Overview
This lecture covers the main cell types of the nervous system—neurons and glia—with focus on their roles and structural differences in the central and peripheral nervous systems.
Divisions of the Nervous System
- The nervous system is divided into the Central Nervous System (CNS: brain, brainstem, spinal cord) and Peripheral Nervous System (PNS: nerves extending from CNS).
- Neurons and glia are present in both CNS and PNS.
Neurons: Structure and Function
- Neurons are excitable cells that send signals to other neurons, muscles, or glands.
- Main parts of a neuron: dendrites (receive signals), soma (cell body), axon hillock (initiates action potential), axon (transmits signal), and synaptic terminals (communicate with target cells).
- The synapse is the gap between neurons and their target cells, allowing chemical signal transmission.
- Most neurons are myelinated, meaning their axons are insulated by a fatty myelin sheath to enhance signal transmission.
Glia in the Central Nervous System (CNS)
- Oligodendrocytes create myelin sheaths for CNS neurons by wrapping their axons.
- Astrocytes support neurons, maintain the environment, and are involved in the blood-brain barrier.
- Ependymal cells line brain ventricles and produce cerebrospinal fluid (CSF).
- Microglia act as immune cells, using phagocytosis to remove debris or invaders.
Glia in the Peripheral Nervous System (PNS)
- Schwann cells produce the myelin sheath for PNS neuron axons, with each Schwann cell myelinating a single segment.
- Satellite cells surround and support neuron cell bodies (ganglia) in the PNS, maintaining their environment.
Key Terms & Definitions
- Neuron — Excitable cell that communicates via electrical and chemical signals.
- Glia — Supporting cells of the nervous system; term means "glue."
- Myelin — Fatty layer insulating axons to speed up signal transmission.
- Oligodendrocyte — CNS glial cell that myelinates axons.
- Astrocyte — CNS glial cell involved in support and blood-brain barrier.
- Ependymal cell — CNS glial cell producing CSF in brain ventricles.
- Microglia — CNS glial cell acting as immune defense.
- Schwann cell — PNS glial cell myelinating axons.
- Satellite cell — PNS glial cell supporting neuron cell bodies.
- Ganglia — Clusters of neuron cell bodies in the PNS.
Action Items / Next Steps
- Review diagrams of neuron and glial cell structures.
- Study the differences between CNS and PNS glial cells.
- Prepare for a quiz on cell types and their functions in the nervous system.