The document describes the structure and function of neurons and the nervous system. It discusses how neurons are able to transmit signals via nerve impulses. When a neuron is stimulated, it causes depolarization of the membrane through ion exchange, initiating an action potential. This potential then propagates along the axon. At synapses, neurotransmitters transmit signals between neurons. The document also explains reflex arcs which allow for rapid involuntary responses through defined pathways and different types of reflexes.