LAB EXERCISE

11

CRANIAL NERVES

Cranial Nerves• Twelve pairs

of cranial nerves – That arise

from the brain

• Each nerve is identified by a Roman number– I through XII– and a name

Cranial Nerves• 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

Summary of Function of Cranial Nerves

Figure 13.5b

Cranial Nerves

• Four cranial nerves carry parasympathetic fibers that serve muscles and glands – Occulomotor (III)

– Facial (VII)

– Glossopharyngeal (IX)

– Vagus (X)

Cranial Nerves• Cranial Nerves

–The 12 cranial nerve groups are

identified by:

–Primary function

–Origin

–Pathway

–Destination

Cranial Nerves• Olfactory Nerves (I)

– Primary function: • Special sensory (smell)

– Origin: • Receptors of olfactory epithelium

Cranial Nerves• Olfactory Nerves (I)

– Pathway:

• Olfactory foramina in cribriform plate of ethmoid bone

– Destination:

• Olfactory bulbs

• To the olfactory tract

Cranial Nerve I - Olfactory Nerve

• Assesment– Have patient smell different items

• Damage to the ethmoid bone– Can cause anosmia

• Loss of smell

Cranial Nerves• Optic Nerves (II)

– Primary function:

• Special sensory (vision)

– Origin:

• Retina of eyes

Cranial Nerves• Optic Nerves (II)

– Pathway:

• Optic Canal of sphenoid bone

Cranial Nerves• Optic Nerves (II)

– Destination:

• Diencephalon via optic chiasm

• Optic tracts

– Leading to

lateral

geniculate

nuclei

• Olfactory Lobe

Cranial Nerve II - Optic Nerve• Assessment

– Test visual Acuity one eye at a time• Snellen eye chart

– Test peripheral vision one eye at a time• Cover one eye and have the patient look at your nose.• Move your finger to check superior and inferior fields

• Damage to the orbits or diseases in the nervous system can cause a loss of vision.

• Anopia

– Ipsilateral blindness due to sensory loss in the nerve

Cranial Nerves• Oculomotor Nerves (III)

– Primary function:

• Motor (eye movements)

– Controls four of six eye-movement

muscles

– Origin:

• Midbrain

– Pathway:

• Superior orbital fissures of sphenoid

Cranial Nerves• Oculomotor Nerves (III)

– Destination:

• Somatic motor

– Superior, inferior, and medial rectus muscles

– Inferior oblique muscle

– Levator palpebrae superioris muscle

• Oculomotor Nerves (III)– Visceral motor

• Parasympathetic Function• Ciliary ganglion

Cranial Nerves

Cranial Nerves• Oculomotor Nerves (III)

– Destination:

• Visceral motor

(Parasympathetic)

– Intrinsic eye muscles

» Cilliary Muscle

**Accommodation

of the lens

» Circular Muscles

**Constriction of iris

» Radial Muscles

**Dilation of iris

Cranial Nerve III - OculomotorAssessment

- To test the patients pupils

*Use a penlight and mm ruler

- Check to see where eyelid falls on the pupil

Damages

*Causes Ptosis

– Drooping of eyelid

*Causes diplopia

– Double vision

*Trouble with eye movements

Cranial Nerves

• The Trochlear Nerves (IV)

– Primary function:

• Motor (eye movements)

– Origin:

• Midbrain

Cranial Nerves• The Trochlear Nerves (IV)

– Pathway:• Superior orbital fissure of sphenoid

– Destination: • Superior oblique muscle

Cranial Nerve IV - Trochlear NerveAssessment

-Have patient follow your

finger while moving it to the

nose

Damages

*Causes

Diplopia

Paralysis

Strabismus

*Lazy Eye

Cranial Nerves• The Trigeminal Nerves (V)

– Primary function:

• Mixed Nerve

– Sensory

» Functions in

touch, pain, &

temperature

receptors of the

face

– Motor

» Innervates the

muscles of

mastication

Cranial Nerves• The Trigeminal Nerves

(V)

• Largest cranial

nerves

• With three major

branches

–Ophthalmic

–Maxillary

–Mandibular

Cranial Nerves• The Trigeminal

Nerves (V)

– Sensory

Innervation

– Semilunar ganglion

• Contains cell

bodies of

sensory neurons

Cranial Nerves• The Trigeminal Nerves (V)

– Ophthalmic Branch (V1)

• Sensory innervation to:

–Orbital structures

–Nasal cavity

–Skin of forehead

–Upper eyelid

–Eyebrow

–Part of nose

Cranial Nerves• The Trigeminal Nerves (V)

– Pathway:

• Ophthalmic Branch (V1)

– Superior Orbital Fissure

Cranial Nerves• The Trigeminal Nerves (V)

– Origin:

• Maxillary Branch (V2)

• Sensory innervation to

– Lower eyelid

– Upper

» Lip

» Gums

» Teeth

– Cheek and nose

– Palate and part of

pharynx

Cranial Nerves• The Trigeminal Nerves (V)

– Pathway:

• Maxillary branch (V2)

–Foramen Rotundum

Cranial Nerves• The Trigeminal Nerves (V)

• Mandibular Branch (V3)

– Sensory

innervation to:

» Lower

Gums

Teeth

Lips

» Palate

» Part of tongue

Lingual Nerve

Cranial Nerves

• The Trigeminal Nerves (V)

– Origin:

• Mandibular branch (V3)

• Motor innervation From

–Motor nuclei of pons

Cranial Nerves• The Trigeminal Nerves (V)

– Destination:

• Motor nerves of Mandibular Branch

– Muscles of mastication

» Chewing

Cranial Nerves• The Trigeminal Nerves (V)

– Pathway:

• Mandibular branch

– Foramen Ovale

Cranial Nerve V - TrigeminalAssessment

*To test for pain, touch & tempersture

-Safety pin & hot and cold objects

*Corneal reflex

- Cotton wisk

*To test motor function

-Clench teeth and move jaw

side to side

Cranial Nerve V - TrigeminalDamages

*Cause problems in chewing

*Loss of sensations of pain and

temperature

*Tic Douloureux

Trigeminal Neuralgia

*Severe pain from damage

of maxillary and

mandibular nerves

Cranial Nerves

• The Abducens Nerves (VI)– Primary function:

• Motor (eye movements)

– Origin: • Pons

Cranial Nerves• The Abducens Nerves (VI)

– Pathway:

• Superior orbital fissures of sphenoid

– Destination:

• Lateral rectus muscle

– Moves eye laterally

Cranial Nerve VI - AbducensAssessment

Make a big x in the air and draw a

line through it.

**Observe for twitching or

nystagmus

Damages

*Cannot move eyeball laterally

*Nystagmus – “Dancing Eyes”

Cranial Nerves• The Facial Nerves (VII)

– Mixed – Sensory – Motor

– Origin: • Sensory

– Taste receptors on anterior 2/3 of tongue

– Destination:

• Sensory

– Sensory nuclei of pons

Cranial Nerves• The Facial Nerves (VII)

– Sensory Innervation

– Geniculate Ganglion

• Contains cell bodies

of sensory neurons

Cranial Nerves• The Facial Nerves (VII)

–Origin: • Motor

–Motor nuclei of pons

–Destination

• Somatic Motor

–Muscles of

facial

expression

Cranial Nerves– Somatic Motor

– Facial nerve branches

• Temporal

• Zygomatic

• Buccal

• Mandibular

• Cervical branches

Cranial Nerves• The Facial Nerves (VII)

– Destination

– Visceral motor

– Parasympathetic Function

» Pterygopalatine Ganglion

Lacrimal gland

Mucous Glands

» Submandibular Ganglion

Submandibular Glands

Sublingual Glands

SUBLINGUAL

SUBMANDIBULAR

Cranial Nerves• The Facial Nerves (VII)

– Pathway: • Internal acoustic

meatus to facial canals

• Then through the stylomastoid foramina

Cranial Nerve VII - Facial NerveAssessment

-- To test for taste

**Place sugar(sweet) salt, vinegar(sour) & quinine(bitter)

on anterior 2/3 of tounge

-- To test for tearing

**Place ammonia near the eyes

-- To test for facial symmetry

**Have patient close eyes, smile, whistle and blow

Cranial Nerve VII - Facial NerveDamages

*Shingles

* Lyme disease

* Loss of taste

* Decreased saliva

* Bell’s Palsy.

Cranial Nerves• The Vestibulocochlear Nerves (VIII)

– Primary function:

• Special sensory

– Vestibular branch

» Balance and equilibrium

» Originates at receptors of vestibule (balance)

» Connects to vestibular nuclei of pons and medulla

oblongata

Cranial Nerves• The Vestibulocochlear Nerves (VIII)

– Primary function:

• Special sensory

– Cochlear branch

» Hearing

» Originates at sensors of cochlea (hearing)

» Connects with cochlear nuclei of pons and medulla

oblongata

Cranial Nerves• The Vestibulocochlear Nerves (VIII)

– Origin: • Receptors of inner ear

– Pathway: • Internal acoustic meatus of temporal bones

Cranial Nerve VIII - VestibulocochlearAssessment

**Tuning Fork

Damages

Vertigo

Rotating

Ataxia

Lack of coordination

Tinnitus

Ringing of ears

Cranial Nerves• The Glossopharyngeal Nerves (IX)

– Primary function:

• Mixed to head and neck

• Origins:

– Motor

*From motor nuclei of medulla oblongata

– Sensory

» Posterior 1/3 of tongue

» Part of pharynx and palate

» Carotid arteries

Cranial Nerves

– Superior and inferior ganglion

• Sensory neurons of tongue and pharynx

FIGURE 14-25

Cranial Nerves• The Glossopharyngeal Nerves (IX)

– Pathway: • Jugular foramina

– Between occipital and temporal bones

Cranial Nerves• The Glossopharyngeal Nerves (IX)

– Destination: • Sensory

– Sensory nuclei of medulla oblongata

• Somatic motor – Nerves involved in swallowing

Cranial Nerves• The Glossopharyngeal Nerves (IX)

– Destination:• Visceral motor • Parasympathetic Function

– Otic Ganglion» Parotid salivary

gland

Cranial Nerve - IX Glossophary-ngeal• Assessment

– Test for taste on posterior 2/3– Test position of uvula– Test swallowing and gag reflex

• Damages– Difficulty in

• Swallowing• Digestion• Loss of taste• Loss of sensation in throat• Reduced saliva production

Cranial Nerves• The Vagus Nerves (X)

– “The Vagabond”

• The only cranial

nerve that extends

beyond the head and

neck

– Primary function:

• Mixed

• 90% of

parasympathetic

function

• Thorax and abdomen

Cranial Nerves• 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

Cranial Nerves• The Vagus Nerves (X)

– Pathway:

• Jugular foramina

• Between occipital and temporal

bones

Cranial Nerves

– Sensory Neurons

located in

• Superior Ganglion

– Jugular ganglion

• Inferior Ganglion

– Nodose ganglion

Cranial Nerves• The Vagus Nerves (X)

– Destination:• Sensory

– Sensory nuclei and autonomic centers of medulla oblongata

• Visceral motor – Parasympathetic– Muscles of the palate and

pharynx– Muscles of the digestive,

respiratory, and cardiovascular systems in thoracic and abdominal cavities

Cranial Nerve X - Vagus• Assessment• **Same as IX• Damages

– Loss of sensations to organs– Interfere with swallowing, digestion

and vocal cords– Increase blood pressure

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

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

Cranial Nerves• The Accessory Nerves (XI)

– Pathway: • Jugular foramina between occipital and

temporal bones

Cranial Nerves• The Accessory Nerves (XI)

– Destination: • Internal branch

– Voluntary muscles of palate, pharynx, and larynx

Figure 14-27

Cranial Nerves• The Accessory Nerves (XI)

– Destination: • External branch

– Sternocleidomastoid and trapezius muscles

Cranial Nerve XI - Accessory• Assessment

– Have patient rotate head– Have patient cough

• Damages– Ipsilateral paralysis of

sternocleidimastoid and trapezius• So you can’t raise your

shoulders or turn your head– Difficulty in swallowing

Cranial Nerves• The Hypoglossal Nerves (XII)

– Primary function: • Motor (tongue movements)

– Origin: • Motor nuclei of medulla oblongata

Cranial Nerves• The Hypoglossal Nerves (XII)

– Pathway: • Hypoglossal canals of occipital bone

– Destination: • Muscles of tongue

Cranial Nerve XII - Hypoglossal• Assessment• **Have patient protrude and retract • tongue• Damages

– Atrophy of ipsilateral tongue– Difficulty

• Swallowing• Chewing • Speaking

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

• BRAINSTEM– MIDBRAIN

– III - Oculomoter - movement of eye– IV - Trochlear – movement of eye

– PONS– V - Trigeminal – chewing, touch, pain & temperature receptors– VI - Abducens – movement of eyeball– VII - Facial – facial expressions, tears, saliva & taste– VIII - Vestibulocochlear (vestibular branch only). - equilibrium

– Medulla Oblongata– VIII – Vestibulocohlear – hearing & equilibrium– IX - Glossopharyngeal – swallowing, taste, saliva production, blood

pressure and monitor breathing

– X - Vagus – swallowing, coughing, voice, blood pressure, monitor breathing, control digestive

secretions & organs of heart, stomachand G, I tract– XI - Accessory – swallowing, movement of head and shoulders– XII - Hypoglossal – swallowing, chewing & speaking

CEREBRUM - I - Olfactory –smell

l - II - Optic - vision