s+p : vestibular senses

vestibular system

the set of 5 organs — 3 semicircular canals and 2 otolith organs — located in each inner ear that sense head motion and head orientation with respect to gravity

spatial orientation

a sense comprised of our 3 sense modalities of linear motion, angular motion, and tilt

angular motion

can be sensed when rotating head from side to side as if to say “no”

linear motion

sensed when accelerating or decelerating in a car

tilt

can be sensed when nodding head up and down as if to say “yes”

semicircular canals

3 toroidal tubes in the vestibular system that sense angular motion

work by having fluid that moves relative to the walls of the canals —> fluid bends cilia on hair cells —> causing a neural signal

otolith organs

mechanical structures in the vestibular system that sense both linear acceleration and gravity

tiny crystals called otoconia resting on cilia from hair cells —> inertia/gravity causes otoconia to push down on cilia —→ causes neural signal

depolarization

bending toward tallest stereocillia

hyperpolarization

bending away from tallest stereocillia

perilymph

fluids that fill semicircular canals

endolymph

fluid filled by membrane formed in second, smaller toroid

ampulla

cross section of each canal swells substantially near where the canals join the vestibule

cristae

specialized detectors of angular motion located in each semicircular canal in a swelling called ampulla

otolith organs

sense acceleration and tilt

2 types of otolith organs

utricle and saccule

macula

specialized detector of linear acceleration and gravity

otoconia

hair cells encased in gelatinous structure that contains calcium carbonate crystals

vestibulo-ocular reflexes (VORs)

counter-rotating the eyes to counteract head movements and maintain fixation on a target

angular VORs

when the head turns to the left, the eyeballs are rotated to the right to partially counteract this motion

torsional eye movements

when ehad is rolled about the x-axis, eyeballs can be rotated a few degrees in the opposite direction to compensate

autonomic nervous system

part of the nervous system innervating glands, heart, digestive system, and responsible for regulation of many involuntary actions

motion sickness

results when there’s a disagreement between the motion and orientation signals provided by semicircular canals, otolith organs, and vision

vestibulo-spinal responses

reflexes that help keep us from falling over, w/o these, we’d be unable to stand up in the dark