the adult human brain - houston community college

PowerPoint® Lecture Presentations prepared by

Jason LaPres

Lone Star College—North Harris

14 The Brain and Cranial Nerves

An Introduction to the Brain and Cranial Nerves

• The Adult Human Brain

• 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

14-1 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)

14-1 The Brain

• Cerebrum

• 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

• Second largest part of brain

• Coordinates repetitive body movements

• Two hemispheres

• Covered with cerebellar cortex

Figure 14-1 An Introduction to Brain Structures and Functions

CEREBRUM

• Conscious thought processes,

• Memory storage and processing • Conscious and subconscious regulation

of skeletal muscle contractions

intellectual functions

CEREBELLUM

• Coordinates complex somatic motor patterns

other somatic motor centers in brain and spinal cord

Fissures

Left cerebral

hemisphere

• Adjusts output of

Spinal cord

14-1 The Brain

• Diencephalon

• Located under cerebrum and cerebellum

• Links cerebrum with brain stem

• Three divisions of the diencephalon

1. Left thalamus

2. Right thalamus

3. Hypothalamus

14-1 The Brain

• Diencephalon

• Thalamus

• Relays and processes sensory information

• Hypothalamus

• Hormone production

• Emotion

• Autonomic function

14-1 The Brain

• Diencephalon

• Pituitary gland

• Major endocrine gland

• Connected to hypothalamus

• Interfaces nervous and endocrine systems

14-1 The Brain

• The Brain Stem

• Processes information between:

• Spinal cord and cerebrum or cerebellum

• Includes:

• Midbrain

• Pons

• Medulla oblongata

14-1 The Brain

• 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

14-1 The Brain

• Medulla Oblongata

• Connects brain to spinal cord

• Relays information

• Regulates autonomic functions

• Heart rate, blood pressure, and digestion

Figure 14-1 An Introduction to Brain Structures and Functions

DIENCEPHALON

THALAMUS

• Relay and processing centers for sensory

information

• Centers controlling

HYPOTHALAMUS

emotions, autonomic

functions, and

hormone production

MIDBRAIN

• Generation of reflexive

and auditory data

somatic motor responses

consciousness

MEDULLA OBLONGATA

function (cardiovascular, respiratory, and

digestive system activities)

• Relays sensory information to thalamus and to other portions of the brain stem

• Autonomic centers for regulation of visceral

Brain stem • Processing of visual

• Maintenance of

• Relays sensory information to cerebellum and thalamus • Subconscious somatic and visceral motor centers

14-1 The Brain

• Ventricles of the Brain

• Each cerebral hemisphere contains one large lateral

ventricle

• Separated by a thin medial partition (septum

pellucidum)

14-1 The Brain

• Third ventricle

• Ventricle of the diencephalon

• Lateral ventricles communicate with third ventricle

• Via interventricular foramen (foramen of Monro)

14-1 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 midbrain called the cerebral

aqueduct

Figure 14-2a Ventricles of the Brain

Cerebral hemispheres

Medulla oblongata

Spinal cord Central canal

Ventricular system, lateral view

Lateral ventricles

Interventricular foramen

Third ventricle

Cerebral aqueduct

Fourth ventricle

Ventricles of the Brain

Figure 14-2b Ventricles of the Brain

Lateral ventricles

Interventricular foramen

Third ventricle

Cerebral aqueduct

Fourth ventricle

Ventricles of the Brain

Cerebral hemispheres

Central canal Cerebellum

Ventricular system, anterior view

14-1 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

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

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

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

Cranium (skull)

Cerebellum

Medulla oblongata

Spinal cord

A lateral view of the brain, showing its

position in the cranium and the organization

of the meninges

Cerebral cortex

Dura mater (endosteal layer)

Dural sinus

Dura mater (meningeal layer)

Subdural space

Arachnoid mater

Subarachnoid space

Arachnoid trabeculae

Pia mater

Cerebral cortex

• 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

• 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

Figure 14-4a The Formation and Circulation of Cerebrospinal Fluid

Choroid plexus

of third ventricle

Cerebral

aqueduct

Lateral aperture

Choroid plexus of

fourth ventricle

Arachnoid mater

Subarachnoid space

Dura mater

Filum terminale

Spinal cord

Central canal

Superior

sagittal

Extension of choroid

plexus into

lateral ventricle

Arachnoid

granulations

Median aperture

Figure 14-4b The Formation and Circulation of Cerebrospinal Fluid

Cerebral

cortex

The relation-

ship of the

arachnoid

granulations

and dura

mater.

Subarachnoid

Arachnoid

Subdural

Dura mater

(meningeal

layer)

Arachnoid

trabeculae

movement

Arachnoid

granulation

Dura mater

(endosteal

layer)

Cranium Superior

sagittal sinus

• 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 21–23 Arteries of the Neck and Head

Figure 21–24a Arteries of the Brain

Figure 21–24b Arteries of the Brain

Figure 21–29a Major Veins of the Head, Neck, and Brain

Figure 21–29b Major Veins of the Head, Neck, and Brain

Figure 21–29c 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

14-3 The Medulla Oblongata

• 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

Cerebral peduncle

Diencephalon

Optic tract

Lateral geniculate nucleus

Midbrain

Cerebellar peduncles

Medial geniculate nucleus

Superior colliculus

Inferior colliculus

Inferior cerebellar peduncle

Middle cerebellar peduncle

Superior cerebellar peduncle

Cranial nerves

Medulla

oblongata

Thalamus

N VI N VII

N VIII N IX N X N XI

Spinal cord

Spinal

nerve C1

Spinal

nerve C2

Lateral view

Figure 14-5b The Diencephalon and Brain Stem

Optic chiasm

Thalamus

Optic tract

Cerebral

peduncle

Mamillary

Infundibulum

Cranial nerves

N VIII

Medulla oblongata

Ventral roots of spinal nerves C1 and C2

Spinal cord

Anterior view

Figure 14-5c The Diencephalon and Brain Stem

Choroid plexus in roof

of fourth ventricle

Choroid plexus

Thalamus

Third ventricle

Pineal gland

Superior colliculi

Inferior colliculi

Inferior

Middle

Superior

Cerebellar peduncles

Corpora quadrigemina

Cerebral peduncle

Dorsal roots

of spinal nerves

C1 and C2

Posterior view

• The Medulla Oblongata

• Includes three groups of nuclei

1. Autonomic nuclei

2. Sensory and motor nuclei of cranial nerves

3. Relay stations along sensory and motor pathways

• Autonomic Nuclei of the Medulla Oblongata

• Reticular formation

• Gray matter with embedded nuclei

• Regulates autonomic functions

• Autonomic Nuclei of the Medulla Oblongata

• 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)

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

Figure 14-6c The Medulla Oblongata and Pons

Tracts

Ascending tracts Descending tracts

Transverse fibers

Respiratory Centers

Pneumotaxic center

Apneustic center

Cerebellum

Fourth ventricle

Reticular formation

Medulla oblongata

Olivary nucleus

Lateral view

Midbrain

Medulla

oblongata

Spinal cord

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

• Folia

• Surface of cerebellum

• Highly folded neural cortex

• Anterior and posterior lobes

• Separated by primary fissure

• Cerebellar hemispheres

• Separated at midline by vermis

Figure 14-7a The Cerebellum

Primary

fissure

Right Hemisphere

of Cerebellum

Left Hemisphere

of Cerebellum

The posterior, superior surface of the cerebellum, showing

major anatomical landmarks and regions

Posterior

lobe Folia

Figure 14-7a The Cerebellum

Left Hemisphere

of Cerebellum Right Hemisphere

of Cerebellum

Vermis

Anterior lobe

Primary fissure

Posterior lobe

The posterior, superior surface of the cerebellum,

showing major anatomical landmarks and regions

Figure 14-7b The Cerebellum

Midbrain

Anterior lobe

Pons Cerebellar Peduncles

Superior cerebellar

peduncle

Middle cerebellar

peduncle

Inferior cerebellar

peduncle

Medulla oblongata Flocculonodular lobe

Choroid plexus of

the fourth ventricle

Posterior

Cerebellar

cortex

Cerebellar

nucleus

A sectional view of the cerebellum, showing the arrangement of gray matter and white matter

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)

Figure 14-8a The Midbrain

Thalamus

Cerebral peduncle

Pineal gland

Red nucleus

Substantia nigra

Corpora quadrigemina

Superior colliculus

Inferior colliculus

Reticular formation

A posterior view. The underlying nuclei are colored only on the right.

Figure 14-8b The Midbrain

Cerebral peduncle

Substantia nigra

Red nucleus

Cerebral aqueduct

Superior colliculus

Tectum

Tegmentum

Cerebellum

A superior view of a transverse section at the level of the midbrain.

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 Thalamus

• The third ventricle

• Separates left thalamus and right thalamus

• Interthalamic adhesion

• Projection of gray matter

• Extends into ventricle from each side

Figure 14-9a The Thalamus

Frontal lobe

A lateral

view of the brain, color coded

to indicate the regions that

receive input from the thalamic

nuclei shown in part (b)

Parietal lobe

Occipital

Figure 14-10a The Hypothalamus in Sagittal Section

A diagrammatic view of the hypothalamus, showing the locations of major nuclei and centers

Suprachiasmatic nucleus

Autonomic centers (parasympathetic)

Paraventricular nucleus

Autonomic centers (sympathetic)

Supraoptic nucleus

Tuberal nuclei

Optic chiasm

Infundibulum

Pituitary gland

Thalamus

Preoptic area

Interthalamic adhesion

Hypothalamus

Mid- brain

Mamillary body

Tuberal area

Figure 14-10b The Hypothalamus in Sagittal Section

Choroid plexus

Pineal gland

Hypothalamus

Aqueduct of midbrain

Cerebellum

Fourth ventricle

Mamillary body

Thalamus (surrounds third ventricle)

Parietal lobe

The hypothalamus and adjacent portions of the brain

• 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

• 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

8. Controls circadian rhythms (day–night cycles)

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

• 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

• 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

• Reticular formation

• Stimulation or inhibition affects emotions (rage, fear,

pain, sexual arousal, pleasure)

Figure 14-11a The Limbic System

A diagrammatic sagittal section through the

cerebrum, showing the cortical areas associated

with the limbic system. The parahippocampal

gyrus is shown as though transparent to make

deeper limbic components visible.

Temporal lobe

of cerebrum

Anterior group of

thalamic nuclei

Hypothalamus

Mamillary body

Components of the

Limbic System in

the Diencephalon

Corpus

callosum Fornix

Pineal

Components of the Limbic

System in the Cerebrum

The region of the cerebral

hemisphere shown in green

is known as the limbic lobe.

Cingulate gyrus

(superior portion of

limbic lobe)

Parahippocampal

gyrus (inferior portion

of limbic lobe)

Hippocampus

Figure 14-11b The Limbic System

Anterior nucleus of thalamus

Hypothalamic nuclei

Olfactory tract

Amygdaloid body Hippocampus (with dentate gyrus)

Cingulate gyrus

Corpus callosum

Fornix

Mamillary body

Hypothalamus

Parahippocampal gyrus

A three-dimensional reconstruction of the limbic system, showing the relationships among the major components.

Table 14-7 The Limbic System

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

14-9 The Cerebrum

• Gray Matter

• In cerebral cortex and basal nuclei

• White Matter

• Deep to basal cortex

• Around basal nuclei

14-9 The Cerebrum

• Structures of the Cerebrum

• Gyri of neural cortex

• Increase surface area (number of cortical neurons)

• Longitudinal fissure

• Separates cerebral hemispheres

• Lobes

• Divisions of hemispheres

14-9 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

Figure 14-12a The Brain in Lateral View

Lateral sulcus

Medulla oblongata

FRONTAL

Central sulcus

TEMPORAL LOBE

Lateral view, cadaver brain

Cerebellum

OCCIPITAL

PARIETAL LOBE

Figure 14-12b The Brain in Lateral View

FRONTAL

Precentral

Central

sulcus

Postcentral

Lateral sulcus

PARIETAL LOBE

OCCIPITAL

TEMPORAL

Cerebellum

Medulla oblongata

Lateral view

Figure 14-12d The Brain in Lateral View

Central sulcus Postcentral gyrus

PARIETAL LOBE

OCCIPITAL

Parieto-

occipital sulcus

Cerebellum Pons

Medulla oblongata

Midsagittal section

TEMPORAL LOBE

FRONTAL

Precentral gyrus

Cingulate

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

• The Basal Nuclei

• Are masses of gray matter

• Are embedded in white matter of cerebrum

• Direct subconscious activities

14-9 The Cerebrum

• Anatomy of Basal Nuclei

• Caudate nucleus

• Curving, slender tail

• Lentiform nucleus

• Globus pallidus

• Putamen

Figure 14-14a The Basal Nuclei

Lentiform

nucleus

Tail of caudate

nucleus

Thalamus

Head of

caudate

nucleus

Amygdaloid

The relative

positions of the

basal nuclei in the

intact brain, lateral view

Figure 14-14b The Basal Nuclei

Head of caudate nucleus

Internal capsule

Putamen

Thalamus

Choroid plexus

Pineal gland

Lateral ventricle

(posterior horn)

Fornix

Third ventricle

Fornix (cut edge)

Septum pellucidum

Corpus callosum

Lateral ventricle

(anterior horn)

A horizontal section as seen in a dissection

Figure 14-14c The Basal Nuclei

Head of caudate

nucleus

Lateral

ventricle

Corpus callosum

Septum pellucidum

Internal capsule

Lateral sulcus

Tip of lateral

ventricle

Frontal section

Insula

Claustrum

Putamen

Globus

pallidus

Lentiform

nucleus

Amygdaloid body

14-9 The Cerebrum

• Functions of Basal Nuclei

• 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

• Central sulcus separates motor and sensory areas

• Motor areas

14-9 The Cerebrum

• Motor and Sensory Areas of the Cortex

• Sensory areas

• Primary sensory cortex

• Surface of postcentral gyrus

14-9 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

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

Major anatomical landmarks on the surface of

the left cerebral hemisphere. The lateral sulcus

has been pulled apart to expose the insula.

FRONTAL LOBE

Prefrontal cortex

Gustatory cortex

Insula

Lateral sulcus

Olfactory cortex

Somatic motor association area (premotor cortex)

Primary motor cortex (precentral gyrus)

Central sulcus Primary sensory cortex (postcentral gyrus)

PARIETAL LOBE

TEMPORAL LOBE

OCCIPITAL LOBE

Somatic sensory association area

Visual association area

Visual cortex

Auditory cortex

Auditory association area

14-9 The Cerebrum

• 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)

14-9 The Cerebrum

• 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)

14-9 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

14-9 The Cerebrum

• General Interpretive Area

• Also called Wernicke’s area

• Present in only one hemisphere

• Receives information from all sensory association

• Coordinates access to complex visual and auditory

memories

14-9 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)

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

General interpretive area

Frontal eye field

Speech center

Prefrontal cortex

The left hemisphere generally contains the

general interpretive area and the speech center.

The prefrontal cortex of each hemisphere is

involved with conscious intellectual functions.

14-9 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

14-9 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)

Figure 14-16 Hemispheric Lateralization

Left Cerebral Hemisphere

LEFT HAND

Prefrontal

cortex

Speech center

Writing

Auditory cortex

General interpretive center

(language and mathematical

calculation)

Visual cortex

(right visual field)

C O R P U S

C A L L O S U M

Figure 14-16 Hemispheric Lateralization

Right Cerebral Hemisphere

RIGHT HAND

Prefrontal

cortex

Anterior commissure

Analysis by touch

Auditory cortex

Spatial visualization

and analysis

Visual cortex

(left visual field)

C O R P U S

C A L L O S U M

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

Figure 14-18 Origins of the Cranial Nerves

Olfactory bulb: termination

of olfactory nerve (I)

Olfactory tract

Optic nerve (II)

Infundibulum

Oculomotor nerve (III)

Basilar artery

Vertebral artery

Cerebellum

Medulla oblongata

Spinal cord

Figure 14-18 Origins of the Cranial Nerves

Optic chiasm

Optic tract

Mamillary body

Trochlear nerve (IV)

Trigeminal nerve (V)

Abducens nerve (VI)

Vestibulocochlear

nerve (VIII)

Facial nerve (VII)

Glossopharyngeal

nerve (IX)

Vagus nerve (X)

Hypoglossal nerve (XII)

Accessory nerve (XI)

• Olfactory Nerves (I)

• Primary function:

• Special sensory (smell)

• Origin:

• Receptors of olfactory epithelium

• Pathway:

• Olfactory foramina in cribriform plate of ethmoid

• Destination:

• Olfactory bulbs

Figure 14-19 The Olfactory Nerve

Olfactory tract

(to olfactory cortex

of cerebrum)

Left olfactory

bulb (termination

of olfactory nerve)

OLFACTORY

NERVE (N I)

Olfactory

nerve fibers

Cribriform plate

of ethmoid

Olfactory

epithelium

• Optic Nerves (II)

• Special sensory (vision)

• Origin:

• Retina of eye

• Pathway:

• Optic canals of sphenoid

• Destination:

• 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

Figure 14-20 The Optic Nerve

Pituitary

Midbrain

Visual cortex

(in occipital lobes)

Optic projection

fibers

Optic tract

Optic chiasm

OPTIC NERVE

(N II)

Olfactory bulb

Olfactory tract

Lateral geniculate nucleus (in thalamus)

• Oculomotor Nerves (III)

• Motor (eye movements)

• Origin:

• Midbrain

• Pathway:

• Superior orbital fissures of sphenoid

• The Trochlear Nerves (IV)

• Motor (eye movements)

• Origin:

• Midbrain

• Pathway:

• Superior orbital fissure of sphenoid

• Destination:

• Superior oblique muscle

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

Superior

oblique

muscle

Trochlea

Superior

rectus

muscle

Levator

palpebrae

superioris

muscle

Inferior

rectus

muscle

Ciliary

ganglion

Lateral rectus

muscle (cut)

ABDUCENS

NERVE (N VI)

NERVE (N II) Optic

chiasm

OCULOMOTOR

NERVE (N III)

TROCHLEAR

NERVE (N IV)

Trigeminal

nerve (N V), cut

Vestibulocochlear

nerve (N VIII), cut

Facial nerve

(N VII), cut Medial

rectus

muscle

Inferior

oblique

muscle

• The Trigeminal Nerves (V)

• Mixed (sensory and motor) to face

• Origin:

• Ophthalmic branch (sensory)

• Orbital structures

• Nasal cavity

• Skin of forehead, upper eyelid, and eyebrow

• Part of nose

• Origin:

• Maxillary branch (sensory)

• Lower eyelid

• Upper lip, gums, and teeth

• Cheek and nose

• Palate and part of pharynx

• Origin:

• 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

Figure 14-22 The Trigeminal Nerve

Supra-orbital

nerves

Ciliary ganglion

Foramen

rotundum

Infra-orbital

Lingual nerve

Submandibular

ganglion

Mental nerve

Pterygopalatine

ganglion

Mandibular

branch

Otic ganglion

Foramen ovale

Maxillary

branch

TRIGEMINAL

NERVE (N V)

Semilunar

ganglion

Ophthalmic

branch

Superior orbital fissure

• The Facial Nerves (VII)

• 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)

• 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

• Facial Nerve Structures

• Facial nerve branches

• Temporal

• Zygomatic

• Buccal

• Mandibular

• Cervical branches

Figure 14-23a The Facial Nerve

Pterygopalatine

ganglion

Greater petrosal

Geniculate

ganglion

FACIAL

NERVE (N VII)

Posterior

auricular

branch

Stylomastoid

foramen

Chorda tympani nerve

(with mandibular

branch of N V)

Lingual branch

(with lingual nerve

of N V)

Submandibular

ganglion

Temporal

branch

Zygomatic

branches

Buccal

branch

Mandibular

branch

Cervical

branch

The origin and branches of the facial nerve

Figure 14-23b The Facial Nerve

Temporal

branch

Zygomatic

branch

Buccal branch

Mandibular

branch

Cervical branch

The superficial distribution

of the five major branches

of the facial nerve

• The Vestibulocochlear Nerves (VIII)

• Special sensory

• Vestibular branch

• Balance and equilibrium

• Cochlear branch

• Hearing

• The Vestibulocochlear Nerves (VIII)

• 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

Figure 14-24 The Vestibulocochlear Nerve

Tympanic cavity

(middle ear)

Semicircular

canals

Vestibular

branch (N VIII)

Facial nerve

(N VII),

Internal

acoustic

meatus

VESTIBULOCOCHLEAR

NERVE (N VIII)

Medulla

oblongata

Cochlear branch (N VIII) Cochlea Auditory tube Tympanic membrane

• The Glossopharyngeal Nerves (IX)

• Mixed (sensory and motor) to head and neck

• The Glossopharyngeal Nerves (IX)

• Origins:

• Sensory

• Posterior 1/3 of tongue

• Part of pharynx and palate

• Carotid arteries

• Motor

• Motor nuclei of medulla oblongata

Figure 14-25 The Glossopharyngeal Nerve

Otic ganglion

Inferior

(petrosal)

ganglion

Lingual

branch

Carotid body

Carotid sinus

Common carotid artery

Carotid sinus branch

Pharyngeal branches

Parotid salivary gland

Superior (jugular)

ganglion

Medulla oblongata

GLOSSOPHARYNGEAL

NERVE (N IX)

N VIII

• The Vagus Nerves (X)

• 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

• Vagus Nerve Structures

• Vagus nerves

• Branch and radiate extensively

• Superior (jugular) ganglion and inferior (nodose)

ganglion

• Hold sensory neurons

Figure 14-26 The Vagus Nerve

Superior

pharyngeal

branch

NERVE (N X)

Superior

laryngeal nerve

Internal branch

External branch

Inferior

ganglion

of vagus

Medulla oblongata

Auricular branch

to external ear

Superior ganglion

of vagus nerve

Pharyngeal branch

Superior laryngeal nerve

Figure 14-26 The Vagus Nerve

Recurrent

laryngeal nerve

Cardiac branches

Cardiac plexus

Right lung Left lung

Anterior vagal trunk

Spleen

Celiac plexus

Stomach

Pancreas

Small intestine

Hypogastric plexus

• The Accessory Nerves (XI)

• Motor to muscles of neck and upper back

• Origin:

• Motor nuclei of spinal cord and medulla oblongata

• The Accessory Nerves (XI)

• Pathway:

• Jugular foramina between occipital and temporal bones

• Destination:

• Internal branch

• Voluntary muscles of palate, pharynx, and larynx

• External branch

• Sternocleidomastoid and trapezius muscles

• The Hypoglossal Nerves (XII)

• Motor (tongue movements)

• Origin:

• Motor nuclei of medulla oblongata

• Pathway:

• Hypoglossal canals of occipital bone

• Destination:

• Muscles of tongue

Figure 14-27 The Accessory and Hypoglossal Nerves

HYPOGLOSSAL NERVE (N XII)

ACCESSORY NERVE (N XI)

Internal branch: to palatal,

pharyngeal, and laryngeal

muscles with vagus nerve

Intrinsic muscles of tongue

Styloglossus muscle

Genioglossus muscle

Geniohyoid muscle

Hyoglossus muscle

Hyoid bone

Thyrohyoid muscle

Sternohyoid muscle

Sternothyroid muscle

Trigeminal nerve (N V)

Medulla oblongata

Cranial root of N XI

Spinal

root of N XI

External

branch of N XI

Spinal cord

Omohyoid muscle

Sternocleidomastoid

muscle

Ansa cervicalis

(cervical plexus)

Trapezius muscle

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

Table 14-10 Cranial Reflexes

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