![]() ![]() These neurons passing through the medulla also form many relays, where one neuron passes its signal on to another neuron that continues onward to the brain or body. Although the reason for this switch is unknown, it explains why the brain feels and controls the contralateral side of the body. The medulla contains all of the neurons that connect the brain to the spinal cord, and it is at the level of the medulla that about 90% of these neurons switch from the left side of the body to the right and vice versa. Stimulation of the cerebral cortex by the reticular formation produces the effect of being awake and conscious, while the inactivation of the reticular formation leads to sleep. The reticular formation, which extends throughout the brain stem, performs several important functions, including the stimulation of the cerebral cortex and the production of muscle tone. Ten of the brain’s twelve cranial nerves also originate in the brain stem, providing vital connections between the brain and the sensory organs, heart, and digestive organs. ![]() The spinothalamic tract for pain, itch, and other signals.The posterior column-medial lemniscus pathway for senses including proprioception and fine touch.The corticospinal tract for motor signals.Through its white matter, the brain stem forms the connections between the brain and the body via the spinal cord, including: The brain stem, through its gray matter, provides many of the basic survival and reflex functions for the body. Finally, the midbrain forms the most superior and most complex region of the brain stem.Superior to the medulla is the pons, which is larger and structurally more complex than the medulla.It is a tube very similar structurally to the spinal cord, but is wider and contains several masses of gray matter internally. The medulla is the inferior-most region of the brain stem that connects the brain to the spinal cord.Three major regions make up the brain stem: medulla oblongata, pons, and midbrain. The reticular formation, a network of mixed gray and white matter, extends throughout the interior of the brain stem and plays an important role in stimulation of the cerebrum and the muscles of the body. Masses of gray matter, known as nuclei, perform the processing role of the brain stem. The exterior of the brain stem consists of white matter that conducts nerve signals within the brain stem and to the spinal cord and other regions of the brain. It is located at the base of the brain, superior to the spinal cord and inferior to the cerebrum.Īs the brain stem ascends from the spinal cord, it widens and becomes more complex in its structures, both internally and externally. The brain stem is a tube-shaped mass of nervous tissue a little over 3 inches (8 cm) long. It forms the connection between the brain and the spinal cord, maintains vital control of the heart and lungs, and coordinates many important reflexes. The brain stem is one of the most basic regions of the human brain, yet it is one of the most vital regions for our body’s survival. ![]()
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