Synapses are the bottleneck of the brain

Spinal pathways and reflexes

Abstract

The spinal cord is the switching point between the body's periphery and the brain. It receives information from the periphery with sensors (e.g. mechanosensors of the skin), the axons of which enter the spinal cord via the dorsal roots. In the spinal cord, these stimuli are conducted to the brain via the sensitive pathways of the connecting apparatus. On the other hand, the brain sends descending (motor) pathways to control the body's peripherals (e.g. the muscles).

In addition to the connecting apparatus, the spinal cord also has what is known as its own apparatus, which connects the various spinal cord segments with one another. These cross connections allow the spinal cord to mediate independent functions without the influence of the brain, the so-called spinal reflexes. These are stereotypical responses (e.g. muscle contraction) to characteristic stimuli (e.g. stretching) of a sensor (e.g. a muscle spindle). A typical example of spinal reflexes are muscle self-reflexes, which are checked as part of the neurological examination.

In addition to the already mentioned sensory and motor neurons of the spinal cord, there are accumulations of vegetative neurons in certain areas of the spinal cord. These serve, among other things, to control the autonomic nervous system and to interconnect so-called visceral and mixed reflexes.

Connection set and own set

The spinal cord has two main functions: The connection of different nerve centers with one another and the independent interconnection of spinal reflexes (see below). The pathways of the spinal cord run in the white matter and connect the spinal cord with the brain (connecting apparatus) on the one hand and various spinal cord segments with one another (self-apparatus) on the other. The connecting apparatus can be functionally divided into sensitive (ascending) and motor (descending) pathways.

Connecting device

The names of the ascending and descending lanes are usually named after their place of origin and destination. The first-named structure usually represents the origin of the path and the second-named structure its destination. For example, the anterior corticospinal tract connects the (motor) cortex with the spinal cord (medulla spinalis), whereas the lateral spinothalamic tract connects the spinal cord (spinal medulla) with the thalamus!

Own device

  • Definition or function: System of neurons for connecting several spinal cord segments to one another, among other things. for interconnecting spinal reflexes
  • Associated tracks
    • Directly adjacent to the gray matter: Fasciculi proprii anterior, - lateralis and - posterior
    • Lying between the connecting apparatus
      • Septomarginal fasciculus
      • Fasciculus interfascicularis
      • Fasciculus sulcomarginalis

Sensitive tracks

The sensitive tracts of the spinal cord convey the afferent information of the sensory cells in the periphery (e.g. the skin) via the spinal cord to the brain. The course of the sensitive pathways is slightly different, but their structure is very similar. Your 1st neuron is in the spinal ganglion, your 2nd neuron in the dorsal horn or brain stem, your 3rd neuron in the thalamus and your destination is the somatosensitive cortex.

Overview of the basic interconnection pattern

Overview of the sensitive pathways of the connection apparatus

In contrast to the other sensitive tracts of the spinal cord, the cerebellar lateral cords end in the cerebellum and not in the sensitive cortex. Therefore, this information is not consciously perceived!

Symptoms of isolated railway damage

Dissociated sensory disorder, e.g. in anterior spinal artery syndrome
The fibers of the anterior cord enter through the posterior horn, cross segmentally in the anterior commissura and then run ventrolaterally in the white matter as a bundled anterior cord to the thalamus. In the case of isolated damage to the anterior commissure (e.g. due to bleeding of the anterior spinal artery or a mass), only the fibers that cross segmental there are affected, but not the more lateral anterior cord. Therefore, there is an isolated loss of information from the segmental crossing pain and temperature fibers. Clinically, this manifests itself in a loss of pain and temperature sensations in the dermatome supplied by the affected spinal cord segment. Since the fine sense of touch (rear cords) remains unaffected in this segment, but the pain and temperature sensation is completely lost, one speaks of a so-called dissociated sensory disorder.