Cranial Nerve Physiology Flashcards
What is the pathway of the olfactory nerve?
Receptors in olfactory epithelium of nasal cavity, olfactory nerve fibres pass through foraminifera in cribriform plate and enter the olfactory bulb in the anterior cranial fossa
What are the component parts of the olfactory nerve?
Special sensory- smell
What are the clinical applications of the olfactory nerve?
Fractured cribriform plate may tear olfactory nerve fibres causing anosmia
What is the pathway of the optic nerve?
Enters via optic canal, nerves join to form optic chiasm, fibres from medial (nasal) half of each retina cross to form optic tract
What are the component parts of the optic nerve?
Special sensory-vision
What are the clinical applications of the optic nerve?
Increase in CSF pressure can cause papilloedema
Section of right optic nerve causes blindness through right eye
Section of optic chiasm causes loss of peripheral vision (bitemporal hemianopsia)
Section of right optic tract causes blindness in left temporal and right nasal fields (left homonymous hemianopsia)
What is the pathway of the oculomotor nerve?
Emerges from midbrain and exits via superior orbital fissure
What are the component parts of the oculomotor nerve?
Somatic motor - extraocular muscles (superior, medial & inferior rectus and inferior oblique) and eyelid (levator palpebrae superioris)
Visceral motor - parasympathetic to pupil causing constriction and to ciliary muscle causing accommodation of the lens
What is the clinical application of the oculomotor nerve?
Drooping of upper eyelid (ptosis)
Eyeball abducted and pointing down
No pupillary reflex
No accommodation of the lens
What is the pathway of the trochlear nerve?
Emerges from dorsal surface of the mid brain and exits via the superior orbital fissure
What are the component parts of the trochlear nerve?
Somatic motor - extraocular muscle (superior oblique turns eye downwards)
What are the clinical applications of the trochlear nerve?
Diplopia when looking down
What is the pathway of the ophthalmic branch of the trigeminal nerve?
Emerges from the pons, travels through the trigeminal ganglion and exits via the superior orbital fissure
What is the pathway of the maxillary branch of the trigeminal nerve?
Emerges from the pons, travels through the trigeminal ganglion and exits via the foramen rotundum
What is the pathway of the mandibular branch of the trigeminal nerve?
Emerges from the pons, travels through the trigeminal ganglion and exits via the foramen ovale
What are the component parts of the ophthalmic branch of the trigeminal nerve?
General sensory - from cornea, forehead, scalp, eyelids, nose and mucosa of nasal cavity and sinuses
What are the component parts of the maxillary branch of the trigeminal nerve?
General sensory - from face over maxilla, maxillary teeth, temperomandibular joint, mucosa of nose, maxillary sinuses and palate
What are the component parts of the mandibular branch of the trigeminal nerve?
General sensory - from face over mandible, mandibular teeth, temperomandibular joint, mucosa of mouth & anterior 2/3rds of tongue
Somatic motor - muscles of mastication, part of digastric, tensor veli palatinin & tensor tympani
What is the pathway of the abducens nerve?
Emerges between pons and medulla and exits exits via the superior orbital fissure
What is the pathway of the facial nerve?
Emerges between pons and medulla and exits via internal acoustic meatus, facial canal and stylomastoid foramen
What is the pathway of the vestibulocochlear nerve?
Emerges from between pons and medulla and exits via internal acoustic meatus, dividing into vestibular & cochlear nerves
What is the pathway of the glossopharyngeal nerve?
Emerges from medulla and exits via jugular foramen
What is the pathway of the vagus nerve?
Emerges from medulla and exits via jugular foramen, then everywhere
What is the pathway of the accessorynerve?
Small cranial (medulla) and large spinal roots exit via jugular foramen
What is the pathway of the hypoglossal nerve?
Emerges from medulla and exits through the hypoglossal canal
What are the component parts of the abducens nerve?
Somatic motor - extraocular muscle (lateral rectus abducts the eye)
What are the component parts of the facialnerve?
Somatic motor - muscles of facial expression & scalp, stapedius of middle ear, part of digastric muscle
visceral motor - Parasympathetic innervation of submandibular & sublingual salivary glands, lacrimal glands, glands of nose & palate
Special sensory - taste from anterior 2/3rd of tongue & soft palate
general sensory - from external acoustic meatus
What are the component parts of the vestibulocochlear nerve?
Special sensory - vestibular sensation from semicircular ducts, utricle, saccule gives sense of position & movement. Also hearing from spiral organ
What are the component parts of the 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 & carotid sinus
Visceral motor - parasympathetic innervation of parotid gland
Somatic motor - to stylopharyngeus, helps with swallowing
What are the component parts of the vagus nerve?
Special sensory - taste from epiglottis and palate
General sensory - sensation from auricle, external acoustic meatus
Visceral sensory - from pharnyx, larynx, trachea, bronchi, heart, oesophagus, stomach, intestine
Visceral motor - parasympathetic innervation muscle in bronchi, gut, heart
Somatic motor - to pharynx, larynx, palate & oesophagus
What are the component parts of the accessory nerve?
Somatic motor - striated muscle of soft palate, pharynx & larynx, and to sternocleidomastoid & trapezius
What are the component parts of the hypoglossal nerve?
Somatic motor - to muscles of tongue
What are the clinical applications of the abucens nerve?
Medial deviation of the affected eye causing diplopia
What are the clinical applications of the facial nerve?
Most frequently injured - due to long pathway through bone
Bell’s palsy - cannot frown, close eyelid, or bare teeth
What are the clinical applications of the vestibulocochlear nerve?
Tinnitus (ringing in the ears)
Deafness (conductive vs sensorineural)
Vertigo (loss of balance)
Nystagmus (involuntary rapid eye Movements)
What are the clinical applications of the glossopharyngeal nerve?
Loss of gag reflex and taste from back of tongue
Associated with injuries to CNs X and XI - jugular foramen syndrome
What are the clinical applications of the vagus nerve?
Damage to pharyngeal branches cause difficulty in swallowing
Damage to laryngeal branches causes difficulty in speaking
What are the clinical applications of the accessory nerve?
Weakness in turning head and shrugging shoulder
What are the clinical applications of the hypoglossal nerve?
Vulnerable to damage during tonsillectomy
Causes paralysis & atrophy of ipsilateral half of tongue. Tip deviates towards affected side
What are the clinical applications of the mandibular branch of the trigeminal nerve?
Paralysis of muscles of mastication
Loss of corneal or sneezing reflex
Loss of sensation in the face
Trigeminal neuralgia
