Lecture 18 - Vestibular influences on occulomotor control and posture Flashcards
Where does the output of the vestibular labyrinths project to?
The vestibular nuclei
What is the role for vestibulo-ocular reflexes?
To keep images on the eyes still when the head moves
What is the role for the vestibulospinal relfexes?
To enable the skeletomotor system to compensate for head movements
What signals how fast the head is rotating?
The vestibular apparatus
The occulomotor system uses information from the vestibular apparatus to do what?
Stabilise the eyes to keep images in the retina
What are the three different types of VOR? [3]
- Rotational vestibular-ocular reflex
- Translational vestibular-ocular reflex
- Ocular counter-rolling response
What does Rotational vestibular-ocular reflexes compensate for?
- Head rotation
- Recieves inputs from the semicircular canals
What does the Translational vestibular-ocular reflex compensate for?
Linear head movements
What does the Ocular counter-rolling response compensate for?
Head tilt in the vertical plane
How does the rotational vestibular-ocular reflex control the eyes?
They cause them to slowly rotate in the opposite direction to any rotational head movement
The coordination of head and eye movements to direct the fovea is called?
Gaze
What do small gaze movements cause?
Saccades
What happens when gaze movements are larger?
- Head and eyes move simultaneously
- VOR is supressed
What are two problems with the VOR?
- It habituates
- The canals do not response well to very slow head movements
How can the problems with the VOR be componsated for?
The optokinetic system provides the central vestibular system with visual information
What properties are shared between the VOR and the optokinetic reflex?
- Builds up slowly
- Responds to very slow visual image motion
What is circular vection?
When the whole scene is moving it messes up the vestibular stabilisation
What does vestibular stabilsation do?
Allows one to tell which items are moving and which are stationary
Vestibular nuceli respond identically to what?
- Head mvoements
- Movement of an image on the retina
How do we know we are falling?
- Visual
- The head moves
What is the major factor in the maintainance of posture?
Signals from the vestibular nuceli to the spinal cord
What are the four different vestibular nuclei? [4]
- Medial
- Lateral
- Superior
- Descending
Where does the superior and medial nuclei recieve inputs from?
The semicircular canals
Where do the superior and medial nuclei send outputs to?
- Occulomotor centres
- Spinal cord
