Head and Neck Anatomy: Cranial Nerves

Introduction

• Overview of the nervous system
• Central and peripheral nervous systems
• Function and structure of the brain and spinal cord

Nervous System Breakdown

Central Nervous System

• Brain: Processes sensory information, initiates responses, stores memories, generates thoughts/emotions
  • Forebrain: Cerebrum, thalamus, hypothalamus
    • Controls temperature, reproduction, eating, sleeping, emotions
  • Midbrain: Top of the brain stem
    • Handles vision, hearing, motor control, sleep, alertness
  • Hindbrain: Medulla, pons, cerebellum
    • Supports vital functions like breathing
• Spinal Cord: Highway for neuronal signaling, reflex control

Peripheral Nervous System

• Sensory Division (Afferent): Carries information to CNS
  • Somatic Sensory: Touch, pain, pressure, temperature, proprioception
  • Special Somatic Sensory: Vision, hearing, balance
  • Visceral Sensory: Stretch, pain, temperature, hunger
• Motor Division (Efferent): Sends information from CNS
  • Somatic Motor: Voluntary, skeletal muscle
  • Visceral Motor: Autonomic nervous system
    • Sympathetic: Fight or flight
    • Parasympathetic: Rest and digest

Cranial Nerves Overview

Cranial Nerve I: Olfactory Nerve

• Special visceral sensory for smell
• Pathway: Nasal cavity -> cribriform plate -> olfactory bulb -> CNS

Cranial Nerve II: Optic Nerve

• Special somatic sensory for vision
• Pathway: Retina -> optic nerve -> optic chiasma -> lateral geniculate nucleus -> occipital lobe

Cranial Nerve III: Oculomotor Nerve

• Somatic motor to eye muscles: superior/inferior/medial rectus, inferior oblique
• Parasympathetic control for pupil constriction

Cranial Nerve IV: Trochlear Nerve

• Somatic motor to superior oblique muscle
• Arises from dorsal side of the brain stem

Cranial Nerve V: Trigeminal Nerve

• Sensory from orofacial region
• Somatic motor to muscles of mastication
• Divisions:
  • V1: Ophthalmic
  • V2: Maxillary
  • V3: Mandibular

Cranial Nerve VI: Abducens Nerve

• Somatic motor to lateral rectus muscle

Cranial Nerve VII: Facial Nerve

• Sensory from ear, tongue, palate
• Somatic motor to facial expression muscles
• Parasympathetic to salivary glands

Cranial Nerve VIII: Vestibulocochlear Nerve

• Special somatic sensory for hearing and balance

Cranial Nerve IX: Glossopharyngeal Nerve

• Touch/taste from posterior third of tongue
• Motor to stylopharyngeus muscle
• Involved in carotid sinus reflex

Cranial Nerve X: Vagus Nerve

• Sensory/motor to heart, lungs, digestive tract
• Somatic motor to pharynx/larynx muscles

Cranial Nerve XI: Spinal Accessory Nerve

• Somatic motor to sternocleidomastoid and trapezius muscles

Cranial Nerve XII: Hypoglossal Nerve

• Somatic motor to tongue muscles except palatoglossus

Conclusion

• Recap of cranial nerves and their functions
• Invitation to join Patreon for additional resources