lateral loop

Definition

Target type: cellularcomponent

Non-compact myelin located adjacent to the nodes of Ranvier in a myelin segment. These non-compact regions include cytoplasm from the cell responsible for synthesizing the myelin. Lateral loops are found in the paranodal region adjacent to the nodes of Ranvier, while Schmidt-Lantermann clefts are analogous structures found within the compact myelin internode. [GOC:dgh]

The lateral loop is a specialized cellular structure found in the axons of certain neurons, primarily in the central nervous system. It is characterized by a distinctive loop-like morphology, with the axon forming a hairpin turn, creating two parallel segments that run adjacent to each other. The cellular components of the lateral loop are:

1. **Axon:** The core component of the lateral loop is the axon, which is a long, slender projection of the neuron that carries nerve impulses away from the cell body. In the lateral loop, the axon forms the loop itself, with two segments running parallel to each other.

2. **Myelin Sheath:** The axon in the lateral loop is typically myelinated, meaning it is surrounded by a fatty insulating layer called the myelin sheath. This sheath is formed by glial cells, such as Schwann cells in the peripheral nervous system and oligodendrocytes in the central nervous system. Myelin enhances the speed of nerve impulse conduction along the axon.

3. **Nodes of Ranvier:** Along the myelinated axon, there are gaps in the myelin sheath called nodes of Ranvier. These gaps expose the axon membrane, allowing for the generation of action potentials, or nerve impulses. The nodes of Ranvier play a crucial role in saltatory conduction, where nerve impulses jump from one node to the next, increasing the speed of conduction.

4. **Axonal Cytoplasm:** The axon is filled with axoplasm, a specialized cytoplasm that contains various organelles and molecules necessary for neuronal function. This includes microtubules, neurofilaments, mitochondria, and other components involved in axonal transport, the movement of molecules and organelles along the axon.

5. **Axolemma:** The axolemma is the plasma membrane that surrounds the axon. It is responsible for regulating the movement of substances in and out of the axon, including ions, neurotransmitters, and other signaling molecules.

6. **Presynaptic Terminal:** The lateral loop may have a presynaptic terminal at the end of the axon, where the nerve impulse is transmitted to another neuron or target cell. This terminal contains synaptic vesicles filled with neurotransmitters that are released into the synaptic cleft, the space between neurons, to signal the next cell.

7. **Glial Cells:** In addition to the myelin-forming glial cells, other glial cells, such as astrocytes, may be associated with the lateral loop. Astrocytes provide structural support, regulate the extracellular environment, and play a role in neuronal signaling.

The lateral loop is thought to be involved in a variety of neuronal functions, including signal processing, neuronal plasticity, and synaptic transmission. It is a complex structure with a unique morphology and cellular composition that contributes to the efficient and coordinated communication within the nervous system.'
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Compounds (34)