Central Nervous System (CNS)

Cerebrum:

higher functions

Cerebellum:

coordination

Brainstem:

basic life functions

Dicencephalon:

hormonal control

Meninges:

• dura mater

• arachnoid mater

• pia mater

Afferent System:

sensory input

Efferent System:

motor output

Somatic Nervous System (SNS)

voluntary muscles 

Autonomic Nervous System (ANS)

involuntary control

Direction and Function of Afferent (Sensory)

Body→CNS Taste, pain, proprioception

Direction and Function of Efferent (Motor)

CNS→Body muscle activation

Sympathetic Function:

flight-or-flight (decrease salivation)

Parasympathetic Function:

rest and digest (increase salivation)

Cranial Nerves Overview:

• 12 paired nerves, numbered I–XII.

• Connected to brain base, exit via foramina.

• Can be afferent, efferent, or both

I Olfactory: Type

Afferent

I Olfactory: Funciton

smell

I Olfactory: Skull Exit

cribriform plate

II Optic: Type

Afferent

II Optic: Function

sight

II Optic: Skull exit

Optic Canal

III Oculomotor: Type

Efferent

III Oculomotor: Function

eye movement

III Oculomotor: Skull Exit

superior orbital fissure

IV Trochlear: Type

Efferent

IV Trochlear: Function

eye movement

IV Trochlear: Skull exit

superior orbital fissure

V Trigeminal: Type

both-afferent and efferent

V Trigeminal: Function

mastication, facial sensation

V Trigeminal: Skull exit

V1- Superior orbital fissure

V2-Foreman Rotundum

V3- Foreman Oval

VI Abducens: Type 

Efferent

VI Abducens: Function

eye movement

VI Abducens: Skull exit

superior orbital fissure

VII Facial: Type 

both

VII Facial: Function

facial expression, taste

VII Facial: Skull Exit

internal acoustic meatus. stylomastoid foramen

VIII Vestibulocochlear: Type

afferent

VIII Vestibulocochlear: Function

hearing, balance

VIII Vestibulocochlear: Skull exit

internal acoustic meatus

IX Glossopharyngeal: Type

both

IX Glossopharyngeal: Function

taste, pharynx, parotid gland

IX Glossopharyngeal: Skull Exit

jugular foramen

X Vagus: Type

both

X Vagus: Function

organs, pharynx, larynx

X Vagus: Skull Exit

Jugular foramen

XI Accessory: Type

efferent

XI Accessory: Function

neck muscles

XI Accessory: Skull exit

jugular foramen

XII Hypoglossal: Type 

efferent

XII Hypoglossal: Function:

tongue movement

XII Hypoglossal: Skull exit

hypoglossal canal

Cranial Nerve I – Olfactory:

• Type: Afferent (Sensory)

• Function: Transmits smell from nasal mucosa to the brain.

• Pathway: Enters skull via cribriform plate of the ethmoid bone → joins olfactory bulb.

• Clinical Note: Damage may affect sense of smell

Cranial Nerve II – Optic:

• Type: Afferent (Sensory)

• Function: Transmits visual information from retina to brain.

• Pathway: Travels through optic canal of the sphenoid bone.

• Clinical Note: Damage can lead to vision loss or visual field defects

Cranial Nerve III – Oculomotor:

• Type: Efferent (Motor)

• Function: Controls most eye muscles (movement), pupil constriction, and lens shape.

• Pathway: Runs in lateral wall of cavernous sinus, exits via superior orbital fissure.

• Clinical Note: Lesions may cause double vision, drooping eyelid (ptosis), or pupil

dilation.

Cranial Nerve IV – Trochlear:

• Type: Efferent (Motor)

• Function: Controls superior oblique muscle of the eye (downward and lateral

movement).

• Pathway: Also runs in lateral wall of cavernous sinus, exits via superior orbital

fissure.

• Clinical Note: Damage may result in difficulty looking down (especially when reading or

descending stairs).

Trigeminal Nerve (V) – Dental Focus V1 Ophthalmic:

Sensory – upper face

Smallest of three branches: it also branches into Frontal, Lacrimal, and Nasociliary

Trigeminal Nerve (V) – Dental Focus V2 Maxillary:

Sensory – mid-face

Trigeminal Nerve (V) – Dental Focus V3 Mandibular:

Mixed – lower face, mastication muscles. Is the entire efferent part of the trigeminal nerve

Clinical Note: Trigeminal Neuralgia (TN):

Severe facial pain, often maxillary or mandibular branches. Treatments include surgery, injections, medications

Cranial Nerve VI – Abducens:

• Efferent to lateral rectus muscle (eye movement).

• Exits via superior orbital fissure

Cranial Nerve VII – Facial:

• Efferent: Muscles of facial expression, posterior suprahyoid muscles, parasympathetic to

lacrimal and salivary glands.

• Afferent: Taste from anterior 2/3 of tongue, small patch of skin behind ear.

• Travels through internal acoustic meatus, facial canal, and exits via stylomastoid

foramen.

• Dental relevance: Innervates facial muscles and passes through parotid gland

Cranial Nerve VIII – Vestibulocochlear

• Afferent for hearing and balance.

• Originates in inner ear, enters skull via internal acoustic meatus

Cranial Nerve IX – Glossopharyngeal

• Efferent: Stylopharyngeus muscle, parasympathetic to parotid gland.

• Afferent: Taste and sensation from posterior tongue, oropharynx.

• Passes through jugular foramen.

• Otic ganglion involved in parasympathetic relay

Cranial Nerve X – Vagus

• Efferent: Muscles of soft palate, pharynx, larynx; parasympathetic to thoracic/abdominal

organs.

• Afferent: Taste from epiglottis, skin around ear.

• Exits via jugular foramen.

• Dental relevance: Innervates pharyngeal structures; involved in vasovagal response

(fainting).

Cranial Nerve XI – Accessory:

• Efferent to trapezius and sternocleidomastoid, also soft palate and pharynx.

• Exits via jugular foramen.

• Important for head and neck movement

Cranial Nerve XII – Hypoglossal

• Efferent to intrinsic and extrinsic tongue muscles.

• Exits via hypoglossal canal.

• Dental relevance: Controls tongue movement.