The Brain and Cranial Nerves - Napa Valley College · 14 The Brain and Cranial Nerves PowerPoint®...

Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

C h a p t e r

14

The Brain

and Cranial Nerves

PowerPoint® Lecture Slides

prepared by Jason LaPres

Lone Star College - North Harris

Copyright © 2009 Pearson Education, Inc.,

publishing as Pearson Benjamin Cummings


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)


The Brain

Six Regions of the Brain

Cerebrum

Cerebellum

Diencephalon

Mesencephalon

Pons

Medulla oblongata

3D Peel-Away of the Brain

14Brain_3DPA_3D.mov


The Brain

Cerebrum

Largest part of brain

Controls higher mental functions

Divided into left and right cerebral

hemispheres

Surface layer of gray matter (neural cortex)


The Brain

Cerebrum

Neural cortex

Also called cerebral cortex

Folded surface increases surface area

Elevated ridges (gyri)

Shallow depressions (sulci)

Deep grooves (fissures)


The Brain

Cerebellum

Second largest part of brain

Coordinates repetitive body movements

Two hemispheres

Covered with cerebellar cortex


The Brain

Diencephalon

Located under cerebrum and cerebellum

Links cerebrum with brain stem

Three divisions

Left thalamus

Right thalamus

Hypothalamus


The Brain

Diencephalon

Thalamus

Relays and processes sensory information

Hypothalamus

Hormone production

Emotion

Autonomic function

Pituitary gland

Major endocrine gland

Connected to hypothalamus

Via infundibulum (stalk)

Interfaces nervous and endocrine systems


The Brain

The Brain Stem

Processes information between

Spinal cord and cerebrum or cerebellum

Includes

Mesencephalon

Pons

Medulla oblongata


The Brain

The Brain Stem

Mesencephalon

Also called midbrain

Processes sight, sound, and associated reflexes

Maintains consciousness

Pons

Connects cerebellum to brain stem

Is involved in somatic and visceral motor control


The Brain

The Brain Stem

Medulla oblongata

Connects brain to spinal cord

Relays information

Regulates autonomic functions:

– heart rate, blood pressure, and digestion


The Brain

Figure 14–1 An Introduction to Brain Structures and Functions.


The Brain

Embryological Development

Determines organization of brain structures

Neural tube

Origin of brain

Enlarges into three primary brain vesicles

– prosencephalon

– mesencephalon

– rhombencephalon


The Brain

Five Secondary Brain Vesicles

Telencephalon

Diencephalon

Mesencephalon

Metencephalon

Myelencephalon


The Brain

Origins of Brain Structures

Diencephalon and mesencephalon persist

Telencephalon:

Becomes cerebrum

Metencephalon

Forms cerebellum and pons

Myelencephalon

Becomes medulla oblongata


The Brain


The Brain

Ventricles of the Brain

Origins of ventricles

Neural tube encloses neurocoel

Neurocoel expands to form chambers (ventricles) lined with

ependymal cells

Each cerebral hemisphere contains one large lateral

ventricle

Separated by a thin medial partition (septum pellucidum)


The Brain


Third ventricle

Ventricle of the diencephalon

Lateral ventricles communicate with third ventricle:

– via interventricular foramen (foramen of Monro)


The Brain


Fourth ventricle

Extends into medulla oblongata

Becomes continuous with central canal of the

spinal cord

Connects with third ventricle:

– via narrow canal in mesencephalon

– aqueduct of midbrain


The Brain

Figure 14–2 Ventricles of the Brain.


The Brain

The brain is a large, delicate mass of neural tissue

containing internal passageways and chambers filled

with cerebrospinal fluid

Each of the six major brain regions has specific functions

Ascending from the medulla oblongata to the cerebrum,

brain functions become more complex and variable

Conscious thought and intelligence are produced in the

neural cortex of the cerebral hemispheres


Brain Protection and Support

Physical protection

Bones of the cranium

Cranial meninges

Cerebrospinal fluid

Biochemical isolation

Blood–brain barrier



The Cranial Meninges

Have three layers:

Dura mater

Arachnoid mater

Pia mater

Are continuous with spinal meninges

Protect the brain from cranial trauma



The Cranial Meninges

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



Dural Folds

Folded inner layer of dura mater

Extend into cranial cavity

Stabilize and support brain

Contain collecting veins (dural sinuses)

Falx cerebri, tentorium cerebelli, and falx cerebelli



Dural Folds

Falx cerebri

Projects between the cerebral hemispheres

Contains superior sagittal sinus and inferior sagittal

sinus

Tentorium cerebelli

Separates cerebellum and cerebrum

Contains transverse sinus

Falx cerebelli

Divides cerebellar hemispheres below the tentorium cerebelli



Figure 14–3a The Relationship among the Brain, Cranium, and

Meninges.



Figure 14–3b The Relationship among the Brain, Cranium, and

Meninges.



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 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



Figure 14–4 The Formation and Circulation of Cerebrospinal Fluid.



Figure 14–4a The Formation and Circulation of Cerebrospinal Fluid.



Figure 14–4b The Formation and Circulation of Cerebrospinal Fluid.



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



Figure 21–22 Arteries of the Neck and Head.



Figure 21–23 Arteries of the Brain.



Figure 21–28 Major Veins of the Head, Neck, and Brain.



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

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

Surround capillaries of choroid plexus

Limits movement of compounds transferred

Allows chemical composition of blood and CSF to

differ



Four Breaks in the BBB

Portions of hypothalamus

Secrete hypothalamic hormones

Posterior lobe of pituitary gland

Secretes hormones ADH and oxytocin

Pineal glands

Pineal secretions

Choroid plexus

Where special ependymal cells maintain blood–

CSF barrier



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


The Medulla Oblongata


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



Figure 14–5a The Diencephalon and Brain Stem.



Figure 14–5b The Diencephalon and Brain Stem.



Figure 14–5c The Diencephalon and Brain Stem.




Includes three groups of nuclei

Autonomic nuclei

Sensory and motor nuclei of cranial nerves

Relay stations along sensory and motor pathways



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

sets 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



Figure 14–6a The Medulla Oblongata and Pons.



Figure 14–6b The Medulla Oblongata and Pons.


The Pons

The Pons

Links cerebellum with mesencephalon,

diencephalon, cerebrum, and spinal cord

Sensory and motor nuclei of cranial nerves V,

VI, VII, VIII


The Pons

The Pons

Nuclei involved with respiration

Apneustic center and pneumotaxic center:

– modify respiratory rhythmicity center activity

Nuclei and tracts

Process and relay information to and from

cerebellum

Ascending, descending, and transverse tracts:

– transverse fibers (axons):

» link nuclei of pons with opposite cerebellar

hemisphere


The Pons

Figure 14–6a The Medulla Oblongata and Pons.


The Pons

Figure 14–6b The Medulla Oblongata and Pons.


The Pons

Figure 14–6c The Medulla Oblongata and Pons.


The Pons


The Cerebellum

Functions of the Cerebellum

Adjusts postural muscles

Fine-tunes conscious and subconscious

movements


The Cerebellum

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


The Cerebellum


Purkinje cells

Large, branched cells

Found in cerebellar cortex

Receive input from up to 200,000 synapses

Arbor vitae

Highly branched, internal white matter of cerebellum

Cerebellar nuclei: embedded in arbor vitae:

– relay information to Purkinje cells


The Cerebellum


The peduncles

Tracts link cerebellum with brain stem, cerebrum, and spinal

cord:

– superior cerebellar peduncles

– middle cerebellar peduncles

– inferior cerebellar peduncles


The Cerebellum

Disorders of the Cerebellum

Ataxia

Damage from trauma or stroke

Intoxication (temporary impairment)

Disturbs muscle coordination


The Cerebellum

Figure 14–7a The Cerebellum.


The Cerebellum

Figure 14–7b The Cerebellum.


The Cerebellum


The Mesencephalon

Structures of the Mesencephalon

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)


The Mesencephalon

Structures of the Mesencephalon

Cerebral peduncles

Nerve fiber bundles on ventrolateral surfaces

Contain:

– descending fibers to cerebellum

– motor command fibers


The Mesencephalon

Figure 14–8a The Mesencephalon.


The Mesencephalon

Figure 14–8b The Mesencephalon.


The Mesencephalon


The Diencephalon

Integrates sensory information and motor

commands

Thalamus, epithalamus, and hypothalamus

The pineal gland

Found in posterior epithalamus

Secretes hormone melatonin


The Diencephalon

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 (or intermediate mass):

– projection of gray matter

– extends into ventricle from each side


The Diencephalon

The Thalamus

Thalamic nuclei

Are rounded masses that form thalamus

Relay sensory information to basal nuclei and

cerebral cortex


The Diencephalon

Five Groups of Thalamic Nuclei

Anterior group

Anterior nuclei

Part of limbic system (emotions)

Medial group

Provides awareness of emotional states

Ventral group

Relays sensory information


The Diencephalon

Five Groups of Thalamic Nuclei

Posterior group

Pulvinar nucleus (sensory)

Lateral geniculate nucleus (visual)

Medial geniculate nucleus (auditory)

Lateral group

Affects emotional states

Integrates sensory information


The Diencephalon

Figure 14–9 The Thalamus.


The Diencephalon

Figure 14–9a The Thalamus.


The Diencephalon

Figure 14–9b The Thalamus.


The Diencephalon

[INSERT Table. 14.5]


The Diencephalon

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


The Diencephalon

Figure 14–10a The Hypothalamus in Sagittal Section.


The Diencephalon

Figure 14–10b The Hypothalamus in Sagittal Section.


The Diencephalon

Eight Functions of the Hypothalamus

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


The Diencephalon

Eight Functions of the Hypothalamus

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


The Diencephalon


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


The Limbic System

Components of the Limbic System

Amygdaloid body

Acts as interface between the limbic system, the

cerebrum, and various sensory systems

Limbic lobe of cerebral hemisphere

Cingulate gyrus

Dentate gyrus

Parahippocampal gyrus

Hippocampus


The Limbic System

Components of the Limbic System

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)


The Limbic System

Figure 14–11a The Limbic System.


The Limbic System

Figure 14–11b The Limbic System.


The Limbic System


The Cerebrum

The Cerebrum

Is the largest part of the brain

Controls all conscious thoughts and

intellectual functions

Processes somatic sensory and motor

information


The Cerebrum

Gray matter

In cerebral cortex and basal nuclei

White matter

Deep to basal cortex

Around basal nuclei


The Cerebrum

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


The Cerebrum

Structures of the Cerebrum

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


The Cerebrum

Figure 14–12a The Brain in Lateral View.


The Cerebrum

Figure 14–12b The Brain in Lateral View.


The Cerebrum

Figure 14–12c The Brain in Lateral View.


The Cerebrum

Three Functional Principles of the Cerebrum

Each cerebral hemisphere receives sensory

information from, and sends motor commands to, the

opposite side of the body

The two hemispheres have different functions,

although their structures are alike

Correspondence between a specific function and a

specific region of cerebral cortex is not precise


The Cerebrum

White Matter of the Cerebrum

Association fibers

Commissural fibers

Projection fibers


The Cerebrum


Association fibers

Connections within one hemisphere:

– arcuate fibers:

» are short fibers

» connect one gyrus to another

– longitudinal fasciculi:

» are longer bundles

» connect frontal lobe to other lobes in same hemisphere


The Cerebrum


Commissural fibers

Bands of fibers connecting two hemispheres:

– corpus callosum

– anterior commissure


The Cerebrum


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 Cerebrum

Figure 14–13a Fibers of the White Matter of the Cerebrum.


The Cerebrum

Figure 14–13b Fibers of the White Matter of the Cerebrum.


The Cerebrum

The Basal Nuclei

Also called cerebral nuclei

Are masses of gray matter

Are embedded in white matter of cerebrum

Direct subconscious activities


The Cerebrum

Structures of Basal Nuclei

Caudate nucleus

Curving, slender tail

Lentiform nucleus

Globus pallidus

Putamen


The Cerebrum

Figure 14–14a The Basal Nuclei.


The Cerebrum

Figure 14–14b The Basal Nuclei.


The Cerebrum

Figure 14–14c The Basal Nuclei.


The Cerebrum

Functions of Basal Nuclei

Involved with

The subconscious control of skeletal muscle tone

The coordination of learned movement patterns

(walking, lifting)


The Cerebrum

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


The Cerebrum

Motor and Sensory Areas of the Cortex

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


The Cerebrum

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


The Cerebrum

Figure 14–15a Motor and Sensory Regions of the Cerebral Cortex.


The Cerebrum

Association Areas

Sensory association areas

Monitor and interpret arriving information at sensory areas of

cortex

Somatic motor association area (premotor cortex)

Coordinates motor responses (learned movements)


The Cerebrum

Sensory Association Areas

Somatic sensory association area

Interprets input to primary sensory cortex (e.g., recognizes

and responds to touch)

Visual association area

Interprets activity in visual cortex

Auditory association area

Monitors auditory cortex


The Cerebrum

Integrative Centers

Are located in lobes and cortical areas of both

cerebral hemispheres

Receive information from association areas

Direct complex motor or analytical activities


The Cerebrum

General Interpretive Area

Also called Wernicke area

Present in only one hemisphere

Receives information from all sensory association

areas

Coordinates access to complex visual and auditory

memories


The Cerebrum

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)


The Cerebrum

Figure 14–15b Motor and Sensory Regions of the Cerebral Cortex.


The Cerebrum

Interpretive Areas of Cortex

Brodmann areas

Patterns of cellular organization in cerebral cortex


The Cerebrum

Figure 14–15c Motor and Sensory Regions of the Cerebral Cortex.


The Cerebrum


The Cerebrum

Hemispheric Lateralization

Functional differences between left and right

hemispheres

Each cerebral hemisphere performs certain

functions that are not ordinarily performed by

the opposite hemisphere


The Cerebrum

The Left Hemisphere

In most people, left brain (dominant hemisphere)

controls

Reading, writing, and math

Decision making

Speech and language

The Right Hemisphere

Right cerebral hemisphere relates to

Senses (touch, smell, sight, taste, feel)

Recognition (faces, voice inflections)


The Cerebrum

Figure 14–16 Hemispheric Lateralization.


The Cerebrum

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


The Cerebrum

Four Categories of Brain 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


The Cerebrum

Figure 14–17a-d Brain Waves.


The Cerebrum

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


Cranial Nerves

12 pairs connected to brain

Four Classifications of Cranial Nerves

Sensory nerves: carry somatic sensory information,

including touch, pressure, vibration, temperature, and

pain

Special sensory nerves: carry sensations such as

smell, sight, hearing, balance

Motor nerves: axons of somatic motor neurons

Mixed nerves: mixture of motor and sensory fibers


Cranial Nerves

Cranial nerves are classified by primary

functions

May also have important secondary functions

Distributing autonomic fibers to peripheral ganglia

The 12 cranial nerve groups are identified by

Primary function

Origin

Pathway

Destination


Cranial Nerves

Figure 14–18 Origins of the Cranial Nerves.


Cranial Nerves

Olfactory Nerves (I)

Primary function

Special sensory (smell)

Origin

Receptors of olfactory epithelium

Pathway

Olfactory foramina in cribriform plate of ethmoid

Destination

Olfactory bulbs


Cranial Nerves

Olfactory Nerve Structures

Olfactory bulbs

Located on either side of crista galli

Olfactory tracts

Axons of postsynaptic neurons

Leading to cerebrum


Cranial Nerves

Figure 14–19 The Olfactory Nerve.


Cranial Nerves

Optic Nerves (II)

Primary function

Special sensory (vision)

Origin

Retina of eye

Pathway

Optic canals of sphenoid

Destination

Diencephalon via optic chiasm


Cranial Nerves

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


Cranial Nerves

Figure 14–20 The Optic Nerve.


Cranial Nerves

Oculomotor Nerves (III) Primary function

Motor (eye movements)

Origin Mesencephalon

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


Cranial Nerves

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


Cranial Nerves

The Trochlear Nerves (IV)

Primary function


Origin

Mesencephalon

Pathway

Superior orbital fissure of sphenoid

Destination

Superior oblique muscle


Cranial Nerves

The Abducens Nerves (VI)

Primary function


Origin

Pons

Pathway

Superior orbital fissures of sphenoid

Destination

Lateral rectus muscle


Cranial Nerves

Figure 14–21 Cranial Nerves Controlling the Extra-Ocular Muscles.


Cranial Nerves

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


Cranial Nerves


Origin

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


Cranial Nerves


Pathway

Ophthalmic branch:

– superior orbital fissure

Maxillary branch:

– foramen rotundum

Mandibular branch:

– foramen ovale


Cranial Nerves


Destination

Sensory nerves:

– sensory nuclei in pons

Motor nerves of mandibular branch:

– muscles of mastication


Cranial Nerves

Trigeminal Nerve Structures

Trigeminal nerves

Largest cranial nerves

With three major branches

Semilunar ganglion

Contains cell bodies of sensory neurons


Cranial Nerves

Figure 14–22 The Trigeminal Nerve.


Cranial Nerves

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)


Cranial Nerves

The Facial Nerves (VII)

Destination

Sensory:

– sensory nuclei of pons

Somatic motor:

– muscles of facial expression

Visceral motor:

– tear and nasal mucous glands

– submandibular and sublingual salivary glands


Cranial Nerves

Facial Nerve Structures

Facial nerve branches

Temporal

Zygomatic

Buccal

Mandibular

Cervical branches


Cranial Nerves

Facial Nerve Structures

Geniculate ganglia

Hold cell bodies of sensory neurons

Pterygopalatine ganglia

Postganglionic fibers innervate glands (lacrimal, nasal cavity,

and pharynx)

Submandibular ganglia

Innervate salivary glands


Cranial Nerves

Figure 14–23a The Facial Nerve.


Cranial Nerves

Figure 14–23b The Facial Nerve.


Cranial Nerves

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


Cranial Nerves

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


Cranial Nerves

Figure 14–24 The Vestibulocochlear Nerve.


Cranial Nerves

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


Cranial Nerves

The Glossopharyngeal Nerves (IX)

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


Cranial Nerves

Glossopharyngeal Nerve Structures

Superior and inferior ganglion

Sensory neurons of tongue and pharynx

Otic ganglion

Synapse visceral motor fibers


Cranial Nerves

Figure 14–25 The Glossopharyngeal Nerve.


Cranial Nerves

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


Cranial Nerves

The Vagus Nerves (X)

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


Cranial Nerves

Vagus Nerve Structures

Vagus nerves

Branch and radiate extensively

Superior (jugular) ganglion and inferior

(nodose) ganglion

Hold sensory neurons


Cranial Nerves

Figure 14–26 The Vagus Nerve.


Cranial Nerves

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


Cranial Nerves

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


Cranial Nerves

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


Cranial Nerves

Figure 14–27 The Accessory and Hypoglossal Nerves.


Cranial Nerves


Cranial Reflexes

Cranial Reflexes

Monosynaptic and polysynaptic reflex arcs

Involve sensory and motor fibers of cranial nerves

Clinically useful to check cranial nerve or brain

damage


Cranial Reflexes

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