Chapter 6 - Nerve Tissue
The nervous system is specialized for communication of information from one region of the body to another.
The neuron is the structural and functional unit of the nervous system. Nerve cells are specialized to receive input from other cells and then convey this information to other cells.
A synapse is a junction between two neurons in which impulses pass by diffusion of an extracellular neurotransmitter.
Glial cells (or neuroglia) provide support and protection to neurons. Four types of cells are found in the central nervous system:
- Astrocytes - provide physical and metabolic support
- Oligodendrocytes - form myelin sheaths around multiple axons
- Microglia - phagocytic cells
- Ependymal Cells - line the ventricles of the brain and the central canal of the spinal cord
A variety of glial cells are associated with the peripheral nervous system.
- Schwann Cells - isolates axons from the surrounding extracellular compartment
- Non-myelinating - Schwann cells encapsulates multiple non-myelinated axons
- Myelinating - Schwann cells wrap a segment of a single axon with a myelin sheath
- Satellite Cells - small cuboidal cells that surround the cell bodies of nerve cells in ganglia
- specialized Glial Cells - associated with specific tissues or organs
Peripheral nerves contain the axons of both motor neurons and sensory neurons that connect with the spinal cord. They are surrounded by multiple layers of connective tissue.
Myelinated axons are a portion of a neuron that is encapsulated by a fatty layer called the myelin sheath. The speed of conduction of myelinated axons is faster than non-myelinated axons.
A neuromuscular junction (or motor endplate) is a specialized synapse between a motor neuron and a skeletal muscle cell. It transmits a signal to the muscle fiber causing its contraction.