physiology guyton

1. Vestibular Apparatus

2. Objectives
• Components of vestibular apparatus
• Mechanism of stimulation of vestibular
apparatus
• Vestibular pathway
• Centers for integration of different sensory
stimuli to maintain balance

3. • Sensory organ for detecting sensations of
equilibrium
• Bony labyrinth*
• membranous labyrinth*
• The membranous labyrinth is the functional
part of the vestibular apparatus.

6. MACULA
• Macula is a small sensory area on the inside
surface of each Utricle and saccule
• 2mm in diameter
• macula of the utricle lies mainly in the
horizontal plane and determines orientation
of the head when the head is upright
• macula of the saccule is located mainly in a
vertical plane and signals head orientation
when the person is lying down.

9. • The calcified statoconia have a specific gravity
two to three times the specific gravity of the
surrounding fluid and tissues.
• The weight of the statoconia bends the cilia in
the direction of gravitational pull.

14. • Under normal resting conditions, the nerve
fibers leading from the hair cells transmit
continuous nerve impulses at a rate of about
100 per second.
• What happens to number of impulses on
movement of cilia toward kinocilium?
Depolarization

15. Functions of Utricle and saccule
• Maintenance of Static Equilibrium
• Detection of Linear Acceleration
• No role in detecting linear velocity for
example during running. Which receptors?
• air pressure acting on pressure end-organs in
the skin

16. Function of semicircular canals
• Detection of Head Rotation
(angular acceleration)
• Predictive Function in the Maintenance of
Equilibrium
• Stabilizing the Eyes (vestibule ocular reflex)

18. Other Factors Concerned with
Equilibrium
• Neck Proprioceptors
• Proprioceptive and Exteroceptive Information
from Other Parts of the Body
• Visual Information

19. Cerebellum, reticular nuclei of the brain stem and spinal cord
Through Reticulospinal and Vestibulospinal tracts*
the vestibular nuclei
Primary pathway for equilibrium begins in
Vestibular apparatus
vestibular nerves(scarpa’s ganglion)

20. • Flocculonodular lobes of the cerebellum are
especially concerned with dynamic
equilibrium signals from the semicircular
ducts.
• The uvula of the cerebellum plays a similar
important role in static equilibrium.
• Medial longitudinal fasciculus cause
corrective movements of the eyes every time
the head rotates
• Signals also pass upward to the cerebral
cortex.