B11 Flashcards
Hormonal coordination
What is the endocrine system ?
an organ system comprised of glands that secrete hormones (chemical messengers) in order to prompt a specific response from the body
Describe the effects of hormones in comparison to those of the nervous system
- hormonal effects last longer in the body on average
[] HOWEVER they take more time to actually take effect, whilst the nervous system can prompt reactions in only seconds - some hormones act and dissipate relatively fast, like insulin and adrenaline, whilst others like growth and sex hormones last in the body longer and take longer to take effect
What is ADH ?
anti-diuretic hormone; controls water reabsorption in the kidneys by increasing the permeability of tubules in the kidneys
What is FSH ?
- Follicle Stimulating Hormone
- stimulates the ovaries to produce the sex hormone oestrogen in females
What is TSH ?
- Thyroid Stimulating Hormone
- stimulates the thyroid gland to secrete thyroxine, the hormone that helps to control the rate of metabolism
What are the roles of the hormones secreted by the pituitary gland in the brain ?
- controls growth in children
[] human growth hormone (HGH) - stimulates thyroid gland to make thyroxine
[] thyroid stimulating gland (TSH) - stimulates ovaries to produce and release eggs, as well as oestrogen (hormone)
- stimulates testes to produce sperm as well as testosterone (hormone)
What are the roles of the hormone secreted by the thyroid gland ?
- produces thyroxine
[] controls metabolic rate of the body
What are the roles of the hormone secreted by the adrenal glands ?
- secretes adrenalin in response to fear/anxiety/stress
[] triggers fight or flight response in body:
-> breathing rate quickens
-> heart rate increases
-> glycogen stores converted into glucose for respiration
-> pupils dilate to let in more light
-> blood supply diverted from digestive system to muscles
-> mental awareness increases
What are the roles of the hormone secreted by the ovaries ?
- oestrogen
[] controls development of female secondary sexual characteristics
[] stimulates thickening and maintenance of uterine lining
[] inhibits FSH
[] stimulates the release of LH
What are the roles of the hormone secreted by the testes ?
- testosterone
[] controls development of male secondary sexual characteristics as well as the production of sperm
What are the roles of the hormones secreted by the pancreas ?
- secretes insulin
[] controls blood glucose levels through prompting cells to take in glucose from the blood - glucagon
[] converts glycogen back into glucose to be used in cellular respiration
What is a hormone ?
- chemical messenger (either a protein or starch-based; most are proteins)
- travel through the bloodstream
- are secreted in response to an external or internal stimulus and prompt a response from an effector (sometimes another gland, other times can be cells etc.)
Describe how the pancreas controls blood glucose levels through the negative feedback loop involving insulin and glucagon
if blood glucose levels are too high:
-> uncontrolled increase in blood glucose concentration after a meal
-> pancreas releases insulin in response
-> insulin prompts increased intake of glucose by body cells for respiration (often why one feels warmer after eating)
[] excess glucose is converted to glycogen in the liver - if glycogen stores are full, it is instead stored as lipids/fat
-> blood glucose levels fall to normal levels
if blood glucose levels are too low:
-> glucagon released by the pancreas
-> glycogen stores are converted into glucose for cellular respiration
-> amino acids and fats broken down
-> blood glucose levels rise to normal levels
What causes type 1 diabetes, and what are its effects ?
- pancreatic cells being unable to produce (sufficient amounts of) insulin
- effects:
[] blood glucose levels are uncontrolled and so surge after a meal
[] kidney resorts to excreting glucose in urine
[] increased production of urine means one feels thirsty all the time; water levels in the body are dangerously off-balance
[] glucose cannot get into body cells without insulin, so no respiration and a lack of energy, causing fatigue
[] fats and proteins are broken down instead of glucose for fuel, making one lose weight
What causes type 2 diabetes, and what are its effects ?
- type of diabetes that grows more common with age, poor diet, obesity and lack of exercise
[] pancreas still makes insulin (perhaps less than needed by the body), but the body cells stop responding to it properly - effects:
[] without proper reactions to insulin, glucose cannot be taken into body cells for respiration (causes fatigue)
[] fats and proteins are broken down instead (patient loses weight)
[] glucose is excreted via the urine (increased urine production means increased loss of water - patient feels thirsty constantly)
Describe how type 1 diabetes is TREATED
- insulin injections into the blood before meals (would simply be digested if ingested instead)
- reducing/carefully managing the amount of carbohydrates eaten so as not to cause spikes in blood sugar that are hard to control without sufficient insulin
[] means that people have to carefully plan when they exercise, as need enough glucose for respiration
MEANS THAT PEOPLE WILL HAVE TO INJECT INSULIN EVERY DAY OF THEIR LIVES
[] costly if healthcare in a country isn’t free
[] risk of air embolisms when doing injections (fatal in some cases)
[] inconvenient
[] for those with low pain tolerances or fear of needles, can be a frequent struggle
[] however, there are also patches that inject the insulin for you, instead of having to do the injection with a manual needle that can help with this
Describe how type 1 diabetes is CURED and the associated pros/cons
- pancreas transplant
[] risk of general anaesthesia
[] have to take immunosuppressants, so exchange one medicine for another
[] very few donor pancreases available in the UK, so long waiting lists
[] immunosuppressants can be ingested instead of injected, and a transplant allows one to live a healthy life without too much planning going into mealtimes, exercise etc. - transplants of pancreatic cells
[] limited success so far
[] risk of general anaesthesia
[] less risk of rejection, so immunosuppressants not really needed - some cases of adult stem cell cloning have succeeded in curing type 1 diabetes
[] no risk of rejection
Describe how type 2 diabetes is TREATED
- developing a healthier lifestyle through:
[] losing weight
[] controlling intake of carbohydrates and sugars
[] exercising regularly - IF THE ABOVE DOESN’T WORK, there are drugs available that either increase insulin production, increase reactivity of body cells to insulin or reduce the amount of glucose absorbed from food in the small intestine
Describe the negative feedback loop controlling metabolism in the body
-> pituitary gland detects that thyroxine levels in blood are too low through sensors in the brain
-> pituitary gland releases TSH
-> TSH stimulates thyroxine production in the thyroid gland
-> thyroxine levels rise
-> sensors in the brain signal the pituitary gland to stop producing TSH so thyroxine levels fall again
List the female secondary sexual characteristics
- growth of genitals and darkening of surrounding skin
- fat redistribution to breasts, buttocks and hips
- brain matures
- growth of pubic and underarm hair
- growth spurt
- beginning of menstruation
[] uterus grows
[] eggs begin to mature and release once a month/menstrual cycle
What is LH ?
luteinising hormone; stimulates release of eggs (ovulation)
What role do oestrogen and progesterone play in the menstrual cycle ?
- oestrogen thickens the uterine lining
- progesterone is responsible for maintaining the lining
- oestrogen inhibits release of FSH and stimulates release of LH
- progesterone inhibits the release of FSH AND LH
- progesterone helps to maintain pregnancy if an egg is fertilised and implants into the uterine lining
What is menopause and how is fertility affected leading up to it ?
- menopause = when the supply of eggs in the ovaries are used up completely, and no more menstrual cycles can occur
- fertility decreases leading up to menopause, and risk of having children with genetic disease or defects increases
Describe the secondary sexual characteristics of males
- genitals grow and skin darkens
- shoulders and chest broaden due to increase in muscle mass in those areas
- brain matures
- testes grow and become active, producing sperm throughout life
- pubic, facial and underarm hair grow
- growth spurt
- larynx grows and voice breaks, deepening
How long is the average menstrual cycle ?
28 days - varies from individual to individual
Describe the main stages of the menstrual cycle and the interaction of hormones over its course (and at which days they occur)
- stage 1: period
[] days 0 - 4
[] uterine lining breaks down and is passed out of the body as blood through the vaginal canal
[] during this time, progesterone is produced to inhibit LH (ovulation stimulant) and FSH (egg maturation stimulant)
[] just after period, FSH levels spike to produce oestrogen - stage 2: lining thickens again
[] days 4 - 14
[] role is to prepare uterus for implanting of a fertilised egg
[] progesterone (in smaller quantities) and oestrogen in large quantities produced to thicken and maintain the uterine lining
[] FSH is released to mature eggs, ready for ovulation - stage 3: ovulation
[] day 15
[] egg travels out of oviduct and into the uterus where it waits to be fertilised
[] LH is released to stimulate ovulation - stage 4: maintenance of uterine lining in case of fertilisation
[] days 15 - 28
[] if no egg is fertilised and implants, the cycle begins again with the period and passing out the unfertilised egg
[] progesterone produced to maintain lining and inhibit LH and FSH production until the after the next period
[] drop in progesterone levels allows next cycle to start
Where is progesterone produced ?
empty follicle in ovaries after ovulation
What are the 6 main methods/categories of contraception ?
- hormonal contraception
- chemical contraception (spermicides)
- abstinence
- surgical methods
- barrier methods
- IUD (intrauterine device)
What is abstinence, why/how is it used and how effective is it as a contraceptive ?
- abstinence is simply not having sex at certain points during the menstrual cycle to avoid times of high fertility
- mostly used by religious people whose beliefs forbid artificial contraception
- also known as the rhythm method
- very unreliable and ineffective, especially if one has an irregular menstrual cycle
[] the use of ovulation indicators help to make the method slightly more reliable
What is a vasectomy, why/how is it used and how effective is it as a contraceptive ?
- surgical method of contraception
- the sperm ducts are cut and tied to prevent release of sperm
- 100% effective, no risk of human error
[] however, is permanent and cannot be reversed
[] no anaesthesia needed
What is tubal ligation, why/how is it used and how effective is it as a contraceptive ?
- surgical method of contraception
- oviducts are cut and tied to prevent release of eggs
[] risk of anaesthesia for the procedure - 100% effective, no risk of human error, but is PERMANENT
What is an IUD, why/how is it used and how effective is it as a contraceptive ?
- intrauterine device
- inserted into the uterus by a doctor
[] last 3-5 years, though can be removed at any time by a doctor - some contain/are made of copper, which prevents any early embryos from implanting in the uterine lining
- some slowly release progesterone to prevent build-up of uterine lining and thicken cervical mucus
- very effective (almost 100%)
[] may cause problems with one’s period or cause infection
What is a spermicide, and how effective is it as a contraceptive ?
- chemical contraception method
- readily available, so are convenient, HOWEVER are relatively ineffective as a contraceptive
What are the main barrier methods, why/how are they used and how effective are they as contraceptives ?
- work by preventing sperm reaching and fertilising an egg
- condom
[] latex sheath placed over the penis
[] catches sperm once ejaculated
[] no side effects, no medical advice or prescription needed
[] offer some protection from STDs
[] may get damaged during intercourse and let sperm through - diaphragm
[] thin rubber diaphragm placed over cervix before intercourse
[] no side effects
[] must initially be fitted by a doctor
[] if not positioned correctly, sperm can get through
[] provides some protection from STDs - barrier methods are on the whole effective as contraception if used properly, though there is a risk of human error and work better in conjunction with spermicides or hormonal contraception
What is the mixed pill, why/how is it used and how effective is it as a contraceptive ?
- hormonal contraceptive
- contains low doses of oestrogen and progesterone to inhibit production and release of FSH by the pituitary gland so no eggs mature
- also stop lining developing to prevent implantation
- make cervical mucus thicker to prevent sperm getting through
- effective but has some side effects like high blood pressure, risk of thrombosis and breast cancer
- taken orally; convenient
[] risk of human error if forget to take the pill
What is the progesterone-only pill, why/how is it used and how effective is it as a contraceptive ?
- taken orally
[] has to be taken very regularly and has risk of human error which affects effectiveness - hormonal contraceptive
What are the three alternate hormonal methods to the pills ?
- contraceptive implants
[] release progesterone slowly and are extremely effective - progesterone injections
[] last only 12 weeks so risk of human error in terms of forgetting to reinject, but effective - contraceptive patches
[] mix of oestrogen and progesterone released and absorbed into bloodstream via skin
What are the three main causes of infertility (other than naturally being infertile) ?
- age
- eating disorders like anorexia
- obesity
Describe the fertility treatment for people who do not ovulate (frequently) and thus are infertile
- prescribed fertility drugs containing FSH and/or LH to stimulate maturation of and release of eggs
[] a dose that is too high can often result in unwanted high levels of fertility, so dosage must be carefully controlled - works very effectively for women whose cause of infertility lies in the improper release and production of FSH and/or LH
When is IVF (in-vitro fertilisation) used to treat infertility ?
- no clear cause of infertility
- oviducts have been damaged/blocked
- donor egg has to be used
- problems with sperm count in semen
How is IVF carried out ?
- female patient is given FSH and LH drugs to stimulate maturation of many eggs and then to bring them to the point of ovulation
- mature eggs are collected from the ovary just before their release
[] fertilised with the male’s sperm in a laboratory - fertilised eggs kept in special solution in warm environment to simulate the uterus and help the egg grow into an embryo
- embryo(s) are inserted into the uterus where they implant in the uterine lining if successful
Give the advantages of IVF treatment
- gives parents who would otherwise be infertile the chance to have their own children
- spare mature eggs collected during IVF treatment can be stored for later use if decided to get pregnant again, or can be donated to scientific embryonic stem cell research
Give the disadvantages of IVF treatment
- IVF is expensive for society (if provided by the NHS) and for people
[] IVF success rates are low, meaning multiple rounds of treatment are usually needed, costing thousands of pounds
[] equipment is highly specialised and costs a lot of money - success rates of IVF are low
- failures cause distress in parents in the event of miscarriage
- fertility drugs used during IVF can have negative impacts on the mother’s health
- IVF increases the chance of multiple pregnancy (1 in 5 IVF, vs 1 in 80 naturally)
[] thus increases likelihood of stillbirth and premature birth, as well as endangering the mother’s health
[] babies born very prematurely cost a lot of money to keep alive and may develop severe and permanent disabilities - unused eggs may cause ethical problems if unwanted, the couple break up etc.
Why are gravitropisms and phototropisms important to plants’ development ?
they enable the plant to grow right side up and access the correct nutrients/conditions needed for different parts of the plant regardless of which way up the seed falls or is planted
What is phototropism and how does it work ?
- response of a plant to one-sided or uneven light
- how it works:
-> one-sided/uneven light hits the shoot
-> auxin moves from the area in the light to the area in the shadow
-> plant cells respond to the movement of auxin, and are elongated by the auxin
-> uneven elongation/growth of cells due to the uneven distribution of auxin causes the shoot to bend towards the light whilst growing
[] USEFUL FOR PHOTOSYNTHESIS
What is gravitropism and how does it work ?
- response of a plant to uneven distribution of auxin due to gravity
- how it works:
[] roots and shoots respond differently to auxin: shoots grow on the side where the auxin is present, whilst roots grow on the side where auxin isn’t present
[] if a seed is germinated on its side and both the beginning of the roots and shoots grow outwards horizontally, the auxin in the plant will sink to the bottom of these roots/shoots
[] roots grow away from auxin and so are directed deeper into the ground
[] shoots grow towards auxin and so bend upwards out of the ground
[] once the roots/shoots are straight(er) up/down, auxin levels even out and the plant grows normally downwards or upwards until another tropism like hydro or phototropism comes into play
Describe the method of a practical investigating the effects of light on newly germinated seedlings
- place cotton wool in 3 separate petri dishes and soak with EQUAL VOLUMES of water
- place ten (mustard/the same type of) seeds in each dish
- leave dishes in a warm place ALTOGETHER, SO TEMPERATURE IS THE SAME FOR ALL 3 and allow to germinate
[] water seeds daily with the same volume of water - after seeds have germinated, make sure each of the three dishes have the same number of seedlings
- measure and record the heights of the seedlings in each of the dishes, holding the stems straight against the ruler to get an accurate reading
- place one dish in full sunlight on a very bright windowsill for example, place one in complete darkness (in a box or closed room) and one in partial light, like at the back of a room with light coming in from the front
- measure and record (in 3 separate charts, separated by light condition) the heights of each seedling in the same way as before for at least 5 consecutive days
[] calculate a mean height for each day of growth in the three different charts
RESULTS:
- full light grows relatively straight and is roughly the same height as seedlings in partial light
[] leaves are green and healthy
- partial light grows bent towards the light source
[] leaves are green and healthy
- darkness grows straight upwards and is by far the tallest due to growing rapidly trying to reach light
[] leaves are yellow or lighter green due to having no sunlight to photosynthesise with
Describe the method of a practical investigating the effects of gravity on newly germinated seedlings
- germinate seedlings (all of same type of seed) using cotton wool soaked in water in a petri dish, watering with the same volume of water daily until germinated
- place the petri dish of seedlings on its side in the dark (so phototropisms don’t interfere)
[] observe shoots growing upwards and the shoots growing downwards after a period of at least 5 days of growth
What are the 3 main plant hormones and their uses in plants and horticulture/agriculture ?
- auxin:
[] used for growth and photo/geotropism in plants
[] in agri/horticulture, used for rooting powders (good for clones from cuttings of plants) as well as weed killers, as a surplus of the hormone causes rapid uncontrolled growth that kills the plant when absorbed through the leaves (most weeds have broad leaves whilst crop plants have narrower leaves, so absorb less and are safe from the killer)
[] weed killers remove competition for nutrients and space, allowing crop plants to grow bigger and more healthily, increasing yield and profit for farmers
[] rooting powders allow quicker production of clones to be sold, raising profits - gibberellin:
[] initiates seed germination
[] used in brewing industry to end seed dormancy, thus speeding up the germination of barley seeds for malt
[] promote flowering throughout the year for pot plants; useful for horticultural industries and plant sellers
[] are used to make fruits bigger and thus more profitable as more people buy the fruits in general instead of a select few appealing fruits - ethene:
[] technically a gas that promotes ripening of the plant’s fruits
[] used to ripen fruit quickly after transport for sale
[] reduces waste of unsold product in transport etc.
