Cranial nerves Flashcards by Michael Alcorn

What types of nerves can be in cranial nerves?

Somatic motor fibres:

Supply striated muscle

Autonomic motor fibres (aka visceral motor fibres):

Parasympathetic - supplies smooth muscle & glands

Visceral sensory/afferent:

inputs from pharynx, larynx, heart, lung, gut etc - not normally conscious

General sensory:

Touch, temp etc from skin & mucous membranes

Special sensory:

taste, smell, vision, hearing & balance

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Why is there no sympathetic motor fibres in the cranial nerves?

Parasympathetic outflow is Craniosacral

Sympathetic outflow is Thoracolumbar thus cant be through any cranial nerves

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Where are the cell bodies located for:

Sensory (afferent) fibres?
Somatic motor (efferent) fibres?
Autonomic motor (efferent) fibres?

Sensory (afferent):

Cell bodies located within ganglia that are outside of the CNS (ie dorsal root ganglia)

Somatic motor (efferent):

Cell bodies located within the CNS in ‘Nuclei’

Autonomic motor (efferent):

Pre-ganglionic fibres have cell bodies within the CNS
Post-ganglionic fibres have theirs in autonomic ganglia (outside of the CNS)

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What type of nerve is the Olfactory nerve?

CN I

Sensory nerve (smell)

(special sensory)

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Describe the anatomical pathway that signals travel through the Olfactory nerve?

Receptors located in olfactory epithelium of nasal cavity - moves on to…
Fibres through foraminifera in cribriform plate of ethmoid bone - after which the…
Fibres enter olfactory bulb in ant. cranial fossa

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What are the clinical applications of the Olfactory nerve?

A fractured cribriform plate may tear olfactory nerve fibres causing anosmia

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What type of nerve is the Optic nerve?

CN II

Special sensory - vision

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What is the pathway of the Optic nerve?

CN II

enters via optic canal, nerves join to form optic chiasm, fibres from medial (nasal) half of each retina cross to form optic tract

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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)

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What type of nerve is the Oculomotor nerve?

CN III

Motor - eye movement

Has both a Somatic and Autonomic aspect:

Somatic motor - Extraocular muscles & eyelid
Autonomic motor - Parasympathetic Pupil control

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Describe the pathway of the Occulomotor nerve

CN III

Emerges from midbrain and exits via superior orbital fissure into orbit

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What are the clinical applications of the oculomotor nerve?

CN III

–drooping of upper eyelid (ptosis)

–eyeball abducted and pointing down

–no pupillary reflex

–no accommodation of the lens

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What type of nerve is the trochlear nerve?

CN IV

Somatic motor - eye movement

Motor information to superior oblique

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What is the pathway of the trochlear nerve?

CN IV

emerges from dorsal surface of the mid brain and exits via the superior orbital fissure

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What are the clinical applications of the trochlear nerve?

Diplopia when looking down

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What type of nerve is the Abducens nerve?

CN VI

somatic motor - extraocular muscle (lateral rectus abducts the eye)

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What is the pathway of the abducent nerve?

CN VI

emerges between pons and medulla and exits via the superior orbital fissure

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What is the clinical application of the Abducent nerve?

CN VI

Medial deviation of the affected eye causing diplopia

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What type of nerve is the Trigeminal nerve?

CN V

mixed (sensation from face & mouth, muscles of mastication)

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What 3 nerves does the Trigeminal nerve give rise to?

Ophthalmic nerve - CN V₁

General sensory

Maxillary nerve - CN V₂

General sensory

Mandibular nerve - CN V₃

General sensory
Somatic motor

What is the pathway of the Ophthalmic nerve?

CN V₁

emerges from the pons, travels through the trigeminal ganglion and exits via the superior orbital fissure

What areas are innervated by the Ophthalmic nerve?

General sensory - from cornea, forehead, scalp, eyelids, nose and mucosa of nasal cavity and sinuses

Describe the pathway of the Maxillary nerve

CN V₂

Emerges from the pons, travels through the trigeminal ganglion and exits via the foramen rotundum

What areas are innervated by the Maxillary nerve?

CN V2

General sensory - from face over maxilla, maxillary teeth, temperomandibular joint, mucosa of nose, maxillary sinuses and palate

Describe the pathway of the Mandibular nerve

CN V₃ emerges from the pons, travels through the trigeminal ganglion and exits via the foramen ovale

Describe the functions of the mandibular nerve

CN V₃ **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 palatini & tensor tympani

What possible conditions can arise due to damage of the Mandibular nerve?

CN V₃ Paralysis of muscles of **mastication** Loss of **corneal** or sneezing reflex Loss of **sensation** in face Trigeminal **neuralgia**

Describe the pathway of the facial nerve

CN VII emerges between pons and medulla and exits via internal acoustic meatus, facial canal and stylomastoid foramen

What are the functions of the facial nerve?

CN VII **Somatic motor** * muscles of facial expression & scalp, stapedius of middle ear, part of digastric muscle **Autonomic 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 palsy is linked to damage to the Facial nerve?

CN VII Bells Palsy - Muscles of facial expression have impacted motor innervation so can not **Frown, Close eyelid or bare teeth** Facial nerve is most frequently damaged due to long pathway through bone

Describe the pathway of the Vestibulocochlear nerve

CN VIII Emerges from between pons and medulla and passes through the internal acoustic meatus - dividing into vestibular and cochlear nerves once through

What is the function of the vestibulocochlear nerve?

CN VIII **Special sensory:** * **Vestibular sensation** - from semicircular ducts, utricle, saccule gives sense of position & movement * **Hearing** - from spiral organ

What conditions may arise from damage to the vestibulocochlear nerve?

CN VIII * Tinnitus (ringing in the ears) * Deafness (sensorineural?) * Vertigo (loss of balance nae feart ah heights) * Nystagmus (involuntary rapid eye movements)

What are the functions of the Glossopharyngeal nerve?

CN IX _Special sensory_ - Taste from posterior 1/3rd tongue _General Sensory_ - Cutaneous sensations from middle ear and posterior oral cavity _Visceral sensory_ - Carotid body & carotid sinus (BP regulation) _Autonomic motor_ - Parasympathetic innervation of Parotid gland _Somatic motor_ - to Stylopharyngeus (helps with swallowing)

What are the indications that there has been damage to the Glossopharyngeal nerve?

CN IX Loss of Gag reflex and Taste sensation in posterior 1/3rd of tongue Also associated with damage to Vagus (X) and Accessory (XI) nerves (jugular foramen syndrome)

What is the pathway of the glossopharyngeal nerve?

CN IX Emerges from Medulla and exits via Jugular foramen

What is the pathway of the Vagus nerve?

CN X Emerges from medulla and exits via jugular foramen, then cuts about everywhere

What are the functions of the vagus nerve?

CN X _Special sensory:_ * Taste from epiglottis & palate _General sensory:_ * Sensation from Auricle & external acoustic meatus _Visceral Sensory:_ * pharnyx, larynx, trachea, bronchi, heart, oesophagus, stomach, intestine (basically organs with some sort of Parasympathetic link) _Autonomic motor:_ * Parasympathetic innervation of muscle in **bronchi, gut, heart** _Somatic motor:_ * Pharynx, larynx, palate, oesophagus

What clinical conditions are linked to vagus nerve damage?

Difficulty swallowing - Damage to pharyngeal branches of Vagus Difficulty speaking - Damage to laryngeal branches of Vagus

What is the function of the Accessory nerve?

CN XI Somatic motor - Sternocleidomastoid & trapezius

In the cranial nerve examination, what signs would test for/indicate damage to the accessory nerve?

CN XI Weakness in turning head (SCM) Weakness in shrugging shoulders (Trap)

What is the pathway of the accessory nerve?

CN XI small cranial (medulla)\* and large spinal roots exit via jugular foramen \*in doubt

What is the function of the Hypoglossal nerve?

CN XII Somatic motor - Muscles of the tongue

What is the pathway of the Hypoglossal nerve?

CN XII Emerges from medulla and exits through the hypoglossal canal

For each function listed, identify the nerve(s) involved: A) Smell - B) Sight - C) Taste - D) Hearing & Balance - E) Movement of eyes -

A) Olfactory B) Optic C) Facial, Glossopharyngeal & Vagus D) Vestibulocochlear E) Oculomotor, Trochlear & Abducent

For each function listed, provide the nerve(s) that do the shit A) Accommodation of eye B) Constriction of pupil C) Movement of muscles of the face D) Sensation from the face E) Chewing (mastication)

A) Oculomotor B) Oculomotor C) Facial D) Trigeminal E) Trigeminal (mandibular)

For each function, list the Cranial nerve(s) that do it A) Swallowing B) Movement of tongue C) Movement of vocal cords D) Movement of the neck

A) Glossopharyngeal (& Accessory) B) Hypoglossal C) Vagus D) Accessory