Sensory Systems: The Vestibula r System Dr. Jonathan Spindel CSD and ISAT James Madison University
Welcome message from author
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Transcript
Sensory Systems:
The Vestibular
System
Dr. Jonathan Spindel
CSD and ISATJames Madison University
Why?
Dizziness and balance problems ...
• 7 million patients annually
• #1 complaint of patients over age 70
• #3 complaint of all patients (after headache and lower back pain)
One in three people will have dizziness or balance dysfunction during their life.
(85% of these are due to inner ear involvement)
What is “dizziness?”
• vertigo
• disequilibrium
• lightheadedness
(also … fuzzy-headed,
blurred vision, off-kilter,
stumbly, drunk, not right …)
“the four legged stool”
vestibular
visual
proprioceptive
diffuse CNS
Balance & Motion Management
Balance & Motion Management
vestibular
visual
proprioceptive
auditory
other
CommonCentral
Processing
Individual CentralProcessing
EyeMovements
Posture
Adaptive Controller
The Vestibular System
Head Motion:Angular Acceleration
Head Motion:Linear Acceleration
Head Position:Gravity
SemicircularCanals
Saccule &Utricle
CentralNervous System
Other Inputs
Spinal Cord &Cerebellum:
Posture
Forebrain:Orientation
Oculomotor System:
Eye Movements
The Vestibular System
Head Motion:Angular Acceleration
Head Motion:Linear Acceleration
Head Position:Gravity
SemicircularCanals
Saccule &Utricle
CentralNervous System
Other Inputs
Spinal Cord &Cerebellum:
Posture
Forebrain:Orientation
Oculomotor System:
Eye Movements
The Vestibular Periphery
3 semi-circular canals(sense angular acceleration)
2 otolith organs (maculae);saccule and utricle
(sense linear acceleration)
The Sensory Element: Vestibular Hair Cells
Transducers converting
mechanical energy into
neuro-chemical signals
interpretated by the brain
as motion of the head or
head position
KEY POINT: Continuous activity with directional sensitivity.Excited by bundle deflection towards KC.
Inhibited by bundle deflection away from KC.
Hair Cells in Action
Otolith Organs: Saccule & Utricle
Function:
• Static tilt (gravity)
• Linear acceleration
Otolith Organs: Static Tilt and Linear Acceleration
Semicircular Canals
Function:
• Angular acceleration
• VOR
Semicircular Canals: Structure of the “Crista”
SCC System: Organization
Canals function in paired sets:
right anterior & left posteriorright posterior & left anterior
right horizontal & left horizontal
Motion inducing excitation of one canal induces inhibition of the other.
NOTE: Canals are not orthogonal (at right angles to) normal directions of body/head movement, therefore most regular motions
stimulate multiple canal sets.
The Vestibular System
Head Motion:Angular Acceleration
Head Motion:Linear Acceleration
Head Position:Gravity
SemicircularCanals
Saccule &Utricle
CentralNervous System
Other Inputs
Spinal Cord &Cerebellum:
Posture
Forebrain:Orientation
Oculomotor System:
Eye Movements
The Vestibulo-Ocular Reflex (Excitatory)“Three-Neuron Arc”
Vestibulo-Ocular Reflex (VOR)
Nystagmus
(In general, the objective of most vestibular testing is to look for nystagmus to be there when it should
be, and to not be there when it shouldn’t be.)
Normal vestibular nystagmus is a series of eye motions which reflexively keep center vision focused on the fovea of the eye during head motion.
The Vestibular System
Head Motion:Angular Acceleration
Head Motion:Linear Acceleration
Head Position:Gravity
SemicircularCanals
Saccule &Utricle
CentralNervous System
Other Inputs
Spinal Cord &Cerebellum:
Posture
Forebrain:Orientation
Oculomotor System:
Eye Movements
Brainstem: Vestibular Nucleus
Posterior“Phantom”
Aspect
Vestibular Nuclear Complex
• Lateral VN (LVN)- input from utricle and semicircular canals (maintenance of posture)
• Medial VN (MVN) & Superior VN (SVN)- input primarily from semicircular canals (primary participant in VOR)
• Descending (Inferior) VN (DVN)- input from semicircular canals, utricle and saccule, and vermis of the
cerebellum (integrate vestibular reflexes with other sensory/cerebellar input)
(First site of central sensory interaction integration. Misnomer since only a small number of VNC neurons receive input from vestibular periphery, most receive input from other sensory systems (visual, proprioceptive, auditory, etc.).
The Vestibular System
Head Motion:Angular Acceleration
Head Motion:Linear Acceleration
Head Position:Gravity
SemicircularCanals
Saccule &Utricle
CentralNervous System
Other Inputs
Spinal Cord &Cerebellum:
Posture
Forebrain:Orientation
Oculomotor System:
Eye Movements
Lateral Vestibulo-Spinal Tract
Control of head and neck, upper limb, trunk and lower limb movements in response to motion.
Medial Vestibulo-Spinal Tract
MVST fibers do not extend beyond the
thoracic spinal segments.
Primary participants in movements that control head and upper body response to motion.
Related Documents
