Professor Long's Lecture: Sensory Physiology of Equilibrium and Hearing

Introduction

• Instructor: Professor Bob Long
• Course: Human Anatomy and Physiology 2
• Institution: Del Mar College
• Context: Online video lectures due to coronavirus shutdown
• Focus: Sensory physiology related to equilibrium and hearing, specifically in the inner ear

Overview of the Inner Ear

• Key Structures: Cochlea, vestibule, semicircular canals
• Semicircular Canals: Three loops responsible for detecting rotation and equilibrium
  • Anterior
  • Lateral
  • Posterior

Inner Ear Anatomy

• Bony Labyrinth: Maze of bone structures
  • Includes the cochlea, vestibule, semicircular canals
• Membranous Labyrinth: Flexible structure inside the bony labyrinth, hollow and filled with fluid
  • Contains endolymph (inside the membranous)
  • Surrounded by perilymph (between membranous and bony)

Function of Fluids

• Endolymph & Perilymph: Crucial for sensory functions of equilibrium and hearing
• Filtering of Fluids: Similar to cerebrospinal fluid in its function for neurons, this fluid is crucial for nerve cell function

Equilibrium

• Cochlea: Monitors hearing (audition)
• Vestibule and Semicircular Canals: Part of the vestibular complex, monitor balance and equilibrium
  • Vestibular Nerve: Formed by axons from utricle, saccule, and semicircular canals
  • Cranial Nerve VIII: Vestibulocochlear nerve, a fusion of vestibular nerve and cochlear nerve

Semicircular Canals and Rotation Detection

• Anterior Canal: Detects anterior-posterior rotation (e.g., headbanging)
• Lateral Canal: Detects horizontal rotation (e.g., spinning like a skater)
• Posterior Canal: Detects lateral rotation (e.g., doing cartwheels)
• Mechanism: Movement of cupula, gelatinous structure, and crista ampullaris (sensory hair cells)

Utricle and Saccule

• Function: Detect angular/linear movement and gravitational forces
• Structure: Macula containing sensory hair cells topped with otoliths (tiny crystals)
• Mechanism: Movement of otoliths lagging behind during motion indicating direction and acceleration

Conditions Affecting Equilibrium

• Vertigo: Feeling of dizziness or imbalance
  • Causes include inner ear infections, displaced otoliths, sinus infections
• Therapeutic Maneuvers: Certain body positions can help rebalance otoliths
• Impacts of Sinus and Ear Infections: Can lead to dizziness due to fluid pressure changes

Conclusion

• Next video will cover hearing
• Understanding equilibrium is crucial for comprehending the overall sensory system of the inner ear

These notes provide a comprehensive overview of the inner ear's role in equilibrium and hearing, focusing on the anatomy and physiology essential for understanding human sensory systems.