Vestibular System

what is the vestibular system

• provides balance

• position and motion of head in space

• rotational and linear

where is the vestibular system located

the inner ear

where is the horizontal plane

horizontally to youw

where is the anterior plane

in front of you

where is the posterior plane

back of the body

what are the main organs of the vestibular system

• copula

  • gelatinous solution hair cells lay in

  • like the basilar membrane of the auditory system

• otolith organs

  • utricle

  • saccule

• semicircular canals

  • horizontal

  • anterior

  • posterior

• hair cells

what happens when damage is done to the vestibular system

• dizziness

• nausea

• loss of balance

  • room is spinning

what are the two otolith organs

• utricle

  • saccule

what are the three semicircular canals

• horizontal

• anterior

  • posterior

what plane is the horizontal semicircular canal associated with, what motion is associated with this

• around the neck

  • doing a pirouette

what plane is the posterior semicircular canal associated with, what motion is associated with this

• frontal plane

• cartwheeling

• post - behind you - divides your front and back half

what plane is the anterior plane associated with

• nodding

• sagittal plane - slices through the middle of your head through your nose

• aunts are saggy

what part of your body does the sagittal plane split - what semicircular canal is that associated with

right through your head through your nose - hit it when nodding - anterior canal

what part of the body does the frontal plane split - what semicircular canal is this related to

right through the middle of you through your ears - when cartwheeling - posterior

why do we have three semicircular canals

there are three axes our head can go in

where is the endolymph fluid located in the vestibular system

in the semicircular canals

where is the copula located in the vestibular system

in the circular spot surrounded by endolymph fluid in the semicircular canals

how do we detect rotation

we move our head and the actual canal moves, but the endolymph fluid inside of it does not move. the endolymph fluid will push against the cupula in the opposite direction of the rotational movement. the cupula gel will push against hair cells causing them to move, again in the opposite direction of the rotational movement. this causes hair cells to move and create action potentials

which way do hair cells move proportional to the rotation of movement? why?

opposite. due to the inertial properties of endolymph fluid

does endolymph fluid push against the cupula? what does this cause or prevent?

endolymph fluid pushes against the cupula which moves hair cells causing action potentials

what are the saccule and utricle

the two otolith organs

what do the saccule and utricle do

signal movement on the vertical and horizontal axes

which axes does the saccule work on? what does this give information on

the vertical axis, gives information on gravity

what axes does the utricle work on? what does this give information on

horizontal, gives information on linear movement

what is the structure of the otolith organs

they have hair cells embedded in a gelatinous form. this gelatinous form has otoconia which are calcium carbonate crystals

what are otoconia

calcium carbonate crystals in the otolith organs

how do the otolith organs signal information

when we move hair cells move with us but the gelatinous gel hair cells are in lags behind due to its mass from otoconia, this deforms hair cells and causes action potentials

which otolith organ is always delivering information? why? what ability does this give us?

• saccule

• always deformed due to gravity

• we can tell which way is up or down

what is benign positional vertigo, what causes it

sudden onset of dizziness and nausea, caused by head trauma

what is happening in the vestibular system to cause sudden benign vertigo

otoconia in the otolith organs have broken off, because all of the fluid in the brain is connected it had made its way into the endolymph fluid in the canals. this changes the density of the canals such that when we turn our head it moves differently (with greater acceleration because mass and acceleration are related) and will move hair cells more greatly to signal to our brain that we are moving faster than we are. this confuses our brain and indicates that something is wrong. to make us stop moving our brain make us nauseous (protective mechanism).

how do we cure sudden benign vertigo

find which direction of movement causes vertigo symtpoms (usually only one) and from that determine which canal is affected. hang the person upside down to dislodge the crystal thats in the wrong spotwhat

what are kinocilia

a special cilia on hair cells which indicate direction, each hair cell only has one

do semicircular canals work alone

no

which semicircular canals work together

the ones on either side of your head

how do semicircular canals work together? what effect does this have?

one semicicular canal on one side of your head will send an excitatory signal to the vestibular nerve to increase firing rate and the other will send an inhibitory signal to decrease vestibular neuron firing rate. this allows us to detect which direction our head is turning

how does transduction of rotational movement happen?

• rotate the head

• canal moves

• endolymph fluid inside does not

  • inertial properties

• endolymph fluid pushes on cupula

• cupula bends hair cells

• hair cells bend towards kinocilium

• K+ channels open

• hair cell depolarizes

• Ca2+ flows in

• releases neurotransmitters

• causes action potential

what can give you the sense that you’re moving when you’re not? what is an example of this

strong visual inputs

like when youre sitting on a train and the train next to you starts moving and you think its you, it confuses your brain

what two major systems/structures do the vestibular system feed into

• central

• cerebellum

what does the dorsal route entry zone do

helps with sensory integration

what does arousal mean in brain physiology

state of alertness

what are the sensors of the peripheral nervous system

otolith organs (saccule and utricle) and the semicircular canals (horizontal, anterior, posterior)

what are the other two components of the peripheral vestibular system

• vestibular nerve

• dorsal root entry zone

what does the peripheral vestibular system feed into

the peripheral vestibular system feeds directly into the cerebellum as well as the central nervous system

do the cerebellum and the central nervous system feed into each other when recieveing input from the peripheral vestibular system

yes

what does the central nervous system feed into after receiving inputs from the peripheral vestibular system

• the oculomotor nuclei

• the vestibulospinal system

• autonomic nervous system

• reticular formation

what does the oculomotor nuclei do with information given (peripheral vestibular system to CNS)

controls eye movement

what does the vestibulospinal tract do with information from the vestibular system (peripheral vestibular system to CNS)

• control posture

• vestibulospinal reflex - ensures you dont fall over

what does the autonomic nervous system do with infomration from the vestibular system ((peripheral vestibular system to CNS))

• modulates our vomiting centre

what does the reticular formation centre do with information from the vestibular system (peripheral vestibular system to CNS)

the reticular formation helps with arousal (alertness)

what are the three main functions of the vestibular system

• vestibular ocular reflex

• vestibular postural reflex

• sense of spatial orientation

what does the vestibular postural reflex do

• from the vestibulospinal system

• ensures you don’t fall over

• recovery after a fall

• how cats land on there feet

what does the vestibular ocular reflex do

the vestibular ocular reflex (from the oculomotor nuclei) ensures our pupils can compensate for involuntary movement and focus on objects

what is the consequence of damage to your vestibular ocular reflex

cant recognize faces or read signs when walking, cant read a book (involuntary movement from your heartbeat and breathing)

what is a proprioreceptors

a specialized receptor that detects changes in muscle movement and length

what are the three systems which contribute to balance

• leg proprioception (including muscle stretch reflexes)

• ocular movement (optokinetic system)

• vestibular system

how do we know leg proprioreceptors (including stretch reflex) contributes to balance

if you hit a blindfolded persons achilles tendon they will think there muscles are more stretched than they are and that they are leaning forward. they will compensate for this by leaning backwards and will fall over if not supported.

how does our occular system contribute to balance

the optokinetic system takes in inputs of how we are moving through space

how many eye nerves do we have - what are they for

6 total; two for each of up and down, left and right, and torsion

what is the wiring of our eye connected to in the vestibular system

the semicircular canals

what is Nystagmus

uncontrolled eye movement

what are the three types of eye movement

• saccade

• smooth pursuit

• vergence

what is the most common kind of eye movement

saccade

what is a saccade

an eye movement. rapid jumping of the eye in space. if we didnt have this you would just be moving around all the time. you go blind for a second

what is a smooth pursuit

an eye movement. following an object in the distance

what is a vergence

an eye movement. something coming closer to you. you go cross eyed

what would happen to your eye movement when you were moving at a constant velocity with your eyes closed

nothing would happen. you are moving with constant velocity so the endolymph fluid does not experience any net movement and no signals are being fired

what would happen if you started to be rotated to the left with your eyes closed

your canal would shift to the left with you and the endolymph fluid inside would shift right triggering a right vestibular eye movement and your eyes would shift right. then a saccade would occur to shift your eyes back to centre. this process would repear