Nervous Tissue

Neuroglia “Nerve Glue” (Support Cells) Neuroglia - nonconductiong cells that provide protection & support and assist with metabolism

Neuroglia “Nerve Glue” (Support Cells)

Oligodendrocytes - form the myelin sheaths, which wrap around neurons in the CNS to protect & insulate Schwann cells - form the myelin sheaths & neurilemma in neurons of the PNS

Neuroglia “Nerve Glue” (Support Cells) Microglia - spider shaped phagocytic cells of CNS; engulf & digest bacteria, foreign objects & dead cells Astrocytes - star shaped cells that help maintain the blood-brain barrier

Neuroglia “Nerve Glue” (Support Cells) Ependymal Cells - line cavities of the CNS and have cilia which help to circulate cerebrospinal fluid (CSF)

Glial Cells Activity

Neuron Video Clip

Neurons (nerve cells) Neuron - structural & functional unit of nervous tissue; cell body with many extensions or processes (nerve “fibers”) which conduct impulses

Neurons (nerve cells)

Neuron Structure Cell body (soma) - metabolic center of the neuron; contains the nucleus, neuroplasm & organelles such as Nissl bodies (rough ER for protein synthesis) and neurofibrils (provide support & transport proteins -Does not contain centrioles; neurons cannot divide (reproduce)

Neuron Structure Dendrites - short, numerous, and thickly branched extensions of the cell body (like tree roots) -Receive messages from other neurons and conduct the impulses toward the cell body = afferent process

Neuron Structure Axon - single, long, cylindrical tube with the same consistent diameter, runs through and out of the cell body(like a tail). End has many fine branches. -Carries impulses away from the cell body to another neuron or effector cell (muscle or gland) = efferent process

Other Parts of a Neuron Myelin sheath - pearly white, shiny lipid substances that cover the axon of many neurons; protects, insulates, & allows for faster conduction of impulses Neurilemma - delicate covering over myelin sheath (made by Schwann cells in PNS neurons); helps to repair damaged nerve processes

Other Parts of a Neuron Axis cylinder - central core of a nerve fiber - part which impulse travels down Nodes of Ranvier - indentations in the myelin sheath; important in the conduction process

What is the difference between a neuron & a nerve? Neuron = an individual nerve cell capable of conducting impulses Nerve = a group of individually insulated nerve cell fibers

Nerve Structure Individual nerve fiber wrapped by endoneurium --> Fascicle (group of nerve fibers) wrapped by perineurium --> Nerve (cord-like) wrapped by epineurium

Nerve Structure

White vs. Grey Matter White matter - nervous tissue that has a myelin sheath -mainly consists of axons & found in outer portion of spinal cord and inner part of brain

White vs. Grey Matter Grey matter - nervous tissue that lacks a myelin sheath -mainly consists of cell bodies on outer surface of brain & central portion of spinal cord

White vs. Grey Matter

Classification of Neurons Structural - # of processes = unipolar, bipolar, multipolar Functional - sensory, motor, or associative

Classification of Neurons

Types of Nerves Mixed - carry both sensory & motor fibers (like a two way street) Afferent (sensory) - carry only sensory fibers [like a one-way street to the brain/spinal cord] Efferent (motor) - carry only motor fibers [like a one way street from the brain/spinal cord]

Video Clip: Nerve Types

The End!