Nervous tissue neuron neurons-8520 Picture Here Functions of Nerve Tissue nreacts to stimuli from the internal and external environment and conducts impulses to organs, nanalyses and integrates stimuli to provide appropriate, co-ordinated responses organs, nconducts impulses from the sense organs and receptors to the central nervous system (CNS), ntransmits impulses from the CNS to the effectors (skeletal muscle, smooth muscles and glands). ann nNervous system central (CNS) n peripheral (PNS) n n motor (voluntary) n autonomic n nOrigin of NS: neuroectoderm n Pic14.jpg (102351 bytes) Nervous tissue structure nerve cells (neurons) + supporting cells (glia) Neuron nPerikaryon n(cell body) nDendrite(s) n nAxon hillock nAxon – only 1 n nTelodendria f14-3a_structures_in_a__c f14-3a_structures_in_a__c Receptive portion Transmission portion Secretory portion PARTS of NEURON Neuron 4 – 100 mm in Æ N Mi neurotubules, neurofilaments Nissl bodies = RER Dendrite(s) transport of nerve impulses Usual organelles in cytoplasm (GA, ER, Ri, Ly, … lipofuscin cnemnns nucleus nucleolus Nissl substance dendrite Triangular shape of perikaryon (pyramidal neuron from cerebral cortex) Shape of perikaryon (usually depends on the number of dendrites) Cajal's horizontal cells in brai cortex Purkinje cells in cerebellum Neurons of spinal ganglia Pyramidal cells in brain cortex Motor neurons in anterior horns of spinal column image008 3_09 ORG11 1 2 3 1, 2 – multipolar neurons: Nissl bodies 3 – pseudounipolar neurons:lipofuscin Classification of neurons (according to number of processes) n(Apolar) nUnipolar nBipolar nPseudounipolar nMultipolar n(Amacrine) n typyneuronu amakrinní kopie Classification of neurons (according to …) nthe length of axon: n Golgi type I (long axon) – length up to 1 m n Golgi type II (short axon) – length about several 1 cm nthe function: n sensitive neurons (aferent) – conduct impulses from n the receptors to CNS n motor neurons (eferent) – conduct impulses from CNS n to the efector cells n interneurons – are situated between sensitive and motor n neurons; represent 97 % of all neurons n Dendrites (from Greek dendron, “tree”) nare the branched projections of a neuron that act to conduct the electrical stimulation, ndendritic spines are small membranous protrusions electric intensity vector acts in perpendicular direction to dendrite axis. draft_9 spine Axon (neurit, nerve fibre) nis a long, slender projection of neuron, that conducts electrical impulses away from the perikaryon of neuron, naxon hillock, initial segment ncontains neurofilaments, neurotubules nits surface can be covered by sheath(s): Schwann sheath, myelin sheath, ntelodendria nerv1 Axon hillock Initial segment of axon Schwann cells Axonterminals (telodendrion) STRUCTURE of AXON Sheaths of axons (neurits) introd6 myelin2 Schwann cells (in PNS) Myeline sheath Oligodendrocytes (in CNS) Nerve sheaths - myelin sheath - Schwann sheath (in PNS) - oligodendrocytes (in CNS) Nervová tkáň - 16 Obaly nervových výběžků Nervová tkáň - 15 Nerv Myelin sheath Ø 1 - 20 µm thick Ø 70 % H2O, lipids, proteins Ø spirally arranged lipoprotein lamellae Ø by Ranvier nodes is separated into internodia (Ranvier segments, 0,6–2,0 mm long) 004 Myelinani Image_000447_upr kopie Picture3 arrobend arrobend arrobend arrobend Nodes of Ranvier Nervová tkáň - 12 Nervové vlákno w-peripheralnerve-7 arrobend Nervová tkáň - 17 Nervové vlákno nemyelinizované Neurilemma = composed of Schwann cells Ø fibers without myelin sheath - Schwann cell surrounds more axons Ø myelinized fibers - each internodium has its own Schwann cell myelin2 Synapses nserve for transmission of impulses between neurons or neuron and effector cell, nchemical or electric synapses, nthree parts of synapse: 1) presynaptic knob 2) synaptic cleft 3) postsynaptic membrane synapse synapticcleft Function of synapse synapse synani1 Synaptic vesicles Synaptic cleft 20 – 30 nm 07a80e00 Short chains of peptides practice Interneuronal synapses neuron – neuron neuron Axodendritic Axosomatic Dendrodendritic axoaxonal Peripheral synapses neuron – effector cell I10-40-nerve neuromuscular_junction_copy1192590849 nmjunct3 Motor end plate Neuroglia (glial cells) nSupporting cells in nerve tissue nFunctions: supportive, nutritive, (immuno)protective nCentral glia: astrocytes fibrous n protoplasmic n oligodendroglia n microglia (Horteg) n ependyma nPeripheral glia: Schwann cells n satellite cells practice Neuroglia Central glia § astrocytes – hematoencephalic barrier § § oligodendrocytes – myelin § § mikroglia – phagocytosis § § ependymocytes – lining of CNS cavities + liquor production Periferal glia § Schwann cells (neurilemma) – myelin § satelite cells – isolation of perikarya in ganglia f14-6_cellular_organiza_c CENTRAL GLIA Nervový systém - 4 Mozková kůra Cortex cerebri (HE) – lamina pyramidalis Nervový systém - 5 Velké pyramidové bb Cortex cerebri (HE) – lamina ganglionaris with large pyramidal cells of Betz s1440x Nervový systém - 3 Mozková kůra Cortex cerebri (HE) – pyramidal cell purkinje_small cerebellum_40x_PC231474 Cerebellum (impregnation) – Purkinje cell s1740xgm Nervový systém - 15 Mícha Medulla spinalis (HE) – motor neuron Nervový systém - 22 Ganglion spinale Spinal ganglion (HE) nerve nerve epineurium pseudounipolar neurons bundles of nerve fibers s17100xdrg s1720xdrg Ganglion cell + satellite cells NL%20NERVE%20S97-36327%20HE%205X epineurium perineurium bundles of nerve fibers blood vessels adipose tissue Peripheral nerve (HE) – cross section neurolemmocytes neuro-vandyperipheralnerve-rev nervefibercross Peripheral nerve (HE) cross section Axon myelin sheath Schwann cell nucleus Nervový systém - 35 Periferní nerv w-peripheralnerve-7 Peripheral nerve (HE) longitudinal section Myelinated nerve fiber (axon) hl3-15 brain Thank you for your attention Astrocytes (macroglia) nProtoplasmic astrocytes Fibrous astrocytes n n n n n n n n n n nFunctions: cytoplasmic processes are ended by end feet, which form continuous layer – limiting membranes on the surface of: 1) blood capillaries (membrana limitans gliae perivascularis; together with endothelium it forms blood-brain barrier, n 2) brain (membrana limitans gliae suoerficialis) Astrocytes have protective and nutritive function n 35 35 In gray matter of CNS In white matter of CNS Astrocyte bbb Astrocyte END FOOT End feet taking nutrients From blood End feet bringing nutrients to dendrites and bodies of neurons End feet bringing nutrients to telodendrion of neuron Astrocyte cneafp2 astros-1 Astrocytes brain introd4 arrobend arrobend Membrana limitans gliae superficialis epen100he EllenG1 introd6 f2_06 Myelinani PERIPHERAL GLIA: SCHWANN CELLS wobbly1 wobbly2 getimage F8-3B w-peripheralnerve-7 ner402he mucosalelecmic Myelin3 fnode1 drg40he gan41he 07b80e00 neuronecomplex n oligo image n neuron2 Picture3 A damaged nerve signal Nervous tissue structure n nerve cells (neurons) + supporting cells (glia) glial arrobend NMJ1 MOTOR%20END%20PLATES%20SMALL%201 Axon terminals Muscle spindle Motor end plates Muscle fibers Group of motor end plates each skeletal muscle fiber—no matter how long it may be—has only one such neuromuscular junction these muscle fibers will contract simultaneously myoneuraljunction Nervová tkáň - 8 Axony příčně n synapse n Nervou2 brain_manSmall f14-13a-b_synapses_c myelin2 introd6 n neuron myelin fiber copy.JPG (29694 bytes) cs of nerve copy.JPG (43557 bytes) Node of Ranvier copy.JPG (30994 bytes) Osmium cs nerve copy.JPG (42042 bytes) Fig. 1 (a) A myelinated axon in the peripheral nervous system and (b) its development. Each Schwann cell myelinates a single axon, to which it is directly apposed. During development (anticlockwise) Schwann cells loosely ensheath axons and the myelin sheath grows around the axon to form concentric layers, which become tightly apposed spinal ganglia (nerve fibe copy.JPG (40205 bytes) spinal ganglia (lipofuscin copy.JPG (32170 bytes) perineurium 2 copy.JPG (44684 bytes) w-peripheralnerve-7 cnepche cnepcp2