Functional Components Of Cranial Nerves Flashcards
What are the functional components of cranial nerves?
Motor (efferent): GSE, GVE, SVE
Sensory (afferent): GSA, GVA, SVA, SSA
*NoSSE
What is the function of CN I (Olfactory nerve)?
CN I is responsible for the special sensory function of smell (SVA). It enters the cranial cavity through the cribriform plate and synapses in the olfactory bulb.
What is the function of CN II (Optic nerve)?
CN II is responsible for the special sense of vision (SSA). It carries visual information from the retina to the lateral geniculate body and then to the primary visual cortex.
What are the functions of CN III (Oculomotor nerve)?
GSE: Innervates extraocular muscles (superior, medial, and inferior recti, inferior oblique, and levator palpebrae superioris).
GVE: Parasympathetic innervation to the sphincter pupillae and ciliary muscles.
What is the function of CN IV (Trochlear nerve)?
CN IV innervates the superior oblique muscle, which moves the eye down and out (GSE).
What is the function of CN VI (Abducens nerve)?
CN VI innervates the lateral rectus muscle, which is responsible for lateral movement of the eye (GSE).
What are the functions of CN V (Trigeminal nerve)?
GSA: General sensation from the face.
SVE (Branchial motor): Innervates muscles of mastication.
GSE: Proprioceptive fibers.
What are the functions of CN VII (Facial nerve)?
SVE: Muscles of facial expression.
GVE: Parasympathetic innervation to lacrimal, submandibular, and sublingual glands.
SVA: Taste from the anterior 2/3 of the tongue.
GSA: Sensation to part of the external ear.
What is the function of CN VIII (Vestibulocochlear nerve)?
CN VIII is responsible for hearing and balance (SSA). It carries sensory information from the cochlea (hearing) and semicircular canals (balance).
What are the functions of CN IX (Glossopharyngeal nerve)?
SVE (BM): Innervates the stylopharyngeus muscle.
GVE: Parasympathetic innervation to the parotid gland.
GVA: Sensation from the posterior 1/3 of the tongue, oropharynx, and carotid body.
SVA: Taste from the posterior 1/3 of the tongue.
What are the functions of CN X (Vagus nerve)?
SVE (BM): Innervates muscles of the palate, pharynx, and larynx.
GVE: Parasympathetic innervation to thoracic and abdominal organs.
GSA: Sensation from the auricle and external acoustic meatus.
GVA: Sensation from thoracic and abdominal organs.
SVA: Taste from the epiglottis.
What is the function of CN XI (Spinal accessory nerve)?
CN XI innervates the sternocleidomastoid and trapezius muscles (GSE).
What is the function of CN XII (Hypoglossal nerve)?
CN XII innervates the muscles of the tongue (GSE).
Where are the nuclei of cranial nerves located?
All cranial nerve nuclei, except CN I and CN II (which are extensions of the forebrain), are located in the brainstem (midbrain, pons, and medulla oblongata).
What is the corneal reflex, and which cranial nerves are involved?
The corneal reflex tests the sensory function of CN V (Trigeminal nerve) and the motor function of CN VII (Facial nerve). It checks if a patient winks when the cornea is touched.
What is the difference between upper motor neuron (UMN) and lower motor neuron (LMN) lesions in CN VII (Facial nerve)?
UMN lesion: Affects the contralateral lower face (forehead spared).
LMN lesion: Affects the entire ipsilateral face (forehead and lower face).
What is the role of the Edinger-Westphal nucleus
The Edinger-Westphal nucleus is responsible for the parasympathetic (GVE) component of CN III, controlling the sphincter pupillae and ciliary muscles for pupil constriction and lens accommodation.
Which cranial nerves are involved in taste sensation?
CN VII (Facial nerve): Taste from the anterior 2/3 of the tongue.
CN IX (Glossopharyngeal nerve): Taste from the posterior 1/3 of the tongue.
CN X (Vagus nerve): Taste from the epiglottis.
How are cranial nerve nuclei organized in the brainstem?
They are organized into six discontinuous columns: three sensory (GSA, GVA/SVA, SSA) and three motor (GSE, GVE, SVE).
Which cranial nerves exit through the superior orbital fissure?
CN III (Oculomotor), CN IV (Trochlear), CN V1 (Ophthalmic branch of Trigeminal), and CN VI (Abducens).
Which cranial nerves exit through the jugular foramen?
CN IX (Glossopharyngeal), CN X (Vagus), and CN XI (Accessory).
What is the clinical significance of a CN III (Oculomotor) palsy?
It causes ptosis (drooping eyelid), dilated pupil, and inability to move the eye medially, upward, or downward.
Which cranial nerves are involved in the gag reflex?
CN IX (Glossopharyngeal) for sensory and CN X (Vagus) for motor.
Which cranial nerves are involved in the pupillary light reflex?
CN II (Optic) for sensory and CN III (Oculomotor) for motor.
