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AQA Biology > 6.1 Internal & External Stimuli > Flashcards

6.1 Internal & External Stimuli Flashcards

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1
Q

What are plant growth factors?

A

Chemicals that regulate plant growth response to directional stimuli

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2
Q

Where are plant growth factors produced?

A

Planting growing regions

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3
Q

How do plant growth factors move around plant?

A

Diffuse from cell to cell
Mass transport in phloem

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4
Q

Why do shoots show positive phototropism?

A

IAA diffuses to shaded side of shoot tip
Causes active transport of H+ ions into cell wall
Disruption of H bonds between cellulose molecules make cell more permeable to water
Cells on shaded side elongate faster due to higher turgor pressure
Shoot bends towards light

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5
Q

Why do roots show positive gravitropism?

A

Gravity causes IAA to accumulate on lower side of root
IAA inhibits elongation of root cells
cells on upper side of root elongate faster
Root tip bends downwards

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6
Q

What’s the acronym for contrasting mammalian hormones and plant growth factors?

A

CASTS
Concentration
Action
Synthesis
Transport
Speed

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7
Q

Compare concentration of mammalian hormones and plant growth factors.

A

MH response not always dependent on concentration
PGF response proportional to concentration

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8
Q

Compare action of mammalian hormones and plant growth factors.

A

MH bind to complementary proteins in/on target cells
PGF can affect all cells

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9
Q

Compare synthesis of mammalian hormones and plant growth factors.

A

MH specialised glands
PGF various tissues in growing regions

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10
Q

Compare transport of mammalian hormones and plant growth factors.

A

MH circulatory system
PGF diffusion or phloem translocation

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11
Q

Compare speed of mammalian hormones and plant growth factors.

A

MH faster acting (homeostasis)
PGF slower acting (plant growth)

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12
Q

Define taxis.

A

Directional movement in response to external stimulus

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13
Q

Define kinesis.

A

Non directional response to presence and intensity of external stimulus

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14
Q

What is the importance of taxis and kinesis?

A

Maintain mobile organism in optimum environment

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15
Q

Why do many organisms respond to temperature and humidity with kinesis rather than taxis?

A

Less directional stimuli
Often no clear gradient from one extreme to other

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16
Q

How could a student recognise kinesis in an organisms movement?

A

Organism crosses division between two environments and turning increases to return to favourable
Organism moves distance into unfavourable and turning slowly decreases to lead to new environment

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17
Q

Outline events in a simple reflex arc.

A

Receptor detects stimulus
Sensory neuron
Relay neuron in CNS coordinated response
Motor neuron
Response by effector

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18
Q

What is the importance of a simple reflex?

A

Rapid response to potentially dangerous stimuli since only 3 neurons involved

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19
Q

What stats test could be used to determine whether factor has significant effect on organism movement in choice chamber or not?

A

Chi squared

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20
Q

What features do all sensory receptors have?

A

Establish a generator potential
Respond to specific stimuli

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21
Q

What is a Pacinian corpuscle?

A

A type of receptor found in the skin that responds to changes in pressure.

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22
Q

Describe the structure of a Pacinian corpuscle.

A

Single nerve fibre surrounded by layers of connective tissue separate by viscous gel and contained by a capsule

23
Q

What do Pacinian corpuscles have on the plasma membrane?

A

Stretch-mediated Na+ channels

24
Q

What do Pacinian corpuscles have along the base layer of tissue?

A

A capillary

25
Q

How does a Pacinian corpuscle respond to pressure?

A

Pressure deforms membrane, causing stretch-mediated Na+ ion channels to open
If Na+ influx raises membrane to threshold potential, a generator potential is produced
Action potential moves along sensory neuron

26
Q

Name the two types of photoreceptor cell located in the retina.

A

Cone cells
Rod cells

27
Q

Where are rod cells located in the retina?

A

Evenly distributed around periphery
Not in central fovea

28
Q

Where are cone cells located in the retina?

A

Mainly central fovea

29
Q

What’s the acronym for contrasting rod cells and cone cells?

A

PACL
Pigment
Visual Acuity
Colour sensitivity
Light sensitivity

30
Q

Compare pigment of rod cells and cone cells.

A

ROD: Rhodopsin
CONE: 3 types of iodopsin

31
Q

Compare visual acuity of rod cells and cone cells.

A

ROD: Low resolution as many rod cells synapse with 1 neuron
CONE: High resolution as 1 cone cell synapses with 1 neuron (no retinal convergence)

32
Q

Compare colour sensitivity of rod cells and cone cells.

A

ROD: Monochromatic (all wavelengths of light detected) so can’t detect different colours
CONE: Tricolour (red/blue/green wavelengths absorbed by different types of iodopsin) so can detect different colours

33
Q

Compare light sensitivity of rod cells and cone cells.

A

ROD: Very sensitive
CONE: Less sensitive

34
Q

What is retinal convergence?

A

The sharing of a single nerve fiber by several rod cells in the retina

35
Q

Outline the pathway of light from a photoreceptor to the brain.

A

Photoreceptor
Bipolar neuron
Ganglion cell of optic nerve
Brain

36
Q

Define myogenic.

A

Contraction of heart initiated within muscle rather than by nerve impulses

37
Q

Name the two nodes involved in heart contraction.

A

Sinoatrial node (SAN)
Atrioventricular node (AVN)

38
Q

Where is the Sinoatrial node (SAN) located?

A

Within the wall of the right atrium

39
Q

Where is the Atrioventricular node (AVN) located?

A

Near lower end of right atrium in the wall that separates the 2 atria

40
Q

Describe how heartbeats are initiated and coordinated.

A

SAN initiates wave of depolarisation
Wave spreads across both atria (atrial systole)
Layers of fibrous, non conducting tissue delays impulse while ventricles fill and valves close
AVN conveys wave of depolarisation via Bundle of His
Ventricles contract from apex upwards

41
Q

How can cardiac output by calculated?

A

stroke volume x heart rate

42
Q

What is the autonomic nervous system?

A

System that controls involuntary actions of glands and muscles

43
Q

What are the two subdivision of the autonomic nervous system?

A

Sympathetic
Parasympathetic

44
Q

What is the sympathetic nervous system?

A

Involved in “fight or flight” response
Stimulates effectors to speed up activity

45
Q

What is the parasympathetic nervous system?

A

Involved in normal resting conditions
Inhibits effectors to slow down activity

46
Q

Name the receptors involved in changing heart rate.

A

Baroreceptors
Chemoreceptors

47
Q

What is detected by the baroreceptors?

A

Changes in blood pressure

48
Q

Where are the baroreceptors located?

A

Carotid body

49
Q

What is detected by chemoreceptors?

A

Changes in pH

50
Q

Where are the chemoreceptors located?

A

Carotid body
Aortic body

51
Q

How does the body respond to an increase in blood pressure?

A

Baroreceptors send more impulses to cardioinhibitory centre in medulla
More impulses to SAN via parasympathetic nervous system
Stimulates release of acetylcholine which decreases heart rate

52
Q

How does the body respond to an decrease in blood pressure?

A

Baroreceptors send more impulses to cardioacceleratory centre in medulla
More impulses to SAN via sympathetic nervous system
Stimulates release of noradrenaline which increases heart rate and strength of contraction

53
Q

How does the body respond to an increase in CO₂ concentration?

A

Chemoreceptors detect pH decrease and send more impulses to cardioacceleratory centre in medulla
More impulses to SAN via sympathetic nervous system
Stimulates release of noradrenaline which increases heart rate
Blood flow to lungs increases so rate of gas exchange and ventilation increases

AQA Biology (43 decks)

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