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Nervous tissue
Nervous tissue forms the organs of the nervous system such as the brain, spinal cord, and nerves. It is cellular tissue composed of neurons and glial cells. Nervous tissue lacks extracellular material. Neurons generate, conduct, and transmit nerve impulses and process information, while glial cells perform supporting functions. Neurons consist of a cell body and processes, with cell bodies forming gray matter and processes forming white matter. Neurons are polarized and use synapses to transmit nerve impulses chemically or electrically between each other. Glial cells such as oligodendrocytes and astrocytes insulate and support neurons. Myelinated nerve fibers contain axons surrounded by myelin sheaths
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Nervous tissue
- 1. Nervous Tissue Lecturer –professor Boronikhina Tatiana Vladimirovna
- 2. Nervous tissue formsorgans of the nervous system nerve ganglion ⇓ brain
- 3. Nervous tissue iscellular tissue consists of cells neurons glial cells lacks extracellular material
- 4. All nervous tissuecells have processes
- 5. Nervous tissue cellfunctions Neurons 1. generation, conduction, and transmission of nerve impulses 2. accumulation, processing, and reproduction of information Glial cells attending functions
- 6. Nervous tissue embryonicorigins Neural tube ⇒ neurons and glial cells of CNC Neural crest ⇒ neurons and glial cells of PNS Mesenchyme ⇒ microglial cells of CNS
- 7. Neuron consists ofa cell body and processes Neuron cell bodies form ganglia of PNS gray matter of CNS Neuron processes form nerves of PNS white matter of CNS
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- 9. Neuron cytology Nucleus islarge and euchromatic with well-developed nucleoli Cytoplasm is rich in organelles rER mitochondria Golgi apparatus microtubules and filaments sER lysosomes
- 10. Neuron cell body(soma, perikaryon)
- 11. Neurons are obligatoryaerobic cells contain numerous mitochondria use O2 - 25% in adults 50% in children blood glucose is a substratum of respiration
- 12. Time of revivificationin clinical death is limited 5 – 6 minutes 15 – 16 minutes in hypothermia or pharmacologic defence
- 13. Basophilic clumps orNissl bodies rER Nissl bodies
- 14. Neuron rER synthesizesmembrane proteins proteins are necessary for synaptic vesicle formation neuron growth and differentiation intracellular regeneration
- 15. Golgi apparatus takespart in synaptic vesicle formation Golgi apparatus in neuron cell bodies synaptic vesicles
- 16. “Neurofibrils” are aggregatedmicrotubules and filaments Silver impregnation ⇑ electron micrograph of axon cytoplasm
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- 18. Dendrites are numerous orsingle branch dichotomically directly from the soma (arborization) contain all organelles possess spines to increase the synaptic surface ⇒ may form receptors
- 19. Axon is always asingle branches forming collaterals and at the terminal lacks rER and ribosomes contains many microtubules and filaments lacks spines may form effectors
- 20. Axonal transport Transport direction: anterograde – away from the neuron soma retrograde – towards the neuron soma Transport velocity: fast (200-400mm/day) synaptic vesicles slow (0,2-1mm/day) tubulin, actin intermediate (2-50mm/day) enzymes
- 21. Neuron dynamic polarization Dendritesconduct nerve impulses ⇓ towards the soma Axon conducts nerve impulses ⇓ away from the soma neurons are polarized by synapses
- 22. Synapses are specialized neuronjunctions to transmit nerve impulses
- 23. Synapse classifications Depending ontransmission mechanism: • chemical • electrical (nexuses) Depending on physiologic effect: • excitatory • inhibitory
- 24. Morphologic synapse classification Synapsesare a neuron axon terminations on the soma, dendrites, and the axon of another neurons a - axosomatic b - axodendritic c - axoaxonic
- 25. Chemical synapse parts Presynapse– axon ending (presynaptic knob) synaptic vesicles with neurotransmitters mitochondria presynaptic membrane Postsynapse – soma, dendrite, or axon postsynaptic membrane receptors to neurotransmitters Synaptic cleft filaments enzymes for neurotransmitter inactivation
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- 27. Parasynapse is fromglial cells functions synaptic cleft isolation neurotransmitter utilization
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- 29. Neurotransmitter-receptor interaction opensionic channels Exitatory synapse Na+ channels open ⇓ membrane depolarization ⇒ Inhibitory synapse Cl- channels open ⇓ membrane hyperpolarization
- 30. Neurotransmitter utilization return topresynapse by endocytosis destruction in synaptic cleft by enzymes absorption by parasynapse
- 31. Peripheral nerve endings Sensorynerve endings – receptors are terminals of the sensory neuron dendrites Function: interact with stimuli and generate nerve impulses Motor nerve endings - effectors are terminals of the motor neuron axons on muscles or glands Function: stimulate muscle contraction or gland secretion
- 32. Histologic receptor classification Free dendriteterminals Non-free dendrite terminals glial cells Encapsulated dendrite terminals glial cells connective tissue
- 33. Encapsulated receptor inthe skin dermis mechanoreceptor Pacinian corpuscle
- 34. Effectors are neuromuscularor neuroglandular synapses ⇐ on smooth muscle cells on skeletal muscle fiber ⇒
- 35. Motor end plate Presynapse– motorneuron axon Postsynapse – sarcolemma Neurotransmitter – acetylcholine Cleft enzyme - acetylcholinesterase Parasynapse - lemmocytes
- 36. Functional neuron classification Sensoryneurons pseudounipolar bipolar multipolar (rarely) Motor neurons multipolar Associative neurons multipolar or bipolar
- 37. Neuron capacity forregeneration Physiologic regeneration intracellular level (static population) Reparative regeneration soma damage ⇒ cell death process damage ⇒ processes are repaired
- 38. Nervous stem cells bediscovered in the brain ⇒
- 39. Glial cell classification Macroglialcells arise from neuroectoderm oligodendrocytes astrocytes ependymal cells Microglial cells arise from mesenchyme are blood monocyte derivatives are macrophages of the CNS belong to the mononuclear phagocytic system ⇐
- 40. Glial cell commonfeatures possess processes are capable of migration (except for ependymal cells) can proliferate are capable of phagocytosis (except for ependymal cells) perform attending functions for neurons
- 41. Oligodendrocytes are found inthe CNS and PNS possess a few short processes contain numerous organelles enclose the neuron cell bodies and processes live symbiotically with neurons Functions: neuron insulation and protection neuron nutrition nerve fiber formation nerve fiber regeneration ⇐ ⇒
- 42. Astrocytes are found onlyin the CNS: protoplasmic astrocytes ⇒ in the gray matter fibrous astrocytes ⇒ in the white matter contain numerous microfilaments and microtubules their processes sheathe blood vessels form glial membrane beneath the pia mater Functions: • neuron support • neuron isolation • nutrient transport • electrolyte balance maintenance • repair (scar formation)
- 43. Ependymal cells are foundin the CNS: line the spinal canal and brain ventricles form epithelium-like layer are cylindrical or cuboidal in shape apical cell pole possesses cilia basal cell pole form process Functions: • production of cerebrospinal fluid (CSF) • exchange between CSF and nervous tissue • neuron support ⇒
- 44. Ependymal cells linethe spinal canal
- 45. Nerve fibers areneuron processes enveloped by oligodendrocyte sheaths Unmyelinated nerve fibers contain dendrites (except for ANS motor neuron axon) untreated fibers are grey in colour are slow - nerve impulse conduction velocity is 8-10 m/sec Myelinated nerve fibers contain axons (except for sensory neuron dendrites) untreated fibers are white in colour are fast - nerve impulse conduction velocity is 80-120 m/sec Function of sheaths – electric insulation of neuron process
- 46. Unmyelinated nerve fibers containsseveral (15-20) axis cylinders or neuron processes the so-called “cable-type fibers” axis cylinders are enclosed by cytoplasm and plasmalemma of oligodendrocytes (lemmocytes or Schwann cells in the PNS)
- 47. Myelinated nerve fibers containthe only axis cylinder axis cylinder is enclosed by the myelinated sheath (myelin) and neurilemma (cytoplasm, nucleus, and plasmalemma of lemmocyte)
- 48. Myelinated sheath (myelin) consistsof oligodendrocyte plasmalemma (mesaxon) several layers has lipoprotein organization with lipid predominance
- 49. Myelinated sheath structures Nodeof Ranvier sites between adjacent lemmocytes lacked myelin Schmidt-Lanterman clefts (only in PNS) sites where the Schwann cell cytoplasm is preserved to function like nutritious canals
- 50. Myelinated fiber lightand scanning appearance • nodes of Ranvier provide saltatory impulse conduction
- 51. PNS nerve fibersare enclosed by endoneurium Includes basal lamina collagen fibers Is produced by lemmocytes
- 52. Myelinated fiber formationin the CNS an oligodendrocyte produces myelin of several axis cylinders ⇔
- 53. Myelinated fibers inthe CNS neurilemma is minimal myelin lacks Schmidt-Lanterman clefts nodes of Ranvier are bare
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- 56. Thank you forattention!