What nerve routes are followed by impulses passing through the nervous system?

There are two main nerve routes that impulses can take when passing through the nervous system: the ascending tracts and the descending tracts.

Ascending Tracts

Ascending tracts carry sensory information from the peripheral nerves to the brain. There are three main types of ascending tracts:

* Spinothalamic tracts: These tracts carry information about pain, temperature, and touch from the skin and muscles to the brain.

* Posterior column tracts: These tracts carry information about proprioception (the sense of body position) and fine touch from the skin to the brain.

* Trigeminothalamic tracts: These tracts carry information from the face to the brain.

Descending Tracts

Descending tracts carry motor commands from the brain to the muscles. There are two main types of descending tracts:

* Pyramidal tracts: These tracts carry voluntary motor commands from the cerebral cortex to the spinal cord.

* Extrapyramidal tracts: These tracts carry involuntary motor commands from the brain to the spinal cord.

The ascending and descending tracts are organized somatotopically, which means that they are arranged in a way that corresponds to the body's surface. This organization allows the brain to receive and process information from specific parts of the body and to send motor commands to specific parts of the body.