9 unit 1 chapter 9. 9 unit 1 brain- neurons enclosed in skull spinal cord connects to brain ...
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Figure 9.1TRANSCRIPT
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Nervous Tissue
Chapter 9
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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
Figure 9.1
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Function
• Sensory Receptors & afferent nervesCarry information into brain & spinal cord
• Integration- information processingPerception = awareness of sensory input Carry by short interneurons
• Motor activity- efferent nervesSignals to glands and muscles (effectors)
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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
Figure 9.2
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Nervous System
• Neuron= nerve cell Specialized for signal carrying & information
processing• Neuroglia cells-support, nourish &
protect neuronsNeuroglia critical for homeostasis of
interstitial fluid around neurons
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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
Figure 9.3
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Myelination
• Axons covered with a myelin sheath Many layered lipid & protein creating
insulationsIncreases speed of nerve conduction.
• Nodes of Ravier= gaps in the myelin
• Some diseases destroy myelin- E.g. multiple sclerosis & Tay-Sachs
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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
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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
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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