Biology · Oct / Nov 2021 · Paper 42 · Question 4
0610
As printed in the paper
The question as text
Involuntary actions occur because nerve impulses travel along the components of reflex arcs. An example of an involuntary action is the rapid movement of a hand after unexpectedly touching a very hot object. Fig. 4.1 shows the structures that are involved in the movement of the hand. hot object V W Z Y X U Fig. 4.1
Read automatically from the paper; the printed page above is exact.
Show the answer and mark scheme
4(a)[5]
one mark for each row:
letter
function
name
on Fig.
4.1
conducts impulses to
sensory / afferent, neurone
V
CNSconducts impulses to
motor / effector / efferent,
Y
an effectorneurone
conducts impulses
relay / connector
X
within the CNS/ intermediate, neurone
detects / senses,
stimulus / change in
receptor
U
temperaturecontracts / causes
biceps / muscle /
movement / carry out
Z
effectorresponse
4(b)[4]
any four from:
1
vesicles move towards end of, pre-synaptic neurone / axon / AW ; 2
vesicles fuse with (pre-synaptic) membrane ;
3
(named) neurotransmitter released ;
4
neurotransmitter diffuses across, synapse / gap / synaptic cleft ; 5
neurotransmitter binds to receptor, on post-synaptic neurone ;
6
impulse (generated) in post-synaptic neurone ;
7
AVP ;
4(c)[1]
blinking / pupil reflex / iris reflex / accommodation / corneal reflex / tear reflex / AVP ;
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