Chapter 8 2 the nervous system
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Chapter 8.2: The Nervous System. Neuroglia. Astrocytes Largest and most numerous Maintain blood-brain barrier Isolates CNS from circulation Capillaries impermeable Repair damaged neural tissue. Figure 8.4. Neuroglia cont…. Oligodendrocytes Coats axons with myelin Nodes of Ranvier

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Neuroglia
Neuroglia

  • Astrocytes

  • Largest and most numerous

  • Maintain blood-brain barrier

  • Isolates CNS from circulation

  • Capillaries impermeable

  • Repair damaged neural tissue



Neuroglia cont
Neuroglia cont…

  • Oligodendrocytes

  • Coats axons with myelin

  • Nodes of Ranvier

  • Parts of axon with no myelin

  • Internodes

  • Parts of axon with myelin

  • Myelin increases speed of action potential



Neuroglia cont1
Neuroglia cont…

  • Microglia

  • Engulf wastes and pathogens



Neuroglia cont2
Neuroglia cont…

  • Ependymal Cells

  • Produces cerebrospinal fluid



Neuroglia cont3
Neuroglia cont…

  • Satellite Cells

  • Support cell bodies

  • Schwann Cells

  • Covers axons—called neurilemma



Demyelination disorders
Demyelination Disorders

  • Demyelination

  • Progressive destruction of myelin

  • Inflammation

  • Axon Damage

  • Scarring of neural tissue

  • Gradual loss of sensation and motor control

  • Numbness and paralysis


Disorders cont
Disorders cont…

  • Multiple Sclerosis (MS)

  • Optic nerve, brain and spinal cord affected

  • Partial loss of vision

  • Problems with speech, balance and motor coordination


Neuron anatomy
Neuron Anatomy

  • Neuron cell bodies—gray matter

  • Located in ganglia of PNS

  • White matter—bundles of axons

  • Called nerves



Membrane potential
Membrane Potential

  • Polarized—resting cell membrane

  • Resting Potential—membrane potential of resting neuron

  • -70mV

  • More negative ions inside than out of neuron



Potential cont
Potential cont…

  • Depolarization

  • Shift membrane potential towards positive

  • Ex: 0 mV



Potential cont1
Potential Cont…

  • Hyperpolarization

  • Shift membrane potential towards more negative

  • Ex: - 80 mV



Potential cont2
Potential cont…

  • Action Potential

  • Triggered by depolarization

  • Membrane potential must reach threshold

  • -60 mV



Potential cont3
Potential cont…

  • Repolarization

  • Return to resting potential



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