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AQA Biology > Homeostasis > Flashcards

Homeostasis Flashcards

1
Q

what is homeostasis?

A

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

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2
Q

why is homeostasis important?

A

it maintains optimal conditions for enzymes and all cell functions

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3
Q

what does homeostasis control?

A
  • body temp
  • water levels
  • blood glucose concentration
  • ion levels
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4
Q

what controls homeostasis?

A
  • receptors=detect stimuli
  • co-ordination centres (brain+spinal chord+pancreas)=recieve & process info from receptors
  • effectors (musclees+glands)= carry out response to restore optimum levels
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5
Q

what is a negative feedback loop?

A

a type of regulatory system that helps to maintain conditions in the body within an ideal range

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6
Q

what does the nervous system allows us to do?

A
  • react to our surroundings
  • co-ordinate our behaviour
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7
Q

conscious action

A

stimulus –> receptor –> sensory neurone –> coordinator (brain) –> motor neurone –> effector –> response

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8
Q

what is the reflex arc?

A
  • stimulus detected by receptor
  • electrical impulse carried to sensory neurone to CNS
  • dendrites of sensory neurone=synapse=electrical impulse diffuses across through a chemical neurotransmitter to relay neurone in spinal cord
  • electrical impulse carried through spinal cord
  • reaches synapse= diffuses across through chemical neurotransmitter
  • reaches motor neurone= carries electrical impulse to effector= carries put the response (a reflex)
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9
Q

why are reflexes important?

A

they protect us

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10
Q

why are reflexes quick?

A

they don’t pass through the brain

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11
Q

required practical: reaction time

A
  1. The person being tested should sit with arm resting on edge of table
  2. They should hold a ruler vertically between thumb and index finger at 0 cm
  3. let go at the ruler with no warning
  4. the person should catch the ruler as quickly as they can
  5. reaction time measured with the number they catch the ruler at
  6. read the number above the thumb
  7. repeat and calculate a mean
  8. the person being tested should then have a caffeinated drink eg. a can of coke
  9. after 10 mins repeat experiment again, their reaction time should speed up
  10. variables you need to control: same person, same hand, ruler dropped from same height
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12
Q

characteristics of 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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13
Q

what are some key brain areas?

A

cerebral cortex (outer wrinkly layer of brain)
cerebellum or little brain (back of brain)
medulla or brain stem (base of brain, top of spinal cord)

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14
Q

what are their functions? Brain

A
  • cerebral cortex=consciousness, intelligence, memory, language, senses
  • cerebellum=controls balance, co-ordination
  • medulla= controls unconscious activities eg. breathing, heart rate
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15
Q

how can we study the brain?

A
  • studying patients with brain damage
  • electrically stimulating the brain
  • MRI scans
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16
Q

how do they work? Brain

A

electrical stimulation:
- tiny electrodes put in different brain parts
-tiny jolts of electricity stimulate these regions and the effects can be observed

MRI scans:
- magnetic fields have an effect on the protons in the water molecules of the body
- functional MRIs=images of different regions of the brain that are active during different activities eg. listening to music or recalling a memory=detect changes in blood flow=more active regions=increased blood flow

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17
Q

why is it difficult to investigate brain functions?

A
  • research of the brain is risky= research is slower
  • research relies on dead people donating their brain
  • may be unethical= x informed consent from individuals
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18
Q

why is it difficult to treat diseases? Brain

A
  • incredibly complex and delicate organ=extremely difficult for neuroscientists to study it to find out how it works
  • limited understanding=so complex and different regions can’t be studied separately=treating brain damage+disease is very difficult;
  • any potential treatment carries risks of further damage=more problems eg. speech or motor issues, permanent personality changes
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19
Q

pros and cons of treating brain damage/disease

A
  • benefits=improving the quality of someone’s life (as the procedure is used to treat a disorder of some kind)
  • risks=more permanent damage, some of these will be because we still don’t fully understand how the brain and nervous system works
  • damaged neurones are hard to repair+they don’t repair themselves+ x way to repair them developed
  • damage eg tumours=difficult to remove= x easily accessible
  • surgery=dangerous=intricate procedure
  • high risk of damage=tissue very delicate
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20
Q

what is the eye?

A

sense organ containing receptors sensitive to light intensity and colour.

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21
Q

what are the parts of the eye?

A
  • retina
  • optic nerve
  • sclera
  • cornea
  • iris
  • ciliary muscles
  • suspensory ligaments
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22
Q

how are they adapted? Eye

A
  • retina - has 2 types of receptors (sensitive to colour/light)
  • optic nerve - carries signals from retina to brain
  • sclera - tough, supporting eye wall
  • cornea - transparent outer layer (refracts light into eye)
  • iris - coloured part of eye (controls size of pupil)
  • ciliary muscles - control shape of lens
  • suspensory ligaments - control shape of lens
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23
Q

what is accommodation?

A

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

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24
Q

how does the eye focus on near objects?

A
  • ciliary muscles contract
  • suspensory ligaments loosen (slack)
  • lens is then thicker and refracts light rays strongly.
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25
Q

how does the eye focus on far objects?

A
  • ciliary muscles relax
  • suspensory ligaments are pulled tight (taut)
  • lens is then pulled thin and only slightly refracts light rays.
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26
Q

what the 2 common eye defects?

A
  • myopia (short sighted)
    light focuses before retina
  • hyperopia (long sighted)
    light focuses behind retina
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27
Q

how can they be treated? Eye

A

myopia
- concave lenses
hyperopia
- convex lenses
both
- hard/soft contact lenses
- laser eye surgery
- lens replacement

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28
Q

what is thermoregulation?

A

how body temp is controlled
done by thermoregulatory centre in brain

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29
Q

how does the thermoregulatory centre detect temp?

A
  • has receptors that sensitive to blood temp
  • skin=temp receptors=send electrical impulses to thermoregulatory centre
30
Q

what happens when temp is too high or too low?

A
  • body temp is too high=blood vessels dilate/get wider (vasodilation)+sweat is produced from the sweat glands+hairs lie flat
  • body temp is too low=blood vessels constrict/get narrow
    (vasoconstriction)+skeletal muscles contract (shiver)+hairs stand up
31
Q

what is the endocrine system?

A
  • composed of glands which secrete hormones directly into the bloodstream
  • blood carries hormone to a target organ where it produces an effect
  • slower+act for longer compared to nervous system
32
Q

what is a hormone?

A
  • chemicals that act like messengers
  • secreted by glands+ carried in bloodstream from organ to organ
33
Q

what are the glands in our body?

A
  • pituitary gland
  • pancreas
  • thyroid
  • adrenal gland
  • ovary
  • testes.
34
Q

where as these glands found?

A

pituitary gland - brain
* pancreas - by kidneys
* thyroid - throat
* adrenal gland - on top of kidneys
* ovary/testes - vagina/penis

35
Q

what does the pituitary gland do?

A
  • master gland
  • secrets lots of hormones which act on other glands in the body= stimulate other hormones
36
Q

what happens when blood glucose is too high?

A

beta cells in pancreas detect rise in blood glucose=pancreas releases insulin=make liver turn glucose into glycogen for storage in liver+muscles

37
Q

what happens when blood glucose is too low?

A

alpha cells in pancreas detect drop in blood glucose=pancreas releases glucagon=make liver turn glycogen back into glucose

38
Q

what are the symptoms of diabetes?

A
  • increased blood glucose levels after eating
  • kidneys excrete glucose in urine
  • frequent urination
  • increased thirst
  • lack of energy
  • weight loss
  • blurred vision
  • cuts/wound heal slowly
  • itching around genitals
39
Q

what is type 1 diabetes?

A

a disorder in which the pancreas fails to produce sufficient insulin

40
Q

what are the causes of type 1 diabetes?

A
  • genetics
  • pancreas produces little to no insulin
  • blood glucose is at a deathly high level
41
Q

how do you treat type 1 diabetes?

A
  • insulin injections
  • limit simple carbs
42
Q

what is type 2 diabetes?

A

a disorder in which body cells no longer respond to insulin produced by the pancreas

43
Q

what are the cause of type 2 diabetes?

A
  • becoming resistant to own insulin
  • body cells x respond insulin
  • obesity is a risk factor
44
Q

how do you treat type 2 diabetes?

A
  • carb-controlled diet
  • regular exercise
45
Q

how do we lose water and how do we control it?

A
  • Water leaves the body via the lungs during exhalation.
  • Water, ions and urea are lost from the skin in sweat.
  • x control over water, ion or urea loss by the lungs or skin.
  • Excess water, ions and urea are removed via the kidneys in the urine.
46
Q

what does digesting proteins do?

A
  • results in excess amino acids=broken down by deamination in liver=ammonia released=toxic=converted to urea for safe excretion.
47
Q

what happens when water levels are too high?

A
  • receptors in brain detect increase in water levels
  • pituitary gland releases less ADH
  • kidneys reabsorb less water= urine is dilute
48
Q

what happens when water levels are too low?

A
  • receptors in brain detect low water levels
  • pituitary gland releases more ADH
  • kidneys reabsorb more water=urine is concentrated
49
Q

how do our kidneys work?

A
  1. ultrafiltration
    - small molecules eg. urea, glucose, ions, water
    - moved from bloodstream into kidneys (Bowman’s capsule)
  2. all glucose is selectively reabsorbed by active transport back into the blood
  3. loop of Henle
    - salt ions and water selectively reabsorbed
  4. any needed water is reabsorbed back into blood in the collecting duct
    - controlled by ADH
50
Q

what some kidney problems?

A
  • kidney stones
  • renal damage/failure
51
Q

how can renal damage/failure be treated?

A
  • dialysis
  • organ transplant
52
Q

how does dialysis work?

A
  • unfiltered blood that is high in urea is taken from a blood vessel in the arm
  • mixed with blood thinners=prevent clotting
  • pumped into the dialysis machine
    Inside the machine
  • blood and dialysis fluid are separated by a partially permeable membrane
  • dialysis fluid= x urea+similar concentration of glucose and salt ions to blood=concentration gradient between blood+dialysis fluid
  • urea, excess salt ions, water diffuses across to dialysis fluid
53
Q

pros and cons of dialysis

A

pros
- available to all patients (no shortage)
- x immune-suppressant drugs
- no risk of rejection

cons
- limit salt+protein intake between sessions
- expensive for NHS
- regular sessions (4-6 hrs long)=impact patient life

54
Q

pros and cons of organ transplant

A

pros
- x control diet
- cheaper for NHS overall

cons
- immune-suppressants drugs= up risk of infection
- organ donor shortage
- operation=risky
- kidney only lats for 8-9 yrs approx.

55
Q

what are the main female and male hormones?

A
  • female: oestrogen
  • male: testosterone - stimulates sperm production
56
Q

hormones involved in menstrual cycle

A
  • FSH - causes egg to mature in ovaries+stimulates ovaries to produce oestrogen
  • LH - stimulates the release of mature egg
  • oestrogen - grows uterus lining+stimulates release of LH+inhibits release of FSH
  • progesterone - maintains uterus lining for 2nd half of cycle+inhibits release of LH+FSH
57
Q

menstrual cycle

A

day 1-7
- menstruation (uterus lining sheds) - progesterone

day 8-13
- uterus lining builds back up - oestrogen
- egg matures - FSH

day 14
- ovulation (release of an egg) - LH

day 15-28
- uterus lining sheds again if egg is unfertilised
- uterus lining is maintained if egg is fertilised=provides blood supply+nutrients to egg

58
Q

contraception methods

A
  • oral contraceptives that contain hormones to inhibit FSH production so that no eggs mature
  • injection, implant or skin patch=release progesterone to inhibit the maturation and release of eggs for a number of months or years
  • barrier methods eg. condoms+diaphragms=sperm X reaching an egg
  • intrauterine devices (IUD) which prevent the implantation of an embryo or release a hormone
  • spermicidal agents which kill or disable sperm
  • abstaining from intercourse when an egg may be in the oviduct
  • surgical methods of male and female sterilisation.
59
Q

how can you treat infertility with hormones?

A
  • ‘fertility drug’= pill with LH+FSH=pregnant normally
60
Q

what is IVF+procedure?

A
  • in-vitro fertlisation
  • IVF involves giving a mother FSH and LH to stimulate the maturation of several eggs.
  • The eggs are collected from the mother and fertilised by sperm from the father in the laboratory.
  • The fertilised eggs develop into embryos.
  • At the stage when they are tiny balls of cells, one or two embryos are inserted into the mother’s uterus (womb).
61
Q

dangers with IVF

A
  • multiple births eg. twins= risky for both mum+babies
  • causes emotional+physical stress
  • low success rates
  • side effects eg. mood swings, acne
  • expensive
  • embyos that x inserted=destroyed=unethical
62
Q

what is adrenaline?

A
  • hormone released by adrenal glands in times of fear or stress.
  • increases the heart rate+boosts the delivery of oxygen & glucose to brain + muscles=preparing body for ‘flight or fight’
63
Q

what is thyroxine?

A
  • hormone released by thyroid gland
  • regulates basal metabolic rate
  • stimulates protein synthesis=proteins=growth and development
  • levels are controlled by negative feedback
64
Q

how is thyroxine released?

A

in response to TSH= released from pituitary gland

65
Q

what hormones do plants release?

A
  • auxin
  • gibberellins
  • ethene
66
Q

what type of tropisms do plants have?

A
  • phototropism (light)
  • geotropism/gravitropism (gravity)
  • hydrotropism (water)
  • chemotropism (chemicals eg. minerals)
  • thigmotropism (touch)
67
Q

what does auxin control and how?

A
  • growth
  • produced at tips of shoots+roots

shoots
- diffuses down stem=cell elongation in shoots
- light shined directly on shoot= equal distribution=grow up
- light shined on one side= auxin moves to shaded side=unequal distribution=cells on shaded side elongate+bend towards light

roots
- slows growth in roots+curve downwards

68
Q

what do gibberellins control and how?

A
  • initiating seed germination
69
Q

what does ethene control and how?

A
  • cell division
  • fruits ripening
70
Q

required practical: effect of light on seedlings

A
  1. put cotton wool in 3 petri dishes and add the same volume of water in each
  2. add 10 seeds in each dish+put them in a warm place
  3. let seeds to germinate and add water if it dries
  4. ensure all dishes have the same no. of seeds eg. remove any seeds
  5. put one petri dish next to a window (full light), one in a dark cupboard (no light) and the last one in partial light (a dim room)
  6. measure the height of each seedling everyday for a week and record
  7. calculate mean height of each seedling everyday
  8. compare mean heights of seedlings in the different conditions
71
Q

how are plant hormones used?

A

Auxins
- weed killers
- rooting powders
- for promoting growth in tissue culture

Ethene
- control ripening of fruit during
storage and transport

Gibberellins
- end seed dormancy
- promote flowering
- increase fruit size

AQA Biology (7 decks)

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