4 BRAIN STEM AND CEREBELLUM 4.1. Brain Stem Surface Anatomy: Posterolateral View 4.2. Brain Stem Surface Anatomy: Anterior View 4.3. Cerebellar Anatomy: External Features 4.4. Cerebellar Anatomy: Internal Features 4.1 BRAIN STEM SURFACE ANATOMY: POSTEROLATERAL VIEW The entire telencephalon, most of the diencephalon, and the cerebellum are removed to reveal the dorsal surface of the brain stem. The three cerebellar peduncles (superior, middle, and inferior) are sectioned and the cerebellum removed. The dorsal roots provide input into the spinal cord, and the cranial nerves provide input into and receive output from the brain stem. The fourth nerve (trochlear) is the only cranial nerve to exit dorsally from the brain stem. The tubercles and trigones on the floor of the fourth ventricle are named for nuclei just beneath them. The superior and inferior colliculi form the dorsal surface of the midbrain, and the medial and lateral geniculate nuclei (associated with auditory and visual processing, respectively) are shown at the caudalmost region of the diencephalon. CLINICAL POINT The facial colliculus is an elevation on the floor of the fourth ventricle in the pons under which is located the abducens nucleus (cranial nerve VI) and the axons of the facial nerve nucleus (VII), which arc around the abducens nucleus. A tumor or other lesion on one side of the floor of the fourth ventricle may induce symptoms related to cranial nerves VI and VII, including ipsilateral paralysis of lateral gaze (lateral rectus) and medial gaze (resulting from damage to nerve VI’s interneurons, which ascend to the nucleus of CN III via the medial longitudinal fasciculus) as well as ipsilateral facial palsy. The cerebellar peduncles convey the cerebellar afferent and efferent fibers. The superior peduncle conveys the major efferents to the red nucleus and thalamus (especially the ventrolateral nucleus), whereas the inferior peduncle conveys the major efferents to the vestibular and reticular nuclei. The middle peduncle conveys the corticoponto-cerebellar fibers. Afferents enter the cerebellum especially through the inferior peduncle but also through the superior peduncle. Damage to the lateral hemisphere of the cerebellum or its associated peduncles can result in ipsilateral symptoms, including limb ataxia, mild hypotonia, dysmetria (misjudgment of distance), decomposition of movement (especially movement involving several joints), intention tremor (with movement), dysdiadochokinesia (inability to perform rapid alternating movements), and inability to dampen movements appropriately (rebound phenomena). Only gold members can continue reading. Log In or Register to continue Share this:Click to share on Twitter (Opens in new window)Click to share on Facebook (Opens in new window) Related Related posts: VENTRICLES AND THE CEREBROSPINAL FLUID SPINAL CORD MOTOR SYSTEMS VASCULATURE DEVELOPMENTAL NEUROSCIENCE SENSORY SYSTEMS Stay updated, free articles. Join our Telegram channel Join Tags: Netters Atlas of Neuroscience with STUDENT CONSULT Online Access Jun 4, 2016 | Posted by admin in NEUROLOGY | Comments Off on BRAIN STEM AND CEREBELLUM Full access? Get Clinical Tree
4 BRAIN STEM AND CEREBELLUM 4.1. Brain Stem Surface Anatomy: Posterolateral View 4.2. Brain Stem Surface Anatomy: Anterior View 4.3. Cerebellar Anatomy: External Features 4.4. Cerebellar Anatomy: Internal Features 4.1 BRAIN STEM SURFACE ANATOMY: POSTEROLATERAL VIEW The entire telencephalon, most of the diencephalon, and the cerebellum are removed to reveal the dorsal surface of the brain stem. The three cerebellar peduncles (superior, middle, and inferior) are sectioned and the cerebellum removed. The dorsal roots provide input into the spinal cord, and the cranial nerves provide input into and receive output from the brain stem. The fourth nerve (trochlear) is the only cranial nerve to exit dorsally from the brain stem. The tubercles and trigones on the floor of the fourth ventricle are named for nuclei just beneath them. The superior and inferior colliculi form the dorsal surface of the midbrain, and the medial and lateral geniculate nuclei (associated with auditory and visual processing, respectively) are shown at the caudalmost region of the diencephalon. CLINICAL POINT The facial colliculus is an elevation on the floor of the fourth ventricle in the pons under which is located the abducens nucleus (cranial nerve VI) and the axons of the facial nerve nucleus (VII), which arc around the abducens nucleus. A tumor or other lesion on one side of the floor of the fourth ventricle may induce symptoms related to cranial nerves VI and VII, including ipsilateral paralysis of lateral gaze (lateral rectus) and medial gaze (resulting from damage to nerve VI’s interneurons, which ascend to the nucleus of CN III via the medial longitudinal fasciculus) as well as ipsilateral facial palsy. The cerebellar peduncles convey the cerebellar afferent and efferent fibers. The superior peduncle conveys the major efferents to the red nucleus and thalamus (especially the ventrolateral nucleus), whereas the inferior peduncle conveys the major efferents to the vestibular and reticular nuclei. The middle peduncle conveys the corticoponto-cerebellar fibers. Afferents enter the cerebellum especially through the inferior peduncle but also through the superior peduncle. Damage to the lateral hemisphere of the cerebellum or its associated peduncles can result in ipsilateral symptoms, including limb ataxia, mild hypotonia, dysmetria (misjudgment of distance), decomposition of movement (especially movement involving several joints), intention tremor (with movement), dysdiadochokinesia (inability to perform rapid alternating movements), and inability to dampen movements appropriately (rebound phenomena). Only gold members can continue reading. Log In or Register to continue Share this:Click to share on Twitter (Opens in new window)Click to share on Facebook (Opens in new window) Related Related posts: VENTRICLES AND THE CEREBROSPINAL FLUID SPINAL CORD MOTOR SYSTEMS VASCULATURE DEVELOPMENTAL NEUROSCIENCE SENSORY SYSTEMS Stay updated, free articles. Join our Telegram channel Join Tags: Netters Atlas of Neuroscience with STUDENT CONSULT Online Access Jun 4, 2016 | Posted by admin in NEUROLOGY | Comments Off on BRAIN STEM AND CEREBELLUM Full access? Get Clinical Tree
