S1B5 - Cranial Nerves IX-XII Flashcards
Which cranial nerve provides parasympathetic output to the parotid gland via the otic ganglion?
CN IX provides parasympathetic output to the parotid gland via the otic ganglion.
What happens to the uvula as a result of a unilateral lesion of CN X?
Lesions of CN X result in paralysis of the pharynx and larynx, and a deviation of the uvula to the opposite side of injured nerve. There is also a loss of the efferent limb of the gag reflex.
What is the motor function of the hypoglossal nerve?
CN XII is the hypoglossal nerve. It innervates the intrinsic and extrinsic tongue muscles (except for palatoglossus, which is innervated by CN X).
What occurs after a lesion of CN IX?
Lesions of CN IX cause a loss of the afferent limb of the gag reflex and loss of taste and general sensation from posterior third of the tongue.
A patient presents with inability to turn her head to the left and inability to shrug her shoulder on the right side. What nerve is injured?
Unilateral lesions of CN XI result in a decreased ability to turn the head to the opposite side of injured nerve and a decreased ability to shrug the ipsilateral shoulder.
What cranial nerve makes up the efferent limb of the gag reflex?
CN X functions as the efferent limb of the gag reflex (CN IX is afferent).
Through what foramen does CN XII exit the skull?
CN XII exits the skull through the hypoglossal canal.
What occurs after a unilateral lesion of CN XII?
Lesions of CN XII result in a deviation of the tongue to the SAME side of the injured nerve, “you lick the lesion.” Ipsilateral deviation is due to paralysis of the ipsilateral genioglossus muscle and unopposed action of the contralateral genioglossus muscle.
Which of the following is an inaccurate statement?
A) CN VII innervates stapedius muscles in ear
B) CN XII injury will cause deviation of tongue to opposite side of injury
C) CN VI innervates lateral rectus muscle
D) CN XI innervates sternocleidomastoid muscles
CN XII injury will cause deviation of tongue to opposite side of injury
Answer Explanation
CN XII injury will result in deviation of tongue to the same side of injury. By contrast, CN X injury will result in deviation of uvula to the opposite side of injury. All of the other statements above are accurate correlations of individual cranial nerve functions.
What foramen carries CN X as it exits the skull?
CN X exits the skull through the jugular foramen.
What are the sensory functions of the vagus nerve and what seven muscles are innervated by the vagus nerve?
CN X is the vagus nerve. It has afferent sensory fibers from the ear canal (outer ear) and the meninges. In addition it provides motor innervation to the following muscles:
- Cricothyroid
- Palatoglossus
- Levator veli palatini
- Laryngeal muscles
- Palatopharyngeus
- Salpingopharyngeus
- Pharyngeal constrictor muscles
What does CN IX traverse through to exit the skull and what are the functions of CN IX?
CN IX is the glossopharyngeal nerve, which exits the skull at the jugular foramen. It has the following functions:
- General sensation of the posterior one third of the tongue and mucosa of the oropharynx
- Taste from the posterior one third of the tongue
- Receives visceral input from the carotid body and carotid sinus
What muscles are innervated by CN XI?
CN XI is the spinal accessory nerve, it innervates the sternocleidomastoid and trapezius muscles.
What foramen carries CN XI as it exits the skull?
CN XI exits the skull via the jugular foramen.
During cardiac surgery, a patient suffers iatrogenic injury to the nerve which carries afferent signals from the aortic arch chemo-baroreceptors. A postoperative examination of this patient will likely show which new finding?
A) Difficulty in balance
B) Loss of afferent limb of gag reflex
C) Deviation of uvula
D) Deviation of tongue
E) Inability to shrug shoulders
Deviation of uvula
Answer Explanation
Branches of the vagus nerve (CN X) monitor inputs from aortic arch chemo-baroreceptors. This nerve also mediates speech and swallowing: lesions result in paralysis of the pharynx and larynx and deviation of the uvula to the side opposite the injured nerve. CN VIII mediates hearing and balance. CN IX mediates the afferent limb of the gag reflex and monitors the carotid sinus baroreceptors and carotid body chemoreceptors. CN XI injury results in inability to turn head to the contralateral side (sternocleidomastoid) and inability to shrug the ipsilateral shoulder (trapezius muscle). CN XII results in deviation of the tongue to the same side of injury.
What can be seen in a bilateral lesion to CN XI?
Bilateral lesions of CN XI result in a decreased ability to look straight down by tilting chin toward chest and a decreased ability to shrug both shoulders.
What nerve provides parasympathetic input to the organs from the neck to the transverse colon?
CN X also innervates the viscera of the neck, abdomen, and thorax and provides parasympathetic input to all organ from the neck to the transverse colon (except the adrenal glands).
What muscle is innervated by CN IX?
CN IX provides motor innervation for the stylopharyngeus muscle.
