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Histology of the Nervous Tissue

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nervous system overview

Nervous systemMonitors and processes sensory information

from the environment and from within the body

Principal cell populationsNeuron - transmits impulsesNeuroglia - Support, protects and insulates the

nervous tissue

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Central Nervous TissueBrainSpinal cord

Peripheral Nervous TissueNerves

Neural tissue location

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The Anatomy of a Neuron

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Nissl bodies – clusters of RER and ribosomesDendrites

Receptive regionAxon or nerve fiber

Nerve impulse generator and transmitterAxon hillockAxon terminal or synaptic knobsCollaterals with telodendria

Neuron structure

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Neuron structure

Synaptic terminalsPresynaptic membraneSynaptic vesicles

neurotransmitterSynaptic cleftPostsynaptic membrane

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Neurons

They make up the gray matter of the nervous system

Clusters of cell bodies, dendrites, unmyelinated axons and neuroglias are called:Nuclei if they are located in the CNSGanglia if they are located in the PNS

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Axons or nerve fibers

Covered by myelinFatty material secreted by Schwann cells in

the PNSFatty material secreted by oligodendrocytes

in the CNSMyelin insulates the axons

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Axons or nerve fibersIn the PNS

The wrapping of the Schwann cell around the axon is called myelin sheath

NeurilemmaIt is the peripheral layer of the Schwann

cellIt contains the nucleus and most of the

organellesNodes of Ranvier

Gaps between Schwann cells

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Anatomical or structuralUnipolarBipolarMultipolar

Neuron classification

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A Structural Classification of Neurons

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FunctionalSensory neurons or afferent neurons

• deliver information from the body to the CNS

• Typically unipolar or bipolar• Body found in a ganglia (PNS)

Neuron classification

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Neuron classification

Motor neurons or efferent neurons• Carry impulse from the CNS to the

body• Typically multipolar• Body found in the CNS

Association (interneuron) neuron• Found between and sensory and a

motor neuron

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Structure of a nerve

DefinitionBundle of fibers wrapped in myelin and

connective tissue Located in the PNS

ClassificationSensory or afferent – going to the CNSMotor or efferent- going to the bodyMixed – carry sensory and motor fibers

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Structure of a nerve

The connective tissue that surrounds the fiber is calledEndoneurium-covers each nerve fiberPerineurium – covers a bundle of nerve fibers

The whole bundle is called fascicleEpineurium – covers the whole nerve

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Electroencephalography

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Electroencephalography - EEG

Measures brain activityAlpha waves = awake with eyes closed.

Resting.Alpha block

Beta waves = awake with eyes opened. Alert.Delta waves = normal during sleepTheta waves = normal children, abnormal in

adults

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