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Chapter 14: The Brain and Cranial Nerves
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)
14-1 The Brain
• Six Regions of the Brain
1. Cerebrum
2. Cerebellum
3. Diencephalon
4. Mesencephalon
5. Pons
6. Medulla oblongata
• Cerebrum
• Largest part of brain
• Controls higher mental functions
• Divided into left and right cerebral hemispheres
• Surface layer of gray matter (neural cortex)
• Neural cortex
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Also called cerebral cortex
Folded surface increases surface area
Elevated ridges (gyri)
Shallow depressions (sulci)
Deep grooves (fissures)
• Cerebellum
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• Second largest part of brain
• Coordinates repetitive body movements
• Two hemispheres
• Covered with cerebellar cortex
Diencephalon
• Located under cerebrum and cerebellum
• Links cerebrum with brain stem
• Three divisions of the diencephalon
1. Left thalamus
2. Right thalamus
3. Hypothalamus
• Thalamus
• Relays and processes sensory information
• Hypothalamus
• Hormone production
• Emotion
• Autonomic function
© 2012 Pearson Education, Inc.
• Diencephalon
• Pituitary gland
• Major endocrine gland
• Connected to hypothalamus
• Via infundibulum (stalk)
• Interfaces nervous and endocrine systems
• The Brain Stem
• Processes information between:
• Spinal cord and cerebrum or cerebellum
• Includes:
• Midbrain
• Pons
• Medulla oblongata
• 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
• Medulla Oblongata
• Connects brain to spinal cord
• Relays information
• Regulates autonomic functions
• Heart rate, blood pressure, and digestion
• Embryological Development
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Determines organization of brain structures
Neural tube
• Origin of brain
• Enlarges into three primary brain vesicles
1. Prosencephalon
2. Mesencephalon
3. Rhombencephalon
• Five Secondary Brain Vesicles
1. Telencephalon
2. Diencephalon
3. Mesencephalon
4. Metencephalon
5. Myelencephalon
• Origins of Brain Structures
• Diencephalon and mesencephalon persist
• Telencephalon
• Becomes cerebrum
• Metencephalon
• Forms cerebellum and pons
• Myelencephalon
• Becomes medulla oblongata
© 2012 Pearson Education, Inc.
• Ventricles of the Brain
• Origins of ventricles
• Neural tube encloses neurocoel
• Neurocoel expands to form chambers (ventricles) lined with ependyma
• Each cerebral hemisphere contains one large lateral ventricle
• Separated by a thin medial partition (septum pellucidum)
• Third ventricle
• Ventricle of the diencephalon
• Lateral ventricles communicate with third ventricle
• Via interventricular foramen (foramen of Monro)
• Fourth ventricle
• Extends into medulla oblongata
• Becomes continuous with central canal of the spinal cord
• Connects with third ventricle
• Via narrow canal in midbrain called the cerebral aqueduct
• 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
14-2 Brain Protection and Support
• Physical Protection of the Brain
• Bones of the cranium
• Cranial meninges
• Cerebrospinal fluid
• Biochemical Isolation
• Blood–brain barrier
• The Cranial Meninges
• Have three layers
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1. Dura mater
2. Arachnoid mater
3. Pia mater
Are continuous with spinal meninges
Protect the brain from cranial trauma
Dura mater
• Inner fibrous layer (meningeal layer)
• Outer fibrous layer (endosteal layer) fused to periosteum
• Venous sinuses between two layers
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
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• Dural Folds
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Folded inner layer of dura mater
Extend into cranial cavity
Stabilize and support brain
Contain collecting veins (dural sinuses)
Three largest dural folds
1. Falx cerebri
2. Tentorium cerebelli
3. Falx cerebelli
• Falx Cerebri
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Projects between the cerebral hemispheres
Contains superior sagittal sinus and inferior sagittal sinus
• Tentorium Cerebelli
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Separates cerebellum and cerebrum
Contains transverse sinus
• Falx Cerebelli
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Divides cerebellar hemispheres below the tentorium cerebelli
• Cerebrospinal Fluid (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
• Choroid plexus
• 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
• 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
• CSF in subarachnoid space
• Arachnoid villi
• Extensions of subarachnoid space
• Extend through dura mater to superior sagittal sinus
• Arachnoid granulations
• Large clusters of villi
• Absorb CSF into venous circulation
• 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
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• Cerebrovascular Disease
• Disorders interfere with blood circulation to brain
• Stroke or cerebrovascular accident (CVA)
• Shuts off blood to portion of brain
• Neurons die
• 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), steroids, and prostaglandins
• Diffuse into interstitial fluid of brain and spinal cord
• Astrocytes control blood–brain barrier by:
• Releasing chemicals that control permeability of endothelium
• 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
• 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
• Protection and Support
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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
14-3 The Medulla Oblongata
• The Medulla Oblongata
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Allows brain and spinal cord to communicate
Coordinates complex autonomic reflexes
Controls visceral functions
Nuclei in the Medulla
• Autonomic nuclei control visceral activities
• Sensory and motor nuclei of cranial nerves
• Relay stations along sensory and motor pathways
• Includes three groups of nuclei
1. Autonomic nuclei
2. Sensory and motor nuclei of cranial nerves
3. Relay stations along sensory and motor pathways
© 2012 Pearson Education, Inc.
• Autonomic Nuclei of the Medulla Oblongata
• Reticular formation
• Gray matter with embedded nuclei
• Regulates autonomic functions
• Reflex centers
• Control peripheral systems
• Cardiovascular centers
• Cardiac center
• Control blood flow through peripheral tissues
• Respiratory rhythmicity centers
• Set pace for respiratory movements
• Sensory and Motor Nuclei of the Medulla Oblongata
• Associated with 5 of 12 cranial nerves (VIII, IX, X, XI, XII)
• Relay Stations of the Medulla Oblongata
• Nucleus gracilis and nucleus cuneatus
• Pass somatic sensory information to thalamus
• Solitary nucleus
• Receives visceral sensory information
• 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
• Modify respiratory rhythmicity center activity
3. Nucei that process and relay information to and from cerebellum
4. Ascending, descending, and transverse tracts
• Transverse fibers (axons)
• 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
• Structures of the Cerebellum
• Folia
• Surface of cerebellum
• Highly folded neural cortex
• Anterior and posterior lobes
• Separated by primary fissure
• Cerebellar hemispheres
• Separated at midline by vermis
• Vermis
• Narrow band of cortex
• Flocculonodular lobe
• Below fourth ventricle
© 2012 Pearson Education, Inc.
• Purkinje cells
• Large, branched cells
• Found in cerebellar cortex
• Receive input from up to 200,000 synapses
• Arbor vitae (“tree of life”)
• Highly branched, internal white matter of cerebellum
• Cerebellar nuclei embedded in arbor vitae
• Relay information to Purkinje cells
• The peduncles
• Tracts link cerebellum with brain stem, cerebrum, and spinal cord
• Superior cerebellar peduncles
• Middle cerebellar peduncles
• Inferior cerebellar peduncles
• Disorders of the Cerebellum
• Ataxia
• Damage from trauma or stroke
• Intoxication (temporary impairment)
• Disturbs muscle coordination
14-6 The Midbrain
• Structures of the Midbrain
• Tectum
• Two pairs of sensory nuclei (corpora quadrigemina)
• Superior colliculus (visual)
• Inferior colliculus (auditory)
• Tegmentum
• Red nucleus (many blood vessels)
• Substantia nigra (pigmented gray matter)
• Cerebral peduncles
• Nerve fiber bundles on ventrolateral surfaces
• Contain:
1. Descending fibers to cerebellum
2. Motor command fibers
14-7 The Diencephalon
• The Diencephalon
• Integrates sensory information and motor commands
• Thalamus, epithalamus, and hypothalamus
• The pineal gland
• Found in posterior epithalamus
• Secretes hormone melatonin
• The Thalamus
• Filters ascending sensory information for primary sensory cortex
• Relays information between basal nuclei and cerebral cortex
• The third ventricle separates left thalamus and right thalamus
• Interthalamic adhesion
• Projection of gray matter
• Extends into ventricle from each side
• Thalamic nuclei
• Are rounded masses that form thalamus
© 2012 Pearson Education, Inc.
• Relay sensory information to basal nuclei and cerebral cortex
• Five Groups of Thalamic Nuclei
1. Anterior group
• Anterior nuclei
• Part of limbic system (emotions)
2. Medial group
• Provides awareness of emotional states
3. Ventral group
• Relays sensory information
4. Posterior group
• Pulvinar nucleus (sensory)
• Lateral geniculate nucleus (visual)
• Medial geniculate nucleus (auditory)
5. Lateral group
• Affects emotional states
• Integrates sensory information
• The Hypothalamus
• Mamillary bodies
• Process olfactory and other sensory information
• Control reflex eating movements
• Infundibulum
• A narrow stalk
• Connects hypothalamus to pituitary gland
• Tuberal area
• Located between the infundibulum and mamillary bodies
• Helps control pituitary gland function
• Eight Functions of the Hypothalamus
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Provides subconscious control of skeletal muscle
Controls autonomic function
Coordinates activities of nervous and endocrine systems
Secretes hormones
• Antidiuretic hormone (ADH) by supraoptic nucleus
• Oxytocin (OT; OXT) by paraventricular nucleus
Produces emotions and behavioral drives
• The feeding center (hunger)
• The thirst center (thirst)
Coordinates voluntary and autonomic functions
Regulates body temperature
• Preoptic area of hypothalamus
Controls circadian rhythms (day–night cycles)
• Suprachiasmatic nucleus
14-8 The Limbic System
• The Limbic System
• Is a functional grouping that:
• Establishes emotional states
• Links conscious functions of cerebral cortex with autonomic functions of
brain stem
• Facilitates memory storage and retrieval
© 2012 Pearson Education, Inc.
• Components of the Limbic System
• Amygdaloid body
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• Acts as interface between the limbic system, the cerebrum, and various
sensory
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Limbic lobe of cerebral hemisphere
• Cingulate gyrus
• Dentate gyrus
• Parahippocampal gyrus
• Hippocampus
Fornix
• Tract of white matter
• Connects hippocampus with hypothalamus
Anterior nucleus of the thalamus
• Relays information from mamillary body to cingulate gyrus
Reticular formation
• Stimulation or inhibition affects emotions (rage, fear, pain, sexual
arousal, pleasure)
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
• Gray Matter
• In cerebral cortex and basal nuclei
• White Matter
• Deep to basal cortex
• Around basal nuclei
• Structures of the Cerebrum
• Gyri of neural cortex
• Increase surface area (number of cortical neurons)
• Insula (“island” of cortex)
• Lies medial to lateral sulcus
• Longitudinal fissure
• Separates cerebral hemispheres
• Lobes
• Divisions of hemispheres
• Central sulcus divides:
• Anterior frontal lobe from posterior parietal lobe
• Lateral sulcus divides:
• Frontal lobe from temporal lobe
• Parieto-occipital sulcus divides:
• Parietal lobe from occipital lobe
• 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
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not precise
© 2012 Pearson Education, Inc.
• White Matter of the Cerebrum
• Association fibers
• Connections within one hemisphere
• Commissural fibers
• Bands of fibers connecting two hemispheres
• Projection fibers
• Connect cerebrum with lower areas
• Association Fibers
• Arcuate fibers
• Are short fibers
• Connect one gyrus to another
• Longitudinal fasciculi
• Are longer bundles
• Connect frontal lobe to other lobes in same hemisphere
• Commissural Fibers
• Corpus callosum
• Anterior commissure
• Projection Fibers
• Pass through diencephalon
• Link cerebral cortex with:
• Diencephalon, brain stem, cerebellum, and spinal cord
• Internal capsule
• All ascending and descending projection fibers
• The Basal Nuclei
• Are masses of gray matter
• Are embedded in white matter of cerebrum
• Direct subconscious activities
• Anatomy of Basal Nuclei
• Caudate nucleus
• Curving, slender tail
• Lentiform nucleus
• Globus pallidus
• Putamen
• Functions of Basal Nuclei
• Involved with:
• The subconscious control of skeletal muscle tone
• The coordination of learned movement patterns (walking, lifting)
• Motor and Sensory Areas of the Cortex
• Central sulcus separates motor and sensory areas
• Motor areas
• Precentral gyrus of frontal lobe
• Directs voluntary movements
• Primary motor cortex
• Is the surface of precentral gyrus
• Pyramidal cells
• Are neurons of primary motor cortex
© 2012 Pearson Education, Inc.
• Sensory areas
• Postcentral gyrus of parietal lobe
• Receives somatic sensory information (touch, pressure, pain, vibration,
taste, and
temperature)
• Primary sensory cortex
• Surface of postcentral gyrus
• Special Sensory Cortexes
• Visual cortex
• Information from sight receptors
• Auditory cortex
• Information from sound receptors
• Olfactory cortex
• Information from odor receptors
• Gustatory cortex
• Information from taste receptors
• Association Areas
• Sensory association areas
• Monitor and interpret arriving information at sensory areas of cortex
• Somatic sensory association area
• Interprets input to primary sensory cortex (e.g., recognizes and responds
to touch)
• Sensory Association Areas
• Visual association area
• Interprets activity in visual cortex
• Auditory association area
• Monitors auditory cortex
• Somatic motor association area (premotor cortex)
• Coordinates motor responses (learned movements)
• Integrative Centers
• Are located in lobes and cortical areas of both cerebral hemispheres
• Receive information from association areas
• Direct complex motor or analytical activities
• General Interpretive Area
• Also called Wernicke’s area
• Present in only one hemisphere
• Receives information from all sensory association areas
• Coordinates access to complex visual and auditory memories
• Other Integrative Areas
• Speech center
• Is associated with general interpretive area
• Coordinates all vocalization functions
• Prefrontal cortex of frontal lobe
• Integrates information from sensory association areas
• Performs abstract intellectual activities (e.g., predicting consequences of
actions)
• Interpretive Areas of Cortex
• Brodmann areas
• Patterns of cellular organization in cerebral cortex
© 2012 Pearson Education, Inc.
• Hemispheric Lateralization
• Functional differences between left and right hemispheres
• Each cerebral hemisphere performs certain functions that are not ordinarily
performed by
the opposite hemisphere
• 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)
• Monitoring Brain Activity
• Brain activity is assessed by an electroencephalogram (EEG)
• Electrodes are placed on the skull
• Patterns of electrical activity (brain waves) are printed out
• Four Categories of Brain Waves
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1. Alpha waves
2. Beta waves
3. Theta waves
4. Delta waves
Alpha Waves
• Found in healthy, awake adults at rest with eyes closed
Beta Waves
• Higher frequency
• Found in adults concentrating or mentally stressed
Theta Waves
• Found in children
• Found in intensely frustrated adults
• May indicate brain disorder in adults
Delta Waves
• During sleep
• Found in awake adults with brain damage
Synchronization
• A pacemaker mechanism
• Synchronizes electrical activity between hemispheres
• Brain damage can cause desynchronization
• Seizure
• Is a temporary cerebral disorder
• Changes the electroencephalogram
• Symptoms depend on regions affected
© 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
• 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
• Olfactory Nerves (I)
• Primary function:
• Special sensory (smell)
• Origin:
• Receptors of olfactory epithelium
• Pathway:
• Olfactory foramina in cribriform plate of ethmoid
• Destination:
• Olfactory bulbs
• Olfactory Nerve Structures
• Olfactory bulbs
• Located on either side of crista galli
• Olfactory tracts
• Axons of postsynaptic neurons
• Leading to cerebrum
• Optic Nerves (II)
• Primary function:
• Special sensory (vision)
• Origin:
• Retina of eye
• Pathway:
• Optic canals of sphenoid
• Destination:
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Diencephalon via optic chiasm
Optic Nerve Structures
Optic chiasm
Where sensory fibers converge
And cross to opposite side of brain
Optic tracts
Reorganized axons leading to lateral geniculate nuclei
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Oculomotor Nerves (III)
Primary function:
Motor (eye movements)
Origin:
Midbrain
Pathway:
Superior orbital fissures of sphenoid
Destination:
Somatic motor
Superior, inferior, and medial rectus muscles
Inferior oblique muscle
Levator palpebrae superioris muscle
Visceral motor
Intrinsic eye muscles
Oculomotor Nerve Structures
Oculomotor nerve
Controls four of six eye-movement muscles
Delivers autonomic fibers to ciliary ganglion
Ciliary ganglion controls intrinsic muscles of iris and lens
The Trochlear Nerves (IV)
Primary function:
Motor (eye movements)
Origin:
Midbrain
Pathway:
Superior orbital fissure of sphenoid
Destination:
Superior oblique muscle
The Abducens Nerves (VI)
Primary function:
Motor (eye movements)
Origin:
Pons
Pathway:
Superior orbital fissures of sphenoid
Destination:
Lateral rectus muscle
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The Trigeminal Nerves (V)
Primary function:
Mixed (sensory and motor) to face
Origin:
Ophthalmic branch (sensory)
Orbital structures
Nasal cavity
Skin of forehead, upper eyelid, and eyebrow
Part of nose
Maxillary branch (sensory)
Lower eyelid
• Upper lip, gums, and teeth
• Cheek and nose
• Palate and part of pharynx
• Mandibular branch (sensory)
• Lower gums, teeth, and lips
• Palate and part of tongue
• Mandibular branch (motor)
• Motor nuclei of pons
• Pathway:
• Ophthalmic branch
• Superior orbital fissure
• Maxillary branch
• Foramen rotundum
• Mandibular branch
• Foramen ovale
• Destination:
• Sensory nerves
• Sensory nuclei in pons
• Motor nerves of mandibular branch
• Muscles of mastication
• Trigeminal Nerve Structures
• Trigeminal nerves
• Largest cranial nerves
• With three major branches
• Semilunar ganglion
• Contains cell bodies of sensory neurons
• The Facial Nerves (VII)
• Primary function:
• Mixed (sensory and motor) to face
• Origin:
• Sensory
• Taste receptors on anterior 2/3 of tongue
• Motor
• Motor nuclei of pons
• Pathway:
• Internal acoustic meatus to facial canals (stylomastoid foramina)
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• Destination:
• Sensory
• Sensory nuclei of pons
• Somatic motor
• Muscles of facial expression
• Visceral motor
• Tear and nasal mucous glands
• Submandibular and sublingual salivary glands
• Facial Nerve Structures
• Facial nerve branches
• Temporal
• Zygomatic
• Buccal
• Mandibular
• Cervical branches
• Geniculate ganglia
• Hold cell bodies of sensory neurons
• Pterygopalatine ganglia
• Postganglionic fibers innervate glands (lacrimal, nasal cavity, and
pharynx)
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Submandibular ganglia
Innervate salivary glands
The Vestibulocochlear Nerves (VIII)
Primary function:
Special sensory
Vestibular branch
Balance and equilibrium
Cochlear branch
Hearing
Origin:
Receptors of inner ear
Pathway:
Internal acoustic meatus of temporal bones
Destination:
Vestibular and cochlear nuclei of pons and medulla oblongata
Vestibulocochlear Nerve Structures
Vestibular branch
Originates at receptors of vestibule (balance)
Connects to vestibular nuclei of pons and medulla oblongata
Cochlear branch
Originates at sensors of cochlea (hearing)
Connects with cochlear nuclei of pons and medulla oblongata
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The Glossopharyngeal Nerves (IX)
Primary function:
Mixed (sensory and motor) to head and neck
Origins:
Sensory
Posterior 1/3 of tongue
Part of pharynx and palate
Carotid arteries
Motor
Motor nuclei of medulla oblongata
Pathway:
Jugular foramina between occipital and temporal bones
Destination:
Sensory
Sensory nuclei of medulla oblongata
Somatic motor
Nerves involved in swallowing
Visceral motor
Parotid salivary gland
Glossopharyngeal Nerve Structures
Superior and inferior ganglion
Sensory neurons of tongue and pharynx
Otic ganglion
Synapse visceral motor fibers
The Vagus Nerves (X)
Primary function:
Mixed (sensory and motor)
Widely distributed in thorax and abdomen
Origins:
Sensory
Part of pharynx
Auricle and external acoustic meatus
Diaphragm
Visceral organs of thoracic and abdominopelvic cavities
• Motor
• Motor nuclei in medulla oblongata
• Pathway:
• Jugular foramina
• Between occipital and temporal bones
• Destination:
• Sensory
• Sensory nuclei and autonomic centers of medulla oblongata
• Visceral motor
• Muscles of the palate and pharynx
• Muscles of the digestive, respiratory, and cardiovascular systems in
thoracic and
abdominal cavities
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• Vagus Nerve Structures
• Vagus nerves
• Branch and radiate extensively
• Superior (jugular) ganglion and inferior (nodose) ganglion
• Hold sensory neurons
• The Accessory Nerves (XI)
• Primary function:
• Motor to muscles of neck and upper back
• Origin:
• Motor nuclei of spinal cord and medulla oblongata
• Pathway:
• Jugular foramina between occipital and temporal bones
• Destination:
• Internal branch
• Voluntary muscles of palate, pharynx, and larynx
• External branch
• Sternocleidomastoid and trapezius muscles
• Accessory Nerve Structures
• Spinal root
• Motor fibers that originate in anterior gray horns of first five cervical
segments of spinal
cord
• Cranial root
• Motor fibers that originate in medulla oblongata
• Internal branch
• Joins the vagus nerve
• External branch
• Controls muscles of neck and back
• The Hypoglossal Nerves (XII)
• Primary function:
• Motor (tongue movements)
• Origin:
• Motor nuclei of medulla oblongata
• Pathway:
• Hypoglossal canals of occipital bone
• Destination:
• Muscles of tongue
14-10 Cranial Reflexes
• Cranial Reflexes
• Monosynaptic and polysynaptic reflex arcs
• Involve sensory and motor fibers of cranial nerves
• Clinically useful to check cranial nerve for brain damage
© 2012 Pearson Education, Inc.
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Chapter 14
Chapter 14 Outline - North Mac Schools
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