Section I The Cells and It's Basic Changes of Nervous System I.Neuron The neuron is a pyramidal cell with a rounded nucleus and prominent nucleolus. The granularity of the cytoplasm is imparted by rough endoplasmic reticulum(Nissl substance).Section I The Cells and It’s Basic Changes of Nervous System I. Neuron The neuron is a pyramidal cell with a rounded nucleus and prominent nucleolus. The granularity of the cytoplasm is imparted by rough endoplasmic reticulum (Nissl substance)