Nerves Flashcards
What are peripheral Nerves?
Axons extend throughout the body and are fragile and easily damaged. They arise from the CNS (motor neurons), dorsal root ganglia (sensory neurons) and autonomic nervous system ganglia (motor neurons).
Some axons are myelinated to increase speed of the action potential transmission and increase likelihood of firing.
What connective tissues wrap axons?
Axons are wrapped in connective tissue:
- Epineurium wraps the whole nerve
- Perineurium wraps fascicles (bundles of axons)
- Endoneurium wraps the individual axons
What are Schwann cells?
A Schwann cell is involved in myelination and is used to support axons. They have visible nuclei in H&E sections. The Schwann cell wraps multiple times around the axon and lays down myelin in the glial cell membrane.
What are the nodes of Ranvier?
Schwann cells myelinate successive lengths of axon and leave a small gap which is called a node of ranvier. These nodes are the mechanism for which myelination improves the speed of action potentials.
What are ganglia?
Ganglia are collections of neurons that exist outside the CNS.
They include dorsal root ganglia (sensory) and sympathetic and parasympathetic ganglia (autonomic motor) (as well as satellite cells (glia) to support neurons)
