# Neural Tissue --- **Nervous tissue**, or **neural tissue** is the [[tissue]] that respond to [[biology#What Does It Mean To Be Alive|stimuli]] and sends electrochemical impulses to through [[nervous system]], where it eventually reaches and activates an **effector**, or a muscle or gland that reacts. There are two main cells that make up nervous tissue, [[neurons|neurons]], which conduct impulses from all over the body, and [[glial cells]], which support and take care of the neurons. ## Gray Matter & White Matter Neural tissue can generally be classified as **gray matter** or **white matter**. They are named for their appearance under the [[microscope]], as the delineations between gray and white matter in the central nervous system is quite stark, and reveals clues as to the nature of the tissue. **Gray matter** is made up of neural bodies, their dendrites, and [[myelination|unmyelinated]] axons. It typically acts to process signals received from the white matter, and makes up the nuclei of the CNS. **White matter** is made up of [[myelination|myelinated]] axons, which allow [[neurons#Saltatory Conduction|saltatory conduction]], and thus faster propagation of signals along the nerves and tracts of the nervous system. ## Signal Propagation Neurological signals travel between neurons by an *electrochemical* process. The "electro" part of this refers to [[action potential|action potentials]] which are significant changes in the charge of a neuron's plasma membrane can travel from one end of it to the other, triggering [[channel proteins#Gated Channels|voltage-gated channels]] that further propagate the action potential down the cell or initiate the release of a [[neurotransmitter]]. This neurotransmitter refers to the "chemical" part of "electrochemical". Individual neurons can communicate with one another by means of two different methods: an [[action potential]] or a [[graded potential]]. Action potentials are distinct actions, while graded potentials are are surges of change in electromagnetic charge, which can build up to trigger an action potential ## CNS vs PNS There are a couple important distinctions between the types of nervous tissue found in the [[central nervous system|CNS]] and the [[peripheral nervous system|PNS]]. - In the CNS a bundle of neuron axons called a **tract** and in the PNS it is called a **[[nerves|nerve]]**. - In the CNS [[myelination|myelination]] is done by glial cells called [[glial cells|oligodendrocytes]] and in the PNS it is done by [[glial cells|neurolemmocytes]]. ___