P2: Homeostasis And Response Flashcards
1
Q
What is the pupil?
A
A small hole that lets light into the eye
2
Q
What does the cornea do?
A
Refracts light rays as they enter the eye
2
Q
What does the iris do?
A
Controls the size of the pupil.
3
Q
What does the lens do?
A
Refracts light rays as they enter the eye
4
Q
What do the ciliary muscles do?
A
Control the shape of the lens to focus the light.
5
Q
What do the suspensory ligaments do?
A
Controls the shape of the lens to focus the light
6
Q
What does the retina contain?
A
Receptors that are sensitive to light intensity and colour
7
Q
What does the optic nerve do?
A
Carries impulses from receptors in the retina to the brain
8
Q
What does the sclera do?
A
Supports and protects the eye. A fibrous outer wall.
9
Q
What happens if light is too bright?
A
It can damage the retina
10
Q
What happens to the retina in dim light? (Before the iris reacts)
A
It’s not stimulated enough to give a good image.
11
Q
What does the iris do in bright light?
A
Contracts to make the pupil smaller
12
Q
Why does the eyes’ lens change shape?
A
To help it focus on both near and faraway objects.
13
Q
What does the iris do in dim light?
A
The iris relaxes to make the pupil bigger
13
Q
What do the muscles and ligaments do to focus on a near object?
A
The ciliary muscles contract and the suspensory ligaments loosen. Makes the lens thicker, so light rays are refracted more strongly
14
Q
What is the process of the eyes’ lens changing shape called?
A
Accommodation
15
Q
What do the ligaments and muscles do to focus on a far away object?
A
The ciliary muscles relax and the ligaments tighten. This makes the lens thinner, so light rays are only slightly refracted.
16
Q
Describe the lens in hyperopia.
A
The lens is too thin and doesn’t refract light rays enough.
16
Q
What is hyperopia?
A
A condition where near objects appear blurry. Longsightedness
17
Q
Describe the lens in myopia.
A
The lens is too thick and refracts light rays too much.
17
Q
What is myopia?
A
A condition where far away objects appear blurry. Short-sightedness.
18
Q
What type of lens can be used to correct long-sightedness?
A
Convex lens.
19
Q
What type of lens can be used to correct short-sightedness?
A
Concave lens.
20
Q
Function of the pituitary gland.
A
Produces many hormones
21
Describe how the brain is informed of the image detected by the retina.
An electrical impulse from the receptor of the retina is sent along the optic nerve.
21
Describe the process of IVF
-FSH matures the egg and LH releases the egg
-Eggs are collected from the ovary and fertilisation occurs
-Fertilised egg divides, forming an embryo
-Embryo is inserted into the womb
22
Name the two hormones used in IVF treatment.
FSH and LH
23
Explain how information about something sharp touching the skin reaches the brain.
-Sharp point stimulates receptor in the skin
-Sends an electrical impulse through the sensory neurone to the spinal cord
-Crosses synapse to other relay neurones in the brain
24
What is the name of the connection between nerve cells?
Synapse
25
A person notices a dog in the middle of the road as she is driving, and slams the breaks. Explain how the nervous system brings about this response.
-Eyes act as receptors to stimulus.
-Electrical impulses are sent to the co-ordinator
-These impulses then travel to the leg muscles (the effector).
25
Describe the adaptations of nerve cells.
Long, thin, with many branched connections to either end
26
Explain how alcohol consumption slows down someone’s responses
Affects the nervous system and slows down the reactions. Acts as a depressant.
27
Describe the movement of information from a receptor to an effector.
Stimulus –> Receptor –> Sensory Neurones –> Coordinator (central nervous system (Relay Neurones)) –> Motor Neurones –> Effector –> Response
28
What happens when an electrical impulse hits the end of a nerve cell?
Triggers the release of chemicals that diffuse across the synapses to the next nerve cell, where they trigger another electrical impulse.
29
What generally are effectors?
Muscles or glands.
30
What are in the central nervous system?
Our brain and spinal cord.
31
What are the four main areas in the brain?
Cerebral cortex, pituitary gland, medulla and cerebellum
31
List the general sequence a reflex action follows.
Stimulus –> Receptor –> Sensory Neurone –> Relay Neurone –> Motor Neurone –> Effector –> Response
32
State the functions of the cerebral cortex.
Memory, speech, problem solving.
33
What does the cerebellum control?
Balance, co-ordination of movement and muscular activity.
34
What does the hypothalamus do?
It is the regulating centre for temperature and water balance within the body.
34
What does the medulla control?
Unconscious activities, such as heart rate and breathing rate.
35
What is electrical stimulation of the brain?
Stimulating different parts of the brain with a weak electrical current and asking patients to describe what they experienced.
36
What are the risks of brain surgery?
Due to the complexity and delicacy of the brain, if surgery is undergone more damage or side-effects may be created.
36
What is an MRI scan?
A scan that uses strong magnetic fields and radio waves to show details of brain structure and functions. Patients are asked to perform various tasks, and doctors will see which parts of the brain are active.
37
Name the type of plant response to gravity.
Gravitropism
38
Describe how stems and roots respond differently to high concentrations of auxins.
-Cells in stems grow more.
-Stems in roots grow less
38
Give three reasons why it is useful for a young root to grow towards gravity.
-Anchorage
-Lets root take in water
-Lets root take in ions
38
Name the type of plant response to light.
Phototropism
39
What plant hormone promotes growth?
Auxin
40
What can Gibberellins be used to do?
-End seed dormancy
-Promote flowering
-Increase fruit size
41
What are gibberellins responsible for?
Growth and development, and initiating seed germination,
42
Describe how stems and roots respond differently to gravity.
The stem grows against the force of gravity
The root grows in the direction of gravity.
43
What does ethene do in a plant?
Speeds up ripening in fruit, and controls cell division during plant growth.
44
What are auxins used for in the agriculture and horticulture industry?
-As weed killers
-As rooting powders
-For promoting growth in tissue culture.
44
How is auxin used as a weedkiller?
The auxin makes the weeds grow too quickly/uncontrollably and die.
44
Describe how ethene is used in the food industry.
Fruit is picked unripe and then transported. They are then ripened during storage by adding ethene, and then they are taken to shops to be sold.
45
How can auxin be used as rooting powder?
Plant cuttings can be dipped in auxin before planting, ensuring they grow.
46
What does homeostasis control in the human body?
Blood glucose concentration, body temperature and water levels.
47
Explain how sweating helps to control body temperature.
-Evaporation of water lost from sweat cools the skin
-This cools the blood
47
How is auxin used in tissue culture?
The auxin is used to stimulate cell division and elongation.
48
Explain how insulin controls the blood sugar concentration in a healthy person.
-Insulin is produced by pancreas
-If blood glucose levels are too high, insulin is released
-Allowing glucose to move from the blood cells into liver cells, where it is converted into glycogen
49
Describe how glucagon helps control the blood sugar concentration in a healthy person.
-Excess glucose is stored in the liver as glycogen
-If blood glucose levels fall, glucagon is released from the pancreas
-This stimulates glycogen to be converted back to glucose
-This causes glucose to be released into the blood
50
Which gland is known as the “master gland”?
The pituitary gland.
50
What is a hormone?
A chemical substance, produced by a gland and carried in the bloodstream, which alters the activity of specific target organs.
51
What happens to a hormone once it has been used?
It is destroyed by the liver.
52
List some of the glands.
Pituitary gland, thyroid gland, pancreas, adrenal glands, testes, ovaries.
53
What does thyroxine do?
Increases the metabolic rate.
54
What is adrenaline? (Where is it produced and what does it do)
A hormone produced in the adrenal glands in times of fear or stress that increases breathing rate, heart rate, flow of blood to muscles, conversion of glycogen to glucose, diverts blood away from areas such as the digestive system
55
What is a negative feedback system?
A mechanism to lower raised levels of something, and to raise reduced levels of something.
56
Where is thyroxine produced?
Thyroid gland.
57
What happens when there are low thyroxine levels in the bloodstream?
It stimulates the hypothalamus to release TRH, which causes the pituitary to release TSH, so the thyroid releases more thyroxine.
58
What happens to hormones when there are high thyroxine levels in the bloodstream?
TRH release is inhibited, which inhibits the release of TSH from the pituitary, so less thyroxine is released, so normal blood levels are maintained
59
What is glucose needed for?
Respiration
60
What happens if the blood glucose concentration is too high?
The pancreas produces the hormone insulin that causes glucose to move from the blood into the cells.
61
What are the effects of insulin?
Makes glucose move out of the blood and into cells, makes the liver convert glucose into glycogen and stores it
62
What is produced if blood glucose concentration is too low?
The pancreas releases a hormone called glucagon.
63
What does glucagon do?
Raises the level of glucose in the blood, causes liver and muscle cells to convert glycogen into glucose, causes glucose to move out of cells and into the blood
64
Which factors contribute to the risk of developing Type 2 diabetes?
Obesity, diet, exercise, age.
65
What happens in Type 1 diabetes?
The pancreas fails to produce enough insulin, and is often detected from an early age.
66
What can be done to control blood sugar levels in Type 2 Diabetes?
-Have a carbohydrate controlled diet
-Having an exercise regime
66
What does Oestrogen do?
-Controls the development of female secondary sexual characteristics
-Stimulates the lining of the uterus to grow again after menstruation
-Inhibits production of FSH
-Stimulates release of LH
66
What do people with Type 1 Diabetes have to do to control their blood sugar levels?
-Inject insulin
-Monitor their blood sugar levels throughout the day
-Be careful with their diet
-Exercise
66
What happens in Type 2 Diabetes?
The person’s body cells no longer respond to insulin produced by the pancreas.
67
What does testosterone do?
Controls the development of male secondary sexual characteristics.
68
List some male secondary sexual characteristics.
-Voice breaks
-Hair grows on face and body
-Body becomes more muscular
-Testes start to produce sperm cells
-Pubic and underarm hair grows
-Sexual organs grow and develop
69
List some female secondary sexual characteristics.
-Voice deepens gradually
-Hips get wider
-Breasts develop
-Ovaries start to release egg cells - menstruation starts.
-Pubic and underarm hair grows
-Sexual organs grow and develop
70
On average, how long does the menstrual cycle last?
28 days
71
What does FSH do?
Causes an egg to mature in the ovaries, and stimulates the ovaries to release oestrogen.
72
What does oestrogen do?
Inhibits the production of FSH, repairs, thickens and maintains the uterus lining. Stimulates the release of LH.
73
What does LH do?
Stimulates the egg to be released (ovulation)
74
What does Progesterone do?
Maintains the lining of the uterus during the middle of the menstrual cycle and pregnancy. Inhibits production of LH and FSH.
75
What happens to the placenta when a woman becomes pregnant?
It produces progesterone
76
What are the benefits of oral contraceptives?
Very effective if taken correctly, and can reduce the risk of cancers.
76
What hormones does the oral contraceptive pill contain?
Oestrogen and progesterone
77
What do fertility drugs contain?
FSH and LH.
78
What are the problems with oral contraceptives?
The side effects, including changes in weight, mood and blood pressure.
78
What do contraceptive injections include?
Progesterone
79
Give examples of types of contraceptives.
Physical barrier methods
Intrauterine devices
Spermicidal agents
Abstinence
Surgical methods of sterilisation
80
What does IVF involve?
-Giving a mother FSH and LH to stimulate the maturation of several eggs.
-Collecting the eggs from the mother and fertilising them in a dish in a laboratory
-The fertilised eggs develop into embryos, and the tiny balls of cells are inserted into the mother’s uterus.
81
What are the cons of IVF treatment?
-Expensive
-Low success rates
-Side effects of the drugs
-Emotionally and physically stressful
-Risk of multiple births
82
What happens to the body when we get too hot?
-Sweat glands in the skin release more sweat
-Blood vessels leading to the skin capillaries become wider (vasodilation)
83
What happens to the body when we get too cold?
-Skeletal muscles contract rapidly, and we shiver.
-Blood vessels leading to the skin capillaries become narrower
-Hairs on the skin rise to trap a layer of insulating air next to the skin
84
What happens if body cells gain too much water?
They may burst.
84
What is osmoregulation?
The control of water levels and mineral salts in the blood.
84
What leaves the lungs when we exhale?
Water and Carbon Dioxide
85
What happens if body cells do not gain enough water?
They may shrivel and not function efficiently.
86
How is water lost from the body?
-As urine from the kidneys
-As sweat from the skin
-As water vapour from the lungs when we exhale
87
What is lost in sweat?
Water, ions and urea.
88
What do the kidneys remove from the bloodstream?
Excess water, salts, and urea.
89
What artery is blood transported to the kidney through?
The renal artery.
89
What happens to excess amino acids?
-They are taken to the liver, and deaminated to form ammonia
-Ammonia is toxic, so it is immediately converted to urea for safe excretion.
-Urea is released from the liver cells and passes into the bloodstream, where it is transported to the kidneys and passed out in urine
90
What are the 3 stages of the kidneys when filtering blood?
-Filtration - the kidney absorbs ureas, water, ions and glucose.
-Selective reabsorption - the kidney passes back all of the glucose originally filtered out, some water and some ions back into the bloodstream.
-Formation of urine - molecules that aren’t selectively reabsorbed become urine
90
What is ADH?
Anti-diuretic hormone. Controls the water content of the blood. Increases reabsorption of water by the collecting ducts.
91
What is a dialysis machine?
A machine that acts as an artificial kidney
92
How does dialysis work?
Unfiltered blood is passed through the dialysis machine, which contains a partially permeable membrane and dialysis fluid with a concentration of glucose and ions similar to levels in the blood, and no urea. Diffusion and osmosis occurs across the membrane, which does what the kidney would do.
93
What are the advantages of kidney dialysis?
-Greatly reduces levels of urea
-Allows a person with kidney failure to maintain their health
-Maintains balance of water and ions in blood.
94
What are the disadvantages of kidney dialysis?
-Expensive
-Patients must follow a rigid diet
-Only work for a limited time
-Patient must have their blood connected to the machine for several hours every week
95
What is done to counter organ rejection of a kidney transplant?
-Tissue typing (giving kidneys to patients who have antigens that are similar to the antigens of the donor kidney)
-Immuno-suppressant drugs
96
What are the advantages of kidney transplants?
-Patients can lead a more normal life without having to have a controlled diet
-Cheaper for the NHS
97
What are the disadvantages of kidney transplants?
-Patient must take immuno-suppressant drugs which increase the risk of infection
-Shortage of organ donors
-Kidney only lasts 8-9 years on average
-Operation carries risks.
98
Why do scientists use large numbers of subjects when testing?
To reduce the effect of anomalies by recognising them
98
Explain how thyroxine being produced increases the body temperature.
Thyroxine increases metabolic rate, and respiration releases energy, causing an increase in body temperature
99
What does an MRI scan do?
Allows doctors to see the brain activity without surgery.
