chapter 8.2: the nervous system. neuroglia astrocytes largest and most numerous maintain...
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Chapter 8.2: The Nervous System
Neuroglia
AstrocytesLargest and most numerousMaintain blood-brain barrier Isolates CNS from circulationCapillaries impermeableRepair damaged neural tissue
Figure 8.4
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
Figure 8.5
Neuroglia cont… Microglia Engulf wastes and pathogens
Figure 8.4
Neuroglia cont… Ependymal Cells Produces cerebrospinal fluid
Figure 8.4
Neuroglia cont… Satellite Cells Support cell bodies Schwann Cells Covers axons—called neurilemma
Figure 8.5b
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… Multiple Sclerosis (MS) Optic nerve, brain and spinal cord
affected Partial loss of vision Problems with speech, balance and
motor coordination
Neuron Anatomy Neuron cell bodies—gray matter Located in ganglia of PNS White matter—bundles of axons Called nerves
Figure 8.6
Membrane Potential Polarized—resting cell membrane Resting Potential—membrane
potential of resting neuron -70mV More negative ions inside than out of
neuron
Figure 8.8 5
Potential cont… Depolarization Shift membrane potential towards
positive Ex: 0 mV
Figure 8.8 5
Potential Cont… Hyperpolarization Shift membrane potential towards
more negative Ex: - 80 mV
Figure 8.8 5
Potential cont… Action Potential Triggered by depolarization Membrane potential must reach
threshold -60 mV
Figure 8.8 5
Potential cont… Repolarization Return to resting potential
Figure 8.8 5