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Biology > Organisms Respond To Changes In Their Internal And External Environments (3.6) > Flashcards

Organisms Respond To Changes In Their Internal And External Environments (3.6) Flashcards

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1
Q

how can receptor cells respond to stimuli?

A
  • some produce electrical activity in nerve cells
  • some secrete substances
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2
Q

what are 2 examples of a coordinator?

A

brain
spinal chord

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3
Q

what are the 3 stages in the reflex arc?

A

detection
coordination
action

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4
Q

describe the reflex action process

A

stimulus -> receptor -> coordinators -> effectors -> response

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5
Q

how do organisms respond to change?

A

they detect a stimulus (by a receptor cell)

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6
Q

an organism must find ________ conditions to survive

A

favourable

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7
Q

what is taxis and kinesis?

A

simple responses that enable mobile organisms to stay in a favourable environment

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8
Q

what is kinesis?

A

a non-directional response to a stimuli
e.g when flatworms under a stone are exposed to light they move in random directions which eventually bring them back into the darkness, they will then stop moving

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9
Q

the rate of movement of an organism is affected by the ________ of the stimulus

A

intensity

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10
Q

what is taxis?

A

a directional response to a stimulus (the organism moves directly away or towards the stimulus)
e.g euglena swims directly towards the light in a pond using its flagellum

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11
Q

what is phototropism?

A

a growth response to light

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12
Q

what is a tropism?

A

a growth response towards a stimulus (in plants)

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13
Q

what is geotropism?

A

growth response to gravity

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14
Q

a tropism can be __________ or __________ causing the plant to grow towards or away from the stimulus

A

positive
negative

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15
Q

plant growth regulators act in a similar way to _________________ in animals

A

hormones

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16
Q

the growth response in plants relies on plant growth ____________ that are released in response to a _________.

A

regulators
stimulus

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17
Q

what are 2 examples of plant growth regulators?

A

auxin
IAA’s

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18
Q

what does IAA stand for?

A

indoleactic acid

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19
Q

where is IAA found in the plant

A

just before the tip

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20
Q

how does IAA influence the growth of a plant towards a stimulus?

A
  • when IAA moves into the elongating region of the shoot it lowers the PH
  • this breaks some of the bonds in the cellulose cell wall
  • the cell wall loosens and the cells can be more easily stretched (cell elongation)
    -by effecting the cell elongation, IAA influences the growth of a plant towards the stimulus
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21
Q

what is it called when shoots grow towards the light?

A

positive phototropism

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22
Q

describe the process of phototropism?

A

-in shoots, higher concentrations of IAA results in a greater rate of cell elongation
-IAA moves from the illuminated side of a shoot to the shaded side
- the higher concentration of IAA on the shaded side causes a faster rate of cell elongation
- this causes the shoot to bend towards the light

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23
Q

What are some elements of hormonal communication?

A

Chemical
Transmition by blood
Slow
Long lasting response
Permanent effect

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24
Q

What are some elements of nervous transmission?

A

Neurone transmission
Rapid transmission
Localised
Temporary effect
Nerve impulse specifically targeted

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25
Q

What are the 2 elements of the peripheral nervous system?

A

Autonomic - unconscious
Voluntary - conscious control

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26
Q

What type of cell is the Pacinian Corpuscle?

A

Receptor cell

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27
Q

The Pacinian Corpuscle responds to changes in _____________ __________.

A

Mechanical pressure

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28
Q

How is a nerve impulse generated in the Pacinian Corpuscle?

A

When pressed, the change in pressure on the membrane passes to the core and causes increased permeability to sodium ions causing depolarisation leading to a generator potential. If this exceeds the threshold then a nerve impulse is generated.

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29
Q

The Pacinian Corpuscle is a t___________.

A

Transducer

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30
Q

What is a transducer?

A

Converts one form of energy to anothr

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31
Q

How does the Pacinian Corpuscle act as a transducer?

A

It converts the energy of the stimulus into a nervous impulse known as a generator potential.

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32
Q

What happens to the stretch mediated sodium channel protein when they are deformed?

A

Their permeability to sodium changes and allow sodium ions to pass along them.

This stretching widens the sodium channels and sodium ions diffuse into the neurone.

The influx of sodium ions changes the potential of the membrane (depolarised), making a generator potential.

The generator potential therefore starts an action potential-nerve impulse

33
Q

What is the lining of the eyeball called?

A

The retina

34
Q

What do light receptors do?

A

Send nerve impulses along sensory neurones in the optic nerve to the brain

35
Q

What are the 2 types of photoreceptors?

A

Rods and cones

36
Q

Light use pass through other structures e.g ________ ____ to reach the rods and cones.

A

Bipolar cells

37
Q

What photosensitive chemical do rods contain?

A

Rhodopsin

38
Q

What photosensitive pigment do cones contain?

A

Iodopsin

39
Q

What happens to photosensitive chemicals in light?

A

The pigments are bleached by the light.
After bleaching rhodopsin regenerates slowly and iodopsin regenerates quickly

40
Q

How many rods are there in the eye?

A

120 million

41
Q

How many rods connect to one bipolar cell?

A

15 to 45

42
Q

Where are rods found?

A

In all the retina but not in the fovea

43
Q

Rods have ______ sensitivity

A

Good

44
Q

How many cones are there in the eye?

A

6 million

45
Q

How many cones connect to 1 bipolar cell?

A

1

46
Q

Where are cones found?

A

In all the retina, there are lots in the fovea

47
Q

Cones have _____ sensitivity

A

Poor

48
Q

What are the 3 types of cones?

A

Red
Green
Blue

Each type of cone has a broad sensitivity to different wavelengths so the responses overlap to distinguish other colours e.g yellow

49
Q

Iodopsin regenerates ______.

A

Quickly

50
Q

Rhodopsin regenerates ______.

A

Slowly

51
Q

What are the two divisions of the autonomic nervous system?

A

Sympathetic nervous system
Parasympathetic nervous system

52
Q

The sympathetic nervous system _______ up activities and thus allows us to cope with stressful situations e.g the fight or flight response

A

Speeds

53
Q

The parasympathetic nervous system inhibits effects and ______ _____ activities. This allows energy to be conserved. Controls under normal resting conditions.

A

Slows down

54
Q

The sympathetic and parasympathetic nervous system are ____________, meaning their effects oppose one another.

A

Antagonistic

55
Q

Where are chemoreceptors found?

A

In the wall of the coronary arteries

56
Q

What do chemoreceptors detect change in?

A

PH

57
Q

When CO2 concentrations in the blood is too _______, chemoreceptors detect the drop in __ and send impulses to the section of the medulla oblong at a responsible for increased heart rate.

A

High
PH

58
Q

Where do chemoreceptors send impulses to in the brain?

A

The medulla oblongata

59
Q

What is the medulla oblongata?

A

The cardiac centre of the brain

60
Q

The medulla oblongata is linked to the ___ node that decreases ______ rate via the parasympathetic nervous system.

A

SA
Heart

61
Q

How does the medulla oblongata increase heart rate?

A

Increases the number of impulses sent to the SA node via the sympathetic nervous system.

62
Q

What is a baroreceptor?

A

A pressure receptor

63
Q

Where are baroreceptors found?

A

In the wall of the coronary artery and the atria

64
Q

What happens when blood pressure is too high?

A

Impulses are sent to the medulla oblongata which sends impulses to the S.A node via the parasympathetic nervous system which decreases the heart rate.

65
Q

What happens when blood pressure is too low?

A

Impulses are sent to the medulla oblongata which then sends impulses to the S.A node via the sympathetic nervous system which increases the heart rate

66
Q

What is an ECG?

A

Electrocardiogram

67
Q

What does the parasympathetic nervous system do?

A

Inhibits effectors
Controls actions under resisting conditions
Slows down activity
Conserves energy

68
Q

What does the sympathetic nervous system do?

A
  • stimulates effectors
  • controls conditions under stress or activity
  • initiates the fight or flight response
69
Q

What is a nerve impulse?

A

A self propagating wave of electrical disturbance that travels along the surface of the axon membrane.

70
Q

What is the resting potential of an axon?

A

-65mv

71
Q

When is an axon said to be polarised?

A

When it is at its resting potential

72
Q

The active transport of sodium ions is greater than that of potassium ions. How many sodium ions move out for the potassium ions that move in?

A

3 sodium ions move out for every 2 potassium ions that move in.

73
Q

How is a chemical gradient created in the axon?

A

There are more sodium ions in the tissue fluid surrounding the axon than in the cytoplasm, and more potassium ions in the cytoplasm than in the tissue fluid, this creating a chemical gradient.

74
Q

Why is there an electrical gradient in the axon?

A

As more potassium ions diffuse out of the axon, the outside of the axon becomes more and more positive.

75
Q

What is an action potential?

A

The temporary reversal of the charge on the axon membrane. As a result the negative charge of -65mv inside the membrane becomes a positive charge of around +40mv

76
Q

What happens to the axon membrane during an action potential?

A

It is depolarised

77
Q

Briefly describe an action potential.

A
  1. Na gated channels open
  2. Na food into axon
  3. Potential difference reversed
  4. Na gates close
  5. K gated channels open
  6. K flood out of axon
  7. Inside axon returns to negative
  8. Resting potential is restored
78
Q

What is hyperpolarisation?

A

The temporary overshoot of outward diffusion of potassium ions leads to the inside of the axon being more negative (relative to the outside) than usual.

Biology (8 decks)

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