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gcse bio > homeostasis > Flashcards

homeostasis Flashcards

1
Q

what is homeostasis

A

regulation of internal conditions of a cell/organism to maintain optimum conditions in responses to internal and external changes

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2
Q

three examples of internal conditions in humans

A

keep:
blood glucose concentration
body temperature
water levels

constant

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3
Q

features of automatic control system

A

receptor cells
coordination centre
effector

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4
Q

what do receptor cells do

A

detect stimulus/changes in environment (internal and external)

passes information to coordination centre

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5
Q

what does coordination centre do

A

receives and processes info from receptor cells
sends instructions to effector

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6
Q

what does effector do

A

muscle or gland that restores optimum level by carrying out response

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7
Q

two parts of nervous system

A

cns - brain and spinal chord
other nerves running to and fro cns

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8
Q

describe how nervous system works

A

receptors detect stimulus

sends electrical impulses down neurones to cns (coordination centre)

cns sends electrical impulses down neurones to effector

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9
Q

effectors are usually..

A

contracting muscles or hormone-secreting glands

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10
Q

how does reflex arc work

A

• receptor detects stimulus
• sends electrical impulses along sensory neurone to cns
• end of sensory neurone: synapse which releases chemical that passes impulse to relay neurone
• end of relay neurone: synapse releases chemical that passes impulse to motor neurone
• end of motor neurone: effector
• effector carries response

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11
Q

how to investigate reaction time

A

• p1 sits upright on stool and rests arm on table, dominant hand overhanging
• p2 holds ruler vertically, with 0cm at thumb level
• p2 drops at random time, p1 catches quick as possible
• record measurement at top of thumb
• repeat 5x and calculate mean. convert to reaction times using online conversion table

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12
Q

independent variable of investigating reaction time

A

drink caffeine and repeat experiment

dominant hand & non dominant hand

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13
Q

what does the brain do

A

controls our complex behaviours

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14
Q

what is the outer brain called and what does it do

A

cerebral cortex
responsible for language, memory, consciousness, and intelligence

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15
Q

what is the bit at the back of the brain called and what does it do

A

cerebellum
controls muscle coordination e.g movements and balance

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16
Q

what is the bit in the middle of the brain and what does it do

A

medulla
controls unconscious activity e.g breathing and heart rate

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17
Q

why are brain problems difficult to study

A

skull makes access difficult
extremely complex structures
delicate and easy to damage

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18
Q

three methods to study brain

A
  1. study patients with brain damage. by knowing where damage is, they can try to link that area to its function
  2. electrically stimulate it. do this to different parts of brain and look at effects on behaviour
  3. mri scans. allows us to look at which parts of brain are most active during activities
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19
Q

what stimulates receptors in eye

A

changes in light intensity and colour

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20
Q

what does cornea do

A

transparent front of eye. it refracts light rays into eye

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21
Q

what does lens do

A

focuses light rays to the back of the eye
ciliary muscles and suspensory ligaments can change shape to lens to focus on near/distant objects

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22
Q

what does the retina do

A

back of the eye - contains receptor cells for light intensity & colour, then send electrical impulses

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23
Q

what does the optic nerve do

A

carries impulses from retina receptors to brain

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24
Q

what does the sclera do

A

white part - tough, protective layer

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25
Q

what does the pupil do

A

space in centre of iris - allows light rays to pass into eye

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26
Q

what does the iris do

A

coloured part - controls size of pupil

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27
Q

explain what happens in eye when you enter a dark room

A

REFLEX ACTION
- light intensity is lower
• receptors in retina detect this
• electrical impulses sent to brain
• brain sends electrical impulses to muscles in iris
• muscles contract, causing pupil to become larger
• more light can enter eye

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28
Q

order of where light goes in eye

A

CIPLRO
cornea
iris
pupil
lens
retina
optic nerve

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29
Q

how to remember eye order

A

ciplro
can
i
please
live
really
old

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30
Q

what is accommodation

A

changing the shape of the lens to focus on near or distant objects

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31
Q

structure of lens

A

suspensory ligaments connects lens to surrounding ciliary muscle

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32
Q

what happens to lens when looking at near object

A

• ciliary muscles contracts, causing suspensory ligaments to loosen
• lens is now thicker and more curved
• meaning it refracts light more strongly

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33
Q

what happens to lens when looking at something far

A

• ciliary muscles relax, causing suspensory ligaments to pull tight
• lens becomes thin and less curved
• refracts light by smaller amount

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34
Q

what is hyperopia and why does it happen

A

long sightedness
eyeball is too short or lens is too thin, so when focusing on near objects,light is focused at a point behind the retina

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35
Q

how to treat long sight and graph

A

glasses with convex lenses - partially focus light before it enters eye

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36
Q

what is myopia and why does it happen

A

short sightedness
eyeball is too long or lens is too thick, so when focusing on distant objects, light focuses in front of retina

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37
Q

how to treat short sightedness and graph

A

glasses with concave lenses - partially unfocusses light before it enters eye

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38
Q

three treatments for vision defects with one pro and one con

A

contact lenses - convenient for sport, risk of infection
laser eye surgery to change shape of cornea - precise, risk of infection
replacement lens surgery - risk of damage to retina

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39
Q

what is normal body temperature

A

37 °

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40
Q

impulses from which receptors go the part of the brain that controls temperature, and what is the part of the brain called?

A

receptors in the thermoregulatory centre (TC) detect blood temp.
receptors in skin detect skin temp and send impulses to TC

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41
Q

what happens when body temp gets too high e.g during excersize

A

• receptors detect that its too high
• TC acts as coordination centre. it receives info from receptors and triggers effectors
• effectors e.g sweat glands respond

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42
Q

three things when body is too hot

A

• hairs are flat
• sweat glands -> sweat -> evaporates, energy taken from body -> body cools
• vasolidation

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43
Q

what is vasolidation

A

blood vessels that supply capillaries at surface dilate so more blood flows. heat transfers out of blood, body temp decreased

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44
Q

three things when body temp is too low

A

• hairs stand up - insulating air layer
• muscles contract, shivering. requires respiration, which transfers energy therefore warming body
• vasoconstriction

45
Q

what is vasoconstriction

A

blood vessels supplying capillaries at surface constrict. less blood flows, less heat lost

46
Q

what id the endocrine system

A

a system of glands, which secrete hormones directly into bloodstream, where it is carried all around body to their specific target organs to produce an effect

47
Q

compare the endocrine system and nervous system

A
  • NS has extremely fast action, ES has a much slower action
  • NS effects are short lived, ES effectd act for long time
  • NS uses electrical impulses which travel down neurones, whereas ES uses hormones (chemicals) travel through bloodstream
48
Q

how can you identify if a response is nervous or hormonal

A

response is quick: nervous
response lasts long tome: hormonal

49
Q

where is the pancreas and what role does it have in ES

A

found: upper abdomen
produces: insulin
use: regulate blood glucose level

50
Q

where are the ovaries found and what is their use in the ES

A

found: pelvis
produces: oestrogen
use: menstrual cycle

51
Q

where are the testes found and what is their use in the ES

A

found: behind penis
produce: testosterone
use: controls puberty and sperm production

52
Q

where is the thyroid gland found and what is its tole in the ES (need)

A

found: front of neck
produces: thyroxine
use: regulating basal metabolic rate, heart rate, and temperature

53
Q

where are the adrenal glands found and what role do they have in the ES

A

found: on top of kidneys
produce: adrenaline
use: when in fear or stress, “fight or flight” response

54
Q

where is pituitary gland/master gland found and what role does it have in the ES

A

found: brain
produces: many hormones, depending on body conditions
use: range of effects. it acts on other glands, causing them to release other hormones to bring about an effect

55
Q

what happens to glucose levels when you eat carbohydrates, and what does the body do?

A
  • conc of blood glucose rises
  • pancreas senses rise and produces insulin
  • insulin travels across body via blood
  • insulin triggers body cells to take up glucose from blood, and liver and muscle cells to store excess as glycogen
  • blood glucose returns to normal
56
Q

what happens to conc or blood glucose between meals and what does the body do?

A

blood glucose falls
- pacreas senses fall
- pancreas releases glucagon, travels across body via blood
- glucagon triggers liver cells to covert glycogen back to glucose, which is released into blood
- blood glucose returns to normal

57
Q

simple cycle of blood glucose levels throught day

A

after meal - glucose rises - insulin released - glucose taken in and converted
between meals - glucose falls - glucagon released - glycogen converted

58
Q

what is type one diabetes

A

pancreas does not produce enough sufficient insulin, meaning blood glucose can become dangerously high

59
Q

treatment for type one diabetes

A

monitor blood glucose conc and use insulin injections throughout the day, most likely after meals
also: limiting food rich in simple carbs, and regular exercise

60
Q

what is type two diabetes

A

when body cells stop responding to the bodys insulin, meaning blood glucose can become dangerously high

61
Q

type two diabetes treatment

A

diet, including controlling carbs
excercise

62
Q

pattern of water in body

A

constant balance

63
Q

three ways the body loses water

A

via lungs when exhaling. uncontrollable
via skin when sweating, which also contains sodium ion and urea. uncontrollable
via kidneys when urinating
controllable

64
Q

how do kidneys regulate excess water, ions, and urea?

A
  • blood containing urea enters kidney via artery
  • kidney removes urea, plus excess ions and water
  • these leave kidney as urine, stored in bladder
  • blood containing no urea leaves kidney via vein
65
Q

how do kidney adjust levels of molecules in blood

A
  • blood passes through capillaries, small molecules (urea, ions, water, glucose) are filtered out of blood. this is called filtration.
  • useful molecules (glucose, some ions, some water) reabsorbed back into blood. this is called selective reabsorption
    -waste is released as urine
66
Q

what does concentration of glucose, ions, and urea look like after passing through kidneys

A

glucose: same (filtered, reabsorbed)
ions: decreases (filtered, reabsorbed)
urea: virtually zero (filtered)

67
Q

how do we digest amino acids

A
  • when we digest protein, amino acids pass into blood.
  • liver breaks down excess amino acids and produces the chemical
    ammonia. this is called deamination
  • ammonia is very toxic, so liver immediately converts it to urea
  • kidneys safely excrete urea
68
Q

what does the body do when it loses too much water

A

water falls = blood too concentrated.
- pituitary gland releases ADH into bloodstream
- ADH travels to kidneys, causing tubules to become more permeable to water - more water reabsorbed to blood
- meaning less urine produced, water levels return to normal, pituitary gland stops releasing ADH

69
Q

what does the body do when blood is too dilute

A

water concentration rises
- pituitary gland stops releasing ADH
- kidneys reabsob less water into blood
- more urine produced, water levels return

70
Q

what is kidney dialysis

A

when kidneys fail and water, ion, and urea levels are adjusted using a machine

71
Q

how does kidney dialysis work

A

blood has higher conc of water, ions and urea
- patients blood passes over a semi permeable membrane
- urea, ions, and water allowed through, but not larger molecules e.g protein, blood cells
- on other side of membrane there is dialysis fluid, containing normal concs of water and ions, NOT urea
- there is now a conc gradient for urea
- urea diffuses blood -> fluid
- fluid constantly refreshed - constant large gradient
- excess water and ions also diffuse

72
Q

compare advantages and disadvantages of kidney dialysis and transplant

A
  • SHORTAGE. no shortage of dialysis machines, shortage of donors
  • LIFE. dialysis - several weekly treatments and controlled diet, donors lead normal life, however take anti rejection drugs forever
  • ## PRICE. dialysis is long term expensive, donors are initially expensive
73
Q

what is ovulation

A

the release of an egg from the ovary every 28 days

74
Q

what happens during menstrual cycle

A
  • ovulation occurs
  • uterus lining thickens in prepation
  • sperm present, egg fertilised and implants in uterine wall to develop
  • not present, egg and uterine lining break down and release, a period
75
Q

what are the four menstruation hormones

A

fsh (follicle stimulating)
oestrogen
lh (luteinising)
progesterone

76
Q

first stage of hormones

A
  • pituitary gland releases FSH
  • travels to ovaries, causes egg to mature
  • stimulates oestrogen
77
Q

second stage of menstruation hormones

A
  • ovaries produce oestrogen
  • causes uterus lining to thicken
  • stimulates LH, inhibits FSH
78
Q

third stage if menstrual hormone

A
  • produced by ptuitry gl
  • stimulates release of egg
79
Q

fourth stage of menstrual hormones

A
  • produced by ovaries after ovulation
  • inhibits fsh and lh -prevent more eggs
  • keeps lining thick in case egg fertilises
  • otherwise, progesterone falls, lining breaks down, period occurs
80
Q

how to remember order of hormones in menstrual cycle

A

F Ound
O Pen
L Obster
P incer

81
Q

how does the pill work

A

contains hormones (oestrogen and progesterone) which prevents production of fsh, preventing eggs from maturing
produces mucus to block sperm

82
Q

advantage disadvantage of oral contraceptives

A

99% effecicacy
lighter & less painful periods

no sti protection
requires memory to take it daily

83
Q

advantages and efficacies of patch, injection, and implant

A

lighter and less painful periods
convenient (not daily)
injection 97%
patch 91%
implant 99%

84
Q

which contraceptive methods are hormonal and what disadvantages do they have

A

pill, injection, implant, patch, iud
no protection from stis

85
Q

advantage and disadvantage of barrier methods (condom or diaphragm) and efficacy

A

85%
sti protection
hormone free
spermicide gel

can slip off (m) requires skill (f)

86
Q

what is an iud, its efficacy, and its advantages and disadvantages

A

prevents implantation, release hormon
99%
lasts 10 years

no sti protection
painful

87
Q

what is sterilisation and disadvantages

A

surgical contraception
women: prevents egg reaching uterus
men: prevents sperm leaving

very difficult to reverse
no sti protection

88
Q

what is abstaining and what are advantages and disadvantages

A

avoiding intercourse after ovulation

not “unethical” (no barrier methods)

hard to tell
no sti protection

89
Q

what is the most effective way of contraception

A

abstinence (no sex)

90
Q

what can be used if a woman las low levels of fsh and lh

A

fertility drug containing said hormones

91
Q

how does ivf work

A
  • fsh and lh given to stimulate eggs
  • eggs collected from mother
  • fertilised by sperm from father in lab
  • fertilised eggs develop to embryos
  • once tiny balls of cells, embryos inserted into uterus
  • embryos develop
92
Q

five disadvantages of ivf

A
  • low success rate
  • emotionally and physically stressful
  • multiple births - risks
  • many embryos destroyed - unethical
  • expensive
93
Q

what does the adrenal gland do

A

produces the hormone adrenaline to blood when in fear or stress.
heart rate increases -> more oxygen and glucose delivered to brain and muscles, preparing body to “fight or flight”

94
Q

what does thyroxine do

A

released by tsh from pituitary gland.
stimulates (speeds) bmr
growth and development

95
Q

what is negative feedback cycle

A

if level of a hormone falls, events triggered to cause it to increase. if level is too high, events triggered to decrease it

96
Q

negative feedback cycle for thyroxine

A

level falls: pituitary gland releases tsh -> thyroxine released
level now risen: brain detects -> prevents ptuitry gland releasing tsh, thyroxine returns

97
Q

what is phototropism

A

when plants grow towards light

98
Q

what is auxin

A

plant hormone in the tips of shoots and in the roots that responds to light (phototropism) and gravity (gravitropism)

99
Q

how is auxin used to grow towards light

A

auxin triggers cell growth
light causes auxin to concentrate and spread down the darker side of the shoot
this means cells on darker side grow faster, shoot grows towards light

100
Q

what is gravitropism (or geotropism)

A

plants growth in response to gravity

101
Q

how is auxin used to grow towards force of gravity

A

gravity causes auxin to concentrate on lower side.
in roots, auxin inhibits cell growth.
lower side grows slower, meaning roots grow toward force of gravity

102
Q

what are two chemicals used by plants to regulate behaviour and what do they do

A

giberellin: germination of seeds
ethene: cell division and ripening of fruit

103
Q

how do you investigate plant response to light

A
  • put 10 cress seeds in three different petri dishes with moist cotton
  • label a b and c
  • shine light: above, each direction
  • leave for one week in warm area and water daily
  • observe and draw graph
104
Q

why do seeds in the dark grow faster

A

seeds usually grow underground and grow rapidly to reach light

105
Q

how can you investigate plant response to gravity

A

place a dish of seedlings vertically in the dark

106
Q

three uses for auxins in agriculture

A
  1. weedkillers
    2 rooting powders
  2. growing cells in tissue culture, which is used to clone plants
107
Q

uses of gibberellin in agriculture

A
  1. ending seed dormancy
  2. encourage plants to flower
  3. make fruit grow larger
108
Q

used of ethene in agriculture

A

trigger foods to ripen before being sold e.g bananas

gcse bio (6 decks)

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