Anatomy & Physiology

Anatomy & Physiology Study Guide 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, and back and to the visceral organs of the thoracic and peritoneal cavities. There are the relay stations along sensory and motor pathways that receive visceral sensory information that reaches the CNS from the spinal nerves and cranial nerves. This information is integrated and forwarded to other autonomic centers in the brain. Pons The pons links the cerebellum with the mesencephalon, diencephalon, cerebrum, and spinal cord. The pons contains four groups of components. The pons contains many of the sensory and motor nuclei of cranial nerves. These cranial nerves (V, VI, VII, and VIII) innervate the jaw muscles, the anterior surface of the face, one of the extra-ocular muscles (the lateral rectus), and provide sensation for the organs of the inner ear (the vestibular and cochlear nuclei). The pons also contains nuclei involved with the control of respiration. On each side of the pons, the reticular formation in this region contains two respiratory centers: the apneustic center and the pneumotaxic center. These centers transform the activity of the respiratory rhythmicity center in 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, brain stem, 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. It has two primary functions. One function is adjusting the postural muscles of the body. The cerebellum controls rapid, automatic adjustments that maintain equilibrium and balance. These changes in position and muscle tone are produced by modifying the activities of motor centers in the brain stem. The second major function is programming and fine-tuning movements controlled at the conscious and subconscious levels. The cerebellum refines learned movement patterns. This function is performed indirectly by controlling activity along motor pathways at the cerebral cortex, basal nuclei, and motor centers in the brain stem. The cerebellum has a multifaceted surface composed of neural cortex. The folia , or folds of the cerebellum surface, are less prominent than the folds in the surfaces of the cerebral hemispheres. The anterior and posterior lobes are separated by the primary fissure. Along the midline, a narrow band of cortex, known as the vermis , separates the cerebellar hemispheres. The slender flocculonodular lobe lies between the roof of the fourth ventricle and the cerebellar hemispheres and vermis. The cerebellum has a superficial layer of neural cortex. The cerebellar cortex contains large, highly branched Purkinje cells . The extensive dendrites of each Purkinje cell receive input from up to 200,000 synapses. Inside, the white matter of the cerebellum creates a branching array that resembles a tree. Anatomists call it the arbor vitae , or “tree of life.”

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