AN68.1-3 | Nervous tissue histology — Glossary

Aggregates of rough ER and free polyribosomes in neurons that stain blue with cresyl violet; present in soma and dendrites, absent in axon hillock and axon

Dissolution of Nissl bodies in the neuronal soma following axon injury; indicates neuronal stress and shift to regenerative protein synthesis

The region of the soma where the axon originates; the trigger zone for action potential initiation; lacks Nissl substance but contains converging microtubules

A gap in the myelin sheath between adjacent Schwann cells (PNS) or oligodendrocyte segments (CNS) where sodium channels concentrate for saltatory conduction

The rapid jumping of action potentials from one node of Ranvier to the next along myelinated axons, greatly increasing conduction velocity

The myelinating glial cell of the PNS; one Schwann cell wraps around one axon segment (internode); also forms Remak bundles around unmyelinated axons

The myelinating glial cell of the CNS; one oligodendrocyte can myelinate segments of up to 50 different axons

Star-shaped CNS glial cell with GFAP filaments; forms the blood-brain barrier via end-feet on capillaries, buffers K+, and forms glial scars

The resident macrophage of the CNS derived from mesoderm; performs immune surveillance and phagocytosis of debris and pathogens

Flattened glial cells surrounding neuronal cell bodies in dorsal root ganglia and autonomic ganglia; provide metabolic and structural support

Degeneration of the axon and myelin sheath distal to a nerve injury site; Schwann cells proliferate and macrophages clear debris to form bands of Büngner

Columns of proliferating Schwann cells that form regeneration tubes guiding regrowing axons after nerve injury

The delicate connective tissue surrounding individual nerve fibres within a fascicle

The connective tissue sheath surrounding a nerve fascicle; forms the blood-nerve barrier

The outer connective tissue sheath surrounding an entire peripheral nerve; contains vasa nervorum

A cluster of pseudounipolar sensory neuron cell bodies located on the posterior root of each spinal nerve, each surrounded by satellite cells

An insulating lipid-protein sheath formed by spiral wrapping of Schwann cells (PNS) or oligodendrocytes (CNS) around axons

The junction between two neurons or between a neuron and an effector cell where neurotransmitter-mediated signal transmission occurs

A chemical substance released from presynaptic vesicles into the synaptic cleft to transmit signals to the postsynaptic cell

The movement of organelles, vesicles, and proteins along microtubules in axons; anterograde (kinesin) and retrograde (dynein)

Intermediate filaments (10 nm) that are the most abundant cytoskeletal element in axons; determine axon calibre; aggregate as neurofibrillary tangles in Alzheimer's

Acute inflammatory demyelinating polyneuropathy of PNS Schwann cells; post-infectious autoimmune; ascending flaccid paralysis with areflexia

Infection by Mycobacterium leprae that specifically targets Schwann cells via alpha-dystroglycan; the most common cause of non-traumatic peripheral neuropathy in India