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A Level AQA Biology > Stimuli and Response > Flashcards

Stimuli and Response Flashcards

1
Q

What is tropism?

A

The response of a plant to a directional stimulus.

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2
Q

How do plants respond to stimuli?

A

Using growth factors/hormones.

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3
Q

What are some examples of plant growth factors/hormones?

A
  • Auxin.

- Gibberellins.

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4
Q

Where are plant growth factors made?

A

In growing regions of the plant (e.g. root tips and shoot tips).

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5
Q

How do plant growth factors move around the body?

A
  • Move short distances by diffusion and active transport.

- Move long distances in the phloem.

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6
Q

What is phototropism?

A
  • The effect of light on root tips and shoot tips (IAA moves to the shaded side of the roots/shoots).
  • Shoots - IAA causes elongation so shoots grow towards light.
  • Roots - IAA inhibits cell growth so roots grow away from light.
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7
Q

What is gravitropism/geotropism?

A
  • The effect of gravity on root and shoot tips (IAA always moves to the underside).
  • Shoots - Grow away from gravity.
  • Roots - Grow towards gravity.
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8
Q

What is taxes?

A

Mobile organism moves towards or away from a directional stimulus.

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9
Q

What is kinesis?

A

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

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10
Q

What are the stages of a reflex?

A

Stimulus - receptor - sensory neurone - relay neurone - motor neurone - effector - response.

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11
Q

What are the advantages of a reflex?

A
  • Help organism avoid damage.
  • Very fast.
  • Doesn’t need to be learnt so can protect infants.
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12
Q

What happens when a pacinian corpuscle is stimulated?

A
  • Pressure causes the lamellae to stretch and deform.
  • Stretch mediated sodium ion channels open.
  • NA+ diffuses into neurone.
  • Greater the stimulus, the more Na+ channels open.
  • Depolarisation of the neurone is called generator potential.
  • If threshold is reached, then an action potential is initiated.
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13
Q

What are the two types of receptor cell in the human eye?

A

Rod cells and cone cells.

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14
Q

What are some features of Rod cells?

A
  • Monochromatic - one pigment.
  • More sensitive to low light.
  • Low visual acuity.
  • Many rod cells join a single bipolar cell.
  • Mostly in peripheral part of the retina.
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15
Q

What are some features of cone cells?

A
  • Trichromatic (red, green and blue).
  • Colour vision.
  • Less sensitive to low light.
  • Higher visual acuity.
  • Each cone cell has its own bipolar cell.
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16
Q

What is the role of the sinoatrial node (SAN)?

A

Initiates heart beat.

17
Q

What is the role of the atrioventricular node (AVN)?

A

Delays electrical impulse so allows atria to contract before ventricles contract.

18
Q

When do the semilunar valves open?

A

When the blood pressure is greater in the ventricles then the blood vessels.

19
Q

When do the atrioventricular valves open?

A

When blood pressure is higher in the atria than ventricles.

20
Q

What is the role of the purkyne fibres?

A

Allows the electrical impulse to cause the ventricles to contract from the base upwards.

21
Q

Why does the heart contain non-conducting tissue?

A

It stops the electrical impulse from SAN reaching ventricles.

22
Q

What happens if we have high blood O2, low blood CO2, high pH or high blood pressure?

A
  • Chemoreceptors or baroreceptors detect it.
  • Receptors send nerve impulses to the medulla oblongata in the brain.
  • Medulla oblongata sends nerve impulses along parasympathetic neurones.
  • Parasympathetic neurones secrete acetylcholine (neurotransmitter).
  • Heart rate slows down.
23
Q

What happens if we have low blood O2, high blood CO2, low pH or low blood pressure?

A
  • Chemoreceptors or baroreceptors detect it.
  • Receptors send nerve impulses to the medulla oblongata.
  • Medulla oblongata sends more impulses along sympathetic neurones.
  • Sympathetic neurones secrete noradrenaline (neurotransmitter).
  • Heart rate speeds up.
24
Q

How is heart rate controlled?

A
  • SAN initiates the heart beat.
  • Sends an electrical impulse across the atria.
  • Atria contract
  • Non-conductive tissue prevents the electrical impulse reaching the ventricles.
  • AVN delays electrical impulse.
  • Allows the atria to contract and empty before the ventricles contract.
  • AVN sends the electrical impulse down the bundle of His and along the Purkyne tissue.
  • Ventricles contract from the base upwards.
25
Q

Why does the left ventricle have the most cardiac muscle?

A

It pumps blood to the whole body.

A Level AQA Biology (10 decks)

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