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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

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33
Q

What is the lining of the eyeball called?

A

The retina

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34
Q

What do light receptors do?

A

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

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35
Q

What are the 2 types of photoreceptors?

A

Rods and cones

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36
Q

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

A

Bipolar cells

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37
Q

What photosensitive chemical do rods contain?

A

Rhodopsin

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38
Q

What photosensitive pigment do cones contain?

A

Iodopsin

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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

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40
Q

How many rods are there in the eye?

A

120 million

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41
Q

How many rods connect to one bipolar cell?

A

15 to 45

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42
Q

Where are rods found?

A

In all the retina but not in the fovea

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43
Q

Rods have ______ sensitivity

A

Good

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44
Q

How many cones are there in the eye?

A

6 million

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45
Q

How many cones connect to 1 bipolar cell?

A

1

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46
Q

Where are cones found?

A

In all the retina, there are lots in the fovea

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47
Q

Cones have _____ sensitivity

A

Poor

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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

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49
Q

Iodopsin regenerates ______.

A

Quickly

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50
Q

Rhodopsin regenerates ______.

A

Slowly

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51
Q

What are the two divisions of the autonomic nervous system?

A

Sympathetic nervous system
Parasympathetic nervous system

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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.

79
Q

What are the 3 factors that affect the speed of an action potential?

A
  • myelination and saltatory conduction
  • axon diameter
  • temperature
80
Q

How does myelination effect the speed of an action potential?

A

The action potential jumps from node to node (saltatory conduction) which means the action potential travels along the axon faster as it doesn’t have to generate an action potential along the entire length, just the nodes of Ranvier

81
Q

How does axon diameter effect the speed of an action potential?

A

The wider the diameter, the speed of conductance increases

A wider diameter means that there is less leachate of ions out and therefore action potentials travel faster

82
Q

How does temperature affect the speed of an action potential?

A

A higher temperature increases the speeds of conductance because:
- the ions diffuse faster
- the enzymes involved in respiration work faster therefore there is more ATP for active transport in the sodium potassium pump

83
Q

Describe how a synapse functions.

A

1) an action potential arrives at the synaptic knob. Depolarisation of the synaptic knob leads to opening of Ca+ channels and Ca+ diffuses into the synaptic knob.
2) vesicles contain neurotransmitters move and fuse with the presynaptic membrane. Neurotransmitter is released into the synaptic cleft.
3) Neurotransmitter diffuses, down concentration gradient, across synaptic cleft, to post-synaptic membrane; neurotransmitter binds by complementary shape to receptors on the surface of the post-synaptic membrane.
4) Na+ ion channels on the post-synaptic membrane open and Na+ diffuses in; if enough neurotransmitter, then enough Na+ diffuses in, above threshold, and post-synaptic neurone becomes depolarised.
5) neurotransmitter is degraded and released from the receptor; the Na+ channel close and the post-synaptic neurone can re-establish resting potential; the neurotransmitter is transported back into the presynaptic neurone where is it recycled.

84
Q

1) an action potential arrives at the synaptic _____. Depolarisation of the synaptic knob leads to opening of Ca+ channels and Ca+ diffuses into the synaptic knob.
2) vesicles contain neurotransmitters move and fuse with the presynaptic membrane. Neurotransmitter is released into the synaptic _____.
3) Neurotransmitter diffuses, down ____________ gradient, across synaptic cleft, to post-synaptic membrane; neurotransmitter binds by complementary shape to receptors on the surface of the post-synaptic membrane.
4) Na+ ion channels on the post-synaptic membrane open and Na+ diffuses in; if enough neurotransmitter, then enough Na+ diffuses in, above ________, and post-synaptic neurone becomes depolarised.
5) neurotransmitter is degraded and released from the receptor; the Na+ channel close and the post-synaptic neurone can re-establish _______ potential; the neurotransmitter is transported back into the presynaptic neurone where is it recycled.

A

1) knob
2) cleft
3) concentration
4) threshold
5) resting

85
Q

What is unidirectionality?

A
  • synapses can only travel in one direction from the presynaptic neurone to the postsynaptic neurone
86
Q

What are the 2 types of summation?

A

Spatial summation

Temporal summation

87
Q

What is spatial summation?

A
  • a number of different presynaptic neurones together release enough neurotransmitter to exceeded the threshold value of the post synaptic neurone. Together they therefore trigger a new action potential
88
Q

What is temporal summation?

A
  • a single presynaptic neurone releases neurotransmitters many times over a short period. If the total amount exceeds the threshold value of the postsynaptic neurone, then a new action potential is triggers.
89
Q

What is inhibition in a synapse?

A
  • on the postsynaptic membrane of some synapses, the protein chapels carrying chlorine ions (Cl-) can be made to open.
  • this leads to an inward diffusion of Cl- ions, making the inside of the postsynaptic membrane even more negative than when it is at resting potential (hyperpolarisation)
  • this makes it less likely that a new action potential will be created (inhibitory synapses)
90
Q

What are the different modes of action drugs can have on a synapse?

A
  • stimulating the release of a neurotransmitter
  • providing the chemicals needed to synthesise neurotransmitters
  • acting in the same way as a neurotransmitter by binding to the same specific receptor
  • preventing the reuptake of the neurotransmitter by the presynaptic neurone
91
Q

Neurotransmitters are inhibitory or __________.

A

Excitatory

92
Q

Excitatory neurotransmitters result in the production of an a_____ p________.

A

Action potential

93
Q

Inhibitory neurotransmitters prevent the production of an a______ p_______. They do this by causing __________ ions to leave the postsynaptic membrane.

A

Action potential
Potassium

94
Q

Striated muscles make up the muscles in the body that are attached to the ________.

A

Skeleton

95
Q

What is a striated muscle made up of?

A

Muscle fibres

96
Q

What is a striated muscle made up of?

A

Muscle fibres

97
Q

What is the cell surface membrane called in a striated muscle cell?

A

Sarcolemma

98
Q

What is the cytoplasm called in a striated muscle cell?

A

Sarcoplasm

99
Q

what is the Endoplasmic reticulum called in a striated muscle cell?

A

Sarcoplasmic reticulum (SR)

100
Q

What does the sarcoplasm contain?

A

Mitochondria and Myofibrils

101
Q

What are Myofibrils?

A

Bundles of actin and myosin filaments - slide past each other during muscle contraction

102
Q

How are calcium ions transported into lumen of the sarcoplasmic reticulum?

A

The membrane of the SR contain protein pumps that transport calcium ions into the lumen of the SR

103
Q

Where are Myofibrils located?

A

In the sarcoplasm

104
Q

What are the 2 types of protein filament that a Myofibrils is made up of?

A

Myosin
Actin

105
Q

Each Myofibril is made up of _____ filaments of myosin and ____ filaments of actin.

A

Thick filaments of myosin

Thin filaments of actin

106
Q

What are the 6 elements of a myofibril?

A

H band
I band
A band
M line
Z line
Sarcomere

107
Q

What is the H band?

A

Part of a Myofibril where only thick myosin filaments are present

108
Q

What is the I band?

A

Part of a Myofibril where only thin actin filaments are present

109
Q

What is the A band?

A

Part of a Myofibril that contains areas where only myosin filaments are present and areas where myosin and actin filaments overlap

110
Q

What is the M line?

A

Part of a Myofibril where there is attachment for myosin filaments

111
Q

What is the Z line?

A

Part of a Myofibril where there is attachment for actin filaments

112
Q

What is the sarcomere?

A

The section in a Myofibril between two Z lines

113
Q

What are the 2 types of muscle fibres?

A

Slow-twitch
Fast-twitch

114
Q

What are some elements of fast muscle fibres?

A
  • short contraction-relaxation cycle
  • fewer capillaries
  • ATP supplied mostly from anaerobic respiration
  • fewer, smaller, mitochondria present
  • large store of calcium ions in the SR
  • large amounts of glycogen and phosphocreatine present
  • faster rate of ATP hydrolysis in myosin heads
  • fatigues rapidly due to grater lactate formation
115
Q

What are some elements of slow muscle fibres?

A
  • long contraction -relaxation cycle
  • denser network of capillaries
  • ATP supplies mostly from aerobic respiration
  • many, lager, mitochondria present
  • small store of calcium ions in the SR
  • small amounts of glycogen present
  • slower rate of ATP hydrolysis in myosin heads
  • fatigues more slowly due to rescued lactate formation
116
Q

What proportions of fast muscle fibres do high intensity athletes have?

A

Higher proportions

  • low proportion of slow muscle fibres
117
Q

What proportions of slow muscle fibres do endurance athletes have?

A

High

  • low proportion of fast muscle fibres
118
Q

What effects can training have on an individual’s muscles?

A
  • influence which fibre types develop
  • increase the number of capillaries and mitochondria present in muscles
119
Q

What 3 molecules make up an actin fibre?

A

Actin, tropomyosin, troponin

120
Q

What is the named neurotransmitter?

A

Acetylcholine

121
Q

Which enzyme breaks down acetylcholine?

A

Acetylcholinesterase

122
Q

Muscles are ________.

A

Antagonistic

123
Q

Skeletal muscle is under conscious (V________) control.

A

Voluntary

124
Q

Describe the structure of a myosin filament.

A

Composed of polypeptide chains twisted around each other with two globular heads on the end.

125
Q

Describe how a wave of depolarisation spreads across the sarcolemma in a neuromuscular junction.

A

An action potential causes the release of acetylcholine into sarcolemma

126
Q

What causes the release of calcium ions from the SR in a neuromuscular junction?

A

The wave of depolarisation spreads over the sarcolemma into T tubules- this causes the release of calcium ions from the SR

127
Q

What to calcium ions attach to on the actin filament snd what does this do? (Neuromuscular junction)

A

The calcium ions attach to the troponin complexes and cause them to detach from tropomyosin. This exposes myosin binding sites

128
Q

What provides the energy for a contraction (Neuromuscular junction)?

A

As the myosin attaches to the acid a molecule of ATP is broken down into ADP and Pi. This release of energy provides the energy for the contraction

129
Q

Describe a power stroke.

A

Myosin, locked onto actin, now contracts - pulling the actin filaments. The 2 filaments slide past each other - this s why it’s called the sliding filament model of muscle contraction

Biology (8 decks)

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