens is the wrong shape so doesnt refract the light enough, or the eyeball is too short. The images of the near objects are brought into focus behind the retina.
38
What lens do people who are long sighted need to wear?
Convex lenses
| They are curved outwards so the light is refracted onto the lens.
39
What is the medical term for short-sightedness?
Myopia.
40
What does it mean if a person is short sighted?
They are unable to focus of distant objects.
This occurs when the lens is the wrong shape and refracts the light or the eyeball is too long.
The images of the distant objects are brought into focus in front of the retina.
41
What lens should a short sighted person wear?
You can use glasses with a concave lens.
| The lens curves inwards. This makes sure that the light rays focus on the retina.
42
What are three treatments for vision defects?
Contact lenses
Laser eye surgery
Replacement lens surgery
43
Why might a person want to wear contact lenses?
Lightweight and invisible.
| More convenient for activities such as sport.
44
What are the two types of contact lenses?
Hard and Soft
| People usually prefer soft as they are more comfortable, but they carry a higher risk of infection than hard lenses.
45
What is laser eye surgery?
A laser can be used to vaporise tissue, changing the shape of the cornea and so changing how strongly it refracts light into the eye. Changing the shape so that it is more powerful will improve long sight.
46
What is replacement lens surgery?
Sometimes long-sightedness may be more effectively treated by replacing the lens of the eye. The natural lens is removed and and an artificial lens, made of clear plastic, is inserted in its place. As it involves work inside of the eye, it carried a higher risk of infection than laser eye surgery. (including possible damage to the retina which could lead to loss of sight.
47
What is the thermoregulatory centre in the brain?
It contains receptors that are sensitive to the temperature of the blood flowing through the brain. It also receives impulses from temperature receptors in the skin, giving information about skin temperature.
48
What happens when the temperature receptors detect that core body temperature is too high?
The thermoreguatory centre acts as a coordination centre - it receives information from the temperature receptors and triggers the effectors automatically.
Effectors eg sweat glands produce a response and counteract the change.
49
What mechanism allows a more sensitive response to a change in body temperature?
Some effectors work antagonistiaclly eg one effector heats and another cools.
50
What do the effectors do when you are too hot?
Sweat
| and Dilate blood vessels
51
How does sweat help to cool you down?
It evaporates from the skin which transfers energy to the environment.
52
How does you blood vessels dilating help to cool you down?
More blood flows closer to the surface of the skin. This is called vasodilation. This helps to transfer energy from the skin to the environment.
53
What do the effectors do when you are too cold?
Hairs stand up
No sweat
Blood vessels constrict
Shiver
54
Why do your hair stand on end when you're cold?
To trap an insulating layer of air.
55
Why do your blood vessels constrict when you are cold?
Blood vessels supplying skin cappilaries constrict to close off the skin's blood supply. This is called vasoconstriction.
56
Why do you shiver when you are cold?
Your muscles contract automatically. This needs respiration which transfers some energy to warm the body.
57
What are hormones?
Chemical molecules released into the blood. They only affect particular cells in particular organs (called target organs).
58
Where are hormones produced?
They are produced and secreted by various glands, called endocrine glands. These glands make up your endocrine system.
59
What is the pituitary gland?
It produces many hormones that regulate body conditions. It is called the 'master' gland because these hormones act on other glands, directing them to release hormones and bring about change.
60
What is the thyroid?
This produces thyroxine, which is involved in regulating things like the rate of metabolism, heart rate and temperature.
61
What is the adrenal gland?
This produces adrenaline which is used to prepare the body for a 'fight or flight' response.
62
What is the pancreas?
This produces insulin, which is used to regulate the blood glucose level.
63
What are the ovaries?
Produce oestrogen, which is involved in the menstrual cycle.
64
What are the testes?
Produce testosterone, which controls puberty and sperm production.
65
How are nerves and hormones different?
Nerves:
Very fast
Act for a very short time
Act on a very precise area
Hormones:
Slower action
Act for a long time
Act in a more general way.
66
How is glucose normally removed from the blood?
Normal metabolism
| Vigorous exercise
67
How is excess glucose stored?
Stored as glycogen in the liver, and in the muscles.
68
How are glucose levels monitored and controlled?
The pancreas, using the hormone insulin and glucagon in a negative feedback cycle.
69
What happens when the blood glucose levels get too high?
Insulin is added
The insulin is secreted by the pancreas.
The glucose is moved from blood into liver and muscle cells.
So insulin removes glucose from the blood. It also makes the liver turn glucose into glycogen.
And the blood glucose level is reduced.
70
What happens when the blood glucose level is too low?
Glucagon is added
Glucagon is secreted by the pancreas
Glucose is released into blood by the liver.
Glucagon makes the liver turn glycogen into glucose.
Therefore, the blood glucose level is increased.
71
What is diabetes?
A condition that affects your ability to control your blood sugar level.
72
What is type 1 diabetes?
The pancreas produces little or no insulin. This means that a person blood glucose level can rise to a level that can kill them. People with type 1 diabetes need insulin therapy - this usually involves several injection of insulin throughout the day, most likely at meal times.
This makes sure that the glucose is removed from the blood quickly after the food has been digested, stopping the levels from getting too high.
These people also need to think about limiting the intake of food rich in simple carbohydrates and taking regular exercise to remove excess glucose from the blood.
73
What is type 2 diabetes?
When a person becomes resistant to their own insulin. They still produce insulin, but their body cells don't respond properly to the hormone. This ca cause a person's sugar level to rise to a dangerous level.
Being overweight can increase your chance of developing type 2 diabetes, as obesity is a major risk factor in the development of the disease. Type 2 can be controlled by eating a carbohydrate-controlled diet and getting regular exercise.
74
What are the kidneys?
The kidneys make urine by taking waste products (and other unwanted substances) out of your blood. Substances are filtered out of the blood as it passes through the kidneys. This process is called filtration.
75
What is selective reabsorption?
The kidneys then allow useful substances such as glucose, some ions and the right amount of water to be absorbed back into the blood.
76
What are the substances that are removed from the body in urine?
Urea
Ions
Water
77
What is urea?
Proteins and amino acids can't be stored by the body so any excess amino acids are converted into fats and carbohydrates, which can be stored. This occurs in the liver and involves a process called deamination.
Ammonia is produces as a waste product from this process.
Ammonia is toxic so it is converted into urea in the liver. Urea is then transprted to the kidneys, where it is filtered out of the blood and excreted from the body in urine.
78
Why might ions need to be excreted from the body?
If the ion, or water, content of the body is wrong, it could upset the balance between ions, and water meaning that to much or to little water is drawn into cells by osmosis.
Having the wrong amount of water can damage cells or mean they don't work as well as normal.
Some ions are lost in sweat, but this is not regulated so the right balance must be maintained by the kidneys.
79
Why is water excreted from the bodies?
The body has to constantly balance the water coming in against water going out.
We lose water from the skin in sweat and from the lungs when breathing out.
We cannot control how much we lose these ways, so the amount of water is balanced by the amount we consume and the amount removed by kidneys in urine.
80
What hormone controls the concentration of urine?
A hormone called anti-diuretic (ADH). This is released into the bloodstream by the pituitary gland.
81
What happens when a receptor in the brain detects that the water content of urine is too high?
The coordination centre in the brain receives the information and coordinates a response.
The pituitary gland releases less ADH, so less water is reabsorbed from the kidney tubules.
Water content decreases.
82
What happens if the kidneys do not work properly?
Waste substances build up in the blood and you lose your ability to control the levels of ions and water in your body. Eventually, this will result in death. People with failing kidneys can be kept alive by having dialysis treatment, or a kidney transplant.
83
What is a dialysis machine?
A machine does the job of the kidneys. It has to be done regularly to keep the concentrations of dissolved substances in the blood at normal levels, and to remove waste substances.
84
How does a dialysis machine works?
The person's blood flows between partially permeable membranes, surrounded by dialysis fluid. It is permeable to things like ions and waste substances, but not big molecules like proteins.
The dialysis fluid has the same concentration of dissolved ions and glucose as healthy blood. This means that useful dissolved ions and glucose will not be lost from the blood during dialysis.
Only waste substances such as urea and excessive ions and water diffuse across the barrier.
85
How often do patients need to undergo kidney dialysis?
3 times a week
| Each session takes 3-4 hours
86
What are the risks associated with kidney dialysis?
May cause blood clots or infections. Not a pleasent experience and is expensive for the NHS to run.
However, it will give valuable time until a donor organ is found.
87
What is the only cure for kidney failure?
Kidney transplant. Can be from a person who has died that was on the organ donor register, or from someone who is alive, as we all have two kidneys. However, there is a small risk to the person donating.
Although, the person's body may reject the kidney.
Transplants are cheaper than dialysis in the long term and can put an end to the hours patients have to spend on dialysis. But, there is a long waiting list for transplants.
88
What is the main reproductive hormone in men?
Testosterone. It is produced by the testes and stimulates sperm production.
89
What is the main reproductive hormone in women?
Oestrogen. It is produced in the ovaries. As well as bringing bout physical changes, it is also involved in the menstrual cycle.
90
What happens during stage one of the menstrual cycle?
Day 1 - menstruation starts. The uterus lining breaks down for about 4 days.
91
What happens during stage two of the menstrual cycle?
The uterus lining builds up again from day 4- 14, into a thick spongy layer full of blood vessels, ready to receive a fertilised egg.
92
What happens during stage three of the menstrual cycle?
An egg develops and is released from the ovary at day 14. This is called ovulation.
93
What happens during stage four of the menstrual cycle?
The wall is then maintained for about 14 days until day 28. If no fertilised egg has landed on the uterus wall by day 28, the spongy lining starts to break down and the whole cycle starts again.
94
What does oestrogen do in the menstrual cycle?
Produced in the ovaries. It causes the lining of the uterus to grow. It stimulates the release of LH (which causes the release of an egg) and inhibits FSH.
95
What does FSH do in the menstrual cycle?
Follicle stimulating hormone
Produced in the pituitary gland
Causes an egg to mature in one of the ovaries, in a structure called a follicle.
Stimulates the ovaries to produce oestrogen.
96
What does LH do in the menstrual cycle?
Luteinising Hormone
Produced by the pituitary gland
Stimulates the release of an egg at day 14 (ovulation).
97
What is progesterone?
Produced in the ovaries by the remains of the follicle after ovulation. Maintains the lining of the uterus during the second half of the cycle. When the level of progesterone falls, the lining breaks down. It inhibits the release of LH and FSH.
98
What is the combined oral contraceptive pill?
Contains oestrogen and progesterone.
99
How does an oestrogen only pill work?
If it is taken everyday to keep the level of it permanently high, it inhibits the production of FSH, and after a while egg development and production stop and stay stopped.
100
What is the contraceptive implant?
Inserted under the skin of the arm. It releases a continuous amount of progesterone, which stops the ovaries releasing eggs, makes it hard for sperm to swim (production of a thick mucus), and also stops any fertilised egg from implanting in the uterus. An implant can last for three years.
101
What is the contraceptive patch?
Contains oestrogen and progesterone. It is stuck to the skin and each patch lasts for one week.
102
What is the contraceptive injection?
It contains progesterone. Each dose lasts for 2-3 months.
103
What is an IUD?
Intrauterine device is a T shaped device that is inserted into the uterus to kill sperm and prevent implantation of a fertilised egg. There are two main types:
Plastic IUDs that release progesterone and copper IUDs that prevent sperm surviving in the uterus.
104
How can hormones be used to increase fertility?
Some women have levels of FSH that are too low to cause their eggs to mature.This means that no egg is released and the women cannot get pregnant.
The hormone FSH and LH can be given to women in a fertility drug to stimulate ovulation. What are the p
105
What are the pros of taking a fertility drug?
It helps lots of women to get pregnant when they previously couldn't.
106
What are the cons of taking a fertility drug?
It does not always work - some women may have to do it many times, which could make it expensive.
Too many eggs could be stimulated, resulting in unexpected multiple pregnancies.
107
What is IVF?
In vitro fertilisation
Involves collecting the eggs from a woman's ovaries and fertilising them in a lab using the man's sperm.
It can also involve a teachnique called Intra-cytoplasmic sperm injection.
The fertilised eggs are then grown into embryos in a laboratory incubator.
Once the embryos are tiny balls of cells, one or two of them are transferred to the woman'suterus to improve the chance of pregnancy.
FSH and LH are given before egg collection to stimulate several eggs to mature.
108
What is intra cytoplasmic sperm injection? (ICSI)
The sperm is injected directly into the egg. It is useful if the man has a very low sperm count.
109
What are the pros of IVF?
Fertility treatment can give an infertile couple a child.
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What are some cons of IVF?
Multiple births can happen if more than one embryo grows into a baby. So, there is a higher risk of miscarriage or still birth.
The success rate of IVF is low - the average success rate in the UK is about 26%. This makes the process incrdibly stressful and often upsetting, especially if there are multiple failures.
Emotionally and physically stressful for women. Some women have a strong reaction to the hormones eg abdominal pain, vomiting and dehydration.
111
Why are some people against IVF?
It often results in unused embryos that are eventually destroyed. Due to this, some people think it is unethical because each embryo is a potential human life.
The genetic testing before of embryos before implantation also raises ethical issues as some people think it could lead to the selection of preferred characteristics, such as gender or eye colour.
112
What does adrenaline do?
It is a hormone that is released by the adrenal glands, which are just above the kidneys.
Prepares you for flight or fight. It is released in response to stressful or scary situations - your brain detects fear or stress and sends nervous impulses to the adrenal glands, which respond by secreting adrenaline.
113
How does adrenaline get the body ready for 'fight or flight'?
It triggers mechanisms that increase the supply of oxygen and glucose to cells in the brain and muscles. For example, adrenaline increases heart rate.
114
What does thyroxine regulate?
Metabolism.
Also, it stimulates protein synthesis for growth and development.
It is released in response to thyroid stimulating hormone, which is released from the pituitary gland.
115
What is the basal metabolic rate?
The speed at which chemical reactions in the body occur while the body is at rest.
116
What is Auxin?
A plant growth hormone. It controls growth near the tip of shoots and roots. It is produced in the tips and moves backwards to stimulate cell elongation (enlargement process) which occurs in the cells just behind the tips..
117
What is phototropism?
When auxin controls the growth of a plant in response to light
118
What is gravitropism or geotropism?
Auxin controls the growth of a plant in response to gravity.
119
What happens if the tip of a shoot is removed?
No auxin is available so the plant might stop growing.
120
Which way to shoots grow in response to light?
Shoots grow towards the light. When a shoot tip is exposed to light, more auxin accumulates on the side that is in the shade than the side that is in the light.
This makes the cells grow (elongate) faster on the shaded side, so the shoot bends towards the light.
121
Which way do shoots grow in response to gravity?
Shoots grow away from gravity.
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 lower side to grow faster, bending the shoot upwards.
122
Which way do roots grow in regards to gravity?
Roots grow towards gravity.
A root growing sideways will also have more auxin on its lower side. But in a root extra auxin inhibits growth. This means that the cells on top will elongate faster, and the root bends downwards.
123
What are some of auxins uses?
Killing weeds
Growing from cuttings with rooting powder
Growing cells in the tissue culture
124
How are auxins used to kill weeds?
Selective week killers have been developed using auxins, which only affect the broad leaved plants. They totally disrupt their normal growth patterns, which soon kills them, whilst leaving the grass and crops untouched.
125
How can auxins be used for growing from cuttings with rooting powder?
Normally, if you stick cuttings in the soil they won't grow, but if you add rooting powder which contains auxins, they will produce roots rapidly and start growing as new plants. This enables growers to produce lots of clones of a really good plant very quickly.
126
How can auxins be used for growing cells in tissue culture?
Tissue culture can be used to grow clones of a plant from a few of ts cells. To do this, hormones such as auxins need to be added to a growth medium (along with nutrients) to stimulate the cells to divide to form both roots and shoots.
127
What is gibberellin?
Gibberellin is another type of plant growth hormone. It stimulates speed germination, stem growth and flowering.
128
How is giberellin used?
Controlling dormancy
Inducing flowering
Growing larger fruit
129
How is giberellin used to control plant dormancy?
Lots of seeds won't germinate until they have been through certain conditions eg a period of dry or coldness. This is called dormancy. Seeds can be treated with gibberelin to alter dormancy and make them germinate at times of year that they wouldn't normally. It also helps to make sure all the seeds in a batch germinate at the same time.
130
How is giberellin be used to induce flowering?
Some plants require certain conditions to flower, such as longer days or low temperatures. If these plants are treated with giberellin they will flower without any change in their environment. Giberellin can also be used to grow bigger flowers.
131
How can giberellin be used to grow larger fruit?
Seedless varieties of fruit eg seedless grapes often do not grow as large as seeded fruit. However, if giberellin is added to these fruit, they will grow larger to match the normal types.
132
What does ethene do?
Ethene stimulates the ripening of fruit.
It is a gas produced by ageing parts of a plant. It influences the growth of the plant by controlling cell division. It also stimulates enzymes that cause fruit to ripen.
Commercially, it can be used to speed up the ripening of fruits - either while they are still on the plant, or during the transport to the shops.
This means that fruit can be picked when it is unripe (therefore firmer and less easily damaged). The gas is added to the fruit on the way to the supermarket so that it will be perfect as it reaches the shelves.
Ripening can also be delayed while the fruit is in storage by adding chemicals that block ethene's effect on the fruit, or reduce the amount of ethene that the fruit can produce. Alternatively, some chemicals can be used that react with ethene to remove it from the air.
