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Neuron and neurolgia, nervous system, Anatomy and Physiology
There are two main cell types in the nervous system: neurons and neuroglia. Neurons are excitable cells that conduct nerve impulses, while neuroglia provide support and insulation. Neuroglia, also called glial cells, make up about half the volume of the central nervous system and include astrocytes, oligodendrocytes, microglia, ependymal cells, and Schwann cells. Astrocytes help nourish neurons and form the blood-brain barrier, while oligodendrocytes and Schwann cells create myelin sheaths around axons. Neurons consist of a cell body, dendrites that receive signals, and an axon that conducts signals away.
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Neuron and neurolgia, nervous system, Anatomy and Physiology
- 1. NEUROGLIA (GLIA) & NEURON 5/13/2021 1 PREPARED BY, Mr.Vipin Chandran
- 2. CELLS OF THENERVOUS SYSTEM 5/13/2021 2 Two types of cells make up the nervous system: 1. Neuroglia: • Make up about half the volume of CNS. • They were “glue” that held nervous tissue together. 2. Neurons • Excitable 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 5/13/2021 3
- 4. TYPES OF NEUROGLIA 5/13/2021 4 1. Astrocytes 2.Microglia 3. Ependymal cells 4. Oligodendrocytes 5. Schwann cells 6. Satellite cells First 4 types are found in the CNS and remaining two present in PNS
- 5. 1. ASTROCYTES 5/13/2021 5 • Starshaped 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. 5/13/2021 6
- 7. 2. MICROGLIA 5/13/2021 7 •Small, usuallystationary 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 •They engulf and destroy micro organism and tissue debris •Although named as glia, are functionally and developmentally unrelated to nervous system cells
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- 9. 3. EPENDYMAL CELLS 5/13/2021 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 5/13/2021 10 •Smaller thanastrocytes 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. Oligodendroc yte Axon Nucleus Myelination in the CentralNervous System 5/13/2021 11
- 12. 5. SCHWANN CELLS 5/13/2021 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 inthe 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. 5/13/2021 13
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- 15. •Nerve cells withmany 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 5/13/2021 15
- 16. 6. SATELLITE CELLS 5/13/2021 16 • Itsurrounds cell bodies of neurons of PNS ganglia. • It regulate exchange of materials between neuronal cell bodies and interstitial fluid.
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- 18. 2. NEURONS 5/13/2021 18 •The humanbrain estimated to contain about 100 million , or 10% of total neurons of nervous system • Neuron consist of: i. Cell body ii. Axon iii. Dendrites iv. Axon ends
- 19. I. CELL BODY 5/13/2021 19 •Largest part of a nerve cell •Contain nucleus, cytoplasm and various organells like mitochondria and golgi apparatus •Also 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 packagedin vesicles that aid neurotransmission •Other 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 5/13/2021 20
- 21. II. DENDRITES 5/13/2021 21 •Branch extensivelyfrom 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
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- 23. III. AXON. 5/13/2021 23 •Extend fromtapered 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 telodendria and each terminate in a synaptic knob
- 24. •Site of communicationbetween 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. 5/13/2021 24
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- 26. CLASSIFICATION OF NEURON 5/13/2021 26 Structuralclassification 1. Multipolar 2. Bipolar 3. Unipolar Functional Classification 1. Afferent neurons (Sensory) 2. Efferent neurons (Motor) 3. Interneurons (Association)
- 27. STRUCTURAL CLASSIFICATIONL Classified accordingto number of extensions from cell body 1. Multipolar neurons: one axon but several dentrites, most of the neurons in brain and spinal cord are multipolar. 5/13/2021 27
- 28. 2. BIPOLAR NEURONS:One Axon And One Heavily Branched Dentrite, Least Numerous Kind And Found In Retina , Inner Ear And Olfactory Pathway 5/13/2021 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. 5/13/2021 29
- 30. FUNCTIONAL CLASSIFICATION 5/13/2021 30 Classified basedon direction of conduction of nerve impulse. 1.Afferent neuron: to spinal cord or brain 2.Efferent neuron: away from brain or spinal cord to muscle or gland 3.Interneurons: mainly located within the CNS between sensory and motor neuron.
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