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The right and left hemispheres of the brain are connected by a bridge of sorts so that information can be exchanged. The diencephalon (interbrain) contains the thalamus and hypothalamus, with the former being important for consciousness and transmitting sensory input, and the latter being a hormone production site, as well as the center for circulation, breathing, temperature regulation, and sleep-wake rhythm. The midbrain processes and transmits a great deal of information related to movement. Eye movements are controlled from here. And Substantia nigra (black substance) ensures the release of dopamine, which is stimulated by movement and whose function is impaired in Parkinson’s patients, for example. The mid-brain is already part of the brain stem, which phylogenetically represents a very old part of the brain and, unlike the cerebrum, has hardly changed during the course of human evolution.

The spinal cord acts as an extension of the brain stem and is essentially the highway for nerve signals into the body, carrying all signals from the brain everywhere (except for the cranial nerves themselves, which control the eyes, ears, inner ear, tongue and throat, face, etc.). Some nerve signals reach speeds of up to 120 meters per second, while other nerves are much slower. (You know what this is like: You stub your toe on the edge of the bed, drop something on it or jam it in the garage door. You know what’s about to happen, but the pain is still 1 to 2 seconds away. The nerves that send this signal transmit it at a speed of only 1 to 2 meters/second, hence the delayed onset of pain.) The speed of conduction depends on the type of nerve involved. Some are surrounded by a nerve sheath that has small constrictions. The electrical signals then jump from ring to ring, reaching the highest speeds. Nerve sheaths are primarily made of cholesterol and their structure is damaged in patients with the disease “multiple sclerosis”. Small nerve roots are released by the spinal cord between the vertebrae, which branch off to the right and left, supplying individual areas of the body with signals and transporting them back again.