Cranial Nerves Flashcards
\_\_ pairs of spinal nerves. \_\_ Cervical \_\_ thoracic \_\_ lumbar \_\_ sacral \_\_ coccygeal
31 pairs 8 cervical 12 thoracic 5 lumbar 5 sacral 1 coccygeal
Which cranial nerves have CNS characteristics?
Which have PNS characteristics?
CNS- CN I and CN II (has meninges coverings) Strictly sensory. Soma of those neurons are in the CNS.
PNS- CN III to CN XII
Where do CN I and Cn II originate
In the prosencephalon (forebrain, contains diencephalon and telencephalon)
Where do CN 3-12 originate?
Originate in the mesencephalon (midbrain) and the rhombencephalon (hindbrain, contains metencephalon- pons and cerebellum)
Mnemonics for name and function
Name- On occasion our trusty truck acts funny. Very good vehicle any how.
Function- Some say money matters, but my brother says big brains matter more.
Mesencephalon
Midbrain
Rhombencephlon
Hindbrain. Contains metencephalon (pons and cerebellum) and the myelencephalon (medulla)
Metencephalon
Pons and cerebellum. Within the rhombencephalon (hindbrain)
Myelencephalon contains
Medulla. Within the rhombencephalon (hindbrain)
Typically, nerves that emerge from the medial brainstem are __
Typically, nerves that emerge from the lateral brainstem are __
Typically, nerves that emerge between them are ___
medial- Motor, efferent, outbound (exiting CNS)
lateral-Sensory, afferent, inbound (arriving at CNS)
middle- Mixed
2 categories of somatic afferent components
- General (GSA)
-Typical touch/pain sensations (true somatic afferent)
-Fibers convey impulses from the skin and skeletal muscle spindles.
-CN V1, V2, V3, VII, IX, X
2 .Special (SA)
-Involved with CN II and VIII (hearing and balance)
General somatic efferent (GSE)
Somatomotor function (true somatic efferent)
-Skeletal muscles whose origins are not derived from the branchial/pharyngeal arches. This includes extra ocular muscles, tongue muscle.
CNIII, IV, VI, and XII
2 Categories of visceral efferent
- General (GVE)- Innervate smooth muscles, cardiac muscles. Spinal nerves can carry GVE fibers. CN 7, 9, and 10
- Special (SVE)- Goofy one. Not autonomic. Innervate skeletal muscles deep in the neck and face. (deep muscles are usually smooth). Branch of CN V, 7, 9, 10th and part of the 11th (called the cranial root)
2 Categories of the visceral afferent
- General (GVA)- Fibers convey impulses from the sensory receptors in the viscera and blood vessel walls (true autonomic efferent)
CN 9 and 10. - Special (SVA)- Olfactory and gustatory (taste) senses. Cn 1, 7, 9, and 10.
What cranial nerves are located in the telencephalon (within the proencephalon)
CN I (olfactory)
What cranial nerves are located in the Diencephalon (within the proencephalon)
CN II (optic)
Proencephalon
Contains the diencephalon and the telencephalon
What cranial nerves are located in the mesencephalon
CN III (oculomotor) and CN IV (trochlear)
What cranial nerves are located in the metencephalon (pons)?
***Division of the rhombencephalon (hindbrain)
CN V (trigeminal) CN VI (Abducens) CN VII (facial)
What cranial nerves are located in the myelencephalon (medulla) ?
***Division of the rhombencephalon (hindbrain)
CN VIII (Vestibulocochlear) CN IX (Glossopharyngeal) CN X (Vagus) CN XI (Accessory spinal) CN XII (Hypoglossal)
CN I
olfactory
sensory
Olfactory cranial nerve
CN I
sensory
CN II
Optic nerve
Sensory
CN III
Oculomotor nerve
motor
Oculomotor nerve
CN III
motor
CN IV
Trochlear nerve
motor
Trochlear nerve is CN #
IV
motor
CN V
Trigeminal
both
CN VI
Abducens
motor
Abducens nerve is CN #
VI
motor
CN VII
Facial
both
The facial nerve is CN #?
VII
both
CN VIII
vestibulocochlear
sensory
The vestibulocochlear nerve is CN #
CN VIII (8) sensory
CN IX
Glossopharyngeal
both
The glossopharyngeal nerve is CN #?
IX
both
CN X
Vagus
both
Vagus nerve is CN #?
X
both
CN XI
Accessory/spinal accessory
motor
The accessory nerve is CN #?
XI
motor
CN XII
Hypoglossal
motor
The hypoglossal nerve is CN #
XII
motor
Branchial pharyngeal arches
6 total, only 4 are externally visible on a developing fetus.
Arch 1- Mandibular. Innervates temporalis, masseter, and anteiror belly of digastric. Important muscles in chewing.
Arch 2- Hyaloid
Arch 3-6: No special name
The 5th arch doesn’t really develop into anything.
6th arch fibers merge with 4th arch fibers.
Brachial arch one (called the mandibular arch). CN derived and skeletal muscles it innervates?
CN: Madibiluar nerve, which is a branch of trigeminal nerve
Skeletal muscles: Muscles involved with chewing. Temporalis, master, and digastric.
Brachial arch two (called the hyaloid arch) CN derived and skeletal muscles it innervates?
CN: Facial, CN VII
Skeletal: Innervates muscles of facial expression.
Brachial arch 3. CN derived and skeletal muscles it innervates?
CN: Glossopharyngeal (CN IX)
Skeletal: muscles of the pharynx. Swallowing. Neck muscles.
Brachial arch 4. CN derived and skeletal muscles it innervates?
CN: Vagus, CN X. Tends to merge with arch 6.
Skeletal: cricothyroid
Brachial arch 6. CN derived and skeletal muscles it innervates?
CN: Vagus (CN X) and possibly spinal accessory (CN XI). Tends to merge with arch 4.
Skeletal: Intrinsic laryngeal muscles
Sensory ganglia in the head and which CN do they associate with
CN V- Trigeminal and geniculate
CN VIII- spiral and vestibular
CN IX- superior ganglion, and inferior petrosal
CN X- Superior (jugular) and inferior (nodose) ganglia.
Analagous to dorsal root ganglia adjacent to the spinal cord
Pseudounipolar neurons.
Sensory ganglia in the head are associated with which cranial nerves
5, 7, 8, 9, and 10
Autonomic ganglia in the head is exclusively ___
Parasympathetic
Parasympathetic autonomic ganglia in the head and which CN do they associate with
CN III- Ciliary ganglion involved in pupillary constriction (miosis) and stimulates ciliary muscle to increase accommodation.
CN VII- Pterygopalatine ganglion found in the pterygopalatine fossa by ear. Stimulates lacrimal gland to increase tear production
Also the submandibular ganglion that stimulates the submandibular and sublingual gland
CN IX- Otic ganglion innervates parotid gland.
TEST- What components are found in an autonomic ganglia?
CONTAINS CELL BODIES OF POSTSYNAPTIC (POSTGANGLIONIC) NEURONS
Location and role of CN I- Olfactory Nerve (Sensory)
- Considered to be a CNS nerve
- Located through cribriform plate of the ethmoid bone. Nerves pass through the olfactory foramina (roots extending from the olfactory bulb)
- SVA fibers only
- If damaged, these fibers can sometimes grow back and person can regain sense of smell.
Location and role of CN II- Optic nerve (sensory)
Retinal ganglion cells (RGC’s) originate in the retina and terminate in the lateral geniculate body (LGN) and some non-visual centers of the brain suchh as the pineal gland, pulvinar, superior colliculus.
- Within common tendinous ring
- Exits thru Optic canal
- Present in the Middle cranial fossa as optic chiasm (which is superior to the cavernous sinus)
-SSA nerve fibers
SVA. Think-
Smell and taste
Naegleria
Ameoba in warm waters that enter through nasal cavity and infect CN I (olfactory) and then can enter the brain. Progressive. Death.
Location and role of CN III- Oculomotor (Motor)
-As it enters the orbit through the common tendinous ring, it divides in the to superior division and the inferior division (3 branches)
Superior division- Innervates SR Inferior division- Medial branch: MR Central branch: IR Lateral branch: IO and ciliary ganglion which is parasympathetic innervation
-Travels through middle cranial fossa (within cavernous sinus) through the superior orbital fissure/annulus of Zinn.
GSE fibers- EOMs and levator
GVE fibers- Parasympathetic innervation to iris and ciliary muscles. Allows for miosis and accommodation.
SSA think
Vision, hearing, balance
Location and role of CN IV- Trochlear (Motor)
- Enter the orbit through superior orbital fissure and passes ABOVE common tendinous ring
- Exits middle cranial fossa within cavernous sinus DORSALLY (all other cranial nerves exit ventrally)
- Long course makes it more susceptible to injury. Ex: trochlear nerve palsy (head tilt)
- Innervates SO
- GSE nerve fibers
Typically, cranial nerves exit
Ventrally. Except CN IV (trochlear), it exits dorsally. This causes IV to be super long, and easily damaged.
Location and role of CN V- Trigeminal (mostly sensory, but also has motor. So both)
- Trigeminal (Semilunar or gasserian) ganglion in the hindbrain/pons. Houses soma of afferent (sensory) neurons.
- GSA fibers are THE sensory nerves of the head.
- SVE fibers ride along with sensory fibers in the mandibular division to innervate muscles of mastication.
V1- ophthalmic is sensory (GSA)
V2- maxillary is sensory (GSA)
V3- Mandibular is sensory AND motor (GSA and SVE)
Which CNs enter through superior orbital fissure
3, 4, and 6
CN 5b (maxillary) enters cavernous sinus how
Rotundum
Which divisions of the trigeminal innervate
- Facial skin
- Nasal and pharyngeal mucosa
- Anterior 2/3 of tongue
- Muscles of mastication
- GSA fibers- ophthalmic, maxillary and mandibular
- GSA fibers- Ophthalmic and maxillary
- GSA fibers- mandibular
- SVE fibers (think brachial arches)- Mandibular
3 divisions of CNV ophthalmic (GSA)
- **Nasocilliary
- Anterior and posterior ethmoid, infratrochlear, sensory root of ciliary ganglion, and long ciliary
- **Frontal
- Supraorbital and supratrochlear
***Lacrimal
Dermatomes - what are they are where aren’t they located
Sensory/afferent innervation. Not present on face bc Cranial nerves innervate face sensory
Ciliary ganglion
Sensory root (GSA) CNV- ophthalmic- nasocilliary - ciliary ganglion
Maxillary division of CN V
GSA nerve fibers.
- Sensory input is via zygomatic and infraorbial nerves at the inferior orbital fissure.
- Within the pterygopalatine fossa, it travels posterior. Hits bone and then drills a hole (rotundum) and enters cavernous sinus. Sends branches to the pterygopalatine ganglion.
Mandibular division of CN V
-enters/exit middle cranial fossa via foramen ovale. Does not travel through cavernous sinus
Branches:
- Masseteric (M)
- Medial pterygoid (M)
- lateral pterygoid (M)
- Auriculotemporal (S)
- Lingual (S)
- Inferior alveolar (B) innervates lower teeth. Long brach that terminates at mental nerve of mandible.
Which divisions of CN V travel thru cavernous sinus
ophthalmic and maxillary
Motor muscles of mastication
Lateral and medial pterygoids, masseter and temporals.
Clinical assessment of CN V (sensory)
CN V1- forehead region
CN V2- cheek region
CN V3- chin
Herpres Zoster Ophthalmic (HZO) can be also called
Ocular shingles. Portion of face with symptoms lets Dr know which portion of CN 5 is housing the virus.
Hutchinsons sign- If tip of nose is blistered, it is an indication that the eye is also involved since CN V1 innervates eyes and nasal portion.