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A Level Biology > Nervous Coordination (Topic 6B) > Flashcards

Nervous Coordination (Topic 6B) Flashcards

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1
Q

what is the value for resting potential?

A

-70mV

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2
Q

how is resting potential established?

A
  1. 3 Na out 2 K in via Na/K pump
  2. more Na outside than K inside, creating chemical gradient
  3. Na try naturally diffuse in but most gates are closed so can’t and K diffuse out naturally
  4. generating further distance and charge & electro and chemical gradient
  5. equilibrium met between electric and chemical gradients
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3
Q

describe how the resting potential is established in an axon by the movement across the membrane

2 marks

A

pump of Na+ out the axon
diffusion of K+ out the axon

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4
Q

why can sodium and potassium ions can only cross the axon membrane through proteins?

2 marks

A
  1. cannot pass through phospholipid bilayer
  2. because the ions are water soluble
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5
Q

the membrane is depolarised at what value?

A

+ 40mV

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6
Q

what is a nerve impulse?

A

a self propagating wave of electrical disturbance

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7
Q

when the membrane is hyper polarised the value is?

A

below -70mV

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8
Q

how does the membrane go from depolarised to hyper polarised?

A

the voltage dependent Na channels close and voltage dependent K channels open and K+ leave axon repolarising membrane

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9
Q

how does the membrane go from hyper polarised to polarised?

A

voltage dependent K channels close and K+ diffuse back in

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10
Q

when a neurone transmits a series of impulses, why does its rate of oxygen consumption increase?

A

more respiration
more energy supplied
for active transport of ions

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11
Q

why does a myelinated axon conduct impulses faster than a non-myelinated axon?
3 marks

A
  1. in myelinated action potential only at nodes
  2. the sheath makes the impulse jump from node to node
  3. action potential doesn’t have to travel along the whole length
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12
Q

what factors affect the speed of nerve impulse conduction?

A

temperature
myelin sheath presence
axon diameter

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13
Q

pre synaptic neurones…

A

send messages

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14
Q

the post synaptic neurone…

A

recieves messages

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15
Q

cholinergic synapses use…

A

acetylcholine

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16
Q

the properties of an action potential are…

A

• have a threshold
• all or nothing
• all the same size
• have a refractory period

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17
Q

what is the refractory period?

A

where channels remain closed so no further depolarisation occurs which ensures they are separate and only go in one direction

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18
Q

describe what is meant by the all or nothing principle

A

once the threshold is reached an action potential will always fire with the same change in voltage no matter the size of the stimulus

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19
Q

how does action potential change for a bigger stimulus?

A

action potentials are fired more frequently

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20
Q

how does axon diameter affect speed of conduction? why?

A

the bigger the diameter the quicker they are conducted.

because there is less resistance to the flow of ions than in the cytoplasm of a smaller axon so reached other parts of the neurone quicker

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21
Q

how does temperature affect speed of conduction? why?

A

as temperature increases, speed of conduction increases

because ions diffuse faster
(until denaturing)

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22
Q

the synaptic knob contains….

A

synaptic vesicles filled with neurotransmitter

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23
Q

what are the 3 steps for a nerve impulse to travel across a synapse?

A
  1. arrival of an action potential
  2. fusion of the vesicles
  3. diffusion of acetylcholine
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24
Q

at cholinergic synapses,
when action potential arrives at the synaptic knob what happens?

A

stimulates voltage-gated calcium ion channels in the presynaptic neurone to open so Ca+ diffuse into the knob

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25
Q

at cholinergic synapses,
when fusion of the vesicles occurs what happens?

A

the influx of Ca+ into the knob causes synaptic vesicles fuse with the presynaptic neurone. the vesicles release acetylcholine into the synaptic cleft by exocytosis

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26
Q

at cholinergic synapses,
when acetylcholine diffuses what happens?

A

ACh diffuses across synapse and binds to specific cholinergic receptors on the post synaptic membrane causes sodium ion channels to open and move in causing depolarisation. an action potential is generated if the threshold is reached

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27
Q

what do exitatory neurotransmitters do?

A

depolarise the postsynaptic membrane, making it fire an action potential if the threshold is reached

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28
Q

what do inhibitory neurotransmitters do?

A

hyperpolarise the postsynaptic membrane, preventing it from firing action potential

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29
Q

an inhibitory synapse is…

A

a synapse where inhibitory neurotransmitters are released from the presynaptic neurone following an action potential

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30
Q

summation is…

A

where the sum total of lots of smaller impulses triggers an action potential

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31
Q

the two types of summation are…

A

spatial
temporal

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32
Q

spatial summation is…

A

where 2 or more presynaptic neurones release their neurotransmitters at the same time onto the same post synaptic neurone

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33
Q

temporal summation is….

A

where 2 or more nerve impulses arrive in quick succession from the same presynaptic neurone

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34
Q

is action potential more likely with spatial or temporal summation?

A

temporal

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35
Q

a neuromuscular junction is…

A

a specialised cholinerguc synapse between a motor neurone and muscle cell

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36
Q

neuromuscular junstions use which neurotransmitter?

A

acetylcholine

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37
Q

how do nueromuscular junctions work?

4 marks

A
  1. ACh released from vesicles in presynaptic membrane
  2. ACh diffuses across the synaptic cleft and binds to receptors on the post synaptic membrane
  3. this triggers an action potential if threshold is reached
  4. ACh is broken down in the synpatic cleft by acetylcholineesterase
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38
Q

what are the 3 differences between a neuromuscular junction and other synapses?

A
  1. the postsynaptic membrane has lots of folds that form clefts that store AChE
  2. postsynaptic membrane has more receptors than other synapses
  3. ACh is always exitatory, so a respinse is alomst always caused
39
Q

some drugs are agonists and…

A

activate more receptors

40
Q

some drugs are antagonists and…

A

block receptors so they can’t be activated by neurotransmitters. so fewer receptors can be activated

41
Q

some drugs inhibit the enzyme that breaks down neurotransmitters means that there is…

A

more neurotransmitters in the synaptic cleft to bind to receptors and they’re there for longer

42
Q

some drugs stimulate the release of neurotransmitter from the presynaptic neurone ….

A

so more receptors are activated

43
Q

some drugs inhibit the release of neurotransmitters from the presynaptic neurone so…

A

fewer receptors are activated

44
Q

the three types of muscle in the body are…

A

smooth muscle
cardiac muscle
skeletal muscle

45
Q

the role of skeletal muscle is to…

A

produce movement

46
Q

anatgonistic pairs are…

A

pairs of muscles that work together to move a bone. the agonist contract and the antagonist relaxes

47
Q

one muscle fibre is made up of…

A

myofibrils

48
Q

muscle fibres have lots of mitochondria to provide….

A

ATP for muscle contraction

49
Q

muscles are made up of…

A

many muscle fibres

50
Q

myofibrils contain bundles of…

A

thick and thin myofilaments

51
Q

thick myofilaments are made of…

A

myosin

52
Q

thin myofilaments are made of…

A

actin

53
Q

dark bands in a myofibril are…

A

thick myosin filamnets and some overlapping thin actin filaments

54
Q

light bands in a myofibril are…

A

actin filaments only

55
Q

each myofibril is made up of…

A

sarcomeres

56
Q

the ends of each sarcomere are marked with a..

A

Z line

57
Q

in the middle of each sarcomere there in an…

A

M line

58
Q

the M line is the middle of…

A

the myosin filaments

59
Q

around the M line there is a…

A

H zone

60
Q

the H zone only contains…

A

myosin filaments

61
Q

the A band is the…

A

dark band - thick myosin filaments and some overlapping thin actin filaments

62
Q

the I band is the..

A

light band - actin filaments only

63
Q

what happens in the sliding filament theory?

A

myosin and actin filaments slide over each other to make the sarcomeres contract

64
Q

after muscle contraction sarcomeres return…

A

to their original length

65
Q

in the sliding filament theory of muscle contraction which band stays the same length?

A

A band

66
Q

in the sliding filament theory of muscle contraction which band gets narrower?

A

I band

67
Q

in the sliding filament theory of muscle contraction which zone gets narrower?

A

H zone

68
Q

when muscles contract the Z lines…

A

get closer together meaning the sarcomeres get shorter

69
Q

myosin filaments have…

A

globular heads that are hinged

70
Q

myosin filaments are hinged so they…

A

can move back and forth

71
Q

each myosin head has…

A

a binding site for actin and a binding sitefor ATP

72
Q

actin filaments have…

A

binding sites for myosin heads called actin-myosin binding sites

73
Q

what other protein is found between actin filaments?

A

tropomysoin

74
Q

what does tropomyosin do?

A

helps myofilaments move past each other

75
Q

the 4 stages in muscle contraction are….

A
  1. arrival of action potential
  2. movement of the actin filament
  3. breaking of cross bridge
  4. return to resting state
76
Q

the bond formed when a myosin head bind to an actin filament is called….

A

actin-myosin cross bridge

77
Q

slow twitch muscle fibres contract…

A

quickly

78
Q

slow twitch muscle fibres can work for…

A

long periods of time

79
Q

what are slow twitch muscle fibres used for?

A

long distance running

80
Q

which type of respiration works alongside slow twitch fibres

A

aerobic

81
Q

do slow twitch muscle fibres have lots of little mitochondria and blood vessels?

A

lots

82
Q

why do slow twitch muscle fibres have lots of mitochondria and blood vessels?

A

to supply the muscles with oxygen

83
Q

are slow twitch muscle fibres rich in myoglobin?

A

yes

84
Q

fast twitch muscle fibres contract…

A

quickly

85
Q

fast twitch muscle fibres work for…

A

short periods of time

86
Q

what are fast twitch muscle fibres used for?

A

sprinting

87
Q

do fast twitch muscle fibres have lots of little mitochondria and blood vessels?

A

little

88
Q

do fast twitch fibres have lots of myoglobin?

A

no

89
Q

give evidence for the sliding filament theory…

  • distance between Z lines shortens
  • I band gets narrower
  • H zone becomes narrower
A
  • distance between Z lines shortens
  • I band gets narrower
  • H zone becomes narrower
90
Q

if a myosin molecule was unable to bind to another myosin molecule why would muscle contraction be prevented
3 marks

A

cannot form myosin
cannot move actin
can’t move actin towards each other

91
Q

explain the role of ATPase during muscle contraction

2 marks

A
  1. ATPase breaks ATP down ATP to be used for energy
  2. (energy is) used to form actomyosin bridges
92
Q

describe how stimulation by nerve impulse starts the movement of actin filament

(6 marks)

A
  1. calcium ions
  2. bond to tropomysin
  3. revealing binding site on actin
  4. myosin binds to exposed sites on actin
  5. cross bridges form between actin and myosin
  6. activates ATPase
93
Q

after death cross bridges between actin and myosin remain firmly bonded, why?

2 marks

A
  1. no ATP produced
  2. to seperate actin and myosin

A Level Biology (19 decks)

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