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Nervous System Cells

Nervous System Cells. Neurons = functional cellular unit of nervous system; action potentials Neuroglial cells = support, nourish, or protect neurons Oligodendroglial & Schwann cells = insulate neurons with myelin (Gnathostomes)

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Nervous System Cells

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  1. Nervous System Cells • Neurons = functional cellular unit of nervous system; action potentials • Neuroglial cells = support, nourish, or protect neurons Oligodendroglial & Schwanncells = insulate neurons with myelin (Gnathostomes) Astrocytes = transport nutrients (& signal neurons at synapse); CNS only Microglia = engulf bacteria; CNS only Ependymal cells = cilliated cells that line central canal & ventricles; CNS only

  2. Neural Tissue

  3. Motor Neuron cell body node of Ranvier axon myelin under a Schwann cell axon hillock synaptic terminal dendrite

  4. Neuron Function • Signal propagates down an axon as ion channels open along the axon (changing voltage) – electrical signal • At the end of the axon vessicles containing neurotransmitter release– chemical signal

  5. Schwann Cells & Oligodendroglia

  6. Subphylum Vertebrata Actinopterygii Chondrichthys coelacanths amphibians lungfishes Mammalia hagfishes lampreys Reptilia myelin (Schwann cells & oligodendrocytes) brain

  7. Nervous System Development • Three ectodermal sources. • Neural tube – becomes C.N.S., optic “nerve,” retina, and pre-ganglionicmotor nerves. CNS derived only from neural tube. • Neural crest – becomes post-ganglionic nerves and peripheral glia. • Neurogenic placodes – become post-ganglionic cranial nerve (V, VII, IX, X) AND olfactory, vestibular, and lateralis sensory receptor cells.

  8. somite notochord inter- mediate meso- derm coelom lateral plate mesoderm Vertebrate Neurula (section) gut

  9. neural crest cells sclerotome dermatome myotome splanchnic mesoderm coelom somatic mesoderm Vertebrate Embryo (section) gut

  10. neural crest cells sclerotome dermatome myotome coelom Vertebrate Embryo (section) gut

  11. neural crest cells vertebra dermatome myotome coelom Vertebrate Embryo (section) gut

  12. will form dorsal root ganglion vertebra dermatome myotome will form other ganglia developing skin coelom Vertebrate Embryo (section) gut

  13. Neurogenic Placodes(post-ganglionic cranial nerves V, VII, IX, & X)

  14. Brain Development • Neurons migrate from the ependymal layer more superficially; 1st migrate least. • The anterior neural tube forms: -Prosencephalon (Forebrain) -Mesencephalon (Midbrain) -Rhombencephalon (Hindbrain) rhombomeres = segmental divisions

  15. Brain Developmental Regions • Prosencephalon = FOREBRAIN Telencephalon cerebrum & olfactory lobes Diencephalon thalamus, hypothalamus • Mesencephalon = MIDBRAIN  optic lobes / superior colliculi & tegmentum • Rhombencephalon = HINDBRAIN Metencephalon cerebellum & pons Myelencephalon medulla oblongata

  16. Spinal Nerves Development sensory inter- motor notochord

  17. Amniote Embryo (section)

  18. Nervous System Overview • Central Nervous System (CNS)= brain and spinal cord; myelin from oligodendroglia (astrocytes in synapse) Tract= region of axons; Nucleus or Cortex = region of cell bodies • Peripheral Nervous System (PNS)= nerves and ganglia; myelin from Schwann cells (also can cover synapse) Nerve = bundle of axons Ganglion = bundle of cell bodies

  19. PNS Overview • Cranial Nerves = attached to brain; many have ganglia; numbered with Roman numerals from anterior to posterior • Spinal Nerves = attached to spinal cord; most have ganglia; distinctly segmental dorsal root ventral root

  20. Peripheral Nervous System • Sensory (Afferent) = brings info. to CNS • Motor (Efferent) = takes info. from CNS • Visceral = innervates smooth muscle or organs in the coelom • Somatic = innervates skel. muscle and skin • Pre-ganglionic = cell bodies in the CNS; between CNS & a ganglion • Post-ganglionic Nerves = cell bodies in a ganglion; between a ganglion & another ganglion or a non-neural tissue

  21. Nervous System Overview

  22. Spinal nerves • Spinal Nerves = segmental from spinal cord • Dorsal Root = afferent (sensory) nerve • Dorsal Root Ganglion = afferent (sensory) neuron cell bodies • Ventral Root = efferent (motor) nerve • Sypathetic chain = chain of ganglia ventral to spinal cord

  23. Human Spinal Nerves • Cervical Plexus(C1-C5) also innervates diaphragm (Phrenic nerves) • Brachial Plexus (C5-T1) innervates arm • Intercostal / Thoracic Nerves (T2-T12) • Lumbar Plexus (T12-L5) • Sacral Plexus (L5-Co2) also innervates legs (Sciatic nerves)

  24. Human Thoracic Spinal Nerve

  25. dorsal root ganglion dorsal root spinal nerve ventral root sypathetic ganglion Human Thoracic Spinal Nerves

  26. Human Thoracic Spinal NervesSensory Neurons

  27. Human Thoracic Spinal NervesMotor Neurons

  28. Shingles Herpes/chicken pox virus dormant in spinal or cranial nerve

  29. Cranial Nerves • 10-13 nerves arising from the brain; numbered anterior to posterior. • 0 - nervus terminalis sensory for blood vessels of olfactory epithelium • I - olfactory “nerve” (ethmoid foramina) sensory fibers that innervate the olfactory epithelium • II - optic nerve (optic canal) sensory “nerve;”innervates retina not a true nerve; an extension of brain

  30. Cranial Nerves • III - oculomotor nerve (superior orbital fiss.) motor nerve for 4 of the 6 extrinsic eye muscles • IV - trochlear nerve (superior orbital fissure) motor nerve for 1 of the 6 extrinsic eye muscles • V - trigeminal nerve (3 branches)(foramina ovale and spinosum & superior orbital fissure) sensory for skin of head; motor for 1st arch muscles (mandibular branch) Trigeminal/Gasserion Ganglion • VI - abducens nerve (superior orbital fissure) motor nerve for 1 of the 6 extrinsic eye muscles

  31. Cranial Nerves • VII - facial nerve (3 branches)(stylomastoid foramen) - Facial/Geniculate Ganglion sensory for taste buds and head lateralis system; motor for 2nd arch muscles (hyomandibular branch) • VIII - auditory nerve (Vestibulocochlear) sensory for inner ear/vestibule (internal aud. meatus) • IX - glossopharyngeal nerve (jugular for.) sensory for taste and pharynx; motor for 3rd arch muscles (1st branchial arch branch) – Superior & Inferior Glossopharyngeal Ganglia • IX - vagus nerve (jugular foramen) sensory and motor for mouth, pharynx, outer ear, and most viscera – Superior & Inferior Vagus Ganglia

  32. Posterior-Most Cranial Nerves • XI - spinal accessory nerve (amniotes only) (foramen magnum) sensory & motor for branchiomeric muscles (e.g., trapezius, sternomastoid) = branch of vagus in non-amniotes • XII - hypoglossal nerve (amniotes only) (hypoglossal canal) motor & sensory for tongue muscles = occipital nerves in non-amniotes

  33. somitomeres 1-7 somites 1-4 mandibular arch hyoid arch 1st branchial arch Shark-like Vertebrate

  34. terminal 0 mandibular arch hyoid arch 1st branchial arch Special Sensory Cranial Nerves optic II auditory VIII olfactory I

  35. X XII IV V VI VII IX III mandibular arch hyoid arch 1st branchial arch Segmental Cranial Nerves XI

  36. X XII IV V VI VII IX III mandibular arch hyoid arch 1st branchial arch Segmental Cranial Nerves XI II VIII I 0

  37. X XII VII IV VI V IX III XI II 0 I VIII Suprabranchial Placodes • Form ganglia for the trigeminal, facial, glossopharyngeal, & vagus cranial nerves.

  38. CNS • Spinal Cord = CNS dorsal to notochord and posterior to head • Central canal = canal within spinal cord • Brain = enlarged anterior CNS • Ventricles = cavities in brain • Cerebrospinal fluid (CSF) = fills ventricles & central canal • Choroid plexus = tuft of capillaries that secrete CSF

  39. Meninges • Meninges = layers of connective tissue surrounding CNS Non-tetrapods = 1 (primitive meninx) Non-mammal tetrapods = 2 (dura matter + secondary meninx) Mammals = 3 • Dura matter = outermost • Arachnoid = middle • Pia matter = innermost

  40. CNS • Gray matter = many cell bodies; >integration • White matter = few cell bodies; many axons with myelin(in Gnathostomes); >transport • Gray matter ancestrally deep; white matter superficial, EXCEPTsuperficial in forebrain in amniotes, teleosts, hagfishes, and a few chondrichthyans

  41. Spinal Cord cauda equina

  42. Brain Regions • Prosencephalon = FOREBRAIN Telencephalon cerebrum & olfactory lobes Diencephalon thalamus, hypothalamus, epiphysis, hypophysis, optic nerves • Mesencephalon = MIDBRAIN; tectum  superior colliculi & inferior colliculus tegmentum • Rhombencephalon = HINDBRAIN Metencephalon cerebellum & pons Myelencephalon medulla oblongata

  43. Brain Regions

  44. Teleost Brain Regions Pros- Mes- Rhomb-

  45. Bird Brain Regions Pros- Mes- Rhomb-

  46. Telencephalon • Olfactory lobes • Cerebrum, large in mammals & birds, lateral ventricles. • In mammals, dorsal pallium forms the 6 layered neocortex. • gyri = folds of neocortex • sulci = grooves of neocortex • Actinopterygiians = gray matter everts; single medial ventricle • All other vertebrates = gray matter inverts; 2 lateral ventricles

  47. Diencephalon • Thalamus, Hypothalamus, & Median Ventricle (3rd). • Optic nerves cross and enter brain at optic chiasma (neurons pass through the diencephalon, synapse in the mesencephalon). • Dorsal epiphysis (pineal & parietal organ) & Ventral hypophysis (pituitary).

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