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nervous system lecture for anatomy & physiology
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Chapter 10, Section 2
Neurons and Neuroglia
Structural Classification of Neurons
Multipolar neuron –
1 axon and many dendrites
• Includes most neurons in the brain
• Motor neurons and interneurons
Bipolar Neuron –
1 axon and 1 dendrite
• Some sensory neurons are bipolar
• Includes photoreceptors of retina • Includes photoreceptors of retina
and olfactory nerves
Unipolar Neurons
Single process extending from soma
• Peripheral Process – conducts
information from PNS
• Central Process – conducts information
to CNS
• Example: Dorsal root ganglion Figure 10.6. structural types of neurons
Functional Classification of Neurons
Afferent – Sensory
• Conducts information from PNS to CNS
• Dendrites may act as receptors (eyes, ears, touch)
• Most are unipolar, and some are bipolar
Efferent – Motor
• Conducts impulses from CNS to PNS• Conducts impulses from CNS to PNS
• Controls Effectors (muscles or glands)
•Voluntary Control – in somatic nervous system
• Involuntary control – in autonomic nervous system
Interneurons
• located within CNS
• links neurons in CNS together
• multipolar
Functional Classification of Neurons
Figure 10.7. Neurons classified by their functions. Sensory, Motor, and Interneurons.
Neuroglia in CNS
Astrocytes “star-shaped”
• Attach blood vessels to neurons
• Aid in metabolism
• Strengthen synapses
• Role in blood Brain barrier
Ependymal Cells
• Cuboidal or columnar epithelium
• Line central canal of spinal cord and ventricles of brain
• Regulate Cerebral Spinal Fluid (CSF)(CSF)
Microglia “small cells”
• Phagocytize bacteria and cell debris
• Proliferate with inflammation or infection of CNS
Oligodendrocytes
• Forms Myelin sheath in CNS
• 1 Oligodendrocytes covers several axons
Neuroglia in CNS
Figure 10.8. Types of neuroglia in the CNS.
Neuroglia compose half of the brain’s volume
Neuroglia of the PNS
Schwann Cells
• Forms Myelin Sheath in PNS
Satellite Cells
• Support cluster of cell bodies in PNS, called ganglia
1. Multiple Sclerosis (MS) – immune system attacks neurons in the CNS
• Myelin sheath is destroyed, leaving behind scars (scleroses)
• Scars block transmission of underlying neurons
• Muscles no longer receive stimulation from neurons and may
whither (atrophy)
Disorders of Neuroglia
Disorders of Neuroglia
2. Brain tumors
• most brain tumors are from neuroglia, not neurons
3. Huntington’s Disease
• May be caused by activation of microglia in CNS
• Microglia release neurotoxins, causing the degeneration of neurons
End Section 2, Chapter 10