Final answer:
Neurons are classified as unipolar, bipolar, or multipolar based on the number of processes extending from the cell body. Unipolar neurons in humans are actually pseudo-unipolar sensory neurons found in ganglia, bipolar neurons are typically found in sensory organs, and multipolar neurons, with multiple dendrites, are most common in the central nervous system.
Step-by-step explanation:
What determines whether a neuron is unipolar, bipolar, or multipolar is the number of processes extending from the cell body. A unipolar neuron has a single process that extends from the soma and is found in insects where they stimulate muscles or glands. In humans, these neurons are termed pseudo-unipolar and are sensory neurons found in ganglia. Their axons branch into two extensions; one connected to dendrites for sensory reception and another that transmits information to the spinal cord.
Bipolar neurons, with one axon and one dendrite, are typically found in sensory organs such as the retina. An example is a retinal bipolar cell that receives signals from photoreceptor cells.
Multipolar neurons, the most common type, have one axon and multiple dendrites and are predominant in the central nervous system, including the brain and spinal cord. As an example, Purkinje cells in the cerebellum are multipolar and have many branching dendrites.