Medulla, CN VII and CN XII*

Question 1

What does the medulla oblongata contain?

Answer 1

• the nuclei for the last 6 cranial nerves.
• the respiratory and cardiovascular centers.
• ascending and descending pathways between the spinal cord and brain.

Question 2

How are cranial nerves numbered? and explain the numbers and origins.

Answer 2

The cranial nerves are numbered according to their level of origin from the brain.

The first and second nerves arise from the cerebral hemispheres.
the third and fourth arise from the midbrain.
the fifth and sixth from the pons.
the seventh to twelfth from the medulla.

Question 3

How are cranial nerves numbered? and explain the numbers and origins.

Answer 3

The cranial nerves are numbered according to their level of origin from the brain.

The first and second nerves arise from the cerebral hemispheres.
the third and fourth arise from the midbrain.
the fifth and sixth from the pons.
the seventh to twelfth from the medulla.

Question 4

Where do ascending pathways travel?

Answer 4

They travel between the spinal cord and the brain and also pass through the brainstem.

Question 5

What is the medulla?

Answer 5

It is continuous with the spinal cord through a hole in the base of the skull and the spinal cord is enclosed in the spinal canal inside the vertebral column.

Question 6

What happens if the intracranial pressure is raised due to a brain lesion or haemorrhage?

Answer 6

The pressure cannot be relieved physiologically as the cranium is a closed cavity. Raised pressure will displace the brain downwards. As a result the medulla is displaced through the foramen magnum into cranium canal. Referred to as ‘coning’.

Question 7

What does the seventh facial nerve innervate?

Answer 7

It exits the brainstem at the junction of the pons and medulla.

The facial nerves innervate the:
- the muscles of facial expression.
- taste buds on the anterior tongue.
- the stapedius muscle.

Question 8

What are the 5 nerves of CN VII?

Answer 8

Temporal - forehead muscles.
Zygomatic - eye.
Buccal - cheek and upper lip.
Mandibular - lower lip.
Cervical - platysma.

Question 9

What are the 5 nerves of CN VII?

Answer 9

Temporal - forehead muscles.
Zygomatic - eye.
Buccal - cheek and upper lip.
Mandibular - lower lip.
Cervical - platysma.

Question 10

What happens if their is damage in the middle ear?

Answer 10

It will affect all branches producing:
- facial paralysis
- loss of lacrimation
- loss of stapedius muscle

Question 11

What is cranial nerve VIII?

Answer 11

The vestibulocochlear nerve is the 8th cranial nerve supplying the inner ear.

Question 12

What does the vestibulocochlear nerves connect to?

Answer 12

It connects to the cochlear nuclei in the brainstem and the vestibular nuclei (which provide info about balance).

Question 13

What does CN IX carry?

Answer 13

The 9th cranial nerve is the glossopharyngeal nerve.
It carries:
- somatic sensory nerves to the mucosa of the pharynx and posterior tongue.
- taste sensory nerves to the posterior tongue.
- visceral sensory nerves from the carotid body and sinus forming the afferent limb of cardiovascular and respiratory reflexes in response to changes in blood pressure/chemistry.

Question 14

What happens if the 9th nerve is damaged?

Answer 14

It will result in dysphagia.

Question 15

What does CN X supply?

Answer 15

It is the tenth nerve, vagus nerve.

• Sensation to the larynx.
• motor innervation to the muscles of the soft palate, pharynx and larynx.
• parasympathetic innervation to the organs of the thorax and abdomen.

Question 16

What happens if the vagus nerve (CN X) is damaged?

Answer 16

• damage to the left recurrent laryngeal nerve from left lung disease.
• damage to both the superior laryngeal nerves and recurrent laryngeal nerves during thyroid operations.
• damage to motor nerves will result in paralysis of the soft palate, pharynx and, larynx.
• damage to the sensory nerves resulting in loss of protective reflexes in the larynx food may be inhaled into the lower respiratory tract without a cough reflex (silent aspiration).

Question 17

What does CN XI supply?

Answer 17

It is the 11th cranial nerve (accessory nerves).

They supply:
- sternocleidomastoid and trapezius muscles (strong elevators of the shoulders).

Question 18

What does CN XII supply and how is it tested?

Answer 18

It is the 12th nerve (hypoglossal). It is purely a motor nerve supplying the muscles of the tongue.

Tested by asking client to protrude their tongue.