Neurons

A neuron is a specialized cell that transmits information throughout the nervous system through electrical and chemical signals.

• A neuron is composed of three parts: cell body, dendrites, ​and axon.
• The cell body contains cytoplasm along with cell organelle and granules known as Nissl’s granules.
• ​Dendrites are small fibers that project out of the cell body. They also contain Nissl’s granules. Its function is to transmit impulses toward the cell body.
• ​Axon is a long fiber, branched at the distal end. The axons transmit nerve impulses away from the cell body to synapse or to a neuro-muscular junction.
• ​Neurotransmitters are present in the synoptic knob present at the end of the axon.
• ​Axons are divided into three types based on the number of axons and ​dendrites.
  • Unipolar: cell body with​ one axon. Example: E​m​br​yonic stage.
  • Bipolar: one axon and one dendrite. Example: Retina of the eye
  • Multipolar: with one axon and two or more dendrites. Example: Cerebral cortex.

There are two types of axons, namely, myelinated and non-myelinated. 

• The myelinated nerve fibers are enveloped ​with Schwann cells. It forms a myelin sheath around the axon. For example, Spinal and cranial nerves. 
• Non​-myelinated fiber is enclosed by a Schwann cell that does not form a myelin sheath around the axon. ​Example: Autonomous and somatic neural systems. Nodes of Ranvier are the gaps between two adjacent myelin sheaths.

NCERT Notes for Class 11 Biology Chapter 18 – Neural Control and Coordination: The neural system controls and coordinates various ​functions, and homeostatic and metabolic activities of all the organs in the body. Neurons​​ are ​the ​functional unit of the neural system. The human nervous system is divided into two parts: The central nervous system (CNS) and the Peripheral nervous system (PNS). You will find neural control and coordination class 11 notes self-study here. Also, see the solutions of NCERT Class 11 Biology Chapter 18: Neural Control and Coordination.