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 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