homeostasis and response Flashcards
(90 cards)
1
Q
What is homeostasis? Why is it needed?
A
Homeostasis is the regulation of internal conditions of a cell or organism to maintain optimum conditions for a function in response to internal or external changes. This is needed because enzymes and cells require very specific conditions in order to work.
2
Q
Give three examples of homeostasis in the human body.
A
examples of homeostasis in the human body:
- controlling blood glucose concentration
- body temperature
- water levels
3
Q
What two things may be involved in automatic control systems?
A
Automatic control systems may involve nervous responses or chemical responses.
4
Q
Give the five steps in automatic control systems.
A
automatic control systems:
1) stimulus - a change in the environment
2) receptor cells - detect changes in the environment
3) co-ordination centre - receives and processes information from receptor cells (eg. brain, spinal chord, pancreas)
4) effector - carry out responses to restore optimum levels (a muscle or gland)
5) response
5
Q
What are the two parts of the nervous system?
A
The nervous system has two parts, which are the central nervous system (CNS, brain and spinal chord) and the nerves running from the CNS.
6
Q
Describe how the nervous system works.
A
The nervous system passes information from receptors along neurones as electrical impulses to the CNS, which coordinates the response of effectors (muscles contracting, glands secreting hormones etc.), which enables humans to react to their surroundings.
7
Q
Describe the reflex ark.
A
reflex ark:
- no conscious decision making, so they are automatic and rapid
1) stimulus is detected by a receptor
2) electrical impulses pass from the receptor along a sensory neurone to the CNS
3) at the end of this is a junction (synapse), and a chemical is released
4) this chemical diffuses across to a relay neurone in the CNS
5) this triggers an electrical impulse, sent along the relay neurone, to a synapse, which releases chemicals diffused across to a motor neurone
6) this passes to an effector
8
Q
What does the brain control?
A
The brain controls complex behaviour, such as language. It contains billions of interconnected neurones.
9
Q
What is the cerebral cortex?
A
The cerebral cortex is the outer, highly folded front part of the brain. It is responsible for consciousness, intelligence, memory and language.
10
Q
What is the cerebellum?
A
The cerebellum is responsible for muscle coordination and balance.
11
Q
What is the medulla?
A
The medulla controls unconscious activities like breathing and heart rate.
12
Q
Give three reasons why studying the brain difficult.
A
studying the brain is difficult as:
- it’s protected by the skull, so it’s tricky to access
- the structures are complex
- it’s extremely delicate
13
Q
Name three ways scientists investigate the brain.
A
investigating the brain:
- neuroscientists look at people with brain damage and try to link what’s happening with the damaged part of the brain
- electrically stimulate the brain to look at the effects on behaviour and link this to the part of the brain
- MRI scanning to look at which parts of the brain are most active during certain activities
14
Q
What is the eye?
A
The eye is a sense organ containing receptors sensitive to light intensity and colour.
15
Q
What is the cornea?
A
The cornea is where light rays pass through. It is transparent, at the front of the eye and they start focusing the rays.
16
Q
What is the pupil?
A
The pupil is where the light rays pass through after the cornea. It is in the centre of the iris.
17
Q
What is the iris?
A
The iris gives the eye its colour. They contain muscles to control the size of the pupil, and so control how much light enters.
18
Q
What is the lens?
A
The lens is where light passes through after the pupil. It focuses the light rays onto the back of the eye. It can change shape so it can focus on near or far objects.
19
Q
What is the retina?
A
The retina is the back of the eye where the light rays focus. It contains receptor cells for light intensity and colour.
20
Q
What is the optic nerve?
A
The optic nerve passes electrical impulses from the receptor cells to the brain.
21
Q
What is the sclera?
A
The sclera is the white part of the eye, which is tough to protect the eye.
22
Q
What are the suspensory ligaments and the ciliary muscle?
A
The suspensory ligaments and the ciliary muscle work with the lens to focus on near or distant objects. The ciliary muscle is round and connected to it in straight lines connected to the eye are suspensory ligaments.
23
Q
What is accommodation, in terms of the eye?
A
Accommodation is the process of changing the shape of the lens to focus on near or distant objects.
24
Q
What happens to the eye in bright light?
A
In bright light, the circular muscles are contracted to make the pupil smaller so that less light goes in.
25
What happens to the eye in dim light?
In dim light, the radical muscles are contracted to widen the pupil so that more light goes in.
26
Describe how the eye focuses on a near object.
how the eye focuses on a near object:
- light from near objects needs to be focused a large amount
- the ciliary muscles contract
- this causes the suspensory ligaments to loosen
- the lens is now thicker and refracts light more strongly so that the light rays focus on the retina
27
Describe how the eye focuses on a distant object.
how the eye focuses on a distant object:
- light from distant objects needs to be focuses only a relatively small amount
- the ciliary muscles relax
- the suspensory ligaments are pulled tight
- the lens is pulled thin and slightly refracts light so that the light rays focus on the retina
28
What is it called if someone is long sighted? How is it caused?
long sighted (hyperopia)
- cannot focus on near objects
- this is because the eyeball is too short or the lens has become less elastic (so can't become thick enough to focus on near objects)
- light is focused to a point behind the retina
29
What is it called if someone is short sighted? How is it caused?
short sighted (myopia)
- cannot focus on far objects
- this is because the eyeball is too long or the lens is too thick
- light is focused in front of the retina
30
Give four ways in which eyesight problems can be treated.
treatments for eyesight:
- myopia is treated with concave lens glasses, which partially unfocus the rays before they enter the eye --> )(
- hyperopia is treated with convex lens glasses, which partially focus the rays before they enter the eye --> ()
- contact lenses
- laser eye surgery changes the shape of the cornea, so it refracts light more or less
- replacement lens surgery with an artificial lens
31
What is thermoregulation?
Thermoregulation is the regulation of body temperature. The normal body temperature is 37 degrees Celsius.
32
What is the part of the brain that controls and monitors body temperature?
The thermoregulatory centre is the part of the brain that monitors and controls the body temperature.
33
Where are there receptors to monitor body temperature?
The thermoregulatory centre contains receptors which are sensitive to the temperature of the blood. The skin also contains temperature receptors, which sends electrical impulses down sensory neurones to the thermoregulatory centre.
34
What happens if the body temperature is too high?
body temperature too high:
- sweat glands release sweat which evaporates, taking energy from the body, cooling it down
- vasodilation - the blood vessels dilate (get wider), so more blood flows to the capillaries and heat can transfer out of the blood
35
What happens if the body temperature is too low?
body temperature too low:
- stop sweating to conserve more heat energy
- vasoconstriction - blood vessels constrict, so less blood flows through the capillaries and less heat is lost
- shivering, means that the skeletal muscles contract, so to generate energy for this, the muscle cells increase the rate of respiration to release heat
36
What is the endocrine system?
The endocrine system consists of a number of glands which secrete hormones directly into the bloodstream, which then act only on a target organ, where it produces an effect. It is slower than the nervous system, but the effects last longer.
37
What is the function of the pancreas in the endocrine system?
In the endocrine system, the pancreas produces and releases insulin, which is used to regulate blood glucose level.
38
What is the function of the ovaries in the endocrine system?
In the endocrine system, the ovaries produce oestrogen, which is involved in the menstrual cycle.
39
What is the function of the testes in the endocrine system?
In the endocrine system, the testes produce testosterone, which controls puberty and sperm production in males.
40
What is the function of the thyroid?
In the endocrine system, the thyroid produces thyroxine which is involved in regulating the rate of metabolism, heart rate and temperature, as well as growth.
41
What is the function of the adrenal glands?
In the endocrine system, the adrenal glands produce adrenaline, which is used to prepare the body for the 'fight or flight' response.
42
What is the function of the pituitary gland?
In the endocrine system, the pituitary gland is located in the brain and produces and releases several different hormones to regulate body conditions. It is often called the 'master gland' as these hormones act on other glands, directing them to release hormones that bring about change.
43
What happens if the blood glucose level is too high?
blood glucose too high:
- pancreas produces the hormone insulin
- this causes glucose to move from blood into cells
- insulin also causes excess glucose to be converted to glycogen for storage in the liver and muscle cells
44
What is glycogen?
Glycogen is the storage molecule in humans for glucose.
45
What is type one diabetes? How is it monitored?
type one diabetes:
- the pancreas doesn't produce enough insulin
- characterised by uncontrolled high blood glucose levels, so very little is converted to glycogen (storage) or taken into the cells
- it is monitored with insulin injections
46
What is type two diabetes? How is it treated? Give a risk factor.
type two diabetes:
- when the body cells stop responding to insulin
- it is treated with a controlled carbohydrate diet and an exercise regime
- obesity is a risk factor
47
What happens if the blood glucose level is too low?
blood glucose too low:
- pancreas produces the hormone glucagon
- this causes glycogen to be converted back into glucose and released back into the blood
48
What is glucagon?
Glucagon is a hormone released by the pancreas that causes glycogen to be converted back into glucose and to be released into the blood.
49
Give three ways in which water leaves the body.
ways in which water leaves the body:
- the lungs during exhalation
- through sweat (along with ions and urea)
- by the kidneys in urine (this can be controlled)
50
What happens if body cells gain or loose too much water by osmosis?
If body cells gain or loose too much water by osmosis, they do not function efficiently.
51
Describe the processes that the kidneys carry out to remove waste products from the blood.
kidneys:
- blood enters the kidneys through an artery containing the waste product urea
- kidneys remove urea, excess water and ions
- blood passes through capillaries
- small molecules are filtered out (urea, ions, water, glucose)
- all glucose, some ions and water are reabsorbed into the blood (selective reabsorbtion)
- no urea is reabsorbed
- this leaves the kidney as urine and is stored in the bladder
- blood leaves the kidney through a vein
52
Describe the process of deamination.
deamination:
- in the liver, amino acids are broken down into ammonia
- ammonia is toxic so it is immediately converted to urea for safe excretion
53
What happens if the blood is too concentrated?
blood is too concentrated (low water):
- the pituitary gland releases the hormone ADH into the bloodstream
- ADH affects the kidneys by making tubules (small tubes) more permeable to water, so more water is reabsorbed into the blood
54
What happens if the blood is too dilute?
blood is too dilute (high water):
- the pituitary gland stops releasing ADH
- less ADH affects the kidneys by making tubules (small tubes) less permeable to water, so less water is reabsorbed into the blood
55
Name two treatments to kidney failure.
treatments to kidney failure:
- kidney dialysis
- kidney transplant
56
Describe the process of kidney dialysis.
kidney dialysis:
- level of ions, water and urea are adjusted by a machine
- patients blood passes through a semi permeable membrane, allowing urea, ions and water through, but not larger molecules
- on the other side is dialysis fluid, containing a normal concentration of water and ions, and no urea
- therefore, there is a concentration gradient for urea, so it will diffuse into the dialysis fluid
- small concentration gradient for water and ions, so only some pass through
57
What is kidney failure?
When kidneys fail, blood contains too much water, ions and urea.
58
Give one advantage and three disadvantages of kidney dialysis.
kidney dialysis advantages:
- no shortage of machines
kidney dialysis disadvantages:
- expensive in the long term
- need to visit the hospital several times a week
- controlled diet so that there is not too much urea
59
Give two advantages and three disadvantages of kidney transplants.
kidney transplant advantages:
- only expensive initially
- drugs can be taken to reduce the risk of rejection
kidney transplant disadvantages:
- yet in some cases, the kidney is rejected by the immune system
- shortage of doners
- drugs must be taken for their entire life
60
What do reproductive hormones cause in men and women?
Reproductive hormones cause secondary sex characteristics to develop. For example, pubic hair.
- in men, the testes produce testosterone to stimulate sperm production
- in women, the ovaries produce oestrogen
61
What is ovulation?
Ovulation is when the eggs begin to mature and one is released approximately every 28 days.
62
Describe what happens to the uterus if sperm is or is not present.
- uterus lining becomes thick and spongy
- egg makes it way to the uterus
if sperm is present
- the egg can be fertilised and implants itself into the uterus wall
if sperm isn't present
- both the egg and uterus are released
63
What is FSH?
FSH is the follicle simulating hormone that causes an egg to mature in the ovary. It also triggers the production on oestrogen in the ovaries.
64
What is LH?
LH is the luteinising hormone that causes an egg to be released. It also prevents oestrogen from being released and starts progesterone releasing.
65
What are oestrogen and progesterone?
Oestrogen makes the lining in the uterus thick, and progesterone maintains it. Oestrogen also stops the release of FSH and stimulates the release of LH. Progesterone stops the release of FSH and LH.
66
Describe the stages of the menstrual cycle in terms of the release of hormones and their effects.
the menstrual cycle hormones:
- in the first stage, FSH is released by the pituitary gland and travels to the ovaries, causing an egg to mature, and triggers the ovaries to make oestrogen
- oestrogen makes the lining thick and stops the pituitary gland from releasing more FSH and also it stimulates it to release LH
- LH triggers ovulation
- once the egg is released, progesterone is produced, which stops the release of FSH and LH and keeps the lining thick
67
What is contraception?
Contraception is the prevention of fertilisation.
68
What are oral contraceptives? Give some advantages and disadvantages.
Oral contraceptives contain hormones to inhibit FSH so that no eggs mature. This must be taken everyday, but it is very reliable. It does increase the risk of blood clots and breast cancer. It also does not prevent STDs.
69
What is an implant as a contraceptive? Give some advantages and disadvantages.
An implant as a contraceptive can be a skin patch or an injection which contains progesterone to stop eggs from being matured or released. They are convenient as they last three years, but there are side effects. They also don't prevent STDs.
70
What is a barrier method as a contraceptive? Give some advantages and disadvantages.
A barrier method as a contraceptive prevents the insertion of sperm. It is effective, does not have side effects and reduces the risk of STDs. However, they can break or slip off.
71
How can barrier methods as a contraceptive be made more effective?
Barrier methods as a contraceptive be made more effective by using spermicides as the kill or disable sperm.
72
What is an IUD? Give some advantages and disadvantages.
IUD is an intrauterine device, a contraceptive. It prevents an embryo from implanting by releasing hormones to stop fertilisation. It is highly effective and can be used for 10 years or more. It does not protect against STDs.
73
What are surgical methods as a contraceptive? Give some advantages and disadvantages.
Surgical methods as contraception include sterilisation. In a female, this prevents an egg from reaching the uterus and in males, it prevents sperm from leaving the penis. It is highly effective. It does not protect against STDs and is difficult to reverse.
74
What is abstinence as a contraceptive? Give some advantages and disadvantages.
Abstinence as a contraceptive is avoiding sex when ovulating. This is highly effective and prevents the spread of STDs. It is hard to tell when the person is ovulating.
75
Name six contraceptives.
contraceptives:
- abstinence
- IUD (intrauterine device)
- barrier methods (eg. condoms)
- surgical methods (eg. vasectomy)
- implants
- oral contraceptives
76
How can infertility be treated?
Infertility can be treated by giving FSH or LH to a woman in an infertility drug, which causes her to ovulate more than usual.
77
What is IVF?
in-vitro fertilisation (IVF):
- the mother is treated with FSH and LH, causing several eggs to mature
- the eggs are collected from the mother and fertilised by the father's sperm in the lab
- the fertilised eggs develop into embryos
- when becomes a small ball of cells, it is inserted back into the uterus
78
Give six disadvantages of IVF.
disadvantages of IVF:
- success rates are low
- very expensive
- many embryos are destroyed
- it can lead to multiple births, risking the babies and the mother
- it is emotionally stressful for the parents
- physically demanding for the mother
79
What is negative feedback?
Negative feedback counteracts a change.
80
Where are adrenal glands? What do they do?
Adrenal glands are located at the top of the kidneys. They produce adrenaline in times of fear or stress to increase heart rate and boost the delivery of oxygen and glucose to the brain and muscles, preparing for the fight or flight technique. This is negative feedback.
81
Where is the thyroid gland? What does it do?
The thyroid gland is at the base of the neck. It releases thyroxine to stimulate the body's basal metabolic rate (faster). It also causes growth and development. This is controlled by negative feedback.
82
What is phototropism?
Phototropism is when the plant grows towards the light.
83
What is gravitropism, or geotropism?
Gravitropism or geotropism is when plant roots grow towards gravity.
84
What is auxin's function in plant tips?
Auxin is produced in plant tips. Light causes the auxin to concentrate on the darker side of the tip. It then spreads down the shoot so that cells grow faster on the darker side and it will bend towards the light.
85
What is auxin's function in plant roots?
Auxin is produced in plant roots. Gravity causes the auxin to concentrate on the lower side, closer to the centre of the earth. In roots, the auxin inhibits cell growth. Therefore, the lower side grows slower and the root bends towards gravity.
86
What is the function of giberellins?
Giberellins are important in initiating seed germination.
87
What is the function of ethene?
Ethene controls cell division and the ripening of fruits.
88
Give three uses of auxins.
uses of auxin:
- weed killers
- rooting powders
- promoting growth in tissue culture
89
Give three uses of giberellins.
uses of giberellins:
- end seed dormancy (causes early germination)
- encouraging flowering
- increase fruit size
90
Give one use of ethene.
use of ethene:
| - control of ripening fruit during storage and transport
