4.1 Cranial Nerve Functions Flashcards
CNI
Sensory
Sense of smell
CNII
Sensory
Vision
CNIII
Motor
Extracular msucles:
Superior branch: SR
Inferior branch: IR, MR, IO
Autonomic
Sphincter pupillae
Ciliary muscles - accommodation
CNVI
Motor
SO
CNV1
FNP structures
Skin Ant scalp Forehead Upper eyelid Dorsum of nose
Eye
Conunctiva
Cornea
Iris
Dura in anterior cranial fossa
Mucosa of nasal cavity
Frontal sinus
Ethmoidal sinus
Parasympathetic Supply
Lacrimal gland
Post ganglionic fibres from the pterygopalatine ganglion join lacrimal branch of V1.
CNV2
Sensory Function
• Skin o Lower eyelid o Side of nose o Cheek o Upper lip • Dura in middle cranial fossa • Nasopharynx • Palate mucosa • Nasal cavity mucosa • Teeth and gums of upper jaw • Maxillary sinus
Parasympathetic Function
• Lacrimal gland
o Postganglionic fibres from pterygopalatine ganglion travel with zygomatic branch of V2 to join lacrimal branch of V1.
• Nasal glands
o Parasympathetic fibres are also carried to the mucous glands of the nasal mucosa.
o Postganglionic fibres travel with the nasopalatine and greater palatine nerves (branches of V2)
CNV3
Sensory Function
• Skin o Lower face o Cheek o Chin o Lower lip o Anterior part of external ear o Temporal region • Lower teeth and gums • Mucosa of the cheek • Anterior 2/3rd of tongue (general sensation NOT special) • Mastoid air cells • Mandible • Dura in the middle cranial fossa
Motor Function
• Innervates the muscles of mastication o Temporalis o Masseter o Medial pterygoid o Lateral pterygoid • Tensor tympani • Tensor veli palatine • Anterior belly of digastric • Mylohyoid
Parasympathetic Supply
• Submandibular and sublingual glands
o Postganglionic fibres from the submandibular region (derived form the facial nerve), travel with the lingual nerve to innervate these glands.
• Parotid gland
o Postganglionic fibres from the otic ganglion (derived from the glosspharyngeal nerve) travel with the auricotemporal branch to innervate the parotid gland)
CNVI
LR6
CNVII
- Nerve to stapedius supplies the stapedius muscle in the inner ear
- Posterior auricular nerve supplies the intrinsic and extrinsic muscles of the outer ear and the occipital part of the occipitofrontalis muscle.
- Nerve to the posterior belly of digastric
- Nerve to the stylohyoid
- Temporal branch – frontalis, orbicularis oculi, corrugator supercilii
- Zygomatic branch – orbicularis oculi
- Buccal branch – orbicularis oris, buccinators, zygomaticus
- Marginal Mandibular branch – mentalis
- Cervical branch – platysma
Special Sensory Function
• Chorda tympani branch supplies taste buds of the anterior 2/3rds of tongue
Parasympathetic Function
- Parasympathetic secretomotor to submandibular and sublingual salivary glands via the chorda tympani
- Parasymathetic secretomotor to glands of nasal mucosa, paranasal sinuses, palates and the lacrimal gland via the greater petrosal nerve
CNVIII
Hearing Balance
CNIX
Sensory Function
• Tympanic nerve arises as the nerve passes the jugular foramen.
o It penetrates the temporal bone and enters the middle ear where it forms the tympanic plexus – a network of nerves that supply sensory innervation to the middle ear, internal surface of the tympanic membrane and Eustachian tube.
• Carotid sinus nerve arises at the level of stylopharyngeus.
o Descends down neck to innervate both the carotid sinus and the carotid body, providing information regarding blood pressure and oxygenation.
• Terminates by splitting into:
o Pharyngeal branch
• Forms pharyngeal plexus
• Innervates the mucosa of the oropharynx
o Lingual branch (Special Sensory)
• Provides posterior 1/3 of tongue with general and taste sensation
o Tonsillar branch
• Forms the tonsillar plexus, which innervates the palatine tonsils.
Motor Function
• Stylopharyngeus muscle
o Acts to shorten and widen the pharynx and elevate the larynx during swallowing
Parasympathetic Function
- Visceromotor innervation to the parotid gland.
- These fibres originate in the inferior salivatory nucleus of CN XI.
- They travel with the tympanic nerve to the middle ear.
- From here, they continue as the lesser petrosal nerve before synapsing at the otic ganglion.
- The fibres the travel to the parotid where they have a secretomotor effect.
CNX
Sensory Function
• Somatic sensory (skin and muscles) provided by auricular nerve:
o Skin of the posterior part of the external auditory canal and external ear
• Visceral sensory (organs)
o Larygopharynx – via internal laryngeal nerve
o Superior larynx – via internal laryngeal nerve
o Heart – via cadiac branches
o GI tract – via terminal branches
• Special sensory
o Taste in root of tongue and epiglottis
Motor Function
• Muscles of the pharynx o Pharyngeal branches • Superior, middle and inferior pharyngeal constrictor muscles • Palatopharyngeus • Salpingopharyngeus o (All except sylopharyngeus – glosspharyngeal) • Muscles of the larynx o Recurrent laryngeal nerve • Thyro-arytenoid • Posterior crico-arytenoid • Lateral crico-arytenoid • Transverse and oblique arytenoids • Vocalis o External laryngeal nerve • Cricothyroid • Muscles of the palate except tensor veli palatine
Parasympathetic Function
• Heart
o Cardiac branches convey parasympathetic innervation to the SA node and AV node.
o Stimulate a reduction in resting heart rate producing a rhythm of 60-80bpm.
• In vagus nerve lesion, resting heart rate = 100bpm
• GI tract
o Up to splenic flexure (sharp bend between transverse/descending colon)
o Stimulates smooth muscle contraction and glandular secretion.
CNXI
Motor Function
• Sternocleidomastoid
o From mastoid process of the temporal bone to the manubrium and the medial third of the clavicle.
o Lateral flexion and rotation of the neck when acting unilaterally.
o Extension of the neck at the atlanto-occipital joints when acting bilaterally.
• Trapezius
o From base of the skull and spinous processes of C7-T12 to the lateral third of the clavicle and acromion.
o Upper fibres elevate scapula and rotate during >90O abduction
o Middle fibres retract scapula
o Lower fibres depress scapula
CNXII
Motor Function
- Extrinsic and intrinsic muscles of the tongue
- C1.C2 roots innervate the strap muscles of the neck
