Cranial nerves IX-XII
In this lesson, we’ll cover cranial nerves IX-XII.
1) Watch the following videos about cranial nerves IX-XII:
2) Next, watch this video about the gut-brain axis, a connection between our gut and brain that relies heavily on the vagus nerve:
3) Finally, answer these questions to test your understanding:
1. Damage to the glossopharyngeal nerve (cranial nerve IX) would most likely be associated with which of the following?
- A. loss of taste on the anterior 2/3 of the tongue
- B. difficulty moving the tongue side to side
- C. loss of taste on the posterior 1/3 of the tongue
- D. facial paralysis on one side of the face
Show Answer
Correct answer: C
Damage to the glossopharyngeal nerve can cause a variety of symptoms, including a loss of taste on the posterior ⅓ of the tongue, trouble swallowing, and generally decreased sensation on the back of the tongue, the soft palate, and pharynx.
2. After head trauma, a patient has damage to his right hypoglossal nerve. When he sticks out his tongue, which side is it likely to deviate toward?
- A. right
- B. left
- C. neither; it won't deviate at all
Show Answer
Correct answer: A
If the hypoglossal nerve on only one side is damaged and the patient is asked to protrude his or her tongue, the tongue will typically deviate toward the side of the damaged nerve.
3. Which of the following cranial nerves carries the majority of all the parasympathetic fibers in the body?
- A. Trigeminal nerve (CN V)
- B. Glossopharyngeal nerve (CN IX)
- C. Vagus nerve (CN X)
- D. Accessory nerve (CN XI)
Show Answer
Correct answer: C
The vagus nerve (cranial nerve X) carries over 75% of all parasympathetic fibers in the body. It innervates organs in the thorax and abdomen, including the heart, lungs, and digestive tract, making it the main parasympathetic nerve of the body.
4. A patient presents with left shoulder weakness and difficulty lifting their left arm. Their left shoulder also is drooping compared to the right, and their left shoulder blade is protruding abnormally far from the back. The doctor determines the patient is experiencing a cranial nerve dysfunction. Which of the following cranial nerves is most likely involved?
- A. Accessory nerve (CN XI)
- B. Trochlear nerve (CN IV)
- C. Vagus nerve (CN X)
- D. Abducens nerve (CN VI)
Show Answer
Correct answer: A
The accessory nerve supplies the sternomastoid and trapezius muscle. The sternomastoid helps to turn your head to the side, as well as bend your neck down or to the side. The trapezius is involved with the movement of the neck and scapula (shoulder blade). Dysfunction of the accessory nerve often causes shoulder pain, impaired arm and shoulder movement, a drooping shoulder, and/or protrusion of the shoulder blade (winged scapula).
5. Which cranial nerve connects the brain to the gastrointestinal tract and plays a central role in communication along the gut–brain axis?
- A. olfactory nerve (CN I)
- B. trigeminal nerve (CN V)
- C. vagus nerve (CN X)
- D. hypoglossal nerve (CN XII)
Show Answer
Correct answer: C
The vagus nerve (CN X) sends and receives signals between the brain and much of the GI tract. Because it carries both sensory information from the gut to the brain and motor signals back to the gut, it is the main nerve involved in communication along the gut–brain axis.
