7.Nervous Tissue1.ppt
- 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:- 1. Cell body (Perikaryon) 2. 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
- 8. 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)
- 10. Types of Axons 1. Myelinated axon (with myelin sheath) may be sensory or motor 2. Unmyelinated axon (without myelin sheath) may be sensory or motor All types of axons in PNS are supported by cells called Schwann cells
- 11. 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
- 12. 1. Myelinated Axon 1.Each Schwann cell forms one segment of myelin sheath around the axon called internode 2.Each internode is about 200-1000 μm long 3.Between internodes is a gap called node of Ranvier where there is no myelin sheath
- 13. 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
- 17. 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
- 19. Structure of Peripheral Nerve Contains parallel bundles of axons Each bundle contains myelinated & umyleinated axons Contains motor & sensory axons Mo nerve cell bodies
- 20. 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
- 24. Ganglia Ganglia are groups of neuron cell bodies outside the CNS Types of ganglia:- 1. Dorsal root (spinal) ganglia 2. Autonomic ganglia (e.g. Sympathetic ganglia)
- 26. 1. 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
- 28. 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