Chapter 16 Part 1 Flashcards
Otolithic organs
Anatomic site of sensory receptors that respond to head position relative to gravity and to linear acceleration and deceleration of the head.
Vestibular apparatus
Part of the inner ear that detects position and movement of the head; it consists of the semicircular canals, saccule, and utricle.
Semicircular canals
Three hollow rings in the inner ear that are oriented at right angles to each other. Each canal contains the receptor mechanism for detecting rotational acceleration or deceleration of the head.
Vestibular nuclei
Site of synapse between the first- and second-order neurons that convey information about head position and head movement.
Vestibular ocular reflex (VOR)
Involuntary movements of the eyes that stabilize visual images during head and body movements;
Semicircular canals:
rotational movement of the head
Crista:
Is a body of supporting cells and sensory hair cells
Three pairs of semicircular canals:
(1) Left with right horizontal canals
(2) Left anterior with right posterior
(3) Left posterior with the right anterior
Utricle and saccule:
respond to head position relative to gravity and to linear acceleration and deceleration
Otoconia:
calcium carbonite crystals that are more dense than the surrounding fluid and gelatinous support
Conjugate
both eyes move in the same direction
Vergence
eyes move toward the midline or away from the midline (convergence vs. divergence)
Gaze stabilization
Keeping the position of the eyes stable during head movements to ensure that the environment does not appear to bounce
Direction of gaze
Directing the gaze at visual targets
Saccades
fast eye movements to switch gaze from one object to another
Smooth pursuits
eye movements that follow a moving object
Vergence movements
movement of the eyes toward or away from midline to adjust for different distances between the eyes and the visual target
Utricular macula-horizontal
Responds maximally to head tilts that begin with the head in the upright position, as in bending forward to pick something off the floor
Respond to linear acceleration and deceleration
Saccular macula- vertical
Responds maximally when the head moves from a laterally flexed position, as in moving from side lying to standing
Semicircular canals are used to:
stabilize vision
What is once major function of the vestibular nuclei?
coordinate movements of the eyes and head to allow for stable visual fixation during head movement.
What are the two roles the vestibular system has in motor control?
gaze stabilization
postural adjustments
Tracts for postural adjustments:
Lateral Vestibulospinal Tract: LMN to limbs and trunk
Medial Vestibulospinal Tract: adjust head
Nasal retina
info crosses the midline in the optic chiasm and projects to the contralateral visual cortex
Temporal retina
info continues ipsilaterally through the optic chiasm and projects to the ipsilateral cortex
Primary visual cortex:
stimulates neurons that discriminate the shape, size, or texture of objects.
Action Stream:
Is a stream of visual information that flows dorsally and used to direct movement
Perception stream:
Is a stream of visual information that flows ventrally and used to recognize visual objects
