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14 The Brain and Cranial Nerves PowerPoint® Lecture Presentations prepared by Jason LaPres Lone Star College—North Harris © 2012 Pearson Education, Inc. An Introduction to the Brain and Cranial Nerves • Learning Outcomes • 14-1 Name the major brain regions, vesicles, and ventricles, and describe the locations and functions of each. • 14-2 Explain how the brain is protected and supported, and discuss the formation, circulation, and function of cerebrospinal fluid. • 14-3 Describe the anatomical differences between the medulla oblongata and the spinal cord, and identify the main components and functions of the medulla oblongata. © 2012 Pearson Education, Inc. An Introduction to the Brain and Cranial Nerves • Learning Outcomes • 14-4 List the main components of the pons, and specify the functions of each. • 14-5 List the main components of the cerebellum, and specify the functions of each. • 14-6 List the main components of the midbrain, and specify the functions of each. • 14-7 List the main components of the diencephalon, and specify the functions of each. © 2012 Pearson Education, Inc. An Introduction to the Brain and Cranial Nerves • Learning Outcomes • 14-8 Identify the main components of the limbic system, and specify the locations and functions of each. • 14-9 Identify the major anatomical subdivisions and functions of the cerebrum, and discuss the origin and significance of the major types of brain waves seen in an electroencephalogram. • 14-10 Describe representative examples of cranial reflexes that produce somatic responses or visceral responses to specific stimuli. © 2012 Pearson Education, Inc. Synapse Pre-synaptic neuron Synaptic cleft Post-synaptic neuron Glutam ate AMP AR © 2012 Pearson Education, Inc. NMD AR • In the pre-synaptic neuron, an electrical signal comes in, opens up to voltage-gated channels, and signals the vesicles containing neurotransmitters (chemical signal) to be released into the synaptic cleft. • Receptors on the post-synaptic neuron bind to the neurotransmitter signaling it to open its gate and let ions flow through. • The flow of ions will generate a current that changes the resting membrane potential. If the membrane potential passes the threshold, then an action potential is produced. • The action potential is then propagated to the next neuron, and the communication continues from neuron to neuron. Picture adapted from MRC Centre for Synaptic Plasticity An Introduction to the Brain and Cranial Nerves • The Adult Human Brain • Ranges from 750 cc to 2100 cc • Contains almost 97% of the body’s neural tissue • Average weight about 1.4 kg (3 lb) © 2012 Pearson Education, Inc. Brain Summary • Important component of the CNS. • Site for coordination and integration of sensations, emotions, memory, and behavior. • Divided into 6 regions (cerebrum, cerebellum, diencephalon, mesencephalon, pons, and medulla oblongata) • Protected by 3 connective tissue meninges: dura mater, arachnoid, and the pia mater—just like the spinal cord. • Large blood vessels called dural sinuses can be found between 2 layers of dura mater. • The subarachnoid space is filled with CSF • Cranial nerves emerge from various parts of the brain • The brain contains both gray matter and white matter • Gray = interneurons and neuroglia • White = fiber tracts © 2012 Pearson Education, Inc. 14-1 The Brain • Six Regions of the Brain 1. Cerebrum 2. Cerebellum 3. Diencephalon 4. Mesencephalon (midbrain) 5. Pons 6. Medulla oblongata © 2012 Pearson Education, Inc. Brain Stem 14-1 The Brain • Cerebrum • Largest part of brain • Controls higher mental functions • Divided into left and right cerebral hemispheres • Surface layer of gray matter (neural cortex) © 2012 Pearson Education, Inc. 14-1 The Brain • Cerebrum • Neural cortex • Also called cerebral cortex • Folded surface increases surface area • Elevated ridges (gyri) • Shallow depressions (sulci) • Deep grooves (fissures) © 2012 Pearson Education, Inc. 14-1 The Brain • Cerebellum • Second largest part of brain • Coordinates repetitive body movements • Two hemispheres • Covered with cerebellar cortex © 2012 Pearson Education, Inc. Figure 14-1 An Introduction to Brain Structures and Functions Left cerebral hemisphere Gyri Sulci CEREBRUM • Conscious thought processes, intellectual functions • Memory storage and processing • Conscious and subconscious regulation of skeletal muscle contractions Fissures CEREBELLUM Spinal cord © 2012 Pearson Education, Inc. • Coordinates complex somatic motor patterns • Adjusts output of other somatic motor centers in brain and spinal cord 14-1 The Brain • Diencephalon • Located under cerebrum and cerebellum • Links cerebrum with brain stem • Three divisions of the diencephalon 1. Epithalamus 2. thalamus 3. Hypothalamus © 2012 Pearson Education, Inc. 14-1 The Brain • Diencephalon • Thalamus • Relays and processes sensory information • Hypothalamus • Hormone production • Emotion • Autonomic function © 2012 Pearson Education, Inc. 14-1 The Brain • Diencephalon • Pituitary gland • Major endocrine gland • Connected to hypothalamus © 2012 Pearson Education, Inc. 14-1 The Brain • The Brain Stem • Processes information between: • Spinal cord and cerebrum or cerebellum • Includes: • Midbrain • Pons • Medulla oblongata © 2012 Pearson Education, Inc. 14-1 The Brain • Midbrain • Also called mesencephalon • Processes sight, sound, and associated reflexes • Maintains consciousness • Pons • Connects cerebellum to brain stem • Is involved in somatic and visceral motor control © 2012 Pearson Education, Inc. 14-1 The Brain • Medulla Oblongata • Connects brain to spinal cord • Relays information • Regulates autonomic functions • Heart rate, blood pressure, and digestion © 2012 Pearson Education, Inc. Figure 14-1 An Introduction to Brain Structures and Functions DIENCEPHALON THALAMUS • Relay and processing centers for sensory information HYPOTHALAMUS • Centers controlling emotions, autonomic functions, and hormone production MIDBRAIN Brain stem • Processing of visual and auditory data • Generation of reflexive somatic motor responses • Maintenance of consciousness PONS • Relays sensory information to cerebellum and thalamus • Subconscious somatic and visceral motor centers © 2012 Pearson Education, Inc. MEDULLA OBLONGATA • Relays sensory information to thalamus and to other portions of the brain stem • Autonomic centers for regulation of visceral function (cardiovascular, respiratory, and digestive system activities) 14-1 The Brain • Ventricles of the Brain • Within the brain are 4 spaces called ventricles • 2 lateral ventricles • Third ventricle • Fourth ventricle • Connects with third ventricle via narrow canal in midbrain called the cerebral aqueduct © 2012 Pearson Education, Inc. Figure 14-2a Ventricles of the Brain Cerebral hemispheres Ventricles of the Brain Lateral ventricles Third ventricle Cerebral aqueduct Fourth ventricle Pons Medulla oblongata Spinal cord Ventricular system, lateral view © 2012 Pearson Education, Inc. Central canal Figure 14-2b Ventricles of the Brain Ventricles of the Brain Cerebral hemispheres Lateral ventricles Third ventricle Fourth ventricle Central canal Cerebellum Ventricular system, anterior view © 2012 Pearson Education, Inc. 14-1 The Brain • The Brain • The brain is a large, delicate mass of neural tissue • Containing internal passageways and chambers filled with cerebrospinal fluid • Each of the six major brain regions has specific functions • Ascending from the medulla oblongata to the cerebrum, brain functions become more complex and variable • Conscious thought and intelligence • Are produced in the neural cortex of the cerebral hemispheres © 2012 Pearson Education, Inc. 14-2 Brain Protection and Support • Physical Protection of the Brain • Bones of the cranium • Cranial meninges • Cerebrospinal fluid • Biochemical Isolation • Blood–brain barrier © 2012 Pearson Education, Inc. 14-2 Brain Protection and Support • The Cranial Meninges • Have three layers 1. Dura mater 2. Arachnoid mater 3. Pia mater • Are continuous with spinal meninges • Protect the brain from cranial trauma © 2012 Pearson Education, Inc. 14-2 Brain Protection and Support • The Cranial Meninges • Dura mater • Inner fibrous layer • Arachnoid mater • Covers brain • Contacts epithelial layer of dura mater • Subarachnoid space between arachnoid mater and pia mater • Pia mater • Attached to brain surface by astrocytes © 2012 Pearson Education, Inc. 14-2 Brain Protection and Support • Dural Folds • Folded inner layer of dura mater • Extend into cranial cavity • Stabilize and support brain • Contain collecting veins (dural sinuses) © 2012 Pearson Education, Inc. Figure 14-3a The Relationship among the Brain, Cranium, and Meninges Dura mater (endosteal layer) Dural sinus Dura mater (meningeal layer) Subdural space Arachnoid mater Subarachnoid space Arachnoid trabeculae Pia mater Cerebral cortex Cerebral cortex Cerebellum Medulla oblongata Spinal cord A lateral view of the brain, showing its position in the cranium and the organization of the meninges © 2012 Pearson Education, Inc. Cranium (skull) 14-2 Brain Protection and Support • Cerebrospinal Fluid (CSF) – subarachnoid space is filled with CSF • Surrounds all exposed surfaces of CNS • Interchanges with interstitial fluid of brain • Functions of CSF • Cushions delicate neural structures • Supports brain • Transports nutrients, chemical messengers, and waste products © 2012 Pearson Education, Inc. 14-2 Brain Protection and Support • Cerebrospinal Fluid (CSF) • Choroid plexus—site of CSF production • Specialized ependymal cells and capillaries • Secrete CSF into ventricles • Remove waste products from CSF • Adjust composition of CSF • Produces about 500 mL of CSF/day © 2012 Pearson Education, Inc. 14-2 Brain Protection and Support • Cerebrospinal Fluid (CSF) • CSF circulates: • From choroid plexus • Through ventricles • To central canal of spinal cord • Into subarachnoid space via two lateral apertures and one median aperture around the brain, spinal cord, and cauda equina © 2012 Pearson Education, Inc. 14-2 Brain Protection and Support • Blood Supply to the Brain • Supplies nutrients and oxygen to brain • Delivered by internal carotid arteries and vertebral arteries • Removed from dural sinuses by internal jugular veins © 2012 Pearson Education, Inc. Figure 21–24a Arteries of the Brain © 2012 Pearson Education, Inc. Figure 21–29a Major Veins of the Head, Neck, and Brain © 2012 Pearson Education, Inc. 14-2 Brain Protection and Support • Blood–Brain Barrier (BBB) • Isolates CNS neural tissue from general circulation • Formed by network of tight junctions • Between endothelial cells of CNS capillaries • Lipid-soluble compounds (O2, CO2) and steroids • Diffuse into interstitial fluid of brain and spinal cord • Astrocytes control blood–brain barrier by: • Releasing chemicals that control permeability of endothelium © 2012 Pearson Education, Inc. 14-2 Brain Protection and Support • Blood–CSF Barrier • Formed by special ependymal cells • Surrounds capillaries of choroid plexus • Limits movement of compounds transferred • Allows chemical composition of blood and CSF to differ © 2012 Pearson Education, Inc. 14-2 Brain Protection and Support • Protection and Support • Meninges stabilize brain in cranial cavity • Cerebrospinal fluid protects against sudden movement • CSF provides nutrients and removes wastes • Blood–brain barrier and blood–CSF barrier • Selectively isolate brain from chemicals in blood that might disrupt neural function © 2012 Pearson Education, Inc. 14-3 The Medulla Oblongata • The Medulla Oblongata • Allows brain and spinal cord to communicate • Coordinates complex autonomic reflexes • Controls visceral functions • Sensory and Motor Nuclei of the Medulla Oblongata • Associated with 5 of 12 cranial nerves (VIII, IX, X, XI, XII) © 2012 Pearson Education, Inc. Figure 14-5a The Diencephalon and Brain Stem Diencephalon Cerebral peduncle Lateral geniculate nucleus Thalamus Optic tract Medial geniculate nucleus Cranial nerves Midbrain Superior colliculus N II Inferior colliculus N III N IV Cerebellar peduncles Superior cerebellar peduncle NV Pons N VI N VII N VIII N IX NX N XI Middle cerebellar peduncle Inferior cerebellar peduncle Medulla oblongata N XII Spinal nerve C1 Spinal nerve C2 Spinal cord Lateral view © 2012 Pearson Education, Inc. Medulla Oblongata Summary • The pathway from spinal cord to brain through which all ascending (sensory) and descending (motor) fibers pass. Many of the nuclei involved in basic survival processes such as coughing, sneezing, sweating, and chewing are found here as well as nuclei that control the heart rate, respiratory rate, and blood pressure. © 2012 Pearson Education, Inc. 14-4 The Pons • The Pons • Sensory and motor nuclei of cranial nerves (V, VI, VII, VIII) • “the bridge” contains fiber tracts that connect the medulla and midbrain as well as transverse tracks between left and right cerebellar hemispheres. © 2012 Pearson Education, Inc. Figure 14-6c The Medulla Oblongata and Pons Tracts Ascending tracts Respiratory Centers Descending tracts Pneumotaxic center Apneustic center Transverse fibers Cerebellum Midbrain Fourth ventricle Pons Medulla oblongata Medulla oblongata Reticular formation Olivary nucleus Spinal cord Lateral view © 2012 Pearson Education, Inc. 14-5 The Cerebellum • Summary • Located in the posterior part of the brain, it plays an important role in motor control, interpreting textures of objects, some spatial perception, understanding some aspects of speech, and time keeping. • It is the second largest part of the brain and externally exhibits gyri and folia • Functions of the Cerebellum 1. Adjusts postural muscles 2. Fine-tunes conscious and subconscious movements © 2012 Pearson Education, Inc. Figure 14-7a The Cerebellum Vermis Anterior lobe Posterior lobe Left Hemisphere of Cerebellum Primary fissure Folia Right Hemisphere of Cerebellum The posterior, superior surface of the cerebellum, showing major anatomical landmarks and regions © 2012 Pearson Education, Inc. Figure 14-7b The Cerebellum Midbrain Anterior lobe Cerebellar Peduncles Pons Arbor vitae Superior cerebellar peduncle Cerebellar nucleus Middle cerebellar peduncle Cerebellar cortex Posterior lobe Inferior cerebellar peduncle Choroid plexus of the fourth ventricle Medulla oblongata Flocculonodular lobe A sectional view of the cerebellum, showing the arrangement of gray matter and white matter © 2012 Pearson Education, Inc. 14-6 The Midbrain • Structures of the Midbrain • Two pairs of sensory nuclei (corpora quadrigemina) • Superior colliculus (visual) • Inferior colliculus (auditory) • Summary • The corpora quadrigemina control reflexes of the eye and ear. Fiber tracts extend between the pons and cerebrum and between the midbrain and the cerebellum. Contains nuclei of cranial nerves III and IV. © 2012 Pearson Education, Inc. Figure 14-8a The Midbrain Thalamus Pineal gland Red nucleus Substantia nigra Corpora quadrigemina Cerebral peduncle Superior colliculus Inferior colliculus Reticular formation A posterior view. The underlying nuclei are colored only on the right. © 2012 Pearson Education, Inc. 14-7 The Diencephalon • The Diencephalon • Integrates sensory information and motor commands • Thalamus, epithalamus, and hypothalamus © 2012 Pearson Education, Inc. 14-7 The Diencephalon • Thalamus: site of some aspects of emotion and memory; relay and filter to the cerebrum for the special senses and motor activity • Hypothalamus: Inferior to the thalamus. The major controller of the autonomic nervous system and the link between the nervous system and much of the endocrine system via its connection with the pituitary gland. It is also involved in memory, thermoregulation, satiety, thirst, sleep, and emotion. • Epithalamus: contains the pineal gland (endocrine in function) and a relay from the limbic system to the midbrain. © 2012 Pearson Education, Inc. 14-9 The Cerebrum • The Cerebrum • Is the largest part of the brain • Controls all conscious thoughts and intellectual functions • Processes somatic sensory and motor information © 2012 Pearson Education, Inc. 14-9 The Cerebrum • The Cerebrum Summary • Forms the bulk of the brain, is folded superficially to form ridges (gyri) and grooves (sulci). • A longitudinal fissure divides the cerebrum into 2 cerebral hemispheres. Each hemisphere is further subdivided into 5 lobes: frontal, parietal, temporal, insula, and occipital. © 2012 Pearson Education, Inc. Figure 14-12a The Brain in Lateral View Central sulcus FRONTAL LOBE PARIETAL LOBE OCCIPITAL LOBE Lateral sulcus TEMPORAL LOBE Pons Medulla oblongata Lateral view, cadaver brain © 2012 Pearson Education, Inc. Cerebellum Figure 14-12b The Brain in Lateral View Precentral gyrus Central sulcus Postcentral gyrus PARIETAL LOBE FRONTAL LOBE OCCIPITAL LOBE TEMPORAL LOBE Lateral sulcus Cerebellum Pons Medulla oblongata Lateral view © 2012 Pearson Education, Inc. Figure 14-12c The Brain in Lateral View Insula Retractors along the lateral sulcus showing the insula © 2012 Pearson Education, Inc. Figure 14-12d The Brain in Lateral View Precentral gyrus Central sulcus Postcentral gyrus Cingulate gyrus PARIETAL LOBE FRONTAL LOBE Parietooccipital sulcus OCCIPITAL LOBE TEMPORAL LOBE Medulla oblongata Midsagittal section © 2012 Pearson Education, Inc. Pons Cerebellum 14-9 The Cerebrum • The Cerebrum Summary • The cerebrum receives sensory information from both internal and external stimuli. Within the cerebral gray matter, this information is evaluated in conjunction with memory and is used to coordinate motor output . • The fiber tracts (white matter) of the brain serve to receive or send information to the rest of the body (projection tracts), cross from one cerebral hemisphere to the other (commissural tracts such as the corpus collosum), or connect different regions within one hemisphere (association tracts). • Deep pockets of gray matter called the basal nuclei are involved in motor control. © 2012 Pearson Education, Inc. 14-9 The Cerebrum • Three Functional Principles of the Cerebrum 1. Each cerebral hemisphere receives sensory information from, and sends motor commands to, the opposite side of the body 2. The two hemispheres have different functions, although their structures are alike 3. Correspondence between a specific function and a specific region of cerebral cortex is not precise © 2012 Pearson Education, Inc. Figure 14-13b Fibers of the White Matter of the Cerebrum Longitudinal fissure Corpus callosum Projection fibers of internal capsule Anterior commissure Anterior view © 2012 Pearson Education, Inc. • Motor and Sensory Areas of the Cortex © 2012 Pearson Education, Inc. Figure 14-15a Motor and Sensory Regions of the Cerebral Cortex Primary motor cortex (precentral gyrus) Central sulcus Primary sensory cortex (postcentral gyrus) Somatic motor association area (premotor cortex) PARIETAL LOBE Somatic sensory association area FRONTAL LOBE Visual association area Prefrontal cortex OCCIPITAL LOBE Gustatory cortex Visual cortex Insula Auditory association area Lateral sulcus Olfactory cortex Auditory cortex TEMPORAL LOBE Major anatomical landmarks on the surface of the left cerebral hemisphere. The lateral sulcus has been pulled apart to expose the insula. © 2012 Pearson Education, Inc. 14-9 The Cerebrum • Hemispheric Lateralization • Functional differences between left and right hemispheres • Each cerebral hemisphere performs certain functions that are not ordinarily performed by the opposite hemisphere © 2012 Pearson Education, Inc. 14-9 The Cerebrum • The Left Hemisphere • In most people, left brain (dominant hemisphere) controls: • Reading, writing, and math • Decision making • Speech and language • The Right Hemisphere • Right cerebral hemisphere relates to: • Senses (touch, smell, sight, taste, feel) • Recognition (faces, voice inflections) © 2012 Pearson Education, Inc. Figure 14-16 Hemispheric Lateralization Left Cerebral Hemisphere LEFT HAND Prefrontal cortex Speech center Writing Auditory cortex General interpretive center (language and mathematical calculation) Visual cortex (right visual field) © 2012 Pearson Education, Inc. C O R P U S C A L L O S U M Figure 14-16 Hemispheric Lateralization Right Cerebral Hemisphere RIGHT HAND Prefrontal cortex Anterior commissure C O R P U S C A L L O S U M Analysis by touch Auditory cortex Spatial visualization and analysis Visual cortex (left visual field) © 2012 Pearson Education, Inc. 14-10 Cranial Nerves • Cranial Nerves • 12 pairs connected to brain • Four Classifications of Cranial Nerves 1. Sensory nerves carry somatic sensory information, including touch, pressure, vibration, temperature, and pain 2. Special sensory nerves carry sensations such as smell, sight, hearing, balance 3. Motor nerves: axons of somatic motor neurons 4. Mixed nerves: mixture of motor and sensory fibers © 2012 Pearson Education, Inc. 14-10 Cranial Nerves • Cranial Nerves • Are classified by primary functions • May also have important secondary functions • Distributing autonomic fibers to peripheral ganglia • The 12 cranial nerve groups are identified by: • Primary function • Origin • Pathway • Destination © 2012 Pearson Education, Inc. Cranial Nerve I: Olfactory II: Optic III: Oculomotor Nerve Type sensory sensory primarily motor IV: Trochlear primarily motor V: Trigeminal: sensory VI: Abducens primarily motor eyeball movement; proprioception (lateral rectus muscle) VII: Facial mixed movement of facial muscles; tear and saliva secretion; sense of taste and proprioception VIII: Vestibulocochlear: cochlear branch VIII: Vestibulocochle-ar: vestibular branch sensory sensory hearing sense of equilibrium mixed sensations of taste, touch, and pain from tongue and pharynx; chemoreceptors (that monitor O2and CO2); blood pressure receptors; movement of tongue and swallowing; secretion of saliva X: Vagus mixed parasympathetic sensation and motor control of smooth muscles associated with heart, lungs, viscera; secretion of digestive enzymes XI: Accessory primarily motor head movement; swallowing; proprioception XII: Hypoglossal primarily motor tongue movement, speech, and swallowing; proprioception IX: Glosso-phayrngeal © 2012 Pearson Education, Inc. Major Functions smell vision eyeball and eyelid movement; lens shape eyeball movement; proprioception (superior oblique muscle) sensations of touch and pain from facial skin, nose, mouth, teeth, and tongue; proprioception motor control of chewing Figure 14-18 Origins of the Cranial Nerves Olfactory bulb: termination of olfactory nerve (I) Olfactory tract Optic nerve (II) Infundibulum Oculomotor nerve (III) Pons Basilar artery Vertebral artery Cerebellum Medulla oblongata Spinal cord © 2012 Pearson Education, Inc. Figure 14-18 Origins of the Cranial Nerves Optic chiasm Optic tract Mamillary body Trochlear nerve (IV) Trigeminal nerve (V) Abducens nerve (VI) Facial nerve (VII) Vestibulocochlear nerve (VIII) Glossopharyngeal nerve (IX) Vagus nerve (X) Hypoglossal nerve (XII) Accessory nerve (XI) © 2012 Pearson Education, Inc. Figure 14-21 Cranial Nerves Controlling the Extra-Ocular Muscles Superior rectus muscle Superior oblique muscle OPTIC NERVE (N II) Optic chiasm OCULOMOTOR NERVE (N III) TROCHLEAR NERVE (N IV) Trochlea Levator palpebrae superioris muscle Trigeminal nerve (N V), cut Inferior oblique muscle Vestibulocochlear nerve (N VIII), cut Inferior rectus muscle © 2012 Pearson Education, Inc. Ciliary ganglion Medial rectus muscle Facial nerve (N VII), cut Lateral rectus muscle (cut) ABDUCENS NERVE (N VI) Figure 14-22 The Trigeminal Nerve Superior orbital fissure Supra-orbital nerves Ophthalmic branch Semilunar ganglion Ciliary ganglion Pons TRIGEMINAL NERVE (N V) Foramen rotundum Maxillary branch Infra-orbital nerve Foramen ovale Lingual nerve Otic ganglion Submandibular ganglion Mandibular branch Pterygopalatine ganglion Mental nerve © 2012 Pearson Education, Inc. Figure 14-23a The Facial Nerve Pterygopalatine ganglion Greater petrosal nerve Geniculate ganglion FACIAL NERVE (N VII) Temporal branch Pons Zygomatic branches Posterior auricular branch Buccal branch Stylomastoid foramen Chorda tympani nerve (with mandibular branch of N V) Mandibular branch Lingual branch (with lingual nerve of N V) Cervical branch The origin and branches of the facial nerve © 2012 Pearson Education, Inc. Submandibular ganglion Figure 14-24 The Vestibulocochlear Nerve Tympanic cavity (middle ear) Semicircular canals Vestibular branch (N VIII) Facial nerve (N VII), cut Internal acoustic meatus VESTIBULOCOCHLEAR NERVE (N VIII) NV Pons N VI N VII N IX N XII NX Medulla oblongata N XI Tympanic membrane © 2012 Pearson Education, Inc. Auditory tube Cochlea Cochlear branch (N VIII) Figure 14-25 The Glossopharyngeal Nerve Pons NV N VII N VIII N VI GLOSSOPHARYNGEAL NERVE (N IX) Otic ganglion Medulla oblongata Inferior (petrosal) ganglion Superior (jugular) ganglion Parotid salivary gland Lingual branch Pharyngeal branches Carotid sinus branch Carotid body Carotid sinus Common carotid artery © 2012 Pearson Education, Inc. Figure 14-26 The Vagus Nerve Superior pharyngeal branch VAGUS NERVE (N X) Pons Medulla oblongata Auricular branch to external ear Inferior ganglion of vagus nerve Internal branch Superior laryngeal nerve External branch © 2012 Pearson Education, Inc. Superior ganglion of vagus nerve Pharyngeal branch Superior laryngeal nerve Figure 14-27 The Accessory and Hypoglossal Nerves HYPOGLOSSAL NERVE (N XII) ACCESSORY NERVE (N XI) Internal branch: to palatal, pharyngeal, and laryngeal muscles with vagus nerve Intrinsic muscles of tongue Trigeminal nerve (N V) Medulla oblongata Cranial root of N XI Spinal root of N XI Styloglossus muscle External branch of N XI Genioglossus muscle Geniohyoid muscle Spinal cord Hyoglossus muscle Hyoid bone Thyrohyoid muscle Trapezius muscle Sternocleidomastoid muscle Sternohyoid muscle Sternothyroid muscle Ansa cervicalis (cervical plexus) Omohyoid muscle © 2012 Pearson Education, Inc.