The diagram given below depicts a defect of the human eye which has been corrected by using a suitable lens. Answer the following questions: The diagram given below depicts a defect of the human eye which has been corrected by using a suitable lens. Answer the following questions:
Draw a neat, labelled diagram of a neuron.
Topic: Neuron — diagram
Answer
Your diagram must show: • CYTON (cell body) containing the NUCLEUS • DENDRITES — short, numerous, branched processes arising from the cyton • AXON — a single long process leading away • MYELIN SHEATH covering the axon, with NODES OF RANVIER as gaps and SCHWANN CELLS along it • AXON TERMINALS (nerve endings) at the far end
Labels required: dendrite, cyton, nucleus, axon, myelin sheath, node of Ranvier, axon terminal.
WHAT THE SHAPE MUST SHOW, because this is where diagrams go wrong: DENDRITES are SHORT, MANY and BRANCHED, clustered at the cell body the AXON is SINGLE and LONG, extending away from it Drawing several long processes, or branching the axon at its base, loses the mark however neat the drawing.
THE FUNCTIONAL LOGIC: dendrites are the "ears" of the neuron, RECEIVING impulses; the axon is the "mouth", CARRYING them away. Information travels dendrite → cyton → axon, never the reverse.
The MYELIN SHEATH insulates the axon so that the impulse LEAPS from one node of Ranvier to the next, greatly speeding transmission — which is why the nodes are worth drawing.