Cranial nerves (I, V,VII, IX, X, XI & XII)

🖇 Cranial Nerve Anatomy – Summary Notes

📌 CN I – Olfactory Nerve

🟠 Type: Sensory only (smell)
🟣 Structure & Pathway:

• Primary neurons in olfactory mucosa (roof of nasal cavity)
• Axons pass through cribriform plate → olfactory bulb
• Secondary neurons form olfactory tract, which divides into:
• • Lateral stria → Primary olfactory center
  • Medial stria → crosses via anterior commissure → opposite side
    🟣 Centers:
• Primary center: Detects smell
• Secondary centers: (frontal, parietal, temporal lobes) interpret smell

📌 CN V – Trigeminal Nerve

🟠 Type: Mixed (mainly sensory, partly motor)
🟣 Divisions: Ophthalmic (V1), Maxillary (V2), Mandibular (V3)
🟣 Motor supply:

• Muscles of mastication: Temporalis, Masseter, Medial & Lateral Pterygoids
• Mylohyoid and Anterior belly of Digastric
  🟣 Sensory nuclei:
• Main sensory nucleus: touch & pressure
• Spinal nucleus: pain & temperature
• Mesencephalic nucleus: proprioception
  🟣 Exit foramina:
• V1 → Superior orbital fissure
• V2 → Foramen rotundum
• V3 → Foramen ovale

📌 CN VII – Facial Nerve

🟠 Type: Mixed (motor, sensory, parasympathetic)
🟣 Motor:

• Facial expression muscles
• Stapedius (reduces vibration in loud sounds)
  🟣 Sensory:
• Taste from anterior 2/3 of tongue (via Chorda tympani)
  🟣 Parasympathetic:
• Lacrimal gland via Greater Superficial Petrosal Nerve
• Submandibular & Sublingual glands via Superior Salivatory nucleus
  🟣 Course:
• Enters internal acoustic meatus → through facial canal → exits stylomastoid foramen
  🟣 Main branches:
• Greater Petrosal, Nerve to Stapedius, Chorda Tympani
• In parotid gland → divides into 5 branches: Temporal, Zygomatic, Buccal, Marginal Mandibular, Cervical

📌 CN IX – Glossopharyngeal Nerve

🟠 Type: Mixed
🟣 Origin & Exit: From medulla oblongata → exits via jugular foramen
🟣 Motor: Stylopharyngeus muscle only
🟣 Sensory:

• Taste + general sensation from posterior 1/3 of tongue
• Pharyngeal sensation
  🟣 Parasympathetic:
• To parotid gland via Lesser Petrosal Nerve

📌 CN X – Vagus Nerve & CN XI – Accessory Nerve

🟠 Origin: Both from medulla oblongata, exit via jugular foramen
🟣 Vagus (CN X):

• Motor: Pharynx, larynx, soft palate (except stylopharyngeus)
• Parasympathetic: Heart, lungs, GI tract
  🟣 Accessory (CN XI):
• Cranial part: Joins CN X → forms Pharyngeal Plexus
• Spinal part: Supplies Sternocleidomastoid & Trapezius
  🚨 Note: Motor fibers to the pharynx often attributed mainly to CN X (even though CN XI contributes)

📌 CN XII – Hypoglossal Nerve

🟠 Type: Purely motor
🟣 Function: Supplies all tongue muscles
🟣 Nucleus: In Hypoglossal Triangle (floor of 4th ventricle, medulla oblongata)

🚨 Focus Points

🟣 High-yield questions:

1. Location of olfactory neuron cell bodies
2. Functions of trigeminal nuclei
3. Stapedius and Chorda Tympani roles (Facial Nerve)
4. Only muscle supplied by CN IX (Stylopharyngeus)
5. Pharyngeal Plexus composition (CN X + CN XI)
6. Hypoglossal nucleus location – Hypoglossal Triangle