Cranial Nerves Flashcards
How many cranial nerves is there?
12
How would nerves be prone to compression?
Inflammation
Tumours
Fractures
What type of fibres may cranial nerves contain?
Somatic motor Visceral motor Visceral sensory General sensory Special sensory
What does somatic motor fibres supply?
Striated muscle
What do visceral motor fibres supply?
Parasympathetic supply innervating smooth muscles and glands
What do visceral sensory fibres do?
Afferent inputs from pharynx, larynx, heart, lung gut etc
What do general sensory fibres do?
Afferent inputs (e.g. touch, temp, pain) from skin and mucous membranes
What is involved in special sensory fibres?
Taste Smell Vision Hearing Balance
Neumonic to remember the cranial nerves
OOH To Touch And Feel Very Green Vegetables AH
What is CNI?
Olfactory
What is CNII?
Optic
What is CNIII?
Oculomotor
What is CNIV?
Trochlear
What is CNV?
Trigeminal
What is CNVI?
Abducent
What is CNVII?
Facial
What is CNVIII?
Vestibulocochlear
What is CNIX?
Glossopharyngeal
What is CNX?
Vagus
What is CNXI?
Accessory
What is CNXII?
Hypoglossal
Function of CNI
Sensory - smell
Function of CNII
Sensory - vision
Function of CNIII
Motor - eye movement
Function of CNIV
Motor - eye movement
Function of CNV
Mixed
- sensation from face and mouth
- muscles of mastication
Function of CNVI
Motor - eye movement
Function of CNVII
Mixed
- muscles of facial expression
- parasympathetic
- taste
Function of CNVIII
Sensory
- hearing
- balance
Function of CNIX
Mixed
- swallowing
- sensation from tongue
- parasympathetic
Function of CNX
Mixed
- muscles of throat
- parasympathetic
- visceral sensory
Function of CNXI
Motor
- soft palate
- throat
- neck
Function of CNXII
Motor - tongue
Pathway of olfactory nerve
Receptors in olfactory epithelium of the nasal cavity
Olfactory nerve fibres pass through foraminifera in cribriform plate of ethmoid bone
Enter olfactory bulb in anterior cranial fossa
Pathway of optic nerve
Enters via optic canal
Nerves join to form optic chiasm
Fibres from medial (nasal) half of each retina cross to form the optic tract
What can increased CSF pressure do to the optic nerve?
Cause papilledema
What would section of the right optic nerve cause?
Blindness through the right eye
What would section of the optic chiasm cause?
Loss of peripheral vision (bitemporal hemianopia)
What would section of the right optic tract cause?
Blindness in the left temporal and right nasal fields (left homonymous hemianopsia)
Pathway of the oculomotor
Emerges from midbrain
Exits via superior orbital fissure
What does the oculomotor nerve (CNIII) supply?
Somatic motor
- extraocular muscles (SR, MR, IR + IO)
- eyelid - LPS
Visceral motor
- parasympathetic to pupil causing constriction
- ciliary muscle causing accommodation of the lens
Pathway of the trochlear nerve
Emerges from dorsal surface of the midbrain
Exits via superior orbital fissure
Which extraocular muscle does the trochlear nerve give supply to?
Superior oblique
If the trochlear nerve was damaged, what would be seen?
Diplopia when looking down
Pathway of abducent nerve
Emerges between pons and medulla
Exits via superior orbital fissure
Which extraocular muscle does the abducent muscle supply?
Lateral rectus
The 3 trigeminal nerves
CNV1 - ophthalmic
CNV2 - maxillary
CNV3 - mandibular
Pathway of the ophthalmic division of the trigeminal nerve (CNV1)
Emerges from pons
Travels through trigeminal ganglion
Exists via superior orbital fissure
Function of CNV1
General sensory - cornea - forehead - scalp - eyelids - nose - muscosa of nasal cavity and sinuses
Pathway of the maxillary division of the trigeminal nerve
Emerges from pons
Travels through trigeminal ganglion
Exits via foramen rotundum
Function of CV2
General sensory
- face over maxilla
- maxillary teeth
- temporomandibular joint
- mucosa of nose
- maxillary sinuses
- palate
Pathway of the mandibular division of the trigeminal nerve (CNV3)
Emerges from the pons
Travels through the trigeminal ganglion
Exists via foramen ovale
Function of CNV3
General sensory - face over mandible - mandibular teeth - temporomandibular joint - mucosa of mouth - anterior 2/3rds of tongue Somatic motor - muscles of mastication - part of digastric - tensor veli palatinin - tensor tympani
Pathway of facial nerve
Emerges between pons and medulla
Exits via internal acoustic meatus, facial canal and stylomastoid foramen
Function of facial nerve
Somatic motor - muscles of facial expression - scalp - stapedius of middle ear - part of digastric muscle Visceral motor - parasympathetic innervation of submandibular and sublingual salivary glands, lacrimal glands, glands of nose and palate Special sensory - taste from anterior 2/3rds of tongue - soft palate General sensory from external acoustic meatus
Why is the facial nerve frequently injured?
Due to its long pathway through the bone
What is a common condition that occurs when the facial nerve is damaged?
Bells palsy
Features of bells palsy
Cannot frown
Close eyelid
Bare teeth
Pathway of vestibulocochlear nerve
Emerges between pons and medulla
Exits via internal acoustic meatus
Divides into vestibular and cochlear nerves
What does the vestibulochochlear nerve divide into?
Vestibular nerve
Cochlear nerve
Function of vestibulocochlear nerve
Special sensory (sense of position and movement)
- vestibular sensation from semi-circular ducts
- utricle
- saccule
- hearing from spiral organ
Pathway of glossopharyngeal nerve
Emerges from medulla
Exits via jugular foramen
Function of glossopharyngeal nerve
Special sensory
- taste from posterior 3rd of tongue
General sensory
- cutaneous sensations from middle ear and posterior oral cavity
Visceral sensory
- Sensation from carotid body and carotid sinus
Visceral motor
- parasympathetic innervation of the parotid gland
Somatic motor
- stylopharyngeus
- helps with swallowing
Pathway of the vagus nerve
Emerges from medulla
Exits via jugular canal
Goes everywhere
Function of vagus nerve
Special sensory - taste from epiglottis and palate General sensory - sensation from auricle - external acoustic meatus Visceral sensory - pharynx - larynx - trachea - bronchi - heart - oesophagus - stomach - intestine Visceral motor - parasympathetic innervation muscle in bronchi, gut, heart Somatic motor - pharynx - larynx - palate - oesophagus
What would damage to the pharyngeal branches of the vagus nerve cause?
Difficulty in swallowing
What would damage to the laryngeal branches of the vagus nerve cause?
Difficulty in speaking
Pathway of the accessory nerve
Small cranial (medulla) and large spinal routes exit via jugular foramen
Function of accessory nerve
Somatic motor
- striated muscle of soft palate, pharynx and larynx
- sternocleidomastoid
- trapezius
Pathway of hypoglossal nerve
Emerges from medulla
Exits through hypoglossal canal
Function of hypoglossal nerve
Somatic motor to muscles of the tongue
When is the hypoglossal nerve vulnerable to damage?
During tonsillectomy
If the hypoglossal nerve was damaged, what would be the presentation?
Paralysis and atrophy of the ipsilateral half of the tongue
Tip deviates towards the affected side