Nervous System Questions PDF

11/7/24 Questions 1. How many flowers were on the wall? FIVE 2....

11/7/24 Questions 1. How many flowers were on the wall? FIVE 2. Was the color BROWN listed? NO 3. What word was in the bottom right corner? DOOR 4. What color was below SHOES? BLUE 5. What flavor was to the left of CHOCOLATE? VANILLA 1 2 Learning Objectives 1. Enumerate and explain the gross anatomy of the brain by tabulating the parts, function and characteristics of the brain 2. Understand the structure of the cerebral cortex and its parts by tabulating its use, functions and clinical importance NEUROANATOMY 3. Indicate the functions of the midbrain by listing its clinical importance and significance By : Marc Anthony P. Cueto M.D. 4. Identify the cerebellar cortex by tabulating its structure, function, use and clinical importance 5. Identify the different spinal and cranial nerves of the peripheral nervous system 3 4 Part I : Neuron, Meninges and CSF 5 6 1  11/7/24 Neuron Neuron u Neurons are the conducting cells of u An axon is a long, hair-like extension of the nervous system. a nerve cell that carries a message to another nerve cell. u Typical neuron consists of a cell body, containing the nucleus and the u Dendrites are thread-like extensions of the surrounding cytoplasm; several short cytoplasm of a neuron that receive signals radiating processes (called dendrites); and from other neurons. Typically, as one long process (called the axon), which in multipolar neurons, dendrites branch into treelike processes, but in unipolar terminates in twiglike branches and may and bipolar neurons, dendrites resemble have branches projecting along its course. axons. u In many ways, the cell body is similar to u Neurons communicate with each other by other types of cells. It has a nucleus with at sending chemicals, called least one nucleolus and contains many of the neurotransmitters, across a tiny space, typical cytoplasmic organelles. called a synapse, between the axons and dendrites of adjacent neurons. 7 8 Meninges and Cerebrospinal Fluid u The brain and the spinal cord are delicate semisolid structures requiring u PROTECTION and u SUPPORT. u The brain is invested by : u three (3) membranes, u floated in a clear fluid, u and encased in a bony vault. u Three membranes surround the brain: 1. Dura mater or pachymenix – most external membrane; dense connective tissue envelope 2. Arachnoid – located between the dura mater and pia mater 3. Pia mater – innermost connective tissue membrane; thin, translucent membrane; adherent to the surface of the brain and spinal cord u The pia mater and arachnoid have a similar structure and collectively are called – Leptomeninges. 9 10 Dura Mater u The cranial dura consists of : 1. An outer periosteal layer adherent to the inner surface of the cranium, which is rich in Crista galli blood vessels and nerves. 2. An inner meningeal layer lined with flat cells u The meningeal layer gives rise to several septa that divide the cranial cavity into Sella turcica compartments. 1. Falx cerebri – largest; which extends in the midline from the crista galli to the internal occipital protuberance 2. Tentorium cerebelli – horizontal projection of the dura mater which separates and covers the cerebellum from the posterior part of the cerebral hemisphere 3. Falx cerebelli – small midline projection of the dura mater in the posterior cranial fossa. 4. Diaphragma sellae – small horizontal shelf of the dura mater that covers the hypophyseal fossa in the sella turcica of the sphenoid bone. There is an opening in the Internal occipital center which passes the infundibulum, which connects the pituitary gland with the base of the brain and accompanying blood vessels. protuberance 11 12 2  11/7/24 Dura Mater u The arterial supply to the dura mater travels in the outer periosteal layer of the dura and consists of : 1. Anterior meningeal arteries in the anterior cranial fossa 2. The middle and accessory meningeal arteries in the middle cranial fossa 3. The posterior meningeal artery and other meningeal branches in the posterior cranial fossa u All are small arteries EXCEPT for the middle meningeal artery, which is much larger and supplies the greatest part of the dura. 13 14 Dura Mater u The anterior meningeal arteries arteries are branches of the ethmoidal arteries. u The middle meningeal artery is a branch of the maxillary artery. It enters the middle cranial fossa through the foramen spinosum and divides into anterior and posterior branches: 1. the anterior branch passes in an almost vertical direction to reach the vertex of the skull, crossing the pterion during its course. 2. The posterior branch passes in a posterosuperior direction, supplying this region of the middle cranial fossa. 15 16 Dura Mater u The accesory meningeal artery is usually a small branch of the maxillary artery that enters the middle cranial fossa through the foramen ovale and supplies areas medial to this foramen. u The posterior meningeal artery, and other meningeal branches supplying the dura mater in the posterior cranial fossa come from several sources: 1. The posterior meningeal artery, the terminal branch of the ascending pharyngeal artery, enters the posterior cranial fossa through the jugular foramen. 2. A meningeal branch from the ascending pharyngeal artery enters the posterior cranial fossa through the hypoglossal canal. 3. Meningeal branches from the occipital artery enter the posterior cranial fossa through the jugular foramen and the mastoid foramen 4. A meningeal branch from the vertebral artery arises as the vertebral artery enters the posterior cranial fossa through the foramen magnum. 17 18 3  11/7/24 Accessory meningeal artery Maxillary artery External carotid artery 19 20 Dura Mater u Innervation Ø Innervation of the dura mater is by small meningeal branches of all three divisions of the Trigeminal nerve (V1, V2, V3) and the Vagus nerve (X) and the first, second and sometimes, third cervical nerves. Ø In the anterior cranial fossa, meningeal branches from the ethmoidal nerves, which are branches of the ophthalmic nerve (V1), supply the floor and the anterior part of the flax cerebri. Ø A meningeal branch of the ophthalmic nerve (V1), turns and runs posteriorly, supplying the tentorium cerebelli and the posterior part of the falx cerebri. Ø The middle cranial fossa is supplied medially by meningeal branches from the maxillary nerve (V2) and laterally, along the distribution of the middle meningeal artery, by meningeal branches from the mandibular nerve (V3). Ø The posterior cranial fossa is supplied by meningeal branches from the first, second and sometimes third cervical nerves, which enter the fossa through the foramen magnum, the hypoglossal canal and the jugular foramen. 21 22 Arachnoid mater u It is a thin, avascular membrane that lines, but it is not adherent to, the inner surface of the dura mater. u From its inner surface thin processes or trabeculae extend downward, cross the subarachnoid space, become continuous with the pia mater. u The arachnoid does not enter the grooves or fissures of the brain, except for the longitudinal fissure between the two cerebral hemispheres. 23 24 4  11/7/24 Pia Mater Arrangement of meninges and u It is a thin delicate spaces membrane that closely invests the surface of u There is a unique arrangement of meninges coupled with real and potential spaces within the cranial cavity. the brain. u A potential space is related to the dura mater, while a real space exists u It follows the contour between the arachnoid mater and the pia mater. of the brain, entering u Extradural space the grooves and Ø The potential space between dura mater and bone is the extradural space. fissures on its surface Normally, the outer or periosteal layer of dura mater is firmly attached to the and is closely applied Ø bones surrounding the cranial cavity. to the roots of the Ø This potential space between dura and bone CAN BECOME a fluid filled actual cranial nerves at their space when a traumatic event results in vascular hemorrhage. origins. Ø Bleeding into the extradural space due to rupture of a meningeal artery or atorn dural venous sinus results in an extradural hematoma. 25 26 Arrangement of meninges and spaces u Subarachnoid space Ø Deep to the arachnoid mater is the ONLY normally occurring fluid filled space associated with the meninges. Ø It occurs because the arachnoid mater clings to the inner surface of the dura mater and does not follow the contour of the brain, while the pia mater, being against the surface of the brain, closely follows the grooves and fissures on the surface of the brain. Ø The narrow subarachnoid space is therefore created between these two membranes. Ø The subarachnoid space surrounds the brain and spinal cord and in certain locations it enlarges into expanded areas called subarachnoid cisterns. It contains cerebrospinal fluid (CSF) and blood vessels. 27 28 Cerebrospinal Fluid u It is a clear, colorless liquid containing small amounts of protein, glucose and potassium and relatively large amounts of sodium chloride. u There are no substances normally found in CSF that are not also found in blood plasma. u There is no cellular component in CSF, although 1 to 5 cells per cubic millimeter may be considered to be within normal limits in any CSF sample. u It serves to support and cushion the CNS against trauma. u The buoyancy of CSF is indicated by the fact that a brain weighing 1500g in air weighs only 50g when immersed in CSF. u This bouyancy serves to reduce the momentum and acceleration of the brain when the cranium is suddenly displaced , thereby reducing concussive damage. 29 30 5  11/7/24 Circulation of Cerebrospinal Fluid Cerebrospinal Fluid (CSF) Left and Right Lateral Ventricles Interventricular Foramen (Foramen u The CSF has been regarded as an ultra filtrate of the blood plasma because of Monro) of their resemblance, except for differences in protein concentration. Third Ventricle Cerebral u Approximately 70% of the CSF is secreted by the choroid plexus located in Aqueduct the lateral ventricles and in the roof of the third and fourth ventricles. (Aqueduct of Sylvius) u The remaining 30% of the CSF is derived from metabolic water production. Fourth Ventricle LateralAperture Lateral Aperture :: Foramenof Foramen of Lushka Lushka u The choroid plexus is a villous structure extending from the ventricular Medial Aperture: Medial Aperture: surface into the CSF. This plexus consists of a single layer of cuboidal Foramen Foramen of Magendie of Subarachnoid space Magendie epithelium with basal infoldings resting on a basement menbrane enclosing an extensive capillary network embedded in a connective tissue stroma. u The CSF returns to the venous system through arachnoid villi. These project Arachnoid villi as clumps or arachnoid granulations into the superior sagittal sinus and its lateral extensions the lateral lacunae. Superior Sagittal Sinus 31 32 Clinical Correlation 33 34 Lumbar Tap/Puncture Hydrocephalus Ø Itis the abnormal dilatation of the cerebral ventricular system, which is due to either : (1) obstruction to the flow of CSF (2) overproduction of CSF (3) failure of reabsorption of CSF 35 36 6  11/7/24 Hydrocephalus u In adults the commonest cause of hydrocephalus is an interruption of the normal CSF absorption through the arachnoid granulations. u This occurs when blood enters the subarachnoid space after subarachnoid hemorrhage, passes over the brain, and interferes with normal CSF absorption. u In children, hydrocephalus is always dramatic in its later stages. u The hydrocephalus increases the size and dimensions of the ventricle and as a result the brain enlarges. u Because the skull sutures are not fused, the head expands. u Cranial enlargement in utero may make vaginal delivery impossible, and delivery has to be by Caesarean section. u Treatment : placement of a shunt 37 38 39 40 Brain u It is a component of the central nervous system. u During development the brain can be divided into five (5) continuous parts. From rostral to caudal they are: 1. Telencephalon (cerebrum) It becomes the large cerebral hemispheres The surface of these hemispheres consists of elevations (gyri) and depressions (sulci) and the hemispheres partially separated by a deep longitudinal fissure. The cerebrum fills the area of the skull above the tentorium cerebelli and is subdivided into lobes based on position. Part II : The Brain 2. Dienchephalon Hidden from view in the adult brain by the cerebral hemispheres Consists of: 1. Thalamus 2. Hypothalamus 3. Other related structures Considered as the most rostral part of the brainstem 41 42 7  11/7/24 Brain 3. Mesencephalon (midbrain) First part of the brainstem seen when an intact adult brain is examined Located at the junction between and in both the middle and posterior cranial fossae. 4. Metencephalon Gives rise to the cerebellum and the pons 5. Myelencephalon (medulla oblongata) Caudal most part of the brainstem Ends at the foramen magnum or the uppemost rootlets of the first cervical nerve and to which cranial nerves VI to XII are attached. 43 44 Cerebral Hemispheres u The paired cerebral hemispheres are mirror image duplicates consisting of a highly convoluted gray cortex (pallium), an underlying white matter, and a collection of deep neuronal masses, known as the basal ganglia. u They are partially separated from each other by the longitudinal fissure. u This fissure contains in situ contains the falx cerebri. u In frontal and occipital regions the separation of the hemispheres is complete, but in the central region the fissure extends only to fibers of the broad interhemispheric commisure called the corpus callosum. 45 46 Cerebral Hemispheres u Each cerebral hemisphere is subdivided into lobes by various sulci. u The major lobes of the brain are named for the overlying bones of the skull. u On the basis of the more constant sulci and gyri, the cerebrum is divided into six so called lobes: 1. Frontal 2. Temporal 3. Parietal 4. Occipital 5. Insular 6. Limbic 47 48 8  11/7/24 Cerebral Hemispheres Cerebral Hemispheres Ø Frontal lobe u Lateral surface Largest of all the lobes of the Ø The two most important sulci for brain, comprises about one-thrid topographical orientation on the of the hemispheric surface. lateral side of the hemisphere are: 1. Lateral sulcus – begins inferiorly in Extends rostrally from the the Sylvian fossa and extends central sulcus to the frontal obliquely posterior, separating the pole; its inferior boundary is the frontal and temporal lobes. lateral sulcus. Caudally this sulcus separates It is where the primary motor portions of the parietal and temporal lobes. area is located where all parts of the body are represented in a 2. Central sulcus – prominent sulcus distorted but topographical running from the superior margin of manner also called the the hemisphere downward and forward toward the lateral sulcus. HOMONCULUS (little person). 49 50 Cerebral Hemispheres Ø Parietal lobe Boundaries of the parietal lobe are less precise, except for its anterior border on the lateral convexity formed by the central sulcus. It where the primary somesthetic area, the cortical region where tactile and kinesthetic sense from superficial and deep receptors are somatotopically represented. Ø Temporal lobe Lies inferior to the lateral sulcus. It is where the primary auditory and olfactory cortex is located Ø Occipital lobe Rests on the tentorium cerebelli and constitutes the caudal pole of the hemisphere. It is where the primary visual cortex is located. 51 52 Cerebral Hemispheres Cerebral hemispheres u Medial surface u Lateral ventricles Ø The most prominent structure on the medial surface is the Ø Ependymal lined cavities of the cerebral massive interhemispheric commissure called the corpus hemispheres callosum. Ø Contains CSF and conform to the general shape Ø Corpus callosum of the hemispheres Composed of myelinated fibers, reciprocally interconnects Ø Portions of the lateral ventricles contain neraly all cortical regions of the two hemispheres. choroid plexus, which is formed by the Forms the floor of the longitudinal fissure, as well as the roof of the lateral ventricle invagination of the ependymal roof plate into the ventricular cavities. Plays an important role in the interhemispheric transfer of learned discriminations, sensory experience and memory. 53 54 9  11/7/24 Corpus callosum Lateral ventricles Thrid ventricle 4th ventricle 55 56 Cerebellum u Also known as “little brain” u It is a structure that is located at the back of the brain, underlying the occipital and temporal lobes of the cerebral cortex. u Although the cerebellum accounts for approximately 10% of the brain’s volume, it contains over 50% of the total number of neurons in the brain. u Historically, the cerebellum has been considered a motor structure, because cerebellar damage leads to impairments in motor control and posture and because the majority of the cerebellum’s outputs are to parts of the motor system. u Motor commands are not initiated in the cerebellum; rather, the cerebellum modifies the motor commands of the descending pathways to make movements more adaptive and accurate. 57 58 Cerebellum : Functions Cerebellum : Functions u The cerebellum is involved in the following functions: u Motor learning. u Maintenance of balance and posture. u The cerebellum is important for motor learning. u The cerebellum is important for making postural adjustments in order to maintain balance. u The cerebellum plays a major role in adapting and fine-tuning motor u Through its input from vestibular receptors and proprioceptors, it modulates programs to make accurate movements through a trial-and-error process commands to motor neurons to compensate for shifts in body position or changes in (e.g., learning to hit a baseball). load upon muscles. u Patients with cerebellar damage suffer from balance disorders, and they often u Cognitive functions. develop stereotyped postural strategies to compensate for this problem (e.g., a u Although the cerebellum is most understood in terms of its contributions to wide-based stance). motor control, it is also involved in certain cognitive functions, such as u Coordination of voluntary movements. language. u Most movements are composed of a number of different muscle groups acting u Thus, like the basal ganglia, the cerebellum is historically considered as part together in a temporally coordinated fashion. of the motor system, but its functions extend beyond motor control in ways u One major function of the cerebellum is to coordinate the timing and force of these different muscle groups to produce fluid limb or body movements. that are not yet well understood. 59 60 10  11/7/24 Cerebellum : Anatomy u The cerebellum consists of two major parts. u The cerebellar deep nuclei (or cerebellar nuclei) are the sole output structures of the cerebellum. u These nuclei are encased by a highly convoluted sheet of tissue called the cerebellar cortex, which contains almost all of the neurons in the cerebellum. 61 62 Cerebellum : Anatomy Vermis u Divisions of the cerebellum u Two major fissures running mediolaterally divide the cerebellar cortex into three primary lobes. u The posterolateral fissure separates the flocculonodular lobe from the corpus cerebelli, and the primary fissure separates the corpus cerebelli into a posterior lobe and an anterior lobe. u The cerebellum is also divided sagittally into three zones that run from medial to lateral. u The vermis (from the Latin word for worm) is located along the midsagittal plane of the cerebellum. u Directly lateral to the vermis is the intermediate zone. u Finally, the lateral hemispheres are located lateral Posterolateral to the intermediate zone (there are no clear fissure morphological borders between the intermediate zone and the lateral hemisphere that are visible from a gross specimen). 63 64 Cerebellar Function Testing Cerebellar Function Testing 65 66 11  11/7/24 Brainstem Brainstem u the posterior part of the brain, adjoining and structurally u Though small, this is an extremely important part of the brain as continuous with the spinal cord. In humans it is usually the nerve connections of the motor and sensory systems from described as including the medulla the main part of the brain to the rest of the body pass through oblongata (myelencephalon), pons (part of the brainstem. metencephalon), and midbrain (mesencephalon). u This includes the corticospinal tract (motor), the posterior u The brainstem provides the main motor and sensory column-medial lemniscus pathway (fine touch, vibratio innervation to the face and neck via the cranial nerves. sensation, and proprioception), and the spinothalamic u Of the twelve pairs of cranial nerves, ten pairs come from tract (pain, temperature, itch, and crude touch). the brainstem. The other two pairs come from the u The brainstem also plays an important role in the regulation cerebrum (CN I & II) of cardiac and respiratory function. It also regulates the central nervous system, and is pivotal in maintaining consciousness and regulating the sleep cycle. The brainstem has many basic functions including heart rate, breathing, sleeping, and eating. 67 68 Brainstem u Midbrain Ø The midbrain is divided into three parts. Ø The first is the tectum, (Latin:roof), which forms the ceiling. Ø The second part is the tegmentum which forms the floor of the midbrain, and is ventral to the cerebral aqueduct. Ø The third part, the ventral tegmentum is composed of paired cerebral peduncles. These transmit axons of upper motor neurons. u Pons Ø The pons lies between the medulla oblongata and the midbrain. Ø It contains tracts that carry signals from the cerebrum to the medulla and to the cerebellum and also tracts that carry sensory signals to the thalamus. Ø The pons is connected to the cerebellum by the cerebellar peduncles. u Medulla Ø The medulla oblongata often just referred to as the medulla, is the lower half of the brainstem continuous with the spinal cord. Its upper part is continuous with the pons. Ø The medulla contains the cardiac, respiratory, vomiting and vasomotor centres dealing with heart rate, breathing and blood pressure. 69 70 Midbrain 71 72 12  11/7/24 Medulla 73 74 Cranial Nerves u The12 pairs of cranial nerves are part of the peripheral nervous system (PNS) and pass through the foramina or fissures in the cranial cavity. u 10 pairs come from the brainstem Part III : Cranial Nerves u2 pairs come from cerebrum 75 76 OLFACTORY NERVE Cranial Nerve I 77 78 13  11/7/24 I. Olfactory Nerve u The olfactory nerve [I] carries special afferent (SA) fibers for the sense of smell. Its sensory neurons have: peripheral processes that act as receptors in the nasal mucosa, and central processes that return information to the brain. u The receptors are in the roof and upper parts of the nasal cavity, and the central processes, after joining into small bundles, enter the cranial cavity by passing through the cribriform plate of the ethmoid bone. u They terminate by synapsing with secondary neurons in the olfactory bulbs. u Damage causes impaired sense of smell (Anosmia) 79 80 I. Olfactory Nerve v Component: Sensory v Function: Smell v Origin: Olfactory receptor nerve cells in OPTIC NERVE the olfactory mucous membrane. Cranial Nerve II v Opening to the Skull: Openings in cribriform plate of ethmoid 81 82 II. Optic Nerve II. Optic Nerve u The optic nerve [II] carries SA fibers for vision. q Component: Sensory u These fibers return information to the brain from photoreceptors in the retina. u Neuronal processes leave the retinal receptors, join into small bundles, and are carried by the optic nerves to other q Function: Vision components of the visual system in the brain. u The optic nerves enter the cranial cavity q Origin: Back of the eyeball through the optic canals. u Blindness/visual field abnormalities, loss of pupillary constriction q Opening to the Skull: Optic Canal 83 84 14  11/7/24 Optic canal Optic nerve OCULOMOTOR NERVE Cranial Nerve III 85 86 III. Oculomotor Nerve III. Oculomotor Nerve u The oculomotor nerve [III] carries u In the orbit, the GSE fibers in the two types of fibers: oculomotor nerve innervate levator u General somatic efferent (GSE) palpebrae superioris, superior rectus, fibers innervate most of the extra- ocular muscles. inferior rectus, medial rectus, and inferior oblique muscles. u General visceral efferent (GVE) fibers are part of the u The GVE fibers are preganglionic parasympathetic part of the autonomic division of the PNS. parasympathetic fibers that synapse in the u The oculomotor nerve [III] leaves the ciliary ganglion and ultimately innervate the anterior surface of the brainstem sphincter pupillae muscle, responsible for between the midbrain and the pons. pupillary constriction, and the ciliary u It enters the anterior edge of the muscles, responsible for accommodation of tentorium cerebelli, continues in an the lens for near vision. anterior direction in the lateral wall of the cavernous sinus, and leaves u Dilated pupil, ptosis, loss of normal the cranial cavity through the superior orbital fissure. pupillary reflex, eye moves down inferiorly and laterally (down and out) 87 88 89 90 15  11/7/24 III. Oculomotor Nerve § Component: Motor § Function: § Raises upper eyelid § Turns eyeball upward, downward and medially § Constricts pupil § Accommodates the eye § Origin: Anterior surface of the midbrain § Opening to the Skull: Superior orbital fissure 91 92 Superior orbital fissure TROCHLEAR NERVE Oculomotor Cranial Nerve IV nerve 93 94 IV. Trochlear Nerve IV. Trochlear Nerve u The trochlear nerve [IV] is a cranial nerve that carries GSE fibers to innervate the superior oblique ü Component: Motor muscle, an extra-ocular muscle in the orbit. u It arises in the midbrain and is the only cranial nerve to exit from the ü Function: Assisting in turning eyeball posterior surface of the brainstem. downward and laterally u After curving around the midbrain, it enters the inferior surface of the free edge of the tentorium cerebelli, continues in an anterior direction in the lateral wall of the cavernous sinus, and enters the orbit through ü Origin: Posterior surface of the midbrain the superior orbital fissure. u Inability to look inferiorly when the eye is adducted (down and in). ü Opening to the Skull: Superior orbital fissure 95 96 16  11/7/24 IV. Trochlear Nerve ü Component: Motor ü Function: Assisting in turning eyeball downward and laterally ü Origin: Posterior surface of the midbrain ü Opening to the Skull: Superior orbital fissure 97 98 Superior orbital fissure TRIGEMINAL NERVE uCranial Nerve V Trochlear nerve 99 100 V. Trigeminal Nerve u The trigeminal nerve [V] is the major general sensory V. Trigeminal Nerve nerve of the head and also innervates muscles that move the lower jaw. u In the middle cranial fossa the sensory root expands into the trigeminal ganglion, which u It carries general somatic afferent (GSA) and branchial contains cell bodies for the sensory neurons in efferent (BE) fibers: the trigeminal nerve and is comparable to a spinal ganglion. u The GSA fibers provide sensory input from: u The ganglion is in a depression (the trigeminal a. the face, depression) on the anterior surface of the petrous b. anterior one-half of the scalp, part of the temporal bone, in a dural cave (the trigeminal cave). c. mucous membranes of the oral and nasal cavities and the paranasal sinuses, the u The motor root is below and completely separate from the sensory root at this point. d. nasopharynx, u Arising from the anterior border of the trigeminal ganglion are the three terminal divisions of the e. part of the ear and external acoustic meatus, part of trigeminal nerve, which in descending order are: the tympanic membrane, the ophthalmic nerve (ophthalmic division [V1]). f. the orbital contents and conjunctiva, and the the maxillary nerve (maxillary division [V2]), and e. dura mater in the anterior and middle cranial fossae. the mandibular nerve (mandibular division [V3]). u The BE fibers innervate the muscles of mastication; the tensor tympani, tensor veli palatini, and mylohyoid muscles; and the anterior belly of the digastric muscle. 101 102 17  11/7/24 V1. Ophthalmic Nerve V1. Ophthalmic Nerve v Component: Sensory v Component: Sensory v Function: v Function: It supplies the sensory fibers to the: v Cornea v Cornea v Skin of forehead v Skin of forehead v Scalp v Scalp v Eyelids and nose v Eyelids and nose v Mucous membranes of paranasal sinuses v Mucous membranes of paranasal sinuses and nasal cavity and nasal cavity v Origin: Anterior aspect of the pons v Origin: Anterior aspect of the pons v Opening to the Skull: Superior orbital fissure v Opening to the Skull: Superior orbital fissure 103 104 Superior orbital fissure V2. Maxillary Nerve o Component: Sensory o Function: It supplies sensory fibers to the: o Skin of the face over maxilla o Teeth of the upper jaw o Mucous membrane of the nose, the maxillary sinus and palate Ophthalmic nerve (V1) o Origin: Anterior aspect of the pons o Opening to the Skull: Foramen rotundum 105 106 Foramen rotundum V3. Mandibular Nerve o Component: Mixed o Function (Motor) It supplies motor fibers to the: o Muscles of mastication o Mylohyoid o Anterior belly of digastric o Tensor veli palatine Maxillary nerve o Tensor tympani (V2) o Origin: Anterior aspect of the pons o Opening to the Skull: Foramen ovale 107 108 18  11/7/24 Foramen ovale V3. Mandibular Nerve Component: Mixed Function (Sensory): It supplies sensory fibers to the: Skin of cheek Skin over mandible and side of head Teeth of lower jaw and TMJ Mucous membrane of mouth and anterior part of tongue Mandibular Origin: Anterior aspect of the pons nerve (V3) Opening to the Skull: Foramen ovale 109 110 Trigeminal Nerve V u Loss of sensation and pain in the region supplied by the three divisions of the nerve over the face; loss of motor function of the muscles of mastication on the side of the lesion ABDUCENT NERVE Cranial Nerve VI 111 112 VI. Abducens Nerve VI. Abducent Nerve u The abducent nerve [VI] carries GSE fibers to innervate the lateral rectus muscle in the orbit. ü Component: Motor u It arises from the brainstem between the pons and medulla and passes forward, piercing the dura covering ü Function: Lateral rectus muscle : turns eyeball the clivus. laterally u Continuing upward in a dural canal, it crosses the superior edge of the petrous part of the temporal bone, enters and crosses the cavernous sinus just inferolateral to the internal carotid artery, and enters ü Origin: Medulla oblongata the orbit through the superior orbital fissure. u Inability of lateral eye movement ü Opening to the Skull: Superior orbital fissure 113 114 19  11/7/24 VI. Abducent Nerve ü Component: Motor ü Function: Lateral rectus muscle turns eyeball laterally ü Origin: Medulla oblongata ü Opening to the Skull: Superior orbital fissure 115 116 Superior orbital fissure Abducent nerve 117 118 VII. Facial Nerve u The facial nerve [VII] carries GSA, SA, GVE, and BE fibers: The GSA fibers provide sensory input from part of the external acoustic meatus and deeper parts of the auricle. The SA fibers are for taste from the anterior two-thirds of the tongue. The GVE fibers are part of the FACIAL NERVE parasympathetic part of the autonomic division of the PNS and : a. stimulate secretomotor activity in the Cranial Nerve VII lacrimal gland, b. submandibular and sublingual salivary glands, and c. glands in the mucous membranes of the nasal cavity, and hard and soft palates. 119 120 20  11/7/24 VII. Facial Nerve VII. Facial Nerve The BE fibers innervate : u The facial nerve [VII] attaches to the lateral surface of the brainstem, between the pons the muscles of the face (muscles of facial and medulla oblongata. expression) and scalp derived from the second pharyngeal arch, and u It consists of a large motor root and a smaller sensory root (the intermediate nerve): the stapedius muscle, The intermediate nerve contains the the posterior belly of the digastric muscle, SA fibers for taste, the parasympathetic GVE the stylohyoid muscle. fibers, and the GSA fibers. The larger motor root contains the BE fibers. u The motor and sensory roots cross the posterior cranial fossa and leave the cranial cavity through the internal acoustic meatus. u After entering the facial canal in the petrous part of the temporal bone, the two roots fuse and form the facial nerve [VII]. 121 122 VII. Facial Nerve VII. Facial Nerve q Component: Mixed q Origin : Medulla Oblongata q Function: Motor : q Opening in the skull : Internal acoustic meatus It supplies motor fibers to the: & Stylomastoid foramen muscles of the face and scalp Stapedius muscle Posterior belly of digastric Stylohyoid muscles q Function: Sensory Taste from Anterior 2/3 of tongue, from the floor of the mouth and palate. 123 124 Internal acoustic VII. Facial Nerve meatus q Function: Secretomotor Submandibular and sublingual salivary glands Lacrimal gland Glands of nose and palate q Origin: Medulla oblongata q Opening to the Skull: internal acoustic Stylomastoid foramen meatus, facial canal, stylomastoid foramen 125 126 21  11/7/24 Facial Nerve VII u Damage produces Facial nerve palsy (Bell’s palsy). Facial nerve u Paralysis of facial muscles u Abnormal taste sensation from the anterior two-thirds of the tongue and dry conjunctivae u Paralysis of contralateral facial muscles below the eye 127 128 VESTIBULOCOCHLEAR NERVE Cranial Nerve VIII 129 130 VIII. Vestibulocochlear Nerve VIII. Vestibulocochlear Nerve u The vestibulocochlear nerve [VIII] carries SA fibers for hearing and balance, and consists of two divisions: o Component: Sensory a vestibular component for balance, and a cochlear component for hearing. o Function: u The vestibulocochlear nerve [VIII] attaches to o Vestibular - Saculae, saccule, semicircular the lateral surface of the brainstem, between the pons and medulla, after emerging from the canals – position of head internal acoustic meatus and crossing the posterior cranial fossa. o Cochlear – Organ of Corti - hearing u The two divisions combine into the single nerve seen in the posterior cranial fossa within the substance of the petrous part of the temporal bone. o Origin: Medulla oblongata u Damage produces deafness, dizziness, nausea, loss of balance and nystagmus. o Opening to the Skull: Internal acoustic meatus 131 132 22  11/7/24 VIII. Vestibulocochlear Nerve Internal acoustic meatus o Component: Sensory o Function: o Vestibular – Position and movement of the head (Saculae, saccule, semicircular canals – position of head) o Cochlear – Hearing (Organ of Corti) o Origin: Medulla oblongata o Opening to the Skull: Internal acoustic meatus Vestibulocochlear nerve 133 134 IX. Glossopharyngeal Nerve u The glossopharyngeal nerve [IX] carries GVA, GSA, SA, GVE, and BE fibers: u The GVA fibers provide sensory input from the carotid body (chemoreceptor for O2) and carotid sinus GLOSSOPHARYNGEAL (baroreceptor). u The GSA fibers provide sensory input from the posterior one-third of the tongue, palatine tonsils, oropharynx, and mucosa of the middle ear, NERVE u pharyngotympanic tube, and mastoid air cells. The SA fibers are for taste from the posterior one- third of the tongue. Cranial Nerve IX u The GVE fibers are part of the parasympathetic part of the autonomic division of the PNS and stimulate secretomotor activity in the parotid salivary gland. u The BE fibers innervate the muscle derived from the third pharyngeal arch (the stylopharyngeus muscle). 135 136 IX. Glossopharyngeal Nerve IX. Glossopharyngeal Nerve – Tympanic Nerve u The glossopharyngeal nerve [IX] arises as u Branching from the glossopharyngeal nerve several rootlets on the anterolateral surface [IX] either within or immediately outside the of the upper medulla oblongata. jugular foramen is the tympanic nerve. u The rootlets cross the posterior cranial fossa u This branch reenters the temporal bone, and enter the jugular foramen. enters the middle ear cavity, and participates u Within the jugular foramen, and before in the formation of the tympanic plexus. exiting from it, the rootlets merge to form u Within the middle ear cavity it provides the glossopharyngeal nerve. sensory innervation to the mucosa of the u Damage results in loss of bitter and sour taste cavity, pharyngotympanic tube, and mastoid and impaired swallowing, blood pressure air cells. anomalies (with CN X). u Loss of taste to the posterior one-third of the tongue and sensation of the soft palate 137 138 23  11/7/24 IX. Glossopharyngeal Nerve IX. Glossopharyngeal Nerve ü Component: Mixed ü Function: Motor It supplies motor fibers to : ü Origin: Medulla oblongata Stylopharyngeus muscle – assists swallowing ü Function: Sensory It supplies motor fibers to: ü Opening to the Skull: Jugular foramen General sensation and taste from post. ½ of the tongue and pharynx Carotis sinus and carotid body ü Function: Secretomotor Parotid gland 139 140 Jugular foramen IX. Glossopharyngeal Nerve ü Origin: Medulla oblongata ü Opening to the Skull: Jugular foramen 141 142 X. Vagus Nerve u The vagus nerve [X] carries GSA, GVA, SA, GVE, and BE fibers: The GSA fibers provide sensory input from the larynx, laryngopharynx, deeper parts of the auricle, part of the external acoustic meatus, and the dura mater in the posterior cranial fossa. The GVA fibers provide sensory input from the VAGUS NERVE aortic body chemoreceptors and aortic arch baroreceptors, and the esophagus, bronchi, lungs, heart, and abdominal viscera in the foregut and midgut. Cranial Nerve X The SA fibers are for taste around the epiglottis and pharynx. 143 144 24  11/7/24 X. Vagus Nerve X. Vagus Nerve u The vagus nerve arises as a group of rootlets on The GVE fibers are part of the parasympathetic the anterolateral surface of the medulla part of the autonomic division of the PNS and oblongata just inferior to the rootlets arising to stimulate smooth muscle and glands in the form the glossopharyngeal nerve [IX]. pharynx, larynx, thoracic viscera, and abdominal u The rootlets cross the posterior cranial fossa viscera of the foregut and midgut. and enter the jugular foramen. The BE fibers innervate one muscle of the tongue (palatoglossus), the muscles of the soft u Damage causes hoarseness or loss of voice, palate (except the tensor veli palatini), pharynx impaired swallowing, GI dysfunction, blood (except the stylopharyngeus), and larynx. pressure anomalies (with CN IX), fatal if both are cut u Soft palate deviation with deviation of the uvula to the normal side. 145 146 X. Vagus Nerve X. Vagus Nerve ü Component: Mixed ü Component: Motor ü Function: ü Function: ü Heart and great thoracic blood vessels ü Heart and great thoracic blood vessels ü Larynx, trachea, bronchi and lungs ü Larynx, trachea, bronchi and lungs ü Alimentary tract from pharynx to splenic flexure of ü Alimentary tract from pharynx to splenic flexure of colon colon ü Liver, kidney, pancreas ü Liver, kidney, pancreas ü Origin: Medulla oblongata ü Origin: Medulla oblongata ü Opening to the Skull: Jugular foramen ü Opening to the Skull: Jugular foramen 147 148 Jugular foramen ACCESSORY NERVE Cranial Nerve XI Vagus nerve 149 150 25  11/7/24 XI. Accessory Nerve/Spinal Accessory Nerve XI. Accessory Nerve/Spinal Accessory Nerve u The accessory nerve [XI] is a cranial u The accessory nerve [XI] continues nerve that carries BE fibers to innervate through the posterior cranial fossa and the sternocleidomastoid and trapezius exits through the jugular foramen. muscles. u It then descends in the neck to u It is a unique cranial nerve because its innervate the sternocleidomastoid and roots arise from motor neurons in the trapezius muscles from their deep upper five segments of the cervical surfaces. spinal cord. u Damage causes impaired head, neck, u These fibers leave the lateral surface of shoulder movement the spinal cord and, joining together as u Paralysis of sternocleidomastoid and they ascend, enter the cranial cavity trapezius muscles through the foramen magnum. 151 152 XI. Accessory Nerve XI. Accessory Nerve v Component: Motor v Function: v Origin: medulla oblongata v Cranial root : It supplies motor fibers to the: v Muscles of soft palate (except tensor veli v Opening to the Skull: Jugular foramen palatini) v Muscles pharynx (except styopharyngeus)