Brainstem Medulla David A. Morton, Ph.D. Jan 17th, 2013 Objectives • • • • • • • • • Describe the trajectory of the cranial nerves, their components, and their functions Identify and locate the CN’s associated with the medulla, the pons and the midbrain. Explain how cranial nerves differ from spinal nerves List the cranial nerves that contain parasympathetic fibers, the location of their nuclei, and their function Recognize the major internal and external landmarks on the dorsal and ventral surface of the brain stem, so that you can determine if a gross or stained cross section is medulla, pons or midbrain. Identify on a typical cross section all the brain stem nuclei containing motor neurons that end on striated muscle. Explain why cranial nerves are so important in localizing lesions. Name reflexes that test these nerves and brain stem levels. Relate branches of the vertebrobasilar blood supply to the medulla and pons explaining the deficits that would occur with vascular occlusion. Internal anatomy of brainstem The fate of the alar and basal laminae • Why are brain stem sensory nuclei lateral Alar Sulcus limitans Som S VS VM SM to motor nuclei in brainstem? BM Basal Medulla Som S Alar Sulcus limitans VS VM SM Basal Spinal cord Medulla oblongata External anatomy: • Pyramid • Olive • CNN VIII, IX, X, XI and XII • Fourth ventricle • Vertebral arteries VIII O Medulla P Horizontal section IX & X XII XI O P Medulla oblongata Solitary nuclei and tract Som S Alar VS VM SM BM Basal Medulla Nucleus ambiguus Medulla Oblongata Hypoglossal nucleus (CN XII) • Somatic motor • Comparable to ventral horn • Tongue muscles Medulla Oblongata Dorsal motor nucleus (CN X) • Visceral motor • Comparable to lateral horn • Origin of preganglionic parasympathetic neurons Medulla Oblongata Inferior salivatory nucleus (CN IX) • Visceral motor • Comparable to lateral horn (can not see it on brains) • Origin of preganglionic parasympathetic neurons to otic ganglion Medulla Oblongata Nucleus ambiguus (CN IX and X) • Branchial (spec visc) motor • Origin of BM neurons for IX and X Medulla Oblongata Reticular formation • Forms the central core of brain stem • Nuclear groups not obvious Medulla Oblongata Vascular supply: • Vertebra artery •Anterior spinal artery PICA • PICA Vert Ant sp Objectives • • • • Explain what the meninges cover and what spaces they surround. For each meningeal space describe a classic source for blood in the space. Describe where CSF is produced and how it circulates and is removed. Name the most likely sites of obstruction of CSF circulation and the consequences. • Explain how the Blood Brain Barrier is different from the CSF Brain interface. Cranial Meninges Dura mater Arachnoid mater Pia mater Cranial Meninges Dura mater (2 layers in the skull) • Periosteal layer and Meningeal layer • Dural venous sinus Dural Venous sinuses Meningeal hemorrhages Blood in meningeal spaces or potential spaces 1. Epidural hemorrhage 2. Subdural hemorrhage 3. Subarachnoid hemorrhage Epidural space Dura mater • Middle meningeal artery Epidural hemorrhage Torn middle meningeal a. Epidural hemorrhage Subdural space Dura mater • Bridging cerebral vein • Courses between cerebrum and dural venous sinus Subdural hemorrhage Torn bridging cerebral v. What space is the artery located? Dural Venous sinuses Brain arteries – Subarachnoid space Internal carotid artery (ICA) • Ophthalmic • Anterior cerebral • Middle cerebral Vertebral artery • PICA • Basilar • AICA • SCA • Posterior cerebral Cerebral arterial circle of Willis • Anterior communicating • Anterior cerebral • ICA • Posterior communicating • Posterior cerebral Subarachnoid hemorrhage Stroke Organize the following terms: Cerebral aqueduct Lateral ventricle 4th ventricle Arachnoid granulations Superior sagittal sinus Lateral apertures 3rd ventricle Subarachnoid space Aqueduct of Sylvius Foramen of Magendie Median aperture Foramen of Monro Interventricular foramen Foramen of Luschka Choroid plexus Lateral ventricle Mesencephalic aqueduct The following terms are in order: Choroid plexus Lateral ventricle Interventricular foramen Lateral ventricle Foramen of Monro 3rd ventricle Cerebral aqueduct Aqueduct of Sylvius 4th ventricle Lateral apertures Foramen of Luschka Median aperture Foramen of Magendie Subarachnoid space Arachnoid granulations Superior sagittal sinus Mesencephalic aqueduct The ventricular system The ventricles, lined by ependymal cells, are obvious internal landmarks, and are important as internal structures to relate other structures to. Try to visualize them and rotate them with the brain. They will form the “wire frame” for our orientation to the brain. The ventricular system The ventricular system Hydrocephalus is dilation of all or part of the ventricular system due to obstruction of CSF flow. There are two types: 1. Obstructive (non-communicating) hydrocephalus. Block in the ventricular system or the outlet foramina. 2. Communicating (non-obstructive) hydrocephalus. Block in the subarachnoid space or the arachnoid granulations. a. Meningitis followed by scarring. b. Subarachnoid hemorrhage, meningeal fibrosis and scarring Copyright © 2010 Pearson Education, Inc. Hydrocephaly 1. Obstructive (noncommunicating) hydrocephalus. Block in the ventricular system or the outlet foramina. Copyright © 2010 Pearson Education, Inc. Hydrocephaly Copyright © 2010 Pearson Education, Inc. 2. Communicating (nonobstructive) hydrocephalus. Block in the subarachnoid space or the arachnoid granulations. Figure 12.26a Formation, location, and circulation of CSF. Superior sagittal sinus 4 Choroid plexus Arachnoid villus Interventricular foramen Subarachnoid space Arachnoid mater Meningeal dura mater Periosteal dura mater 1 Right lateral ventricle (deep to cut) Choroid plexus of fourth ventricle 3 Third ventricle Cerebral aqueduct Lateral aperture Fourth ventricle Median aperture Central canal of spinal cord (a) CSF circulation Copyright © 2010 Pearson Education, Inc. 2 1 CSF is produced by the choroid plexus of each ventricle. 2 CSF flows through the ventricles and into the subarachnoid space via the median and lateral apertures. Some CSF flows through the central canal of the spinal cord. 3 CSF flows through the subarachnoid space. 4 CSF is absorbed into the dural venous sinuses via the arachnoid villi.