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A-level Biology > 14 - Response to Stimuli > Flashcards

14 - Response to Stimuli Flashcards

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1
Q

What is the basic sequence of events beginning with a stimulus?

A

Stimulus, Receptor, Coordinator, Effector, Response

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2
Q

Name a plant growth factor.

A

Indoleacetic acid (IAA)

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3
Q

Where is IAA produced?

A

Tips of roots and shoots

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4
Q

How does IAA cause positive phototropism in shoots?

A

IAA moves from illuminated side to shaded side
Higher concentration on shaded side cause faster rate of cell elongation
Shoot bends towards light

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5
Q

How does IAA cause positive gravitropism in roots?

A

Gravity influences IAA to move from upper side to lower side of root.
Cells on upper side elongate more as IAA inhibits cell elongation in roots
Root bends downwards.

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5
Q

How does IAA cause positive gravitropism in roots?

A

Gravity influences IAA to move from upper side to lower side of root.
Cells on upper side elongate more as IAA inhibits cell elongation in roots
Root bends downwards.

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6
Q

What kinds of organisms display taxes and kineses? Give an example.

A

Organisms without complex nervous systems. For example, flatworms.§

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7
Q

What is the purpose of taxes and kineses?

A

Enable organisms to stay in a favourable environment.

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8
Q

What is a kineses?

A

A non-directional response to a stimulus, affected by the intensity of the stimulus.

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9
Q

What is a taxis?

A

A directional response to a stimulus.

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10
Q

Give three types of neurone.

A

Sensory, relay (intermediate), motor

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11
Q

How many neurones does a reflex arc involve?

A

3

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12
Q

Describe the reflex arc pathway.

A

Stimulus, Receptor, Sensory, Relay, Motor, effector, Response

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13
Q

What stimulus does the Pacinian corpuscle respond to?

A

Mechanical pressure

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14
Q

How does the Pacinian corpuscle function?

A
  • When pressure is applied, stretch mediated sodium ion channels open
  • Sodium ions diffuse in
  • This establishses an electrical potential difference (depolarisation)
  • Which causes a generator potential
  • Causing an action potential
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15
Q

Name two receptors in human eyes.

A

Rods
Cones

16
Q

What pigment is broken down in rod cells?

A

Rhodopsin

17
Q

What pigment is broken down in cone cells?

A

Iodopsin

18
Q

What is visual acuity?

A

The ability to distinguish separate points.

19
Q

How do eye receptors work?

A

When hit by light, pigment breaks down

20
Q

Describe the connection pathway between rods and the optic nerve.

A

Multiple rods connect to one bipolar cell
Multiple bipolar cells synapse to a sensory neurone on the optic nerve

21
Q

How are cones connected to the optic nerve?

A

One cone connects to one bipolar cell
Connecting to a single sensory neurone

22
Q

How is summation used in rod cells? What kind of summation is this?

A

Multiple stimulated rods generate a sufficient generator potential to react the threshold
So a less sharp image is formed, but can be seen in lower light Spatial.

23
Q

What does myogenic mean?

A

Occurs without external stimulation

24
Q

Describe the process of heart contraction. (6)

A

SAN sends out wave of excitation
Atria contract
(delay) AVN sends out wave of excitation
Bundle of His/Purkinje fibre conducts wave of excitation to apex
Ventricles contract

25
Q

What controls changes to the heart rate?

A

Two centres in the medulla; the accelerator centre and inhibitory centre

26
Q

How is the accelerator centre connected to the SAN?

A

Sympathetic nervous system

27
Q

How is the inhibitory centre connected to the SAN?

A

Parasympathetic nervous system

28
Q

Where are blood pressure receptors found?

A

Cartoid arteries and aorta

29
Q

How do blood pressure receptors work?

A

When blood pressure is higher than usual, more impulses are sent to the inhibitory centre, which reduces heart rate. And vice versa

30
Q

what do chemoreceptors detect (nervous system)?

A

Changes in pH of blood due to CO2 concentration

31
Q

When more carbon dioxide is in the blood, what occurs?

A

pH decreases
chemoreceptors send more impulses to accelerator centre
heart rate increases
carbon dioxide removed
pH returns to normal

32
Q

Suggest one precaution that would ensure the response really was due to light. (1)

A

Use heat filter in front of lamp.

A-level Biology (21 decks)

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