FOUR CRANIAL NERVES

Question 1

origin of cranial nerves

Answer 1

Midbrain – the trochlear nerve (IV) comes from the posterior side of the midbrain. It has the longest intracranial length of all the cranial nerves.

Midbrain-pontine junction – oculomotor (III).

Pons – trigeminal (V).

Pontine-medulla junction – abducens, facial, vestibulocochlear (VI-VIII).

Medulla oblongata – posterior to the olive: glossopharyngeal, vagus, accessory (IX-XI). Anterior to the olive: hypoglossal (XII).

Question 2

1. Glossopharyngeal CNIX

Answer 2

1. jugular foramen
2. • Mixed nerve:
     • Swallowing
     • Taste (post. third of tongue)
     • Salivation (parotid)
     • Monitors carotid body + sinus
     • Supplies the stylopharyngeus muscle
     • Small amount of sensation from around the external ear

Question 3

2. VAGUS NERVE X

Answer 3

1. jugular foramen

-	Mixed nerve – subserves for: 
•	Speech 
•	Lifting of palate 
•	Swallowing 
•	Communicates with thoraco-abdominal structures 
•	Small amount around external ear 
-	Supplies motor fibres to:
•	Voluntary muscles of larynx and superior oesophagus 
-	Send visceral motor fibres to: 
•	Involuntary muscles and glands of the tracheobrochial tree and oesophagus via pulmonary and oesophageal plexuses 
•	The heart via cardiac plexus 
•	Alimentary tract 
-	Sends sensory fibres to:
•	Pharynx and larynx 

3.- Course in thorax differs between L + R (Recurrent laryngeal nerves)
 L = Arch around the arch of the aorta (T4-T5)
 R = Arch around the right subclavian artery (T1-T2)

Question 4

3. accessory nerves XI

Answer 4

1. jugula foramen
2. • Somatic motor nerve:
     • Turns head and Lifts shoulders
     • Cranial root joins vagus nerve – striated muscle of soft palate, pharynx, larynx + esophagus

Question 5

4. hypoglossal xii

Answer 5

1. hypoglossal canal
2. • Somatic motor nerve:
     • Supplies muscles of tongue
     • Conveys motor fibres from C1 + C2 spinal nerves - hyoid muscles (thyro/geniohyoid)

Question 6

remember

Answer 6

• IX, X, XII: receive branches from sup. cervical sympathetic ganglion
• XI + XII: communicate with cervical plexus