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Chapter 14: The Brain & Cranial Nerves
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Homeostasis Brain receives input, integrates new & stored info, makes decisions, & executes responses through motor activities
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Development of the Brain
Develops from neural tube
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Figure 14-1 An Introduction to Brain Structures and Functions.
Left cerebral hemisphere Gyri Cerebrum Sulci • Conscious thought processes, intellectual functions • Memory storage and processing • Conscious and subconscious regulation of skeletal muscle contractions Fissures Diencephalon Thalamus • Relay and processing centers for sensory information Hypothalamus • Centers controlling emotions, autonomic functions, and hormone production Cerebellum • Coordinates complex somatic motor patterns • Adjusts output of other somatic motor centers in brain and spinal cord Spinal cord Midbrain Brain stem • Processing of visual and auditory date • Generation of reflexive somatic motor responses • Maintenance of consciousness Pons • Relays sensory information to cerebellum and thalamus • Subconscious somatic and visceral motor centers 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)
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Superior sagittal sinus Inferior sagittal sinus
Cranial Meninges Dura mater (periosteal layer) Cranium Dural sinus Dura mater (meningeal layer) Subarachnoid space Pia mater Subdural space Arachnoid mater Cerebral cortex Dura mater Superior sagittal sinus Cranium Inferior sagittal sinus Dural folds Cerebrum Falx cerebri Tentorium cerebelli Falx cerebelli Cerebellum Medulla oblongata Transverse sinus Spinal cord a A lateral view of the brain, showing its position in the cranium and the organization of the meninges b A diagrammatic view, showing the orientation of the three largest dural folds: the falx cerebri, tentorium cerebelli, and falx cerebelli
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Ventricles of the Brain
Spaces within cerebrum Produces CSF Nourishes & protects brain & spinal cord Pons Medulla oblongata Spinal cord Central canal Cerebral hemispheres Cerebellum Ventricles of the Brain Lateral ventricles Interventricular foramen Third ventricle Cerebral aqueduct Fourth ventricle Ventricles, lateral view Ventricles, anterior view b a Cerebral hemispheres
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Figure 14-4 Formation and Circulation of Cerebrospinal Fluid.
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Diencephalon Midbrain Pons Medulla oblongata Thalamus
Figure 14-1 An Introduction to Brain Structures and Functions (Part 2 of 2). 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 date • Generation of reflexive somatic motor responses • Maintenance of consciousness Pons • Relays sensory information to cerebellum and thalamus • Subconscious somatic and visceral motor centers 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)
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Figure 14-5 The Diencephalon and Brain Stem.
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Figure 14-6 The Medulla Oblongata.
Autonomic centers Reticular formation Medulla oblongata Cardiovascular centers Solitary nucleus Pons Relay stations Olivary nucleus Olive Nucleus cuneatus Pyramids Spinal cord Nucleus gracilis Decussation of pyramids a Lateral white columns Anterior view The Medulla Oblongata Region/Nucleus Function GRAY MATTER Olivary nucleus Relay information from the red nuclei, other midbrain centers, and the cerebral cortex to the cerebellum Attachment to membranous roof of fourth ventricle Reflex centers Regulate heart rate and force of contraction Set the basic pace of respiratory movements Cardiovascular center Respiratory rhythmicity center Nucleus gracilis Relay somatic information to the thalamus Nucleus cuneatus Other nuclei/centers Sensory and motor nuclei of five cranial nerves; nuclei relay ascending information from the spinal cord to higher centers Cranial nerves VIII (in part), IX, X, XI (in part), and XII Posterior median sulcus Reticular formation Contains nuclei and centers that regulate vital autonomic functions; extends into the pons and midbrain Lateral white column Posterior white columns WHITE MATTER Ascending and descending tracts within columns Link the brain with the spinal cord b Posterolateral view
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The Pons Figure 14-7 The Pons. WHITE MATTER Descending tracts
Region/Nucleus Function WHITE MATTER Descending tracts Carry motor commands from higher centers to nuclei of cranial or spinal nerves Ascending tracts Carry sensory information from brain stem nuclei to the thalamus Transverse fibers Interconnect cerebellar hemispheres Pons Cerebellum GRAY MATTER Apneustic and pneumotaxic centers Adjust activities of the respiratory rhythmicity centers in the medulla oblongata Fourth ventricle Reticular formation Medulla oblongata Automatic processing of incoming sensations and outgoing motor commands Spinal cord Olivary nucleus Cranial nerve nuclei N V, VI, VII, and VIII (in part) Relay sensory information and issue somatic motor commands Other nuclei/relay centers Relay sensory and motor Information to the cerebellum
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Figure 14-9 The Midbrain. The Midbrain
Region/Nuclei Function GRAY MATTER Pineal gland Tectum (roof) Superior colliculus Integrate visual information with other sensory input; initiate reflex responses to visual stimuli Thalamus Inferior colliculus Relay auditory information to medial geniculate nuclei; initiate reflex responses to auditory stimuli Walls and floor Substantia nigra Regulates activity in the basal nuclei Red nucleus Subconscious control of upper limb position and background muscle tone Reticular formation Automatic processing of incoming sensations and outgoing motor commands; can initiate involuntary motor responses to stimuli; helps maintain consciousness Other nuclei/centers: Nuclei associated with cranial nerves III and IV WHITE MATTER a A posterior view. The underlying nuclei are colored only on the right. Cerebral peduncles Connect primary motor cortex with motor neurons in brain and spinal cord; carry ascending sensory information to thalamus Corpora quadrigemina Thalamus ANTERIOR Cerebral peduncle Superior colliculi Inferior colliculi Substantia nigra Cerebral peduncle Red nucleus Trochlear nerve (N IV) Tegmentum Cerebral aqueduct Superior cerebellar peduncle Superior colliculus Cerebellum Fourth ventricle Tectum (roof) POSTERIOR b Posterior view of a cadaver dissection of the diencephalon and brain stem. c A superior view of a transverse section at the level of the midbrain.
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Reticular Formation The Pons WHITE MATTER Descending tracts
Region/Nucleus Function WHITE MATTER Descending tracts Carry motor commands from higher centers to nuclei of cranial or spinal nerves Ascending tracts Carry sensory information from brain stem nuclei to the thalamus Transverse fibers Interconnect cerebellar hemispheres Pons Cerebellum GRAY MATTER Apneustic and pneumotaxic centers Adjust activities of the respiratory rhythmicity centers in the medulla oblongata Fourth ventricle Reticular formation Medulla oblongata Automatic processing of incoming sensations and outgoing motor commands Spinal cord Olivary nucleus Cranial nerve nuclei N V, VI, VII, and VIII (in part) Relay sensory information and issue somatic motor commands Other nuclei/relay centers Relay sensory and motor Information to the cerebellum
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Cerebellum Cerebrum Left cerebral hemisphere Gyri Sulci
Figure 14-1 An Introduction to Brain Structures and Functions (Part 1 of 2). Left cerebral hemisphere Gyri Cerebrum Sulci • Conscious thought processes, intellectual functions • Memory storage and processing • Conscious and subconscious regulation of skeletal muscle contractions Fissures Cerebellum • Coordinates complex somatic motor patterns • Adjusts output of other somatic motor centers in brain and spinal cord Spinal cord
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Figure 14-8 The Cerebellum.
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Functions of Cerebellum
Evaluate intended movements & correct any discrepancies in order to obtain smooth, coordinated action Regulates posture & balance
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Diencephalon Midbrain Pons Medulla oblongata Thalamus
Figure 14-1 An Introduction to Brain Structures and Functions (Part 2 of 2). 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 date • Generation of reflexive somatic motor responses • Maintenance of consciousness Pons • Relays sensory information to cerebellum and thalamus • Subconscious somatic and visceral motor centers 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)
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Parietal lobe and cingulate gyrus Association areas of cerebral cortex
Basal nuclei b An enlarged view of the thalamic nuclei of the left side Cerebellum General Sensory input Visual input Auditory input Pulvinar nucleus Medial geniculate nucleus Lateral geniculate nucleus Ventral group Posterior group Lateral group Medial group Anterior group Limbic system Frontal lobes Parietal lobe and cingulate gyrus Association areas of cerebral cortex a A lateral view of the brain, color coded to indicate the regions that receive input from the thalamic nuclei shown in part (b) Frontal lobe Parietal lobe Occipital lobe Thalamus Major sensory relay station to cortex
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Table 14-2 The Thalamus.
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Hypothalamus The Hypothalamus
Parietal lobe Corpus callosum Septum pellucidum Choroid plexus Thalamus (surrounds third ventricle) Fornix Anterior cerebral artery Pineal gland Hypothalamus Frontal lobe Cerebral aqueduct Anterior commissure Cerebellum Optic chiasm Optic nerve Fourth ventricle a The hypothalamus and adjacent portions of the brain Infundibulum (cut) Tuberal area Mammillary body Interthalamic adhesion The Hypothalamus Thalamus Region/Nuclei Function Paraventricular nucleus Secretes oxytocin, stimulating smooth muscle contractions in uterus and mammary glands Preoptic area Regulates body temperature by control of autonomic centers in the medulla oblongata Hypothalamus Tuberal area Autonomic centers Control heart rate and blood pressure by regulation of autonomic centers in the medulla oblongata Sympathetic Optic chiasm Parasympathetic Tuberal nucleus Produces inhibitory and releasing hormones that control endocrine cells of the anterior lobe of the pituitary gland (adenohypophysis) Mid- brain Infundibulum Mammillary body Control feeding reflexes (licking, swallowing, etc.) Suprachiasmatic nucleus Regulates daily (circadian) rhythms Pituitary gland Pons Supraoptic nucleus Secretes antidiuretic hormone, restricting water loss by the kidneys b A diagrammatic view of the hypothalamus, showing the locations and functions of major nuclei and centers
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Epithalamus Consists of pineal gland & habenular nuclei Pineal gland
Secretes melatonin Habenular nuclei Involved in emotional responses to odors
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Circumventricular Organs
CVOs Includes parts of diencephalon Part of hypothalamus Pineal gland Pituitary gland Few other structures Can monitor chemical changes in blood because no blood-brain barrier Helps in coordinating activities of nervous & endocrine systems
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Cerebellum Cerebrum Left cerebral hemisphere Gyri Sulci
Figure 14-1 An Introduction to Brain Structures and Functions (Part 1 of 2). Left cerebral hemisphere Gyri Cerebrum Sulci • Conscious thought processes, intellectual functions • Memory storage and processing • Conscious and subconscious regulation of skeletal muscle contractions Fissures Cerebellum • Coordinates complex somatic motor patterns • Adjusts output of other somatic motor centers in brain and spinal cord Spinal cord
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Figure 14-13 The Brain in Lateral View.
Central sulcus Frontal lobe Parietal lobe Occipital lobe Lateral sulcus Temporal lobe Cerebellum Precentral gyrus Central sulcus Postcentral gyrus Pons Medulla oblongata a Lateral view, cadaver brain Frontal lobe Parietal lobe Occipital lobe Temporal lobe Lateral sulcus Cerebellum Pons Medulla oblongata b Lateral view Insula Precentral gyrus Central sulcus Postcentral gyrus c Retractors along the lateral sulcus showing the insula Cingulate gyrus Parietal lobe Frontal lobe Parieto- occipital sulcus Occipital lobe Pons Temporal lobe Cerebellum Medulla oblongata d Midsagittal section
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Figure 14-16 Motor and Sensory Regions of the Cerebral Cortex.
Central sulcus Parietal Lobe Frontal Lobe Primary sensory cortex (postcentral gyrus) Primary motor cortex (precentral gyrus) Somatic motor association area (premotor cortex) Somatic sensory association area Retractor Occipital Lobe Prefrontal cortex Visual association area Visual cortex Gustatory cortex Insula Temporal Lobe Lateral sulcus Auditory association area Auditory cortex Olfactory cortex a Major anatomical landmarks on the surface of the left cerebral hemisphere. The lateral sulcus has been pulled apart to expose the insula. Frontal eye field 4 Speech center 6 1 40 39 Prefrontal cortex General interpretive area 44 41 42 18 17 b The left hemisphere generally contains the general interpretive area and the speech center. The prefrontal cortex of each hemisphere is involved with conscious intellectual functions. c Regions of the cerebral cortex as determined by histological analysis. Several of the 50 Brodmann areas are shown for comparison with the results of functional mapping.
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Table 14-3 The Cerebral Cortex.
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Figure 14-14 Fibers of the White Matter of the Cerebrum.
Fibers/Tracts Function Association fibers Interconnect cortical areas within the same hemisphere Arcuate fibers Interconnect gyri within a lobe Lateral view a Longitudinal fasciculi Interconnect the frontal lobe with other cerebral lobes Commissures Interconnect and permit communication between the cerebral hemispheres Corpus callosum Longitudinal fissure Anterior commissure Projection fibers Connect cerebral cortex to diencephalon, brain stem, cerebellum, and spinal cord Internal capsule Anterior view b
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Figure 14-15 The Basal Nuclei.
Corpus callosum Lateral ventricle (anterior horn) Head of caudate nucleus Septum pellucidum Internal capsule Fornix (cut edge) Putamen Thalamus Third ventricle Choroid plexus Pineal gland Fornix Lateral ventricle (posterior horn) Head of caudate nucleus Lentiform nucleus Tail of caudate nucleus Thalamus Amygdaloid body b A superior view of two transverse sections at different levels a The relative positions of the basal nuclei in the intact brain, lateral view The Basal Nuclei Corpus callosum Nuclei Function Lateral ventricle Caudate nucleus Subconscious adjustment and modification of voluntary motor commands Septum pellucidum Internal capsule Lentiform nucleus Subconscious adjustment and modification of voluntary motor commands Putamen Lateral sulcus Globus pallidus Insula Anterior commissure Claustrum Plays a role in the subconscious processing of visual information Tip of inferior horn of lateral ventricle Amygdaloid body Component of limbic system c Frontal section
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Figure 14-12 The Limbic System.
Corpus callosum Pineal gland Fornix Cingulate gyrus (superior portion of limbic lobe) Anterior group of thalamic nuclei Parahippocampal gyrus (inferior portion of limbic lobe) Hypothalamus Mammillary body Hippocampus (within dentate gyrus) Temporal lobe of cerebrum a A diagrammatic sagittal section through the cerebrum, showing the cortical areas associated with the limbic system. The parahippocampal gyrus is shown as though transparent to make deeper limbic components visible. The Limbic System The Limbic System Cerebral Components Limbic lobe cortical areas Diencephalic Components Corpus callosum Cingulate gyrus (superior portion of limbic lobe) Thalamus Anterior nuclei group Parahippocampal gyrus (inferior portion of limbic lobe) Hypothalamus Dentate gyrus Hypothalamic nuclei Tracts Mammillary body Fornix Other Components Nuclei Reticular formation Amygdaloid body (not shown) Olfactory tract Hippocampus (within dentate gyrus) b A three-dimensional reconstruction of the limbic system, showing the relationships among the major components.
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Figure 14-13b The Brain in Lateral View.
Precentral gyrus Central sulcus Postcentral gyrus Frontal lobe Parietal lobe Occipital lobe Temporal lobe Lateral sulcus Cerebellum Pons Medulla oblongata b Lateral view
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Figure 14-13d The Brain in Lateral View.
Precentral gyrus Central sulcus Postcentral gyrus Cingulate gyrus Parietal lobe Frontal lobe Parieto- occipital sulcus Occipital lobe Pons Temporal lobe Cerebellum Medulla oblongata d Midsagittal section
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Functional Areas of the Cerebrum
Central sulcus Parietal Lobe Frontal Lobe Primary sensory cortex (postcentral gyrus) Primary motor cortex (precentral gyrus) Somatic motor association area (premotor cortex) Somatic sensory association area Retractor Occipital Lobe Visual association area Prefrontal cortex Visual cortex Gustatory cortex Insula Temporal Lobe Lateral sulcus Auditory association area Auditory cortex Olfactory cortex a Major anatomical landmarks on the surface of the left cerebral hemisphere. The lateral sulcus has been pulled apart to expose the insula.
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Figure 14-16b Motor and Sensory Regions of the Cerebral Cortex.
Frontal eye field Speech center Prefrontal cortex General interpretive area b The left hemisphere generally contains the general interpretive area and the speech center. The prefrontal cortex of each hemisphere is involved with conscious intellectual functions.
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Figure 14-16c Motor and Sensory Regions of the Cerebral Cortex.
40 39 44 41 42 18 17 c Regions of the cerebral cortex as determined by histological analysis. Several of the 50 Brodmann areas are shown for comparison with the results of functional mapping.
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Figure 14-17 Hemispheric Lateralization.
Left Cerebral Hemisphere Right Cerebral Hemisphere LEFT HAND RIGHT HAND Prefrontal cortex Prefrontal cortex Speech center Anterior commissure C O R P U S Writing Analysis by touch C A L L O S U M Auditory cortex (right ear) Auditory cortex (left ear) Spatial visualization and analysis General interpretive center (language and mathematical calculation) Visual cortex (right visual field) Visual cortex (left visual field)
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Alpha waves are characteristic of normal resting adults
Figure Brain Waves. Patient being wired for EEG monitoring a Alpha waves are characteristic of normal resting adults b Beta waves typically accompany intense concentration c Theta waves are seen in children and in frustrated adults d Delta waves occur in deep sleep and in certain pathological conditions 0 Seconds
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Figure 14-19 Origins of the Cranial Nerves.
Olfactory bulb: termination of olfactory nerve (N I) Olfactory tract Optic chiasm Optic tract Optic nerve (N II) Mammillary body Infundibulum Trochlear nerve (N IV) Oculomotor nerve (N III) Trigeminal nerve (N V) Abducens nerve (N VI) Basilar artery Pons Facial nerve (N VII) Vertebral artery Vestibulocochlear nerve (N VIII) Medulla oblongata Glossopharyngeal nerve (N IX) Cerebellum Vagus nerve (N X) Hypoglossal nerve (N XII) Spinal cord Accessory nerve (N XI)
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Figure 14-20 The Olfactory Nerve.
Olfactory tract (to olfactory cortex of cerebrum) Left olfactory bulb (termination of olfactory nerve) Olfactory nerve (N I) Olfactory nerve fibers Cribriform plate of ethmoid bone Olfactory epithelium
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Figure 14-21 The Optic Nerve.
Eye Pituitary gland Olfactory bulb Olfactory tract Optic nerve (N II) Optic chiasm Optic tract Lateral geniculate nucleus (in thalamus) Midbrain (cut) Visual cortex (in occipital lobes) Optic projection fibers
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Figure 14-22 Cranial Nerves Controlling the Extrinsic Eye Muscles.
Superior rectus muscle Optic nerve (N II) Optic chiasm Oculomotor nerve (N III) Trochlear nerve (N IV) Superior oblique muscle Trochlea Levator palpebrae superioris muscle Trigeminal nerve (N V), cut Inferior oblique muscle Vestibulocochlear nerve (N VIII), cut Facial nerve (N VII), cut Inferior rectus muscle Medial rectus muscle Ciliary ganglion Lateral rectus muscle (cut) Abducens nerve (N VI)
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Figure 14-23 The Trigeminal Nerve.
Superior orbital fissure Ophthalmic branch Supraorbital nerves Semilunar ganglion Ciliary ganglion Pons Trigeminal nerve (N V) Foramen rotundum Maxillary branch Infraorbital nerve Foramen ovale Otic ganglion Lingual nerve Submandibular ganglion Mandibular branch Mental nerve Pterygopalatine ganglion
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Figure 14-24 The Facial Nerve.
Pterygopalatine ganglion Greater petrosal nerve Geniculate ganglion Facial nerve (N VII) Temporal branch Zygomatic branch Temporal branch Buccal branch Mandibular branch Pons Cervical branch b The superficial distribution of the five major branches of the facial nerve 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 Submandibular ganglion a The origin and branches of the facial nerve
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Figure 14-25 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) N V Pons N VI N VII N IX N XII N X Medulla oblongata N XI Tympanic membrane Auditory tube Cochlea Cochlear branch (N VIII)
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Figure 14-26 The Glossopharyngeal Nerve.
Pons N V N VII N VIII N VI Glossopharyngeal nerve (N IX) Otic ganglion Medulla oblongata Inferior (petrosal) ganglion Superior (jugular) ganglion Pharyngeal branches Lingual branch Parotid salivary gland Carotid sinus branch Carotid body Carotid sinus Common carotid artery
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Figure 14-27 The Vagus Nerve.
Pharyngeal branch Vagus nerve (N X) Pons Medulla oblongata Auricular branch to external ear Superior ganglion of vagus nerve Inferior ganglion of vagus nerve Pharyngeal branch Superior laryngeal nerve Internal branch Superior laryngeal nerve External branch Recurrant laryngeal nerve Cardiac branches Cardiac plexus Right lung Left lung Liver Anterior vagal trunk Spleen Stomach Celiac plexus Pancreas Colon Small intestine Hypogastric plexus
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Figure 14-28 The Accessory and Hypoglossal Nerves.
Hypoglossal nerve (N XII) Trigeminal nerve (N V) Accessory nerve (N XI) Medulla oblongata Cranial root of N XI Internal branch: to palatal, pharyngeal, and laryngeal muscles with vagus nerve Spinal root of N XI Intrinsic muscles of tongue Styloglossus muscle External branch of N XI Genioglossus muscle Geniohyoid muscle Spinal cord Hyoglossus muscle Hyoid bone Trapezius muscle Thyrohyoid muscle Sternocleidomastoid muscle Sternohyoid muscle Ansa cervicalis (cervical plexus) Sternothyroid muscle Omohyoid muscle
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Table 14-4 Cranial Nerve Branches and Functions (Part 1 of 2).
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Table 14-4 Cranial Nerve Branches and Functions (Part 2 of 2).
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Table 14-5 Cranial Reflexes.
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