Vestibular Flashcards
where are the cells bodies of the vestibular system located
in the scarpa ganglion
what is the vestibular system responsible for
balance, reflexive movements, head position, self motion, spatial orientation
two main components of the vestibular labyrinth
membranous labyrinth (sacs filled with endolymph) bony labyrinth (sacs filled with perilymph)
the vestibular system is joined to which auditory structure
the cochlea (has the same fluids)
what are the three types of movement in 3D space
translational (back n forth/ sideways)
static head tilts
rotational
what detects static head tilts
primarily by the otolith organs
what is rotational movement detected by
the semi circular canals
where are the vestibular hair cells located (2)
in the utricle & saccule and the ampullae of the semi circular canals
where/ what are the ampullae
enlargements at the base of each semi circular canal where hair cells are located
what is the macula
a sensory epithelium i. the otolith organs that consists of supporting cells and hair cells
what is the otolith membrane
a gel layer with calcium carbonate crystals (otoconia)
what makes the otolith membrane heavy?
otoconia (calcium carbonate crystals)
how are static head tilts detected
static head tilt cause the heavy otolith membrane to slide causing movements in the stereocilia of the hair cells depending on the direction you tilt your head
describe the orientation of stereocilia in the otolith organs
smallest to largest towards the striola
which plane does the utricle detect movement in
translational movements of the head in the horizontal plane
which plane of movement does the saccule detect movement in
translational movements of the head in the vertical plane
what is the sensory epithelium called in the semi circular canals
the crista
what structure makes the barrier to endolymph in the semi circular canals
gel like structure called the cupula
how is rotation of the head detected in the semi circular canals
rotation causes the endolymph to move in the opposite direction displacing the cupula position. leading to movement of the stereocilia of the hair cells causing hyperpolarisation or depolarisation
how are the stereocilia orientated in the semi circular canals
the pair of corresponding hair cells are orientated oppositely in each ear
when sensing angular accelerations in the head why does the discharge rate plateau in the middle
the fluid pushes back against the gel like cupula as it returns to its original shape
what inputs does the vestibular nuclei integrate
sensory cues from vision, cutaneous (touch), and muscle spindles (proprioception)
describe four outputs of the vestibular nuclei
- to spinal cord and motor neurones of limb and torso (balance & posture)
- to motor neurones of external eye muscles (stabilising gaze)
- to thalamus then vestibular cortex (perception of motion)
- cross talk to cerebellum (motor coordination)
what is the vestibulo-ocular reflex
a reflex that control movement of the eye sockets when the head moves (moves eye in opposite direction to the head stabilising gaze)
what structure controls the vestibular-cervical reflex and what is it
medial vestibular nucleus - signals from semi circular canals control neck muscles and head position vis this pathway
what structures control the vestibular spinal reflex and what is it
lateral and medial vestibular nuclei - signals from the otoliths travel to the nuclei where nerve cell carry signals via the vestibulospinal tract to the spinal cord to stabilise posture
describe the vestibular ascending pathways
through the lateral and superior vestibular nuclei to the thalamus then to the vestibular cortex
