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GCSE Biology > Topic 5 - Homeostatis and response > Flashcards

Topic 5 - Homeostatis and response Flashcards

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1
Q

Define homeostatis

A

The maintenance of internal conditions such as water, sugar, temperature and ion levels

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2
Q

Define a stimulus

A

something that changes in the environment

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3
Q

Define receptor

A

the thing that detects the change

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4
Q

Define co-ordinator

A

the part of the body that processes the change

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5
Q

Define effector

A

what causes the change (muscles or glands)

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6
Q

Define response

A

what happens to the body

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7
Q

What are the 2 parts of the central nervous system?

A
  • brain
  • spinal cord
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8
Q

Define a synapse

A

A gap between 2 neurones across which chemical signals pass.

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9
Q

What does SRSRMER stand for?

A

stimulus - receptor - sensory neuron - relay neuron - motor neuron - effector - response

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10
Q

Define a reaction time

A

the time taken to react to a stimulus

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11
Q

Define the suspensory ligaments (in the eye)

A

tough fibres that hold the lens in place

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12
Q

Define the iris

A

muscles that contract or relax to change the shape of the pupil - the coloured part of the eye

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13
Q

Define the sclera

A

tough protective layer - the white of the eye

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14
Q

Define the retina

A

layer containing light sensitive cells which send electrical impulses to the brain when stimulated by light

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15
Q

Define the optic nerve

A

a bundle of nerve fibres that sends electrical impulses to the brain

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16
Q

Define the cornea

A

transparent area at the front of the eye which allows light into the eye - it refracts light to direct it into the eye

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17
Q

Define ciliary muscles

A

muscles that contract or relax to change the shape of the lens to focus the light

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18
Q

What does the eye do to focus on a nearby object?

A
  • ciliary muscles contract
  • suspensory ligaments slacken
  • the lens becomes rounder
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19
Q

What does the eye do to focus on a distant object?

A
  • ciliary muscles relax
  • suspensory ligaments tighten
  • the lens becomes flatter
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20
Q

What does myopia mean?

A

short sight - can see near objects clearly and distant objects are blurred - the far point is too close

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21
Q

What does hyperopia mean?

A

long sight - can see distant objects clearly and close objects are blurred - the near point is too far

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22
Q

Why are people myopic?

A

their eyeball is longer than usual or their lens is too curved so the focus point is in front of the retina

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23
Q

Why are people hyperopic?

A

their eyeball is shorter than usual or their lens is too thin/flat so the focus point is behind the retina

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24
Q

What does the convex lens do?

A

causes the light rays to converge (go together)

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25
Q

What does the concave lens do?

A

cause the light rays to diverge (go apart)

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26
Q

What type of lens do myopic people need?

A

concave

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27
Q

What type of lens do hyperopic people need?

A

convex

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28
Q

What does the eye do in bright light?

A
  • circular muscles contract
  • radial muscles relax
  • pupil constricts (gets smaller)
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29
Q

What does the eye do in dim light?

A
  • circular muscles relax
  • radial muscles contract
  • pupil dilates (gets bigger)
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30
Q

What is the role of the cerebral cortex?

A

it’s responsible for things like consciousness, intelligence, memory and language

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31
Q

What is the role of the medulla?

A

it controls unconscious activities like breathing and your heartbeat

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32
Q

What is the role of the cerebellum?

A

it’s responsible for muscle coordination

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33
Q

What are the 3 methods of brain study?

A
  • studying patients with brain damage
  • electrically stimulating the brain
  • MRI scans
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34
Q

What are radial muscles in the eye?

A

go from centre to outside - straight lines

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35
Q

What are circular muscles in the eye?

A

go around the pupil in a circle

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36
Q

Name some treatments for vision defects

A
  • contact lenses/glasses
  • laser eye surgery changes the shape of the cornea so it will refract light differently
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37
Q

Describe the 2 body responses when you’re too hot

A
  • sweating - the heat is transferred from the body to liquid and evaporates
  • vasodilation - blood vessels widen so they are closer to the surface so more heat is lost through the skin
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38
Q

Describe the 3 body responses when you’re too cold

A
  • shivering - muscles contract which means more respiration which releases energy which releases heat
  • goosebumps - little hairs stand up and trap a layer of air for insulation
  • vasoconstriction - blood vessels get narrower and further from surface so less heat is lost through skin
39
Q

What happens in the thermoregulatory centre?

A

It is the place where temperature is monitored - it receives info from receptors in the skin and triggers the effectors

40
Q

Why would it be dangerous if all the glucose you absorbed stayed in the blood?

A
  • it would cause water to move out of the cells by osmosis
  • the body has to take glucose out of the blood for respiration
41
Q

Define glucose

A

it’s sugar used in respiration (to release energy)

42
Q

Define glycogen

A

it’s a carbohydrate - it’s a storage system in the liver made out of glucose

43
Q

Define insulin

A

a hormone that tells your body to change glucose into glycogen - it’s made in the pancreas

44
Q

Define glucagon

A

a hormone that tells your body to change glycogen into glucose - it’s made in the pancreas

45
Q

What happens when your blood sugar levels are too high?

A
  • insulin is secreted by the pancreas
  • the liver converts glucose into glycogen
  • levels drop
46
Q

What happens when your blood sugar levels are too low?

A
  • glucagon is secreted by the pancreas
  • the liver converts glycogen into glucose, and releases it into the blood
  • levels rise
47
Q

Name the 6 glands in the endocrine system

A
  • pituitary
  • thyroid
  • adrenal
  • pancreas
  • ovaries
  • testes
48
Q

What hormone does the thyroid gland produce?

A

thyroxine

49
Q

What hormone do the adrenal glands produce?

A

adrenaline

50
Q

What hormone do the testes produce?

A

testosterone

51
Q

Which gland is the master gland?

A

the pituitary gland

52
Q

What’s the difference between hormones and nerves?

A
  • nerves act quickly for a short amount of time in a specific area
  • hormones act slowly for a long time in a more general area
53
Q

How does type 1 diabetes occur?

A

the body produces little/ no insulin - this leads to a high blood glucose level

54
Q

How is type 1 diabetes controlled/ treated?

A
  • regular insulin injections
  • regular monitoring of blood sugar levels
55
Q

How does type 2 diabetes occur?

A

when the body doesn’t respond to the insulin produced - linked to obesity

56
Q

How is type 2 diabetes controlled/ treated?

A

control diet and regular exercise

57
Q

Name the 3 stages in the kidney

A
  • filtration
  • selective reabsorbtion
  • excretion
58
Q

Describe the stages of what happens in your kidney

A
  • excess amino acids are converted to ammonia then to urea
  • blood flows into the kidney
  • small substances are filtered out of the blood
  • useful molecules (all glucose and some mineral ions) are absorbed back into the blood by diffusion and active transport
  • blood flows away
  • waste substances (urea) continue out of the nephron, into the collecting duct and to the bladder
59
Q

Describe what your body does when you have too much water in your blood

A
  • there is a lower concentration of solutes in blood
  • so less ADH is released by the pituitary gland
  • kidney tubule wall becomes less permeable so less water is reabsorbed (more dilute urine)
60
Q

Describe what your body does when you have too little water in your blood

A
  • there is a higher concentration of solutes in blood
  • so more ADH is released by the pituitary gland
  • kidney tubule wall becomes more permeable so more water is reabsorbed
61
Q

Describe how dialysis machines work

A
  • blood is taken from an artery in the arm
  • blood flows between partially permeable membranes, surrounded by dialysis fluid - removes waste substances and excess water/ions
  • clean blood flows through bubble trap to remove any bubbles
  • blood returns to a vein in the arm
62
Q

Describe the substances in dialysis fluid and their concentrations

A
  • low in salt and urea (so salt and urea diffuse out of the blood to the lower concentration)
  • sugar and mineral concentration is same as blood (no movement)
63
Q

Name some advantages of dialysis

A
  • more readily available than transplant
  • no risk of rejection
  • no need for immunosuppressant drugs
64
Q

Name some disadvantages of dialysis

A
  • time consuming
  • expensive
  • will have to use for the rest of your life
  • can cause infections or blood clots
65
Q

Name some advantages of a kidney transplant

A
  • cheaper than dialysis
  • long term solution
  • can lead a normal life
66
Q

Name some disadvantages of a kidney transplant

A
  • risk of rejection (medication doesn’t always work)
  • only lasts 9 years
67
Q

What are the roles of FSH?

A
  • causes egg to mature in follicles
  • stimulates ovaries to produce oestrogen
68
Q

What are the roles of oestrogen?

A
  • builds up the lining of the uterus
  • stops FSH being produced
  • stimulates production of LH
69
Q

What are the roles of LH?

A
  • stimulates the release of a mature egg on day 14 (ovulation)
70
Q

What are the roles of progesterone?

A
  • stops the release of LH
  • stops the release of FSH
  • maintains the lining of the uterus
71
Q

Describe the hormones in the menstrual cycle

A
  • FSH released - egg matures and stimulates oestrogen
  • oestrogen released - thickens womb lining, turns off FSH and turns on LH
  • LH released - causes ovulation
  • progesterone released - maintains womb lining, turns off both FSH and LH
72
Q

Where are the 4 hormones involved in the menstrual cycle produced?

A

FSH - pituitary gland
oestrogen - ovaries
LH - pituitary gland
progesterone - ovaries

73
Q

Describe oral contraceptives

A

pills with oestrogen (to stop FSH production so no eggs can mature) and progesterone (which stops ovaries releasing eggs)

74
Q

Describe IUDs

A

a T-shaped device inserted into uterus
- plastic ones release progesterone
- copper ones prevent sperm surviving in the uterus

75
Q

Describe abstaining

A

not having intercourse

76
Q

Describe sterilisation (contraception method)

A

cutting the fallopian tubes or the sperm duct - permanent

77
Q

Describe a barrier method

A

stops the sperm and egg meeting (condoms, diaphragm etc.)

78
Q

Give some advantages and disadvantages of the contraceptive pill

A

+ 99% effective
- side effects - headaches, nausea etc.
- doesn’t prevent STDs

79
Q

Describe hormones given to increase fertility and give some pros and cons

A

FSH + LH are given to women to stimulate ovulation
+ helps pregnancy
- doesn’t always work
- multiple pregnancies could occur

80
Q

Describe IVF

A
  • women are given FSH + LH to stimulate several eggs to mature
  • eggs are collected and fertilised with sperm in a lab
  • fertilised eggs are grown into embryos
  • embryos are transferred into woman’s uterus
81
Q

Give some advantages and disadvantages of IVF

A

+ helps pregnancy
- success rate is low
- higher risk of multiple births
- emotionally + physically stressful

82
Q

Describe adrenaline

A
  • released by the adrenal glands
  • released in response to stressful/scary situations
  • increases the oxygen and glucose supply to cells
  • increases heart rate
83
Q

Describe how negative feedback works in the body

A
  • conditions change from set point
  • change detected
  • corrective mechanisms activated
  • conditions return to set point
  • corrective mechanisms switched off
84
Q

Describe thyroxine

A
  • released by the thyroid gland
  • it controls the metabolic rate of your body and is important in growth and development
  • it is released in response to TSH - a negative feedback system
85
Q

What is auxin and what does it do in the roots and in the shoots?

A
  • auxin is a plant hormone that controls growth
  • in shoots, it speeds up growth
  • in roots, it reduces growth
86
Q

Define tropism

A

a plant growing in response to a stimulus - movement towards stimuli is positive tropism and away is negative tropism

87
Q

Why does a shoot tip grow towards light?

A
  • the auxin moves to the shaded area
  • the auxin speeds up growth in the shaded side
  • so the plant grows towards the light
88
Q

Describe how a shoot grows in response to gravity

A
  • auxin is pulled downwards by gravity
  • the auxin speeds up growth on the lower side
  • this cause shoot to curve upwards
89
Q

Describe how a root grows in response to gravity

A
  • auxin is pulled downwards by gravity
  • the auxin reduces growth on the lower side
  • this causes the root to curve downwards
90
Q

Describe the 3 human uses of auxins

A
  • killing weeds - it disrupts their growth cycle + kills them
  • rooting powder - auxins in rooting powder cause cuttings to produce roots rapidly and grow as a plant
  • tissue culture - auxin promotes growth so cells can divide and clone
91
Q

Describe 3 human uses of gibberellin

A
  • ending dormancy - gibberellin alters dormancy so seeds germinate at times of the year they wouldn’t usually
  • growing larger fruit - helps seedless varieties grow larger to match the normal types
  • induce flowering - plants can flower without their usually required condition - also grows larger flowers
92
Q

Describe 1 human use of ethene

A
  • fruit can be picked when unripe and ethene (gas) is added to them to ripen on the way to shops
93
Q

Describe the plant growth responses RPA

A
  • put 10 cress seeds into 3 petri dishes, lined with moist cotton wool
  • shine a light on each dish, each going in different directions
  • leave them for a week and the shoots will have grown towards the light

GCSE Biology (7 decks)

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