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A Level Biology Paper 2 > Survival, Response, Nervous System > Flashcards

Survival, Response, Nervous System Flashcards

1
Q

External stimuli

A

Temperature
pH
Pressure
Humidity

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2
Q

Internal stimuli

A

Change in pH
Blood glucose concentration
Blood water potential

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3
Q

Why do woodlice spend more time in humid areas

A

Likelihood of dessicated is less
Due to their relatively large SA:VOL
And open gas exchange surface
And no waxy waterproof cuticle on exoskeleton

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4
Q

What are gibberellins

A

Growth factors
Stimulate flowering and seed germination
Growth of stem and flowering of plant

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5
Q

Threshold

A

Minimum intensity required to result in an action potential

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6
Q

Why aren’t neurones myelinated

A

They are so short and small that they only carry an impulse over short distances

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7
Q

What are neutotransmitters

A

Chemical transmitters that diffuse across synaptic clefts from the pre synaptic neurones membrane where they are synthesised to the post synaptic neurones membrane
Binding to the complementary receptor on the post synaptic membrane

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8
Q

Where is acetylcholine used

A

Parasympathetic branch of autonomic nervous system
Cholinergic synapse
Neuromuscular synapse

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9
Q

What is the maximum frequency of action potentials limited by

A

Refractory period length

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10
Q

Frequency of action potentials is related to what

A

Intensity of stimulus

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11
Q

Stimulus reaction pathway

A 
Stimulus
Receptor
Sensory neurone
Coordinator
Inter neurone/relay
Coordinator
Motor neurone
Effector
Response
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12
Q

Stimulus

A

Detectable change in the internal or external environment of an organism
That produces a response
To keep optimum conditions for survival

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13
Q

Instinctive behaviour

A

Inate responses to stimuli

Genetically determined so not learned

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14
Q

Examples of instinctive behaviour

A

Kinesis
Taxis
Reflex arc

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15
Q

What is a reflex

A

An innate response to stimuli

Producing a specific short lived response

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16
Q

What is kinesis

A

Random locomotion of whole organism in response to a stimulus
Inate
AKA rate of change of movement

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17
Q

Kinesis in woodlice

A

Move around more (speed and rate of turning) in low humidity
Rate of movement related to intensity of stimulus
Random movements (not directional)
Don’t move along a gradient of humidity
Just more likely to reach Hugh humidity by chance
Adaptive response

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18
Q

How do you investigate kinesis

A

Choice chamber

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19
Q

What is taxis

A

Directional locomotion of whole organism
Either towards
Or away
From a stimulus

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20
Q

Two types of taxis

A 
Positive taxis (towards stimulus)
Negative taxis (away from stimulus)
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21
Q

Examples of taxis

A

Phototaxis (light)
Aerotaxis (air)
Chemotaxis (chemical)

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22
Q

Explain taxis in earthworms

A 
Negative phototaxis
Away from light
Increases chance of survival in soil 
More likely to find food
More likely to avoid predators
Less likely to dehydrate
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23
Q

Similarities between taxis and kinesis

A

Both involve locomotion of whole organism in response to a stimulus
Both inate

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24
Q

Taxis vs kinesis

A

Taxis is directional movement whereas kinesis is random

Taxis is a response towards or away from a stimulus whereas kinesis is a change in rate of movement

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25
Q

What is a tropism

A

Growth movement
Of part of a plant
In response to a directional stimulus
Towards or away

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26
Q

Two types of tropism

A

Positive (towards)

Negative (away)

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27
Q

Examples of tropisms

A

Phototropism (light)
Geotropism (gravity)
Halotropism (salt)
Hydrotropism (water)

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28
Q

What are growth factots

A

Synthesised in cells throughout plants
Diffuse through tissue
In response to a stimulus
Stimulating or inhibiting growth in the tissue that produced it

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29
Q

Growth factor vs hormone

A

Growth factors affect the tissue that released them

Hormones affect a distant target organ

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30
Q

Growth factor vs nervous system

A

Growth factors effect is a lot slower than an electrical impulse
Electrical impulse can travel all over whereas growth factor is localised

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31
Q

What are auxins

A

Growth factors that cause shoot growth by cell elongation
Cell wall becomes loose and cells get longer
Moves through plant tissue and brings about tropisms
Due to uneven distribution of auxin in growing region
Causing uneven growth

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32
Q

IAA

A

Indoleacetic Acid
Plant growth factor
Synthesised in shoots and roots
Diffusing into growing regions

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33
Q

IAA in shoots

A

Synthesised in the shoot tips
Diffuses into growing region
Light causes movement of IAA from light to shaded side
Proportionally more IAA on shaded side
Causing directional growth
Promoting elongation on shaded side
Uneven growth as shoot bends towards light

Positive phototropism

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34
Q

IAA in roots

A 
IAA synthesised in roots
IAA diffuses into growing region
IAA moves towards underside/shaded side
Inhibits elongation
Proportionally IAA on underside
Directional uneven growth down into the soil
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35
Q

How does the nervous system work

A

Detection of stimuli by receptors
Transmission of nerve impulses by neurones
Response by effectors

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36
Q

What is the nervous system

A

Nervous system provides a rapid response to stimuli

Involving nerve transmission along neurones and chemical transmission across synapses between neurones

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37
Q

Endocrine vs nervous system

A

Endocrine system involves hormones for communication whereas nervous system has neurotransmitters
Endocrine system has a slower, longer lasting response than the nervous system

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38
Q

What does the nervous system consist of

A

Central nervous system (brain and spinal cord)

Peripheral nervous system (nerves originating from brain and spinal cord)
Autonomic (involuntary/subconscious)
Voluntary (voluntary conscious control)

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39
Q

What are neurones

A

Specialised cells adapted to their function

Which is to carry electrical impulses from one part of the body to another

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40
Q

Types of neurones

A

Sensory neurone (receptor to CNS)
Inter (relay or bipolar neurone)
Motor (CNS to effector)

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41
Q

Features of a motor neurone

A 
Dendrites
Nucleus
Cell body
Schwann cells
Myelin sheath
Nodes of Ranvier
Terminal end branch
Axon
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42
Q

Dendrites

A

Many thin extensions projecting out from the cell body
Carry electrical impulses towards cell body
Recieve impulses from other nerve cells

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43
Q

Cell body function

A 
Soma
Contains organelles like RER, 80s ribosomes 
For protein synthesis
To synthesise neurotransmitters
Contains nucleus
44
Q

Schwann cells

A 
Synthesise myelin (lipid)
Which insulates the axon
45
Q

Myelin

A 
Lipid 
Synthesised by schwann cells
Insulating electrical impulses along axon to allow for saltatory conduction
Increasing the speed of transmission
Provides protection
46
Q

Nodes of Ranvier

A

Gaps between schwann cells
Where myelin sheath is absent
And saltatory conduction can occur

47
Q

Axon

A

Carries nerve impulses away from cell body

48
Q

Terminal end branches

A

Connect neurone to effector

49
Q

What is resting potential

A

At rest there is a potential difference
Of -70mV across axon membrane
Due to the outside of the membrane being slightly more positive
Higher concentration of positive Na+ ions outside neurone
Higher concentration of K+ inside neurone so diffuse out through leaky potassium ion Channel proteins
Remains polarised until stimulus of threshold potential

50
Q

How is a resting potential established

A

Sodium potassium pump actively transports 3 Na+ out of axon and 2 K+ into axon
Using energy from ATP hydrolysis
K+ diffuses out if axon by potassium channel protein down a concentration gradient
Making the inside more negative than outside of the membrane

51
Q

Synoptic links

A

Na+/K+ pump for active transport
Many mitochondria in neurones to synthesise ATP
Channel proteins involved in facilitated diffusion of ions
Proteins are specific shapes and structures

52
Q

All or nothing principle

A

If a stimuluses intensity is below threshold there is no action potential
Anything at threshold or above generates a full sized action potential
Regardless of increase in stimulus (only affects frequency)

53
Q

Depolarisation

A

Stimulus (-50mV) opens voltage gated Na+ channel proteins
Na+ ions diffuse into cell down concentration gradient
Via facilitated diffusion
Higher concentration of positive Na+ ions inside the cell makes the inside relatively more positive than outside

54
Q

Repolarisation

A 
\+40mV action potential reached
Causing Na+ channel proteins to close
K+ channel proteins to open
K+ rapidly diffuses out
Down a concentration gradient
Making the inside more negative again
55
Q

Hyperpolerisation

A

Potassium channels remain open longer than needed
To reach resting potential
Making the inside even more negative
Sodium potassium pump restores the resting potential of -70mV once -80/-90mV reached

56
Q

Action potential

A

Period of inexcitability

Following the transmission of an impulse

57
Q

What is the refractory period determined by

A

The short time taken to return the membrane to resting potential

58
Q

Advantage of refractory period

A

Prevents overstumulation
Which would waste valuable ATP
Lead to neurone death

59
Q

What is a nerve impulse

A

Movement/propagation of an action potential along a neurone
Action potential acts as stimulus to adjacent polarised areas of membrane
Causing action potential to be passed along

60
Q

What affects the rate of nerve transmission

A

Temperature
Axon diameter
Myelin sheath and saltatory conduction

61
Q

Explain myelination and saltatory conduction

A

Impulse travels by jumping from one node of ranvier to the next
Occurs because myelin sheath insulates the axon so depolarisation can only occur at the nodes where there are gaps/myelination absent/axon membrane is exposed
Pumps and channel proteins only found at the nodes
Electrocurrents produced depolarises next node
And impulse jumps from 1 to next
Increasing the rate of transmission
Because depolarisation can only occur at the nodes so less of the neurone needs to be depolarised
Sodium diffuses between nodes

62
Q

How does temperature affect nerve transmission

A

Higher temperature means greater kinetic energy
Increasing the rate of diffusion of ions
Which increases the rate of conduction of ions

63
Q

How does axon diameter affect rate of nerves transmission

A

Larger diameter means larger membrane surface area
Increasing number of channel proteins
Increases the rate of diffusion and hence conduction

64
Q

Why are impulses described as unidirectional

A

Only go one way

From pre-synaptic neurone membrane to post-synaptic neurone membrane

65
Q

How do you identify pre and post synaptic neurones

A

Vesicles containing neurotransmitters only produced in pre-synaptic neurone
Neurotransmitter receptor proteins only to on post-synaptic neurone membrane

66
Q

Why are synapses needed

A

Electrical impulses can’t jump the gap between neurones

Impulses transmitted between neurones across a synapse using chemical messengers called neurotransmitters

67
Q

What is ACh

A

Acetylcholine
Neurotransmitter involved in the parasympathetic branch of the autonomic nervous system and cholinergic synapses
Diffuses from the pre-synaptoc neurone membrane to the post-synaptic neurone membrane
Bind to their complementary receptors on post-synaptic membrane

68
Q

How does the synapse work

A
  1. Action potential arrives at synaptic knob
  2. Causing voltage gated calcium ion channels in the pre-synaptic membrane to open
  3. Calcium ions diffuse into synaptic knob by facilitated diffusion since there is a higher concentration in the synaptic cleft
  4. Calcium ions activate enzymes that cause synaptic vesicles to move towards the pre-synaptic membrane
  5. Vesicles fuse with the pre-synaptic membrane and release ACh via exocytosis
  6. ACh diffuses down a concentration gradient and binds to specific ACh receptors on post-synaptic membrane
  7. Opening sodium ion channel proteins so sodium ions diffuse in
  8. If membrane reaches threshold potential then it depolarises the membrane and an action potential created
  9. Spreading along axon of post synaptic neurone
  10. Acetylcholinesterase hydrolysed ACh into choline and ethanic acid
  11. Which diffuse back across synaptic cleft and across the pre-synaptic neurone membrane
  12. ATP synthesised in mitochondria used to resynthesise ACh which is then stored in vesicles
69
Q

Pros of synapse

A

Prevents impulse going in the wrong direction

Filters out low level stimuli so if threshold isn’t reached at post synaptic neurone membrane no action potential generated
Preventing overstimulation
And a waste of valuable ATP

70
Q

Cons of synapse

A

Delays impulse slightly

71
Q

How does a neuromuscular junction work

A
  1. Action potential arrives at synaptic knob
  2. Causing voltage gated calcium ion channels in the pre-synaptic membrane to open
  3. Calcium ions diffuse into synaptic knob by facilitated diffusion since there is a higher concentration in the synaptic cleft
  4. Calcium ions activate enzymes that cause synaptic vesicles to move towards the pre-synaptic membrane
  5. Vesicles fuse with the pre-synaptic membrane and release ACh via exocytosis
  6. ACh diffuses down a concentration gradient and binds to specific ACh receptors on post-synaptic membrane
  7. Opening sodium ion channel proteins so sodium ions diffuse in
  8. If membrane reaches threshold potential then it depolarises the membrane and an action potential created
  9. Spreading along axon of post synaptic neurone and propagated along length of muscle fibre
  10. Acetylcholinesterase hydrolysed ACh into choline and ethanic acid
  11. Which diffuse back across synaptic cleft and across the pre-synaptic neurone membrane
  12. ATP synthesised in mitochondria used to resynthesise ACh which is then stored in vesicles
72
Q

What is a neuromuscular junction

A

Synapse between motor neurone and muscle cell
Using acetylcholine neurotransmitter
Which binds to nicotinic cholinergic receptors

73
Q

Differences between cholinergic synapse and neuromuscular junction

A

Receptors: Neuromuscular post synaptic membrane has more

Acetylcholinesterase: Neuromuscular post synaptic membrane folds to form lots of clefts that increase the surface area for more embedded enzyme

Response: When a motor neurone fires an action potential along response is always triggered in muscle cell but not the case for cholinergic synapses

74
Q

What are cholinergic synapses

A

Most synapses are cholinergic
Meaning they use acetylcholine as the neurotransmitter
Acetylcholine is the most abundant neurotransmitter

75
Q

How is the potential across membrane reversed when an action potential is produced

A

Sodium channel proteins close at +40mV
Potassium channel proteins open
Potassium ions diffuse out of the axon down a concentration gradient
Sodium/Potassium pump helps restore the ion distribution

76
Q

How does myelination affect nerve impulses

A

Impulse jumps from node to node
Depolarisation only at node
Since sodium ion/potassium ion diffusion can only occur where there is no myelin sheath at the nodes of ranvier
So action potential only occurs here
Fewer jumps/depolarisations to reach the length of the axon

77
Q

What is summation

A

Build up of neurotransmitter within the synapse

78
Q

Temporal summation

A

Different neurones converge at a single synapse
Action potential arrives from a number of different neurones
Occurring over the same time period
Causing the release of enough neurotransmitter to cause an action potential in the post synaptic neurone
May be a mixture of inhibitory and excitatory neurotransmitter

79
Q

Spatial summation

A

One pre synaptic neurone but impulses arrive in rapid succession
Giving a cumulative effect which is sufficient to depolarise the post synaptic neurone
Causing the release of enough neurotransmitter to cause an action potential in the post synaptic neurone

80
Q

What is fatigue

A

Rate of transmitter released is higher than the rate at which it is reformed
Pre synaptic neurone can’t release enough neurotransmitter to generate an action potential in post synaptic neurone until its regenerated

81
Q

What are excitatory neurotransmitters

A

Cause an action potential in the post synaptic neurone
By making the resting potential inside neurone less negative than the outside
So less sodium ions needed to reach threshold

82
Q

What are inhibitory neurotransmitters

A

Affect a different receptor on the post synaptic membrane
Resting potential becomes hyperpolarised/more negative
Post synaptic membrane less likely to reach threshold potential and generate an action potential

83
Q

2 ways drugs can affect synapses

A

Excitatory effect

Inhibitory effect

84
Q

How can drugs have an excitatory effect on synapses

A

Stimulate the nervous system by creating more action potentials in post synaptic neurone
Increase release of neurotransmitter
Inhibit enzyme that hydrolyses NET
Similar shape to NET so bind to receptors on post synaptic membrane and mimic NETS effect (agonist)

85
Q

How can drugs have an inhibitory effect on synapses

A

Create fewer action potentials on the post synaptic membrane
Inhibit the release of neurotransmitter
Hyperpolarise the membrane so resting potential becomes more negative and harder to reach threshold potential
Bind to and block receptors on the post synaptic membrane due to similar shape to NETS

86
Q

List some drugs

A 
Alcohol
Amphetamines
Cocaine
Codeine
Caffeine
Curare
Heroin
Nicotine
Valium
87
Q

Cocaine

A

Prevents hydrolysis of neurotransmitter involved in sympathetic branch of autonomic nervous system

88
Q

How do codeine and heroin work

A

Bind to endorphin receptors which are neurotransmitters involved in sensory nerve pathways and specifically pain pathways

89
Q

Valium

A

Increases the effects of GABA

90
Q

Caffeine

A

Reduces the threshold value for neurone excitation

91
Q

Nicotine

A

Similar shape to ACh

Binds to nicotinic cholinergic receptors

92
Q

Curare

A

Blocks ACh affects by blocking receptors at neuromuscular junctions
Muscles can’t be stimulated
Paralysis

93
Q

Alcohol

A

Inhibits neurotransmitter release from presynaptic neurone so fewer receptors activated

94
Q

Amphetamines

A

Stimulate neurotransmitter release from presynaptic neurone so more receptors activated

95
Q

Advantage of taxis/kinesis

A

Increased likelihood of returning to favourable conditions with better…

Food availability
Temperature
Less competition
Less predators

SPECIFIC TO Q

96
Q

Why do unmyelinated axons use more ATP than myelinated axons

A

ATP needed for active transport
In myelinated axons, active transport of sodium and potassium through the sodium potassium pump only takes place at the nodes of Ranvier
Whereas active transport occurs along the whole length of an unmyelinated axon

97
Q

Why do we need proteins to transport sodium and potassium

A

They are ions
So they are charged particles
Charged particles can’t cross the phospholipid bilayer unaided

98
Q

How does GABA inhibit nerve impulse transmission

A

Binds to receptors on post synaptic membrane
Opens chloride ion protein channels
Chloride ions diffuse in
Inside is more negatively charged than the outside (hyperpolarised)
Threshold not reached by stimulus
No depolarisation
Reduced effect of sodium ions entering

99
Q

What is an agonist

A

Binds to receptor
Similar shape to NET
Producing a similar response to intended neurotransmitter

100
Q

What is an antagonist

A

Binds to receptor
Similar shape to NET
Stopping it producing the correct response

101
Q

How is a resting potential maintained

A

Membrane relatively impermeable to sodium ions
Voltage gates sodium channels closed
3 sodium ions pumped out and 2 potassium ions pumped in by active transport via sodium potassium pump
Potassium ions diffuse out down their concentration gradient
Through leaky potassium channel proteins
Increased sodium outside the neurone
So inside more negative than outside

102
Q

Purpose of acetylcholinesterase

A

Hydrolyses acetylcholine into choline and ethanoic acid
So acetylcholine doesn’t stay bound to the receptor on the post synaptic neurone membrane and keep repeating action potentials/overstimulation
Choline and ethanoic acid diffuse back across synaptic cleft
Transported across the presynaptic membrane
ATP released from ATP hydrolysis by mitochondria used to resynthesise acetylcholine
Which is then stored in vesicles

103
Q

Advantage of mitochondria noting to the presynaptic membrane when nerve impulses arive

A

Causes calcium channel proteins to open
Calcium diffuses in
Causes vesicles to fuse with the membrane by activating enzymes

104
Q

Advantages of simple reflexes

A 
Rapid
Protect against damage to body tissue
Do not have to be learnt
Help escape predators
Enable homeostatic control
105
Q

How do synapses ensure nerve impulses only travel in one direction

A

Receptors only on the post synaptic neurone membrane

Neurotransmitters only made and stored and released from the pre synaptic neurone

A Level Biology Paper 2 (16 decks)

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