Histology of the Nervous Tissue 1 nervous system

Histology of the Nervous Tissue 1

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

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

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The Anatomy of a Neuron 5

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

Neuron structure l Synaptic terminals ¡Presynaptic membrane ¡Synaptic vesicles lneurotransmitter ¡Synaptic cleft ¡Postsynaptic membrane 7

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Gray Matter l 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

White Matter l Axons are covered by myelin insulation ¡Fatty material secreted by: l Schwann cells in the PNS l Oligodendrocytes in the CNS 10

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Axons or Nerve Fibers l. Myelinated axons are called: l. Tract if they are located in the CNS l. Nerve if they are located in the PNS l. Nodes of Ranvier l. Gaps between myelin sheath 12

Neuron classification l Anatomical or structural ¡Unipolar ¡Bipolar ¡Multipolar 13

A Structural Classification of Neurons 14

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

Neuron classification l. Motor neurons or efferent neurons • Carry impulse from the CNS to the body • Typically multipolar • Body found in the CNS l. Association (interneuron) neuron • Found between and sensory and a motor neuron 16

Structure of a nerve l Definition ¡Bundle of fibers wrapped in myelin and connective tissue ¡Located in the PNS l 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 l The connective tissue that surrounds the fiber is called ¡Endoneurium-covers each nerve fiber ¡Perineurium – covers a bundle of nerve fibers l. The whole bundle is called fascicle ¡Epineurium – covers the whole nerve 18

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Electroencephalography 20

Electroencephalography - EEG l Measures brain activity ¡Alpha waves = awake with eyes closed. Resting. l. 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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