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Biology A2 content > 3.6.1 Stimuli, both internal and external, are detected and lead to a response > Flashcards

3.6.1 Stimuli, both internal and external, are detected and lead to a response Flashcards

1
Q

what is the taxis?

A

a simple response whose direction is determined by the direction of the stimulus

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2
Q

what is kinesis?

A

a non-directional response to a stimulus which brings about increased random movements.

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3
Q

what does negative photo taxis mean?

A

moving away from the light / towards the dark

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4
Q

what is positive chemotaxis?

A

move towards chemicals (cytokines, food etc.)

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5
Q

what does positive rheotaxis do for fish?

A

keeps them facing the current, increases chances of receiving food, increases rate of flow of oxygenated water over their gills

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6
Q

what is the difference between taxis and kinesis?

A

taxis - directional
kinesis - non directional, random movements

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7
Q

what does the prefix rheo- for taxis mean?

A

current

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8
Q

what does the prefix geo- mean ?

A

gravity

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9
Q

what does the prefix chemo- mean?

A

chemical

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10
Q

what advantages does negative phototaxis have for woodlice?

A

less predators
more food sources

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11
Q

what is a stimulus?

A

detectable change in the internal or external environment of an organism that produces a response.

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12
Q

what is trophism?

A

a growth movement of a part of a plant in response to a directional stimulus

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13
Q

what is IAA?

A

an auxin, plant growth factor produced in small quantities
controls cell elongation
causes elongation in shoot cells but inhibits elongation in root cells

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14
Q

where is IAA produced?

A

tips of plant shoots

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15
Q

what is the plant version of taxis?

A

trophism

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16
Q

do shoots grow away from or towards light?

A

towards

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17
Q

plant shoot response to light is called what?

A

phototrophism

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18
Q

name the growth factor produced in the shoot tips which controls a plant shoot’s response to light.

A

IAA

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19
Q

what does IAA do to plant cells in shoots?

A

elongates

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20
Q

if light is distributed around the plant evenly, which direction will the plant grow?

A

upwards

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21
Q

how does IAA distribute itself in plant shoots when light is all around the plant?

A

evenly spread across the tip

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22
Q

if light is on one side, which direction will the shoot grow?

A

towards the light

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23
Q

if light is on one side of the plant, where will IAA accumulate?

A

on the shaded side

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24
Q

what is the root’s response to gravity?

A

positive geotrophism (towards / with force of gravity)

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25
Q

what 2 types of trophism do plant shoots have?

A

negative geotrophism
positive phototrophism

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26
Q

what does IAA do in roots?

A

inhibits elongation

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27
Q

what does IAA do in shoots?

A

encourages elongation

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28
Q

what trophism do roots portray?

A

positive geotrophism
negative phototrophism

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29
Q

what does IAA do to cell elongation in roots?

A

reduces

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30
Q

what does IAA do to cell elongation in shoots?

A

increases

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31
Q

where does growth happen in a shoot?

A

the shoot tip

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32
Q

what is a growth movement of a part in a plant in response to a directional stimulus called?

A

trophism

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33
Q

what would growth look like on a shoot if we covered the tip with foil etc.?

A

growth straight up
because the light is spread evenly across the tip

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34
Q

what would growth look like if i cut off the root tip?

A

hardly any growth
growth happens at the root tip

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35
Q

what are the receptors located mainly in the fingers, soles of feet and genitalia called?

A

the pacinian corpuscle

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36
Q

what do the pacinian corpuscle respond to change in?

A

mechanical pressure (pressure/vibrations)

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37
Q

what are the layers surrounding the sensory nerve ending in the pacinian corpuscle called?

A

lamellae

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38
Q

what happens when a stimulus is applied to the lamellae of the pacinian corpuscle?

A

layers change shape
sodium ions diffuse into cell

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39
Q

what are the Na+ channels in the pacinian corpuscle called?

A

stretch-mediated Na+ channels

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40
Q

How does applying pressure to the pacinian corpuscle produce changes in membrane potential?

A

distorts the layers of lamellae
Na+ channels open
as more pressure is applied, more Na+ channels open
depolarises membrane

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41
Q

what do photoreceptors detect?

A

light

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42
Q

what is light absorbed by in the eye?

A

pigments in photoreceptors

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43
Q

what does the absorption of light cause in the eye?

A

a chemical change
alters membrane permeability to Na+
results in depolarisation of the membrane

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44
Q

what happens in the eye if threshold is reached by depolarisation?

A

impulse is sent along the bipolar neurone and finally to the optic nerve

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45
Q

what are the two types of photoreceptor called in the eye?

A

rods
cones

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46
Q

where are rod cells mainly found within the eye?

A

periphery

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47
Q

where are rod cells absent from?

A

fovea and blind spot

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48
Q

where are cone cells mainly concentrated in the eye?

A

fovea

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49
Q

where are there little to no cone cells?

A

periphery

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50
Q

where are there no cone cells?

A

blind spot

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51
Q

which type of photoreceptor exhibits retinal convergence

A

rod cell

52
Q

what does retinal convergence mean?

A

multiple photoreceptors connected to a single bipolar neurone

53
Q

what do rod cells allow us to see?

A

low light intensities
in black and white

54
Q

why can we see low light intensities due to rod cells?

A

rods each detect small quantities of light
due to retinal convergence, all stimuli from each rod cell (attached to the same BP neurone) added together to generate action potential

55
Q

what is the myelin sheath?

A

covers the axon and is made up of the membranes of the schwann cells wrapped around a neurone which helps speed up impulse transmission

56
Q

what are the nodes of ranvier?

A

constrictions between adjacent schwann cells where there is no myelin sheath

57
Q

what is the axon?

A

a single long fibre that carries nerve impulses away from the cell body

58
Q

what does the pacinian corpuscle respond to changes in?

A

pressure

59
Q

where are the light receptors of the eye found?

A

retina

60
Q

what do light receptors do?

A

convert light energy into nervous impulses

61
Q

why does vision using the fovea have a high visual acuity?

A

cone cells in the fovea do not display retinal convergence

62
Q

what is the pigment in rod cells which is sensitive to low light intensities?

A

rhodopsin

63
Q

which type of photoreceptor is found in the periphery of the retina?

A

rod cells

64
Q

what is the process that allows us to see low light intensities via rod cells called?

A

summation

65
Q

what is the pigment called in rod cells?

A

rhodopsin

66
Q

which type of photoreceptor is mostly concentrated in the fovea?

A

cone cells

67
Q

what is visual acuity?

A

how sharp the image is

68
Q

what is rod cells’ visual acuity like? why?

A

poor due to retinal convergence

69
Q

do cone cells exhibit retinal convergence?

A

no

70
Q

why is cone cells’ sensitivity low?

A

no retinal convergence

71
Q

what light intensity do cone cells detect?

A

high

72
Q

which type of cell contains the pigment that allows us to see in colour?

A

cone cells

73
Q

what is the pigment called in cone cells which allows us to see in colour?

A

iodopsin

74
Q

what are the three types of iodopsin?

A

red, green, blue

75
Q

what is cone cells’ visual acuity like? why?

A

high
no retinal convergence

76
Q

which type of photoreceptor can detect low light intensities?

A

rod cells

77
Q

which type of photoreceptor can detect colour?

A

cone cells

78
Q

which type of cell in the eye has a higher sensitivity?

A

rod cell

79
Q

which type of photoreceptor has a single cell attached to a single bipolar neurone?

A

cone cell

80
Q

what does myogenic mean?

A

the contraction of the muscles is initiated by the muscle itself rather than outside nervous impulses.

81
Q

what is the SAN?

A

a group of cells found in the right atrium
stimulus for contraction
determines the beat of the heart

82
Q

what are the steps in contraction of the heart?

A
  1. SAN sends out nervous impulses across the atria
  2. both atria contract at the same time
  3. AVN receives nerve impulses - short delay to ensure atria are emptied.
  4. AVN sends impulses down the Bundle of His
  5. Impulses transmitted to purkinje fibres which trigger ventricle to contract from the apex (bottom) upwards.
83
Q

where is the SAN located?

A

in the right atrium.

84
Q

which heart chambers contract first after impulses are sent by the SAN?

A

atria

85
Q

which group of cells pick up the waves of electrical activity and delays it slightly?

A

AVN

86
Q

why is the slight delay important from the AVN?

A

to ensure atria are empty

87
Q

which muscle fibres conduct the electrical impulses down the centre of the ventricles to the apex?

A

bundle of His

88
Q

the bundle of His branch out to form what fibres which carry the electrical waves across the ventricular walls?

A

purkinje fibres

89
Q

how does the heart control and co-ordinate the regular contraction of the atria and ventricles?

A
  1. SAN generates electrical impulses
  2. Spreads across both atria - triggers contraction
  3. AVN receives impulses - delays it to enable atria emptying
  4. impulses travel down the bundle of His to the apex of the heart
  5. Purkinje fibres trigger the ventricles to contract from the apex upwards
  6. blood pumped to arteries
90
Q

where are chemoreceptors located?

A

Near the baroreceptors in structures called the carotid and aortic bodies, which respond to changes in carbon dioxide (pH) in the blood.

91
Q

what is the peripheral nervous system made up of?

A

the neurones that connect the CNS to the rest of the body.

92
Q

what two different systems make up the peripheral nervous system?

A

somatic and autonomic nervous systems

93
Q

what does the somatic nervous system control?

A

conscious activities eg. running, playing video games.

94
Q

what does the autonomic nervous system control?

A

unconscious activities eg. digestion

95
Q

what is the nervous system split into?

A

sympathetic and parasympathetic nervous systems

96
Q

what does the sympathetic nervous system do?

A

get the body ready for action (fight or flight system)

97
Q

what does the parasympathetic nervous system do?

A

calms the body down (rest and digest system)

98
Q

which nervous system is involved in the control of heart rate?

A

autonomic nervous system

99
Q

what are changes to heart rate controlled by?

A

region of the brain called medulla oblongata

100
Q

how many centres of the brain are concerned with the control of heart rate?

A

2

101
Q

what is the centre of the brain which increases heart rate linked to?

A

the SAN via the sympathetic nervous system

102
Q

what is the centre of the brain which decreases heart rate linked to?

A

the SAN via the parasympathetic nervous system

103
Q

where are the chemoreceptors and baroreceptors located?

A

in the walls of the aorta and carotid arteries.

104
Q

what do chemoreceptors detect?

A

changes in blood pH (due to changes in carbon dioxide conc.)

105
Q

what does a high concentration of carbon dioxide in the blood do to blood pH?

A

lowers (more acidic)

106
Q

what do baroreceptors detect?

A

changes in blood pressure

107
Q

what are the steps to increase heart rate if pH is too low?

A
  1. exercise or stress increases carbon dioxide levels in the blood (lowers pH)
  2. detected by chemoreceptors - send impulses to medulla oblongata
  3. Medulla oblongata sends impulses via sympathetic nervous system to SAN.
  4. SAN increases heart rate
  5. more blood is pumped to lungs - more carbon dioxide is removed
  6. blood pH rises to normal
108
Q

how do we decrease heart rate if blood pressure is too high?

A

If high blood pressure is detected, more impulses are sent from the baroreceptors to the medulla – this will send more impulses down parasympathetic neurones. This stimulates release of acetylcholine, which decreases heart rate.

109
Q

what is the medulla oblongata?

A

a section of the brain that controls autonomic functions, such as digestion, heart rate and breathing.

110
Q

how do we increase heart rate if blood pressure is too low?

A

if low blood pressure is detected, baroreceptors send more impulses to the medulla, more impulses are sent to the SAN via sympathetic nervous system. This stimulates release of noradrenaline, which increases heart rate and strength of contraction.

111
Q

what happens to decrease heart rate if blood pH is too high?

A

If these changes are detected, more impulses are sent from the chemoreceptors to the medulla – this will send the impulse down parasympathetic neurones. The heart rate will slow to return the oxygen, carbon dioxide and pH of the blood to normal levels

112
Q

what part of the brain controls heart rate?

A

medulla oblongata

113
Q

what type of receptor detects changes in blood pressure?

A

baroreceptor

114
Q

what type of receptor detects changes in pH composition of blood?

A

chemoreceptor

115
Q

under what circumstances would a fall in blood pH take place?

A

carbon dioxide levels are too high

116
Q

where are the two types of receptors which help control heart rate located?

A

wall of the carotid arteries and aorta

117
Q

which branch of the autonomic nervous system would act to increase heart rate?

A

sympathetic nervous system

118
Q

which branch of the autonomic nervous system would act to decrease heart rate?

A

parasympathetic nervous system

119
Q

which branch of the autonomic nervous system would act in response to a blood pH value HIGHER than normal? What would the effect be on heart rate and composition of blood?

A

sympathetic nervous system
heart rate increase
carbon dioxide levels in blood decrease

120
Q

What are plant growth factors and where are they produced?

A
  • Chemicals that regulate plant growth response to directional stimuli.
  • Produced in plant growing regions (apical meristems)
  • Diffuse from cell to cell/ phloem mass transport
121
Q

Many organisms respond to temperature and humidity via kinesis rather than taxis. Why?

A

Less directional stimuli; often no clear gradient from one extreme to the other.

122
Q

what are the advantages of a simple reflex.

A
  1. Rapid response to potentially dangerous stimuli since only 3 neurons involved
  2. instinctive
123
Q

what features are common to all sensory receptors?

A
  • Act as energy transducers which establish an action potential
  • respond to specific stimuli
124
Q

state the formula for cardiac output.

A

cardiac output (CD) = stroke volume (V) x heart rate (R)

125
Q

state the difference between the sympathetic and parasympathetic nervous system.

A

Sympathetic involved in ‘fight or flight’ response: stimulates effectors to speed up activity.
Parasympathetic involved in normal resting conditions: inhibits effectors to slow down activity.

Biology A2 content (19 decks)

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