Fundamentals of the Nervous System and Nervous Tissue Chapter 11 Fundamentals of the Nervous System and Nervous Tissue Part A

Nervous System The master controlling and communicating system of the body Functions: 1-Sensory input – Figure 11.1

Nervous System 2-Integration – 3- Motor output – Figure 11.1

Organization of the Nervous System Central nervous system (CNS) Peripheral nervous system (PNS)

Two principal cell types Neurons – Supporting cells –

Supporting Cells: Neuroglia (glia) Provide a supportive scaffolding for neurons Segregate and insulate neurons

Astrocytes Figure 11.3a

Astrocytes Most abundant, versatile, and highly branched glial cells They cling to neurons and cover capillaries

Microglia and Ependymal Cells Figure 11.3b, c

Microglia and Ependymal Cells Ependymal cells – squamous- to columnar-shaped cells

CEREBROSPINAL FLUID- SHOWN CIRCULATING BY ARROWS Figure 7.17b Slide 7.47b Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

Protection of the Central Nervous System Figure 7.16a Slide 7.44a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

CEREBROSPINAL FLUID Slide 7.47b Figure 7.17b Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

Oligodendrocytes, Schwann Cells, and Satellite Cells IN CNS IN PNS Figure 11.3d, e

Oligodendrocytes – Schwann cells (neurolemmocytes) – Satellite cells-

Neuron Anatomy

Neurons (Nerve Cells) functions in: Composed of a body, axon, and dendrites Long-lived (over 100 yrs), amitotic, and have a high metabolic rate functions in: Electrical signaling Cell-to-cell signaling during development

Nerve Cell Body (Soma) nucleus - Nucleolus- Where outgrowth of neuronal processes There are no centrioles (amitotic nature) Nissl bodies- Axon hillock –

Processes Armlike extensions from the soma Called in the CNS Called in the PNS Two types:

Dendrites of Motor Neurons Short, tapering, and branched They are the receptive, or input, regions of the neuron

Axons: Structure Slender processes of uniform diameter arising from the hillock Long axons are called nerve fibers Usually there is only one unbranched axon per neuron Axonal terminal – branched terminus of an axon

Axons: Function Generate and transmit action potentials Secrete neurotransmitters from the axonal terminals

Neuron Classification Figure 7.6 Slide 7.15 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

Structural Classification of Neurons Multipolar neurons – Figure 7.8a Slide 7.16a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

Structural Classification of Neurons Bipolar neurons – Figure 7.8b Slide 7.16b Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

Structural Classification of Neurons Unipolar neurons – Figure 7.8c Slide 7.16c Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

Nodes of Ranvier (Neurofibral Nodes) Gaps in the myelin sheath between adjacent Schwann cells They are the sites where collaterals can emerge (see 1st neuron pic)

Myelin Sheath and Neurilemma: Formation Figure 11.5a-d

In MS, myelin is lost in multiple areas, leaving scar tissue called sclerosis. These damaged areas are also known as plaques or lesions.

Myelin sheath is green Axon is yellow

Myelin Sheath Whitish, fatty (lipoprotein), segmented sheath around most long axons It functions in:

Formed by Schwann cells in the PNS A Schwann cell: Envelopes an axon in a trough Encloses the axon with its plasma membrane Concentric layers of membrane make up the myelin sheath Neurilemma – remaining nucleus and cytoplasm of a Schwann cell

Unmyelinated Axons A Schwann cell surrounds nerve fibers but coiling does not take place SEE HW PG. 256 #12 A

Axons of the CNS Both myelinated and unmyelinated fibers are present Myelin sheaths are formed by Nodes of Ranvier are widely spaced

Regions of the Brain and Spinal White matter – Gray matter – Basal nuclei –

Gray matter White matter