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Neuroscience > Lecture 11: Posture and Balance > Flashcards

Lecture 11: Posture and Balance Flashcards

1
Q

what is Centre of mass (CoM)

A

point where the mass of the body is equally distributed

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2
Q

what is Base of support (BoS)

A

area of the body in contact with the support surface

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3
Q

what is Centre of pressure (CoP)

A

Center of distribution of force applied to the supporting surface

Moves continuously around the CoM to keep it within the BoS (hearding dog)

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4
Q

what is postural control

A

umbrella term

Controlling body position for orientation and stability

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5
Q

what is postural orientation

A

ability to maintain an appropriate position

(lean forward when walking up hill)

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6
Q

what is postural stability/balance

A

Ability to control centre of mass (COM) relative to gravity and base of support (BOS)

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7
Q

what is the stability if a person is sitting reading a book

A

large base of support

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8
Q

what is the stability of a person standing to read

A

more demands than sitting because base of support is smaller

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9
Q

what is the stability of a person walking and looking forward

A

centre of mass does not stay within base of support, so there is a continuous state of imbalance

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10
Q

do postural control requirements change wit the task and environment

A

yes

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11
Q

3 main sources of sensory input to the CNS

A

somatosensory (70%)

vestibular system (20%)

Vision (10%)

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12
Q

when learning a new skill, do we rely more on somatosensory input or vision for postural stability

A

vision

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13
Q

what are the 2 parts of Vestibular Apparatus

A

bony labyrinth

membranous labyrinth

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14
Q

what is the membranous labyrinth

A

Suspended within bony labyrinth

Filled with fluid (endolymph)

Sensory receptors (hair cells) that tell us where our head has moved

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15
Q

what are the Semicircular Canals

A

3 perpendicular bones in each ear

has cupula (gelatinous mass) with hair bundles inside

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16
Q

what displaces hair cells in ear

A

Angular acceleration which
depolarizes all hair cells together

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17
Q

what is the purpose of the semicircular canals

A

stabilize vision during head turns

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18
Q

what are the names of the 3 Semicircular Canals and how are they positioned

A

anterior(superior), posterior, and horizontal canals

Oriented at 90 degrees to one another

anterior and posterior canals are 45 degrees from midline

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19
Q

what is the counter balanced design

A

Each canal works with a partner on the opposite side

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

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

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20
Q

what movement are the horizontal canals sensitive to

A

Rotation in the transverse plane (head turns)

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21
Q

what 2 movements are the Superior/anterior and posterior canals sensitive to

A

Movement in sagittal plane (nodding)

Movement in the coronal plane (side-bending)

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22
Q

in general, the direction of head movement corresponds to what in canals

A

an increase in the activity of that canal

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23
Q

how are semicircular canals sensitive to angular acceleration

A

Frequency of action potentials increases with higher acceleration

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24
Q

what are the 2 types of otolith organs

A

Saccule and Utricle

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25
what are otolith organs
One utricle and saccule on each side that mirror the other side Each contain a sensory epithelium (macula) topped by crystals (otoconia)
26
what type of movement are otolith organs sensitive to
linear movements and static head tilts
27
what is the orientation of the utricle and what is it responsive to
more horizontal responsive to horizontal movement (side bending, lateral displacement)
28
what is the orientation of the Saccule and what is it responsive to
more vertical responsive to vertical movement (up/down, forward/backward)
29
how are hair cells in otoliths orientated and what movement are they sensitive to
Hair cells oriented in different directions On opposite sides of each macula, hair cells are sensitive to opposite motions (half depolarizes)
30
are otoliths sensitive to acceleration?
no. they have Tonic or sustained pattern of activation
31
what 2 things are special about vestibular inputs
They are multisensory (receive visual and vestibular input) vestibular nuclei provide very fast compensatory eye and head movements
32
why is it important that the vestibular pathways are multi sensory
* Essential for postural control and control of eye movements
33
what is the Medial longitudina lfasciculus (MLF)
connection between vestibular and visual systems tells the eyes which way they should move Involved in the vestibular- ocular reflex (VOR)
34
what is the vestibular- ocular reflex (VOR)
as head turns to the right while looking at something, 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
35
what is the function of the Involved in the vestibular- ocular reflex (VOR)
Keep eyes on target while head is moving
36
what are Vestibulospinal Tracts
Involved in the control of postural orientation and stability Vestibular nuclei give rise to the lateral and medial vestibulospinal tracts
37
what is the Medial Vestibulospinal Tract
Arises from medial vestibular nucleus Descends bilaterally in spinal cord Regulates head/neck position
38
which reflex is the medial vestibulospinal tract involved with
Vestibular cervical reflex Moves head in opposite direction of motion when falling forward, neck extends to protect neck
39
what is the Lateral Vestibulospinal Tract
Arises from lateral vestibular nuclei Controls proximal extensor muscle tone for maintenance of posture in legs
40
what reflex is involved with the Lateral Vestibulospinal Tract
Vestibular spinal reflex (VSR) Body flexes in opposite direction of motion if our body is pushed to the right, we lean to the left to come upright
41
what does the cerebellum do
Cerebellum provides input to medial and lateral vestibular nuclei
42
what 2 things does the cerebellum distinguish between
Motions detected by otoliths and semicircular canals Active vs passive movements
43
what is the Vestibular Cortical System
vestibular information ascends bilaterally to the thalamus, then to the parietal cortex and insula generates a head-in-space picture
44
are vestibular and visual systems are matched to one another
yes
45
what is Physiological vertigo
conflict between sensory systems (motion sickness)
46
what is pathological vertigo
caused by a sudden imbalance of vestibular signals
47
what is Spontaneous Nystagmus
movement of the eyes without stimulus.
48
what is Benign Paroxysmal Positional Vertigo (BPPV)
Most common cause of vertigo Displacement of otoconia from the otoliths into the posterior semicircular canal Signals to the brain that movement is occurring despite no movement
49
what is the Epley Maneuver
Treatment of posterior canal BPPV Displaces the otoconia back into the otoliths using gravity
50
what is the feedforward mechanism
anticipatory postural adjustments in anticipation of postural instability
51
what is the feedback mechanism
corrective postural control strategies in response to unanticipated postural instability
52
what are the 3 types of balance control
Static/Steady State balance Anticipatory/Proactive balance Reactive balance
53
what is Static/Steady State balance
Ability to control the COM relative to the BOS in predictable and unchanging conditions (standing on leg, keeping self balanced)
54
what is Anticipatory/Proactive balance
Ability to activate muscles for balance in advance of potentially destabilizing voluntary movements (ie. picking up a box) * Using feedforward mechanisms
55
what is Reactive balance
Ability to recover a stable position following an unexpected perturbation * Using feedback mechanisms (bus hits the breaks and we need to rebalance)
56
why is Static and dynamic balance really a continuum
when we are "static" we still sway so we are still moving
57
what are the 2 postural stability functions
anticipatory (minimize upcoming issues - feedforward) reactive (correct errors - feedback)
58
what is Anticipatory Postural Adjustment
Activation of postural muscles before execution of voluntary goal
59
why is Reticulospinal Tract important for postural control
Bilateral terminations Postural control to support skilled/coordinated movements Muscle tone
60
what is ankle strategy
Activated during small perturbations and firm surfaces Rely heavily on somatosensory input Distal muscles activated first
61
what is the hip strategy
(standing on balance beam) Activated during larger or faster perturbations Rely more on vestibular and visual inputs Proximal muscles activated first
62
what is change in support strategies
Moving the limbs to change the BOS Humans can adapt by shifting from one strategy to another reaching or stepping
63
what does abnormal postural control look like
Increased sway slower anticipatory control Increased reliance on hip and stepping strategies
64
how does cognition contribute to abnormal postural control in people with strokes
Reaction times increase with increasing postural control demands

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