Vestibular System Flashcards
The vestibular system constitutes an ______ sensor ie; _____
inertial sensor, i.e., it encodes the motion of the head relative to the outside world
Our equilibrium sense is composed of _______ and ________ that begin with the vestibular organs in the inner ear
multiple reflexes and multiple perceptual modalities
What are 4 examples of movements involved with the vestibular system?
Visual stability Balance Autonomic Processes Spatial Orientation
Know this diagram.
What happens when the kinocilium bend toward the tallest portion?
Increased impulse frequency = depolarization, which leads to excitation
What happens when the kinocilium bend toward the smallest portion?
Decreased impulse frequency = hyperpolarization = inhibition
Explain this image from text
Ampulla of semicircular canal
A: Thick zone epithelium (ampulla crista), contain hair cells. The hair bundles of the cell extend into the gelatinous diaphragm, the cupul, which stretches from the crista to the root of the ampulla
B: Angular acceleration: Cupla is displaced by the flow of the endolymph when the head moves. As a result, hair bundles also displaced
Explain this image from text
The left and right semicircular canals work together to signal head movement
Because of inertia, rotation of head counterclockwise causes endolymph to move clockwise with respect to the canals. On the left side, stereocilia move in the excitatory direction = exciting afferent fibers on this side. On right side afferent fibers are hyperpolarized so that firing decreases
Explain this image from text
Same as the previous one just illustrated in a different way
Left anterior and right posterior canals (LARP): rotation in the vertical plane skewed 45° anteriorly to the left.
Right anterior and left posterior canals (RALP): rotation in the vertical plane skewed 45° anteriorly to the right.
The two otolith organs, the ______ and ______, detect linear motion as well as the static orientation of the head relative to gravity, which is itself a linear acceleration.
utricle and saccule
Explain this image from text
The utricle is organized to detect the tilt of the head
The hair bundles are polarized but are orientated in different directions. Therefore, when the head is tilted, the gravitational force on the otoconia bends each hair bundle in a particular direction.
When the head is tilted in the direction of the hair cells axis of polarity = depolarizes = excitation of afferent fiber. When the head is tilted in the opposite direction of the hair cells axis of polarity = hyperpolarizes = inhibition of afferent fiber.
Explain these images from text
Vestibular inputs signaling body posture and motion can be ambiguous (more open to interpretation)
The postural system can’t determine to distinguish between tilt and linear acceleration based on otolithic inputs alone
Very low frequency, the semi-circular canals well not be activated, which is why there is no difference early on between tilt and translation
Explain this image from text
The horizontal vestibulo-ocular reflex
A: Head turns left, excites hair in the left horizontal canal = exciting neurons that evoke right eye movement. Two populations of first-order neurons one in the medial vestibular nucleus (M) which axon crosses midline to excite neurons in the right abducens and prepositions hypoglossal.
Other in the lateral vestibular nucleus travels ipsilaterally on track of dieters to excite oculomotor nucleus to the left medial rectus muscle
Two sets of n neurons in right abducens nucleus; motor neurons into abducens nerve to right LATERAL rectus, interneurons ascend uo left medial longitudinal fasciculus (LMLF) to oculomotor nerve to left medial rectus.
B: afferent fibers excite neurons in medial vestibular nucleus causes inhibition of motor and interneurons in left abducens nucleus = reduces excitation in left LATERAL rectus and right medial rectus
_______ allows you to maintain gaze when the head is moving
VOR (vestibulo-ocular reflex)
Know the target muscle for each canal
Look at this image, see how it relates to Gu et al 2018, slide 11
Explain this diagram in the text (A)
The vestibulo occulor reflex is adaptable
A: Monkey wears spectacles for several days the double the speed of retinal imaging. With spectacles in increases, then returns to normal when off. Therefore trying to make the gain = to 1 so it lands on the fovea. If eye and head move at the same frequency, the gain is at 1, and therefore the target is on the fovea.
Explain this image from text (B)
Vesitibulo-occular system is adaptable
B: Adaptation occurs in the cerebral and brainstem circuits. Visual error –> inferior olivary nucleus. Climbing fiber transmits error signal to the Purkinje cell. Purkinje cells transmits changed information to a floccular target cell in the vestibular nucleus, changing its sensitivity to the vestibular input.
Explain this image from text
And what is efference copy for?
Reafference is sensory feedback due to self-generated motion
Exafference si sensory signals generated from external stimuli in the environment
Efference copy is a copy of a signal produced and sent to the motor system, and is created so that exafference (sensory signals generated from external stimuli in the environment) can be distinguished from reafference
Explain this image from text
neither neck motor efference copy nor proprioception cues alone are sufficient to account for the elimination of neuronal sensitivity to active head rotation
Does vestibular neuron nucleus only encode exaffernce?
Explain this image from text
Cancellation signal is generated only when the activation of neck proprioceptors matches the motor-generated expectation: an internal model of the sensory consequences of active head motion is used to selectively suppress reafference at the vestibular nuclei level.
Explain this image from text
A reference frame can be defined as the particular perspective from which an observation of a spatial variable is made
True or False: Vestibular neurons that receive this visual input can distinguish between visual and vestibular signals
False, can not
Can explain while people may feel moving when the scene is actually moving.
Explain this image
MSTd involved in motion processing, signals from MT would be processed in neurons from MStd
Neurons are modulated based on eye position in this area
Eye and head position gain fields were strongest in MSTd and weakest in PIVC. Our findings reveal distinct spatial reference frames for representing vestibular signals and pose new challenges for understanding the respective roles of these areas in potentially diverse vestibular functions.
