Cranial nerves (nuclei and central connections)

Question 1

Which cranial nerve(s) originate from the midbrain?

Answer 1

Trochlear nerve (CN IV)

Question 2

Which cranial nerve(s) originate from the midbrain/pontine junction?

Answer 2

Oculomotor nerve (CN III)

Question 3

Which cranial nerve(s) originate from the pons?

Answer 3

Trigeminal nerve (CN V)

Question 4

Which cranial nerve(s) originate from the pontine/medulla junction?

Answer 4

Abducens (CN VI), facial (CN VII) and vestibulocochlear (CN VIII)

Question 5

Which cranial nerve(s) originate from the medulla oblongata?

Answer 5

Glossopharyngeal (CN IX), vagus (CN X) & hypoglossal (CN XII)

Question 6

Where do the olfactory (CN I) and optic nerves (CN II) originate from?

Answer 6

Cerebrum

Question 7

All the cranial nerves exit the brain anteriorly except two, which are?

Answer 7

Trochlear (CN IV) which exits posteriorly and vestibulocochlear (CN XIII) which exits laterally

Question 8

Which cranial nerves are sensory, motor and mixed?

Answer 8

Some - sensory (CN I) olfactory Say - sensory (CN II) optic Marry - motor (CN III) oculomotor Money - motor (CN IV) - trochlear But - both sensory and motor (CN V) - trigeminal My - motor (CN VI) - abducens Brother - both (CN VII) - facial Says - sensory (CN VIII) - vestibulocochlear Big - both (CN IX) - glossopharyngeal Brains - both (CN X) - vagus Matter - motor (CN XI) - accessory Most - motor (CN XII) - hypoglossal

Question 9

What does the olfactory nerve supply?

Answer 9

Smell - purely sensory function

Question 10

What does the oculomotor nerve supply?

Answer 10

Somatic motor to levator palpebrae superioris, medial rectus, superior rectus, inferior rectus and inferior oblique muscles Parasympathetic to sphincter pupillae ciliary muscle

Question 11

What does the trochlear nerve supply?

Answer 11

Somatic motor to superior oblique muscle Remember LR 4 SO 6 AO 3 - lateral rectus 6, superior oblique 4, all others 3

Question 12

What does the abducens nerve supply?

Answer 12

Somatic motor to lateral rectus muscle - LR6, SO4, AO3

Question 13

What does the hypoglossal nerve supply?

Answer 13

Somatic motor to hypoglossus, genioglossus, styloglossus and intrinsic muscles of the tongue (basically all intrinsic and extrinsic muscles of the tongue except palatoglossus)

Question 14

What does the spinal accessory nerve supply?

Answer 14

Somatic motor to trapeziusa and sternocleidomastoid muscles

Question 15

What does the trigeminal nerve supply?

Answer 15

Ophthalmic- somatic sensory to scalp, forehead and nose Maxillary - somatic sensory to cheeks, lower eye lid, nasal mucosa, upper lip, upper teeth and palate Mandibular - somatic sensory to anterior 2/3 tongue, skin over mandible and lower teeth + somatic motor to muscles of mastication, tensor tympani, mylohyoid, anterior belly of digastric & tensor veli palatini

Question 16

The sensory nucleus of the trigeminal nerve forms a long column of neurons that stretches from the midbrain down to the upper 2 segments of the cervical spinal cord. It has 3 parts, separated by function, name these

Answer 16

Mesencephalic nucleus - proprioception info from chewing muscles Pontine trigeminal nucleus - discriminative touch, vibration Spinal nucleus - pain & temperature

Question 17

What does the facial nerve supply?

Answer 17

Somatic motor to muscles of facial expression and stapedius muscle Parasympathetic innervation to pterygopalatine ganglia and submandibular, lacrimal and sublingual glands Taste to anterior 2/3 of tongue via chorda tympani Somatic sensory to external part of ear

Question 18

What does the glossopharyngeal nerve supply?

Answer 18

Somatic sensory to posterior 1/3 of tongue, external ear, middle ear cavity, pharyngotympanic tube and upper pharynx. Taste (posterior 1/3 of the tongue). Parasympathetic fibres to the otic ganglion (parotid gland). Motor (one muscle: stylopharyngeus)

Question 19

What does the vagus nerve supply?

Answer 19

Somatic sensory to the external ear, pharynx and larynx Visceral sensory to the pharynx, larynx, trachea, oesophagus and thoracic and abdominal viscera. Taste from epiglottis region of tongue Parasympathetic innervation to ganglia serving thoracic and abdominal viscera. Motor (striated muscle of the pharynx and larynx) (cranial accessory contributes to this function)

Question 20

Name the 4 nuclei of the glossopharyngeal nerve

Answer 20

Solitary nucleus (taste), spinal trigeminal nucleus (somatosensation to ear), salivatory nucleus (parasympathetic) and nucleus ambiguus (stylopharyngeus)

Question 21

What are the 4 nuclei of the vagus nerve?

Answer 21

Dorsal nucleus (parasympathetic), solitary nucleus (taste), spinal trigeminal nucleus (pain from dura and small region of somatosensation associated with the ear) and nucleus ambiguus (motor)

Question 22

The solitary nucleus is shared by more than one cranial nerve, name these cranial nerves

Answer 22

Facial, glossopharyngeal and vagus - supplies taste and visceral sensory information

Question 23

The salivatory nuclei (inferior and superior) is shared by more than one cranial nerve, name these nerves

Answer 23

Facial and glossopharyngeal - parasympathetic efferents to ganglia of salivary glands and pterygopalatine ganglion

Question 24

The nucleus ambiguus is shared by more than one cranial nerve, name these cranial nerves

Answer 24

Glossopharyngeal and vagus - motor efferents to muscles of pharynx, larynx and upper oesophagus

Question 25

The solitary nucleus extends in a V-shape from the upper medulla to the lower medulla and is involved in taste and general visceral sensations. Which cranial nerves have a solitary nucleus and what role does it play for each nerve?

Answer 25

CN VII (facial) - taste to anterior 2/3 of tongue CN IX (glossopharyngeal) - taste to posterior 1/3 of tongue CN X (vagus) - taste to epiglottis region of tongue

Question 26

The commissural nucleus is attached to the solitary nucleus as part of the v-shape. What role does the commissural nucleus play in CNs IX & X?

Answer 26

CN IX (glossopharyngeal) - visceral afferents to carotid body and sinus CN X (vagus) - visceral afferents to aortic arch and viscera e.g. pulmonary stretch receptors

Question 27

What is the corticobulbar tract?

Answer 27

The part of the corticospinal (pyramidal) tract that is motor to cranial nerves V (trigeminal), VII (facial), X (vagus) and XII (hypoglossal)

Question 28

What is unusual about the cortical input to the facial nucleus?

Answer 28

The input to the facial nucleus is only bilateral to the part that controls muscles of the upper face (forehead and around the eyes). Only a crossed input reaches the part of the facial nucleus that controls muscles in the lower half of the face.

Question 29

Identify labels A-J

Answer 29

A = Hypoglossal

B = Spinal accessory

C = Vagus

D = Glossopharyngeal

E = Facial

F = Vestibulocochlear

G = Abducens

H = Trigeminal

I = Oculomotor

J = Trochlear

Question 30

What is the reticular formation?

Answer 30

A network of loosely aggregated cells with cell bodies, axons and dendrites intermingling in the central core of the brainstem. It is distinct from the long pathways (like the medial lemniscus, or the corticospinal tract) and the specific distinct cell groups (like cranial nerve nuclei)

Question 31

What are some of the functions of the reticular formation centres?

Answer 31

•Integrate cranial nerve reflexes.

Participate in conduction and modulation of pain.

Influence voluntary movement.

Regulate autonomic activity.

Integrate some basic functions, like respiration and sleep.

Activate the cerebral cortex: major component of the Ascending Reticular Activating System (a medial bilateral lesion of the brainstem reticular formation at or above the upper pons causes irreversible coma)