17.12: Brainstem: Control Centers of Medulla
The medulla oblongata is a crucial part of the brainstem responsible for controlling various autonomic and involuntary functions. It contains several nuclei, including the olivary, cuneate, gracile, and solitary nuclei.
Olivary Nucleus
The olivary nucleus, or inferior olivary nucleus, is located within the ventrolateral part of the medulla oblongata. It is primarily involved in motor coordination and motor learning. The olivary nucleus receives input from the spinal cord, cerebellum, and motor cortex and sends output to the cerebellum via climbing fibers. This communication helps fine-tune motor movements and maintain balance.
Cuneate Nucleus
The cuneate nucleus is found laterally in the medulla oblongata and receives input from the cuneate fasciculus, which carries sensory information from the upper body's proprioceptors. It is involved in processing touch, pressure, vibration, and proprioceptive sensations. The cuneate nucleus then sends this information to the thalamus via the medial lemniscus pathway, contributing to motor control of skeletal muscles.
Gracile Nucleus
The gracile nucleus is situated medially in the medulla oblongata. It receives input from the gracile fasciculus, which carries sensory information from the lower body's proprioceptors. Like the cuneate nucleus, the gracile nucleus processes touch, pressure, vibration, and proprioceptive sensations and sends this information to the thalamus via the medial lemniscus pathway.
Solitary Nucleus
The solitary nucleus, also known as the nucleus tractus solitarius (NTS), is located in the dorsal part of the medulla oblongata. It receives sensory input from the facial, glossopharyngeal, and vagus nerves, which are responsible for taste sensation and visceral information from the thoracic and abdominal organs. The solitary nucleus regulates cardiovascular and respiratory activities, gastrointestinal motility, and taste sensation.
Control Centers
The medulla oblongata houses several control centers vital for maintaining bodily functions. The cardiovascular center regulates heart rate and blood vessel diameter, thereby controlling blood pressure. The respiratory center controls the rate and depth of breathing by receiving input from chemoreceptors and mechanoreceptors. It also harbors nuclei responsible for initiating reflex actions such as sneezing, hiccupping, and coughing to protect the respiratory system.
The solitary nucleus serves as the control center that regulates gastrointestinal motility by processing visceral information from the thoracic and abdominal organs. The solitary nucleus also processes taste sensations by receiving sensory input from the facial, glossopharyngeal, and vagus nerves. Both the cuneate and gracile nuclei contribute to motor control by processing sensory information from the upper and lower body's proprioceptors, respectively.
