Nursing Entrance Exam

7.1.7 Brain Functions Medulla Oblongata The medulla oblongata is the most inferior of the brain regions, and it includes the attachment sites for 11 of the 12 pairs of cranial nerves. The medulla oblongata is a busy organ; in fact, all communication between the brain and spinal cord involves the medulla oblongata. In addition, the medulla oblongata is a center for the coordination of autonomic reflexes and visceral functions. The medulla oblongata includes three groups of nuclei. The autonomic nuclei that control visceral activities are located in the medulla oblongata. The reticular formation is a loosely organized mass of gray matter that contains embedded nuclei. The portion of the reticular formation found in the medulla oblongata contains nuclei and centers that are responsible for regulating vital autonomic functions. These reflex centers receive inputs from cranial nerves, the cerebral cortex, and the brainstem. The cardiovascular centers adjust the heart rate, the strength of cardiac contractions, and the flow of blood through peripheral tissues. There are also the sensory and motor nuclei of cranial nerves. The medulla oblongata contains sensory and motor nuclei associated with five of the cranial nerves (VIII, IX, X, XI, and XII). These cranial nerves provide motor commands to muscles of the pharynx, neck, back, and to the visceral organs in the peritoneal and thoracic cavities. Finally, relay stations are located along sensory and motor pathways, and they receive visceral sensory information that reaches the CNS from the spinal nerves and cranial nerves. This information is incorporated and advanced to other autonomic centers in the medulla oblongata andelsewhere. Pons The pons links the cerebellum with the mesencephalon, diencephalon, cerebrum, and spinal cord. The pons is comprised of four component groups, and it contains many of the sensory and motor nuclei of cranial nerves. These cranial nerves (V, VI, VII, and VIII) stimulate the jaw muscles, the anterior area of the face, and one of the extraocular muscles (the lateral rectus). In addition, the cranial nerves provide sensation for the organs of the inner ear, such as the vestibular and cochlear nuclei. The pons also contains nuclei involved with respiration control. On each side of the pons, the reticular formation contains two respiratory centers: the apneustic center and the pneumotaxic center. These centers modify the activity of the respiratory rhythm center within the medulla oblongata. The pons also contains nuclei and tracts that process and relay information heading to or from the cerebellum. The pons connects the cerebellum to the cerebrum, brainstem, and spinal cord. Finally, the pons contains ascending, descending, and transverse tracts that interconnect other portions of the CNS. The Cerebellum The cerebellum is an automatic processing center with two primary functions. One function is adjusting the postural muscles of the body. The cerebellum controls the rapid, automatic adjustments that maintain equilibrium and balance. The changes in position and muscle tone are made by

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