OCR General Certificate of Secondary Education (GCSE) Biology Practice Exam

What is an axon?

1. A cell body of a neuron

2. A part of the sensory neuron only

3. A long extension of the cytoplasm

4. A gap between neurons

The correct answer is: A long extension of the cytoplasm

An axon is indeed defined as a long extension of the cytoplasm of a neuron. It serves a critical role in the nervous system by transmitting electrical impulses away from the neuron's cell body. This structure allows for effective communication between neurons and ultimately across the nervous system, facilitating the transmission of signals over long distances. Furthermore, the axon's design contributes to its functionality; it is often insulated by a myelin sheath that enhances the speed and efficiency of signal transmission. This is essential for quick responses and coordination of bodily functions. The cell body of a neuron contains the nucleus and other organelles, but it is not the axon itself. An axon is present in both sensory and motor neurons, not just in sensory neurons. Lastly, the gap between neurons is referred to as a synapse, which is a different component of neuronal communication.