Biological Systems MCAT Practice Exam

What distinguishes a bipolar neuron from other types?

1. It has two axons

2. It has only one dendrite

3. It has multiple synapses

4. It has no myelin sheath

The correct answer is: It has only one dendrite

A bipolar neuron is characterized by having two distinct processes emanating from its cell body: one axon and one dendrite. This structure is specifically adapted for certain types of sensory functions, such as in the retina of the eye and olfactory system. The correct option highlights that a bipolar neuron has only one dendrite, emphasizing its unique feature of having a single, specialized dendritic process to receive information, which distinguishes it from multipolar neurons that typically have multiple dendrites extending from the cell body. This configuration allows for more direct communication and integration of sensory signals. In contrast, other neuron types, such as unipolar neurons, have a single process that bifurcates into axonal and dendritic components, but they do not conform to the bipolar structure. Similarly, while it is true that some neurons may have multiple synapses or axons, bipolar neurons specifically do not fit that description. Lastly, the presence or absence of a myelin sheath is not a distinguishing feature of bipolar neurons, as myelination can vary between different types of neurons. Thus, the defining characteristic of a bipolar neuron is the presence of one axon and one dendrite, confirming the accuracy of the choice that highlights its unique structural feature.