chapter 14 the brain and cranial nerves · 2020. 9. 16. · chapter 14 the brain and cranial nerves...

© 2015 Pearson Education, Inc.

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


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


o Thalamus Relays and processes sensory information

o Hypothalamus Hormone production Emotion Autonomic function


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


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


ependyma o Each cerebral hemisphere contains one large lateral ventricle

Separated by a thin medial partition (septum pellucidum)


o Third ventricle Ventricle of the diencephalon Lateral ventricles communicate with third ventricle

o Via interventricular foramen (foramen of Monro)


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


2. Arachnoid mater 3. Pia mater

o Are continuous with spinal meninges o Protect the brain from cranial trauma


o Dura mater Inner fibrous layer (meningeal layer) Outer fibrous layer (periosteal layer) fused to periosteum Venous sinuses between two layers


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


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


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


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


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


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


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


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


o Vermis Narrow band of cortex

o Flocculonodular lobe Below fourth ventricle



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


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


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


o The third ventricle Separates left thalamus and right thalamus Interthalamic adhesion

o Projection of gray matter o Extends into ventricle from each side


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


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


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


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


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


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


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)


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


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


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


o Ciliary ganglion controls intrinsic muscles of iris and lens

14-10 Cranial Nerves The Trochlear Nerves (IV)


o Origin: Midbrain

o Pathway: Superior orbital fissure of sphenoid

o Destination: Superior oblique muscle

14-10 Cranial Nerves The Abducens Nerves (VI)


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


o Origin: Maxillary branch (sensory)

o Lower eyelid o Upper lip, gums, and teeth o Cheek and nose o Palate and part of pharynx



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


o Pathway: Ophthalmic branch

o Superior orbital fissure Maxillary branch

o Foramen rotundum Mandibular branch

o Foramen ovale


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


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


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


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


o Pathway: Jugular foramina between occipital and temporal bones


o Sensory nuclei of medulla oblongata Somatic motor

o Nerves involved in swallowing


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


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


o Pathway: Jugular foramina Between occipital and temporal bones



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


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)


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

chapter 14 the brain and cranial nerves · 2020. 9. 16. · chapter 14 the brain and cranial nerves...

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