Question 20N.3.HL.TZ0.4
| Date | November 2020 | Marks available | [Maximum mark: 5] | Reference code | 20N.3.HL.TZ0.4 |
| Level | HL | Paper | 3 | Time zone | TZ0 |
| Command term | Describe, Suggest | Question number | 4 | Adapted from | N/A |
The image on the left shows a developing neuron on the first day of culture (day 1). The image on the right shows the same neuron after one day (day 2).
[Source: The establishment of polarity by hippocampal neurons
in culture, CG Dotti, CA Sullivan and GA Banker, Journal of Neuroscience 1 April 1988, 8 (4) 1454–1468;
DOI: https://doi.org/10.1523/JNEUROSCI.08-04-01454.1988, Copyright ©1988 Society for Neuroscience.]
Describe the changes occurring in this neuron from day 1 to day 2.
[2]
a. branches (of dendrites/axons) formed
OR
new/more dendrites formed;
b. dendrites/axons grow/get longer;
Many candidates could describe at least one change occurring, but many used terminology for processes occurring at later stages that were not shown on the photographs.
Suggest other processes that may occur during neural development.
[2]
a. neural tube differentiation/formation;
b. neuron (may) migrate to other parts;
c. axon (may) extend beyond the neural tube/myelinates;
d. synapses develop;
e. neural pruning;
Do not accept “connection” instead of “synapse”.
Most candidates suggested correctly at least one other process, and stronger candidates suggested two.
Suggest what can happen to neurons that are unused in the nervous system.
[1]
a. neural pruning;
b. neurons are destroyed / apoptosis
The vast majority of candidates correctly suggested neural pruning.
