| Date | November 2016 | Marks available | 1 | Reference code | 16N.3.HL.TZ0.4 |
| Level | Higher level | Paper | Paper 3 | Time zone | TZ0 |
| Command term | State | Question number | 4 | Adapted from | N/A |
Question
Defects in the formation of synapses could be the cause of neurological disorders such as Alzheimer’s disease that affects the ability to think and remember clearly. It is more frequent in people older than 65 years of age. The graph shows the changes in synapse number over time. The diagram shows activity-related neural development.
State what happens to unused neurons.
Predict how mental activity might delay the onset of Alzheimer’s disease.
Autism appears early in life and affects how a person communicates and relates to others. There is evidence that autism could be caused by a surplus of synapses. Using all of the information provided, suggest two possible causes of a surplus of synapses in people with autism.
Markscheme
neuron pruning
OR
synapses removed
Do not accept “apoptosis”.
a. more synapses maintained with stimulation/mental activity/OWTTE
b. strong mental activity prevents «neuron» pruning
a. most synapses are formed during childhood/before birth
OR
first years of childhood most important for brain development
b. more synapses «than normal» may be formed «during childhood/before birth in autism»
c. «in autism» pruning of neurons does not occur «causing excess of synapses»
OR
normal synapse elimination does not remove extra synapses
