Sensation of Angular Movements of the Head

Overview

• Sensation of angular movements is due to motion of endolymph fluid within the vestibular system.
• Vestibular system is located in the temporal bone, in the inner ear.
• Inner ear has interconnected canals making up the bony labyrinth, responsible for balance and spatial orientation.

Inner Ear Fluids

• Perilymph: Fills the volume of the bony labyrinth.
• Membranous labyrinth: Suspended in perilymph, contains endolymph fluid.
• Endolymph: Fluid within the membranous labyrinth.

Structure of Membranous Labyrinth

• Consists of three semicircular ducts positioned in three planes:
  • Anterior
  • Posterior
  • Lateral
• Each duct has an ampulla (widened space) where it connects with the utricle.
• Ampulla contains a sensory organ called cristae ampullaris.

Function of Motion Detection

• When endolymph moves, it pushes the gelatinous cupula covering the crista ampullaris.
• This causes hair cells in the crista ampullaris to bend, sending nerve impulses to the brain.

Visualization of Motion

• Spheres will be superimposed in the endolymph to visualize fluid motion.
• Focus on movement within the left vestibular apparatus.

Types of Head Movements

• Axial Rotation: Best exemplified in the lateral semicircular duct. Fluid does not move in sync with the labyrinth due to inertia.
• Flexion and Extension: Anterior duct is most affected.
• Lateral Bending: Affects the posterior duct.

Conclusion

• Endolymph motion is crucial for the body’s sense of movement and balance.