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GCSE Biology Paper 2 > Homeostasis & Response > Flashcards

Homeostasis & Response Flashcards

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1
Q

what is homeostasis?

A

regulation of internal conditions of a cell or organism to maintain optimum conditions for function in response to internal & external changes

homeostasis maintains optimal conditions for enzyme action & all cell functions

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2
Q

what do all control systems involve?

A

receptors that detect stimuli (changes in internal or external environment)
coordination centre that receives & processes info (e.g. brain, spinal cord, pancreas)
effectors that cause responses to restore optimum conditions (muscles that contract & glands that release hormones)

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3
Q

describe negative feedback

A

if a change happens to organism, body responds in opposite direction to stop change.
this keeps conditions within narrow limits.

  1. receptor detects a stimulus e.g. level is too low
  2. coordination centre receives & processes information then organises response
  3. effector produces a response that counteracts the change & restores optimum level e.g. level increases
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4
Q

how is body temperature controlled?

A

stimulus: temperature of surroundings increases or decreases

receptors: temperature receptors (located near skin surface to detect changes in external temperature & in thermoregulatory centre to detect changes in temperature of blood)

coordinator: thermoregulatory centre in hypothalamus in brain receives info from receptors & automatically triggers effectors

effectors: produce a response dependent on whether body is too hot or too cold

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5
Q

what are body’s responses when core body temperature is too high? (be comparative)

A

sweat glands in skin produce more sweat (containing water & mineral ions) to cover skin surface
transfer heat energy from skin to environment to evaporate water
= more cooling of skin
= blood flowing through skin is cooled so core temp decreases

vasodilation
muscles in walls of arteries supplying blood to skin capillaries relax so blood vessels dilate
= more blood flow near surface
= more heat lost by radiation
= core body temp decreases

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6
Q

what are body’s responses when core body temperature is too low?

A

less sweat produced

skeletal muscles (e.g. in arm) contract & relax quickly - shivering
= increase rate of respiration in muscle cells
= releases heat energy as respiration is exothermic
= core body temp increases

vasoconstriction
muscles in walls of arteries supply blood to skin capillaries contract so blood vessels constrict/narrow
= less blood flow near surface
= less heat lost by radiation
= core body temp increases

(hairs stand up on end to trap insulating layer of air)

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7
Q

what does the endocrine system include?

A

glands that secrete hormones (chemicals) into bloodstream
blood carries hormone to target organ where it produces an effect

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8
Q

compare the effects of endocrine system vs nervous system

A

endocrine system effects:
involves hormones
slower
longer-lasting
general (affect more of body)

nervous system effects:
involves nerves
faster
shorter-lasting
precise

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9
Q

what is the pituitary gland?

A

‘master gland’ in the brain
secretes several hormones which act on other glands to stimulate other hormones to be released to cause effects

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10
Q

label pituitary gland
pancreas
thyroid
adrenal gland
ovary
testes

A

see book

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11
Q

what is the purpose of adrenaline & where is it produced?

A

produced in adrenal glands in times of fear & stress
increases heart rate
increases rate of oxygen & glucose supply to brain & muscles
prepares body for ‘fight of flight’ survival response

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12
Q

what is the purpose of thyroxine & where is it produced?

A

produced from thyroid gland
stimulates basal metabolic rate
important role in growth & development
stimulates other organs to increase metabolism

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13
Q

describe negative feedback loop for thyroxine

A

thyroid stimulating hormone (TSH) released from pituitary gland travels in blood & causes thyroxine to be released from thyroid gland
thyroxine travels in blood to pituitary gland

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14
Q

what organ monitors & controls blood glucose concentration?

A

pancreas

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15
Q

what happens when blood glucose concentration is too high?

A

pancreas secretes insulin
= affects target organs liver & muscle cells
= causes glucose to move from blood into cells e.g. liver & convert it into glycogen for storage
= blood glucose concentration decreases

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16
Q

what happens when blood glucose concentration is too low?

A

pancreas secretes glucagon
= causes glycogen to be converted into glucose which is released into bloodstream
= increase blood glucose concentration

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17
Q

what is diabetes?

A

when the body does not respond correctly to changes in blood glucose concentration

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18
Q

what is type 1 diabetes & how is it treated?

A

pancreas fails to produce enough insulin
uncontrolled high blood glucose levels
treated with insulin injections

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19
Q

what is type 2 diabetes & how is it treated?

A

caused by lifestyle
obesity is a risk factor for type 2 diabetes
body cells no longer respond to insulin
treated with a carbohydrate controlled (low carb) diet & regular exercise

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20
Q

how do water, mineral ions & urea leave the body?
what is this controlled by?
why is this important?

A

no control over:
1. via skin in sweat
2. (only) water leaves via lungs during exhalation
control over:
3. excess are removed via kidneys in urine

controlled by kidneys

cells do not function effectively if gain or lose too much water by osmosis

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21
Q

how do proteins (containing nitrogen) leave the body?

A

digestion of proteins from diet produces excess amino acids
in liver amino acids are deaminated to form ammonia
ammonia is toxic
ammonia immediately converted into urea (safer & is excreted)
urea is released into blood, filtered out of blood by kidneys & excreted in urine

22
Q

what is the function of the kidneys?

A

to maintain water balance in the body
produce urine by filtration of blood & selective reabsorption

23
Q

what 3 steps are involves in maintaining water & nitrogen balance in the body?

A
  1. filtering
  2. selective re-absorption
  3. urine release
24
Q

describe kidney filtering

A

water & dissolved substances (urea, glucose & ions) are filtered out of blood & pass into tubule
large molecules (proteins & blood cells) stay in blood & do not go into tubule

25
Q

describe selective reabsorption

A

involves osmosis of water (amount controlled by ADH) & diffusion + active transport of glucose & mineral ions

all glucose reabsorbed (for respiration to release energy)

water is selectively reabsorbed (see above)

mineral ions are selectively reabsorbed - only necessary are reabsorbed

urea - none is reabsorbed so forms urine along with excess water & mineral ions

26
Q

contents of:
blood entering kidney
tubule after filtering
blood leaving kidney
urine

A

see book

27
Q

what is the effect of ADH on permeability of kidney tubule?

A

ADH makes kidney tubule more permeable to water so more can be reabsorbed by osmosis

28
Q

describe negative feedback loop of ADH

A

when water concentration is too low (so blood is too concentrated), more ADH is released from pituitary gland into blood
so more water is reabsorbed from kidney tubules into blood by osmosis
= smaller volume of more concentrated urine
when water concentration is too high (so blood is too dilute), less ADH is released from pituitary gland into blood
so less water is reabsorbed from kidney tubules into blood by osmosis
= larger volume of more dilute urine

29
Q

what 2 methods can treat kidney failure?

A
  1. kidney transplant - cure
  2. dialysis - not cure (keep you alive while waiting for donor)
30
Q

what are the advantages & disadvantages of a kidney transplant?

A

advantages:
improved QOL bc no dialysis needed - can have normal diet
high success rate (especially if life donor)
cheaper in the long term

disadvantages:
must wait for compatible donor
risk of surgery complications
risk of infection after surgery
risk of rejection
must take immunosuppressant drugs so infections more likely

31
Q

how does dialysis work?

A

person’s blood flows b/w partially permeable membranes (allow urea, ions, water, glucose through but not proteins & blood cells) surrounded by dialysis fluid
dialysis fluid contains same concentration of useful mineral ions & glucose & water as healthy blood = not useful mineral ions & water leave blood by diffusion
& no urea so diffuses out of blood into dialysis fluid (steep concentration gradient)
dialysis restores concentrations of substances in blood to optimum levels

32
Q

what are the advantages & disadvantages of dialysis?

A

advantages:
keep person alive until find compatible donor
effective
no immunosuppressant drugs needed

disadvantages:
a lot of time spent in hospital
patient must have low protein diet
very expensive
risk of blood clots & infections

33
Q

what happens during puberty?

A

hormones cause secondary sex characteristics to develop
e.g. females - hips widen & breasts develop
males - shoulders get broader & voice deepens

34
Q

what is the female reproductive hormone & where is it produced?
what happens to eggs at puberty?

A

oestrogen
produced in ovaries
at puberty eggs begin to mature & 1 egg released around every 28 days = ovulation

35
Q

what is the male reproductive hormone, where is it produced & what is its function?

A

testosterone
testes
stimulates production of sperm

36
Q

what is the function of each hormone involved in menstrual cycle?

A

follicle stimulating hormone (FSH) - causes maturation of an egg in ovary & oestrogen release

oestrogen - causes uterus lining to develop & causes pituitary gland to stop FSH release & stimulate release of LH

luteinising hormone (LH) - stimulates release of mature egg (ovulation) & causes progesterone to be released from ovaries

progesterone - maintains uterus lining & stops FSH & LH release from pituitary gland

37
Q

where is each hormone involved in menstrual cycle produced?

A

oestrogen & progesterone produced in ovaries
FSH & LH produced in pituitary gland

38
Q

what happens if egg is not fertilised by sperm & implanted into uterus?

A

both egg & uterus lining are release = period

39
Q

what are the different hormonal & non-hormonal methods of contraception?

A

hormonal:
oral contraceptive pill that contains hormones e.g. oestrogen & progesterone - inhibit FSH production so no eggs mature
implant, injection or skin patch of slow release progesterone - inhibit maturation & release of eggs (LH) for months or years

non-hormonal:
barrier methods e.g. condoms & diaphragms - prevent sperm reaching egg
intrauterine devices - prevent implantation of embryo (or release hormone) e.g. coil
spermicidal agent - kills or disables sperm
abstaining from sexual intercource when egg may be in oviduct
surgical methods of sterilisation

40
Q

how are hormones used to treat infertility?

A
  1. FSH & LH fertility drug to woman - then may become pregnant in the normal way
  2. in vitro fertilisation (IVF)
    give mother FSH & LH to stimulate maturation of several eggs
    eggs collected & fertilised by sperm in lab
    fertilised eggs divide by mitosis to develop into embryos
    when tiny balls of cells, 1 or 2 embryos are inserted into uterus (womb)
41
Q

what are the advantages & disadvantages of IVF?

A

advantages:
allows pregnancy for couples who struggle to conceive naturally
can screen for genetic disorders
can use spare embryos for stem cell research

disadvantages:
emotionally & physically stressful
low success rate
can lead to multiple babies - risk to mother & babies
side effects of hormones
expensive cost to individuals & society

42
Q

why do plants produce hormones?

A

to coordinate growth & responses to light (phototropism) & gravity (gravitropism/geotropism)

43
Q

what hormone controls the response of roots & shoots & where is it produced?

A

auxin
produced in root & shoot tips

44
Q

direction of phototropism & gravitropism

A

shoots are positively phototropic (grow towards light for photosynthesis)
shoots are negatively gravitropic (grow against gravity towards light)

45
Q

how do plant shoots respond when light source is directly above shoot?

A

even distribution of auxin down both sides of the shoot
equal cell growth & cell elongation on both sides of the shoot
shoot grows straight up towards the light

46
Q

how do plant shoots respond when light source is from one side?

A

auxin moves & accumulates on shady side of the shoot
uneven distribution causes cells on shady side to grow faster & elongate more than cells on light side
shoot grows towards the light

47
Q

why does phototropism help a plant to survive?

A

plant grows towards light
leaves absorb more sunlight
more photosynthesis
produces more glucose

48
Q

how does auxin act differently in roots & shoots?

A

shoots: auxin stimulates cell growth & elongation
roots: auxin inhibits cell growth & elongation

49
Q

how do plant shoots respond to gravity?

A

auxin accumulates on underside of shoots due to gravity
uneven distribution of auxin stimulates cells on underside to grow faster & elongate more than cells on upperside
shoots grown upwards against gravity & towards light

50
Q

how do plant roots respond to gravity?

A

auxin accumulates on underside of roots due to gravity
uneven distribution of auxin inhibits cell growth & elongation of underside cells
upperside cells grow faster & elongate more than underside cells
roots grow downwards in direction of gravity into soil for water, mineral ions & anchorage

51
Q

what are other plant hormones & what are their functions & uses?

A

ethene - gas that controls cells division & ripening of fruit
used in food industry to control ripening of fruits during storage & transportation

gibberellins - important in initiating seed germination & stimulate growth of stems
end seed dormancy/speed up germination (brewing industry)
promote flowering
increase fruit size

52
Q

what are the uses of auxins?

A

weed killers & herbicides
rooting powders
promoting growth in tissue culture (cloning)

GCSE Biology Paper 2 (4 decks)

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