Nervous Tissue

-the master integrating and coordinating system
-monitors and processes sensory info
-divided into central nervous system and peripheral nervous system

Central Nervous System

-consists of brain and spinal cord

Peripheral Nervous System

-includes all nervous elements located outside the central nervous system
*ex: nerves, sensory receptors, and some cluster of nerve cells

Nervous Tissue

-made up of neurons and neuroglia cells

Neuroglia/ Glial Cells

-serves the needs of the delicate neurons by bracing and protecting them
CNS: astrocytes, oligodendrocytes, microglial cells, and ependymal cells
PNS: Schwann cells and satellite cells

Microglial Cells

-acts as phagocytes

Oligodendrocytes & Schwann Cells

-myelinate the cytoplasmic extensions of the neurons

Astrocytes

-play a role in capillary-neuron exchanges and control the chemical environment around neurons

Neuron/Nerve Cells

-basic functional units of nervous tissue
-transmit messages from one part of the body to another in the form of nerve impulses

Cell Body of Neuron

-slender processes extend
-both the biosynthetic center of the neuron and part of its receptive region
-make up the gray matter of the CNS and form clusters there called nuclei and ganglia in PNS
-contains a large round nucleus surrounded by cytoplasm

Nuclei

-cluster of neuron cell bodies in CNS

Ganglia

-cluster of neuron cell bodies in PNS

Two structures found in the cytoplasm

Neurofibrils and Chromatophilic Substance

Neurofibrils

-provide support for the cell and a means to transport substances throughout the neuron

Chromatophilic Substance/Nissl Bodies

-an elaborate type of rough endoplasmic reticulum involved in the metabolic activities of the cell

Two Types of Neuron Processes.

1.Dendrites
2.Axons

Dendrites

-receptive regions that bear receptors for neurotransmitters released by the axon terminals of other neurons

Axons/Nerve Fibers

-form the impulse generating and conducting region of the neuron
-the white matter of the nervous system

Tracts

-bundles of axons in the CNS

Nerves

-bundles of axons in PNS

Neurons may have several dendrites, but they only have a single _____________.

Axon

Axon Collaterals

-branch off of the main axon forming more processes

Axon Hillock

-conical area of origin of the axon from the nerve cell body

Axon Terminals

club-shaped endings by which axons make synaptic contacts with other nerve cells or effector cells
-stores the neurotransmitter chemical in tiny vesicles

Synaptic Cleft

- a narrow extracellular cleft between the presynaptic and postsynaptic membranes

Neuromuscular Junction

-specialized synapses between neurons and skeletal muscles

Myelinated Fibers

-long nerve fibers that are covered by fatty material (myelin)

Axons in the PNS are typically heavily myelinated by special supporting cells called ______________.

Schwann Cells

Schwann Cells

-wrap themselves tightly around the axon in jelly roll fashion, this wrapping is the myelin sheath

Nodes of Ranvier

-gaps or indentations in the myelin sheath

Within the CNS myelination is accomplished by neuroglia called ________________.

Oligodendrocytes

Unipolar Neurons

-one very short process which divides into peripheral and central processes, extends from cell body

Bipolar Neurons

-have two processes attached to the cell body
-rare

Multipolar Neurons

-many processes

Sensory (Afferent) Nerves

- conduct impulses only toward the CNS

Motor (Efferent) Nerves

-carry impulses only away from the CNS

Mixed Nerves

-nerves carrying both sensory and motor fibers

Endoneurium

-delicate connective tissue enveloping individual nerve fibers

Perineurium

-sheath of connective tissue enclosing a bundle of nerve fibers
-forming fascicles

Epineurium

sheath of connective tissue around all fascicles of nerve fibers