homeostasis Flashcards
what is homeostasis?
the regulation of conditions inside the body to maintain a stable internal environment, in response to both internal and external conditions, for optimal enzyme action and cell function
what are the general features of an automatic control system?
- receptor cells detect changes in the environment - stimuli (internal/external)
- these pass info to a coordination centre (e.g. brain, spinal cord, pancreas)
- coordination centre processes info, then sends it to effectors
- effectors are muscles or glands, and they carry out the response
what do the nervous and endocrine systems allow us to do?
coordinate our behaviour and respond to our surroundings
what conditions are regulated by the body’s automatic control systems?
- water levels
- urea concentration
- internal body temperature
- carbon dioxide levels
- blood sugar levels
what does the nervous system enable us as humans to do?
enables humans to react to their surroundings and coordinate their behaviour.
describe a reflex arc:
- stimulus detected by receptor
- electrical impulses pass from receptor along a sensory neurone to the cns
- at the cns, chemicals diffuse across a synapse to a relay neurone, which then diffuse chemicals across another synapse to the motor neurone
- the electrical impulse now passes along the neurone to the effector, causing a response
- these effectors may be contracting muscles or hormone secreting glands.
what is the importance of reflex actions?
reflexes are rapid, automatic and unconscious actions, meaning that they can be used in dangerous situations to help protect us.
what are synapses and neurotransmitters?
synapse: gaps between neurones and are found at each junction of the reflex arc
neurotransmitter: chemicals that diffuse across synapses and bind to receptors on the next neurone
describe what occurs at a synapse:
the electrical impulse reaches the end of the neurone, triggering the release of neurotransmitters. these diffuse across the synapse, and bind to receptors on the next neurone. the presence of the neurotransmitter triggers the production of another electrical impulse.
- the electrical signal is temporarily converted to a chemical signal
describe the central nervous system:
- brain, spinal cord
- takes in sensory info, decides what must be done, and sends out orders to the rest of the body
- the spinal cord only really controls simple reflexes: the brain makes all of the important decisions
describe the brain:
- controls complex behaviour.
- made of billions of interconnected neurones and has different regions that carry out different functions.
describe the cerebellum:
responsible for muscle coordination. affects movement, posture, balance and speech.
- at the back of the brain, just under the cerebral cortex
describe the cerebral cortex:
responsible for conscious thought (e.g. memory, language, intelligence)
- also controls senses, e.g. vision, hearing
- big wrinkly bit all around the top
describe the two hemispheres of the cerebral cortex:
- the left hemisphere controls the muscles on the right side of the body and vice versa
describe the medulla, contained within the brain stem:
responsible for unconscious activities (e.g. breathing, heartbeat)
- just above the spinal cord
describe the hypothalamus:
- in the middle
- involved in regulating things, e.g. body temperature
- sends signals to the pituitary gland
describe research into the brain:
- becoming increasingly important. the more scientists understand about how the brain functions, the more likely they are to be able to develop treatments for brain conditions.
- our current understanding of the brain is very limited.
- there are many risks associated with brain studies and treatments of brain disease, as well as ethical concerns.
- the brain is very complex and delicate.
why is treating the brain so difficult?
- wide range of things that can go wrong (e.g. tumours, trauma, mental health problems, infection)
- the fact that it’s encased within a skull (hard to access), and as the surrounding brain tissue is also fragile, it’s difficult to fix anything through surgery
- as the brain is so complex and not yet understood, it’s difficult to fix things with drugs and chemicals
describe brain damage as a way of understanding the brain:
doctors can study people who have had brain damage in certain areas to examine the effect of these injuries on brain function. allows them to map out which area of the brain coordinates what.
- raises ethical concerns, surrounding whether it’s right to study a person when they aren’t in an adequate condition to give permission for this study to happen.
describe electrical stimulation:
- electrical stimulation: treats certain brain disorders (e.g. parkinson’s disease). the nervous system communicates through electrical impulses, so electrical stimulation can help to ‘reset’ the malfunctioning brain area.
- scientists can stimulate different areas of the brain with a weak electrical current, asking patients to describe what they experience.
- if the motor area is stimulated, the patient makes an involuntary movement.
describe MRI scanning:
- MRI: magnetic resonance imagery
- scanners allow us to learn which areas of the brain are active during different activities (e.g. moving, speaking, listening)
- e.g. could be shown an image of something sad during the scan, and a part of your brain will appear brighter, as it’s associated with emotions/sight
- use strong magnetic fields and radio waves to show details of brain structure and function.
what other ways are there to scan the brain?
- CT scans (x-rays). mainly used for seeing which areas of the brain are damaged
- PET scans (using radioactive chemicals) are similar to MRI scans, which measure the underlying brain activity
describe the eye:
a sense organ containing receptors sensitive to light intensity and colour.
describe the role of the retina and the optic nerve:
retina: contains many receptor cells. sensitive to light intensity (rod cells) - more sensitive - and colour of light (cone cells)
- cone cells don’t work well in dim light. this is why you can’t see colours when it’s dark, as it’s only your rod cells working, and they see in black and white
optic nerve: transmits visual info (electrical impulses) to the brain
describe the role of the sclera and the cornea:
sclera: the white of the eye; opaque, protective outer layer
cornea: transparent (no blood vessels) frontal portion, refracts light by the same amount each time (the cornea and the lens help to focus the light rays on the retina)
- all of the oxygen it needs must diffuse into it from the outside air, rather than being supplied by the blood
describe the role of the iris and the pupil:
iris: controls pupil diameter and the quantity of light reaching the retina
pupil: hole in the centre of the iris that light passes through
describe the role of the suspensory ligaments and the ciliary muscles:
- both control the shape of the lens
suspensory ligaments: a ring of fibres; connects the ciliary muscles to the lens. keeps the eye in place
- can only slacken/tighten as they’re not muscles
ciliary muscles: a ring of smooth muscle - changes the shape of the lens to focus light.
how is our internal bodily temperature monitored?
- receptors all over our body, in the skin and blood vessels
- send info about our temp. to the thermoregulatory centre in the hypothalamus, which can figure out if we’re too hot/cold
describe the lens:
- refracts light, fine-tuner after the cornea
- can change its shape, allowing it to control how strongly it refracts light
- always focuses light perfectly on the retina
what is the fovea?
special spot on the retina that only contains cone cells. this is the place that we try to focus light on, so that we can see things clearly
describe the iris reflex:
- controls the size of the pupil
- the pupil is made smaller in bright light conditions, so less light enters and damages the retina (CONSTRICTED)
- the pupil is made larger in low light conditions, allowing more light in, helping us to see in the dark (DILATED)
what are the two muscles that make up the iris?
- on the inside, surrounding the pupil, is the circular muscle
- ## surrounding the circular muscle are the radial muscles
- to constrict the pupils, the circular muscles contract, squeezing the pupils smaller, and the radial muscles must relax, to be stretched longer
- in dark light, the circular muscles relax and the radial muscles contract, making them shorter and pulling the pupil open
what is accomodation?
the act of the lens changing shape, therefore changing refraction, to focus on an object depending on its distance.
how will the rays hit the fovea depending on whether the object is far or near?
- close object. rays hit at a wide angle.
- far object. rays are almost parallel (very close together)
how does the eye accommodate to focus on a close object?
- the ciliary muscles contract inwards towards the lens
- suspensory ligaments loosen, no longer pulling tight on the lens, so the lens is free to return to the thicker, fatter shape
- lens becomes thicker and rounder, so that its’ more curved, which significantly refracts light rays.
how does the eye accommodate to focus on a distant object?
- ciliary muscles relax (moving away from the lens)
- suspensory ligaments tighten (pulls them taut, stretching the lens out)
- lens becomes flatter and thinner, which results in only a minor refraction of light rays (the cornea has already refracted the light most of the way)
describe myopia and hyperopia:
myopia (short-sightedness): when rays of light focus in front of the retina. the lens refracts light too much. forms an image before the retina, making the object appear blurry. can be treated with concave lens glasses (concave lenses refract light outwards, counteracting the over-refraction), which focus the light on the retina.
hyperopia (long-sightedness): when rays of light focus behind the retina, as the lens can’t refract enough. the image appears behind the retina, meaning it appears blurry. can be treated with convex lens glasses (extra refracting power), which focus the light on the retina.
describe modern technologies of fixing visual impairments:
- hard and soft contact lenses.
(in contact with the eye, float on the surface of the cornea. work like spectacle lenses, by focusing and refracting the light). - laser surgery to change the shape of the cornea. common for myopia but can also be used for some hyperopia conditions.
- replacement artificial lens in the eye. recent development. can be placed in front of the original lens, through a small cut in the cornea, to correct an eye defect.
what is thermoregulation?
the technical term for controlling the body temperature.
how is body temperature monitored?
monitored and controlled by the thermoregulatory centre in the brain. the thermoregulatory centre contains receptors sensitive to the temperature of the blood. INTERNAL
- the skin also contains temperature receptors and sends nervous impulses to the thermoregulatory centre. EXTERNAL
what occurs when you’re too cold?
- muscle contractions increase (shivering - the process requires energy through respiration, which produces heat)
- hairs stand on end, as the erector muscles are contracted (trapping an insulating area of air around the body)
- blood vessels constrict, so that blood doesn’t flow close to the skin surface, reducing heat transfer to the surroundings
what occurs when you’re too hot?
- sweat, mixture of water and salt, is released from sweat glands (sweat - releases water, covering the skin. heat is transferred to the water and evaporates with it)
- hairs lie flat
- blood vessels dilate, allowing blood to flow closer to the skin surface, releasing heat
what are hormones?
small chemical molecules passed into the blood, which spread throughout rhe body in the bloodstream
- make contact with some tissues, which have receptors specific to the hormone molecules. the hormone molecules act as signals to trigger certain changes within the cells
what are the 6 glands in the endocrine system?
- testes: produce testosterone (puberty, sperm production)
- thyroid gland: in our neck, produces thyroxine
- ovaries: produces oestrogen (controls puberty, one of the main hormones in the menstrual cycle)
- pancreas: produces insulin and glucagon (regulates blood glucose levels)
- pituitary gland (‘master gland’): found in the brain, linked to the hypothalamus. releases hormones in response to detected changes. (these hormones often trigger hormone releases in other glands, or can directly tell the body what to do)
- adrenal glands: sit above each kidney. produces adrenaline, triggers ‘fight or flight response’.
describe the hormone thyroxine:
- produced in the thyroid gland, found in the neck
- lots of roles, including growth and development, regulating heart rate, and body temperature. mainly increases metabolic rate (rate at which chemical reactions take place)
describe the negative feedback responses if the levels of thyroxine are too high or low:
too low: the pituitary gland releases TSH. this stimulates the thyroid gland to release more thyroxine. the thyroxine levels in the blood go back to normal
too high: the thyroxine will inhibit the pituitary gland from producing TSH. this mean the thyroid gland won’t release as much thyroxine, so the levels will go back to normal
describe the hypothalamus:
detects changes in hormone or water levels when the blood passes through it, and releases hormones to counteract these changes.
what is the endocrine system?
responds to changes in the environment using chemical messengers (hormones). these are released into the bloodstream by glands, and then travel to their target organ, where they produce an effect.
what is the difference between the endocrine and the nervous system?
endocrine:
- slower response
- chemical messengers in bloodstream
- long-lasting response
- acts on large areas
nervous:
- rapid response
- electrical impulses in nerves
- short-lasting response
- precise area of the body (e.g. one muscle)
what occurs when the level of thyroid hormones in the bloodstream decrease?
when this occurs, TSH (thyroid stimulating hormone) is released from the pituitary gland, stimulating the release of more thyroid hormones (e.g. thyroxine), bringing the levels of thyroxine back up to normal
- example of negative feedback
where are the adrenal glands situated, and when is adrenaline produced?
just above each kidney
- adrenaline is produced during the ‘fight or flight’ response, when you get scared, stressed, or needs to exercise. it prepares the body for activity
how does adrenaline affect the body?
- increases heart rate and blood pressure
- dilates eye pupils
- enlarges lungs’ air passages
- temporarily alters metabolism to boost delivery of oxygen and glucose to muscles and the brain (causes conversion of glycogen to glucose)
why do we need a good supply of glucose to our cells?
the cells can use the glucose to carry out cellular respiration
- however, having too much means it can start to damage our tissues
where are blood glucose levels monitored?
blood glucose levels are monitored by the pancreas. it releases either insulin or glucagon, depending on if the glucose levels are too high or too low.
- however both are released at the same time usually, resulting in fluctuating levels, just in extreme cases, one is secreted much more than the other
what occurs when glucose levels are too high?
- pancreas releases insulin into the blood stream
- liver and muscles detect insulin, and convert glucose into glycogen (long term storage form of glucose), reducing the release of glucose into the bloodstream
- the insulin attaches to receptor cells on the liver and muscle tissues
what happens if blood glucose levels are too low?
- the pancreas produces the hormone glucagon, causing glycogen to be converted back into glucose in the liver, and released into the blood.
what is the difference between insulin and glucagon?
insulin decreases blood glucose levels, glucagon increases blood glucose levels.
what is the difference between glucagon and glycogen?
- glucagon is a hormone
- glycogen is a large molecule made up of lots of glucose molecules
describe the difference between type 1 and type 2 diabetes:
type 1: pancreas is unable to produce enough insulin, or only produces a tiny amount. results in uncontrolled high blood glucose levels, resulting in feeling ill/death. inject insulin when needed into abdomen/thigh after a meal, bringing down their blood glucose levels before they get too high.
- generally occurs in children, but is lifelong
type 2: pancreas produces insulin, but the body no longer responds to it. manage diet, exercise regularly. obesity is a risk factor.
- cannot inject insulin as a solution, as the body doesn’t respond to it.
what two factors affect how much insulin needs to be injected into a type 1 diabetic?
- what they’ve eaten. eating more simply carbohydrates means more will need to be injected. they’re encouraged to eat less sugary things
- they’re also encouraged to exercise regularly, as the muscles absorb more glucose from the blood during exercise, meaning less insulin is required
how does urea form?
- digestion of protein results in too many amino acids, which can’t be stored.
- these amino acids undergo deamination (the amino group is removed from the molecule) in the liver, resulting in ammonia.
- ammonia is too toxic, and so is converted into urea (less toxic but still toxic to cells and tissues if there is a build-up), which is lost through sweat and urine.
describe the general structure of the kidneys:
- blood constantly cycles through them. enters through the renal arteries, and out through the renal veins
- from this blood, the kidneys produce urine, which pass down the ureters, and is stored in the bladder, until urinated out through the urethra
describe the structure of the kidneys during filtration:
- blood enters the nephron
- some of the liquid part of the blood is forced from the glomerulus (a tangle of blood vessels) into the Bowman’s capsule, the start of the tubule
- only about 20% of the blood plasma is filtered through to the Bowman’s capsule
where does selective reabsorption occur in the kidneys?
throughout the nephron after the glomerulus and the Bowman’s capsule
- goes the Bowman’s capsule, then the proximal convoluted tubule, then the Loop of Henle, then the distal convoluted tubule, then the collecting duct, which also receives fluid from other nephrons
there are three steps to the kidney process. describe the first step, ultrafiltration:
- blood passes through nephrons (in the kidneys). there are many capillaries, ensuring the blood is high pressure, which aids the process.
- small molecules (e.g. urea, water, ions, glucose) pass into the nephron tubules, whereas larger molecules (e.g. blood cells and proteins) are too large, and so remain in the blood.
there are three steps to the kidney process. describe the second step, selective reabsorption:
- having filtered out essential small molecules from the blood, the kidneys must reabsorb the molecules which are needed, while allowing the not required molecules to pass out in the urine
- (reabsorbed molecules include all glucose, as much water as required, as many ions as required)
there are three steps to the kidney process. describe the third step, the formation of urine:
- non-absorbed molecules (urea, excess water and ions) continue along the nephron tubule as urine, eventually passing out through the bladder.
define puberty:
the period in which adolescents begin to develop secondary sexual characteristics
- e.g. facial hair in men: TESTOSTERONE
- breasts in women: OESTROGEN
what is stage 1 of the menstrual cycle?
MENSTRUATION
period of bleeding that lasts about 4 days
- due to the breakdown of the uterus lining
what is stage 2 of the menstrual cycle?
lining starts to build back up again and becomes a thick spongy layer with lots of blood vessels
- lasts about 10 days up to day 14
- prepares the uterus lining for a fertilised egg
what is stage 3 of the menstrual cycle?
OVULATION
takes place in a single day
- the egg is released from one of the ovaries
what is stage 4 of the menstrual cycle?
lasts from day 14-28
- involves maintaining the lining of the uterus
- if no fertilised egg has attached to the uterus lining, then it will start to break down again, signalling the start of the next cycle (menstruation)
- if there was a fertilised egg, it would implant into the uterus lining, and slowly develop into a foetus. if this happens, the menstrual cycle would stop
describe the menstrual cycle:
- FSH is released by the pituitary gland and causes an egg in the ovary to mature. stimulates the production of oestrogen,
- Oestrogen is produced in the ovaries and causes the development of the thick, spongy uterus lining. It stimulates production of LH, and inhibits the production of FSH.
- LH is released in the pituitary gland, and stimulates the release of a mature egg on Day 14 (ovulation)
- Progesterone is produced in the ovaries after ovulation. Maintains uterus lining from Day 14-28. When progesterone levels drop, the lining breaks down, marking Day 1 of the next cycle. It also inhibits production of LH and FSH.
what happens to males and females, respectively, during puberty?
males:
- testosterone levels rise - sperm production stimulated.
- underarm, facial hair, and pubic hair grow.
- voice deepens.
females:
- oestrogen levels rise - menstruation stimulated.
- underarm and pubic hair grow.
- breasts enlarge.
define contraception:
any artificial method people use to prevent pregnancy
what are the two types of contraception?
these can also be either hormonal or non-hormonal (e.g. chemical is usually hormonal, surgical and barrier is non-hormonal)
why are oestrogen and progesterone used in hormonal contraception
- oestrogen inhibits FSH, meaning no egg will be developed or released
- progesterone stimulates the production of a thick mucus in the cervix, so prevents the sperm from reaching the egg
describe the difference between the combined oral pill and the progesterone-only pill:
combined:
- contains both oestrogen and progesterone
- by taking it everyday, enough oestrogen builds up that it inhibits the production of FSH so that no eggs mature
> lighter periods
> reduce period pains
> over 99% effective
> side effects (acne, mood-swings, nausea, headaches) > doesn't protect against STDs
progesterone-only:
- stimulates the production of a thick, sticky mucus, making it difficult for sperm to penetrate. inhibits the release of FSH. just as effective as the combined pill but with fewer side effects.
> used when breastfeeding
> can take at any age
> suitable if you can’t take oestrogen
> just as effective, fewer side effects
> must take same time every day > some medicines can make it less effective
describe the contraceptive patch/implant/injection:
patch: replaced weekly, slowly releases progesterone and oestrogen into body. small sticker placed on upper arm
- good during menopause
- doesn’t protect against STDs, side effects (blood clots, headaches), some may be allergic to the material, visible
implant: small flexible plastic rod placed under skin of the arm usually, replaced up to every 3 years, releases progesterone into bloodstream to prevent pregnancy.
- doesn’t interrupt sex, reversible, safe to use while breastfeeding, small procedure.
- side effects (headaches, nausea, mood-swings), irregular periods.
injection: done every three months, releases progesterone into the body, preventing ovulation.
- don’t have to think about it often
- side effects (weight gain, headaches, mood swings), doesn’t protect against STDs
describe the intrauterine device (IUD):
- small, t-shaped copper device inserted into the uterus, prevents sperm from surviving in the uterus by killing them
- prevents implantation of an embryo
- the plastic version releases progesterone, releasing a sticky mucus
> some release progesterone, effective, can be left in for 5-10 years, reversible
some may be allergic to copper, risk of infection, can be uncomfortable/intrusive, painful surgery, doesn’t protect against STDs
what do all non-hormonal methods of contraception have in common?
all prevent the sperm from reaching the egg
describe male condoms, and their advantages and disadvantages:
a barrier method during sex. placed over the penis, traps sperm
- effectively protects against STDs
- tears easily, some are allergic to latex, must check expiry dates beforehand
describe female condoms (diaphragm), and their advantages and disadvantages:
- worn inside the vagina, prevents sperm from reaching egg
- helps against STDs, protects both people
- can spill, not widely available, expensive
- often has spermicidal agents, kills/disables sperm upon entrance.
describe the diaphragm, and its advantages and disadvantages:
shallow plastic cup that fits over the cervix, blocking sperm from entering the uterus
- not reliable, must be used with spermicide (kills sperm)
- spermicide can be used alone as contraception, but only works 7/10 times
what is the one way to ensure a 0% chance of pregnancy?
abstinence.
- other less reliable methods include only having sex at certain times of the month and stopping sex just before ejaculation (pull out game)
what’s the difference in sterilisation between males and females?
male: sperm ducts (tubes between testes and penis) are cut so sperm can’t be released during ejaculation
female: fallopian tubes are cut/tied so the egg can’t reach the uterus
what is the difference between gametes and zygotes?
gametes = sex cells
zygotes = fertilised eggs
why might some males and females be infertile?
males: low sperm count, poor quality sperm, hormone problems.
females: ovaries don’t release eggs, fallopian tubes are blocked, uterus lining isn’t thick enough, hormone problems.
what are the two methods of increasing your chance of pregnancy?
IVF and drugs.
- drugs containing FSH and LH can be prescribed by a doctor, boosting the chance of an egg being released
- IVF (In Vitro Fertilisation) is where:
> FSH and LH are given to stimulate
the maturation of many eggs
> Eggs are collected from the ovaries
before being fertilised in a petri dish
with the father’s sperm
> These fertilised eggs develop into
embryos in an incubator and one or
more are implanted in the woman’s
uterus and one or more should grow
into a foetus
a: safe track record (used since 1978), embryos screened for genetic diseases, unused eggs used for research, allows infertile couples to have children
d: expensive, side effects from drugs (hot flushes, severe headaches), emotionally and physically stressful, can lead to multiple births (dangerous for both mother and twins/triplets, due to miscarriage and stillbirth), not very high success rates (1 in 4)
why are embryos kept in an incubator inside laboratories?
provides the optimum temperature for enzymes and thus cell growth
why may people be ethically against IVF?
involves unused embryos that are eventually destroyed, even though they have the potential for human life
describe the recent advances in IVF:
advances in microscope technology means there are higher success rates and we can now remove single cells from embryos to test for genetic diseases
- we can also use this to find characteristics of the baby (e.g. gender, eye colour). some fear this may lead to ‘designer babies’, however, where we pick the one we like the most. this is currently illegal in the UK however UNETHICAL
what do doctors do if a man has a low sperm count?
intra cytoplasmic sperm injection (ICSI)
- sperm is injected into the egg cell with a fine needle
what is meant by the ‘basal metabolic rate’?
the resting metabolic rate
what do gibberellins do in plants, and why are they helpful?
- promote flowering (normally requires certain conditions. we can make more/bigger flowers), increase fruit size
- the addition of gibberellins ends seed dormancy and induces germination. means the farmers can grow multiple crops per year, and that they all start growing at the same time
what is seed dormancy?
seeds sitting in soil won’t germinate and start growing until the conditions are just right (enough warmth, oxygen, water). the period before a seed starts growing is called dormancy
what do auxins do in plants, and why are they helpful?
- change growth patterns to allow roots and shoots to move either towards or away from a stimulus
- once these auxins are produced in the tips, they dissolve in the solution of the cells and diffuse backwards along the shoots/roots. they will then always either accumulate on the shaded side/lower side
- stimulate growth in shoots, inhibit growth in the roots
- used as weed killers, as adding enough of them means the rapid growth uses up all of the weed’s resources, killing it. it disrupts the plant’s growth patterns
- also used in a growth medium to promote tissue growth to form plant clones
- can be used with plant cuttings. used in a rooting powder to encourage it to form roots and grow
describe the growth of shoots (auxins):
- positively phototropic (grow towards light), negatively geotropic (away from ground, opposite direction to gravity)
- if the sun is on the left, the right is in the shade, so the auxins will accumulate here
- auxins stimulate growth, causing these cells on the shaded side to grow faster than on the sunny side
- ## this difference in growth rate causes the shoot to curve around towards the light
- in the case of gravity, if the shoot is bent sideways, the auxins will gather on the lower side and that side will grow faster
- the shoot will curve upwards
what is a tropism?
a response to a stimulus that involves directional growth.
- a negative tropism is if it grows away from a stimulus.
- a positive tropism is if it grows towards the stimulus.
e.g. light tropism = phototropism, gravity tropism = geo/gravitropism.
do plants rely on nerves or hormones to respond to environmental stimuli?
rely on hormones, but they usually act locally, instead of on a large area like in animals
what does ethene do in plants, and why is it helpful?
- a gas that controls cell division and the ripening of fruits
- used in the food industry to control the ripening of fruit during storage and transport (some fruits ripen much quicker than others). we can pick fruit before it’s ripe, to give us enough time to transport it, and so it isn’t damaged during this time. when it reaches its destination, we can expose it to lots of ethene to quickly ripen it, ready for sale
how does ethene work?
plants naturally produce them on their own, and this production is blocked during the transportation process.
- at a cellular level, ethene usually stimulates an enzyme that causes the fruit to ripen
what is ‘crenation hypertonic solution”?
too little water in cells.
what is “isotonic”?
same amount of water inside and outside of cells.
what is “lysis hypotonic solution”?
too much water in cells.
describe an underactive thyroid (hypothyroidism):
- the thyroid gland doesn’t produce enough hormones.
- symptoms: tiredness, weight gain, depression.
- caused by the immune system attacking the thyroid gland, or by treatments for other thyroid illnesses.
- treated by taking daily hormone tables to replace the hormones that aren’t being produced by the thyroid.
describe an overactive thyroid (hyperthyroidism):
- the thyroid produces too many thyroid hormones.
- 10x more common in women, usually happens between the ages of 20-40.
- symptoms: anxiety, irrationality, insomnia, heart palpitations, neck swelling, twitching/trembling.
- can be caused by Graves’ diseases, lumps on the thyroid, and some medicines.
- can be treated using medicine, radio therapy (destroys thyroid cells, reduces ability to produce thyroid hormones), surgery to remove part of thyroid.
what ways are inessential nutrients lost which the body has no control over?
- water leaves the lungs every time you exhale.
- water, mineral ions, and urea are lost through the skin in sweat.
what ways are inessential nutrients lost which the body has control over?
- urea, excess water, and excess mineral ions are removed via the kidneys, then excreted. this process is tightly regulated to:
- maintain water and mineral ion blood
content within the narrow limits.
- remove urea (poisonous nitrogenous
waste).
describe the kidneys:
we have two, but you can survive with one. they’re bean shaped organs, embedded in fatty tissue for protection. all your blood filters through them approx. every five minutes.
- main job is to filter the blood and remove whatever we don’t want (e.g. urea)
- regulates the levels of useful things (e.g. sodium and potassium ions, water)
where do we get ions from, and what happens if the levels get too high or low?
diet
- can damage our cells if too much/too little
where do we get water from, and what happens if the levels get too high or low?
- food and drink
- if there’s too much water in the body, the water will diffuse into our cells through osmosis, causing them to swell and possibly burst
- if there’s too little water in the body, the cells could lose their water and shrink
what is the difference between ureters and the urethra:
ureters = tubes that carry urine from the kidneys to the bladder.
urethra = the tube that carries urine out of the body.
how is the concentration of water in the blood regulated?
the volume of water in the blood is monitored by the hypothalamus. if water levels are too low, it triggers the pituitary gland to release the anti-diuretic hormone (ADH), which increases the permeability of the walls of the kidney tubules (more water is absorbed into the blood), meaning less water is lost in the urine, and less urine is produced overall
how can kidneys be damaged, what are the consequences, and what are the two ways they can be treated?
kidneys can be damaged by:
- accidents (excess alcohol and drugs)
- injections (diabetes)
- it can be fatal if left untreated, as toxins build up in the bloodstream
- inability to regulate water and ion levels
- person can become sick and die
kidney failure is treated by either (both are unreliable):
- dialysis
- kidney transplant (requires a donor)
describe the kidney transplantation process:
- take a healthy kidney and transfer it to a patient that needs it
- quite often the donor is someone who has just died, but a living person can also donate, as we’re born with two, but can live with one
- family members often donate, as the kidney needs to be similar to the patient’s tissue type, otherwise the patient’s immune system rejects it.
- immunosuppressant drugs decrease the chance of the kidney being rejected, as it makes the immune system work less efficiently
- however, the recipient will have to take these their entire life, and they don’t always work.
what are the advantages and disadvantages of a kidney transplantation?
a: have a normal life, as you don’t need constant check-ups, unlike dialysis, cheaper than dialysis in the long run
d: very expensive, some religions don’t allow transplantation, surgical procedure so there’s a risk that something will go wrong, not enough available organs for everyone
describe the dialysis process:
- needle linked to a dialysis tube is inserted into a blood vessel. the patient’s blood passes into the machine, through the circuit, then out into the patient
- when in the machine, the blood comes into contact with a dialysis fluid, but they’re separated by a partially permeable membrane: small molecules (e.g. water, ions) can diffuse across, but cells and proteins can’t
- if the patient has too much of anything, they’ll diffuse across the membrane into the dialysis fluid, due to the concentration gradient, bringing the patient’s blood levels back to normal
- however, this means it will eventually reach equilibrium, so the fluid is constantly replaced, meaning there’s always a concentration gradient
what does dialysis fluid contain?
the same concentration of water and other molecules (e.g. glucose, ions, amino acids) as healthy blood
- doesn’t contain urea
what are the disadvantages of dialysis?
- takes several hours, multiple times a week.
- causes the patient to become very tired.
- dialysis machines are expensive
- unpleasant experience - can cause health issues such as blood clots/infections
- must have it continuously for life
what is negative feedback?
when the level of something in our body gets too high/too low (e.g. blood glucose levels), negative feedback acts to return the levels back to normal - does the opposite of whatever the change was
