histologyofthenervoussystem-140905044427-phpapp02-200729202123.ppt
- 1. HISTOLOGY OF THE HISTOLOGY OF THE NERVOUS SYSTEM NERVOUS SYSTEM (AN OVERVIEW) (AN OVERVIEW) Dr. SAHAR HAFEEZ Dr. SAHAR HAFEEZ drsaharhafeez@yahoo.com drsaharhafeez@yahoo.com
- 2. Learning Objectives Learning Objectives The students should be able to; The students should be able to; Enlist the names & functions of different Enlist the names & functions of different types of Neurons types of Neurons Enlist the names & functions of different Enlist the names & functions of different types of Neuroglia types of Neuroglia Demonstrate an understanding towards the Demonstrate an understanding towards the structural differences structural differences of of neurons and neuroglia neurons and neuroglia Define the terms Define the terms Ganglia Ganglia & & Nuclei Nuclei and and Gray & White Matters Gray & White Matters. . Demonstrate an understanding towards the arrangement of different Demonstrate an understanding towards the arrangement of different layers layers of a typical nerve of a typical nerve. .
- 3. ANATOMICAL ORGANIZATION of the ANATOMICAL ORGANIZATION of the NERVOUS SYSTEM NERVOUS SYSTEM Nervous System CNS PNS ANS BRAIN SPINAL CORD CRANIAL NERVES SPINAL NERVES SYMPATHETIC PARA- SYMPATHETIC
- 4. Cell types present in the Nervous System Cell types present in the Nervous System Nervous tissue is made up of 2 types of cells; Nervous tissue is made up of 2 types of cells; Neurons Neurons (structural & functional unit) (structural & functional unit) Neuroglia Neuroglia (Supporting cells) (Supporting cells)
- 5. Parts of a Neuron Parts of a Neuron Cell body: Cell body: Trophic unit Trophic unit Dendrites: Dendrites: Receptive unit Receptive unit Axon: Axon: Conductive unit Conductive unit
- 6. Perikaryon/Cell Body /Soma Perikaryon/Cell Body /Soma “ “part of a neuron that encloses the nucleus and other organelles part of a neuron that encloses the nucleus and other organelles necessary to maintain and repair the neuron”. necessary to maintain and repair the neuron”. Cell Body Organelles Cell Body Organelles Nucleus Nucleus Golgi apparatus Golgi apparatus RER RER Ribosomes (=Nissl substance) Ribosomes (=Nissl substance)
- 7. Perikaryon/Soma/Nerve cell body Perikaryon/Soma/Nerve cell body Most neurons have their cell bodies located in different parts of Most neurons have their cell bodies located in different parts of CNS CNS Clusters of cell bodies in the CNS are known as Clusters of cell bodies in the CNS are known as Nuclei Nuclei Clusters of cell bodies in PNS are known as Clusters of cell bodies in PNS are known as Ganglia Ganglia
- 8. Axon Characteristics Axon Characteristics Carries information to another neuron or muscle cell. Carries information to another neuron or muscle cell. Often relatively long. Often relatively long. Single (one per neuron). Single (one per neuron). Ends in short branched processes called Ends in short branched processes called telodendria. telodendria. May have collateral branches. May have collateral branches. Covered by neurolemma m Covered by neurolemma made up of Schwann cells. ade up of Schwann cells. Note: axon is the only part of a neuron that Note: axon is the only part of a neuron that is ever myelinated. is ever myelinated. Myelin Sheath Telodendria
- 9. Dendrites (Characteristics) Dendrites (Characteristics) Carry information to the cell body. Carry information to the cell body. Usually multiple. Usually multiple. Relatively short. Relatively short. Often branched. Often branched. Have receptors for Have receptors for neurotransmitters. neurotransmitters. Conduct local potentials. Conduct local potentials.
- 10. Relationship B/W Axon & Dendrites Relationship B/W Axon & Dendrites
- 11. Classification of Neurons Classification of Neurons Neurons are classified according to; Neurons are classified according to; Structure Structure Unipolar/Pseudo unipolar neurons Unipolar/Pseudo unipolar neurons Bipolar neurons Bipolar neurons Multipolar neurons Multipolar neurons Function Function Sensory neurons Sensory neurons Motor neurons Motor neurons Association neurons Association neurons
- 12. Structural Classification of Neurons Structural Classification of Neurons Pseudo unipolar Neurons: Pseudo unipolar Neurons: Present in the dorsal root Present in the dorsal root ganglia of spinal cord ganglia of spinal cord Bipolar Neurons Bipolar Neurons: : Present in Present in the Olfactory epithelium of the Olfactory epithelium of nose as well as in the Retina nose as well as in the Retina of eye of eye Multipolar Neurons Multipolar Neurons: : Present Present everywhere else. everywhere else.
- 13. Functional Classification of Neurons Functional Classification of Neurons Sensory (afferent) Neurons: Sensory (afferent) Neurons: Transmit impulses from the Transmit impulses from the sensory peripheral receptors to sensory peripheral receptors to CNS CNS Motor (efferent) Neurons: Motor (efferent) Neurons: Carry impulses away from Carry impulses away from CNS to peripheral organs CNS to peripheral organs Association/Inter-Neurons: Association/Inter-Neurons: Present only in the CNS and Present only in the CNS and transmit impulses across the transmit impulses across the neurons of CNS neurons of CNS
- 14. Neuroglia = Neuroglia = nerve glue nerve glue Distinguished by their much smaller size as compare to Distinguished by their much smaller size as compare to neurons. neurons. Outnumber neurons in CNS by 9:1 ratio. Outnumber neurons in CNS by 9:1 ratio. Are mainly of six types: Are mainly of six types: 4 of them are found in CNS 4 of them are found in CNS Astrocytes Astrocytes Microglia Microglia Oligodendrocytes Oligodendrocytes Ependymal cells Ependymal cells 2 of them are found in PNS 2 of them are found in PNS Satellite cells Satellite cells Schwann cells Schwann cells
- 15. Neuroglia of CNS Neuroglia of CNS Astrocytes= Astrocytes= star-shaped star-shaped Derived from neuroblast cells. Derived from neuroblast cells. Most abundant type of glial cells Most abundant type of glial cells Function to physically support neurons. Function to physically support neurons. Brace the neurons & anchor them to Brace the neurons & anchor them to the near by capillaries (create BBB) the near by capillaries (create BBB)
- 16. Neuroglia of CNS Neuroglia of CNS Oligodendrocytes: Oligodendrocytes: Derived from neuroblast cells. Derived from neuroblast cells. Function to myelinate axons within CNS. Function to myelinate axons within CNS. Microglia: Microglia: Derived from embryonic mesenchyme. Derived from embryonic mesenchyme. May transform into phagocytes within CNS May transform into phagocytes within CNS Ependymal Cells: Ependymal Cells: Derived from neuroblast cells. Derived from neuroblast cells. Line ventricles of brain & central canal of Spinal cord. Line ventricles of brain & central canal of Spinal cord. (The protective role of Microglia is very important as cells of (The protective role of Microglia is very important as cells of the immune system are denied across the CNS) the immune system are denied across the CNS)
- 17. Neuroglia in the PNS Neuroglia in the PNS Schwann Cells: Schwann Cells: Derived from neural crest Derived from neural crest cells. cells. Myelinate axons in the PNS. Myelinate axons in the PNS. Satellite Cells: Satellite Cells: Surround nerve cell body Surround nerve cell body May aid in controlling May aid in controlling neuronal chemical neuronal chemical environment environment
- 19. Myelination of Axons Myelination of Axons • Myelin protects & electrically insulates the fibers • In CNS, Axons are myelinated by ‘oligodendrocytes • In PNS, Axons are myelinated by ‘Schwann cells’. • Schwann cells myelinate the fibers like a jelly roll. • One Axon in PNS is myelinated by many Schwann cells. • The gap b/w individual Schwann cells is k/a ‘Node of Ranvier’
- 21. Epineurium: Epineurium: Outermost Outermost connective tissue sheet connective tissue sheet covering all the bundles of covering all the bundles of fibers in a nerve. fibers in a nerve. Perineurium: Perineurium: Middle Middle connective tissue sheet connective tissue sheet covering individual bundle of covering individual bundle of fibers. fibers. Endoneurium: Endoneurium: Innermost Innermost sheet covering the individual sheet covering the individual Axon of each fiber in a Axon of each fiber in a bundle. bundle. Coverings of a Typical Peripheral Nerve
- 22. Ganglia Ganglia Button-shaped enlargements with in the PNS produced by a collection of neuron cell bodies. Functionally speaking, Ganglia are the relaying station outside CNS. Unipolar cell bodies are found in spinal/Dorsal root ganglia Multipolar cell bodies are found in autonomic ganglia
- 23. White & Grey Matter of CNS White & Grey Matter of CNS White Matter: Areas of CNS mostly made up of Myelinated axons (as the myelin is white colored) Grey Matter: Areas of the CNS mostly made up of somas of neurons. Arrangement of white & grey matter; In the Spinal cord: White matter outside & Grey matter inside In the Brain: Grey matter outside & white matter inside. Some isolated clusters of grey matter embedded within the inner white matter (Nuclei)
- 24. THANK YOU THANK YOU & & BEST OF LUCK BEST OF LUCK