cranial nerves Flashcards
how many peripheral nerves that originate from the brain and brainstem,
numbered along longitudinal axis
12
cranial nerves
Travel out of skull through foramina
* Have nuclei in cerebrum & brainstem
* CN I and II – forebrain
* CN III – XII from the brainstem
Mostly provide innervation of the head and neck
* Somatic and visceral innervation
* Include parasympathetic but NOT sympathetic innervation
* Special sensory innervation
* Vision, smell, taste, hearing, equilibrium
cranial nerves
primary function of CN I Olfactory Nerve
special sensory smell
Special Afferent fibers (SA)
* Attached to cerebrum
* Olfactory tracts travel to cerebral
cortex, hypothalamus & limbic
system
CN I Olfactory nerve
Olfactory bulbs innervated by other brain
nuclei cause
central adaptation
rapid neuron replacement (unusual)
CN I Olfactory nerve
- Damage to the olfactory nerve (I) can cause an
inability to smell anosmia, a distortion in the
sense of smell
parosmia, or a distortion or lack
of taste
primary function of CN II Optic nerve
special sensory (vision)
- CN I is usually evaluated only after head trauma, when lesions of the
anterior fossa (eg, meningioma) are suspected or patients report
abnormal
smell or taste
Special Afferent fibers (SA)
* Optic nerves connect the retina
to the optic chiasm
Only fibers from the medial side
of the retina (sees peripheral
vision) decussate at the optic
chiasm to the other side of the
brain
injury to CN II optic nerve may impact
visual acuity & visual fields
* Injury may impair ability to see objects on left
or right side
Optic chiasm lesions cause _______
type of partial blindness where
vision is missing in the outer half of both the
right and left visual field
Inflammation (optic neuritis) may impact the
sharpness of vision or color detection
Color vision tested using
Ishihara plates
CN III Oculomotor Nerve primary function
motor (eye movements)
General somatic efferent (GSA)
* Innervates 4 out of 6 extrinsic ______
eye muscles
& levator palpebrae superioris (upper
eyelid)
Autonomic nerves travel to _______
and control intrinsic eye muscles - pupil
diameter & lens shape to focus light on
ciliary ganglion
Intrinsic Eye Muscles
* Ciliary muscle(lens)
* Sphincter pupillae
- Dilator pupillae
parasympathetic
parasympathetic
sympathetic
CN IV Trochlear Nerve
* Innervates superior oblique
extrinsic muscle of the eye
General somatic efferent (GSA)
Testing of CN III Oculomotor Nerve
damage can cause
double vision and
inability to coordinate the movements of
both eyes (strabismus), eyelid drooping
(ptosis) and pupil dilation (mydriasis).
* May tilt head to accommodate
CN VI Abducens Nerve
innervates ____
lateral rectus
extrinsic muscle of the eye
* Abducts the eye
The ability of the eye to look
down and inwards is
controlled by the
trochlear nerve (IV)
CN VI Abducens Nerve
function?
motor (eye movements)
general somatic efferent (GSA)
Oculomotor (III), Trochlea
(IV) & Abducens (VI)
nerves all pass through
superior orbital fissure of skull
Testing CN III, IV & VI
the oculomotor, trochlear and abducens are all involved in eye movements
CN V Trigeminal Nerve
primary function
Mixed (sensory and
motor to face)
* General somatic
afferent (GSA) &
Special visceral
afferent (SVA
testing CN III,IV and VI
Test eye movement - follow your finger with their eyes
3 branches of CN V Trigeminal nerve
3 branches:
1. Ophthalmic
2. Maxillary
3. Mandibular
CN V Trigeminal Nerve
V1: Ophthalmic branch: Sensory
V2: Maxillary branch: Sensory
V3: Mandibular branch: Mixed
V1: Ophthalmic branch: Sensory
V1: Ophthalmic branch: Sensory
Orbital structures, cornea, skin of forehead, nasal cavity,
upper eyelid, eyebrow & part of nose
V2: Maxillary branch: Sensory
Lower eyelid, gums, upper lip, cheek, teeth, nose, palate
& pharynx
V3: Mandibular branch: Mixed
Sensory – teeth, lips, lower gums
Motor – muscles of mastication (chewing)
Injury & Testing of CN V Trigeminal Nerve
Testing
* Corneal reflex
* Facial sensitivity
* Jaw motor strength
pain in areas innervated by
maxillary and mandibular branches
Trigeminal Neuralgia (tic doulouroux) =
primary function of CN VII facial nerve
Mixed (sensory and motor to face)
* General somatic afferent (GSA) Special afferent (SA), General visceral efferent
(GVE) & Special visceral efferent (SVE
CN VII Facial Nerve
5 branches
CN VII Facial nerve
Sensory –
* Proprioception of facial muscles
* Pressure on face
* Special Sensory – Taste anterior 2/3 of tongue
Motor –
* Somatic – facial expression
* Visceral – tear ducts, salivary glands, nasal mucous glands – Autonomic – parasympathetic
Intracranial and extracranial branches
Travels through parotid gland
CN VII facial nerve
innervate lacrimal glands (tears), nasal
cavity & pharynx
Pterygopalantine ganglia
CN VII Facial Nerve – Autonomic Ganglia
* Facial nerves carry pre-ganglionic autonomic fibers to autonomic
ganglia
parasympathetic
innervate submandibular & sublingual
salivary glands
Submandibular ganglia
Primary Function: Special sensory
* Special afferent (SA)
* Vestibular branch: Balance & Equilibrium
* Cochlear branch: Hearing
Testing
* Balance & hearing
CN VIII Vestibulocohlear nerve
Inflammation of a Facial Nerve from viral infection
* Temporary paralysis on one side of face, loss of taste
Testing
* Facial expression
CN VII Facial Nerve – Bell’s Palsy
Primary Function: Mixed (sensory & motor)
* General Somatic afferent (GSA), General visceral afferent (GVA), Special
afferent (SA) & General somatic efferent (GSE) General visceral efferent
(GVE
CN IX Glossopharyngeal Nerve
Sensory – general sensory palate
* special sensory taste in posterior 1/3 of tongue
* Visceral sensory: Monitors blood pressure and dissolved gas concentration by
receptors in carotid artery
CN IX Glossopharyngeal Nerve
Motor
* Somatic – muscles of swallowing
* Visceral – parotid salivary glands – autonomic via Otic ganglia
CN IX Glossopharyngeal Nerve
Testing
Gag reflex – touch arches of pharynx
CN IX Glossopharyngeal Nerve
CN X Vagus Nerve
Primary Function: Mixed (sensory & motor)
* General Somatic afferent (GSA), General
visceral afferent (GVA), Special afferent (SA) &
General somatic efferent (GSE) General
visceral efferent (GVE)
Motor: Pharynx, larynx, vocal cords
* preganglionic parasympathetic innervation to
heart smooth muscles, small intestines &
gland
CN X Vagus Nerve
Sensory: Somatic sensory information from
diaphragm
* Visceral sensory information from abdominal
tract & respiratory tract
CN X Vagus nerve
testing problems swallowing
CN XI Accessory Nerve
AKA – Spinoaccessory
nerves
* Somatic Motor only
* Internal branch –
swallowing &
muscles of vocal
cords
* External branch –
muscles of neck &
back
* Not really a cranial
nerve because originates from spinal cord
CN XI Accessory Nerve
primary function
Motor
muscles of neck & back
* General somatic efferent
(GSE)
* Supplies the
sternocleidomastoid and
trapezius muscles. Damage
to the nerve may cause
a winged scapula
CN XII Hypoglossal Nerve
primary function
Motor – tongue
muscles
* General somatic efferent (GSE)
* Intrinsic originate outside & insert on
tongue
* Extrinsic muscles within tongue
- A damaged hypoglossal nerve will result
in an inability to stick the tongue out
straight; here seen in an injury resulting
from
surgery
know autonomic ganglia parasympathetic
slide 36
Sympathetics to Head * Do NOT originate from cranial nerves
* Originate from upper thoracic segments
* Ascend sympathetic chain to
cervical
ganglia (upper, middle & lower cervical
ganglia) and synapse
Post-ganglionics distribute via
gray rami
communicans to skin or along arterial
branches/cranial nerves to internal
structures
what is horners syndrome
damage to
sympathetic nerves in cervical region
look at slide 38 cranial nerves
Cranial nerves are classified by primary functions
* May also have important secondary functions
* 6 cranial nerves associated with eye function
Mnemonic for Cranial Nerves
Oh, Once One Takes The Anatomy Final, Very Good Vacations Are
Heavenl
