Cranial Nerves Flashcards
CN I- olfactory
CN II- Optic
CN III- oculomotor
CN IV- trochlear
CN V- trigeminal
CN VI- abducens
CN VII- facial
CN VIII- vestibulocochlear
CN IX- glossopharyngeal
CN X- vagus
CN XI- spinal accessory
CN XII - hypoglossal nerve
Modality- General somatic efferent
Nucleus- hypoglossal nucleus
Location- medulla
Distribution- motor Innervation to all tongue muscles except palatoglossus(vagus)
Landmarks: joined by C1
- passes between hyoglossus and mylohyoid
Branches- CN XII itself
-branches of C1- meningeal branch, superior root of Ansa cervicalis, nerve to thyrohyoid, nerve to geniohyoid
Course:
1. Arises from hypoglossal nucleus in floor of fourth ventricle
2. Exits brain in pre olivary fissure
3. Two roots pierce dura mater, enter hypoglossal canal, unite and leave cranial cavity
4. Lies deep to IJV,ICA CN IX, X and XII
5. Runs between ICA and ECA within carotid triangle
6. Run deep to styloid process and posterior belly of digastric
7. Through mylohyoid muscle and enters sublingual region to supply muscles of the tongue.
Lesion: by head and neck malignancy, penetrating traumatic injuries or dissection of ICA. hyoglossus nerve palsy; acute pain.
- Patients will present with deviation of tongue towards damaged side on protrusion as well as possible muscle wasting and fasciculations on affected side
Discuss the temporal fossa
Boundaries: Bound by temporal lines above and zygomatic arch below
Roof(lateral wall)- temporalis fascia
Floor(medial wall)-pterion
Anterior wall- zygomatic process of frontal bone, zygomatic bone and maxilla
Contents: temporalis muscle which arises from the floor and overlying fascia
Sensory stuff
Sensation- perception of a stimulus, which can be from external or internal environment; classified as special and general sensations.
Sensory receptors- structures detect stimuli; convert physical energies of stimulus to biolectric impulses (action potentials) that can be transmitted by sensory neurons; classified as mechano-, thermo-, chemo-, photo-, and nociceptors.
Sensory organs- body organ that houses particular sensory receptors; examples include the skin, eye, tongue etc.
Types of sensory modalities
Special sensations: relayed by cranial nerves exclusively
1. Visual- sight
2. Olfactory- smell
3. Gustatory- taste
4. Auditory function- hearing
5. Vestibular functions- equilibrium of the head
General sensations: not limited to head and cranial nerves
1. Pain
2. Temperature - heat and cold
3. Tactile sensation - discriminate touch
4. Pressure
5. Stretch
6. Vibratory
7. Proprioception