Describe the structure of a neuron with a labelled diagram.
How to lay out the answer. Follow the frame, then write it in your own words.
1 · Define in one line. The neuron is the structural and functional unit of the nervous system. It carries messages as electrical impulses.
2 · Draw the neuron. [Diagram: cyton with nucleus and Nissl's granules, dendrites, long axon with myelin sheath, Schwann cells, nodes of Ranvier, axon terminals with synaptic knobs, arrow for direction]
3 · Explain the cyton and dendrites.
Cyton: cell body with nucleus, cytoplasm and Nissl's granules.
Dendrites: short branches that bring impulses towards the cyton.
4 · Explain the axon.
Axon: one long fibre that carries impulses away from the cyton.
Myelin sheath from Schwann cells insulates it; nodes of Ranvier are the gaps.
Axon terminals end in synaptic knobs that pass the message on.
5 · Add the types. Unipolar (one process), bipolar (two processes, e.g. retina) and multipolar (many dendrites, e.g. brain).
6 · Link to daily life. Sensory neurons tell you a mosquito is biting; vitamin B12 keeps the myelin sheath healthy.
7 · Close in one line. So each part of the neuron helps receive, carry or pass on a message.
Scoring tip: The diagram carries most of the marks. Label at least eight parts and draw an arrow for the direction of the impulse.
