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Histology of Nervous Tissue. PROF. DR. FAUZIAH OTHMAN DEPT OF HUMAN ANATOMY. Feature of nerves tissue Type of cell: neuron & neuroglia General feature of neuron Type of neuroglia: astrocyte, oligodendrocyte, ependymal cell, microglia Synapses Myelin – formation & function
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Histology of Nervous Tissue PROF. DR. FAUZIAH OTHMAN DEPT OF HUMAN ANATOMY
Feature of nerves tissue • Type of cell: neuron & neuroglia • General feature of neuron • Type of neuroglia: astrocyte, oligodendrocyte, ependymal cell, microglia • Synapses • Myelin – formation & function • General structure of peripheral nerves • Ganglia – dorsal root ganglia • & autonomic ganglia
Nervous system divided into: • Central nervous system (CNS) Brain and spinal cord • Peripheral nervous system (PNS) • Cranial and spinal nerves – locate outside the CNS.
Morphology oftypical neuron • Neuronfunctional cell of the nervous tissue. • Cell body or perikaryon - contains the nucleus – regulates the functioning of the neuron. • Numerous dendrites and a single axon. • Contains Nissl bodies in the cytoplasm • Axon hillock- no Nissl bodies • Axon – cellular process (extension) – carries impulses away from the cell body. • Dendrites – cellular process (extension) – carries impulses toward the cell body
2 types of cell i) Neurons (nerve cells) ii) Supporting cells Functions of neurons • specialized to receive stimuli and to conduct electrical impulses to other parts of the system. • Arranged as an integrated communications network, with several neurons in a chain-like fashion involved in sending impulses from one part of the system to another.
Neuron Classification • Structural: • Multipolar – most common type in CNS. • Include all motor neurons and interneurons of brain and spinal cord. • Bipolar- not as common purely sensory. • Retina of eye, inner ear, olfactory epithelium in the upper region of nose. • Unipolar (formerly known as pseudounipolar) • Sensory neurons found in numerous craniosacral ganglia of the spinal cord.
Unipolar neuron Nucleus & nucleolus Cytoplasm fibrocytes Satellite cells Cytoplasm of neuron Myelinated axons
The supporting cells (neuroglia or glia): • Astrocytes • Oligodendrocytes • Microglial cells • Ependymal cells • Schwann cells • Satellite cells CNS PNS
Astrocytes • Largest, most numerous, versatile, and highly branched glial cells • They cling to neurons and cover capillaries • Functionally, they: • Support and brace neurons • Anchor neurons to their nutrient supplies • Guide migration of young neurons • Control the chemical environment
Microglia • Microglia – smallest, ovoid cells with spiny processes - phagocytic cells that migrate through the CNS and remove foreign and degenerated material
Ependymal Cells • Ependymal cells – squamous- to columnar-shaped cells • They line the central cavities of the brain and spinal column
Oligodendrocytes • Oligodendrocytes – branched cells that wrap CNS nerve fibers - Produce myelin in CNS
Schwann Cells and Satellite Cells • Schwann cells (neurolemmocytes) – form myelin sheaths around peripheral axons • Satellite cells surround neuron cell bodies with ganglia
Synapse • The region where the terminals come close to another cell and transmit the impulse • A junction that mediates information transfer from one neuron: • To another neuron • To an effector cell • Presynaptic neuron – conducts impulses toward the synapse • Postsynaptic neuron – transmits impulses away from the synapse
Myelin – formation & function • Whitish, fatty (protein-lipid), segmented sheath around most long axons • Its function: • Protection of the axon • Electrically insulating fibers from one another • Increasing the speed of nerve impulse transmission
2 types of neuroglia produce myelin • CNS= Oligodendrocyte • PNS= Schwann cells