Human Biology/Tissues Nervous Tissue Nervous Tissue: General description: ---Components: nerve cell: neuron Glial cell: neuroglial ---Function: Neurons : receive the stimulation, conduct the nerve impulse. Glial cell: support, protect and insulate, nourish neurons. Neuron: The structural and functional cellular unit. Shape of Neuron: consists of cell body, dendrite and axon. ---cell body(perikaryon or soma): spherical, pyramidal fusiform or stellate in shape. ---dendrite: like branches of tree. ---axon: long thin cord-liked. ( 1 ) Human Biology/Tissues Nervous Tissue Structure of Neuron 1. Cell body: ---cell membrane: unit membrane-irritability, receive stimuli, initiate and conduct nerve impulse membrane proteins-ions channel and receptor ---cell nucleus: large and round, centrally- located, pale stained, with a large, clear nucleolus. ---cytoplasm: perikaryon a. Nissl body: basophilic spot-liked or granule-liked structure, parallelly-arranged rough endoplasmic reticulum and free ribosome. function: synthesis of proteins structural protein enzymes related to the production of neurotransmitters ( 2 ) Human Biology/Tissues Nervous Tissue b. Neurofibril: LM: there are many thread-liked dark brown color structure to form a network. EM: neurofilament microtubule function: supporting involving in intracellular transportation c. other organelle Golgi apparatus mitochondria pigment 2. Dendrite: ---many, short and more branches. ---structure: similar to cell body. ---function: receive the information. 3. Axon: ---thin, less branch. ---structure: no Nissl body, but have microtubule, neurofilament, microfilament, mitochondria, smooth endoplasmic reticulum and vesicle. ( 3 ) Human Biology/Tissues Nervous Tissue axon hillock: the beginning part of axon. axolemma axoplasm ---function: initiate an impulse and conduct the impulse. Classification of Neuron: ---According to number of processes multipolar neuron bipolar neuron pseudounipolar neuron ---According to length of axon Golgi type I neuron: long axon and large. Golgi type II neuron: short axon. ---According to function sensory neuron motor neuron interneuron ---According to the neurotransmitter or neuromodulator release by the neuron cholinergic neuron aminergic neuron peptidergic neuron aminoacidergic neuron Synapse: ---definition: is the junctions between neurons or neuron and non-nerve cells. ---classification: • chemical synapse: taking neurotransmitter as communicating medium. • electrical synapse: gap junction. Types of Synapse: a) axo-dendritic synapse between axon and dendrites. b) axo-somatic synapse between axon and soma. c) axo-axonic synapse between axon and axon. d) dendro-dendritic synapse between dendrites and dendrites The axon ending shows two mitochondria as well as synaptic vesicles that contain neurotransmitters. Liberation of the mediated substance transmit the nerve impulse from pre-synaptic (neuron A in the figure) to the post-synaptic (neuron B) membrane. ( 4 ) Human Biology/Tissues Nervous Tissue Glial cell(neuroglia) 1) Glial cell in central nervous system(CNS) a. Astrocyte: /large stellate. /round or ovoid nucleus, large and pale stained. /end feet: to form glia limitans or vascular feet-constitute blood brain barrier. /classification: fibrous astrocytes: have long, thin and smooth processes. ( 5 ) Human Biology/Tissues Nervous Tissue protoplasmic astrocyte: short, thick processes with more branch. /function: supporting, insulating and repairing. regulate the environment and movement of neuron. b. Oligodendrocyte: ---structure: smaller, fewer process with a small round and dark stained ---function: their processes form myelin-sheath of nerve fiber in CNS. ( 6 ) Human Biology/Tissues Nervous Tissue c. Microglia: ---structure: smallest, elongate shape or ovoid, with a small dark irregular stain. ---function: phagocytosis-mononuclear phagocyte system. d. Ependymal cell: ---structure: simple cuboidal or columnar epithelium. Apical surface: microvilli and cilia. Basal surface: long processes. ---function: produce cerebrospinal fluid. nerve stem cell. ---distribution: ventricle of brain and central canal of spinal cord. 2) glial cell in peripheral nervous system(PNS) a. Schwann cell: /envelop the axon end to end to form myelin-sheath in PNS. b. Satellite cell (capsular cell): /one layer of flattened or cuboidal cell, with round, ovoid and dark stain. /surrounding the neuron in ganglion. Nerve fiber and Nerve ---definition: a structure formed by axon which enveloped or covered by special sheath can conduct the impulse to certain direction. ---classification: according to myelin-sheath myelinated nerve fiber unmyelinated nerve fiber ( 7 ) Human Biology/Tissues Nervous Tissue Nerve: ---Nerve fiber gets together to form nerve. efferent nerve afferent nerve mixed nerve ---structure: epineurium: dense connective tissue. perineurium: dense connective tissue. endoneurium: thin layer of loose connective tissue. Ganglia : composed of cell body outside the CNS, it also contain glial cells in capsulated by dense connective tissue such as craniospinal and autonomic ganglion. Nerve Ending: 1) Sensory nerve ending ①free nerve ending ② Encapsulated nerve ending :have connective tissue capsule a. tactile corpuscle ex. dermis b. lamellar corpuscle ex. ligaments c. Muscular spindles ex. Skeletal muscle 2)Motor nerve ending: muscular Tissue and gland a. Somatic MNE: motor end plate, neuromuscular junction * motor unit: axon of one neuron and all skeletal muscle fiber controlled by it b.Visceral MNE ---distribution: smooth M, Cardiac M and gland. Meninges:- They are membranes of connective tissue encased the central nervous system (brain and spinal cord). a. Duramater: outer layer b. arachnoid middle : is a thin membrane and devoid of blood vessels. c. piamater inner : is a thin loose connective tissue and contain a large number of blood vessels. ( 8 ) .