Cranial Nerves Lecture Notes

Overview of Cranial Nerves

• Total Cranial Nerves: 12
• Named Cranial Nerves: Emergent from the cranium
• Identification: Numbered using Roman numerals from anterior to posterior
• Structure: Emerge from the brainstem (pons, medulla oblongata)

Roman Numerals for Cranial Nerves

• Key Numerals:
  • I = 1
  • V = 5
  • X = 10
• Combinations:
  • I before V = 4, I after V = 6
  • I before X = 9
  • Two after X = 12

Names and Functions of Cranial Nerves

1. Olfactory (I): Smell - Sensory
2. Optic (II): Vision - Sensory
3. Oculomotor (III): Eye movement, raises eyelid, constricts pupil - Motor
4. Trochlear (IV): Eye movement (superior oblique muscle) - Motor
5. Trigeminal (V): Facial sensations, chewing - Both
6. Abducens (VI): Eye movement (lateral rectus muscle) - Motor
7. Facial (VII): Facial expressions, taste, salivary glands - Both
8. Vestibulocochlear (VIII): Hearing and balance - Sensory
9. Glossopharyngeal (IX): Taste, swallowing, speech - Both
10. Vagus (X): Heart rate, digestion, throat sensations - Both
11. Accessory (XI): Neck and shoulder movement - Motor
12. Hypoglossal (XII): Tongue movement - Motor

Mnemonic Devices

• Names: "On occasion, our trusty truck acts funny, very good vehicle anyhow."
• Functions: "Some say merry money but my brother says it's bad business to marry money."

Detailed Functions

Olfactory Nerve (I)

• Sensory: Smell
• Testing: Smell detection through nostrils

Optic Nerve (II)

• Sensory: Vision
• Testing: Covering one eye to check vision

Oculomotor Nerve (III)

• Motor: Eye movement, pupil constriction
• Testing: Eye movement and pupil response

Trochlear Nerve (IV) and Abducens (VI)

• Motor: Both control different eye muscles
• Functionality in Eye Movement

Trigeminal Nerve (V)

• Both: Facial sensation, mastication
• Branches:
  • V1: Ophthalmic
  • V2: Maxillary
  • V3: Mandibular
• Procedure: Numbing for dental work

Facial Nerve (VII)

• Both: Facial expressions, taste
• Branches: Temporal, Zygomatic, Buccal, Mandibular, Cervical

Vestibulocochlear Nerve (VIII)

• Sensory: Balance and hearing
• Conditions: Vertigo and cochlear implants

Glossopharyngeal Nerve (IX)

• Both: Taste, swallowing, speech
• Clinical Relevance: Speech pathologies

Vagus Nerve (X)

• Both: Swallowing, heart rate, digestion
• Importance: Longest cranial nerve affecting multiple systems

Accessory Nerve (XI)

• Motor: Moves trapezius, sternocleidomastoid, aids in speech
• Testing: Shoulder shrugs and head rotation

Hypoglossal Nerve (XII)

• Motor: Tongue movement
• Functionality: Speech and swallowing

Clinical Relevance

• Nerve Palsy: Refers to dysfunction, e.g., "cranial nerve 9 palsy."
• Importance: Knowing functions and numbers is crucial in clinical settings.