Posture and Balance

Question 1

what is CoM?

Answer 1

point where the
mass of the body is equally distributed

Question 2

what is BoS?

Answer 2

area of the body in
contact with the support surfac

Question 3

what is CoP?

Answer 3

Center of
distribution of force applied to the
supporting surfac

Question 4

what is postural control?

Answer 4

Controlling body position in space
for dual purpose of orientation
and stability

Question 5

what is postural orientation?

Answer 5

Ability to maintain an appropriate
position of the whole body with
respect to the environment and
task

Question 6

what is postural stability?

Answer 6

Ability to control centre of mass
(COM) relative to gravity and base
of support (BOS) during
perturbations or motor tasks

Question 7

what is the definition of balance?

Answer 7

Ability to control the centre of
mass relative to gravity and the
base of support

Question 8

what are the 3 main sources of sensory input to the CNS?

Answer 8

vestibular system - 20%
visual system - 10%
Somatosensory system - 70%

Question 9

what makes up the boney labyrinth?

Answer 9

Auditory: cochlea
vestibular: otolith organs, semicircular canals

Question 10

what part of the inner ear allows us to hear?

Answer 10

cochlea

Question 11

what are the two parts of the otolith organs?

Answer 11

utricule and saccule

Question 12

what is the fluid that fills the membranous labyrinth called?

Answer 12

endolymph

Question 13

what are the sensory receptors within the membranous labyrinth?

Answer 13

hair cells

Question 14

what does each semicircular canal contain?

Answer 14

an ampulla

Question 15

what is contained within each ampulla?

Answer 15

a cupula (gelatinous mass)

Question 16

where would you find the hair cells within the semicircular canals?

Answer 16

within the cupula

Question 17

what will displace the hair cells within the canals?

Answer 17

angular acceleration rotates th egel

Question 18

how are the hair cells depolarized in the semicircular canals?

Answer 18

all hair cells depolarize together

Question 19

what is the purpose of the semicircular canals?

Answer 19

stabilize vision during head turns

Question 20

what are the different semicircular canals?

Answer 20

anterior, posterior, horizontal

Question 21

how are the semicircular canals oriented to each other?

Answer 21

Oriented at 90 degrees to
one another

Question 22

how are the anterior and posterior semicircular canals oriented to midline?

Answer 22

Superior and posterior
canals are 45 degrees
from midline

Question 23

how is there a counter balance design to the semicircular canals?

Answer 23

Each canal works with a partner on the opposite side

Canals activate more strongly in response to movement in a particular plane

Question 24

what happens to firing when we move our head to a particular side?

Answer 24

We increase activity in the semicircular canal on the side we are moving toward and decrease activity the side we are moving away from

Question 25

what movement is the horizontal semicircular canal sensitive to?

Answer 25

Rotation in the transverse plane ie. head turns

Question 26

what movement are the anterior/posterior semicircular canals sensitive to?

Answer 26

Movement in sagittal plane ie. nodding head Movement in the coronal plane ie. side- bending

Question 27

what happens to the frequency of action potentials in relation to acceleration?

Answer 27

Frequency of action potentials increases with higher acceleration

Question 28

how many utricle and saccules are on each side?

Answer 28

One utricle and saccule on each side

Question 29

do the saccules or utricules contain a sensory epithelium?

Answer 29

both

Question 30

what is the sensory epithelium of a utricule and saccule called?

Answer 30

macula

Question 31

what does the macula contain?

Answer 31

hair cells enclosed by a gelatinous mass topped by crystals

Question 32

what is the crystal layer of the sensory epithelium called?

Answer 32

otoconia

Question 33

what are the utricules and saccules sensitive to?

Answer 33

linear movements and static head tilts

Question 34

what is the macular orientation of the urticule like?

Answer 34

more horizontal, meaning it is more responsive to horizontal movement like side bending, lateral displacement

Question 35

what is the macular orientation of the saccule like?

Answer 35

more vertical meaning it is more responsive to vertical movement like up-down, forward/backward movement

Question 36

what is the hair cell orientation in the utricule and saccule?

Answer 36

they are oriented in different directions, so on opposite sides of each macula, hair cells are sensitive to opposite motions

Question 37

why are the vestibular pathways special?

Answer 37

1. They are multisensory (receive visual and vestibular input) * Essential for postural control and control of eye movements 2. Vestibular nuclei provide very fast compensatory eye and head movements

Question 38

what is the function of the medial longitudinal fasciculus (MLF)?

Answer 38

tells the eyes which way they should move via connections with cranial nerves

Question 39

what reflex is the medial longitudinal fasciculus involved with?

Answer 39

vestibular-ocular reflex (VOR)

Question 40

what is an example of the vestibular-ocular reflex (VOR)?

Answer 40

As head turns to right: Right horizontal semicircular canal is active; left horizontal semicircular canal is inhibited Eye musculature responsible for moving eyes to left are activated Eye musculature responsible for moving eyes to the right are inhibited

Question 41

what is the function of the vestibular-ocular reflex (VOR)?

Answer 41

Keep eyes on target while head is moving

Question 42

what is the vestibulospinal tract involved in?

Answer 42

the control of postural orientation and stabilit

Question 43

what tracts does the vestibular nuceli give rise to?

Answer 43

medial and lateral vestibulospinal tracts

Question 44

where does the medial vestibulospinal tract arise from?

Answer 44

medial vestibular nucleus

Question 45

how does the medial vestibulospinal tract descend?

Answer 45

bilaterally in spinal cord

Question 46

what does the medial vestibulospinal tract regulate?

Answer 46

head/neck position

Question 47

what is the vestibular cervical reflex? (VCR)

Answer 47

Moves head in opposite direction of motion

Question 48

where does the lateral vestibulospinal tract arise from?

Answer 48

lateral vestibular nuclei

Question 49

what does the lateral vestibulospinal tract control?

Answer 49

proximal extensor muscle tone for maintenance of posture * Particularly lower limbs

Question 50

what is the vestibular spinal reflex (VSR)?

Answer 50

Body flexes in opposite direction of motion

Question 51

what does the cerebellum provide input to?

Answer 51

medial and lateral vestibular nuclei

Question 52

what does the cerebellum distinguish between?

Answer 52

Motions detected by otoliths and semicircular canals Active vs passive movements

Question 53

where does the vestibular cortical system ascend from?

Answer 53

bilaterally from vestibular nuclei to the ventral posterior nucleus of the Thalamus

Question 54

where does the vestibular cortical system go to

Answer 54

Multiple cortical areas * Parietal cortex and insula

Question 55

what does the vestibular cortical system generate?

Answer 55

a head-in-space picture

Question 56

what system is the vestibular system matched to?

Answer 56

visual system

Question 57

why does physiological vertigo occur?

Answer 57

because there is a conflict between sensory systems

Question 58

why does pathological vertigo occur?

Answer 58

a sudden imbalance of vestibular signals due to a lesion in the vestibular system

Question 59

what is the most common form of vertigo?

Answer 59

Benign Paroxysmal Positional Vertigo (BPPV)

Question 60

what causes Benign Paroxysmal Positional Vertigo (BPPV)?

Answer 60

Displacement of otoconia from the otoliths into the semicircular canal

Question 61

what happens when there is a crystal thats gets into the semicircular canals?

Answer 61

Signals to the brain that movement is occurring despite no movement

Question 62

what canal does a displaced crystal typically wind up in?

Answer 62

90% of the time, the posterior canal

Question 63

what is the name of the maneuver to put the crystal back in place?

Answer 63

Epley maneuver (uses gravity)

Question 64

what is the feedforward mechanism?

Answer 64

anticipatory postural adjustments executed in anticipation of postural instability

Question 65

what is the feedback mechanism?

Answer 65

corrective postural control strategies in response to unexpected postural instability

Question 66

what is static/steady state balance?

Answer 66

our ability to control our center of mass relative to our base of support in predictable and unchanging environments

Question 67

what is anticipatory/proactive balance?

Answer 67

our ability to activate muscles for balance in advance of potentially destabilizing voluntary movements (primarily using feedforward mechanisms)

Question 68

what is reactive balance?

Answer 68

our ability to recover our stability after an unexpected perturbation (using feedback machanisms)

Question 69

when is the ankle strategy activated?

Answer 69

small perturbations on a firm base of support

Question 70

what does the ankle strategy rely heavily on?

Answer 70

somatosensory inputs

Question 71

what muscles are activated first for the ankle strategy?

Answer 71

distal muscles

Question 72

when is the hip strategy activated?

Answer 72

during larger or faster perturbations or when on compliant surfaces or smaller BoS

Question 73

what does the hip strategy rely heavily on?

Answer 73

vestibular and visual inputs

Question 74

what muslces are activated first in the hip strategy?

Answer 74

proximal muscles then distal muscles

Question 75

what are some change in support strategies?

Answer 75

moving the limbs to change the BoS shifting from one strategy to another or using a combination of strategies