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A-Level Biology > Internal and External Stimuli > Flashcards

Internal and External Stimuli Flashcards

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1
Q

What is the order for stimuli response?

A 
Stimuli
Receptor
CNS
Effector
Response
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2
Q

What is the CNS made up of?

A

Brain

Spinal cord

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3
Q

What re the two effectors?

A 
Muscle= nervous
Gland = hormonal
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4
Q

What is a stimulus?

A

Detectable change in the eternal or external environment

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5
Q

What is a receptor?

A

Any structure able to respond to a change

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6
Q

What is a coordinator?

A

The “switchboard” connecting information from the receptor to appropriate effector

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7
Q

What is an effector?

A

Causes a response (muscle or gland)

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8
Q

What is a response?

A

The output/change in behaviour

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9
Q

What are the three type of responses?

A

Tactic (taxis)
Kinetic (kinesis)
Trophic (tropism)

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10
Q

How do organisms react to an stimulus in their environment differently?

A

Whole organism or only part of it moves in response

Movement could be directional (+/-) or non-directional

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11
Q

Describe a kinetic response

A

Whole organism
Alteration in rate of movement
In response to change in intensity of stimulus
Non-directional

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12
Q

What is an example of a kinetic response?

A

When in dry conditions woodlice move rapidly and change direction
In drier areas = slow

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13
Q

Describe a taxis response

A

Whole organism
Directed by stimuli
Positive taxis = towards (+)
Negative taxis = away (-)

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14
Q

What is an example of a taxis response?

A

Some species of bacteria move away from waste products they produce
(Negative taxis)

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15
Q

Describe a trophic movement

A

Movement of part of the organism
Directed by stimulus
Growth response

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16
Q

What is an example of a trophic response?

A

Plant roots grow away from light and towards gravity

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17
Q

What are the three type of tropisms?

A

Hydrotropism
Geotropism
Phototropism

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18
Q

Where are auxins produced?

A

Apical meristem

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19
Q

What do auxins do?

A

Cause cells to grow

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20
Q

What is IAA?

A

Example of auxin

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21
Q

What do auxins do in response to tropism?

A

They move to shaded side = causes uneven growth = cell elongation towards sun

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22
Q

Where is IAA made?

A

By cells located throughout plant (not organs)

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23
Q

What is IAA produced in?

A

Small quantities

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24
Q

What does IAA affect inside of the plant?

A

Tissues close by + tissues the are released from

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25
Q

What does IAA affect overall?

A

Growth

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26
Q

What is the CNS?

A

Central nervous system

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27
Q

What is the PNS?

A

Peripheral nervous system

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28
Q

What is the peripheral nervous system

A

Pairs of nerves from the CNS travelling to limbs + organs (sensory neurone)

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29
Q

What are the two main divisions of the PNS?

A

Somatic - conscious = involves brain

Autonomic - subconscious = reflex actions

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30
Q

What is a reflex?

A

Involuntary response to a stimuli

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31
Q

What are the importance of reflexes?

A 
Fast
Automatic
Protective
Innate (not learnt)
Doesn't involve the brain
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32
Q

Why is it important that reflexes are fast, etc?

A

Brain can focus on other complex behaviours

Escape predators, gain food or mates

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33
Q

Describe the process of a reflex arc

A

Sensory neurone takes electrical message from receptor to immediate neurone
Intermediate neurone relays message to motor from sensory
Motor receives from intermediate and sends to effector (muscle)
Muscle will contract so that hands pulls away from stimuli

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34
Q

What do receptors do?

A

Receive info + pass to CNS

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35
Q

Are receptors specific?

A

YES

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36
Q

What is sensory perception?

A

Making sense of information

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37
Q

What must happen to sensory information?

A

Must be converted into info the body understands

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38
Q

What converts sensory information?

A

Transducers

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39
Q

Why is the Pacinian Corpuscle important?

A

It is specific
Involved in sensory reception
Involves in sensory perception

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40
Q

What does the Pacinian Corpuscle respond to?

A

Mechanical pressure

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41
Q

Where is the Pacinian Corpuscle found?

A

Deep skin

eg. Fingers, toes, external genitalia + ligaments/tendons

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42
Q

What does the Pacinian Corpuscle act as?

A

Transducer

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43
Q

What is structure of the Pacinian Corpuscle?

A 
Layers of connective tissue
Viscous gel
Blood capillaries (transports O2 + glucose for respiration = release energy)
Neurone endings
Sensory neurone  (send message to CNS)
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44
Q

What happen when pressure is applied to the Pacinian Corpuscle?

A

Lamellae deforms
Applies pressure to neurone endings
Na channels stretch (stretch mediated Na channels) so Na+ can pass through
Increases permeability of membrane
Na+ move from high to low conc
Via facilitated diffusion
Influx of Na+ changes potential
Once at rest channels change back to normal size
Generator potential results in nervous response

45
Q

What are the two light receptors in the eye?

A

Rod cells

Cone cells

46
Q

What do both receptors in the eye act as?

A

Transducers

47
Q

What do both receptors in the eye do?

A

Convert light energy into electrical energy of a nerve impulse

48
Q

How do the receptors in the eye work?

A

Contain a specific pigment
Pigment broken down by specific wavelength of light
High/low light intensity
IF broken down message will be sent

49
Q

Where are rod cells most numerous?

A

Side of the eye

50
Q

Where are cone cells must numerous?

A

Fovea

51
Q

What pigment is present in rod cells?

A

Rhodopsin

52
Q

What pigment is present in cone cells?

A

3 different idopsin = green, red + blue light

53
Q

What colour image does rod cells produce?

A

Black and white

54
Q

What colour image does cone cells produce?

A

Coloured

55
Q

What light intensity is rod cells’ pigment broken down in?

A

Low

56
Q

What light intensity is cone cells’ pigment broken down in?

A

High

57
Q

What is the visual acuity of rod cells?

A

Low

58
Q

What is the visual acuity of cone cells?

A

High

59
Q

How many neural connections do rod cells have?

A

Multiple

60
Q

How many neural connections do cone cells have?

A

One = own bipolar cell

61
Q

Pigment inside rod cells should be broken down but what else?

A

Threshold value must be exceeded

Ensures generator potential reached

62
Q

What are disadvantages of rod cells?

A

Only generates one impulse regardless of multiple
Cannot distinguish between different sources of light
Low visual acuity

63
Q

What are the two nodes that control the heart?

A

Sinoatrial (SAN)

Atrioventricular (AV)

64
Q

What do the two nodes together do?

A

Iniate the cardiac cycle

65
Q

Describe what happens in the cardiac cycle

A

Electrical impulse spreads across atria from SAN = atria contracts
Atrioventricular septum (non-conductive tissue) stops impulse from travelling to the ventricles
Electrical activity travels to AVN
After a pause the AVN sends an impulse down the bundle of His
The bundle of His conducts the impulse through AV septum to bottom of ventricle
Punkinje fibres (smaller fibres) continue throughout ventricle wall
Ventricle contracts from base up

66
Q

What node is considered the natural pacemaker and why?

A

SAN because it iniated contraction of atria

67
Q

What is importance of the Punkinje fibres>?

A

Smaller branching network which sends nerve impulses to cells in the ventricles of heart

68
Q

Where is the electrical impulse sent once it reaches the AV node?

A

Bundle of His

69
Q

Where does the ventricle contract from and why is this important?

A

Apex (base) = more muscle in the ventricle walls to increase the pressure + push blood further

70
Q

Why is there a short delay before the electrical wave leaves the AVN?

A

Makes sure the atria has emptied before the ventricles contract

71
Q

What is the autonomic system?

A

All internal systems in the body needed to be controlled + regulated

72
Q

What is the peripheral nervous system?

A

Pairs of nerves from the CNS travelling to limbs + organs

73
Q

Is autonomic voluntary or involuntary?

A

Involuntary

74
Q

Is somatic voluntary or involuntary?

A

Voluntary

75
Q

What is the sympathetic N.S primary process?

A

To stimulate body’s fight mode

76
Q

When does the sympathetic N.S stimulate effectors?

A

During strenuous activities

Powerful emotions

77
Q

When does the sympathetic N.S increase in activity?

A

Times of stress, illness or injury

78
Q

Why is the sympathetic N.S constantly active at basic levels?

A

To maintain homeostasis

79
Q

Because the sympathetic N.S stimulates what does it do?

A

Speeds up activities

80
Q

What does sympathetic N.S do for the body?

A

Heighten awareness’
Prepare for action
Help cope with stressful situations

81
Q

Because the parasympathetic inhibits effectors what does it do?

A

Slows activity

82
Q

When does the parasympathetic N.S control activities?

A

Under normal resting conditions

83
Q

What does the parasympathetic N.S deal with?

A

Conserving energy + replenishing the body’s resting reserves

84
Q

When is the parasympathetic N.S active?

A

State of relaxation

= Sleep/recovery from illness or injury

85
Q

What is the parasympathetic N.S primary process?

A

To enable the body to “Rest and Digest”

86
Q

What is the medulla?

A

A cone-shaped neurone mass

87
Q

What is the medulla responsible for?

A

Involuntary functions

88
Q

What does the medulla control?

A

Breathing
Heart rate
Blood pressure

89
Q

What centres does the medulla contain?

A

Cardiac
Respiratory
Vomiting

90
Q

What are the two type of receptors when controlling heart rate?

A

Chemoreceptors

Pressure receptors

91
Q

What does chemoreceptors detect?

A

pH changes in the blood

92
Q

Where are the chemoreceptors found?

A

Carotid arteries

93
Q

What does pressure receptors detect?

A

Pressure changes in the blood

94
Q

Where are pressure receptors found?

A

Carotid arteries

Aorta

95
Q

The centre, in the brain, that increases HR is linked to what?

A

SAN by sympathetic N.S

96
Q

The centre, in the brain, that decreases HR is linked to what?

A

SAN by parasympathetic N.S

97
Q

What happens when blood pressure is high?

Pressure receptors

A

Nervous impulse sent to centre of medulla (decreases HR)
Centre sends impulse via parasympathetic N.S to SAN
Decreases HR

98
Q

What happens when blood pressure is low?

Pressure receptors

A

Nervous impulse sent to centre of medulla (increases HR)
Centre receives impulse via sympathetic N.S to SAN
Increases HR

99
Q

How do chemoreceptors work?

A 
Increased metabolic activity
More CO2 = pH decreases
Chemoreceptors increase impulses to centre of medulla that increase HR
Via sympathetic NS to SAN 
HR increases = blood flow increases 
More CO2 removed 
pH rises to normal
100
Q

What is a feedback loop?

A

The automatic control system resulting in a return to normal conditions

101
Q

`What is the feedback loop of chemoreceptors?

A 
Change in blood pH = stimuli
(Chemo)receptors in carotid arteries
Coordinate centre co-ordinates a response (medulla)
Effector brings about response (heart) 
Response returns HR back to normal
102
Q

What effect does IAA have on growth of roots?

A

Inhibits growth

103
Q

Why does vision using the fovea has a high visual acuity

A

Lots of cones cells present

Each cone cell has its own neurone

104
Q

How does a high conc of IAA at the bottom of the root cause it to bend?

A

High conc at bottom so cell only grow at the top, causing it to bend downwards

105
Q

What is the term used to describe the sharing of one neurone by multiple rod cells?

A

Retinol convergence

106
Q

By which process do plant hormones move from growing regions of a plant to other tissues?

A

Diffusion

107
Q

How is action potential generated in the Pacinian Corpuscle?

A

Applies pressure which deforms tissues
This widens stretch mediated Na channels
Causes influx of Na+ into membrane
Changes the potential

108
Q

What is the role of the bundle of His

A

To conduct electrical message from the AV node to the apex of the heart down the non-conductive septum

109
Q

What is the role of the medulla oblongta

A

Involuntary responses

A-Level Biology (21 decks)

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