Question 19M.3.SL.TZ1.5
| Date | May 2019 | Marks available | [Maximum mark: 7] | Reference code | 19M.3.SL.TZ1.5 |
| Level | SL | Paper | 3 | Time zone | TZ1 |
| Command term | Explain, Outline | Question number | 5 | Adapted from | N/A |
Explain the neural control of swallowing.
[3]
a. voluntary passage of food through the mouth ✔
b. «bolus of» food touches the walls of the pharynx ✔
c. nerve sends message/impulse to brain ✔
d. swallowing centre in the medulla «oblongata» ✔
e. now involuntary/unconscious/autonomic responses/reflexes ✔
f. triggers closing of epiglottis «to prevent choking» ✔
g. leading to contraction of muscles/peristalsis «in the pharynx and esophagus» ✔
Very few candidates recognized the voluntary aspect of swallowing. The role of the medulla and consequent involuntary action were most often described, although answers were frequently quite muddled.
Neurons are initially produced by differentiation in the neural tube. Outline the mechanisms of axon and synapse development that follow the initial creation of neurons.
[4]
a. axons are extensions of the neuron cell body ✔
b. some axons grow out of the neural tube and connect to other parts of the developing embryo ✔
c. chemical stimuli affect axon growth ✔
d. more dendrites form ✔
e. axon reaches the target cell ✔
f. forms single/multiple synapse«s» ✔
g. neural pruning involves the loss of neurons/synapses ✔
Do not accept migration of neurons
The question was often not read properly, with answers describing formation and migration of neurons, and chronological steps were rarely seen. Most answers receiving credit involved synapse formation and neural pruning.