Which of the following best defines a neuron?

A neuron is best defined as a specialized cell that transmits nerve impulses. This definition captures the primary function and role of neurons in the nervous system, where they are responsible for receiving, processing, and transmitting information through electrical and chemical signals. Neurons are essential for conveying messages between different parts of the body and play a critical role in all nervous system activities, including reflexes, sensory processing, and coordinating responses to stimuli.

Other options define different types of cells or functions within the body. The cell responsible for muscle contraction refers to muscle fibers, which are not neurons. Supportive cells in the nervous system are known as glial cells, which provide support and protection for neurons but do not transmit impulses themselves. Receptor cells in the sensory system are specialized for detecting specific stimuli, such as light or sound, but they also do not fulfill the primary role of transmitting nerve impulses as neurons do. Therefore, the most accurate and encompassing description of a neuron is that it is a specialized cell transmitting nerve impulses.