Neuron and neurolgia, nervous system, Anatomy and Physiology

this will be beneficial for bsc nursing and msc nursing students

1. NEUROGLIA (GLIA) & NEURON 04-Mar-21 1 PREPARED BY, Mr. Vipin Chandran

2. CELLS OF THE NERVOUS SYSTEM 04-Mar-21 2 Two types of cells make up the nervous system: Neuroglia : Make up about half the volume of CNS. They were “glue” that held nervous tissue together. 2 . Neurons Ex c itable cells that conduct impulses It respond to stimulus and convert it into action potential.

3. 1.Neuroglia or Glia Neurolgia are smaller than neuron. They are 5 to 25 times more numerous. Glia do not generate or propagate action potentials. Glia means ‘glue’ They can multiple and divide in the mature nervous system 04-Mar-21 3

4. Types of N eur o glia 04-Mar-21 4 Astrocytes Microglia Ependymal cells Oligodendrocytes Schwann cells Satellite cells First 4 types are found in the CNS and remaining two present in PNS

5. 1. Astrocytes 04-Mar-21 5 Star shaped glia (greek: astron -star) Found only in CNS Largest and most numerous type of glia Tiny delicate points extend through brain tissue attaching neurons and tiny blood capillaries ‘Feed’ neurons by taking up glucose from blood, converting to lactic acid and giving to neurons It contain microfilament that give strength to neuron.

6. Endothelial cells creates “blood brain barrier” which restricts movement of substance between blood and interstitial fluid of the CNS. It help to maintain chemical environment for generation of nerve impulse. It also play role in learning and memory. 04-Mar-21 6

7. 2. Microglia 04-Mar-21 7 Small, usually stationary cells found in CNS Also known as Brain’s immune cells In inflamed or degenerating brain tissue, microglia enlarge, move about, and carry on phagocytosis T hey engulf and destroy micro organism and tissue debris Although named as glia, are functionally and developmentally unrelated to nervous system cells

8. 04-Mar-21 8

9. 3. Ependymal cells 04-Mar-21 9 They are cuboidal to columnar cells arranged in single layer posses microvilli and cilia. Thin sheets that line fluid filled cavities in brain and spinal cord. It produce, monitor, and assist circulation of CSF.

10. 4. Oligodendrocytes 04-Mar-21 10 Smaller than astrocytes and have fewer processes Oligo -few, dendro -branch, cyte -cell : meaning " cells with fewer branches " Some lie clustered around nerve cell body, some arranged in rows between nerve fibre in brain and spinal cord Help hold nerve fibre together Important function : produce fatty myelin sheath around nerve fibre of CNS

11. O li g o d e n d roc yte A x on Nuc l e u s Myelination in the Central Nervous System 04-Mar-21 11

12. 5. Schwann cells 04-Mar-21 12 Found only in PNS Also called as ‘ Neurolemmocytes ’ Like oligodendrocytes , they form myelin sheath around axons. Support nerve fibre and form myelin sheath around them Many schwann cells wrap around single neuron Myelin sheath is formed by layers of Schwann cell membrane containing

13. Microscopic gaps in the sheath, between adjecent Schwann cell- Node of Ranvier or myelin sheath gaps The myelin sheath and gaps in nerve fibre are important for transfer of nerve impulses Schwann cell’s nucleus and cytoplasm are squeezed to perimeter to form neurilemma. neurilemma important for regeneration of injured nerve fibres. 04-Mar-21 13

14. Node of Ran v ier 04-Mar-21 14

15. Nerve cells with many Schwann cells attached and having thick myelin sheath -White fibre or Myelinated fibre Several nerve fibres held by single Schwann cell and does not wrap around to form thick myelin sheath – Grey fibre or Unmyelinated fibre 04-Mar-21 15

16. 6 . S atellite cells 04-Mar-21 16 It surrounds cell bodies of neurons of PNS ganglia. It regulate exchange of materials between neuronal cell bodies and interstitial fluid.

17. Node of Ran v ier 04-Mar-21 17

18. 2. Neurons 04-Mar-21 18 The human brain estimated to contain about 100 million , or 10% of total neurons of nervous system Neuron consist of: Cell body Axon Dendrites Axon ends

19. i. Cell body 04-Mar-21 19 Largest part of a nerve cell Contain nucleus, cytoplasm and various organells like mitochondria and golgi apparatus A lso called as " perikaryon " or “soma” ; meaning surrounding the nucleus Plasma membrane encloses the whole neuron . RER and attached ribosomes provide proteins for neuron . Some of the proteins are processed .

20. Neurotransmitters are proteins packaged in vesicles that aid neurotransmission O ther proteins used for repair of neuron Mitochondria replicate themselves in the cell body: some transported to end of axon to provide energy for signal transduction Cluster of RER termed Nissl Bodies 04-Mar-21 20

21. ii. Dendrites 04-Mar-21 21 Branch extensively from cell body like tiny tree Greek word : tree Distal end of sensory neurons called receptors : receive stimuli that initiate nerve signals some dendrites in brain have knoblike dendritic spines: serve as connection point of other

22. 04-Mar-21 22

23. ii i . Axo n . 04-Mar-21 23 Extend from tapered portion of cell body called axon hillock Conduct impulse away from cell body. Axon has side branches called Axon collaterals Distal ends of axon form branches called teloden d ria and each terminate in a synaptic knob

24. S ite of communication between two neuron and a effectors cell is called synapse. Both synaptic end bulb and varicosities contains tiny membrane enclosed sacs called synaptic vesicles that store chemical neurotransmitters . 04-Mar-21 24

25. 04-Mar-21 25

26. Classification of Neuron 04-Mar-21 26 Structural classification Multipolar Bipolar Unipolar Functional Classification Afferent neurons (Sensory) Efferent neurons (Motor) Interneurons (Association)

27. Structural Clas s ificatio n l Classified according to number of extensions from cell body 1. Multipolar neurons: one axon but several dentrites , most of the neurons in brain and spinal cord are multipola r . 04-Mar-21 27

28. 2. Bipolar neurons: One Axon And One Heavily Branched Dentrite , Least Numerous Kind And Found In Retina , Inner Ear And Olfactory Pathway 04-Mar-21 28

29. 3. Unipolar neuron : single process extending from the cell body, which branches into central process (towards CNS) and peripheral process (away from CNS), process forms a single axon and conducting impulse away from dentrite, they are always sensory neurons. 04-Mar-21 29

30. Functional Classification 04-Mar-21 30 Classified based on direction of conduction of nerve impulse. Afferent neuron: to spinal cord or brain Efferent neuron: away from brain or spinal cord to muscle or gland Inter n euron s : mainly located within the CNS between sensory and motor neuron.

31. 04-Mar-21 31