Biyo-Tek Günlüğüm…

Structure and Types of Neurons

The nervous system contains a complex network of nerve cells, or neurons.

Neurons are specialized cells that transmit information throughout the body.

Neurons enable many important functions, such as movement, perception, thought, emotion, and learning.

Structure of Neurons

Neurons consist of three important parts:

1. Dendrites
2. Cell Body
3. Axons

Dendrites which extend from the cell body of the neuron, are the “antennae” of the neuron.

Dendrites receive information from other cells.

Cell bodies are enlarged parts of the neurons from which dendrites and axons project. They contain the nuclei of the cells.

An axon is a long membrane-covered extension of the cytoplasm that conducts nerve impulses.

The ends of an axon are called axon terminals.

Bundles of axons are called nerves.

Insulated Neurons

Many neurons have a layer of insulation on their axon called a myelin sheath formed by the cell membrane of Schwann cells.

Tiny gaps among myelin sheath are called Nodes of Ranvier.

The presence of myelin causes nerve impulses to move faster down the axon.

The speed of impulse conduction is also related to axon diameter. A large-diameter axon conducts impulses faster than a small-diameter axon, assuming both axons are either myelinated or unmyelinated.

Types of Neurons

Neurons can be grouped according to their projections and functions.

Types of neurons according to their projections from the cell body

1. Unipolar neuron: Only one short projection
2. Bipolar neuron: One axon and one dendrite
3. Multipolar neuron: Numerous dendrites and usually one axon

Types of Neurons according to their function

1. Sensory neurons send information from sense organs to CNS (Central nervous system, brain and spinal cord)
2. Motor Neurons send commands from CNS to muscles or glands
3. Inter neurons are between sensory neurons and motor neurons