1.
(a)
The graph below shows the changes in membrane potential of a myelinated nerve
fibre when a nerve impulse travels along it. The maximum depolarisation in the nerve
fibre is +40 mV.
+40
Membrane potential / mV
+20
0
1
2
3
4
5
6
Time / ms
–20
–40
–60
–80
(i)
On the graph, draw an arrow to show the time when the sodium ion channels open.
(1)
(ii)
Explain the meaning of the term myelinated.
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(2)
The Norton Knatchbull School
1
(iii)
State what effect myelination has on the speed of conduction.
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(1)
(b)
On the graph below show the changes in membrane potential of a nerve fibre, with a
resting potential of –60mV and a maximum depolarisation of +35mV, during the passage
of an impulse.
+40
Membrane potential / mV
+20
0
1
2
3
4
5
6
Time / ms
–20
–40
–60
–80
(2)
(Total 6 marks)
The Norton Knatchbull School
2
2.
Neurones transmit electrical impulses along their cell surface membranes when stimulated to do
so. These impulses are called action potentials and involve changes in the electrical potential
across the membranes due to movement of positive ions.
The diagram below shows the distribution of charge inside and outside an unmyelinated axon as
an impulse passes along.
Direction of impulse
+++++++++++++––––––+++++++++
––––––––––––––++++++–––––––––
Axon
––––––––––––––++++++–––––––––
+++++++++++++––––––+++++++++
D
(a)
C
B
A
Use the most suitable term from the list below to describe the state of the axon in regions
B, C and D. Region A has been done for you.
Depolarising
Resting
A
Resting
B
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C
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D
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Repolarising
(2)
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(b)
The diagram below shows two action potentials recorded using an oscilloscope.
+60
Membrane
potential
/ mV
+40
+20
0
–20
– 40
X
–60
–80
–100
0
1
2
3
4
5
6
7
8
9
Time/ m s
(i)
Explain how the change in membrane potential between 0.5 and 2.0 milliseconds is
brought about.
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(4)
The Norton Knatchbull School
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(ii)
Calculate the number of action potentials occurring per second. Show your
working.
Answer .................................. per second
(2)
(c)
Explain what is taking place during the period marked X on the diagram in part (b).
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(3)
(Total 11 marks)
The Norton Knatchbull School
5
3.
The diagram below shows one type of mammalian neurone.
Dendrite
Cell body
Node of Ranvier
Synaptic knob
(a)
(i)
Name the type and state the role of the neurone shown in the diagram.
Type: ................................................................................................................
Role: .................................................................................................................
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(2)
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(ii)
Draw an arrow on the diagram to show the direction in which an impulse would
travel.
(1)
(b)
State precisely where in the central nervous system the cell body of this type of neurone
is found and explain the importance of the dendrites.
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(2)
(c)
Describe the node of Ranvier and explain its importance in the neurone.
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(3)
(Total 8 marks)
The Norton Knatchbull School
7