T5: Homeostasis and Response Flashcards
What needs to happens to the conditions inside of your body?
The conditions inside of the body need to be kept steady even when the external environemnt change.
Why does the conditions inside the body need to be kept steady?
maintains optimal conditions for enzyme action and all cell functions.
What is homeostasis?
the regulation of the internal conditions of a cell or organism to maintain a stable internal environment in response to changes in both internal and external conditions.
What do automatic control systems do and what are they made up of?
regulate your internal environment; these include both nervous and hormonal communication.
In the human body, what do control systems maintain?
blood glucose concentration
body temperature
water levels.
What are the automatic control systems made up of?
- cells called receptors, which detect stimuli (changes in the environment)
- coordination centres (such as the brain, spinal cord and pancreas) that receive and process information from receptors.
- effectors, muscles or glands, which bring about responses which restore optimum levels. (contract or secrete hormones).
can receptors form larger organs?
receptors can form part of larger, complex organs e.g. the retina of the eye is covered in light receptor cells
How does the automatic control system keep your internal environment stable
your automatic control system keeps your internal environment stable using a mechanism called negative feedback.
What is negative feedback?
negative feedback- when the level of something (eg water or temperature) gets TOO HIGH or TOO LOW your body uses negative feedback to bring it back to normal.
How does negative feedback work?
1) Receptor detects a stimulus - level is too high/low
2) The coordination centre receives and processes the information, then organises a response
3) Effector produces a response, which counteracts the change and restores the optimum level - the level decreases/increases
how long do effectors produce responses for?
the effectors will just carry on producing a response for as long as they’re stimulated by the coordination centre. This might cause the opposite problem(making the level change too much- away from the ideal). Luckily the receptor detects if the level becomes too different and negative feedback starts again.
what does the nervous system allow humans to do?
The nervous system enables humans to react to their surroundings and to coordinate their behaviour.
What is the CNS and its function?
The CNS is a coordination centre- it receives information from the receptors and then coordinates a response( decides what to do about it).
-in vertebrates this consists of the brain and the spinal cord only. In mammals the CNS is connected to the body by sensory neurones.
How does the nervous system work?
Information from receptors passes along cells (neurones) as electrical impulses to the central nervous system (CNS). The CNS is the brain and spinal cord. The CNS coordinates the response of effectors which may be muscles contracting or glands secreting hormones.
stimulus → receptor → coordinator → effector → response
What are the sensory neurones?
The neurones that carry information as electrical impulses from the receptors to the CNS
What are the motor neurones?
The neurones that carry electrical impulses from the CNS to effectors.
What are effectors?
All your muscles and glands which respond to nervous impulses.
What is a synapse?
The connection between two neurones is called a synapse.
What happens at synapses?
- the nerve signals are transferred by chemicals which diffuse across the gap.
- these chemical then set off a new electrical signal in the next neurone.
What is a reflex?
A reflex is automatic, rapid responses to certain stimuli that don’t involve the conscious part of the brain- they reduce the chances of being injured.
Give 2 examples of reflexes.
1) If a bright light is shone into your eye, your pupils will automatically get smaller so less light gets into the eye, preventing your eye getting damaged.
2) If you get a shock your body release the hormone adrenaline automatically, it doesn’t wait for your body to decide that you are shocked.
What is a reflex arc?
The passage of information in a reflex (receptor to effector).
Where the do the neurones in the reflex arc go through?
the spinal cord or through an unconscious part of your brain.
What are the steps of the reflex arc?
1) When a stimulus is detected by a receptor, impulse is sent from the sensory neurone to the relay neurone in the CNS.
2) When the impulses reach a synapse between the sensory neurone and the relay neurone, they trigger chemicals to be released. These chemicals cause impulses to be sent along the relay neurone.
3) When the impulse reaches a synapse between the relay neurone and the motor neurone, chemicals are releases causing impulses to be send along the motor neurone,
4) The impulses travel along the motor neurone to the effector which if it is a muscle will contract and move away from stimulus or if it is a gland it will secrete hormones.
what are the differences in voluntary and reflex actions?
voluntary:
-learned
-Brain
-slowER, conscious
reflex:
-protection
-spinal cord (1st)
-quickER, automatic
What is reaction time?
the time it takes to respond to a stimulus; it is often less then one second.
Required practical: ruler test to investigate reaction time.
1)The person being tested should sit with their arm resting on the edge of a table- this is should stop them moving their arm up or down during the test
2)hold a ruler vertically between their thumb and forefinger. Make sure that the zero end of the ruler is level with their thumb and finger. Then let it go without giving any warning.
3) the person should try and catch the ruler as quickly as they can- as soon as they see it fall
4)reaction time is measured by the number on the ruler where it’s caught. The number should be read from the top of the thumb. The further down the ruler is caught (the higher the number) the slower their reaction time
5)repeat the test several times then calculate the mean distance that the ruler fell
6) the person being tested should then have a caffeinated drink (eg 300ml of cola). After 10 mins repeat steps 1 to 5
What are the control variables in the ruler test?
- same person being tested
- same hand to catch the ruler
- same height the ruler is dropped from
- the person should not have had any caffeine/anything that may affect reaction time, before the start of the experiment.
What can affect reacting time?
age, gender, drugs
How can reaction time be measure by a computer?
Simple computer tests such as a person having to click a mouse or press a key as soon as they see a stimulus on the screen e.g. a box changes colour.
Why do computers provide a more precise reaction time than the experiment with a ruler?
- They remove the possibility of human editor from the measurement.
- It also provides a more accurate measurement as a computer can measure milliseconds.
- Removes the possibility of the person being able to predict when to respond; using the ruler test the catcher may learn to anticipate the drop by reading the tester’s body language.
What does the brain do and what is it made up of?
The brain controls complex behaviour. It is made of billions of interconnected neurones and has different regions that carry out different functions.
What are the 4 different regions in the brain?
- cerebral cortex
- medulla
- spinal cord
- cerebellum
What does the cerebral cortex do and where is it located?
Front of the brain. It is the outer wrinkly part of the brain. It’s responsible for things like consciousness, intelligence, memory and language.
What does the medulla do and where is it located?
Front, next to the spinal cord. Controls unconscious activated like breathing and your heartbeat.
What does the cerebellum do and where is it located?
The back of the brain (leafy looking). It is responsible for muscle coordination.
How do scientists/ neurologists study the brain?
- studying patients with brain damage
- electrically stimulating the brain
- MRI scans
How does studying patients with brain damage allow scientists/ neurologists to study the brain
- if a small part of the brain has been damaged, the effect this has on the patient can tell you a lot about what the damaged part of the brain does.
- E.g. if an area at the back of the brain was damaged by a stroke and the patient went blind, you know that that area has something to do with vision.
How does electrically stimulating the brain allow scientists/ neurologists to study the brain?
the brain can be stimulated electrically by pushing a tiny electrode into the tissue and giving it a small zap of electricity. By observing what stimulating different parts of the brain does, it’s possible to get an idea of what those parts do
How does MRI scans of the brain allow scientists/ neurologists to study the brain?
a magnetic resonance imaging scanner is a big fancy tube like machine that can produce a very detailed picture of the brain’s structures. Scientists use it to find out what areas of the brain are active when people are doing things like listening to music or trying to recall a memory.
How has knowledge of the brain allowed for developments?
-knowledge of how the brain works has led to the development of treatments for disorders of the nervous system. For example, electrical stimulation of the brain can help reduce muscle tremors caused by nervous system disorders such as Parkinson’s disease.
What are the potential consequence of brain procedures?
-However, the brain is incredibly complex and delicate: the investigation of the brain function and any treatment of brain damage or disease is difficult. It also carries risks, such as physical damage to the brain or increased problems with brain function (e.g. difficulties with speech)
What is the sclera?
The tough, supporting wall of the eye.
What is the cornea?
The transparent, outer layer at the front of the eye. It refracts light into the eye.
What is the iris and what does it do?
the IRIS contains muscles that allow it to control the diameter of the pupil(the hole in the middle) and therefore how much light enters the eye.
What is the lens’s role?
the LENS focuses the light onto the RETINA (which contains receptors cells sensitive to light intensity and colour).
What controls the shape of the lens?
CILIARY MUSCLES and SUSPENSORY LIGAMENTS.
What does the optic nerve do?
the OPTIC NERVE carries impulses from the receptors on the retina to the brain.
What happens to the eye when there is bright light?
When light receptors in the eye detect very bright light, the reflex (iris reflex) is triggered and makes the pupil smaller.
The circular muscles contract and the radial muscles relax. This reduces the amount of light that can get into your eye.
What happens to the eye when there is dim light?
the radial muscles contract and the circular muscles relax, which makes the pupil wider.
What is accommodation?
the process of changing the shape of the lens to focus on near or distant objects
What happens when the eye is looking at near objects?
1)the ciliary muscles contract, which slackens/loosens the suspensory ligaments.
2)the lens becomes thicker/fat (more curved)
3)this increases the amount by which it refracts light
What happens when the eye is looking at distant objects?
1)the ciliary muscles relax, which allow the suspensory ligaments to be pulled tight
2)this makes the lens go thin (less curved)
3)So it refracts the light by a smaller amount (only slights refracts light rays)
What happens to your eye as you get older?
As you get older, your lens loses flexibility so it can’t easily spring back to a round shape. This means light can’t be focused well for near viewing, so older people will often have to use reading glasses.
What happens to people with long sighted people?
Long sighted (hyperopia) people are unable to focus on near objects as rays of light don’t focus on the retina
When does long sighted vision occur?
this occurs when the lens is the wrong shape and doesn’t refract (bend) the light enough or the eyeball is too short.
What happens to the images in long sighted vision?
the image of near objects are brought into focus behind the retina.
How can long sighted vision be fixed?
you can use glasses with a convex lens (a lens which curves outwards) to correct it. The lens refracts the light rays so they focus on the retina.
What happens to people with short sighted people?
short sighted (myopia) people are unable to focus on distant objects as rays of light do not focus on the retina.
When does short sighted vision occur?
this occurs when the lens is the wrong shape and refracts the light too much or the eyeball is too long.
What happens to the images in short sighted vision?
the images of distant objects are brought into focus in front of the retina.
How can short sighted vision be fixed?
you can use glasses with a concave lens (a lens which curves inwards) to correct it, so that the light rays focus on the retina.
What are 3 other treatments, other than glasses, for vision defects?
- contact lenses
- laser eye surgery
- replacement eye surgery
What do contact lenses do?
- contact lenses are thin lenses that sit on the surface of the eye and are shaped to compensate for the fault in focusing.
- They’re popular because they are lightweight and almost invisible.
- They’re also more convenient than glasses for activities like sports.
What are the 2 main types of lenses and which ones are better?
The two main types of contact lenses are hard lenses and soft lenses. Soft lenses are generally more comfortable but carry a higher risk of eye infections than higher lens.
What does laser surgery do?
bad eyesight can sometimes be corrected with laser eye surgery. A laser can be used to vaporise tissue, changing the shape of the cornea ( and so changing how strongly it refracts light into the eye). Slimming it down makes it less powerful and can improve short sight. Changing the shape so that it’s more powerful will improve long sight. The surgeon can precisely control how much tissue the laser takes off, completely correcting the vision. However, like all surgical procedures, there is a risk of complications, such as infection or the eye reacting in a way that makes your vision worse than before.
What does replacement lens surgery do?
sometimes longsightedness may be more effectively treated by replacing the lens of the eye (rather than altering the shape of the cornea with laser eye surgery). In replacement lens surgery, the natural lens of they eye is removed and an artificial lens, made of clear plastic, is inserted in its place. As it involves work inside the eye, replacing a lens carries higher risks than laser eye surgery, including possible damage to the retina (which could lead to loss of sight)
What does the body do in terms of temperature?
The body has to balance the amount of energy gained (e.g through respiration) and lost to keep the core body temperature constant. (at around 37C: the optimum temperature for enzymes in the body)
What does the thermoregulatory centre?
- there is a thermoregulatory centre in the brain, which contains receptors that are sensitive to the temperature of the blood flowing through the brain.
- the thermoregulatory centre also receives impulses from temperature receptors in the skin, giving information about skin temperature.
What happens when the body temperature becomes too high?
1)temperature receptors detect that core body temperature is too high
2)the thermoregulatory centre acts as a coordination centre- it receives information from the temperature receptors and triggers the effectors automatically
3)effectors e.g. sweat glands produce a response and counteract the change.
What happens when the body temperature becomes too low?
1)temperature receptors detect that core body temperature is too high
2)the thermoregulatory centre acts as a coordination centre- it receives information from the temperature receptors and triggers the effectors automatically
3)effectors e.g. muscles produce a response and counteract the change
How dod some effectors work?
some effects work antagonistically, one effectors heats and another cools, they’ll work at same time to achieve a very precise temperature. This mechanism allows a more sensitive response.
How does the body alter when it’s too hot?
1) SWEAT is produced by sweat glands and evaporates from the skin. This transfers energy from the skin to the environment.
2) the blood vessels supplying the skin dilate so more blood flows close to the surface of the skin. This is called VASODILATION. This helps transfer energy from the skin to the environment.
3)hair erector muscle relaxed so hairs don’t stand up so no trapped and so no insulation so cools down.
How does the body alter when it’s too cold?
1)hairs stand up to trap an insulating layer of air.
2)no sweat is produced.
3)blood vessels supplying skin capillaries constrict to close off the skin’s blood supply. This is called vasoconstriction.
4)when you’re cold you shiver too (your skeletal muscles contract automatically). This needs respiration which transfers some energy to warm the body.
What are hormones?
hormones are chemical messengers, made by the endocrine system, released directly into the blood. They are carried in the blood to other parts of the body, but only affect particular organs - called target organs. Hormones control things in organs and cells that need constant adjustment.
Where are hormones produced?
hormones are produced in and secreted by various glands called endocrine glands. Those glands make up your endocrine system. Hormones tend to have long lasting effects.
What does the pituitary gland do?
produces many hormones that regulate body conditions. It is something called the ‘master gland’ because these hormones act on other glands directing them to release hormones that bring about change
What does the ovaries do?
produce oestrogen which is involved in the menstrual cycle
What does the testes do?
produces testosterone which controls puberty and sperm production in males.
What does the thyroid do?
this produces thyroxine, which is involved in regulating things like the rate of metabolism, heart rate and temperature.
What does the adrenal gland do?
this produces adrenaline, which is used to prepare the body for a ‘fight or flight’ response
What does the pancreas do?
his produces insulin which is used to regulate the blood glucose level
What are the key features of nerves?
ery fast action, act for a short time, act on a very precise area. Use electrical impulses via neurones to carry messages (nervous system)
What are the key features of hormones?
slower action, act for a long time, act in a more general way. Use hormones secreted by glands via blood stream to carry messages (endocrine system)
How you can tell a response is a nervous response?
if the response is really quick it is probably nervous. Some information needs to be passed to effectors really quick (e.g. pain signals) so it’s no good using hormones to carry the message- they are too slow.
How you can tell a response is a hormonal response?
if a response last a long time, it’s probably hormonal. e.g. when you get a shock a hormone called adrenaline is released into the body. You can tell it’s hormonal response (even though it kicks in pretty quickly) because you fell a but wobbly for a while afterwards.
How does glucose get into the blood?
eating foods containing carbohydrates puts glucose into the blood from the gut.
How can glucose be removed from the blood and how can this rate be increased?
- the normal metabolism of cells removes glucose from the blood.
- vigorous exercise removes much more glucose from the blood.
What happens to excess glucose?
excess glucose can be stored as glycogen in the liver and in the muscles.
What must happen to the level of glucose in the blood?
the level of glucose in the blood must be kept steady. Changes are monitored and controlled by the pancreas, using the hormones insulin and glucagon, in a negative feedback cycle.
What happens when blood glucose levels are too high?
-insulin is secreted by pancreas
-this causes glucose to move from the blood into the cells
-in the liver and muscle cells excess glucose is converted to glycogen for storage
What happens when blood glucose levels are too low?
-glucagon is secreted by pancreas
-glucagon makes liver turn glycogen to be converted into glucose and released into the blood
What is diabetes?
diabetes is a condition that affects your ability to control your blood sugar level.
What is type 1 diabetes?
Type 1 diabetes is where the pancreas doesn’t produce sufficient insulin. This means a person’s blood glucose level can rise to a level that can kill them.
How can type 1 diabetes be treated?
- People with type 1 diabetes need insulin therapy- several injections of insulin through out the day, most likely at meal times.
- This makes sure that glucose is removed from the blood quickly once the food has been digested, stopping the level getting too high. It’s very effective treatment. The amount of insulting that needs to be injected depends on the person’s diet and how active they are.
What is type 2 diabetes?
Type 2 diabetes is where a person’s body becomes resistant to their own insulin (they still produce insulin but their body cells don’t respond properly to the hormone).
What are the risks of type 2 diabetes?
This can also cause a person’s blood sugar level to rise to a dangerous level. Being overweight can increase your chance of developing type 2 diabetes, as obesity is a major risk factor in the development of the disease.
How can type 2 diabetes be controlled?
Type 2 diabetes can be controlled by earring a carbohydrate controlled diet and getting regular exercise.
What is filteration? ( in terms of the kidney)
the kidneys make urine by taking waste products out of your blood. Substances are filtered out of the blood as it passes through the kidneys. The substances that are removed from the body in urine include: urea, ions and water
What is selective reabsorption?
useful substances like glucose, some ions and the right amount of water are then absorbed back into the blood
What are the substances in urine?
urea, ions and water.
What is urea?
1)proteins (and the amino acids that they are broken down into) can’t be stored by the body- so any excess amino acids are converted into fats and carbohydrates, which can’t be stored. This occurs in the liver and involves a process called deamination.
2)ammonia is produced as a waste product from this process.
3)ammonia is toxic so it’s converted to urea in the liver. Urea is then transported to the kidneys where it is filtered out of the blood and excreted from the body in urine.
What happens to some urea?
-some small unregulated amount of urea is also lost from the skin in sweat
What are the ions in the urine?
ions such as sodium are taken into the body in food, and then absorbed into the blood.
What could happen if the ion (or water) content of the body is wrong?
this could upset the balance between ions and water, meaning too much or too little water is drawn into cells by osmosis. Having the wrong amount of water can damage cells or mean they don’t walk as well as normal.
What happens to some of the ions?
some ions are lost in sweat. However this amount is not regulated so the right balance of ions in the body must be maintained by the kidneys. The right amount of ions is reabsorbed into the blood after filtration and the rest is removed from the body in urine
What happens to the water in the body?
1)the body has to constantly balance the water coming in against the water going out.
2)we lose water from the skin in wear and from the lungs during exhalation/breathing out.
3)we can’t control how much we lose in these ways, so the amount of water os balanced by the amount we consume and the amount removed by the kidney in urine.
What is the concentration of urine controlled by?
by a hormone called anti-diuretic hormone (ADH). This is released into the bloodstream by the pituitary gland.
What does the brain monitor?
The brain monitors the water content of the blood and instructs the pituitary gland to release ADH into the blood according to how much is needed.
What is the whole process of water regulation controlled by?
The whole process of water content regulation is controlled by negative feedback. This means that if the water content gets too high or too low a mechanism will be triggered that brings it back to normal.
what happens if the water content is too high?
1)receptor in the brain detects that the water content is too high.
2)the coordination centre in the brain receives the information and coordinates a response.
3)the pituitary gland release less ADH so less water is reabsorbed from the kidney tubules. The water content decreases.
what happens if the water content is too low?
1)receptor in the brain detects that the water content is too low.
2)the coordination centre in the brain receives the information and coordinates a response.
3)the pituitary gland release more ADH so more water is reabsorbed from the kidney tubules. The water content increases.
What happens with kidney failure?
If your kidneys don’t work properly, waste substances build up in the body and you lose your ability to control the levels of ions and water in your body. Eventually, this results in death.
What can be used for people with kidney failure?
- dialysis treatment (where machines do the job of kidneys)
- kidney treatment
Why does dialysis have to be done regularly?
Dialysis has to be done regularly to keep the concentrations of dissolved substances in the blood at normal levels, and the remove waste substances.
What happens in a dialysis machine?
- In a dialysis machine the person’s blood flows between partially permeable membranes, surrounded by dialysis fluid. It’s permeable to things like ions and water substances, but not to big molecules like proteins (just like the membranes in the kidney).
What does the dialysis fluid have the same concentration as and why is this important?
- same concentration of dissolved ions and glucose as healthy blood.
- this means that useful dissolved ions and glucose won’t be lost from the blood during dialysis.
- only waste substances (e.g. urea) and the excess ions and water diffuse across the barrier.
What are the cons of dialysis?
- many patients with kidney failure have to have a dialysis session three times a week. Each session takes 3 to 4 hours.
- dialysis can cause blood clots or infections.
- expensive for the NHS to run
- not a pleasant experience
What are the pros of dialysis?
Can buy a patient’s with kidney failure valuable time until a donor organ if found.
What is the only cure for kidney failure at the moment?
to have a kidney transplant
Where do the kidneys for transplants come from?
- healthy kidneys are usually transplanted from people who have died suddenly.
- The person who died has to be on the organ donor register or carry a donor card (provided their relatives agree too)
- Kidneys can be transplanted from people who are still alive (as we all have 2 of them) but there is a small risk to the person donating the kidney.
What are the risks of a kidney transplant for the patient?
There is a risk that the donor kidney can be rejected by the patient’s immune system. The patient can be treated with drugs to prevent this but it can still happen.
What are the pros and cons of transplants?
-transplants are cheaper (in the long run) than dialysis and they can put an end to the hours patients have to spend on dialysis.
- long waiting lists for kidneys.
What happens at puberty?
your body starts releasing sex hormones that trigger off secondary sexual characteristics (such as the development of facial hair in men and breasts in women) snd causes eggs to mature in women.
What is the main reproductive hormone is men and where is it made?
- testosterone
- produced by the testes and stimulates sperm production
What is the main reproductive hormone is women and where is it made?
- oestrogen
- produced by the ovaries
- as well as bringing about physical changes, oestrogen is also involved in the menstrual cycle.
What happens during the 4 stages of the menstrual cycle?
Stage 1: day 1- menstruation starts. The uterus lining breaks down for about 4 days.
Stage 2: The uterus lining builds up again, from day 4 to day 14, into a thick spongy layer full of blood vessels, ready to receive a fertilised egg.
Stage 3: An egg develops and is released from the ovary at day 14 - this is called ovulation.
Stage 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.
What are the four hormones that controlled the menstrual cycle?
Oestrogen, progesterone, FSH (follicle stimulating hormone), LH (luteinising hormone)
What is the role of oestrogen in the menstrual cycle?
1) produced in the ovaries
2) causes the lining of the uterus to grow
3) stimulates the release of LH (which causes the release of an egg) and inhibits releases of FSH
What is the role of progesterone in the menstrual cycle?
1) Produced in the ovaries by the remains of the follicle after ovulation.
2) Maintains the lining of the uterus during the second half of the cycle.
When the level of progesterone falls, the lining breaks down.
3) Inhibits the release of LH and FSH.
What is the role of FSH (follicle stimulating hormone) in the menstrual cycle?
1) produced in the pituitary gland.
2)causes an egg to mature in one of the ovaries in a structure called a follicle.
3)stimulates the ovaries to produce oestrogen.
What is the role of LH (luteinising hormone) in the menstrual cycle?
1)produced by the pituitary gland.
2)stimulates the releases of an egg at day 14 (ovulation)
Which 2 hormones can be used to reduce fertility?
oestrogen and progesterone
How does can oestrogen be used to reduce fertility?
- Oestrogen can be taken to prevent the release of an egg
- this seems strange as naturally oestrogen stimulates the realise of eggs but if oestrogen is taken every day to keep the level of it permanently high, it inhibits the production of FSH and after a while egg development and production stop and stay stopped.
How does can progesterone be used to reduce fertility?
- Progesterone also reduces fertility e.g. by stimulating the production of thick mucus which prevents any sperm getting through and reaching an egg.
What are the 6 types of contraception?
- the pill
- progesterone only pill
- contraceptive patch
- contraceptive implant
- contraceptive injection
- IUD
What is the pill and what is the disadvantages?
is an oral contraceptive contains oestrogen progesterone (known as the combined contraceptive pill).
It is over 99% effective but it can cause side effects like headaches and nausea and it doesn’t protect against sexually transmitted diseases.
What is the progesterone pill?
it has fewer side effects than the pill and is just as effective.
What is the contraceptive patch?
contains oestrogen and progesterone. It is a small 5x5 patch stuck to the skin. Each patch lasts a week.
What is the contraceptive implant?
- inserted under the skin of the arm.
- It releases continuous amount of progesterone which stops ovaries realising eggs, makes it hard for sperm to swim to the egg and stops and fertilised egg implanting in the uterus.
- An implant can last 3 years.
What is a contraceptive injection?
contains progesterone, each does lasts 2-3months.
What is an intrauterine device (IUD)?
T shaped device that’s inserted into the uterus to kill sperm and prevent implantation of a fertilised egg.
2 main types- plastic IUDs release progesterone and copper IUDs that prevent the sperm surviving in the uterus.
What are barrier methods?
Non hormonal forms of contraception are designed to stop the term from getting to the egg.
What are the 3 barrier methods of contraception?
- condoms
- diaphragm
- spermicide
What are condoms and what are their main advantage?
- condoms are worn over the penis during intercourse to prevent the sperm entering the vagina.
- There are also female condoms that are worn inside the vagina.
- Condoms are the only form of contraception that will protect against sexually transmitted diseases.
What is a diaphragm?
a diaphragm is a shallow plastic cup that fits over the cervix (the enter ace the the uterus) to form a barrier. It has to be used worn a spermicide ( a substance that disables/kills the sperm)
What is spermicide?
spermicide can be used alone as a form of contraception but it is not as effective (only 70-80%)
What is sterilisation?
- Sterilisation involves cutting or tying the fallopian tubes (which connect the ovaries to the uterus) in a female, or the sperm duct (the tube between the testes and penis) in a male.
- This is a permanent procedure.
- However there is a very small chance that the tubes can rejoin.
What are natural methods?
- pregnancy may be avoided by finding out when in the menstrual cycle the woman is most fertile and avoiding sexual intercourse on those days.
- It’s popular with people who think that hormonal and barrier methods are unnatural, but it’s not very effective.
What is abstinence?
the only way to be completely sure that sperm and egg don’t meet is to not have intercourse
Why can some women not get pregnant?
some women have levels of FSH (follicle stimulating hormone) that are too low to cause their eggs to mature. This means that no eggs are released and the women can’t get pregnant.
What can be given to women to increase fertility?
the hormones FSH and LH can be given to to women in a fertility drug to stimulate ovulation.
What are the pros of using hormones to increase fertility?
it helps a lot of women to get pregnant when previously they couldn’t
What are the cons of using hormones to increase fertility?
- it doesn’t always work, some women may have to do it many times which
can be expensive.
-too many eggs could be stimulated, resulting in unexpected multiple
pregnancies (twins, triplets, etc.).
What are the first steps of IVF?
1) IVF involves collecting eggs from the woman’s ovaries and fertilising them in a lab using the man’s sperm.
2)IVF treatment can also involve a technique called intra-cytoplasmic sperm injections (ICSI) where the sperm is injected directly into an egg. It’s useful if the man has a very low sperm count.
In IVF (in vitro fertilisation) what happens to the fertilised eggs?
- The fertilised eggs are then grown into embryos in a laboratory incubator.
-Once the embryos are tiny balls of cells, one or two of them are transferred to the woman’s uterus to improve the chance of pregnancy.
In IVF, what happens before eggs are collected?
FSH and LH are given before egg collection to stimulate several eggs to mature (so more than one egg can be collected.
What are the pros of IVF?
can give an infertile couple a child
What are the cons of IVF?
- multiple births can happen if more than one embryo grows into a baby- this is risk for the mother and babies as there’s a higher risk of miscarriage, stillbirth
- the success rate of IVF is low- average success rate in UK is 26%. This makes the procedure very emotionally and physically stressful.
- some women have strong reactions to the hormones- e.g. abdominal pain, vomiting, dehydration
How has advances in microscope technology enabled IVF treatment to develop?
-specialised micro tools have been developed to use on the eggs and sperm under the microscope
-they’re also used to remove single cells from the embryo for genetic testing
How has advances in microscope technology recently enabled IVF treatment to develop?
-the development of of time lapse imaging (using a microscope and camera built into the incubator) means that the growth of they embryos can be continuously monitored to help identify those that are more likely to result in a successful pregnancy.
Why are some people against IVF?
-often results in unused embryos that we eventually destroyed: some people think this is unethical because each embryo is potential human life
-the genetic testing of embryos before implantation also raises ethical issues as some people think it could lead to the selection of preferred characteristics, such as gender or eye colour
what is adrenaline?
adrenaline is a hormone released by the adrenal glands, which are just above the kidneys.
When is adrenaline released?
adrenaline is released in response to stressful or scary situations- your brain detects fear or stress and sends nervous impulses to the adrenal glands which respond by secreting adrenaline.
What does adrenaline get the body ready for and how ?
it gets the body ready for ‘fight or flight’ by triggering mechanisms that increase the supply of oxygen and glucose to cells in the brain and muscles. For example, adrenaline increases heart rate.
How are hormones levels controlled?
Your body can control the levels of hormones in the blood using negative feedback systems.
What is negative feedback?
When the body detects that the level of a substance has gone above or below normal level, it triggers a response to bring the level back to normal again. An example of this is how thyroxine levels are controlled by negative feedback.
What is thyroxine and what is it made from?
thyroxine is a hormone released but the thyroid gland, which is in the neck.
Thyroxine is made in the thyroid gland from iodine and amino acids.
What is the role of thyroxine?
it plays an important part in regulating the basal metabolic rate- the speed at which chemical reactions in the body occur while the body is at rest. Thyroxine is also important for loads of processes in the body such as stimulating protein synthesis for growth and development
When is thyroxine released?
thyroxine is released in response to thyroid stimulating hormone TSH which is released from the pituitary gland.
How does negative feedback control thyroxine levels?
a negative feedback system keeps the amount of thyroxine in the blood at the right level- when the level of thyroxine in the blood is higher than normal, the secretion of TSH from the pituitary gland is inhibited (stopped).
This reduces the amount of thyroxine released from the thyroid gland, so the level in the blood falls back towards normal.
What is auxin?
Auxin is a plant hormone that controls growth near the tips of shoots and roots.
What do plant hormones do?
Plant hormones make sure they grow in the right direction.
What does auxin do?
It controls the growth of a plant in response to light (phototropism) and gravity (gravitropism or geotropism).
Where is auxin produced?
Auxin is produced in the tips and moves backwards to stimulate the cell elongation (enlargement) process which occurs in the cells just behind the tips.
What happens if the tip of a short is removed?
If the tip of a shoot is removed, no auxin is available and the shoot may stop growing.
What does extra auxin do?
Extra auxin promotes growth in the shoot but inhibits growth in the root- producing the desired result.
What happens when a shoot grows towards light?
1) when a shoot tip is exposed to light, more auxin accumulates on the side that’s in the shade than the side that’s in the light.
2) this makes the cells grow (elongate) faster in the shaded side, so the shoot bends towards the light.
What happens when a shoot grows away from gravity and roots grow towards gravity?
1)when a shoot is growing sideways, gravity produces an unequal distribution of auxin in the tip, with more auxin on the lower side
2)this causes the lower side to grow faster bending the shoot upwards
3)a root growing sideways will also have more auxin on its lower sides
4)but in a root the extra auxin inhibits growth. This means the cells on top elongate faster and the root bends downwards.
How can you investigate the effect of light on the growth of newly germinated seeds (cress seeds)?
1) put 10 cress seeds into 3 different Petri dishes each lined with moist filter paper. (Remember to label your dishes e.g. A,B,C)
2) shine a light onto one of the dishes from above and two of the dishes from different directions
3) leave your cress seeds alone for one week until you can observe their responses- you’ll find that the seedlings grow towards the light
4)you’ll know that the growth response of the cress seed is due to light only, if you control all other variables
What are the control variables and how can they be controlled?
NUMBER OF SEEDS: use the same number if seeds in each dish
TYPE OF SEED: use seeds that all come from the same packet
TEMPERATURE: keep your petri dish in a place where the temperature stable (i.e. away from heat sources and draughts)
WATER: use a measuring cylinder to add the same amount of water
LIGHT INTENSITY: keep the distance between the bulb and dish the same
How can you investigate the effect of gravity on the growth of newly germinated seeds (cress seeds) ?
1) place 4 seedlings on damp cotton wool in a Petri dish, each with their roots pointing in a different direction, and store the Petri dish vertically for a few days in the dark
2)you should find that the roots of each seedling grow downwards.
What are the 3 uses of auxin?
- killing weeds
- growing from cuttings with rooting powder
- growing cells in tissue culture
How is auxin used to kill weeds?
most weeds growing in fields of crops or in a lawn are broad leaved, in contrast to grasses and cereals which have very narrow leaves. Selective weed killers have been developed using auxins which only affect the broad leaved plants. They totally disrupt their normal growth patterns, which soon kills them, whilst leaving the grass and crops untouched
How is auxin used to grow from cuttings with rooting powder?
a cutting part of a plant that has been cut off it, like the end of a branch with a few leaves in it. Normally, if you stick cuttings in the soil they won’t grow, but is you add rooting power, which contains auxins, they will produce roots rapidly and start growing as new plants. This enables growers to produce lots of clones of a really good plant very quickly.
How is auxin used to grow cells in tissues culture?
tissue culture can be used to grow clones of a plant from a few of its cells. To do this hormones such as auxins need to be added to the growth medium (along with nutrients) to stimulate the cells to divide to form both roots and shoots.
What is gibberellin and what does it do?
- gibberellin is another type of plant growth hormones.
- it stimulates seed germination, stem growth and flowering.
What are the 3 uses of gibberellin?
- controlling dormancy
- inducing flowering
- growing larger fruit
How is gibberellin used to control dormancy?
ots of seeds won’t germinate until they’ve been through certain conditions (eve a period of cold). This is called dormancy. Seeds can be treated with gibberellin to alter dormancy and make them germinate at times of year that they wouldn’t normally. It also helps to make sure all seeds in a batch germinate at the same time
How is gibberellin used to induce flowering?
some plants require certain conditions to flower. If plants are treated with gibberellin they will flower without any changes in their environment. Gibberellin can also be used to grow bigger flowers
How is gibberellin used to grow larger fruit?
seedless varieties of fruit of often don’t grow as large as seeded fruit but if gibberellin is added to these fruits they will grow larger to match the normal types.
What is ethene and what does it do?
- ethene is a gas produced by aging parts of a plant.
- It influences the growth of the plant by controlling cell division.
- It also stimulates enzymes that cause fruits to ripen.
What can ethene be used commercially?
commercially, it can be used to speed up the ripening of fruits- either while they are still on the plant or during transport to the shops
How can ethene be used to speed up the ripening of fruits?
this means that fruit can be picked while it’s still unripe (and therefore firmer and less easily damaged). The gas is then added to the fruit on the way to the supermarket so that it will be perfect just as it reaches the shelves.
How can ripening be delayed?
ripening can also be delayed while the fruit is in storage by adding chemicals that block ethene’s effect on the fruit or reduce the amount of ethene that the fruit can produce. Alternatively, some chemicals can be used that react with ethene to remove it from the air
