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Nervous Tissue

Nervous Tissue. Originally Written By: Dr. Mohammad Al-Attayeb Typed in the Computer By: Abo Malik Thanks 4 : Dr.I. Nervous Tissue. One of the four basic tissues Generates, conducts & transmits impulses In CNS (brain & spinal cord) In PNS (nerves & ganglia. Components of Nervous Tissue.

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Nervous Tissue

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  1. Nervous Tissue Originally Written By: Dr. Mohammad Al-Attayeb Typed in the Computer By: Abo Malik Thanks 4: Dr.I

  2. Nervous Tissue • One of the four basic tissues • Generates, conducts & transmits impulses • In CNS (brain & spinal cord) • In PNS (nerves & ganglia

  3. Components of Nervous Tissue • Neurons (Nerve cells) • Neuroglia (Supporting cells)

  4. Neuron (Nerve Cell) • Consists of:- • Cell body (Perikaryon) • Cytoplasmic processes:- • Dendrites • Axon

  5. The Neuron Cell Body • Large basophilic cell body • Abundant RER called Nissl bodies in cell body & dendrites but absent in axon • Large nucleus with euchromatin & prominent nucleolus • Neurons do not divide

  6. Types of Neurons According to the number of processes arising from the cell body:- 1. Bipolar:- Two processes (olfactory epithelium) 2. Multipolar:- More than two processes (e.g. sympathetic ganglia) 3. Pseudounipolar:- One process dividing into two (e.g. spinal ganglia)

  7. Types of Axons • Myelinated axon (with myelin sheath) may be sensory or motor • Unmyelinated axon (without myelin sheath) may be sensory or motor All types of axons in PNS are supported by cells called Schwann cells

  8. Schwann Cells • The Schwann cells of myelinated axon in PNS form myelin sheath around the axon • In the unmyelinated axon a Schwann cell supports several axons without forming myelin sheath • Schwann cells have a basal lamina

  9. Myelinated Axon • Each Schwann cell forms one segment of myelin sheath around the axon called internode • Each internode is about 200-1000 μm long • Between internodes is a gap called node of Ranvier where there is no myelin sheath

  10. What Is Myelin Sheath • Myelin sheath is concentric layers of the Schwann cell membrane around the axon • It contains the lipids & proteins of the cell membrane of the Schwann cell

  11. CELL BODY Muscle Fiber

  12. 2. Umyelinated Axons • Successive Schwann cells surround the axon without forming myelin sheath • Many axons are found in deep grooves on the surface of a single Schwann cell • They are smaller than myelinated axons

  13. Structure of Peripheral Nerve • Contains parallel bundles of axons • Each bundle contains myelinated & umyleinated axons • Contains motor & sensory axons • Mo nerve cell bodies

  14. Connective Tissue of the Nerve • Epineurium:- external layer of dense irregular CT covering the nerve • Perineurium:- layers of flat cells with tight junctions & basal lamina around each bundle of axons • Endoneurium:- innermost layer of reticular CT around each Schwann cell covering the axon

  15. Ganglia • Ganglia are groups of neuron cell bodies outside the CNS • Types of ganglia:- • Dorsal root (spinal) ganglia • Autonomic ganglia (e.g. Sympathetic ganglia)

  16. Dorsal Root Ganglion(Spinal Ganglion) • Contains pseudounipolar neurons in groups • Each neuron is surrounded by a capsule of supporting cells called satellite cells • Contains myelinated axons • Sensory ganglion

  17. Sympathetic Ganglion • Contains multipolar neurons separated by spaces containing unmyelinated axons • Capsule of satellite cells is not prominent • It is a motor ganglion • Contains synapses

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