Basics of Neurohistology
Nerve tissue is needed in order to receive and react to information about changes in our internal and external environment.
Our nervous system can be split into 2 parts:
- CNS = Central nervous system = Nerve tissue in the cranial cavity and the spinal canal
- PNS = Peripheral nervous system = Nerve tissue outside of the cranial cavity and spinal canal
Nervous system — OpenStax — CC BY-SA 4.0
The CNS can be further divided into white and gray matter.
The simplest explanation is that gray matter is the neuron’s cell body, while the white matter is the axon itself (“conduction lines”).
White and gray matter distribution in the brain — Adapted from the work of Ms. Emma Vought — CC BY-SA 4.0
White and gray matter distribution in the spinal cord— OpenStax — CC BY-SA 4.0
Notice that the distribution of white and gray matter differs in the brain and spinal cord:
In the brain, white matter is located internally, while the gray matter is at the periphery. In the spinal cord, the opposite is true.
The two parts of our nervous system are derived from two sources:
- CNS cells are derived from neuroectodermal cells of the neural tube. (With one exception – Microglial cells [will be discussed later on] which come from the Yolk sac)
- PNS cells are derived from the cells of the neural crest.
Nerve tissue is composed of two cell populations:
- Neurons – Receive, process, transduce information.
- Neuroglial/Supporting cells – Offer physical protection, insulation, and repair.
We’ll cover the neurons and the neuroglial cells in the following chapters.