Cranial Nerves: Sensorimotor Flashcards
What are the 7 modalities served by the cranial nerves?
Motor:
• Somatic efferent
• Special visceral efferent
• General visceral efferent
Sensory:
• Somatic afferent
• Special visceral afferent (smell, taste)
• General visceral afferent
• Special somatic afferent ( sight, hearing, balance)
What are each of the cranial nerves?
I - Olfactory II - Optic III - Occulomotor IV- Trochlear V- Trigeminal VI- Abducent VII - Facial VIII- Vestibulocochlear IX- glossopharyngeal X- Vagus XI - Accessory XII - Hypoglossal
Where is the olfactory region?
The upper third of the nasal cavity
Describe the route of the olfactory nerve
- Olfactory nerves pass through the cribriform plate (where they are anchored by the dura) and synapse at the olfactory bulb
- Axons in the olfactory bulb form the olfactory canal
- Project to the olfactory cortex then to the limbic system, hypothalamus and reticular formation (for visceral and behavioural response to odours)
What type of cells can differentiate into olfactory neurones?
- Basal cells can differentiate into (bipolar) olfactory neurones
- Can regenerate in humans
What is anosmia and what causes it?
- Olfactory neuropathy cursed by upper respiratory tract infection
- Trauma, causing the brain and olfactory bulb to move may tear the olfactory nerves
What may happen as a result of a fracture of the cribriform plate?
- CSF rhinnorhea
* Blood stained CSF leaking from the nose
What are the modalities of the divisions of the trigeminal nerve?
- V1 and V2 are afferent only
* V3 is afferent and efferent
What are the roots and nuclei of the trigeminal nerve?
Sensory root:
• Mesencephalic nucleus
• Principle (pontine) nucleus
• Spinal nucleus
Motor Root:
• Motor nucleus
Where do the roots of the trigeminal nerve emerge?
From the mid pons and run to the trigeminal ganglion
What are the divisions of the trigeminal nerve that emerge from the trigeminal ganglion?
- Ophthalmic (V1)
- Maxillary (V2)
- Mandibular (V3)
Describe the course of the ophthalmic nerve
- Runs in the lateral wall of the cavernous sinus
- Passes through the superior orbital fissure
- Into the orbit
Describe the route of the Maxillary nerve
- Runs in the lateral wall of the cavernous sinus
- Passes through foramen rotundum
- Enters the pterygopalatine fossa
Describe the course of the mandibular nerve
- Passes through foramen ovale
* Infratemporal fossa
Ophthalmic nerve
• Sensory only branch
• Picks up sympathetic fibres from the carotid plexus
• Gives off the meningeal branch near the trigeminal ganglion that supplies the dura
• 3 main branches:
- lacrimal
- frontal
- nasociliary
What are the 3 main branches of the ophthalmic nerve?
- Lacrimal
- Frontal
- Nasociliary
Function of the lacrimal nerve
- Supplies general sensation to the lacrimal gland, conjunctiva and upper eyelid in the vicinity of the lacrimal gland
- Carries parasympathetic fibres from the facial nerve (CN VII) to the lacrimal gland
Function of the frontal nerve
• Supplies the upper eyelid and conjunctiva, frontal sinus and the scalp as far back as the vertex (afferent)
What are the divisions of the frontal nerve?
- Supra-orbital
* Supra- trochlear nerve
Function of the nasociliary nerve
- Supplies the skin of the medial, upper eyelid and root of the nose
- Sensation to the cornea of the eye (corneal reflex afferent)
- Tip of the nose
What are the divisions of the nasociliary nerve?
- Gives off long ciliary nerves and anterior and posterior ethmoidal nerves
- Continues as the infratrochlear nerve
Branches of the maxillary nerve
- Zygomatic and infra-orbital branches into the orbit via the inferior orbital fissure
- Palatine and superior alveolar branches to the palate and upper teeth
Describe the route of the infra-orbital nerve
- Enters the orbit via the inferior orbital fissure
- Exits the orbit via the infra-orbital canal
- Into the infra-orbital foramen
What is the sensory supply of the maxillary nerve?
- Lateral forehead
- Zygomatic region
- Lower lid
- Side of the nose
- Cheek (anteriorly)
- Upper lip
What are the branches of the mandibular nerve?
- Auriculotemporal
- Buccal
- Lingual
- Inferior Alveolar
What is the sensory supply of the maxillary nerve?
- Skin of the auricle and temple
- Posterior cheek
- Lower lip and chin
- General sensation to the anterior 2/3 of the tongue and the floor of the mouth
- Lower gums and teeth
What is the motor supply of the mandibular nerve?
• Muscles of mastication - lateral pterygoid - medial pterygoid - masseter - temporalis • Tensor tympani • Tensor veli palatini • Mylohyoid • Anterior belly of digastric
What reflex tests the mandibular nerve?
Jaw jerk
• Tap chin with tendon hammer
What are the modalities of the oculomotor nerve?
- Somatic motor
* visceral motor
Where is the nucleus for the oculomotor nerve?
In the midbrain
Describe the course of the oculomotor nerve
- Passes between the posterior cerebral and superior cerebral arteries, before lying close to the posterior communicating artery
- Runs anteriorly on the lateral Wall of the cavernous sinus
- Passes through the superior orbital fissure and enters the orbit
- In the orbit it divides into superior and inferior divisions (rami) through the tendinous ring of zinn
What may happen as a result of an aneurysm of the posterior communicating artery?
May compress the oculomotor nerve
Superior branch of the oculomotor nerve
• Oculomotor fibres and sympathetics from the superior cervical ganglion