1. Nervous Tissue 2 Originally Given By: Dr.Ahmed Attayeb Written By: Dr.Divine, Edited & Made up 2 date: Abo Malik Thanks for: DR.I

2. NEUROGLIA  Neuroglia are the supporting cells of the nervous tissue in the CNS. They can never transmit impulses.  Types of Neuroglia:- 1-Astrocytes 2-Oligodendrocytes 3-Microglia 4-Ependymal cells (NOTE):In contrast to Schwann cells that are in the PNS, these neuroglia are found only in CNS.

3. 1-Astrocytes  The largest of all neuroglia with a large nucleus  Have cytoplasmic processes which support neurons & the blood vessels  Form the Blood-brain barrier  Can divide & fill the places of damaged parts of CNS

4. Types of Astrocytes  There are two types: A)Protoplasmic astrocytes: Found in gray matter of CNS supporting the nerve cell bodies, the axons & the blood vessels. B)Fibrous astrocytes: Found in white matter supporting the axons & the blood vessels.

6. 2-Microglial cell  Found in gray & white matter  Small cell with oval nucleus  Short cytoplasmic processes  Phagocytic cell  Originate from monocytes in bone marrow

7. 3-Oligodendrocytes  Found in gray & white matter of the CNS  Small cells with few cytoplasmic processes  Each cytoplasmic process forms a separate myelin segment (internode)  Each oligodendrocyte forms myelin sheath for many axons in CNS

8. Oligodendrocyte

9. 4-Ependymal cells  Columnar Ciliated cells  Lining the ventricles of the brain & central canal of spinal cord  In the ventricles they secrete the cerebrospinal fluid.

10. Synapse  Synapse is the point of contract between the end of the axon & another neuron, muscle or gland cell  Synapse transmits impulses from the axon to another cell

11. Types of synapses  Chemical synapse:- (in CNS & PNS) Needs a chemical (neurotransmitter) to transmit impulses  Electrical synapse:- (Only in the CNS) as gap junctions between axon & the other neuron in CNS.

12. Chemical Synapse  There chemical synapse consists of four components: 1.Presynaptic membrane is the membrane of the end of the axon 2.Postsynaptic membrane is the membrane of the other cell e.g. Neuron 3.Synaptic cleft is a space between the two membranes 4.Synaptic vesicles in the axon secrete the neurotransmitter into the synaptic cleft

14. Types of Chemical Synapses  Axosomatic synapse It occurs between axon & cell body.  Axodendritic synapse It occurs between axon & dendrite.  Axoaxonic Synapse It occurs between axon & another axon.

15. NERVE ENDINGS  Terminations of axons in epithelium, CT or muscle There are 2 types of nerve endings:- A) Motor nerve endings (somatic OR autonomic) B) Sensory nerve endings (somatic OR autonomic)

16. 1-Somatic motor nerve ending Motor end Plate (Neuromuscular junction)  Synapse of a motor axon with a skeletal muscle fiber  The axon of a single neuron divides to supply more than 100 muscle fibers  Neuron cell body is in the CNS  Neuron & muscle fibers it supplies is called a motor unit

18. 2-Autonomic motor nerve endings  Synapses of axons in cardiac muscle, smooth muscle, or gland.  The cell bodies of these axons are located in autonomic ganglia.

19. B) Sensory nerve endings  Terminations of axons in epithelium, CT or skeletal muscle  The neuron cell bodies of these axons are located in the spinal & cranial nerve ganglia.  E.g: Pacinian corpuscle Muscle Spindle

20. Sensory Nerve Endings Pacinian corpuscle  Pressure receptor found in the skin  Oval in shape, covered by a CT capsule  The end of the axon is umyelinated in the center of the corpuscle  Many layers of flattened cells surround axon & there is tissue fluid between the layers

22. Sensory Nerve Endings Muscle spindle  Stretch receptor found in skeletal muscle  Cylindrical in shape & covered by a CT capsule  Contains small muscle fibers called intrafusal fibers surrounded by sensory axons  The muscle fibers outside the muscle spindle are called extrafusal muscle fibers supplied by motor axons