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homeostasis Flashcards

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1
Q

what is homeostasis?

A

the regulation of the internal conditions of a cell or organism to maintain optimum conditions for enzyme action and all cell functions in response to internal and external changes.

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2
Q

what are the general features of an automatic control system?

A
  • 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
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3
Q

what conditions are regulated by the body’s automatic control systems?

A
  • water levels
  • urea concentration
  • internal body temperature
  • carbon dioxide levels
  • blood sugar levels
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4
Q

what does the nervous system enable us as humans to do?

A

enables humans to react to their surroundings and coordinate their behaviour.

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5
Q

describe a reflex arc:

A
  1. stimulus detected by receptor
  2. electrical impulses pass from receptor along a sensory neurone to the cns
  3. at the cns, chemicals diffuse across a synapse to a relay neurone, which then diffuse chemicals across another synapse to the motor neurone
  4. the electrical impulse now passes along the neurone to the effector, causing a response
  5. these effectors may be contracting muscles or hormone secreting glands.
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6
Q

what is the importance of reflex actions?

A

reflexes are rapid and unconscious actions, meaning that they can be used in dangerous situations to help protect us.

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7
Q

what are synapses and neurotransmitters?

A

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

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8
Q

describe what occurs at a synapse:

A

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.

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9
Q

describe the brain:

A
  • controls complex behaviour.
  • made of billions of interconnected neurones and has different regions that carry out different functions.
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10
Q

describe the cerebellum:

A

responsible for muscle coordination. affects movement, posture, balance and speech.

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11
Q

describe the cerebral cortex:

A

responsible for conscious thought (e.g. memory, language, intelligence)

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12
Q

describe the medulla:

A

responsible for unconscious activities (e.g. breathing, heartbeat)

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13
Q

describe research into the brain:

A
  • 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.
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14
Q

describe brain damage as a way of understanding the brain:

A

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.
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15
Q

describe electrical stimulation:

A
  • 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.
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16
Q

describe MRI scanning:

A
  • MRI: magnetic resonance imagery
  • scanners allow us to learn which areas of the brain are active during different activities (e.g. moving, speaking, listening)
  • use strong magnetic fields and radio waves to show details of brain structure and function.
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17
Q

describe the eye:

A

a sense organ containing receptors sensitive to light intensity and colour.

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18
Q

describe the role of the retina and the optic nerve:

A

retina: contains many receptor cells. sensitive to light intensity (rod cells) and colour (cone cells)

optic nerve: transmits visual info (electrical impulses) to the brain

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19
Q

describe the role of the sclera and the cornea:

A

sclera: the white of the eye; opaque, protective outer layer

cornea: transparent frontal portion, refracts light (the cornea and the lens help to focus the light rays on the retina)

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20
Q

describe the role of the iris and the pupil:

A

iris: controls pupil diameter and the quantity of light reaching the retina

pupil: hole in the centre of the iris that light passes through

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21
Q

describe the role of the suspensory ligaments and the ciliary muscles:

A

suspensory ligaments: a ring of fibres; connects the ciliary muscles to the lens. keeps the eye in place

ciliary muscles: a ring of smooth muscle - changes the shape of the lens to focus light.

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22
Q

what is accomodation?

A

the act of the lens changing shape to focus on an object depending on its distance.

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23
Q

how does the eye accommodate to focus on a close object?

A
  • the ciliary muscles contract
  • suspensory ligaments loosen
  • lens becomes thicker and rounder, which significantly refracts light rays
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24
Q

how does the eye accommodate to focus on a distant object?

A
  • ciliary muscles relax
  • suspensory ligaments tighten
  • lens becomes flatter and thinner, which results in only a minor refraction of light rays
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25
Q

describe myopia and hyperopia:

A

myopia (short-sightedness): when rays of light focus in front of the retina. can be treated with concave lens glasses, which focus the light on the retina.

hyperopia (long-sightedness): when rays of light focus behind the retina. can be treated with convex lens glasses, which focus the light on the retina.

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26
Q

describe modern technologies of fixing visual impairments:

A
  • 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.
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27
Q

what is thermoregulation?

A

the technical term for controlling the body temperature.

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28
Q

how is body temperature monitored?

A

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

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29
Q

what occurs when you’re too cold?

A
  • muscle contractions increase (shivering - the process requires energy through respiration, which produces heat)
  • hairs stand on end (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
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30
Q

what occurs when you’re too hot?

A
  • sweat 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
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31
Q

what are the 6 glands in the endocrine system?

A
  • testes: produce testosterone (puberty, sperm production)
  • thyroid gland: in our neck, produces thyroxine (regulates heart rate, metabolism and body temperature)
  • 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)
  • adrenal glands: sit above each kidney. produces adrenaline, triggers ‘fight or flight response’.
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32
Q

describe the hypothalamus:

A

detects changes in hormone or water levels when the blood passes through it, and releases hormones to counteract these changes.

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33
Q

what is the endocrine system?

A

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.

34
Q

what is the difference between the endocrine and the nervous system?

A

endocrine:
- slower
- chemical messengers
- long-lasting response
- acts on large areas

nervous:
- rapid
- electrical impulses
- short response
- precise area of the body (e.g. one muscle)

35
Q

what occurs when the level of thyroid hormones in the bloodstream decrease?

A

when this occurs, TSH (thyroid stimulating hormone) is released from the pituitary gland, stimulating the release of more thyroid hormones (e.g. thyroxine).

36
Q

how does adrenaline affect the body?

A
  • 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
37
Q

where are blood glucose levels monitored?

A

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.

38
Q

what occurs when glucose levels are too high?

A
  • pancreas releases insulin into the blood stream
  • liver and muscles detect insulin, and convert glucose into glycogen, reducing the release of glucose into the bloodstream
39
Q

what happens if blood glucose levels are too low?

A
  • the pancreas produces the hormone glucagon, causing glycogen to be converted back into glucose in the liver, and released into the blood.
40
Q

what is the difference between insulin and glucagon?

A

insulin decreases blood glucose levels, glucagon increases blood glucose levels.

41
Q

describe the difference between type 1 and type 2 diabetes:

A

type 1: pancreas is unable to produce enough insulin. results in uncontrolled high blood glucose levels. inject insulin when needed.

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.

42
Q

how does urea form?

A
  • 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.
43
Q

there are three steps to the kidney process. describe the first step, ultrafiltration:

A
  • 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.
44
Q

there are three steps to the kidney process. describe the second step, selective reabsorption:

A
  • 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)
45
Q

there are three steps to the kidney process. describe the third step, the formation of urine:

A
  • non-absorbed molecules (urea, excess water and ions) continue along the nephron tubule as urine, eventually passing out through the bladder.
46
Q

describe the menstrual cycle:

A
  1. FSH is released by the pituitary gland and causes an egg in the ovary to mature. stimulates the production of oestrogen,
  2. 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.
  3. LH is released in the pituitary gland, and stimulates the release of a mature egg on Day 14 (ovulation)
  4. 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.
47
Q

what happens to males and females, respectively, during puberty?

A

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.

48
Q

what are the three methods of contraception?

A
  • surgical
  • chemical
  • barrier
  • these can also be either hormonal or non-hormonal (e.g. chemical is usually hormonal, surgical and barrier is non-hormonal)
49
Q

describe the difference between the combined pill and the progesterone-only pill:

A

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

  > 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

  > must take same time every day
  > some medicines can make it less 
  effective
50
Q

describe the contraceptive patch/implant/injection:

A

patch: replaced weekly, releases progesterone into body.
- 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 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

  • the release of progesterone into the body ensures the maturation and release of eggs each month is inhibited.
51
Q

describe the intrauterine device (IUD):

A
  • small, t-shaped copper device inserted into the uterus
  • prevents implantation of an embryo

> 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

52
Q

describe male condoms, and their advantages and disadvantages:

A

a barrier method during sex.
- effectively protects against STDs
- tears easily, some are allergic to latex, must check expiry dates beforehand

53
Q

describe female condoms (diaphragm), and their advantages and disadvantages:

A
  • prevents semen from entering the cervix.
  • helps against STDs, protects both people
  • can spill, not widely available, expensive
  • often has spermicidal agents, kills/disables sperm upon entrance.
54
Q

what is the one way to ensure a 0% chance of pregnancy?

A

abstinence.

55
Q

what’s the difference in sterilisation between males and females?

A

male: sperm ducts (tubes between testes and penis) are cut so sperm can’t be released during ejaculation

female: fallopian tubes are cut so the egg can’t reach the uterus

56
Q

what is the difference between gametes and zygotes?

A

gametes = sex cells
zygotes = fertilised eggs

57
Q

why might some males and females be infertile?

A

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.

58
Q

what are the two methods of increasing your chance of pregnancy?

A

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 growth of many eggs
    > Eggs are collected before being
    fertilised in a petri dish with the
    father’s sperm
    > These fertilised eggs develop into
    embryos and are implanted in the
    woman’s uterus

a: safe track record (used since 1978), embryos screened for genetic diseases, unused eggs used for research.

d: expensive, side effects from drugs (hot flushes, severe headaches), emotionally and physically stressful, can lead to multiple births (dangerous for both mother and baby), not very high success rates.

59
Q

what is meant by the ‘basal metabolic rate’?

A

the resting metabolic rate

60
Q

why do plants produce hormones?

A

coordinates and controls growth and responses to light (phototropism) and gravity (geotropism/gravitropism).

61
Q

what do gibberellins do in plants, and why are they helpful?

A
  • promote the seed germination (sprouting) process
  • promote flowering, increase fruit size
  • end seed dormancy.
62
Q

what do auxins do in plants, and why are they helpful?

A
  • change growth patterns to allow roots and shoots to move either towards or away from a stimulus
  • used as weed killers, as the rapid growth uses up all of the weed’s resources, killing it
  • also used as rooting powders (growth supplements) to promote tissue growth
63
Q

describe the auxin distribution depending on light patterns:

A
  • if the plant it lit evenly, the auxins spread evenly, meaning the plant grows straight.
  • if lit unevenly, auxins gather on the dark side so the plant grows more and bends towards the light.
64
Q

what is a tropism?

A

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.

65
Q

what does ethene do in plants, and why is it helpful?

A
  • 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
66
Q

what is ‘crenation hypertonic solution”?

A

too little water in cells.

67
Q

what is “isotonic”?

A

same amount of water inside and outside of cells.

68
Q

what is “lysis hypotonic solution”?

A

too much water in cells.

69
Q

describe an underactive thyroid (hypothyroidism):

A
  • 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.
70
Q

describe an overactive thyroid (hyperthyroidism):

A
  • 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.
71
Q

what ways are inessential nutrients lost which the body has no control over?

A
  • water leaves the lungs every time you exhale.
  • water, mineral ions, and urea are lost through the skin in sweat.
72
Q

what ways are inessential nutrients lost which the body has control over?

A
  • 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).
73
Q

describe the kidneys:

A

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.

74
Q

what is the difference between ureters and the urethra:

A

ureters = tubes that carry urine from the kidneys to the bladder.
urethra = the tube that carries urine out of the body.

75
Q

how is the concentration of water in the blood regulated?

A

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, meaning less water is lost in the urine.

76
Q

how can kidneys be damaged, and what are the two ways they can be treated?

A

kidneys can be damaged by:
- accidents (excess alcohol and drugs)
- injections (diabetes)

  • it can be fatal if left untreated, as toxins build up.

treated by either (both are unreliable):
- dialysis
- kidney transplant (requires a donor)

77
Q

describe the kidney transplantation process:

A
  1. quite often the donor is someone who has just died, but a living person can also donate.
  2. 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.
  3. immunosuppressant drugs decrease the chance of the kidney being rejected, as it makes the immune system work less efficiently.
  4. however, the recipient will have to take these their entire life, and they don’t always work.
78
Q

what are the advantages and disadvantages of a kidney transplantation?

A

a: have a normal life, as you don’t need constant check-ups, unlike dialysis.

d: very expensive, some religions don’t allow transplantation.

79
Q

describe the dialysis process:

A
  1. needle linked to a dialysis tube is inserted into a blood vessel. blood from the body is passed into a machine with a partially permeable membrane. the other side of the membrane is dialysis fluid. the concentration gradient means that unwanted substances can diffuse out, and useful substances can diffuse in.
  2. dialysis machines are more widely available than kidneys, so more people rely on it to keep them alive. it removes toxic products which could kill you.
80
Q

what are the disadvantages of dialysis?

A
  • takes several hours, multiple times a week.
  • causes the patient to become very tired.
  • dialysis machines are expensive.

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