Draw a labelled diagram of a motor neuron.

Explain how an impulse passes along the membrane of a neuron.

Describe the process of endocytosis.

Award [1] for each of the following clearly drawn and correctly labelled.

a. cell body – shown with a nucleus;

b. nucleus correctly labelled;

c. axon – shown as double line longer than the longest dendrite;

d. myelin sheath/Schwann cells – surrounding the axon;

e. nodes of Ranvier – shown in axon;

f. dendrites – shown extending from the cell body;

g. motor end plates – not covered by myelin sheath and ending with buttons/dots;

a. resting potential is –70mV / relatively negative inside in comparison to the outside;

b. Na^+/K⁺ pumps maintain/re-establish (the resting potential);

c. more sodium ions outside than inside (when at the resting potential);

d. more potassium ions inside than outside (when at the resting potential);

e. nerve impulse is an action potential that stimulates a (wave of) depolarization along the membrane/axon;

f. if neuron is stimulated/threshold potential/–50mV is reached sodium ion channels open;

g. sodium ions diffuse/move in;

h. (Na⁺ move in) causing depolarization;

i. potassium ion channels open / potassium ions diffuse/move out;

j. (K⁺ move out) causing repolarization;

k. local currents / description of Na⁺ ion diffusion between depolarized region and next region of axon to depolarize;

Accept any of the above points clearly explained in an annotated diagram.

a. (plasma) membrane encloses/engulfs solid particles/droplets of fluid/molecules;

b. fluidity of the membrane allows endocytosis;

c. (plasma) membrane forms pit/forms indentation/pulled inwards/invaginates;

d. membrane pinches off /seals back on itself/edges fuse;

e. vesicle/vacuole formed;

f. inside of plasma membrane becomes outside of vesicle membrane / converse;

g. vesicle breaks away from plasma membrane/moves into cytoplasm;

h. active process / endocytosis/vesicle formation requires energy;

Accept any of the above points clearly described in an annotated diagram.

Most gained good marks for the diagram, which were generally of a good standard.

Most could explain the resting and action potential at a point on the axon. However only the best candidates could explain how it is propagated along the axon.

Better candidates could explain endocytosis in detail. Weaker candidates confused it with exocytosis or just described molecules passing through the membrane. The word vesicle should be used for the structure formed by the membrane.