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AQA A Level Biology > Stimuli and Response > Flashcards

Stimuli and Response Flashcards

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1
Q

Why do plants use growth factors?

A

To respond to changes in their environment to increase their chance of survival e.g. towards light to increase the rate of photosynthesis

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2
Q

What is a tropism?

A

The response of a plant to a directional stimulus

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3
Q

How do plants respond to changes in their environment?

A

Growth factors because they dont have circulatory systems or nervous systems

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4
Q

What do auxins (e.g. IAA) do?

A

Cause cell elongation in shoots

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5
Q

What do gibberellins do?

A

Cause flowering and germination

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6
Q

Where are growth factors made?

A

In root and shoot tips

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7
Q

How do growth factors move short distances?

A

By active transport and diffusion

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8
Q

How do growth factors move long distances?

A

In the phloem

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9
Q

How does IAA cause phototropism?

A

IAA moves to the shaded side of the root or the shoot causing: - Shoots: Cells to elongate and grow towards light - Roots: (IAA inhibits cell growth) roots to grow away from light

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10
Q

How does IAA cause gravitropism?

A

IAA moves to the underside of the root or the shoot causing: - Shoots: Cells to elongate and grow against gravity - Roots: (IAA inhibits cell growth) roots to grow with gravity

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11
Q

What are taxes and kineses?

A

Simple responses that keep mobile organisms in favourable environments

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12
Q

What are taxes?

A

Mobile organisms move towards or away from a directional stimulus

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13
Q

What are kineses?

A

Mobile organisms change their movement in response to a non-directional stimulus

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14
Q

Which stimulus’s cause a taxes?

A
  • Predators- Water loss- Heat
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15
Q

How do unfavourable conditions cause a kinesis?

A
  • Move more/faster - Turn more- Allows them to move to a new area
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16
Q

How do favourable conditions cause a kinesis?

A
  • Move less/slower- Turn less- Allows them to remain in a favourable area
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17
Q

What is a reflex?

A

A rapid response to a stimulus without conscious or deliberate control

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18
Q

What is the reflex arc?

A
  • Stimulus - Receptor- Sensory neurone- Relay neurone in CNS- Motor neurone- Effector- Response
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19
Q

What are the advantages of reflexes?

A
  • Help avoid damage- Very fast- Unconscious - Doesn’t need to learnt
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20
Q

What are pacinian corpuscles?

A

They detect pressure, touch and vibrations in the skin

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21
Q

What happens when pacinian corpuscles are stimulated?

A
  • Pressure causes the lamellae to stretch and deform- Stretch mediated sodium ion channels open- Sodium ions diffuse into the neurone- The more sodium ions, the greater the stimulus - Causes depolarisation of the neurone (generator potential)- If threshold is reached then an action potential is initiated
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22
Q

How is light seen by the human eye?

A
  • Light is focused on the retina by the lens- Light is absorbed by the pigments in photoreceptors - Causes sodium ion channels to open (how many depends on the strength) (generator potential)- If threshold met then action potential generated and transmitted along the bipolar neurone to the optic nerve where it is transmitted to the brain
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23
Q

What are the two photoreceptors in the eye?

A

Cone and rod cells

24
Q

Rod cells…

A
  • Detect monochromatic pigments - Are sensitive to low light- Have low visual acuity- Are mostly in peripheral parts of retina- Cannot differentiate the position of light but get an action potential at lower light because many rod cells are joined to one bipolar neurone
25
Q

Cone cells…

A
  • Detect trichromatic pigments - Allow us to see colour vision- Are less sensitive to low light - Have higher visual acuity - Each cone has its own bipolar neurone so position of light can be differentiated but a stronger stimulus is required to reach threshold
26
Q

What is the role of the pulmonary artery?

A

Carries deoxygenated blood from right ventricle to the lungs

27
Q

What is the role of the vena cava?

A

Carries deoxygenated blood from body to the right atria

28
Q

What is the role of the aorta?

A

Carries oxygenated blood from left ventricle to body

29
Q

What is the role of the pulmonary vein?

A

Carries oxygenated blood from lungs to left atria

30
Q

What is the role of the semilunar valves?

A

Open when pressure in ventricles is greater than in blood vessels

31
Q

What is the role of the atrioventricular valves?

A

Open when pressure in atria is greater than ventricles

32
Q

What is the role of the SAN?

A

Initiates heart beat

33
Q

What is the role of the AVN?

A

Delays the impulse, allowing atria to contract before the ventricles

34
Q

What is the role of the bundle of His?

A

Carries the impulse to the Purkyne fibres

35
Q

What is the role of the non-conductive tissue?

A

Stops impulse from SAN reaching ventricles

36
Q

How is heart rate controlled?

A
  • SAN initiates heart beat- Sends an electrical impulse across atria - Causes atria to contract - Non-conductive tissue prevents nerve impulses reaching the ventricles - Impulse arrives at AVN- AVN delays the impulse to allow atria to contract and empty before the ventricles contract- AVN sends impulse down the impulse down the bundle of His to the Purkyne fibres- Causes ventricles to contract from the base up
37
Q

How is the left ventricle different to the right ventricle?

A
  • Highest blood pressure- Most cardiac muscle- Contracts with greatest force- Pumps blood to whole body
38
Q

What happens to the atria during atrial systole?

A

They are contracted and at high pressure

39
Q

What happens to the ventricles during atrial systole?

A

They are relaxed and at low pressure

40
Q

What happens to the atrioventricular valves during atrial systole?

A

Open

41
Q

What happens to the semilunar valves during atrial systole?

A

Closed

42
Q

What happens to the atria during ventricular systole?

A

They are relaxed and at low pressure

43
Q

What happens to the ventricles during ventricular systole?

A

They are contracted and at high pressure

44
Q

What happens to the atrioventricular valves during ventricular systole?

A

Closed

45
Q

What happens to the semilunar valves during ventricular systole?

A

Open

46
Q

What happens to the atria during diastole?

A

They are relaxed and at low filling pressure

47
Q

What happens to the ventricles during diastole?

A

They are relaxed and at low lower pressure

48
Q

What happens to the atrioventricular valves during diastole?

A

Open

49
Q

What happens to the semilunar valves during diastole?

A

Closed

50
Q

What do chemoreceptors detect?

A
  • Changes in blood oxygen conc- Changes in blood carbon dioxide conc - Changes in pH
51
Q

What do baroreceptors detect?

A
  • Changes in blood pressure
52
Q

What happens when a chemoreceptor detects high blood oxygen conc, low blood carbon dioxide conc or high pH?

A

1 - Receptor sends nerve impulses to the medulla oblongata in the brain2 - Medulla oblongata sends a nerve impulse along the parasympathetic nervous system3 - Parasympathetic nervous system secretes acetylcholine4 - Acetylcholine is detected by the SAN5 - Heart rate slows down

53
Q

What happens when a chemoreceptor detects low blood oxygen conc, high blood carbon dioxide conc or low pH?

A

1 - Receptor sends nerve impulses to the medulla oblongata in the brain2 - Medulla oblongata sends a nerve impulse along the sympathetic nervous system3 - Parasympathetic nervous system secretes noradrenaline4 - Noradrenaline is detected by the SAN5 - Heart rate speeds up

54
Q

What happens when baroreceptors detect high blood pressure?

A

1 - Receptor sends nerve impulses to the medulla oblongata in the brain2 - Medulla oblongata sends a nerve impulse along the parasympathetic nervous system3 - Parasympathetic nervous system secretes acetylcholine4 - Acetylcholine is detected by the SAN5 - Heart rate slows down

55
Q

What happens when baroreceptors detect low blood pressure?

A

1 - Receptor sends nerve impulses to the medulla oblongata in the brain2 - Medulla oblongata sends a nerve impulse along the sympathetic nervous system3 - Parasympathetic nervous system secretes noradrenaline4 - Noradrenaline is detected by the SAN5 - Heart rate speeds up

56
Q

What neurotransmitter is secreted by the parasympathetic nervous system?

A

Acetylcholine

57
Q

What neurotransmitter is secreted by the sympathetic nervous system?

A

Noradrenaline

AQA A Level Biology (13 decks)

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