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Neurons
Neurons
Neuron Cell Structure
Cell bodies
- The command center of neuronal signaling; their dendrites which receive signals (typically from other neurons) and send them to the cell body.
- They are the railroad station.
Axons
- Transmits signals to/from the cell body.
- They are the railroad track.
Cerebral Cortical Neurons
Types
2 Types:
Pyramidal cells
- 10 to 80 micrometers in diameter and are shaped like a flask with a single thick, cortically oriented apical dendrite and multiple basal dendrites. One important pyramidal cell type is the Betz cell, which lies within the primary motor cortex.
Non-pyramidal cells
- 5 to 15 micrometers in diameter. The term non-pyramidal cell is used interchangeably with the terms stellate or granule cells. But other non-pyramidal cell types exist, which include basket cells, fusiform cells, Horizontal cells of Cajal, Martinotti cells, and neurogliaform cells.
Histology
- Large, basophilic cytoplasm.
- Large nucleus with diffuse chromatin.
- Prominent nucleolus.
- Neuronal process.
Spinal Motor Neurons
Histology
Lies within the anterior horn of the spinal cord. We note the following:
- Cell body
- Nucleus and nucleolus (which is prominent)
- Dendrite (a dendritic process)
- Axon hillock, which is cone-shaped and connects the cell body to the base of the axon.
Axon Hillock Physiology
- Membrane potentials from throughout the cell body spread to the axon hillock.
- If they depolarize it to its threshold, the axon will fire an action potential.
- Thus, the axon hillock is the decision-making center of the neuron.
Images
- Histological images modified with permission from http://medsci.indiana.edu/a215/virtualscope/docs/chap6_3.htm