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Biology AQA A Level > Response to changes in environment Ch.14 > Flashcards

Response to changes in environment Ch.14 Flashcards

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1
Q

Stimulus

A

a change in an organisms internal or external environment, leading to a response.

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2
Q

What is the importance of response?

A

To increase the chances of survival.

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3
Q

What is kinesis?

A

movement in response to a stimulus. The movement is random with the aim of reaching a favourable environment,

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4
Q

What is taxis?

A

a movement in a response to stimulus. The movement is directional (moving away or towards stimulus), with the aim of reaching a favourable environment

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5
Q

Name all the plant phototropisms

A

Positive phototropism, positive hydrotropism,positive gravitrophism, negative gravitrophism

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6
Q

What is positive phototropism?

A

The shoots, stems and leaves grow towards the light.

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7
Q

What is positive hydrotropism?

A

Roots grow to water

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8
Q

Positive gravitropism

A

Roots grow in the direction of gravity (down)

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9
Q

Negative gravitropism

A

Shoots grow away from gravity (up)

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10
Q

How does gravitropism work?

A

Starch grains (Amyloplast) settle due to gravity. IAA accumulates and in roots it inhibits cell elongation. In shoots it stimulates cell elongation.

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11
Q

How does phototropism work?

A

Light is detected by a chemical in the short tip. Light stimulates IAA to move and accumulates in the shaded side. It stimulates cell elongation on shaded side (throughout the plant). The shaded side grows faster and plant grows towards the light.

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12
Q

What is the chain from stimulus to response

A

Stimulus to Receptor to Co-coordinator to effector to response

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13
Q

What is a Receptor?

A

A specialised cell that detects a specific stimulus and transmits a signal to a sensory neuron.

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14
Q

What is a coordinator?

A

Consists of the brain and the spinal cord. It receives information from receptor and determines response.

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15
Q

What is an effector?

A

The effector carries out the response (a muscle or gland).

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16
Q

What is a reaction?

A

The action that occurs

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17
Q

Why do we need reflexes?

A

1) Reduced potential of harm and damage to organism/tissue.

2)

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18
Q

Why do we need reflexes?

A

1) Reduced potential of harm and damage to organism/tissue.
2) Faster response then if the brain was involved
3) Essential for functions such as breathing and your heart beating
4) Homeostatis mechanisms can be controlled

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19
Q

What is the name for the receptor that responds to pressure ?

A

The Pacinian corpuscles

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20
Q

What is the structure of the Pacinian corpuscles?

A

A single nerve fibre which has Na+ channel protein in the membrane. Myelin sheath. A capsule .

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21
Q

How does the Pacinian corpuscles work?

A

Pressure on the skin changes the shape of the Pacinian corpuscles. This causes the Na channels to open and Na ions diffuse through the channel making the inside more positive. This causes a generator potential. When a threshold is reached an action potential occurs.

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22
Q

How is the structure of Pacinian corpuscles related to the function?

A

The neuron ending has a stretch mediated sodium channel.

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23
Q

What is a Rod?

A

A receptor in the retina that allows us to see light.

24
Q

What is a Cone?

A

A receptor in the retina that allows us to see colour.

25
Q

What is the structure of the Rods and Cones?

A

Cell membrane, vesicles containing pigment, cell body and connection to sensory neuron.

26
Q

What is the pigment in the Rods?

A

Rhodosin

27
Q

How do Rods work?

A

Rhodosin is broken down to Retinene and Scotopsin in the presence of light. In the dark Retinene and Scotopsin forms Rhodosin. When Retinene and Scotopsin are present Na+ channel in the cell membrane open and ions enter by facilitated diffusion. A generator potential is established and an impulse is sent via the sensory neuron.

28
Q

How do Cones work?

A

Contains a pigment which breaks down when it asbsorbs light so Na+ channel proteins in the membrane opens….

29
Q

Why can cones have one of three different forms of iodopsin.

A

Each type has a maximum absorbance of either green, blue or red.

30
Q

Why can we see other colours except for red, blue and red?

A

A mixture of cones are stimulated at the same time sending a mixture of electrical signals to the brain.

31
Q

Why can some people not see some colours?

A

Lack of a specific cone or lack of iodopsin within the cone.

32
Q

What is visual acuity?

A

How detailed an image is.

33
Q

What is light sensitivity?

A

How much light is required for an image to be produced.

34
Q

What visual acuity do rods and cones have?

A

Rods have low visual acuity, Cones haven high.

35
Q

What type of lights sensitivity do rods and cones have?

A

Rods have high and cones have low.

36
Q

Why do Rods have a low acuity?

A

They share bipolar neurones

37
Q

Why do Cones have high acuity?

A

They each have their own bipolar neurone

38
Q

Why do Rods have high light sensitivity?

A

Bipolar neurone is shared with more than one rod. Stimulus accumulates from more than one rod so it reaches the threshold of the bipolar neurone with less stimulus.

39
Q

Why do Cones have low light sensitivity?

A

One cone to one bipolar neurone so a certain amount of stimulus needs to be detected in order to hit threshold.

40
Q

Where are cones found?

A

Concentrated in fovea and decreases concentration as it goes away from the fovea.

41
Q

Where are rods found?

A

Concentrated in the peripheral (side of the eyes) and decreases as it goes to the middle.

42
Q

Where is there no cones or rods?

A

In the blind spot

43
Q

What is the blind spot?

A

Where the bundle of nerves from the eyes go to the brain. There are no cones or rods here

44
Q

What pigment is in Rods?

A

Rhodsin

45
Q

What does Rhodsin break down into in the light?

A

Retinene and Scotopsin

46
Q

What pigment is in Cones

A

Iodopsin

47
Q

What three colours do Cones produce

A

Red, Blue, green

48
Q

What is the nervous system that slows down the heart rate?

A

Sympathetic Nervous system

49
Q

What is the nervous system that speeds up the heart rate?

A

Parasympathetic nervous system

50
Q

How does the heart contract

A

1) SAN sends nerve imputlse to AVN
2) Pause for ventricle to get filled with blood
3) AVN sends nerve impulse to Bundle of His
4) Impulse reaches Purkyne Tissue

51
Q

What is the receptor that detects change in pH? and where is it found?

A

Chemoreceptors in the carotid artries or aorta

52
Q

What is the receptor that detects change in pressure? and where is it found?

A

Borecpetors in the carotid artries and aorta

53
Q

What happens when there needs to be an increase in heart rate?

A

Chemo/ Bore receptors increase frequency of nerve impulses to the medulla oblongata (brain) and the brain increases impulses to the SAN via the sympathetic nervous system.

54
Q

What happens when there needs to be an decrease in heart rate?

A

Chemo/ Bore receptors increase frequency of nerve impulses to the medulla oblongata (brain) and the brain increases impulses to the SAN via the parasympathetic nervous system.

55
Q

Why does CO2 decrease the pH?

A

CO2 reacts with water to produce carbonic acid (H2CO3) which dissociates to release H+ ions. Decreasing the pH.

Biology AQA A Level (15 decks)

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