Done By :- Gharam AL-Khalaileh Yaqeen yousef

Transcription

1 و Done By :- Gharam AL-Khalaileh Yaqeen yousef This file contain DOCTOR SPEECH & SLIDE Page 1

2 We have in neurosysem two type of cell: 1- Neuron that carry action potential. 2- Supported cell for neuron. The most complex system in the human body. Formed by network more than 100 million neuron. Each neuron has a thousand interconnection a very complex system for communication. Nerve tissue is distribute throughout the body, anatomically divide into : CNS & PNS. Structurally consist : nerve cells & glial cells Glial cell like a connective tissue for the neuron. Brain and spinal cord the only organs consist of one type of cell in the body. Cells of Nervous System Page 2

3 Structure of Neuron Principle cells of Nervous Tissue. Consist of 3 parts : CELL BODY (perikaryon/soma) A single AXON Multiple DENDRITES µm Neuron is an active cell ( the most active cell in the body ). Its cromatin not condense, also it has very basophilic nucleolus. Rest cell, their chromatin dense ( we cannot see nucleolus ).. Cell Body (Perikaryon) Central portion of the cell. Generally are polygonal. Different shape and size characteristic regions of nervous system. Contain : Nucleus Perinuclear cytoplasm Cells that produce protein has : - Rough ER. - Pretend nucleolus. Page 3

4 Ultrastructure of Neuron Nucleus : large, spherical to ovoid and centraly located. a single prominent nucleolus. Finely dispersed chromatin. Cytoplasm: Abundantof R.E.R Polyribosomes Basic dyes (a+b) Nissl Bodies lots of S.E.R. Golgi bodies (perikaryon) protein secreting cell Page 4

5 Many mitochondria, most abundant in axon terminal Extensive cytoskeleton axonal transport One centriole do not undergo cell divisions Receiving stimuli Dendrite and Axon Single process up to 100 cm Originate from axon hillock Devoid ribosome Axon: Dilatation of distal portion axon terminal end bulbs synapse conducting impulse away from the soma Axonal transport Multiple elongated processes Dendrites: Cytoplasmic~perikaryon (devoid golgi complex) Page 5

6 Neurons Classification According to the size and shape of the processes: Multipolar: the most abundant, Ex: pyramidal cells, Purkinje cells. **It has cell body, a lot of dentrites, one single axon. Bipolar: Ex: visual, auditory system. It is found in the sensory cells. It has 2 process ( one axon and one dentrites). Pseudounipolar: Ex: sensoryganglia. It has single small process, it seems like multiple process so it is called pseudounipolar. According to the size and shape of the processes According to their function: Sensory Neuron (afferent): It takes the impulse from skin and send it to CNS. CNS= central nervous system. Receive sensory input conduct impulses to CNS Motor Neuron (Efferent): Page 6

7 CNS conduct impulses to muscles, glands and other neurons Interneuron: Connecting the two areas ( sensory, motor ). In the CNS as interconnectors, establish neuronal circuit between sensory and motor neuron. Neuron Grouping The most important cell in the body is the neuron because it cannot be divided.. CORTEX: NUCLEI: Neuron form six layers on the cerebrum. Form three layers on the cerebellum. In subcortical region (thalamus, midbrain, brainstem and spinal cord) neuron form irregular cluster nuclei GANGLION: Cluster of neuron outside the CNS Synapses Sites of impulse transmission. Convert electrical signal into chemical signal Permit neurons to communicate. Types of synapses : Axodentritic synapse. Axosomatic synapse. Axoaxonic synapse. Dendrodentritic synapse Page 7

8 Page 8 Neuroglial Cells IT is like C.T for the neuron because it support them. Metabolic and mechanical supportfor neuron. 10 times abundant than neurons. but nervous is 10 larger ( in size). Neuroglial cells undergo mitosis. Function: provide neurons with structural support and maintain local conditions for

9 neuronal function. Staining: silver or gold impregnation, histochemical technique. Classification: Oligodendrocytes Astrocytes CNS Ependymal Cells Microglia * Schwan cells PNS Astrocytes: Pedicles binds to capillaries and to the pia mater form glial limitans. Controlling the ionic & chemical environment of neurons Energy metabolism Form cellular scar tissue Form the blood-brain barrier that cover capillary. Astrocyte is the most abundant مالحظت : اي وظ فت نم تم ذكرها ف انسال د تكىن نم Astrocyte: Protoplasmic astrocytes: ( short branches. ) Granular cytoplasm. Envelop the surface of nerve cells and blood vessels. Fibrous astrocytes: Long processes.(and small in number.) Predominantly in white matter. Page 9

10 Oligodendrocytes: Produce myelin sheath. (electrical insulation) in CNS. A single cell wrap several axons (40 to 50). Form nodes of Ranvier Differences with Schwann cell that the Schwann cell produce the myelin sheath in the peripheral but the oligodendrocytes produce it in the central has a lot of processes can mylinat multiple neuron at the same time but the Schwann cell mylinated one cell Page 10

11 Microglia: They are the only cells in the nervous system their origin is not nervous system not ectoderm ( it is mesoderm ). antigen presenting cell ( APC) in the nervous system. Phagocytic cells, scattered throughout the CNS. Derived from mesoderm. Small cell bodies. Their nuclei have elongated shape. Short processes with small expansions thorny appearance. Functions: Clearing debris, Act as APC, protect the CNS from viruses and microorganism. Ependymal Cells: Low columnar ciliated epithelial cells line the ventricles of the brain & central canal spinal cord. Formation of choroid flexus produce CSF. cilia. Facilitates the movement of CSF by CSF is very high felter plasma CSF is co-operation between epedymal cell & capillary It is NOT epithelial cell because it is like low columnar & cuboidal cell also it haven t basal lamina,connect with the under cell by processes Page 11

12 PNS. Schwann cells: Analogue to Oligodendrocyte. Produce myelin sheath in the Nerve it mean the axon & neuron it mean cell body which takes the stain so the nerve is multiple axon they covered with CT axon It make myline sheat for signal Nervous System is anatomically divided in to: Central nervous system (CNS). Peripheral nervous system (PNS). The CNS Consist of : Cerebrum Cerebellum Spinal cord No connective tissue soft, gel like When sectioned : White matter is the axon Gray matter is the cell body Covered by meninges covered the brain in 3 layer Page 12

13 Cerebrum Gray Matter: Contains neuronal cell bodies, dendrites and glial cells Six layers composed of neuron White Matter: Contains myelinated axons and myelin-producing oligodendrocytes Cortex is 6 layer of neuron because each layer give different order & function Cerebellum Originate motor movement Gray Matter: Three layers: Outer molecular layer Central layer of large Purkinje cells Inner granule layer White Matter: The same as cerebrum Page 13

14 Spinal Cord Gray Matter (central) shape of H inside Central canal lined by Ependymal cells Legs of the H form : Anterior horns Posterior horns Neurons : large and multipolar White Matter (peripheral) outside بامتحان انالب ما رح كىن ف تم ز ب ه اوىاع ال gili cell هتن بس انمطهىب انتم ز ب ىا و ب ه ال neurons الوه كث رة و صغ رة اما ال central canal is ependymal cell Page 14

15 The PNS Bundles of nerve fibers (axons) outside the CNS & surrounded by connective tissue. Main component: Peripheral nerves Ganglia Nerve endings The cell body is not in the PNS Nerve Fibers Consist of axons enveloped by a special sheath. Group of fibers constitute the peripheral nerve. Two types: Myelinated fiber Unmyelinated fiber The peripheral lining by CT not meninges Nerve made by multiple multiple hundred of axons enclosed by simple CT ال nerve من برا مغطى بال epineurium بعدين كل مجموعة axon مغطى ب perineurium و بعدين كل single axon مغطى ب endoneurium Page 15

16 Myelinated fibers: A single Schwann cell wraps around single axon form myelin sheath nodes of Ranvier. Unmyelinated fibers: A single Schwann cell envelopes several axon. Fibers enveloped within simple clefts of Schwann cells In CNS is totally unmyelinated but in PNS we have Schwann cell around nerve either rapping incompleat or the one Schwann cell has multiple axon that is not cover all one Page 16

17 Conduction Velocity Depend on the extent of Myelination: Unmyelinated fibers No nodes of Ranvier continuous conduction. Slower conduction Myelinated fibers: Gap of myelin sheath (nodes of Ranvier ) saltatory conduction. Faster conduction. Page 17

18 Connective Tissue Investments Epineureum: Dense collagenous Con. Tissue with thick elastic fiber Prevent damage by overstreching Perineureum : Dense con. Tissue Isolates neural environment (blood-nerve barrier) Endoneureum: Loose con. Tissue Regulation of microenvironment of nerve fiber Page 18

19 Peripheral Nerve (H&E) Ganglia Ovoid structure containing neuronal cell bodies, glial cells supported by connective tissue. Function : Relay stations to transmit impulses. Types: Sensory ganglia Autonomic ganglia ف االمؼاء نما ص ر ف ها وجغ ما بىقدر وحدد طب ؼت انىجغ و مكاوه الوه االػصاب ان ف ها involuntary مثم ال autonomic ػهى ػكس انجهد ان بتقدر تحدد ف ه وىع االنم Page 19

20 Sensory Ganglia (cell bodies of sensory neuron) Unipolar cell bodies enveloped by cuboidal capsule cells Cranial ganglia: Associated with the cranial nerve Spinal ganglia: Associated with the spinal nerve Autonomic Ganglia (cell bodies of postganglionic autonomic nerves) Multipolar neuron enveloped by satellite cells. Some are located within certain organ (intramural). Dorsal Root Ganglia Autonomic Nervous System Page 20

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