Inland cells
The inner cells receive nerve impulses from the sensitive nerve cells (neurons) located in the spinal ganglia and send their extensions (axons) to the posterior horn of the spinal cord. However, their axons remain within the gray matter and transmit the incoming information to different other nerve cells, depending on the cell type. The inner cells can be subdivided into The cells of the autologous apparatus connect nerve cells of the spinal cord with each other mainly as so-called intermediate neurons (interneurons).
They are scattered in the gray matter of the spinal cord at various locations. This autologous apparatus ensures that, on the one hand, if the skin experiences a sting, for example, defensive movements take place through the direct connections to the anterior horn cells, which still function even if the spinal cord is separated from the brain by a cut.By means of cross-segment communication, all those cells in the anterior horn that are required to move a muscle or group of muscles can be reached, and the cross connections between the halves of the spinal cord also trigger a movement in the same direction on the other side: the reaction is bilateral. For example, if we stumble with our left foot, there must still be reactions on both sides of the body to cushion the fall.
A simple reflex path also works on this level. The “long” strand cells lie in the nuclei of the posterior horn of the spinal cord. They belong to the afferent, i.e. the ascending, feeding system: The cell bodies receive their information from the spinal ganglion, which is the first switching station (1st neuron) for sensitive information from inside the body and from the body surface, and thus form the second switching station (2nd neuron) on the way to the brain.
Their extensions are long and form thick strands or pathways that ascend to the brain. These run in the white matter on each side of the spinal cord at the front and sides, in the so-called front strands and side strands.
- “short” cells of the spinal cord’s own apparatus and
- “long” strand cells
- Switching cells connect nerve cells of the spinal cord that are located on the same side (= ipsilateral) and on the same level (segment). The
- Commissure cells connect nerve cells that are located on the opposite side (= contralateral) of the spinal cord, but on the same level and
- Association cells connect nerve cells that are on the same side but on different levels, i.e. they belong to different “segments”.
- Not only individual muscle fibers and muscle bundles, but entire muscles and muscle groups are activated in response to a sensitive stimulus
- Independent of the circuitry in the brain:
