Histology of the Nervous Tissue 1

nervous system overview Nervous system  Monitors and processes sensory information from the environment and from within the body Principal cell populations  Neuron - t ransmits impulses  Neuroglia - Support, protects and insulates the nervous tissue 2

Central Nervous Tissue  Brain  Spinal cord Peripheral Nervous Tissue  Nerves Neural tissue location 3

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The Anatomy of a Neuron 5

Nissl bodies – clusters of RER and ribosomes Dendrites  Receptive region Axon or nerve fiber  Nerve impulse generator and transmitter  Axon hillock  Axon terminal or synaptic knobs  Collaterals with telodendria Neuron structure 6

Synaptic terminals  Presynaptic membrane  Synaptic vesicles neurotransmitter  Synaptic cleft  Postsynaptic membrane 7

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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 CNS  Ganglia if they are located in the PNS 9

Axons or nerve fibers Covered by myelin  Fatty material secreted by Schwann cells in the PNS  Fatty material secreted by oligodendrocytes in the CNS  Myelin insulates the axons 10

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Axons or nerve fibers In the PNS  The wrapping of the Schwann cell around the axon is called myelin sheath  Neurilemma It is the peripheral layer of the Schwann cell It contains the nucleus and most of the organelles  Nodes of Ranvier Gaps between Schwann cells 12

Anatomical or structural  Unipolar  Bipolar  Multipolar Neuron classification 13

A Structural Classification of Neurons 14

 Functional Sensory neurons or afferent neurons deliver information from the body to the CNS Typically unipolar or bipolar Body found in a ganglia (PNS) Neuron classification 15

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 16

Structure of a nerve Definition  Bundle of fibers wrapped in myelin and connective tissue  Located in the PNS Classification  Sensory or afferent – going to the CNS  Motor or efferent- going to the body  Mixed – carry sensory and motor fibers 17

Structure of a nerve The connective tissue that surrounds the fiber is called  Endoneurium-covers each nerve fiber  Perineurium – covers a bundle of nerve fibers The whole bundle is called fascicle  Epineurium – covers the whole nerve 18

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Electroencephalography 20

Electroencephalography - EEG Measures brain activity  Alpha waves = awake with eyes closed. Resting. Alpha block  Beta waves = awake with eyes opened. Alert.  Delta waves = normal during sleep  Theta waves = normal children, abnormal in adults 21

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