The Brain and Cranial Nerves

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14 The Brain and Cranial Nerves

PowerPoint® Lecture Presentations prepared by Jason LaPres Lone Star College—North Harris

• The Adult Human Brain

• Average weight about 1.4 kg (3 lb)

• 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)

• Cerebrum

• Neural cortex

• Also called cerebral cortex

• Folded surface increases surface area

• Elevated ridges (gyri)

• Shallow depressions (sulci)

• Deep grooves (fissures)

• Cerebellum

• Second largest part of brain

• Coordinates repetitive body movements

• Two hemispheres

• Covered with cerebellar cortex

Left cerebral hemisphere Gyri

CEREBRUM Sulci

• Conscious thought processes, Fissures intellectual functions • Memory storage and processing • Conscious and subconscious regulation of skeletal muscle contractions

CEREBELLUM • Coordinates complex Spinal somatic motor cord patterns • Adjusts output of other somatic motor centers in brain and spinal cord

• Diencephalon

• Located under cerebrum and cerebellum

• Links cerebrum with brain stem

• Three divisions of the diencephalon

1. Left thalamus

2. Right thalamus

3. Hypothalamus

• Diencephalon

• Thalamus

• Relays and processes sensory information

• Hypothalamus

• Hormone production

• Emotion

• Autonomic function

• Diencephalon

• Pituitary gland

• Major endocrine gland

• Connected to hypothalamus

• 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

THALAMUS • Relay and processing centers for sensory information

HYPOTHALAMUS • Centers controlling emotions, autonomic functions, and hormone production

MIDBRAIN Brain • Processing of visual stem and auditory data • Generation of reflexive somatic motor responses • Maintenance of consciousness

PONS • Relays sensory MEDULLA OBLONGATA information to cerebellum and • Relays sensory information to thalamus and thalamus to other portions of the brain stem • Subconscious • Autonomic centers for regulation of visceral somatic and visceral function (cardiovascular, respiratory, and motor centers digestive system activities) © 2012 Pearson Education, Inc. 14-1 The Brain

• Ventricles of the Brain

• Each cerebral hemisphere contains one large lateral ventricle

• Separated by a thin medial partition (septum pellucidum)

• Ventricles of the Brain

• Third ventricle

• Ventricle of the diencephalon

• Lateral ventricles communicate with third ventricle

• Via interventricular foramen (foramen of Monro)

• Ventricles of 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

Lateral ventricles

Interventricular foramen

Third ventricle

Cerebral aqueduct

Fourth ventricle Pons Medulla oblongata Spinal cord Central canal Ventricular system, lateral view © 2012 Pearson Education, Inc. Figure 14-2b Ventricles of the Brain Ventricles of Cerebral hemispheres the Brain

Lateral ventricles

Interventricular foramen

Third ventricle

Cerebral aqueduct

Fourth ventricle

Central canal Cerebellum

Ventricular system, anterior view

• 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

• 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

• The Cranial Meninges

• Dura mater

• Inner fibrous layer (meningeal layer)

• Outer fibrous layer (endosteal layer) fused to periosteum

• Venous sinuses between two layers

• The Cranial Meninges

• 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

© 2012 Pearson Education, Inc. Figure 14-3a The Relationship among the Brain, Cranium, and Meninges Dura mater (endosteal layer) Dural sinus Cranium (skull) Dura mater (meningeal layer) Subdural space Arachnoid mater Subarachnoid space Arachnoid trabeculae Pia mater Cerebral cortex

Cerebral cortex

Cerebellum Medulla oblongata Spinal cord

• 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

• Cerebrospinal Fluid (CSF)

• Choroid plexus

• Specialized ependymal cells and capillaries

• Secrete CSF into ventricles

• Produces about 500 mL of CSF/day

• Cerebrospinal Fluid (CSF)

• 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

• Cerebrospinal Fluid (CSF)

• CSF in subarachnoid space

• Arachnoid villi

• Extensions of subarachnoid space

• Extend through dura mater to superior sagittal sinus

Arachnoid Extension of choroid granulations plexus into lateral ventricle

Choroid plexus Superior of third ventricle sagittal sinus Cerebral aqueduct

Lateral aperture

Choroid plexus of fourth ventricle

Median aperture

Arachnoid mater Central canal Subarachnoid space

Spinal cord Dura mater

Filum terminale

Superior sagittal sinus Cranium Dura mater (endosteal layer)

Arachnoid granulation

Fluid movement

Arachnoid trabeculae

Cerebral Dura mater cortex (meningeal layer) The relation- Subdural ship of the space arachnoid granulations Arachnoid mater and dura Pia Subarachnoid mater. mater space

• 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

• Cerebrovascular Disease

• Disorders interfere with blood circulation to brain

• Stroke or cerebrovascular accident (CVA)

• Shuts off blood to portion of brain

• Neurons die

• 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

Diencephalon Cerebral peduncle Lateral geniculate nucleus Thalamus Optic tract Medial geniculate nucleus

Cranial nerves Midbrain N II Superior colliculus Inferior colliculus N III N IV Cerebellar peduncles Superior cerebellar peduncle N V

Pons Middle cerebellar peduncle N VI N VII Inferior cerebellar peduncle N VIII N IX N X N XI Medulla oblongata N XII Spinal

nerve C1

Spinal Spinal cord nerve C2

Cranial Thalamus nerves N II

N III Optic tract N IV Cerebral peduncle N V Mamillary Pons body N VI N VII N VIII N IX N X N XI

Third ventricle Pineal gland

Corpora quadrigemina Superior colliculi

Inferior colliculi N IV

Cerebral peduncle

Cerebellar peduncles Superior Middle

Choroid plexus in roof Inferior of fourth ventricle

Dorsal roots of spinal nerves

C1 and C2

• 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)

• 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

Tracts Respiratory Centers Ascending tracts Descending tracts Pneumotaxic center Apneustic center

Transverse fibers Cerebellum Midbrain Fourth ventricle

Pons Medulla oblongata

Reticular formation Medulla Olivary nucleus oblongata

Spinal cord

Lateral view

• 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

Primary Anterior fissure lobe

Posterior lobe Folia

Left Hemisphere Right Hemisphere of Cerebellum of Cerebellum

The posterior, superior surface of the cerebellum, showing major anatomical landmarks and regions

Vermis Anterior lobe

Primary fissure Folia

Posterior lobe

Left Hemisphere Right Hemisphere of Cerebellum of Cerebellum

The posterior, superior surface of the cerebellum, showing major anatomical landmarks and regions

Midbrain

Anterior lobe

Cerebellar Arbor Peduncles Pons vitae Superior cerebellar Cerebellar peduncle nucleus

Middle cerebellar Cerebellar peduncle cortex Inferior cerebellar Posterior peduncle lobe Choroid plexus of the fourth ventricle Medulla oblongata Flocculonodular lobe

• 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)

Pineal Thalamus gland

Red nucleus Substantia nigra

Corpora quadrigemina Cerebral Superior peduncle colliculus Inferior colliculus

ANTERIOR Cerebral Cerebellum peduncle Substantia nigra

Red nucleus Tegmentum Cerebral aqueduct

Superior colliculus

Tectum POSTERIOR

• 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

Frontal lobe Parietal lobe

Occipital lobe

A lateral view of the brain, color coded to indicate the regions that receive input from the thalamic nuclei shown in part (b)

Autonomic centers (sympathetic) Thalamus Paraventricular Interthalamic nucleus adhesion

Preoptic area

Autonomic centers Hypothalamus (parasympathetic)

Suprachiasmatic nucleus Supraoptic nucleus Mid- Tuberal nuclei brain Optic chiasm Tuberal area Mamillary Infundibulum body

Pituitary gland Pons

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

Parietal lobe

Choroid plexus

Thalamus (surrounds third ventricle)

Pineal gland

Hypothalamus

Aqueduct of midbrain

Cerebellum

Fourth ventricle

• 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)

• 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 gyrus • Reticular formation • Stimulation or inhibition affects emotions (rage, fear, pain, sexual arousal, pleasure)

Corpus Pineal callosum Fornix gland

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 Components of the limbic lobe) Limbic System in Parahippocampal the Diencephalon gyrus (inferior portion of limbic lobe) Anterior group of thalamic nuclei Hippocampus

Hypothalamus

Mamillary body Temporal lobe of cerebrum 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.

Cingulate gyrus

Corpus callosum

Anterior nucleus Fornix of thalamus

Hypothalamic Mamillary nuclei body

Olfactory Hypothalamus tract Parahippocampal gyrus

Amygdaloid body Hippocampus (with dentate gyrus)

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

• 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) • Longitudinal fissure • Separates cerebral hemispheres • Lobes • Divisions of hemispheres

• 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

Central sulcus

FRONTAL LOBE PARIETAL LOBE

OCCIPITAL LOBE Lateral sulcus

TEMPORAL LOBE Cerebellum Pons Medulla oblongata Lateral view, cadaver brain

Precentral Central Postcentral gyrus sulcus gyrus

FRONTAL PARIETAL LOBE LOBE

OCCIPITAL LOBE

TEMPORAL Lateral sulcus LOBE Cerebellum Pons Medulla oblongata Lateral view

Precentral gyrus Central sulcus Postcentral gyrus

Cingulate gyrus PARIETAL LOBE

FRONTAL LOBE Parieto- occipital sulcus

OCCIPITAL LOBE

Pons TEMPORAL LOBE Cerebellum

Medulla oblongata Midsagittal section

• 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

• 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

Head of Lentiform caudate nucleus nucleus

Tail of caudate nucleus Amygdaloid Thalamus body The relative positions of the basal nuclei in the intact brain, lateral view

Corpus callosum Head of caudate nucleus Lateral ventricle Internal capsule (anterior horn) Septum pellucidum Putamen Fornix (cut edge) Thalamus Choroid plexus Third ventricle

Pineal gland Fornix

Lateral ventricle (posterior horn)

A horizontal section as seen in a dissection

Lateral ventricle

Corpus callosum

Head of caudate Septum pellucidum nucleus Internal capsule Claustrum Lateral sulcus Insula Anterior Putamen commissure Lentiform Globus nucleus Tip of lateral pallidus ventricle Amygdaloid body Frontal section

• 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

• Motor and Sensory Areas of the Cortex

• Sensory areas

• 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

Primary motor cortex Central sulcus Primary sensory cortex (precentral gyrus) (postcentral gyrus)

Somatic motor association area (premotor cortex) PARIETAL LOBE

Somatic sensory association area FRONTAL LOBE Visual association area Prefrontal cortex OCCIPITAL LOBE Gustatory cortex Visual cortex Insula Auditory association area Lateral sulcus Auditory cortex TEMPORAL Olfactory cortex LOBE

Major anatomical landmarks on the surface of the left cerebral hemisphere. The lateral sulcus has been pulled apart to expose the insula.

• 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)

Frontal eye field

Speech center

Prefrontal General cortex interpretive area

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.

• 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)

Left Cerebral Hemisphere

LEFT HAND

Prefrontal cortex

Speech center

C O R P U Writing S C A Auditory cortex L L O S U General interpretive center M (language and mathematical calculation)

Visual cortex (right visual field)

Right Cerebral Hemisphere

RIGHT HAND

Prefrontal cortex

Anterior commissure C O R P U S Analysis by touch C A Auditory cortex L L O S U M Spatial visualization and analysis

Visual cortex (left visual field)

• 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

Olfactory bulb: termination of olfactory nerve (I)

Olfactory tract

Optic nerve (II)

Infundibulum

Oculomotor nerve (III)

Pons

Basilar artery

Vertebral artery

Cerebellum

Medulla oblongata

Spinal cord

Optic chiasm

Optic tract

Mamillary body

Trochlear nerve (IV)

Trigeminal nerve (V)

Abducens nerve (VI)

Facial nerve (VII)

Vestibulocochlear nerve (VIII)

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

Olfactory tract Left olfactory (to olfactory cortex bulb (termination of cerebrum) of olfactory nerve)

OLFACTORY NERVE (N I)

Olfactory nerve fibers

Cribriform plate Olfactory of ethmoid epithelium

• Optic Nerves (II) • Primary function: • 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

Eye Olfactory bulb Pituitary gland Olfactory tract

OPTIC NERVE (N II)

Optic chiasm

Optic tract

Lateral geniculate nucleus (in thalamus)

Optic projection Midbrain Visual cortex fibers (cut) (in occipital lobes)

• Oculomotor Nerves (III)

• Primary function: • Motor (eye movements) • Origin: • Midbrain • Pathway: • Superior orbital fissures of sphenoid

• The Trochlear Nerves (IV) • Primary function: • Motor (eye movements) • Origin: • Midbrain • Pathway: • Superior orbital fissure of sphenoid • Destination: • Superior oblique muscle

Superior OPTIC Optic OCULOMOTOR TROCHLEAR Superior rectus NERVE (N II) chiasm NERVE (N III) NERVE (N IV) oblique muscle muscle

Trochlea

Levator palpebrae superioris muscle Trigeminal nerve (N V), cut

Inferior Vestibulocochlear oblique nerve (N VIII), cut muscle

Facial nerve Inferior Medial (N VII), cut rectus Ciliary rectus Lateral rectus ABDUCENS muscle ganglion muscle muscle (cut) NERVE (N VI)

• 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

• The Trigeminal Nerves (V) • Origin:

• Maxillary branch (sensory) • Lower eyelid • Upper lip, gums, and teeth • Cheek and nose • Palate and part of pharynx

• The Trigeminal Nerves (V) • Origin:

• Mandibular branch (sensory) • Lower gums, teeth, and lips • Palate and part of tongue • Mandibular branch (motor) • Motor nuclei of pons

• The Trigeminal Nerves (V)

• Pathway:

• Ophthalmic branch

• Superior orbital fissure

• Maxillary branch

• Foramen rotundum

• Mandibular branch

• Foramen ovale

• The Trigeminal Nerves (V)

• Destination:

• Sensory nerves

• Sensory nuclei in pons

• Motor nerves of mandibular branch

• Muscles of mastication

Superior orbital fissure Supra-orbital Ophthalmic nerves branch Semilunar Ciliary ganglion ganglion Pons TRIGEMINAL Foramen NERVE (N V) rotundum Maxillary branch Infra-orbital nerve Foramen ovale Lingual nerve Otic ganglion

Submandibular Mandibular ganglion branch

Pterygopalatine ganglion Mental nerve

• 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)

• 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

Pterygopalatine Greater petrosal Geniculate FACIAL ganglion nerve ganglion NERVE (N VII)

Temporal branch

Pons

Zygomatic Posterior branches auricular branch Buccal branch Stylomastoid foramen Chorda tympani nerve Mandibular (with mandibular branch branch of N V) Lingual branch Cervical (with lingual nerve branch of N V)

Submandibular ganglion The origin and branches of 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)

• Primary function: • 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

Tympanic cavity Semicircular Vestibular Facial nerve Internal VESTIBULOCOCHLEAR (middle ear) canals branch (N VIII) (N VII), acoustic NERVE (N VIII) cut meatus

N V

Pons

N VI N VII

N IX N XII N X Medulla oblongata N XI

Tympanic membrane Auditory tube Cochlea Cochlear branch (N VIII)

• The Glossopharyngeal Nerves (IX) • Primary function: • 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

Pons N V N VII N VIII N VI GLOSSOPHARYNGEAL NERVE (N IX) Otic ganglion Medulla oblongata Inferior Superior (jugular) (petrosal) ganglion ganglion Parotid salivary gland Lingual branch Pharyngeal branches

Carotid sinus branch Carotid body

Carotid sinus

Common carotid artery

• The Vagus Nerves (X)

• Primary function: • Mixed (sensory and motor) • Widely distributed in thorax and abdomen

• The Vagus Nerves (X) • Origins: • Sensory • Part of pharynx • Auricle and external acoustic meatus • Diaphragm • Visceral organs of thoracic and abdominopelvic cavities • Motor • Motor nuclei in medulla oblongata

• The Vagus Nerves (X)

• Pathway: • Jugular foramina • Between occipital and temporal bones

• The Vagus Nerves (X) • 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

Superior VAGUS pharyngeal NERVE (N X) branch Pons

Medulla oblongata Auricular branch to external ear Superior ganglion Inferior of vagus nerve ganglion Pharyngeal branch of vagus nerve Superior laryngeal nerve Internal branch Superior laryngeal nerve External branch

Recurrent Cardiac branches laryngeal nerve Cardiac plexus

Right lung Left lung

Liver Anterior vagal trunk

Spleen Stomach Celiac plexus

Pancreas

Colon Small intestine Hypogastric plexus

• The Accessory Nerves (XI)

• Primary function: • 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) • Primary function: • Motor (tongue movements) • Origin: • Motor nuclei of medulla oblongata • Pathway: • Hypoglossal canals of occipital bone • Destination: • Muscles of tongue

HYPOGLOSSAL NERVE (N XII)

ACCESSORY NERVE (N XI) Trigeminal nerve (N V)

Internal branch: to palatal, Medulla oblongata pharyngeal, and laryngeal muscles with vagus nerve Cranial root of N XI

Intrinsic muscles of tongue Spinal root of N XI Styloglossus muscle External Genioglossus muscle branch of N XI

Geniohyoid muscle Spinal cord Hyoglossus muscle Hyoid bone Trapezius muscle

Thyrohyoid muscle Sternocleidomastoid muscle Sternohyoid muscle Ansa cervicalis Sternothyroid muscle (cervical plexus)

Omohyoid muscle

• Cranial Reflexes

• Monosynaptic and polysynaptic reflex arcs

• Involve sensory and motor fibers of cranial nerves

• Clinically useful to check cranial nerve for brain damage