Nervous Tissue
1. Describe Nerve
A nerve is a bundle of nerve fibers that transmit signals between the central nervous system (CNS) and the peripheral nervous system (PNS).
- Nerve fibers are long, slender extensions of neurons that carry electrical signals.
- Nerve fibers are classified into two types: myelinated (A and B fibers) and unmyelinated (C fibers).
- The myelin sheath, a fatty insulating layer, surrounds myelinated nerve fibers, increasing the speed of electrical conduction.
- Nerve fibers are surrounded by a connective tissue sheath called the endoneurium.
2. Describe Transverse Section (T.S.) of Peripheral Nerve
The transverse section of a peripheral nerve shows the following structure:
- A nerve fascicle is a group of nerve fibers surrounded by the perineurium.
- The perineurium is a connective tissue sheath that surrounds a nerve fascicle.
- The endoneurium is a thin, delicate connective tissue sheath that surrounds individual nerve fibers.
- The nerve fibers are arranged in a specific pattern, with larger fibers in the center and smaller fibers on the periphery.
- The nerve fibers are surrounded by the endoneurium, which is in turn surrounded by the perineurium.
+---------------+ | Endoneurium | +---------------+ | Nerve Fibers | +---------------+ | Perineurium | +---------------+ | Fascicle | +---------------+
3. Describe Longitudinal Section (L.S.) of Peripheral Nerve
The longitudinal section of a peripheral nerve shows the following structure:
- The nerve fibers are arranged in a specific pattern, with larger fibers in the center and smaller fibers on the periphery.
- The nerve fibers are surrounded by the endoneurium.
- The endoneurium is in turn surrounded by the perineurium.
- The perineurium surrounds the nerve fascicles.
- The nerve fascicles are surrounded by the epineurium, a dense connective tissue sheath.
+---------------+ | Epineurium | +---------------+ | Perineurium | +---------------+ | Fascicle | +---------------+ | Endoneurium | +---------------+ | Nerve Fibers | +---------------+
Note: The diagrams are not to scale and are simplified for clarity.