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Download M555 Medical Neuroscience Lab 1: Gross Anatomy of Brain, Crainal
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M555 Medical Neuroscience Lab 1: Gross Anatomy of Brain, Crainal Nerves and Cerebral Blood Vessels Anatomical Directions Terms like “dorsal,” “ventral,” “anterior” and “posterior” provide a means of locating structures relative to the overall orientation of the nervous system. Complications with those terms may arise for two reasons: i) humans stand upright ii) the CNS curves or flexes as it grows from the neural tube, and the forebrain structures (telencephalon and diencephalon) are oriented somewhat differently than the brain stem (midbrain, pons, medulla, cerebellum) and spinal cord. This drawing shows the application of these terms to the human central nervous system. Forebrain Orientation telencephalon diencephalon dorsal superior rostral anterior caudal posterior forebrain brain stem midbrain pons ventral inferior medulla cerebellum spinal cord Brain Stem and Spinal Cord Orientation spinal cord rostral superior ventral anterior dorsal posterior caudal inferior Axis of CNS Part 2: Gross Anatomy of CNS Cranial Nerves There are twelve pairs of cranial nerves. Some are readily apparent; others are smaller and sometimes just the portion near the brain remains, making them more difficult to identify. We’ll cover the cranial nerves later in more detail. Some functions of the cranial nerves are included here as a brief introduction. Finding and naming the nerves are more important now. CN I Olfactory Nerve The nerve is very short and is destroyed when the brain is removed from the skull. Although the nerve is no longer present, structures associated with the nerve - the olfactory bulbs and olfactory tracts - are easily seen. CN II Optic Nerve Typically, proximal stumps of these nerves are visible after removal of the brain from the skull. Look for these associated structures - the optic tract and optic chiasm. CN III Oculomotor Nerve This nerve is associated with eye function. It is involved in constriction of the pupil and also in certain eye movements. CN IV Trochlear Nerve This small nerve is also involved in movements of the eye. It is the only cranial nerve that emerges from the dorsal surface of the brain stem rather than the lateral or ventral surfaces. CN V Trigeminal Nerve This large nerve carries sensory input from the face and motor commands for jaw muscles. CN VI Abducens Nerve This is the third cranial nerve involved in making eye movements. CN VII Facial Nerve This large cranial nerve is necessary for control of facial muscles as well as production of tears and saliva. In addition, it carries much of the sensory information from taste buds. CN VIII Vestibulo-Cochlear Nerve This nerve carries auditory and vestibular input from the inner ear to the brain stem. CN IX Glossopharyngeal Nerve Cranial nerves IX, X and XI are found close together along the sides of the medulla above the spinal cord. This nerve provides some control of a throat muscle and saliva production. It carries a bit of sensory input from the tongue, surface of the head in the region of the ear and from some taste buds. CN X Vagus Nerve Like CN IX, this nerve is involved in taste, touch, saliva production and control of muscles in the throat, but it is best known for supplying parasympathetic output to organs in the chest and upper abdomen. CN XI Accessory Nerve This unusual nerve arises at high cervical levels of the spinal cord, but enters the skull to run with CNs IX and X. It supplies motor outout to the sternomastoid and trapezius muscles. CN XII Hypoglossal Nerve This nerve supplies muscles within the tongue and other muscles that help move the tongue. Surface of the Brain Locate the following structures. diencephalon spinal cord medulla telencephalon pons cerebellum midbrain (mesencephalon) Gyri, Sulci and Lobes on the Surface of the Cerebral Hemispheres Locate the following landmarks on the surface of the cerebral hemispheres. lateral sulcus central sulcus parietal-occipital sulcus preoccipital notch Using these landmarks, define the borders of these five major regions of cerebral cortex. frontal lobe parietal lobe temporal lobe occipital lobe limbic lobe Pull the edges of the lateral sulcus aside and try to catch a glimpse of the cerebral cortex of the insula. Locate the following structures on the surface of the cerebral hemispheres. in the frontal lobe frontal gyri orbital gyri precentral gyrus precentral sulcus in the parietal lobe supramarginal gyrus postcentral gyrus angular gyrus postcentral sulcus superior and inferior parietal lobules in the temporal lobe superior temporal gyrus transverse gyri on superior surface of superior temporal gyrus superior temporal sulcus middle and inferior temporal gyri parahippocampal gyrus uncus in the occipital lobe calcarine sulcus Surface and Interior of the Brain Stem medulla (medulla oblongata) pyramid (a bundle of axons on anterior or ventral surface of medulla) inferior olive (bulge indicating the location of inferior olivary nucleus) obex gracile and cuneate tubercles facial colliculus pons white matter (axon bundles) within pons pontine nuclei midbrain (or mesencephalon) tectal area (“roof”) of the mesencephalon superior colliculus (“optic tectum”) also called the “corpora quadrigemina” inferior colliculus tegmentum of the mesencephalon cerebral peduncles (also called “crus cerebrii”) cerebellum lateral hemispheres of cerebellum vermis of cerebellum flocculonodular lobe of cerebellum tonsil of cerebellum middle cerebellar peduncle ( “penduncle” = another name for a large bundle of axons in brain) fourth ventricle approximate location of foramen of Luschka and Megendie (in fourth ventricle) cerebral aqueduct posterior commissure (at border of midbrain and diencephalon) Medial Surface of the Forebrain diencephalon medial surface of thalamus medial surface of hypothalamus pineal gland mammillary bodies (part of hypothalamus) infundibulum (“stalk”) of pituitary gland third ventricle septum pellucidum interventricular foramen lamina terminalis telencephalon cingulate gyrus cingulate sulcus corpus callosum (including splennium and genu) anterior commissure lateral ventricles basal ganglia or basal nuclei (in interior of cerebral hemispheres) Cerebrovascular System Two systems of arterial blood flow supply the CNS. - the Internal Carotid System - the Vertebrobasilar System Internal Carotid System Find the remaining part of the Internal Carotid Arteries at the base of the brain. Anterior Cerebral Artery Anterior Communicating Artery Middle Cerebral Artery Posterior Cerebral Artery Posterior Communicating Artery Vertebrobasilar System Look for the Vertebral Arteries on the brain stem. If they are not present, know where they are found. Several smaller arteries branch from the vertebral arteries. Anterior and Posterior Spinal Arteries and the Posterior Inferior Cerebellar Arteries. Blood from the vertebral arteries enters the basilar artery. Basilar Artery on the ventral surface of the brain stem. From the basilar artery, blood distributes to several smaller arteries: anterior communicating A Anterior Inferior Cerebellar Artery. Superior Cerebellar Artery. anterior cerebral A Posterior Communicating Artery middle cerebral A circle of Willis internal carotid A posterior communicating A posterior cerebral A superior cerebellar A anterior inferior cerebellar A posterior inferior cerebellar A vertebral A Circle of Willis A network of arteries in the vicinity of the optic chiasm forms an interconnecting network of vessels. Blood enters the Circle of Willis from both the Internal Carotid and Vertebrobasilar Systems. Blood Supply to the Cerebral Cortex Three major arteries - the Anterior, Middle and Posterior Cerebral Arteries supply the forebrain. Below are three views of the cerebral hemispheres. On the drawings, identify the regions supplied by these three major arteries. ACA anterior anterior ACA PCA MCA Lateral Surface of Right Cerebral Hemisphere PCA Medial Surface of Left Cerebral Hemisphere anterior ACA lateral MCA PCA Inferior Surface of Right Cerebral Hemisphere Cerebral Veins and Dural Sinuses Blood passes from deep and superficial cerebral veins into a series of spaces (“sinuses”) associated with the dura matter. Blood from the sinuses eventually enters the internal jugular veins.
