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Biology - Unit 6 > Stimuli & Response > Flashcards

Stimuli & Response Flashcards

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1
Q

Why do plants respond to simuli

A

Increase chance of survival e.g towards light for more photosynthesis

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2
Q

Define tropism

A

Response of a plant to a directional stimulus

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3
Q

How do plants perform a tropism

A
  • Use growth factors such as auxins (Indoleacetic acid, gibberelins)
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4
Q

What does IAA do?

A

Cause cell elongation in the shoots and inhibit cell growth in the roots

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5
Q

What do gibberellins do?

A

Control flowering and germination

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6
Q

Where are growth factors made?

A

In growing regions of the plants

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7
Q

How do growth factors move?

A

Short distances by diffusion and active transport and long distance by phloem

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8
Q

Summarise phototropism

A
  • IAA moves to shadow side
  • Cell elongation in shoots
  • Inhibits cell growth in roots
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9
Q

Summarise gravitropism

A
  • IAA moves to underside
  • Cell elongation in shoots
  • Inhibits cell growth in roots
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10
Q

What is the purpose of taxes and kineses

A

Keep mobile organisms in a favourable environment

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11
Q

Define taxes

A

A Mobile organisms moves away from or towards a directional stimulus

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12
Q

Define kinesis

A

When mobile organisms change their movement and speed in response to a non-directional stimulus

Speed faster/turn more in unfavourable and slower in favourable

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13
Q

Define reflex

A

A rapid response to a stimulus without conscious control

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14
Q

Summarise a reflex

A

Stimulus detected by receptor, travels along sensory neurone, then relay neurone, then motor neurone, then effector then response where the relay neurone is in the CNS

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15
Q

Advantages of a reflex

A

Avoid damage or danger
No thinking so faster
No learning so protects infants

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16
Q

What is the pacinian corpuscle

A

A receptor in skin detecting pressure touch and vibration

17
Q

Summarise how a pacinian corpuscle causes a generator potential

A
  • Pressure causes lamellae to stretch and deform
  • Sodium ion channels are stretch mediated and hence open
  • Na+ diffuse into neurone
  • Greater stimulus, more deformation so more channels open
  • Depolarisation occurs (generator potential)
  • If threshold reached, AP occurs
18
Q

What does the fovea consist of

A

Lots of photoreceptors, mostly cones

19
Q

Summarise what happens when light hits a photoreceptor

A
  • Light focuses on retina by lens
  • Light absorbed by pigments in photoreceptor
  • Causes sodium ion channels to open (generator potential)
    If threshold is reached, AP occurs, travels across bipolar neurone and optic nerve to CNA
20
Q

Summarise ROD cells

A
  • Monochromatic
  • More sensitive to low light
  • Low visual acuity
  • Edges of the retina
21
Q

Why do ROD cells have low visual acuity?

A

Spacial summation to the bipolar neurone, so many rod cells to one bipolar neurone, so one AP generated, regardless of the number of ROD cells

22
Q

Summarise CONE cells

A
  • Trichromatic
  • Less sensitive to low light
  • High visual acuity
  • Focused on the fovea
23
Q

When do atrioventricular valves open?

A

When atria pressure is higher than ventricle pressure

24
Q

What is the purpose of valves?

A

Blood flows in one way and no back flow

25
Q

Summarise how a heart beats

A
  • SAN sends out electrical impulse as heart tissue is myogenic
  • Impulse sent to AVN which delays impulse, allowing atria to contract first
  • Does not pass through atria due to nonconducting tissue
  • AVN sends impulse down bundle of His down centre of heart
  • Then along purkyne fibres
    causing ventricles to contract from the base upwards
26
Q

Summarise the role of chemoreceptors/baroreceptors in decreasing heart rate

A
  • Detected high O2 levels due to less CO2 or detect high pressure
  • Impulse sent to medulla oblongata
  • Sends NERVE impulse via parasympathetic neurones
  • Causes less SAN electrical impulses
27
Q

Summarise the role of chemoreceptors/baroreceptors in increasing heart rate

A
  • Detect low blood O2 due to more CO2 so less pH or low pressure
  • Receptors send more impulses to the sympathetic centre of medulla oblongata
  • More impulses sent to SAN via symapthetic
  • SAN increase heart rate

Biology - Unit 6 (6 decks)

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