B11

Question 1

What is the endocrine system ?

Answer 1

an organ system comprised of glands that secrete hormones (chemical messengers) in order to prompt a specific response from the body

Question 2

Describe the effects of hormones in comparison to those of the nervous system

Answer 2

• 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

Question 3

What is ADH ?

Answer 3

anti-diuretic hormone; controls water reabsorption in the kidneys by increasing the permeability of tubules in the kidneys

Question 4

What is FSH ?

Answer 4

• Follicle Stimulating Hormone
• stimulates the ovaries to produce the sex hormone oestrogen in females

Question 5

What is TSH ?

Answer 5

• Thyroid Stimulating Hormone
• stimulates the thyroid gland to secrete thyroxine, the hormone that helps to control the rate of metabolism

Question 6

What are the roles of the hormones secreted by the pituitary gland in the brain ?

Answer 6

• 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)

Question 7

What are the roles of the hormone secreted by the thyroid gland ?

Answer 7

• produces thyroxine
  [] controls metabolic rate of the body

Question 8

What are the roles of the hormone secreted by the adrenal glands ?

Answer 8

• 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

Question 9

What are the roles of the hormone secreted by the ovaries ?

Answer 9

• oestrogen
  [] controls development of female secondary sexual characteristics
  [] stimulates thickening and maintenance of uterine lining
  [] inhibits FSH
  [] stimulates the release of LH

Question 10

What are the roles of the hormone secreted by the testes ?

Answer 10

• testosterone
  [] controls development of male secondary sexual characteristics as well as the production of sperm

Question 11

What are the roles of the hormones secreted by the pancreas ?

Answer 11

• 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

Question 12

What is a hormone ?

Answer 12

• 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.)

Question 13

Describe how the pancreas controls blood glucose levels through the negative feedback loop involving insulin and glucagon

Answer 13

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

Question 14

What causes type 1 diabetes, and what are its effects ?

Answer 14

• 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

Question 15

What causes type 2 diabetes, and what are its effects ?

Answer 15

• 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)

Question 16

Describe how type 1 diabetes is TREATED

Answer 16

• 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

Question 17

Describe how type 1 diabetes is CURED and the associated pros/cons

Answer 17

• 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

Question 18

Describe how type 2 diabetes is TREATED

Answer 18

• 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

Question 19

Describe the negative feedback loop controlling metabolism in the body

Answer 19

-> 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

Question 20

List the female secondary sexual characteristics

Answer 20

• 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

Question 21

What is LH ?

Answer 21

luteinising hormone; stimulates release of eggs (ovulation)

Question 22

What role do oestrogen and progesterone play in the menstrual cycle ?

Answer 22

• 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

Question 23

What is menopause and how is fertility affected leading up to it ?

Answer 23

• 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

Question 24

Describe the secondary sexual characteristics of males

Answer 24

• 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

Question 25

How long is the average menstrual cycle ?

Answer 25

28 days - varies from individual to individual

Question 26

Describe the main stages of the menstrual cycle and the interaction of hormones over its course (and at which days they occur)

Answer 26

- 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

Question 27

Where is progesterone produced ?

Answer 27

empty follicle in ovaries after ovulation

Question 28

What are the 6 main methods/categories of contraception ?

Answer 28

- hormonal contraception - chemical contraception (spermicides) - abstinence - surgical methods - barrier methods - IUD (intrauterine device)

Question 29

What is abstinence, why/how is it used and how effective is it as a contraceptive ?

Answer 29

- 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

Question 30

What is a vasectomy, why/how is it used and how effective is it as a contraceptive ?

Answer 30

- 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

Question 31

What is tubal ligation, why/how is it used and how effective is it as a contraceptive ?

Answer 31

- 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

Question 32

What is an IUD, why/how is it used and how effective is it as a contraceptive ?

Answer 32

- 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

Question 33

What is a spermicide, and how effective is it as a contraceptive ?

Answer 33

- chemical contraception method - readily available, so are convenient, HOWEVER are relatively ineffective as a contraceptive

Question 34

What are the main barrier methods, why/how are they used and how effective are they as contraceptives ?

Answer 34

- 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

Question 35

What is the mixed pill, why/how is it used and how effective is it as a contraceptive ?

Answer 35

- 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

Question 36

What is the progesterone-only pill, why/how is it used and how effective is it as a contraceptive ?

Answer 36

- taken orally [] has to be taken very regularly and has risk of human error which affects effectiveness - hormonal contraceptive

Question 37

What are the three alternate hormonal methods to the pills ?

Answer 37

- 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

Question 38

What are the three main causes of infertility (other than naturally being infertile) ?

Answer 38

- age - eating disorders like anorexia - obesity

Question 39

Describe the fertility treatment for people who do not ovulate (frequently) and thus are infertile

Answer 39

- 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

Question 40

When is IVF (in-vitro fertilisation) used to treat infertility ?

Answer 40

- no clear cause of infertility - oviducts have been damaged/blocked - donor egg has to be used - problems with sperm count in semen

Question 41

How is IVF carried out ?

Answer 41

- 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

Question 42

Give the advantages of IVF treatment

Answer 42

- 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

Question 43

Give the disadvantages of IVF treatment

Answer 43

- 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.

Question 44

Why are gravitropisms and phototropisms important to plants' development ?

Answer 44

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

Question 45

What is phototropism and how does it work ?

Answer 45

- 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

Question 46

What is gravitropism and how does it work ?

Answer 46

- 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

Question 47

Describe the method of a practical investigating the effects of light on newly germinated seedlings

Answer 47

- 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

Question 48

Describe the method of a practical investigating the effects of gravity on newly germinated seedlings

Answer 48

- 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

Question 49

What are the 3 main plant hormones and their uses in plants and horticulture/agriculture ?

Answer 49

- 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.