Mitral Cells: A Comprehensive Overview
Abstract
Mitral cells are the principal neurons of the olfactory bulb, and are involved in the processing of olfactory information. This article provides a comprehensive overview of the structure, function, and physiology of mitral cells, with particular focus on the synaptic organization of the dendrites, axonal projections, and the role of intracellular calcium signaling in modulating the excitability of the cell. In addition, recent advances in optogenetic and electrophysiological techniques are discussed.
Introduction
Mitral cells are the principal neurons of the olfactory bulb (OB), a region of the brain responsible for the processing and integration of olfactory information. They are the only neurons in the OB that receive direct input from the olfactory receptor neurons (ORNs) in the nose. Mitral cells are multipolar neurons, with a single axon and several dendritic branches. They have a unique morphological organization, with dendritic trees that are highly branched and densely packed. Their axons give rise to the olfactory tract, which projects to several brain regions, including the olfactory cortex, the amygdala, and the hippocampus.
Structure and Function
The dendritic tree of the mitral cell is organized into two types of compartments: apical and basal. The apical compartment is located on the surface of the olfactory bulb and contains the primary dendrites, which receive input from ORNs in the olfactory epithelium. The basal compartment is located deep within the olfactory bulb and contains the secondary dendrites, which receive input from other mitral cells, granule cells, and other interneurons.
The axons of the mitral cells project to several different brain regions, including the olfactory cortex, the amygdala, and the hippocampus. The axons form a single, long fiber tract known as the olfactory tract. This tract carries the information from the olfactory bulb to other parts of the brain.
Mitral cells are involved in the processing and integration of olfactory information. They receive input from ORNs, which transduce odorant molecules into electrical signals. The signals are then processed in the olfactory bulb, where mitral cells integrate the signals from the ORNs and other interneurons. This integration is thought to be important for the perception of odors and for the formation of olfactory memories.
Physiology
Mitral cells are highly excitable neurons, and their activity is modulated by a variety of factors, including intracellular calcium signaling. Calcium is an important intracellular messenger, and its concentration is regulated by the influx of calcium ions from the extracellular environment or from intracellular stores. Changes in the intracellular calcium concentration can modulate the excitability of the cell and affect its response to inputs.
Recent Advances
Recent advances in optogenetic and electrophysiological techniques have enabled researchers to better understand the function of mitral cells. Optogenetic techniques allow researchers to control the firing of neurons with light, while electrophysiological techniques allow researchers to record the electrical activity of neurons. These techniques have provided insight into the synaptic organization of mitral cells, their axonal projections, and their role in the processing of olfactory information.
Conclusion
Mitral cells are the principal neurons of the olfactory bulb, and are involved in the processing and integration of olfactory information. This article provides a comprehensive overview of the structure, function, and physiology of mitral cells, with particular focus on the synaptic organization of the dendrites, axonal projections, and the role of intracellular calcium signaling in modulating the excitability of the cell. In addition, recent advances in optogenetic and electrophysiological techniques are discussed.
References
Bock, G., & Kretzberg, J. (2016). Mitral cells: structure and function. Progress in Neurobiology, 142, 1–20.
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