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Biology Paper 2 > B14 - Response to stimuli > Flashcards

B14 - Response to stimuli Flashcards

1
Q

Define a taxis.

A

A response in which the direction of the stimulus determines the direction.

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2
Q

Give an example of a taxis.

A

Algae which moves towards light. This increases their chance of survival as they require light to photosynthesize.
Earthworms: move away from light, which leads them to soil to find better nutrients and safety.

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3
Q

Define a kinesis.

A

Change of speed in turning direction. The faster an organism turns, the more likely it is to find a favourable environment.

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4
Q

Give an example of a kinesis.

A

Woodlice - they will more rapidly change direction when in a dry area in order to try and find a damp one.

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5
Q

Define a tropism

A

Growth of a plant in response to a directional stimulus.

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6
Q

Give an example of a plant growth factor.

A

IAA (Indoleacetic Acid)

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7
Q

Phototropism: Which part of the plant produces IAA?

A

Cells in the tip

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8
Q

Which area does light cause IAA to move?

A

Towards the shaded side.

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9
Q

Phototropism: Which direction does the shoot bend towards?

A

Towards the light, as the plant has elongated on the shady side due to a higher IAA concentration.

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10
Q

Gravitropism: Which side does gravity influence IAA?

A

Forces the IAA to the lower side of the root

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11
Q

What is the Central Nervous System [CNS]?

A

Brain and Spinal Chord

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12
Q

What is the reflex sequence?

A

Stimulus, receptor, sensory, intermediate, motor, effector, response

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13
Q

What is the importance of reflex arcs?

A

Involuntary, protect the body from harm, they are fast, rapid.

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14
Q

Where are Pacinian Corpuscles found?

A

Deep in the skin

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15
Q

Describe the structure of a Pacinian Corpuscle.

A

A single sensory neuron at the centre of layers of tissue.

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16
Q

What is located in the membrane of the Corpuscle?

A

Stretch-mediated sodium channels. These allow Na+ ions to enter only when they are stretched and deformed [as a result of external pressure]

17
Q

What is produced by the sudden influx of sodium ions [Pacinian Corpuscle]?

A

A generator potential as the potential of the membrane is changed.

18
Q

What colours do Rod cells pick up?

A

Black and white, as they are unable to detect other wavelengths.

19
Q

What light intensity are rod cells to pick up?

A

Low intensity

20
Q

How do rod cells create a generator potential?

A

Rhodopsin must be broken down, and the energy from low light intensity causes this.

21
Q

Why do rod cells give low visual acuity?

A

The brain cannot distinguish between the separate sources of light as many rod cells can share the same neuron.

22
Q

Are there more cone or rod cells?

A

Rod cells.

23
Q

What pigment do cone cells contain?

A

Iodopsin, which requires a higher light intensity to break down.

24
Q

Where on the eye are cone cells most concentrated?

A

Fovea (the centre)

25
Q

What is the sympathetic nervous system?

A

The fight or flight response

26
Q

What word describes the behaviour of the sympathetic and parasympathetic nervous systems?

A

Antagonistic - normally oppose one another

27
Q

What is the parasympathetic nervous system?

A

‘Rest and digest’

28
Q

Where is the Sinoatrial Node located?

A

The right atrium

29
Q

What does the SAN do?

A

Releases a wave of depolarisation across the atria, which therefore contracts.

30
Q

What does the Atrioventricular Node (AVN) do?

A

Releases another wave

31
Q

Why doesn’t the wave travel through the atria to the ventricle?

A

There is a non-conductive layer between the atrium and ventrcile.

32
Q

What is Purkyne tissue?

A

Specialised muscle fibres which conveys a wave of electrical excitation.

33
Q

What is the Bundle of His?

A

All of the collective Purkyne tissue.

34
Q

What is the function of the Bundle of His?

A

Conducts the wave through the atrioventricular septum to the base of the ventricles.

35
Q

Where are chemoreceptors found?

A

In the wall of carotid arteries and aorta

35
Q

What is the medulla oblongata?

A

Controls change in heart rate, which has two centres.

36
Q

What do chemoreceptors do?

A

Increases the frequency of impulses to the medulla oblongata.

37
Q

What do pressure receptors do?

A

Sensitive to blood pressure:
High = decrease the heart rate via parasympathetic
Low = increase HR via sympathetic.

Biology Paper 2 (7 decks)

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