Cambridge International A Level Biology Revision Guide

Chapter 15: Coordination
3 Which of the following is responsible for saltatory conduction in myelinated neurones?
A axon membranes
B nodes of Ranvier
C Schwann cells
D voltage-gated channel proteins [1]
4 Which of the following correctly identifies the effects of the three plant hormones, abscisic acid (ABA), auxin and
gibberellin?
A
Abscisic acid Auxin Gibberellin
elongation growth of roots
and shoots
stomatal closure
stem elongation
B
stimulates synthesis of
amylase in seed germination
stem elongation
acidification of cell walls
C stomatal closure acidification of cell walls
stimulates synthesis of amylase
in seed germination
D
stem elongation
elongation growth of roots and
shoots
stomatal closure
5 Which statements about the concentrations of hormones in the human menstrual cycle are correct?
1 Shortly before ovulation, the concentration of oestrogen is high and concentration of progesterone low.
2 During the last quarter of the cycle, the concentrations of oestrogen and progesterone fall.
3 At the end of menstruation, the concentration of oestrogen is low but rising, and the concentration of
progesterone is low.
4 Just before ovulation, the concentrations of LH and FSH suddenly rise.
A 1, 2, 3 and 4 B 1, 2 and 4 only C 2 and 3 only D 3 and 4 only [1]
6 The figure shows the changes in potential difference across the membrane of a neurone over a period of time. The
membrane was stimulated at time A and time B with stimuli of different intensities.
[1]
359
Potential difference across membrane
of a neurone / mV
+60
+40
+20
0
–20
–40
–60
–80
C
D
E
threshold
a
b
Stimulus B resulted in an action potential.
Describe what is occurring at C, D and E. [6]
Suggest why stimulus A did not result in an
action potential being produced whereas
stimulus B did. [2]
[Total: 8]
0 1
stimulus stimulus
A B
2 3 4 5
Time / ms
Cambridge International AS and A Level Biology 9700/04, Question 8, October/November 2007