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AQA A level Biology > 6.1 Stimuli and response > Flashcards

6.1 Stimuli and response Flashcards

1
Q

What is meant by phototropism

A

A directional growth in response to light

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2
Q

What is meant by gravitropism

A

A directional growth in response to gravity

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3
Q

When there’s directional growth towards a stimuli, is the tropism positive or negative

A

Positive

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4
Q

When there’s directional growth away from a stimuli, is the tropism positive or negative

A

Negative

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5
Q

Describe where IAA is produced

A

In the tops of roots and shoots

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6
Q

When IAA is present in the shoots what does it promote

A

Growth

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7
Q

When IAA is present in the shoots, what does it cause to happen to the cells

A

Causes cell elongation

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8
Q

When IAA is present in the roots, what is inhibited

A

Growth

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9
Q

What causes the movement of IAA in shoots

A

Light

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10
Q

Since IAA is moved by light, what happens when the side of the plant is in the shade

A

IAA diffuses to the shady side of the shoot

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11
Q

If IAA diffuses to the shady side of the shoot, what does the lead too

A

The build up of IAA concentration on the shady side compared to the light side

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12
Q

Since the concentration of IAA is higher on the shadier side, what does this cause

A

It promotes cell elongation and growth, so more of these 2 processes occur on the shadier side compared to the light side

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13
Q

When there’s increased growth and cell elongation on the shadier side of the shoot, what does this lead too

A

The shoot bending towards the light

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14
Q

When the shoot bends towards the light, what is the name of this

A

Positive phototropism

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15
Q

Explain how IAA causes positive phototropism in shoots ( 6 points)

A
  • IAA is produced in the tip of the shoot, initially it is evenly transported to all regions as it begins to move down the shoot
  • Light causes the movement of IAA
  • IAA diffuses to the shady side of the shoot. A greater concentration builds up on this side than the light side
  • Here it promotes cell elongation and growth occurs more on this side
  • The shoot bends towards the light
  • Called positive phototropism
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16
Q

What influences the movement of IAA in the roots

A

Gravity

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17
Q

In the roots, what side of the root will gain a greater concentration of IAA

A

The lower side

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18
Q

When the IAA accumulates on the lower side of the root, what happens

A

The IAA inhibits the elongation of the root cells, so the cells on the lower side of the root elongate less than the upper side

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19
Q

When the cells on the upper side of the root elongate more, what does this lead to

A

Causes the root the bend downwards towards gravity

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20
Q

When the root bends downwards towards gravity, what is the name of the process

A

Gravitotropism

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21
Q

Explain how IAA causes positive gravitropism in roots (5 points)

A
  • Cells in the top of the root produce IAA. It is initially transported to all sides of the root
  • Gravity influences the movement of IAA from the upper side of the root to the lower side of the root
  • A greater concentration of IAA builds up on the lower side
  • In the roots IAA inhibits the elongation of root cells, the cells on the lower side elongate less than the upper side
  • This causes the root to bend downwards towards gravity, and it positive gravitopism
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22
Q

What is a taxis

A

A directional response to a stimulus

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23
Q

If the whole organism moves away from the stiumuli, is the taxis positive or negative

A

Negative taxis

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24
Q

If the whole organism moves towards the stimuli, is the taxis positive or negative

A

Positive taxis

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25
Q

What is a kinesis

A

When an organism changes the speed and the rate in changes in direction to find a more favourable environment

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26
Q

What are reflexes

A

Rapid involuntary responses

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27
Q

What are the roles of reflexes

A
  • Protect against damage to body tissues
  • Enable homeostatic control
  • Enable escape from predators
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28
Q

A simple reflex arc only involves how many neurones

A

3

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29
Q

What is the role of sensory neurones

A

To carry electrical nerve impulses from the receptor to the central nervous system

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30
Q

What do intermediate neurones synapse with

A

Sensory neurones and then with a motor neurone

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31
Q

What are the 7 stages of a reflex arc

A
  • Stimulus
  • Receptor
  • Sensory neurone
  • Coordinator (intermediate nerurone)
  • Motor neurone
  • Effector
  • Response
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32
Q

Explain the features of a sensory neurone

A
  • Respond to one type of stimulus
  • Acts as a tranducter, creating a generator potential
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33
Q

Receptors in the nervous system convert the energy of the stimulus into a nervous impulse, what is this known as

A

A generator potential

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34
Q

Describe the structure of a Pacinian corpuscle

A
  • Single sensory neurone is at the centre of layers of tissue called lamellae each seperated by a gel
  • A capsule surrounds the layers
  • The sensory neurone at the centre has stretch mediated sodium channels in its membrane
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35
Q

In a Pacinian corpuscle, what are the layers of tissue called

A

Lamellae

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36
Q

In the Pacinian corpuscle, what are the layers of tissue (lamellae) separated by

A

A gel

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37
Q

In the Pacinian corpuscle, what type of stretch mediated channel is in the membrane of the sensory neurone at the centre

A

Sodium channels

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38
Q

Explain the stimulus which Pacinian corpuscles respond to

A

Responds to mechanical stimuli such as pressure

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39
Q

What does increased pressure do to the lamellae of the Pacinian corpuscle

A

Deforms the lamellae

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40
Q

When pressure has deformed the lamellae, what does this in turn deform

A

The stretch-mediated sodium ion channels in the membrane of the sensory neurone

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41
Q

When the stretch-mediated sodium ion channels in the membrane of the sensory neurone of the Pacinian corpuscle deforms, what happens to the sodium ion channel, and what does this lead to

A

The sodium ion channels open and sodium ions diffuse in

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42
Q

Once the sodium ions have diffused into the sensory neurone, what happens to the inside of the neurone

A

It becomes more positive

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43
Q

When the inside of the neurone becomes more positive, what is the name of this

A

Depolarisation

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44
Q

What is produced when the inside of the neurone becomes more positive/ depolarisation

A

A generator potential

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45
Q

What is the pigment in rod cones

A

Rhodopsin

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46
Q

What is Rhodopsin in rod cones sensitive to

A

Low light intensity

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47
Q

What is the pigment inside cone cells

A

Iodopsin

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48
Q

Is iodopsin in cone cells sensitive to low light intensity

A

No

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49
Q

Why do rod cells have low visual acuity

A

Because a number of rod cells are connected to a single bipolar neurone. Meaning it will generate a single impulse to the brain regardless of how many neurones are stimulated

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50
Q

A number of rod cells are connected to a single ______ neurone

A

Bipolar

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51
Q

Why are rod cell images only black and white

A

Rhodopsin cannot distinguish between different wavelengths, it is broken down by all wavelengths

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52
Q

In what light intensity can Rhodopsin be broken down in

A

Low light intensity

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53
Q

Why do cone cells have high visual acuity

A

Each cone cell is connected to a single bipolar neurone, meaning that the brain receives separate impulses from each cone cell

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54
Q

In what light can iodopsin be broken down in

A

Broken down in bright light

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55
Q

Why are cone cells sensitive to colour

A
  • There are 3 types of cone cells each with a different type of iodopsin
  • Each type of iodopsin is sensitive to different wavelengths of light
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56
Q

Can stimulation of each cone cell be combined to help reach threshold, and why

A

No as each cone cell has their own bipolar cell

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57
Q

What is a stimulus

A

Any detectable change in environment of organisms that leads to a response

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58
Q

What are the 2 communication systems that result in a response

A
  • Electrical
  • Chemical
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59
Q

What is the name of the system where the communication system is electrical

A

Nervous system

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60
Q

What is the name of the system where the communication system is chemical

A

Endocrine

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61
Q

What are the 5 generic steps from stimuli to a response in both endocrine and nervous system

A
  • Stimuli
  • Receptor
  • Coordinator
  • Effector
  • Response
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62
Q

Receptors are specific to how many different types of stimuli

A

Specific to 1 stimuli

63
Q

What is the name of IAA

A

Indoleactic acid

64
Q

What is the role of IAA

A

Control the plant cell elongation

65
Q

What is the name of the node in the cardiac cycle that sends out regular waves of electrical activity across the atria

A

The sino atrial node

66
Q

What does the sino atrial node sending out regular waves of electrical activity result in

A

The atria contracts

67
Q

In the heart what prevents impulses passing from walls of atria to the ventricles

A

Non-conducting tissue

68
Q

What is the name of the node that detects electrical activity in the atria and then sends out electrical activity to the ventricles

A

Atrioventricular node

69
Q

What is the name of the part of the ventricle where the atrioventricular node sends the electrical activity to

A

The apex of the ventricle

70
Q

What are the name of the smaller fibres in the ventricles, where the impulses travel up

A

The smaller Purkyne fibres

71
Q

When the ventricles contract from which part of the ventricle does the contraction occur from

A

From the apex upwards

72
Q

Explain the events which take place during the cardiac cycle to produce and transmit a wave of electrical activity to make the heartbeat

A
  • The sino atrial node send out regular waves of electrical activity across the atria
  • This causes the atria to contract
  • Non conducting tissue between the atria and ventricles prevents the impulses passing from walls of atria to ventricles
  • This delay ensures the atria is empty of blood before ventricles contract
  • Instead the atrioventricular node is able to detect the electrical activity in the atria and after the delay sends out electrical activity down the bundle of HIS to the apex of the ventricle
  • Impulses travel up the smaller Purkyne fibres and ventricles contract from the apex upwards
73
Q

What is the name of the bundle where the electrical activity get sent down from the atrioventricular node to the apex of the ventricles

A

Bundle of His

74
Q

What does SAN stand for

A

Sino atrial node

75
Q

What does AVN stand for

A

Atrioventricular node

76
Q

The heart can contract without any nervous stimulation, what is the term as to why

A

The heart is myogenic

77
Q

What initiates the sequence of muscle contractions in the heart

A

The sinoatrial node (SAN)

78
Q

Purkyne tissue is initially grouped together in a structure called what

A

Bundle of His

79
Q

What happens to the Purkyne tissue beyond the Bundle of His

A

Branches into smaller fibres

80
Q

What do chemoreceptors detect

A

Changes in carbon dioxide

81
Q

What do pressure receptors detect

A

Changes in pressure

82
Q

Where are chemoreceptors and pressure receptors found

A

In the aorta close to the heart andv in the carotid arteries

83
Q

Where do the carotid arteries pass through

A

The neck to the brain

84
Q

What does the parasympathetic nervous system help the body to do

A

Relax

85
Q

Where is the inhibitory centre and the acceletory centre

A

In the medulla oblongata

86
Q

What does activating the inhibitory centre in the medulla do

A

Sends impulses along the parasympathetic nervous system

87
Q

What type of response does the sympathetic nervous system initiate

A

Fight or flight response

88
Q

What does activiating the acceletory centre in the medulla do

A

Sends impulses along the sympathetic nervous system

89
Q

What happens to the pH when the concentration of carbon dioxide increases

A

The pH falls

90
Q

What are the receptors that detect the change in carbon dioxide levels

A

Chemoreceptors

91
Q

After the chemoreceptors have detected a change in carbon dioxide, what happens

A

The chemoreceptors send impulses to the cardiac centre in the medulla

92
Q

What nervous system is activated when there’s high carbon dioxide concentrations

A

Sympathetic nervous system

93
Q

When there’s high concentrations of carbon dioxide, what does this do to the frequency of impulses sent out by the SAN

A

Increases the frequency

94
Q

When there’s a decrease in the carbon dioxide concentration, what happens to the number of impulses that are sent to the cardiac muscle in the medulla

A

Fewer impulses are sent

95
Q

When there’s a decrease in carbon dioxide what nervous system is activated

A

Parasympathetic nervous system

96
Q

At lower levels are carbon dioxide, what happens to the frequency of impulses sent out by SAN

A

A decrease

97
Q

What is releases at the synapse with the SAN

A

A neurotransmitter

98
Q

What is the name of the centre that the medulla contains

A

Cardio regulatory centre

99
Q

What are the 2 parts of the cardio regulatory centre

A
  • Acceleratory centre
  • Inhibitory centre
100
Q

What is the acceleratory centre responsible for

A

Speeding up the heart rate

101
Q

What is the inhibitory centre response for

A

Slowing down the heart beat

102
Q

What is the coordinator in the nervous system

A

The central nervous system

103
Q

What are the 2 types of nervous systems

A
  • Central
  • Peripheral
104
Q

What are the 2 types of pathways in the peripheral nervous system

A
  • Sensory pathway
  • Motor pathway
105
Q

In the sensory pathway of the peripheral nervous system, do the electrical impulses travel towards or away from the central nervous system

A

Towards the central nervous system

106
Q

In the motor pathway of the peripheral nervous system, do the electrical impulses travel towards or away from the central nervous system

A

Away from the central nervous system

107
Q

What are the 2 types of nervous systems within the motor pathway of the peripheral nervous system

A
  • Somatic (voluntary)
  • Autonomic (Involuntary)
108
Q

What is an example when the somatic nervous system is used

A
  • Walking
  • Skeletal muscles
    -etc
109
Q

What is an example of when the autonomic nervous system is used

A
  • Cardiac muscle
  • Glands
110
Q

What are the names of the 2 divisions from the autonomic nervous system

A
  • Sympathetic division
  • Parasympathetic division
111
Q

What are the 3 mains reasons about the benefit of having simple reflex arcs

A
  • Involuntary response
  • Protects body from harm
  • Fast
  • Don’t have to be taught/ from birth
112
Q

What is the maximum number of neurones in a reflex arc

A

3

113
Q

Why does having a maximum of 3 neurone in the reflex arc make it fast

A

As there’s only 2 synapses, synapses slow the speed

114
Q

Give 2 reasons why reflex arcs are fast

A
  • No decision making
  • Few synapses
115
Q

What is the order from stimuli to response in the nervous system

A
  • Stimuli
  • Receptor in skin
  • Sensory neurone passes nerve impulses to spinal cord
  • Relay neurone pass nerve impulses across spinal cord
  • Motor neurone passes nerve impulses to muscle
  • Effector
  • Response
116
Q

What root does the sensory neurone always go down

A

Down the dorsal (back) root

117
Q

What root does the motor neurone always go down

A

The ventral root

118
Q

What is grey matter, in terms of neurone body

A

Areas where neurones don’t have myelin

119
Q

What is white matter, in terms of neurone body

A

Area where neurones are covering in myelin

120
Q

What are 2 features of receptors

A
  • Specific to single type of stimuli
  • Acts as a transducer to produce a generator potential
121
Q

What do transducers do

A

Changes 1 form of energy into another form

122
Q

What does the Pacinian corpuscle respond to

A

Changes in mechanical pressure

123
Q

In terms of being a transducer, what does the Pacinian corpuscle do

A

Convert mechanical energy into electrical energy which creates a generator potential

124
Q

When pressure is applied to the end of a sensory neurone, what happens

A

The pressure distorts the layers of cells around the neurone. This stretches the membrane of the sensory neurone so the sodium ion channels open. Sodium ions diffuse in. This results in a dipolar membrane which creates a generator potential

125
Q

What are the 2 receptors in the eye

A
  • Rods
  • Cones
126
Q

How many types of rods are there

A

Only 1

127
Q

Are the more rods or cones

A

More rods

128
Q

Are rods found at the periphery of the retina or at the fovea

A

At the periphery of the retina

129
Q

How many types of cones are there

A

3 types each corresponding to different wavelengths of light

130
Q

How are cones distributed in the eye

A

Few at the periphery of retina, concentrated at fovea

131
Q

What does the SAN being myogenic mean

A

Acts independently of nervous system

132
Q

Why is the SAN know as the pacemaker of the heart

A

The SAN starts the heart beat

133
Q

What is the SAN located

A

In the wall of the right atrium

134
Q

Where is the AVN located

A

In the wall of the right atrium

135
Q

With increased respiration, what increases, and what is the effect in the pH of the blood

A

Partial pressure of carbon dioxide increases, so the pH of the blood decreases

136
Q

When there is an increase in partial pressure of carbon dioxide, where do the impulses get sent to

A

The cardioacceleratory centre in the medulla oblongata

137
Q

When there is a decrease in partial pressure of carbon dioxide, where do the impulses get sent to

A

The cardioinhibitory centre in the medulla oblongata

138
Q

What is the role of the SAN

A

To initiate the rhythm of the heart

139
Q

What does the SAN sent out

A

A broad wave of dipolarisation

140
Q

Where does the wave of dipolarisation from the SAN get sent

A

Across both atria

141
Q

What does the wave of dipolarisation sent from the SAN result in

A

The contraction of bot atria, atrial systole

142
Q

After a delay after the SAN sends out a wave of dipolarisation, what does the AVN do

A

Picks up the wave of dipolarisation

143
Q

Once the AVN has picked up the wave of dipolarisation, what happens

A

The AVN transmits electrical activity as an impulse to the apex of the heart, through the Bundle of His

144
Q

What does the Bundle of His do

A

Transmits electrical activity from the AVN to the apex of the heart

145
Q

When the impulse reaches the apex of the heart, what happens

A

The impulse spreads out through a series of fibres (Purkinje fibres)

146
Q

Why is it important that the ventricular contract bottom up

A

To push the blood up and out of the heart through the arteries

147
Q

Why is the delay between the SAN wave and the AVN picking up the wave important

A

To allow the ventricles to fill before ventricular systole

148
Q

What does autonomic mean

A

Self governing

149
Q

What is the word used to describe the relationship between parasympathetic and sympathetic nervous system

A

Antagonistic

150
Q

What is the name of the receptors that detect changes in pressure

A

Baroreceptors

151
Q

When there’s a high blood pressure, what detects that and what is the effect

A

Baroreceptors detects the change in pressure, in high blood pressure the medulla oblongata sends impulses along the parasympathetic pathway which inhibits SAN activity so slows down the heart rate

152
Q

Where there’s low blood pressure, what detects this, and what is the result

A

Barorecpetors detect change in pressure, in low blood pressure the medulla oblongata sends impulses along the sympathetic pathway which increases the frequency of SAN dipolarisation waves which increases the heart rate

153
Q

Exercise causes an increase in heart rate, Describe the role of receptors and of the nervous system in this process (4 marks)

A
  1. Chemoreceptors detect rise in CO2 / H+ / acidity / carbonic acid / fall
    in pH
    OR
    Baro / pressure receptors detect rise in blood pressure;
  2. Send impulses to cardiac centre / medulla;
  3. More impulses to SAN;
  4. By sympathetic (nervous system for chemoreceptors / CO2)
    OR
    By parasympathetic (nervous system for baro/ pressure receptors/ blood pressure)
154
Q

When the heart beats both ventricles contract at the same time. Explain how this is coordinated in the heart after initiation of heartbeat by the SAN (2 marks)

A
  1. Electrical activity only through Bundle of His / AVN;
  2. Wave of electrical activity passes over / through both ventricles at the
    same time;
    For ‘electrical activity’ accept impulses /
    depolarisation / action potential

AQA A level Biology (38 decks)

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