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Nervous Tissue

Nervous Tissue. Chapter 9. Structures of Nervous System. Brain- Neurons enclosed in skull Spinal cord – connects to brain & enclosed in spinal cavity Nerves- bundles of neuronal axons Cranial emerge from brain; spinal nerves- emerge from spinal cord

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Nervous Tissue

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  1. Nervous Tissue Chapter 9

  2. Structures of Nervous System • Brain- Neurons enclosed in skull • Spinal cord– connects to brain & enclosed in spinal cavity • Nerves- bundles of neuronal axons • Cranial emerge from brain; spinal nerves- emerge from spinal • cord • Ganglia- groups of cell bodies outside brain & spinal cord • Enteric plexuses- networks in digestive tract • Sensory receptors- monitor changes in internal or external environments

  3. Figure 9.1

  4. Function • Sensory Receptors & afferent nerves • Carry information into brain & spinal cord • Integration- information processing • Perception = awareness of sensory input • Carry by short interneurons • Motor activity- efferent nerves • Signals to glands and muscles (effectors)

  5. Organization • Central Nervous System (CNS) • Peripheral Nervous System (PNS) • Subdivided: Somatic (SNS) & Autonomic (ANS) nervous systems • Also • INPUT-Afferent or Sensory division • OUTPUT- Efferent or Motor division

  6. Figure 9.2

  7. Nervous System • Neuron= nerve cell • Specialized for signal carrying & information processing • Neuroglia cells-support, nourish & protect neurons • Neuroglia critical for homeostasis of interstitial fluid around neurons

  8. Neuronal Structure • Cell body- nucleus, cytoplasm with typical organelles • Dendrites- highly branched input structures emerging from cell body • Axon- conducts away from cell body toward another neuron or effector • Axon terminals -at end of axon with synaptic bulbs

  9. Figure 9.3

  10. Myelination • Axons covered with a myelin sheath • Many layered lipid & protein creating insulations • Increases speed of nerve conduction. • Nodes of Ravier= gaps in the myelin • Some diseases destroy myelin- E.g. multiple sclerosis & Tay-Sachs

  11. Gray and White Matter • White matter- primarily myelinated axons • Gray matter- cell bodies, dendrites, unmyelinated axons, axon terminals & neuroglia • Spinal cord gray matter is centrally located • Gray matter in brain covers surface of cerebrum & cerebellum – cortex

  12. Neuroglia • Make-up ~ half the volume of CNS • Cells smaller than neurons • Can multiply and divide and fill in brain areas • Do not conduct nerve impulses

  13. Neuroglia-support • Astrocytes- blood brain barrier • Oligodendrocytes- myelin in CNS • microglia - defense • Ependymal cells- CSF production • Schwann- PNS cell support • Satellite cells- in PNS ganglia

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