Homeostasis Flashcards
(143 cards)
1
Q
Define homeostasis
A
The regulation of internal conditions of a cell or organism in order to maintain optimum conditions for function in response to internal and external changes.
2
Q
What is the purpose of homeostasis
A
To maintain optimum conditions in response to stimuli, for enzyme action and all cell action.
Enzyme and cell action include cellular respiration.
3
Q
In the human body, state three examples of what is controlled by homeostasis
A
- Blood glucose concentration
- Body temperature
- Water levels
think of endurance athlete
4
Q
What is an automatic control system?
A
A system that mainly involves chemical and nervous responses.
5
Q
What do automatic control systems always include?
A
STIMULUS
Receptor cells
Coordination centre
Effectors
RESPONSE
6
Q
Automatic controls systems can involve what 2 types of responses?
A
Chemical and nervous responses
7
Q
What is a receptor?
A
Cells which detect internal and external stimuli.
(Stimuli = changes to the environment)
8
Q
What is a coordination centre?
A
The place where information is received from the receptor cells and is processed and an appropriate response is coordinated.
9
Q
What is an effector?
A
Muscles or glands which bring about responses to restore optimum levels
10
Q
Examples of receptors, coordination centres and effectors:
A
Receptors = cells
Coordination centres = Brain, spinal cord, pancreas
Effectors = muscles(contracting) or glands (secreting hormones)
11
Q
The nervous system consists of two parts, what are they?
A
- The CNS - the brain and spinal cord
- Neurons
12
Q
Explain how the nervous system works:
A
- Receptor cells detect stimuli in the environment and convert this into an electrical impulse.
- These electrical impulses pass along sensory neurones to CNS.
- At CNS information carried by electrical impulses are received and processed and the appropriate response is coordinated.
- This processed information is converted to an electrical impulse which passes along motor neurones from CNS to the effectors.
- Effectors receive this info and carry out the response to restore optimum levels.
13
Q
What is meant by a reflex action?
A
An automatic and rapid response to a stimulus that does not involve the conscious part of the brain.
14
Q
Why are reflex actions important?
A
- They prevent us from harm and danger because they are automatic and rapid.
- They control everyday body functions because they are automatic.
15
Q
The reflex arc includes what three types of neurones?
A
- Sensory neurones (connected to receptor cells)
- Motor neurones (found in CNS)
- Relay neurones (found in CNS spinal cord, they connect sensory and motor neurones tg)
16
Q
Describe the process of the reflex arc:
A
- Stimulus is detected by receptor cells and is converted into an electrical impulse.
- Electrical impulse passes along sensory neurones until they reach the end of the S neurone body.
- When they reach the end, chemicals are triggered to be released from the S into the synapses between S and R neurones.
- Chemicals diffuse across synapses between S and R neurones until they reach the receptor site of the relay neurone found in the spinal chord.
- This triggers and electrical impulses in the relay neurones.
- Electrical impulses pass thru R neurones body, and once they reach the end of the body, chemical are triggered to be released into the synapses between R and M neurones.
- The chemical diffuse across the synapses until they reach the receptor site of the M neurones.
- This now triggers an electrical impulse to start in the motor neurone.
- Electrical impulse in motor neurone travels through it to the effector.
- Once electrical impulses reach effectors a response to the stimuli is triggered, this included muscles contracting or glands secreting hormones.
17
Q
Label/draw a diagram of the brain
A
18
Q
What is meant by the brain:
A
An organ made up of millions of interconnected neurones which control complex behaviour.
19
Q
True or false, the brain has different regions which carry out different functions?
A
True
20
Q
What are the three main parts of the brain?
A
- Cerebral cortex - highly folded outer part of the brain
- Cerebellum - rounded structure towards the bottom/back of the brain
- Medulla (the stick ‘’/’’) - bottom-most part of the brain, located in the brainstem in front of the cerebellum.
21
Q
Role of cerebral cortex:
A
M.I.L.C - to control memory, intelligence, language and consciousness.
22
Q
Role of the cerebellum:
A
To control and coordinate muscular movement, muscular activity and balance.
(So if someone has difficulty contracting their muscles, you can link this to the cerebellum possibly being affected).
23
Q
Role of the medulla
A
To control unconscious activity such as breathing, digestion and heart rate.
24
Q
How can scientists investigate the brain, treat brain damage and treat brain diseases?
A
- MRI scans
- Electrically simulating different parts of the brain
- Study patients with brain damage.
25
What are the difficulties scientists may face when studying the brain and treating brain damage?
- The brain is protected by the skull which makes it difficult to access.
- The brain is delicate so it is easily damaged.
- The brain is very complex so surgeons may cause damage to certain parts of the brain as it is not easily understood.
- The brain is surrounded by many membranes, this makes it difficult for drugs to easily reach it.
26
Benefits of procedures carried out on the brain and nervous system, by scientists?
- Allows for scientific advancement with respect to helping us understand the basis of human behaviour.
- Can treat brain diseases and brain disorders.
27
How does studying patients with brain damage help scientists understand the brain?
Scientists can link the damaged part of the brain to its function by observing physical changes of the patient.
28
How do MRI scans help scientists understand the brain?
2 ways
- MRI scans create images of the brain to show parts of the brain which are damaged.
- They can then link the damaged part of the brain to its function by observing physical changes in the patient.
OR
- Scientists can use MRI scans to see which part of the brain is **most** active when the patient is carrying out different activities.
- This allows for scientists to link this part of the brain to its function.
29
How does electrically stimulating different parts of the brain help scientists understand the brain?
- When scientists electrically stimulate different parts of the brain, they can observe the effects this has on a person's behaviour and actions. - This allows them to link these parts of the brain to their function.
30
What is meant by the eye?
A sense organ which contains receptors sensitive to light intensity and colour.
31
State the parts of the eye
- Sclera
- Ciliary muscle
- Optic nerve
- Suspensory ligaments
- Iris
- Cornea
- Retina
32
Label a diagram of the eye
33
Role of the cornea
- Transparent *front* layer of the eye.
- Its job is to allow light rays pass through it and it helps to focus the light rays onto the retina.
34
Role of the Sclera
- White outer layer of the eye.
- Its job is to protect the eye and maintain its shape.
Sclera - white outer layer
Cornea - transparent front layer
35
Role of the retina
- A layer of light sensitive receptor cells found at the back of the eye.
- The receptor cells are sensitive to light intensity and light colour.
- ROLE When light reaches the retina, its receptor cells are stimulated and convert this information into an electrical impulse which passes through the optic nerve into the brain. The brain processes this info and converts it into an image.
36
The role of the optic nerve:
A nerve that leaves the eye and leads to the brain.
Its role is to carry electrical impulses from the retina to the brain, for the brain to create an image.
37
The role of the iris
Irises are muscles that surround the pupil.
The role of the iris is to contract or relax to alter the size of the pupil.
38
Ciliary muscles and Suspensory ligaments:
They hold the lens in place and control its shape.
39
In dark conditions (when light intensity decreases)
- The decrease in light intensity is detected by the light receptors on the retina.
- This stimuli is converted into an electrical impulse which passes through the optic nerve into the brain from the retina.
- The brain processes this, coordinates a response and sends this electrical impulses to specific muscles in the iris.
- These muscles contract, causing the pupil to become larger so more light can enter the eye.
40
In bright conditions (when light intensity increases)
- The increase in light intensity is detected by light receptors on the retina.
- This stimuli is converted into an electrical impulse which passes through the optic nerve into the brain
- The brain processes this information and sends an electrical impulse too specific muscles in the iris.
- These muscles relax causing the pupil to become smaller, so less light enters the eye.
41
True or false, the pupil increasing/decreasing due to iris muscles relaxing/contracting is a reflex action? Explain why.
True.
Bc it is a rapid and automatic response that does not involve the conscious part of the brain.
It is essential as it prevents the eye from getting damaged.
42
What is meant by accommodation?
The process of changing the shape of the lens to focus on distant or near object.
43
Lens are associated with what while iris are associated with?
Lens S.L and C.M : focusing on distant or near objects/accomodation.
Iris, and pupil: Increasing/decreasing the amount of light that enters the eye.
44
True or false, the cornea is the fixed focus and the lens is not?
True.
The lens can change shape to allow us to focus on near or distant object while the cornea does not.
(Cornea does main/most of the focusing while the lens does the rest)
45
Describe how the eye focuses on distant objects:
- Light from distant objects needs to be focussed by only a small amount
- So ciliary muscles relax
- Causing suspensory ligaments to be pulled tight
- So the lens is pulled thin
- So light rays are only reflected slightly and focussed onto a point on the retina.
46
Describe how the eye focuses on close objects
- Light intensity from close objects need to be focussed by a large amount.
- So ciliary muscles contract
- Suspensory ligaments loosen
- The lens becomes thicker
- So light ray are refracted more strongly and focussed onto a point on the retina
47
What is myopia and hyperopia?
These are defects of the eye where light rays do not focus onto the retina.
Myopia: Short-sightedness - can focus on nearby objects but not distant ones.
Hyperopia: Long-sightedness - can focus on distant objects but nor nearby ones.
48
Describe 2 common reasons for hyperopia:
1 - The eyeball may be too short.
So light is focussed at a point behind the retina.
2 - Lens may become less elastic, so cannot become thick enough to focus light rays from near objects onto the retina. (common amongst the elderly)
49
Describe the common reason for myopia: x2
The eyeball is too long so light rays from an object focussing at a point in front of the retina.
OR
The lens is too thick resulting in light rays from an object focussing at a point in front of the retina.
50
Ray diagram for a convex lens used to treat hyperopia
Freesciencelessons
51
Ray diagram for a concave lens used to treat hyperopia
Freesciencelessons
52
What type of lens is used to treat hyperopia and describe how?
- Convex lens ()
- Partially focus the light rays from object before it enters the eye.
53
What of lens is used to treat myopia and how?
- Concave lens ) (
- Partially unfocus light rays before they enter the eye.
54
What are some substitutes instead of using glasses:
- Hard/Soft contact lens (sit on the eyeball and refract light in the same way as glasses).
- Laser eye surgery - used to change the shape of the cornea so it refracts light to a greater or lesser extent.
- Replacement Lens: lens inside the eye can be replaced with an artificial lens.
55
What is the optimum/normal human body temperature?
37 degrees Celsius.
56
Where is the thermoregulatory centre located?
In the hypothalamus in the BRAIN.
- It has receptors sensitive to the temperature of blood in the BRAIN
- It has receptors sensitive to the temperature of blood on the SKIN, which send electrical impulses down sensory neurones to the thermoregulatory centre in the brain.
57
What happens when the body temp gets too high?
- Body temperature needs to be decreased
- Receptor cells in skin and brain detect increase in body temp and pass this info as electrical impulses to TRC in the brain.
- TRC coordinates a response and this is carried out by the effectors:
**Sweat glands release sweat onto the skin's surface. The sweat evaporates and takes this heat energy from the skin to the environment, so body cools down.
**Vasodilation - Blood vessels supplying fine network of capillaries under the skin dilate. This means more blood flows to the capillaries just under the surface of the skin. This allows for more heat energy to be transferred out of the blood, from the skin to the environment so the body temp cools and returns to its normal level.
58
What happens when the body temp gets too low?
- Body temp needs to be increased
- Receptor cells in skin and brain detect decrease in body temp and pass this info as electrical impulses to TRC in the brain.
- TRC coordinates a response and this is carried out by the effectors:
**Vasoconstriction - blood vessels supplying capillaries just under the skin constrict/become narrower. This means less blood flows through the capillaries so less heat is transferred from the skin to the environment. So body temp increases and returns its normal temp
**Shivering - occurs where skeletal muscles contract. In order to do this muscles cells increase their rate of respiration to provide heat energy for this contraction. This heat energy increases the body temp and returns it back to its normal temperatures.
**Sweat glands stop releasing sweat onto the skin's surface. This means less heat energy is transferred from the skin to the environment as sweat evaporates.
59
True or false, the control of body temp by the TRC is an example of homeostasis?
True
60
What is meant by the endocrine system?
A system composed of glands which secrete chemicals called hormones into the blood stream.
61
In the endocrine system, where does the blood carry the hormones?
To target organs where it produces an effect.
62
Compare the endocrine system and the nervous system.
DIFF
- The endocrine system carries out its effects slower than the nervous system's.
- The endocrine system's effects last for longer than the nervous system
- The nervous system uses electrical impulses which travel down neurones to send messages around the body while the endocrine system uses hormones which travel in the bloodstream to send messages around the body.
SIM
- They both use chemicals
- They both carry out homeostasis
63
What is the pituitary gland AKA?
The Master Gland.
It secretes several hormones into the blood in response to body conditions.
These hormones act on other glands to stimulate hormones to be released from these glands to bring about effects.
64
What do hormones released from the pituitary gland do?
They travel in the bloodstream to other glands, and stimulate them to release hormones and bring about and effect.
65
Identify these, on a diagram:
* pituitary gland
* pancreas
* thyroid
* adrenal gland
* ovary
* testes.
66
What is an Endocrine gland?
An organ which secretes hormones directly into the bloodstream.
67
Label a diagram of glands in the endocrine system.
68
Role of the pituitary gland
- The Master Gland
- Secretes hormones into the blood to have an effect on the body, or act on other glands to stimulate them to secrete other hormones.
69
Role of the adrenal gland
To secrete adrenaline in response to stressful situations preparing the body for 'fight or flight'.
70
Role of the thyroid gland
To secrete thyroxine, which control's the body's metabolic rate, heart rate and temperature.
71
Role of the ovaries
To secrete oestrogen.
Oestrogen is involved in:
- The menstrual cycle.
- The development of female secondary reproductive characteristics
72
Role of the testes
To secrete testosterone.
Testosterone is involved in:
- The production of sperm.
- The development of male secondary reproductive characteristics.
73
Role of the pancreas
To secrete insulin.
Insulin controls the body's blood glucose concentration.
74
What are hormones?
Chemical messengers.
75
What are secondary reproductive characteristics?
Features developed during puberty that distinguish male from female.
76
What is gland controls and monitors blood glucose concentration:
The pancreas
77
Explain what happens when blood glucose concentration is too high.
(Usually after a carbohydrate-rich meal).
- Pancreas detects the increase of C6H12O6 in BGC
- So it secretes the hormone insulin directly into the bloodstream.
- Insulin is transported around body cells and triggers them to take in glucose from the bloodstream.
- Muscle and liver cells take in glucose from the bloodstream and convert it into glycogen (storage form of glucose).
- This causes the blood glucose concentration to decrease back to its optimum concentration.
(HOMEOSTASIS HAS TAKEN PLACE)
78
Explain what happens when blood glucose concentration is too low.
(Typically in between meals or when u wake up in the morning after sleeping)
- The pancreas secretes a hormone called glucagon into the bloodstream.
- Glucagon travels through the bloodstream to liver cells.
- Glucagon triggers liver cells to convert glycogen stores back to glucose.
- This glucose is released from the liver cells into the bloodstream.
- So the blood glucose concentration increases back to normal.
79
In what cells is glucose converted into glycogen?
Muscle and liver cells.
80
What is type 1 diabetes?
How can it be treated?
A disorder by which the pancreas fails to produce sufficient insulin.
It is characterised with **uncontrolled high blood glucose levels**
It can be treated using insulin injections.
81
What is type 2 diabetes?
How can it be treated?
A disorder by which body cells no longer respond to insulin produced by the pancreas.
It can be treated with:
- A carbohydrate controlled diet.
- An exercise regime
- Weight loss
82
Obesity is a risk factor for what type of diabetes?
Type 2 diabetes
83
Compare type 1 and type 2 diabetes.
- T1 diabetes, the pancreas doesn't **produce** sufficient insulin, while in T2 it does.
- T2 body cells no longer respond to insulin while in T1 they do.
- Obesity is a risk factor for T2 diabetes, while T1 is due to genetics.
- They both result in an uncontrolled increase in BGC
84
How does glucagon interact with insulin in a negative feedback cycle to control blood glucose levels in the body?
- In a **negative feedback cycle**
- When glucose conc rises, pancreas secretes insulin so glucose concentration falls.
- When glucose conc falls, pancreas secretes glucagon so glucose conc rises.
(explain in detail verbally how this happens and look at a graph).
85
What is glucose needed for?
For respiration to release energy, so it's important that BGC is kept constant.
86
Why is glucagon and insulin's interaction referred to as a negative feedback cycle?
Because they have opposite effects on the body's BGC.
~~~~~~~~~~~~~ (wave graph).
87
State three ways by which substances can leave the body.
Water can leave the body via the lungs during exhalation.
Urea, Water and mineral ions can leave the body from the skin by sweat.
Excess mineral ions, Excess water and urea are removed by the kidneys in urine.
88
Explain the consequences of cells losing or gaining too much water by osmosis.
They do not function efficiently.
89
Describe how the kidneys maintain water balance in the body.
- Blood passes through capillaries leading from the arteries.
- This blood contains Urea, excess mineral ions and water, and glucose.
- All of these molecules in the blood are filtered out of the capillaries into the kidney tubules.
- Now some of the water, some of the ions, and all of the glucose is reabsorbed back into the blood from the tubules and is carried away by the veins.
- This is called selective reabsorption
- Urea and the excess ions and excess water are released as urine via excretion (passes from kidney into the bladder and stored in the bladder before excretion).
90
What does the before and after bar chart for glucose, urea, mineral ions and water look like after filtration?
- Glucose before and after = same conc.
- Mineral ions = less after
- Water = less after
- Urea = 0 after.
91
Arteries and veins carry blood to or away from the kidneys?
Arteries - Blood to kidneys (away from heart)
Veins - Away from kidneys (to heart)
92
What is meant by selective reabsorption?
When useful substance are reabsorbed from the kidney tubules back into the bloodstream after filtration
93
What is meant by deamination?
The digestion of proteins from diet results in excess amino acids in the body which need to be excreted safely.
How does this occur? - DEAMINATION
The process by which the liver breaks down excess amino acids to produce the chemical ammonia
Ammonia is a toxic chemical so is immediately converted into urea and removed from the body via excretion.
94
Excretion versus egestion:
Egestion - passing out of undigested food as faeces.
Excretion - removal toxic material and products of metabolism.
95
What happens when the blood concentration is too dilute?
The kidneys produce a greater volume of urine and remove the excess water.
96
Describe the effects of ADH on the permeability of kidney tubules.
WHEN WATER CONC IS TOO LOW, typically caused by a lot of sweating:
- Pituitary gland detects the decrease in H2O conc. and secretes ADH into the bloodstream.
- Blood carries ADH to the kidney and ADH causes kidney tubules to become more permeable to water.
- This results in more water being reabsorbed into the bloodstream from the kidney tubules
- This means less urine is produced so the concentration of water in the blood increases back to normal.
- When the conc returns back to normal ADH is no longer secreted by the P.G.
WHEN WATER CONC IS TOO HIGH
- ADH is no longer released by the pituitary gland into the bloodstream
- So kidney tubules are less permeable to water.
- So less water is reabsorbed into the bloodstream and more urine is produced.
- So conc of water in blood decreases and returns back to its normal level.
97
What hormone controls water levels in the body?
ADH (anti-diuretic hormone)
98
State 2 ways by which people who suffer from kidney failure can be treated.
Through kidney dialysis.
Through kidney transplants.
99
Explain how kidney dialysis works.
- The patient's blood is passed through a partially permeable membrane.
- One one side of the membrane is the patient's blood and on the other, is dialysis fluid.
- The patient's blood contains a higher conc of water, mineral ions and urea than it should.
- The dialysis fluid contains the normal conc of water and mineral ions but contains no urea.
- This provides a steep concentration gradient for urea to diffuse from the patients blood into the dialysis fluid.
- So SOME of the water and mineral ions diffuse through the the partially permeable membrane into the dialysis fluid, from an area of high to low conc.
- ALL urea diffuses from blood through PPM into dialysis fluid.
- The dialysis fluid is constantly refreshed which maintains a steep concentration gradient for all urea to always diffuse from blood into it.
- The PPM membrane only allows for small molecules such as those mentioned above to pass through it, large molecules like proteins, and doesn't allow blood cells to pass through.
- This allows for the person's blood concentration of water and ions to return to normal.
100
What is a kidney transplant?
The process by which a diseased kidney is surgically replaced with a healthy one from a donor.
101
Advantages + Disadvantages kidney transplants and dialysis.
Advantages of dialysis + D of KD
- No shortage of dialysis machines but w KT, there is a shortage of kidney donors.
- No need for anti-rejection drugs while KD does have need for it.
Advantages of KT + D of KD
- Patients can lead a normal life while KD required frequent treatments which can pose as an inconvenience.
- KT doesn't require a controlled diet but KD does.
- Only expensive initially while KD is expensive in the long term
102
What causes secondary sex characteristics to develop during puberty?
Reproductive hormones.
Examples:
Pubic hair
103
What are the MAIN female and male reproductive hormones?
FEMALE - Oestrogen (involved in menstrual cycle and the development of FSSC)
MALE - Testosterone (stimulates sperm to be produced and is involved in the development of MSSC)
104
What is meant by ovulation?
The process by which a female's egg is released from the ovaries and moves into the uterus via the fallopian tube.
105
How often does ovulation approximately occur?
Once every 28 days.
106
What are the hormones involved in the menstrual cycle?
- FSH (Follicle stimulating hormone) causes the maturation of the egg in the ovary
- LH (Luteinising hormone) Stimulates the release of the egg
- Oestrogen (Involved in maintaining the lining of the uterus)
- Progesterone (Involved in maintaining the lining of the uterus)
107
Role of FSH
To cause the maturation of the egg in the ovary.
108
Role of LH
To stimulate the release of the egg (OVULATION).
109
Role of Oestrogen
To maintain the lining of the uterus by causing it to become thick.
110
Role of progesterone
To maintain the lining of the uterus to be thick in case a fertilised egg implants itself.
111
Explain the interactions of FSH, oestrogen, LH and progesterone, in the control of the menstrual cycle.
- FSH is released by the pituitary gland into the bloodstream.
- FSH travels in the blood to the ovaries and it causes the egg in the ovaries to mature.
- FSH also triggers the ovaries to secrete oestrogen.
- Oestrogen causes the lining of the uterus to become thick and inhibits the production of FSH from the pituitary gland
- Oestrogen stimulates the pituitary gland releases LH into the bloodstream which travels in the blood to the ovaries.
- Here, LH triggers the egg to be released from the ovaries into the uterus.
- Once the ovaries have released the egg in to the uterus, the ovaries produce progesterone.
- Progesterone inhibits the production of FSH and LH which prevents any more eggs from maturing or being released.
- Progesterone also maintains the lining of the uterus to be thick in case a fertilised egg implants.
- If fertilisation does not occur, the level of progesterone falls, the uterus lining breaks down and is released with the egg (a period).
- And the cycle repeats itself.
112
Draw and explain menstrual cycle graph
113
What happens if there is no egg fertilised?
Progesterone levels fall, the egg is released and the lining of the uterus breaks down and is also released through a period.
114
How can fertility be controlled?
What are the 6 types of contraceptions.
Via contraception.
* oral contraceptives that contain hormones to inhibit FSH production so that no eggs mature.
* injection, implant or skin patch of slow release progesterone to inhibit the maturation and release of eggs for a number of months or years.
And also increase the amount of mucus in the cervix so sperm doesn't reach it and fertilise the egg.
* barrier methods such as condoms and diaphragms which prevent the sperm reaching an egg.
* intrauterine devices which prevent the implantation of an embryo or release a hormone to thicken cervical mucus to prevent the sperm from reaching the egg for fertilisation.
* spermicidal agents which kill or disable sperm
* abstaining from intercourse when an egg may be in the oviduct
* surgical methods of male and female sterilisation.
115
What is meant by contraception?
The aim to prevent fertilisation and pregnancy through hormonal and non-hormonal methods.
116
Advantages and Disadvantages of oral contraceptive pills:
AD:
- If it is taken correctly it is highly effective.
DISAD:
- Must be taken daily, if a woman forgets to take it there's a risk of pregnancy.
- There are side-effects such as breast cancer and blood clots (low risks)
- Doesn't protect against STI's
117
What hormones do skin patches, injections and implants have?
Progesterone - this stops the egg from maturing and being released as progesterone inhibits the release of FSH and LH.
118
Advantages and Disadvantages of
- Skin patches
- Injections
- Implants
AD
- More convenient than taking a daily pill as they last for longer.
DISAD
- They have side-effects
- Does not protect against STIs
119
Advantages and disadvantages of barrier methods such as condoms and diaphragms.
AD
- They don't use hormones so they don't have side effects.
- They reduce the risk of STI transmission
- Can be very effective if they are used correctly.
DISAD
- They can break or slip off, so not entirely effective. (can use spermicide gels which kill/disable sperm)
120
Advantages and Disadvantages of IUD (intrauterine device)
AD
- They can prevent pregnancy for up to 10 years (a very long time).
- They have very few side effects
DISAD
- Does not protect against STIs
121
Sterilisation:
What is it, + and -
Sterilisation results in the egg being prevented from leaving the uterus, and the sperm being prevented from leaving the penis.
AD
- Highly effective
DISAD
- Difficult to reverse
- Don't protect against STI's
122
Abstinence from sexual intercourse when the egg may be in the oviduct:
Positives and Negatives
POSTIVES
- No side effects
DISAD
- Hard to tell when a woman has ovulated
- Does not protect against STI's
123
Why can the issues around contraception not be answered by science alone?
- Catholic Church teaches that all contraception is unethical apart from natural contraception.
- Many people believe it's a person's right to choose.
- Other's believe that barrier methods of contraception are a good way to prevent STI transmissions.
124
How can a woman's fertility be treated?
- FSH and LH fertility drugs.
- In Vitro Fertilisation - IVF
125
Explain how the 'fertility drug' works.
- FSH and LH are given to women.
- This increases her chances of becoming pregnant through sexual intercourse.
^remember to always link to the roles of each hormone.
126
Explain how IVF works:
- The mother is given FSH and LH to stimulate the maturation of several eggs.
- The eggs are collected from the mother, and fertilised by sperm from the father in the laboratory.
- The fertilised eggs develop into embryos.
- At this stage, when they are tiny balls of cells, one or two embryos are inserted into the mother's uterus.
127
Benefits and 3 problems of IVF:
- It is emotionally and physically stressful.
- The success rates are not high
- It can lead to multiple births which can pose as risks to both the babies and the mother.
- It is an expensive process
ETHICAL
- Not all embryos created are transferred to the mother, so the remaining embryos are destroyed and some people find this unethical.
128
What is the role of adrenaline in the body?
- The adrenal glands produce the hormone adrenaline during times of stress.
- Adrenaline is released directly into the bloodstream.
- One of the effects of adrenaline is to increase the heart rate.
- Because the heart is beating faster there is a boost in the rate at which oxygen and glucose are delivered to the muscles and the brain to be used for aerobic respiration.
- This prepares the body for 'fight or flight'.
129
What is the role of the thyroxine?
- To regulate the body's basal metabolic rate.
- Plays an important role in growth and development.
130
What is meant by metabolism?
The sum of all the body's chemical reactions.
131
What is the level of thyroxine in the blood controlled by?
Negative feedback
132
Describe the negative feedback system for thyroxine.
- The level of thyroxine levels in the blood is monitored by the brain.
- When thyroxine levels falls, the pituitary gland releases the hormone TSH into the blood.
- TSH triggers the thyroid gland to release more thyroxine into the blood.
- This increase in the levels of thyroxine is detected by the brain.
- This inhibits the production of TSH from the pituitary gland.
- As TSH levels fall, the thyroid gland releases less thyroxine.
- This is a negative feedback cycle.
^^no need to memorise.
133
What are plant hormones used for?
To coordinate and control the growth, responses to light and responses to gravity in plants.
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Phototropism meaning:
Gravitropism meaning:
Tropism meaning:
Phototropism - a plant's directional growth in response to light.
Gravitropism - a plant's directional growth in response to gravity.
Tropism - growth in a plant in response to a stimulus.
135
What is meant by auxins?
A group of plant hormones which control plant growth by promoting cell division and cell elongations.
136
Here is an experiment:
- Scientists shone light from one side of the shoot.
- The shoots grew in the direction of the light
- Scientists wondered if this process is controlled by hormones
- So they removed the tips of the shoots and shone light from that same side.
- The observed the the shoots did not grow in the direction of the light, what does this tell the scientists?
- Scientists then covered the tips of the shoots with foil to block out the light.
- The shoots did not grow towards the direction of the light.
- What does this tell scientists?
- Scientists used foil to cover the lower parts of the shoot
- The shoots grew towards the light as normal.
- What did this tell scientists?
1- Shoot tips produce a plant hormone which controls plant growth (auxin).
2 - The tips of plants are sensitive to light.
3 - The lower parts of the shoots are not sensitive to light.
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How do shoots use the hormone auxin to grow towards the light?
- Auxin is produced at the tips of the plant shoots, and at the shoots auxin triggers cell growth.
- Light causes auxin to move to the shaded/darker side of the shoot tip.
- This stimulates a faster rate of growth on that side of the plant because cell elongation and cell division is occurring.
- The shaded side now grows at a faster rate and bends towards the light.
138
How do shoots and hormones grow towards the gravity?
- Auxin is produced in the root.
- Gravity causes the auxin to concentrate on the lower side of the root.
- In roots, auxin inhibits cell growth.
- So the lower side grows more slowly than the upper side.
- This causes the roots to grow towards the force of gravity.
139
What is the role of Gibberellins:
Initiating seed germination
140
What is the role of Ethene in plants?
Controlling cell division and ripening fruits.
141
Uses of auxins
- Weed Killers
- Rooting powders
- Promoting growth in tissue culture
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Uses of Gibberellins
- End seed dormancy (force a seed to germinate earlier than it normally would)
- Promote flowering
- Increase fruit size.
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Uses of Ethene
- Used in the food industry to control ripening of fruit during storage and transport.
