Homeostasis Flashcards
1
Q
What is homeostasis?
A
- regulation of the internal conditions of a cell or organism to maintain optimum conditions for function in response to internal and external changes.
2
Q
Why is homeostasis important for cells and organisms?
A
-maintains optimal conditions for enzyme action and all cell functions.
3
Q
What are 3 internal conditions homeostasis regulates
A
-Blood glucose concentration
-Body temperature
-Water levels
4
Q
What are the two types of control systems involved in homeostasis?
A
-Nervous responses and chemical responses.
5
Q
What is the role of receptors in a control system?
A
-Receptors detect stimuli, which are changes in the environment.
6
Q
What is the role of coordination centres in a control system?
A
-Coordination centres (such as the brain, spinal cord, and pancreas) receive and process information from receptors.
7
Q
What is the role of effectors in a control system?
A
- Effectors, which are muscles or glands, bring about responses to restore optimum levels.
8
Q
What sequence of events describes how the nervous system works?
A
Stimulus -> receptor -> coordinator -> effector -> response
9
Q
What is the function of the nervous system in humans?
A
-the nervous system enables humans to react to their surroundings and coordinate their behaviour
10
Q
How does information travel to the central nervous system?
A
-information from receptors passes along cells (neurones) as electrical impulses to the central nervous system (CNS)
11
Q
What does the central nervous system (CNS) consist of?
A
-The CNS consists of the brain and spinal cord.
12
Q
What are reflex actions and how are they different from voluntary actions?
A
-Reflex actions are automatic and rapid responses that do not involve the conscious part of the brain.
13
Q
How does a stimulus lead to a response being carried out by the body?
A
-stimulus is converted into an electrical impulse by the receptors
-the electrical impulse passes along sensory neurones to the central nervous system (CNS)
-the CNS coordinates an appropriate response and an electrical impulse is sent along motor neurones to the effector, which carries out the response
14
Q
Describe how a reflex action occurs via a reflex arc
A
-The stimulus is detected by a receptor
-An electrical impulse passes along a sensory neurone and a relay neurone, a chemical diffuses across the gap and stimulates a new impulse which passes along the relay neurone
-the same process occurs at a synapse between a relay and a motor neurone
-at the effector an appropriate response is carried out
15
Q
Why are reflex actions important?
A
-aid survival by preventing harm to the body
16
Q
What is the difference between a reflex pathway and a conscious pathway?
A
-within a reflex pathway, the coordination centre is a relay neurone found in the spinal cord/unconscious parts of the brain
-In a conscious pathway, the coordination centre is in the conscious part of the brain
17
Q
What does the brain control?
A
-complex behaviour
18
Q
What is the brain made of?
A
-billions of interconnected neurons.
19
Q
How do scientists map regions of the brain to specific functions?
A
-by studying patients with brain damage
-by electrically stimulating different parts of the brain and look at the effects on the person’s behaviour
-using MRI scanning techniques to look at which parts of the brain are most active during different activities
20
Q
Why is it difficult to investigate and treat brain disorders?
A
-complexity and delicacy of the brain.
21
Q
what is the function of the cerebral cortex?
A
-it controls language, memory, consciousness and intelligence
22
Q
What is the function of the cerebellum?
A
-controls our balance and co-ordinates our movements
23
Q
What does the medulla control
A
-controls unconscious activities such as our breathing and heart rate.
24
Q
Why is it difficult to study the brain or treat brain diseases?
A
-the brain is protected by the skull making it very tricky to access.
-the structures of the brain are extremely complex so it is difficult to work out exactly which parts of the brain to carry out specific functions
-the brain is extremely delicate and easy to damage
25
What is the role of the hypothalamus?
-it regulates our temperature and water levels
26
describe the method of the reaction time practical
-person 1 sits on a stool with good upright posture
-person 1 then places the forearm of their dominant arm across the table with their hand overhanging the edge
-person 2 holds a ruler vertically
-the 0 cm mark should be between person 's thumb and first finger
-person 2 then tells person 1 to prepare to catch the ruler
-person 2 now drops the ruler at a random time
-person 1 has to catch the ruler with their thumb and first finger as quickly as possible when it drops
-person 2 now records the measurement on the ruler that is level with the top of person 1's thumb
-the test is repeated several times and a mean is calculated
27
what is the independent variable in a investigation
-what is changed
28
what is the dependent variable in a investigation?
-what is being measured
29
what are control variables
-what we do not allow to change
30
What stimuli are the receptors of the eye sensitive to ?
-light intensity and colour
31
what is the fovea?
-the point where light focuses on the retina
-contains the highest concentration of cone cells and gives the sharpest image
32
What is accommodation in the eye?
-the process of changing the shape of the lens to focus on near or distant objects.
33
How does the eye focus on a near object?
-The ciliary muscles contract, the suspensory ligaments loosen, and the lens becomes thicker, refracting light rays strongly.
34
How does the eye focus on a distant object?
The ciliary muscles relax, the suspensory ligaments tighten , and the lens becomes thin, refracting light rays only slightly.
35
What are myopia and hyperopia?
-Myopia is short-sightedness, and hyperopia is long-sightedness. Both are defects where light rays do not focus on the retina.
36
How are myopia and hyperopia treated?
- with spectacle lenses, which refract light rays so they focus on the retina.
37
What are the treatment methods for treating eye defects?
-spectacle lens (concave for myopia, concave for hyperopia)
-contact lenses (hard or soft)
-laser eye surgery ( reduce cornea thickness or change curvature)
-replacement lens (artificial lens for hyperopia)
38
what is the retina and its function?
-a layer of light sensitive cells found at the back of the eye
-when light hits this, cells are stimulated.Impulses are sent to the brain, which interprets the information to create an image
39
What is the optic nerve and its function?
-a nerve cell that leaves the eye and leads to the brain
-carries impulses from the retina to the brain to create an image
40
what is the sclera and its function?
-a white outer layer which supports the structures inside the eye
-it is strong to prevent some damage to the eye
41
what is the cornea and its function?
- a see-through layer at the front of the eye
-allows light through and the curved surface bends and focuses light onto the retina
42
what is the iris and its function?
-muscles that surround the pupil
-they contract or relax to alter the size of the pupil
43
what is the function of ciliary muscles and suspensory ligaments?
-hold the lens in place and control its shape
44
what happens to the iris in bright light?
-the circular muscles contract and the radial muscles relax to make pupils smaller - avoiding damage to the retina
45
what happens to the iris in dim light?
-the circular muscles relax and radial muscles contract to make the pupil larger - so more light can enter the eye to create a better image.
46
what causes myopia?
-the lens is too curved for distant objects
47
what causes hyperopia?
-the lens is too flat to refract light enough
48
how do spectacle lenses treat myopia?
-they use concave lenses to spread out light
49
how do spectacle lenses treat hyperopia?
-they use convex lenses to bring rays together
50
how do spectacle lenses treat hyperopia?
-they use convex lenses to bring rays together
51
what is the advantage of contact lenses over glasses?
-they allow activities like sports to be carried out
52
what can laser eye surgery do for myopia?
-reduce the thickness of the cornea
53
what can laser eye surgery do for hyperopia?
-change the curvature of the cornea
54
what is a risk of replacement lens surgery?
-damage to retina or cataracts developing
55
Where is body temperature monitored and controlled?
- thermoregulatory centre in the brain.
56
What do the thermoregulatory centre and the skin both contain?
-the thermoregulatory centre contains receptors sensitive to blood temperature
-the skin contains temperature receptors that send impulses to the thermoregulatory centre
57
What happens when the body temperature is too high?
- sweat is produced from sweat glands which evaporates and takes energy from the body,
--Blood vessels dilate (vasodilation) so more blood flows through the capillaries
-heat can now transfer out of blood so body temperature returns back to normal
58
What happens when the body temperature is too low?
Blood vessels constrict (vasoconstriction),
-less blood now flows through the capillaries and less heat is lost from the body
-sweating stops, and skeletal muscles contract (shivering) to generate heat which warms the body
59
What does the endocrine system consist of?
- glands that secrete chemicals called hormones directly into the bloodstream.
60
How do hormones affect the body?
-Hormones are carried by the blood to a target organ where they produce an effect.
61
How do the effects of the endocrine system compare to the nervous system?
- The effects of the endocrine system are slower but last longer compared to the nervous system.
62
What is the role of the pituitary gland?
-The pituitary gland is a ‘master gland’ that secretes several hormones into the blood in response to body conditions.
63
What is the function of the hormones secreted by the pituitary gland?
-These hormones act on other glands to stimulate them to release more hormones, bringing about various effects in the body.
64
what is the function of the pancreas?
-secretes insulin
-controls blood glucose levels
65
what is the function of the thryoid?
-secretes thyroxine
-controls metabolic rate, heart rate and temperature
66
what is the function of the adrenal gland?
-secretes adrenaline
-involved in the 'fight or flight' response ( body's response to stressful situations)
67
what is the function of the ovaries?
-secretes oestrogen
-involved with the menstrual cycle and the development of female secondary sexual characteristics
68
what is the function of the testes?
-secretes testosterone
-involved in the production of sperm and the development of male secondary sexual characteristics
69
How is blood glucose concentration controlled?
-by the pancreas.
70
What happens when blood glucose concentration is too high?
-The pancreas produces insulin, which causes glucose to move from the blood into cells. In liver and muscle cells, excess glucose is converted to glycogen for storage.
71
What is Type 1 diabetes?
- a disorder where the pancreas fails to produce sufficient insulin, leading to uncontrolled high blood glucose levels. It is treated with insulin injections.
72
What happens when blood glucose concentration is too low?
-The pancreas produces glucagon, which causes glycogen to be converted into glucose and released into the blood.
73
When does Type 2 diabetes occur ?
- when the body's cells no longer respond to insulin produced by the pancreas.
74
How is Type 2 diabetes treated?
-with a carbohydrate-controlled diet and an exercise regime.
75
What is a risk factor for Type 2 diabetes?
- Obesity is a risk factor for Type 2 diabetes.
76
what are neurones?
-specialised nerve cells
77
what is the role of sensory neurones?
-to carry electrical impulses from receptors to the brain and spinal cord ( CNS)
78
what is the role of the relay neurone?
-carries electrical impulses from one part of the CNS to another.
79
what is the role of the motor neurone?
-carries electrical impulses from the CNS to an effector
80
describe the function of receptors in the skin
-the receptors in the skin detect stimuli and convert it into a electrical impulse
81
what is a synapse?
-a gap between two neurones
82
what are the differences between the nervous system and the endocrine system?
-the nervous system uses electrical impulses while the endocrine system uses hormones which are chemicals
-the endocrine system produces a much slower effect
-the effects of the endocrine system is long lasting
83
what is type 1 diabetes?
-when the pancreas does not produce enough insulin
84
how is blood glucose concentration monitored in a normal person?
-when the blood glucose concentration rise the pancreas releases insulin causing the glucose concentration to fall
-when glucose concentration falls to a certain level, the pancreas releases glucagon causing blood glucose concentration to rise again
85
why do scientists say insulin and glucagon form a negative feedback cycle?
-they have opposite effects on the blood glucose concentration.
86
What is lost from the skin during sweating?
-Water, ions, and urea
87
Can water, ion, or urea loss through the lungs or skin be controlled?
-no
88
What happens to excess amino acids from protein digestion?
- In the liver, excess amino acids are deaminated to form ammonia, which is toxic and is immediately converted to urea for safe excretion.
89
How are excess water, ions, and urea removed from the body?
-They are removed via the kidneys in the urine.
90
What happens if body cells lose or gain too much water by osmosis?
-they do not function efficiently.
91
How do the kidneys produce urine?
-by filtration of the blood and selective reabsorption of useful substances, such as glucose, some ions, and water.
92
How is the water level in the body controlled?
-by the hormone ADH, which acts on the kidney tubules.
93
How is the release of ADH controlled?
-by negative feedback.
94
How can kidney failure be treated?
- by organ transplant or kidney dialysis.
95
what is osmosis?
-the diffusion of water from a dilute solution to a concentrated solution through a partially permeable membrane
96
what are the three ways the body loses water?
-via the lungs when we exhale
-when we sweat we lose water through the skin
-via the kidneys in urine
97
How does the body control how much water is lost in the urine?
-if the blood is too dilute, the kidneys remove the excess water and they produce a greater volume of urine
-as well as excess water urea and excess ions are also removed in urine
98
how do the kidneys remove the waste product urea?
-humans have two kidneys
-blood enters the kidney through an artery and this blood contains the waste product urea
-the kidney removes this urea as well as excess ions and excess water
-these leave the kidney in urine and this is stored in the bladder
-blood now leaves the kidney through a vein and now has no urea
99
how do kidneys adjust the level of molecules in the blood?
-Blood passes through capillaries where small molecules, including urea, ions, water, and glucose, are filtered out.
-These molecules enter a tube, where glucose, some ions, and some water are reabsorbed back into the blood
- Urea, excess ions, and excess water are then released as urine.
100
why is the concentration of glucose in the blood the same after it has passed through the kidneys?
-the kidneys filter glucose out of the blood but then reabsorb it all back into the blood.
101
why has the concentration of ions decreased after passing through the kidneys?
-kidneys filter ions out of the blood but then reabsorb a certain amount of ions back into the blood.
102
what happens when the blood is too concentrated
-ADH is released by the pituitary gland when the blood is too concentrated.
- ADH travels to the kidneys and causes more water to be reabsorbed back into the blood from the kidney tubules.
-because of this less urine is produced and the amount of water in the blood rises back to its level so the pituitary gland stops releasing ADH
103
what happens if the blood becomes too dilute?
-the concentration of water in the blood rises and the pituitary gland stops releasing ADH
-the kidney reabsorb less water into the blood
-more urine is produced and the concentration of water in the blood returns back to normal
104
how will kidney dialysis work?
-In kidney dialysis, the patient’s blood passes over a semi-permeable membrane that allows urea, ions, and water through but does not allow larger molecules like proteins and blood cells. On the other side of the membrane, dialysis fluid contains normal levels of water and ions but no urea. A concentration gradient causes urea to diffuse into the fluid. The fluid is constantly refreshed to maintain this gradient. The fluid also helps balance the patient’s water and ion levels by allowing them to diffuse from blood into the dialysis fluid, restoring normal concentrations
105
what are the advantages and disadvantages of dialysis?
-there is no shortage of dialysis machines
-requires frequent treatments and a controlled diet
-expensive in the long term
106
what are the advantages and disadvantages of kidney transplant?
-allows patient to lead a normal life
-it is only expensive initially
-shortage of kidney donors
-patients have to take anti-rejection drugs for rest of life
107
What causes secondary sex characteristics to develop during puberty?
- Reproductive hormones.
108
What is the main female reproductive hormone?
-Oestrogen which is produced in the ovary
109
What happens during ovulation?
-An egg is released from the ovary approximately every 28 days.
110
What is the main male reproductive hormone?
- testosterone which is produced in the testes
111
What does testosterone stimulate?
-Sperm production.
112
What hormones are involved in the menstrual cycle of a woman?
- Follicle stimulating hormone (FSH), Luteinising hormone (LH), Oestrogen, and Progesterone.
113
What does FSH (Follicle Stimulating Hormone) do?
-causes the maturation of an egg in the ovary.
114
What does LH (Luteinising Hormone) do?
-stimulates the release of the egg from the ovary.
115
What role do oestrogen and progesterone play in the menstrual cycle?
-help maintain the uterus lining.
116
What are hormonal and non-hormonal methods of contraception used for?
-To control fertility.
117
What do oral contraceptives contain?
-They contain hormones that inhibit FSH production so no eggs mature.
118
What do injection, implant, or skin patch methods of contraception release?
-Slow-release progesterone to inhibit egg maturation and release.
119
What are barrier methods of contraception?
-condoms and diaphragms that prevent sperm from reaching an egg.
120
What do intrauterine devices (IUDs) do?
-They prevent the implantation of an embryo or release hormones.
121
What is the function of spermicidal agents?
-They kill or disable sperm.
122
How does abstaining from intercourse prevent pregnancy?
-prevents sperm from reaching the egg when an egg may be in the oviduct.
123
What are surgical methods of contraception?
-Male and female sterilisation.
124
What does In Vitro Fertilisation (IVF) involve?
-Stimulating the maturation of several eggs using FSH and LH, collecting eggs, fertilising them in a lab, and inserting embryos into the uterus.
125
what are disadvantages of IVF
-IVF is emotionally and physically stressful.
- The success rates are not high.
-can cause multiple births which can be a risk to both the babies and the mother.
126
describe the 4 stages of the menstrual cycle
1)Day 1 - menstruation starts. The uterus lining breaks down for about four days
2)The uterus lining builds up again, from day 4 to day 14, into a thick layer full of blood vessels, ready to receive a fertilised egg.
3)An egg develops and is released from the ovary at day 14 , this is called ovulation
4)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.
127
describe the function of progesterone?
-maintains the lining of the uterus
-inhibits the release of LH and FSH
128
describe the function of oestrogen
-causes the lining of the uterus to grow
-stimulates the release of LH and inhibits the release of FSH
129
what are the side effects of 'the pill' - an oral contraceptive
-headaches and nausea
-does not protect against sexually transmitted diseases
130
what is a fertility drug?
-FSH and LH are given to a woman causing a women to ovulate more than usual + increases her chances of becoming pregnant through sexual intercourse
131
what is an advantage of IVF?
-gives a woman the chance to have a baby of her own
132
what is adrenaline and what does it do in the body?
-adrenaline is produced by the adrenal glands during fear or stress
-it increases heart rate and boosts oxygen and glucose delivery to the brain and muscles, preparing the body for 'flight or fight'
133
What role do plant hormones play?
- Plant hormones coordinate and control growth and responses to light (phototropism) and gravity (gravitropism or geotropism).
134
What causes unequal growth rates in plant roots and shoots?
- Unequal distributions of auxin in plants cause unequal growth rates in roots and shoots.
135
What is the role of gibberellins in plants?
-important in initiating seed germination.
136
What does ethene control in plants?
-cell division and the ripening of fruits.
137
What does thyroxine do in the human body?
- Thyroxine, produced by the thyroid gland, stimulates the basal metabolic rate and plays an important role in growth and development.
138
How are plant growth hormones used in agriculture and horticulture?
-to regulate growth and other processes in plants.
139
How are auxins used in agriculture and horticulture?
- weed killers, rooting powders, and to promote growth in tissue culture.
140
How is ethene used in the food industry?
-to control the ripening of fruit during storage and transport.
141
What are some uses of gibberellins in agriculture?
- Gibberellins can be used to end seed dormancy, promote flowering, and increase fruit size.
142
what is a tropism?
-the response of a plant to a specific stimulus
143
what is phototropism?
-the response of a plant's shoot or root to light
144
what is gravitropism?
-the response of a plant's shoot or root to gravity
145
what is auxin?
-a hormone which controls the growth of a plant's shoots and roots
146
how do plant shoots show positive phototropism?
-one side of the shoot is in the light, causing auxin to move to the shaded side
-at the shaded side, the cells are stimulated to grow - the shoot bends towards the light
-as a result, photosynthesis can occur at a faster rate
147
how do plants show negative gravitropism?
-in a horizontal shoot, auxin accumulates in the lower side due to gravity
-cells on the lower side of the shoot grow more, causing the shoot to bend away from the direction of gravity
-as a result, more light is usually available for photosynthesis
148
how do plant roots show positive gravitropism?
-in a horizontal shoot, auxin accumulates in the lower side, causing cells to grow less
-the root bends in the direction of gravity
-as a result, more water and nutrients are available to the plant roots
149
what are gibberellins?
-a type of plant hormone involved in seed germination
150
what is ethene?
-a type of plant hormone involved in cell division and ripening
151
what is the independent variable in the required practical for plant response?
-the light intensity
152
what is the dependent variable in the plant response required practical?
-the height of the seedlings
153
describe the required practical for plant responses?
-we place cotton wool in three petri dishes and then soak them with equal volumes of water
-we then place ten mustard seeds in each dish
-next we leave the dishes in a warm place and allow the seeds to germinate
-water the seeds every day with the same volume of water
-after a few days, the seeds will germinate + we need to make sure the three dishes have the same number of seedlings
-we use a ruler to measure the height of each seedlings by holding the stems to make sure they are straight
-we place the three dishes in different conditions e.g one dish is places in full sunlight for example
-we measure the height of each seedlings by holding everyday for atleast five consecutive days and record in a table
-when experiment is finished we calculate a mean seedlings height for each day
154
what is the control variable for plant responses practical
-the volume of water
155
Where is the thyroid gland found?
-the base of the neck
156
What does thyroxine do in the body?
-stimulates the body’s basal metabolic rate causing chemical reactions to take place at a faster rate
-plays an important role in grow and development
157
What happens when thyroxine levels fall or increase
-thyroxine levels are controlled by negative feedback which acts to increase or decrease the levels by hormones released by the pituitary gland to return the levels back to normal
158
Which two hormones do hormonal methods of contraception use
Oestrogen and progesterone
159
How does the steady release of oestrogen and/or progesterone prevent pregnancy
The inhibit the release of FSH which means eggs can’t mature and be released
160
Name five hormonal methods of contraception
-oral contraceptive pills
-skin patch
-injection
-implant
-IUD
161
What is the combined oral contraceptive pills?
-a pill containing oestrogen and progesterone to prevent pregnancy
-it is 99% effective but can have side effects such as headaches or nausea
-the pill has to be taken everyday for 21 days , followed by a 7 day break and repeat
162
what is the progesterone-only pill?
-a pill containing progesterone to prevent pregnancy
-it is 99% effective and often has fewer side effects than the combined oral contraceptive pill
-the pill has to be taken every day
163
what is a contraceptive skin patch?
-a patch that can be placed on the skin and slowly releases hormones to prevent pregnancy
-each patch lasts 1 week
164
what is a contraceptive injection?
-an injection of hormones to prevent pregnancy
-each injection lasts 3 months
165
what is a contraceptive implant?
-a small device, injected under the skin, that slowly releases hormones to prevent pregnancy
-each implants lasts 3 years
166
What is a IUD?
-a small device, placed in the uterus, that slowly releases hormones to prevent pregnancy
-each IUD can last up to 5 years
167
name 4 examples of non-hormonal methods of contraception
-condoms
-spermicides
-sterilisation
-abstaining from intercourse
168
how does sterilisation work for males?
-the sperm is cut and tied, so that sperm cannot be ejaculated
169
how does sterilisation work for females?
-the fallopian tubes (oviducts) are cut and tied, so that eggs from the ovaries cannot reach the uterus
170
how does a synapse transmit an electrical signal?
-when an electrical impulse reaches the end of a neurone, it causes the release of chemicals (neurotransmitters)
-these chemicals then diffuse across the synapse and stimulate the next neurone to carry another electrical impulse
