Nervous System Cells Overview

Nervous System Cells

• Neurons are signal-transmitting cells with dendrites (input), cell bodies, and axons (output)
• Dendrites and cell bodies stain with Nissl stain, axons do not
• Neurofilament protein and synaptophysin are neuron markers
• Astrocytes physically support neurons, repair, remove excess neurotransmitters, and form part of the blood-brain barrier
• Astrocytes store glycogen and buffer ions
• GFAP is an astrocyte marker
• Oligodendrocytes myelinate axons in the central nervous system (CNS)
• Oligodendrocytes also called "fried egg" appearance historically
• Each oligodendrocyte can myelinate multiple axons (aprox. 30)
• Ependymal cells are ciliated columnar cells lining ventricles and spinal cord central canals
• Ependymal cells circulate cerebrospinal fluid (CSF) and absorb it through microvilli
• Microglia are phagocytic cells in the CNS, responding to tissue damage by releasing inflammatory mediators
• Microglial activation involves releasing nitric oxide and glutamate
• Satellite cells surround neuronal cell bodies in ganglia
• Schwann cells myelinate axons in the peripheral nervous system (PNS)
• Each Schwann cell myelinates one axon

CNS Glial Cells

• CNS glial cells are derived from neuroectoderm, except microglia
• Myelin is a layered wrapping around axons that increases signal conduction speed
• Myelin increases transmission velocity
• Saltatory conduction occurs at nodes of Ranvier
• Astrocytes are the most abundant type of glial cell in the CNS
• Astrocytes play role in reactive gliosis, in response to neural injury
• Microglia are phagocytic cells, responding to tissue damage and infection
• Microglia can fuse to form multinucleated giant cells (as seen in HIV-associated dementia)
• Microglia are derived from mesodermal precursors

PNS Glial Cells

• PNS glial cells are derived from neural crest ectoderm
• Satellite cells surround neurons in peripheral ganglia, having a similar supportive role as astrocytes in the CNS
• Schwann cells myelinate axons in the peripheral nervous system
• A single Schwann cell myelinates one axon

Neuron Action Potential

• Resting membrane potential is more permeable to K+ than Na+
• Depolarization occurs with Na+ influx
• Na+ channel inactivates at peak potential
• Repolarization occurs with K+ efflux
• Hyperpolarization occurs due to slow K+ channel closure
• Na+/K+ pump restores ion concentration

Sensory Receptors

• Free nerve endings detect pain and temperature
• Meissner corpuscles detect light touch and low-frequency vibrations
• Pacinian corpuscles detect high-frequency vibrations and pressure
• Merkel discs detect sustained pressure and touch
• Ruffini corpuscles detect stretch and joint movement

This quiz covers the various types of cells in the nervous system, including neurons, astrocytes, oligodendrocytes, ependymal cells, and microglia. Learn about their structures, functions, and markers to better understand the complexities of the central nervous system. Test your knowledge on how these cells interact and contribute to neural operations.