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