Post on 31-Aug-2021
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Chapter 14
The Brain and Cranial Nerves
An Introduction to the Brain and Cranial Nerves The Adult Human Brain
o Volume ranges from 750 mL to 2100 mL o Contains almost 97 percent of the body’s neural tissue o Average weight about 1.4 kg (3 lb)
14-1 The Brain Six Regions of the Brain
1. Cerebrum 2. Cerebellum 3. Diencephalon 4. Midbrain 5. Pons 6. Medulla oblongata
14-1 The Brain Cerebrum
o Largest part of brain o Controls higher mental functions o Divided into left and right cerebral hemispheres o Surface layer of gray matter (neural cortex)
14-1 The Brain Cerebrum
o Neural cortex Also called cerebral cortex Folded surface increases surface area Elevated ridges (gyri) Shallow depressions (sulci) Deep grooves (fissures)
14-1 The Brain Cerebellum
o Second largest part of brain o Coordinates repetitive body movements o Two hemispheres o Covered with cerebellar cortex
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14-1 The Brain Diencephalon
o Located under cerebrum and cerebellum o Links cerebrum with brain stem o Three divisions of the diencephalon
1. Left thalamus 2. Right thalamus 3. Hypothalamus
14-1 The Brain Diencephalon
o Thalamus Relays and processes sensory information
o Hypothalamus Hormone production Emotion Autonomic function
14-1 The Brain Diencephalon
o Pituitary gland Major endocrine gland Connected to hypothalamus Via infundibulum (stalk) Interfaces nervous and endocrine systems
14-1 The Brain The Brain Stem
o Processes information between: Spinal cord and cerebrum or cerebellum
o Includes: Midbrain Pons Medulla oblongata
14-1 The Brain Midbrain
o Also called mesencephalon o Processes sight, sound, and associated reflexes o Maintains consciousness
Pons o Connects cerebellum to brain stem
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o Is involved in somatic and visceral motor control
14-1 The Brain Medulla Oblongata
o Connects brain to spinal cord o Relays information o Regulates autonomic functions
Heart rate, blood pressure, and digestion
14-1 The Brain Embryonic Development
o Determines organization of brain structures o Neural tube
Origin of brain Enlarges into three primary brain vesicles
1. Prosencephalon 2. Mesencephalon 3. Rhombencephalon
14-1 The Brain Five Secondary Brain Vesicles
1. Telencephalon 2. Diencephalon 3. Mesencephalon 4. Metencephalon 5. Myelencephalon
14-1 The Brain Origins of Brain Structures
Diencephalon and mesencephalon persist o Telencephalon
Becomes cerebrum o Metencephalon
Forms cerebellum and pons o Myelencephalon
Becomes medulla oblongata
14-1 The Brain Ventricles of the Brain
o Origins of ventricles Neural tube encloses neurocoel Neurocoel expands to form chambers (ventricles) lined with
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ependyma o Each cerebral hemisphere contains one large lateral ventricle
Separated by a thin medial partition (septum pellucidum)
14-1 The Brain Ventricles of the Brain
o Third ventricle Ventricle of the diencephalon Lateral ventricles communicate with third ventricle
o Via interventricular foramen (foramen of Monro)
14-1 The Brain Ventricles of the Brain
o Fourth ventricle Extends into medulla oblongata Becomes continuous with central canal of the spinal cord Connects with third ventricle
o Via narrow canal in midbrain called the cerebral aqueduct
14-1 The Brain The Brain
o The brain is a large, delicate mass of neural tissue Containing internal passageways and chambers filled with
cerebrospinal fluid o 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
o Conscious thought and intelligence Are produced in the neural cortex of the cerebral hemispheres
14-2 Brain Protection and Support Physical Protection of the Brain
o Bones of the cranium o Cranial meninges o Cerebrospinal fluid
Biochemical Isolation o Blood–brain barrier
14-2 Brain Protection and Support The Cranial Meninges
o Have three layers 1. Dura mater
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2. Arachnoid mater 3. Pia mater
o Are continuous with spinal meninges o Protect the brain from cranial trauma
14-2 Brain Protection and Support The Cranial Meninges
o Dura mater Inner fibrous layer (meningeal layer) Outer fibrous layer (periosteal layer) fused to periosteum Venous sinuses between two layers
14-2 Brain Protection and Support The Cranial Meninges
o Arachnoid mater Covers brain Contacts epithelial layer of dura mater Subarachnoid space between arachnoid mater and pia mater
o Pia mater Attached to brain surface by astrocytes
14-2 Brain Protection and Support Dural Folds
o Folded inner layer of dura mater o Extend into cranial cavity o Stabilize and support brain o Contain collecting veins (dural sinuses) o Three largest dural folds
1. Falx cerebri 2. Tentorium cerebelli 3. Falx cerebelli
14-2 Brain Protection and Support Falx Cerebri
o Projects between the cerebral hemispheres o Contains superior sagittal sinus and inferior sagittal sinus
Tentorium Cerebelli o Separates cerebellum and cerebrum o Contains transverse sinus
Falx Cerebelli o Divides cerebellar hemispheres below the tentorium cerebelli
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14-2 Brain Protection and Support Cerebrospinal Fluid (CSF)
o Surrounds all exposed surfaces of CNS o Interchanges with interstitial fluid of brain o Functions of CSF
Cushions delicate neural structures Supports brain Transports nutrients, chemical messengers, and waste products
14-2 Brain Protection and Support Cerebrospinal Fluid (CSF)
o Choroid plexus Specialized ependymal cells and capillaries
o Secrete CSF into ventricles o Remove waste products from CSF o Adjust composition of CSF
Produces about 500 mL of CSF/day
14-2 Brain Protection and Support Cerebrospinal Fluid (CSF)
o 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
14-2 Brain Protection and Support Cerebrospinal Fluid (CSF)
o CSF in subarachnoid space Arachnoid villi
o Extensions of subarachnoid space o Extend through dura mater to superior sagittal sinus
Arachnoid granulations o Large clusters of villi o Absorb CSF into venous circulation
14-2 Brain Protection and Support Blood Supply to the Brain
o Supplies nutrients and oxygen to brain o Delivered by internal carotid arteries and vertebral arteries o Removed from dural sinuses by internal jugular veins
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14-2 Brain Protection and Support Cerebrovascular Disease
o Disorders interfere with blood circulation to brain o Stroke or cerebrovascular accident (CVA)
Shuts off blood to portion of brain Neurons die
14-2 Brain Protection and Support Blood–Brain Barrier (BBB)
o Isolates CNS neural tissue from general circulation o Formed by network of tight junctions
Between endothelial cells of CNS capillaries o Lipid-soluble compounds (O2, CO2), steroids, and prostaglandins
Diffuse into interstitial fluid of brain and spinal cord o Astrocytes control blood–brain barrier by:
Releasing chemicals that control permeability of endothelium
14-2 Brain Protection and Support Blood–CSF Barrier
o Formed by special ependymal cells o Surrounds capillaries of choroid plexus o Limits movement of compounds transferred o Allows chemical composition of blood and CSF to differ
14-2 Brain Protection and Support Four Breaks in the BBB
1. Portions of hypothalamus Secrete hypothalamic hormones
2. Posterior lobe of pituitary gland Secretes hormones ADH and oxytocin
3. Pineal gland Pineal secretions
4. Choroid plexus Where special ependymal cells maintain blood–CSF barrier
14-2 Brain Protection and Support Protection and Support
o Meninges stabilize brain in cranial cavity o Cerebrospinal fluid protects against sudden movement o CSF provides nutrients and removes wastes o Blood–brain barrier and blood–CSF barrier
Selectively isolate brain from chemicals in blood that might disrupt
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neural function
14-3 The Medulla Oblongata The Medulla Oblongata
o Allows brain and spinal cord to communicate o Coordinates complex autonomic reflexes o Controls visceral functions o Nuclei in the medulla
Autonomic nuclei control visceral activities Sensory and motor nuclei of cranial nerves Relay stations along sensory and motor pathways
14-3 The Medulla Oblongata The Medulla Oblongata
o Includes three groups of nuclei 1. Autonomic nuclei 2. Sensory and motor nuclei of cranial nerves 3. Relay stations along sensory and motor pathways
14-3 The Medulla Oblongata Autonomic Nuclei of the Medulla Oblongata
o Reticular formation Gray matter with embedded nuclei Regulates autonomic functions
14-3 The Medulla Oblongata Autonomic Nuclei of the Medulla Oblongata
o Reflex centers Control peripheral systems
o Cardiovascular centers Cardiac center Control blood flow through peripheral tissues
o Respiratory rhythmicity centers Set pace for respiratory movements
14-3 The Medulla Oblongata Sensory and Motor Nuclei of the Medulla Oblongata
o Associated with 5 of 12 cranial nerves (VIII, IX, X, XI, XII)
14-3 The Medulla Oblongata Relay Stations of the Medulla Oblongata
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o Nucleus gracilis and nucleus cuneatus Pass somatic sensory information to thalamus
o Solitary nucleus Receives visceral sensory information
o Olivary nuclei (olives) Relay information about somatic motor commands
14-4 The Pons The Pons
1. Sensory and motor nuclei of cranial nerves (V, VI, VII, VIII) 2. Nuclei involved with respiration
Apneustic center and pneumotaxic center o Modify respiratory rhythmicity center activity
3. Nuclei that process and relay information to and from cerebellum 4. Ascending, descending, and transverse tracts
Transverse fibers (axons) o Link nuclei of pons with opposite cerebellar hemisphere
14-5 The Cerebellum Functions of the Cerebellum
1. Adjusts postural muscles 2. Fine-tunes conscious and subconscious movements
14-5 The Cerebellum Structures of the Cerebellum
o Folia Surface of cerebellum Highly folded neural cortex
o Anterior and posterior lobes Separated by primary fissure
o Cerebellar hemispheres Separated at midline by vermis
14-5 The Cerebellum Structures of the Cerebellum
o Vermis Narrow band of cortex
o Flocculonodular lobe Below fourth ventricle
14-5 The Cerebellum Structures of the Cerebellum
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o Purkinje cells Large, branched cells Found in cerebellar cortex Receive input from up to 200,000 synapses
o Arbor vitae (“tree of life”) Highly branched, internal white matter of cerebellum Cerebellar nuclei embedded in arbor vitae
o Relay information to Purkinje cells
14-5 The Cerebellum Structures of the Cerebellum
o The peduncles Tracts link cerebellum with brain stem, cerebrum, and spinal cord
o Superior cerebellar peduncles o Middle cerebellar peduncles o Inferior cerebellar peduncles
14-5 The Cerebellum Disorders of the Cerebellum
o Ataxia Damage from trauma or stroke Intoxication (temporary impairment) Disturbs muscle coordination
14-6 The Midbrain Structures of the Midbrain
o Tectum Two pairs of sensory nuclei (corpora quadrigemina)
o Superior colliculus (visual) o Inferior colliculus (auditory)
o Tegmentum Red nucleus (many blood vessels) Substantia nigra (pigmented gray matter)
14-6 The Midbrain Structures of the Midbrain
o Cerebral peduncles Nerve fiber bundles on ventrolateral surfaces Contain:
1. Descending fibers to cerebellum 2. Motor command fibers
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14-7 The Diencephalon The Diencephalon
o Integrates sensory information and motor commands o Thalamus, epithalamus, and hypothalamus
The pineal gland o Found in posterior epithalamus o Secretes hormone melatonin
14-7 The Diencephalon The Thalamus
o Filters ascending sensory information for primary sensory cortex o Relays information between basal nuclei and cerebral cortex o
14-7 The Diencephalon The Thalamus
o The third ventricle Separates left thalamus and right thalamus Interthalamic adhesion
o Projection of gray matter o Extends into ventricle from each side
14-7 The Diencephalon The Thalamus
o Thalamic nuclei Are rounded masses that form thalamus Relay sensory information to basal nuclei and cerebral cortex
14-7 The Diencephalon Five Groups of Thalamic Nuclei
1. Anterior group Anterior nuclei
o Part of limbic system (emotions) 2. Medial group
Provides awareness of emotional states 3. Ventral group
Relays sensory information
14-7 The Diencephalon Five Groups of Thalamic Nuclei
4. Posterior group
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Pulvinar nucleus (sensory) Lateral geniculate nucleus (visual) Medial geniculate nucleus (auditory)
5. Lateral group Affects emotional states Integrates sensory information
14-7 The Diencephalon The Hypothalamus
o Mammillary bodies Process olfactory and other sensory information Control reflex eating movements
o Infundibulum A narrow stalk Connects hypothalamus to pituitary gland
o Tuberal area Located between the infundibulum and mammillary bodies Helps control pituitary gland function
14-7 The Diencephalon Eight Functions of the Hypothalamus
1. Provides subconscious control of skeletal muscle 2. Controls autonomic function 3. Coordinates activities of nervous and endocrine systems 4. Secretes hormones
Antidiuretic hormone (ADH) by supraoptic nucleus Oxytocin (OT; OXT) by paraventricular nucleus
14-7 The Diencephalon Eight Functions of the Hypothalamus
5. Produces emotions and behavioral drives The feeding center (hunger) The thirst center (thirst)
6. Coordinates voluntary and autonomic functions 7. Regulates body temperature
Preoptic area of hypothalamus 8. Controls circadian rhythms (day–night cycles)
Suprachiasmatic nucleus
14-8 The Limbic System The Limbic System
o Is a functional grouping that: Establishes emotional states
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Links conscious functions of cerebral cortex with autonomic functions of brain stem
Facilitates memory storage and retrieval
14-8 The Limbic System Components of the Limbic System
o Amygdaloid body Acts as interface between the limbic system, the cerebrum, and
various sensory systems o Limbic lobe of cerebral hemisphere
Cingulate gyrus Dentate gyrus Parahippocampal gyrus Hippocampus
14-8 The Limbic System Components of the Limbic System
o Fornix Tract of white matter Connects hippocampus with hypothalamus
o Anterior nucleus of the thalamus Relays information from mammillary body to cingulate gyrus
o Reticular formation Stimulation or inhibition affects emotions (rage, fear, pain, sexual
arousal, pleasure)
14-9 The Cerebrum The Cerebrum
o Is the largest part of the brain o Controls all conscious thoughts and intellectual functions o Processes somatic sensory and motor information
14-9 The Cerebrum Gray Matter
o In cerebral cortex and basal nuclei
White Matter o Deep to basal cortex o Around basal nuclei
14-9 The Cerebrum Structures of the Cerebrum
o Gyri of neural cortex
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Increase surface area (number of cortical neurons) o Insula (“island” of cortex)
Lies medial to lateral sulcus o Longitudinal fissure
Separates cerebral hemispheres o Lobes
Divisions of hemispheres
14-9 The Cerebrum Structures of the Cerebrum
o Central sulcus divides: Anterior frontal lobe from posterior parietal lobe
o Lateral sulcus divides: Frontal lobe from temporal lobe
o Parieto-occipital sulcus divides: Parietal lobe from occipital lobe
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
14-9 The Cerebrum White Matter of the Cerebrum
o Association fibers Connections within one hemisphere
o Commissural fibers Bands of fibers connecting two hemispheres
o Projection fibers Connect cerebrum with lower areas
14-9 The Cerebrum Association Fibers
o Arcuate fibers Are short fibers Connect one gyrus to another
o Longitudinal fasciculi Are longer bundles Connect frontal lobe to other lobes in same hemisphere
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14-9 The Cerebrum Commissural Fibers
o Corpus callosum o Anterior commissure
14-9 The Cerebrum Projection Fibers
o Pass through diencephalon o Link cerebral cortex with:
Diencephalon, brain stem, cerebellum, and spinal cord o Internal capsule
All ascending and descending projection fibers
14-9 The Cerebrum The Basal Nuclei
o Are masses of gray matter o Are embedded in white matter of cerebrum o Direct subconscious activities
14-9 The Cerebrum Anatomy of Basal Nuclei
o Caudate nucleus Curving, slender tail
o Lentiform nucleus Globus pallidus Putamen
14-9 The Cerebrum Functions of Basal Nuclei
o Involved with: The subconscious control of skeletal muscle tone The coordination of learned movement patterns (walking, lifting)
14-9 The Cerebrum Motor and Sensory Areas of the Cortex
o Central sulcus separates motor and sensory areas o Motor areas
Precentral gyrus of frontal lobe o Directs voluntary movements
Primary motor cortex o Is the surface of precentral gyrus
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Pyramidal cells o Are neurons of primary motor cortex
14-9 The Cerebrum Motor and Sensory Areas of the Cortex
o Sensory areas Postcentral gyrus of parietal lobe
o Receives somatic sensory information (touch, pressure, pain, vibration, taste, and temperature)
Primary sensory cortex o Surface of postcentral gyrus
14-9 The Cerebrum Special Sensory Cortexes
o Visual cortex Information from sight receptors
o Auditory cortex Information from sound receptors
o Olfactory cortex Information from odor receptors
o Gustatory cortex Information from taste receptors
14-9 The Cerebrum Association Areas
o Sensory association areas Monitor and interpret arriving information at sensory areas of cortex
o Somatic sensory association area Interprets input to primary sensory cortex (e.g., recognizes and
responds to touch)
14-9 The Cerebrum Sensory Association Areas
o Visual association area Interprets activity in visual cortex
o Auditory association area Monitors auditory cortex
o Somatic motor association area (premotor cortex) Coordinates motor responses (learned movements)
14-9 The Cerebrum
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Integrative Centers o Are located in lobes and cortical areas of both cerebral hemispheres o Receive information from association areas o Direct complex motor or analytical activities
14-9 The Cerebrum General Interpretive Area
o Also called Wernicke’s area o Present in only one hemisphere o Receives information from all sensory association areas o Coordinates access to complex visual and auditory memories
14-9 The Cerebrum Other Integrative Areas
o Speech center Is associated with general interpretive area Coordinates all vocalization functions
o Prefrontal cortex of frontal lobe Integrates information from sensory association areas Performs abstract intellectual activities (e.g., predicting consequences
of actions)
14-9 The Cerebrum Interpretive Areas of Cortex
o Brodmann areas Patterns of cellular organization in cerebral cortex
14-9 The Cerebrum Hemispheric Lateralization
o Functional differences between left and right hemispheres o Each cerebral hemisphere performs certain functions that are not
ordinarily performed by the opposite hemisphere
14-9 The Cerebrum The Left Hemisphere
o In most people, left brain (dominant hemisphere) controls: Reading, writing, and math Decision making Speech and language
The Right Hemisphere o Right cerebral hemisphere relates to:
Senses (touch, smell, sight, taste, feel)
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Recognition (faces, voice inflections)
14-9 The Cerebrum Monitoring Brain Activity
o Brain activity is assessed by an electroencephalogram (EEG) Electrodes are placed on the skull Patterns of electrical activity (brain waves) are printed out
14-9 The Cerebrum Four Categories of Brain Waves
1. Alpha waves 2. Beta waves 3. Theta waves 4. Delta waves
14-9 The Cerebrum Alpha Waves
o Found in healthy, awake adults at rest with eyes closed
Beta Waves o Higher frequency o Found in adults concentrating or mentally stressed
14-9 The Cerebrum Theta Waves
o Found in children o Found in intensely frustrated adults o May indicate brain disorder in adults
Delta Waves o During sleep o Found in awake adults with brain damage
14-9 The Cerebrum Synchronization
o A pacemaker mechanism Synchronizes electrical activity between hemispheres
o Brain damage can cause desynchronization
Seizure o Is a temporary cerebral disorder o Changes the electroencephalogram o Symptoms depend on regions affected
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14-10 Cranial Nerves Cranial Nerves
o 12 pairs connected to brain
Four Classifications of Cranial Nerves 1. Sensory nerves: carriers of somatic sensory information, including touch,
pressure, vibration, temperature, and pain 2. Special sensory nerves: carriers of sensations such as smell, sight,
hearing, and balance 3. Motor nerves: axons of somatic motor neurons 4. Mixed nerves: mixture of motor and sensory fibers
14-10 Cranial Nerves Cranial Nerves
o Are classified by primary functions o May also have important secondary functions
Distributing autonomic fibers to peripheral ganglia o The 12 cranial nerve groups are identified by:
Primary function Origin Pathway Destination
14-10 Cranial Nerves Olfactory Nerves (I)
o Primary function: Special sensory (smell)
o Origin: Receptors of olfactory epithelium
o Pathway: Olfactory foramina in cribriform plate of ethmoid
o Destination: Olfactory bulbs
14-10 Cranial Nerves Olfactory Nerve Structures
o Olfactory bulbs Located on either side of crista galli
o Olfactory tracts Axons of postsynaptic neurons Leading to cerebrum
14-10 Cranial Nerves
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Optic Nerves (II) o Primary function:
Special sensory (vision) o Origin:
Retina of eye o Pathway:
Optic canals of sphenoid o Destination:
Diencephalon via optic chiasm
14-10 Cranial Nerves Optic Nerve Structures
o Optic chiasm Where sensory fibers converge And cross to opposite side of brain
o Optic tracts Reorganized axons Leading to lateral geniculate nuclei
14-10 Cranial Nerves Oculomotor Nerves (III)
o Primary function: Motor (eye movements)
o Origin: Midbrain
o Pathway: Superior orbital fissures of sphenoid
14-10 Cranial Nerves Oculomotor Nerves (III)
o Destination: Somatic motor
o Superior, inferior, and medial rectus muscles o Inferior oblique muscle o Levator palpebrae superioris muscle
Visceral motor o Intrinsic eye muscles
14-10 Cranial Nerves Oculomotor Nerve Structures
o Oculomotor nerve Controls four of six eye-movement muscles Delivers autonomic fibers to ciliary ganglion
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o Ciliary ganglion controls intrinsic muscles of iris and lens
14-10 Cranial Nerves The Trochlear Nerves (IV)
o Primary function: Motor (eye movements)
o Origin: Midbrain
o Pathway: Superior orbital fissure of sphenoid
o Destination: Superior oblique muscle
14-10 Cranial Nerves The Abducens Nerves (VI)
o Primary function: Motor (eye movements)
o Origin: Pons
o Pathway: Superior orbital fissures of sphenoid
o Destination: Lateral rectus muscle
14-10 Cranial Nerves The Trigeminal Nerves (V)
o Primary function: Mixed (sensory and motor) to face
o Origin: Ophthalmic branch (sensory)
o Orbital structures o Nasal cavity o Skin of forehead, upper eyelid, and eyebrow o Part of nose
14-10 Cranial Nerves The Trigeminal Nerves (V)
o Origin: Maxillary branch (sensory)
o Lower eyelid o Upper lip, gums, and teeth o Cheek and nose o Palate and part of pharynx
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14-10 Cranial Nerves The Trigeminal Nerves (V)
o Origin: Mandibular branch (sensory)
o Lower gums, teeth, and lips o Palate and part of tongue
Mandibular branch (motor) o Motor nuclei of pons
14-10 Cranial Nerves The Trigeminal Nerves (V)
o Pathway: Ophthalmic branch
o Superior orbital fissure Maxillary branch
o Foramen rotundum Mandibular branch
o Foramen ovale
14-10 Cranial Nerves The Trigeminal Nerves (V)
o Destination: Sensory nerves
o Sensory nuclei in pons Motor nerves of mandibular branch
o Muscles of mastication
14-10 Cranial Nerves Trigeminal Nerve Structures
o Trigeminal nerves Largest cranial nerves With three major branches
o Semilunar ganglion Contains cell bodies of sensory neurons
14-10 Cranial Nerves The Facial Nerves (VII)
o Primary function: Mixed (sensory and motor) to face
o Origin: Sensory
o Taste receptors on anterior 2/3 of tongue
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Motor o Motor nuclei of pons
o Pathway: Internal acoustic meatus to facial canals (stylomastoid foramina)
14-10 Cranial Nerves The Facial Nerves (VII)
o Destination: Sensory
o Sensory nuclei of pons Somatic motor
o Muscles of facial expression Visceral motor
o Tear and nasal mucous glands o Submandibular and sublingual salivary glands
14-10 Cranial Nerves Facial Nerve Structures
o Facial nerve branches Temporal Zygomatic Buccal Mandibular Cervical branches
14-10 Cranial Nerves Facial Nerve Structures
o Geniculate ganglia Hold cell bodies of sensory neurons
o Pterygopalatine ganglia Postganglionic fibers innervate glands (lacrimal, nasal cavity, and
pharynx) o Submandibular ganglia
Innervate salivary glands
14-10 Cranial Nerves The Vestibulocochlear Nerves (VIII)
o Primary function: Special sensory
o Vestibular branch Balance and equilibrium
o Cochlear branch Hearing
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14-10 Cranial Nerves The Vestibulocochlear Nerves (VIII)
o Origin: Receptors of inner ear
o Pathway: Internal acoustic meatus of temporal bones
o Destination: Vestibular and cochlear nuclei of pons and medulla oblongata
14-10 Cranial Nerves Vestibulocochlear Nerve Structures
o Vestibular branch Originates at receptors of vestibule (balance) Connects to vestibular nuclei of pons and medulla oblongata
o Cochlear branch Originates at sensors of cochlea (hearing) Connects with cochlear nuclei of pons and medulla oblongata
14-10 Cranial Nerves The Glossopharyngeal Nerves (IX)
o Primary function: Mixed (sensory and motor) to head and neck
14-10 Cranial Nerves The Glossopharyngeal Nerves (IX)
o Origins: Sensory
o Posterior 1/3 of tongue o Part of pharynx and palate o Carotid arteries
Motor o Motor nuclei of medulla oblongata
14-10 Cranial Nerves The Glossopharyngeal Nerves (IX)
o Pathway: Jugular foramina between occipital and temporal bones
o Destination: Sensory
o Sensory nuclei of medulla oblongata Somatic motor
o Nerves involved in swallowing
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Visceral motor o Parotid salivary gland
14-10 Cranial Nerves Glossopharyngeal Nerve Structures
o Superior and inferior ganglion Sensory neurons of tongue and pharynx
o Otic ganglion Synapse visceral motor fibers
14-10 Cranial Nerves The Vagus Nerves (X)
o Primary function: Mixed (sensory and motor) Widely distributed in thorax and abdomen
14-10 Cranial Nerves The Vagus Nerves (X)
o Origins: Sensory
o Part of pharynx o Auricle and external acoustic meatus o Diaphragm o Visceral organs of thoracic and abdominopelvic cavities
Motor o Motor nuclei in medulla oblongata
14-10 Cranial Nerves The Vagus Nerves (X)
o Pathway: Jugular foramina Between occipital and temporal bones
14-10 Cranial Nerves The Vagus Nerves (X)
o Destination: Sensory
o Sensory nuclei and autonomic centers of medulla oblongata Visceral motor
o Muscles of the palate and pharynx o Muscles of the digestive, respiratory, and cardiovascular systems in
thoracic and abdominal cavities
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14-10 Cranial Nerves Vagus Nerve Structures
o Vagus nerves Branch and radiate extensively
o Superior (jugular) ganglion and inferior (nodose) ganglion Hold sensory neurons
14-10 Cranial Nerves The Accessory Nerves (XI)
o Primary function: Motor to muscles of neck and upper back
o Origin: Motor nuclei of spinal cord and medulla oblongata
14-10 Cranial Nerves The Accessory Nerves (XI)
o Pathway: Jugular foramina between occipital and temporal bones
o Destination: Internal branch
o Voluntary muscles of palate, pharynx, and larynx External branch
o Sternocleidomastoid and trapezius muscles
14-10 Cranial Nerves Accessory Nerve Structures
o Spinal root Motor fibers that originate in anterior gray horns of first five cervical
segments of spinal cord o Cranial root
Motor fibers that originate in medulla oblongata
14-10 Cranial Nerves Accessory Nerve Structures
o Internal branch Joins the vagus nerve
o External branch Controls muscles of neck and back
14-10 Cranial Nerves The Hypoglossal Nerves (XII)
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o Primary function: Motor (tongue movements)
o Origin: Motor nuclei of medulla oblongata
o Pathway: Hypoglossal canals of occipital bone
o Destination: Muscles of tongue
14-10 Cranial Reflexes Cranial Reflexes
o Monosynaptic and polysynaptic reflex arcs o Involve sensory and motor fibers of cranial nerves o Clinically useful to check cranial nerve for brain damage