Neuroglia, syapse

Nervous system-Neuroglia and Synapse

1. Human Anatomy and Physiology-II Nervous system (Neuroglia , Synapse) Mr N.JEGAN Associate Professor K.M.COLLEGE OF PHARMACY. MADURAI.

2. Content 1.Neuroglia 2. Synapse

3. Neuroglia Neuro - Nerve cell Glial -Supporting cell Cells that provide metabolic support and immune protection for neurons Neuroglia do not generate or conduct nerve impulses. Neuroglial cell present 10-15 times more than neuron in our body. Unlike neurons, glial cells can regenerate if injured

4. Types of neuroglial cell There are two types neuroglial cell in our body 1.Central neuroglial cell- Present in central nervous system a. Astrocytes b. Ependymal Cells c. Microglial Cells (microglia) d. Oligodendrocytes 2.Peripheral neuroglial cell- Present in peripheral nervous system a. Schwann cells b. Satellite cells

5. Central neuroglial cell- Astrocytes Structure Astrocytes are star-shaped with fine branching processes neuroglial cells. It cover the cell body of neuron Location - Brain and Spinal cord Function 1.Supporting network in brain and spinal cord 2.play an important role in the formation of blood-brain barrier 3. Provide calcium and potassium and regulate neurotransmitter level in synapses.

6. Ependymal Cells Structure Epithelial ( Cuboidal ) like cell that form a single lining layer. Location ventricles of the brain and the central canal of the spinal cord. Function Production and regulation of CSF Cilia in the cell circulate CSF around the CNS .

7. Microglial Cells Structure Microglia are the smallest neuroglial cells. These cells are derived from monocytes and enter the tissues of nervous system from blood Location Brain and spinal cord. Function Engulf and destroy the microorganisms and cellular debris by means of phagocytosis in CNS .

8. Oligodendrocytes Structure It produce myelin sheath around the nerve fibers in CNS. It have only few processes, which are short. Location Brain and spinal cord. Function 1. Provide myelination around the nerve fibers in CNS 2. Provide support to the CNS neurons

9. Schwann cells Structure In myelinated axons of peripheral nerve, it form the myelin sheath Location Axon of peripheral nerve Function 1. Provide myelination around the nerve fibers in PNS 2. Remove cellular debris during regeneration

10. Satellite Cells Structure Satellite cells are small, flattened cells Location It is present in exterior surface of PNS neurons. Function 1. Provide physical support to the PNS neurons 2. Regulation of chemical environment of PNS neurons

11. Synapse

12. Synapse Synapse is the junction between two neurons. It is not an anatomical continuation. But, it is only a physiological continuity between two nerve cells

13. CLASSIFICATION OF SYNAPSE Synapse is classified by two methods: A. Anatomical classification B. Functional classification.

14. Anatomical classification It is formed by axon of one neuron ending on the cell body, dendrite or axon of the next neuron. 1.Axoaxonic synapse Axon of one neuron terminates on axon of another neuron 2. Axodendritic synapse Axon of one neuron terminates on dendrite of another neuron 3. Axosomatic synapse Axon of one neuron ends on soma (cell body) of another neuron

15. Functional classification   Functional classification of synapse is on the basis of mode of impulse transmission 1.Electrical Synapse Physiological continuity between the presynaptic and the postsynaptic neurons is provided by gap junction between the two neurons.

16. 2. Chemical synapse It is the junction between a nerve fiber and a muscle fiber or between two nerve fibers, through which the signals are transmitted by the release of chemical transmitter.

17. Properties Of Synapse 1.ONE WAY CONDUCTION The impulses are transmitted only in one direction in synapse, i.e. from presynaptic neuron to postsynaptic neuron 2.  SYNAPTIC DELAY It is a short delay that occurs during the transmission of impulses through the synapse. It is due to the time taken for Release of neurotransmitter , Passage of neurotransmitter and open ion channel 3.  Fatigue Fatigue at synapse is due to the depletion of neurotransmitter substance, acetylcholine

18. 4. SUMMATION Summation is the fusion of effects or progressive increase in the excitatory postsynaptic potential in post synaptic neuron when many presynaptic excitatory terminals are stimulated simultaneously. 5. Electrical properties Electrical properties of the synapse are the EPSP (Excitatory postsynaptic potential)and IPSP(Inhibitory postsynaptic potential)

19. FUNCTIONS OF SYNAPSE Main function of the synapse is to transmit the impulses, i.e. action potential from one neuron to another. However, some of the synapses inhibit these impulses. So the impulses are not transmitted to the postsynaptic neuron. Two types: 1. Excitatory synapses, which transmit the transmission impulses (excitatory function) 2. Inhibitory synapses, which inhibit the transmission of impulses (inhibitory function).

20. Excitatory function

21. Inhibitory function

22. Thank you