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Block 12 Ellen > L18: posture and balance > Flashcards

L18: posture and balance Flashcards

1
Q

which type of muscles are very active in postural control

A

extensor muscles

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2
Q

what brain structure is the most important for posture maintenance

A

brainstem

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3
Q

3 main sensory systems for balance

A
  1. somatosensory receptors
  2. visual system
  3. vestibular system
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4
Q

4 descending tracts originating in the brainstem for controlling posture

A
  • vestibulospinal tract
  • tectospinal tract
  • potine reticulospinal tract
  • medullary reticulospinal tract
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5
Q

what does ventromedial pathways control

A

axial or proximal trunk muscles

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6
Q

dorsolateral pathways control

A

fine muscle control

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7
Q

where are posture motor neurons innervating axial or proximal muscles located in the spinal cord

A

medially

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8
Q

where are voluntary movements affecting distal musculature located in the spinal cord

A

laterally

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9
Q

3 ventromedial tracts

A
  • tectospinal
  • vestibulospinal
  • pontine reticulospinal
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10
Q

2 dorsolateral tracts

A
  • corticospinal

- rubicospinal

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11
Q

function of vestibulospinal and tectospinal tracts

A

keep head balanced on shoulders as body moves

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12
Q

where does vestibulospinal receive input from

A

vestibular labyrinth in inner ear

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13
Q

where does vestibulospinal orginate from

A

vestibular nuclei in medulla

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14
Q

where does tectospinal receive input from

A
  • retina of eye

- auditory informaiton

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15
Q

where does tectospinal originate from

A

superior colliculus (optic tectum)

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16
Q

what does tectospinal response lead to

A

direction of head and eyes to a particular location in space

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17
Q

where do pontine and medullar reticulospinal tracts originate from

A

reticular formation (controlled by inputs from the cerebellum and cortex)

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18
Q

what does pontine reticulospinal do

A

enhances antigravity reflexes of the spinal cord –> extensors of lower limb to maintain standing

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19
Q

what does medullary reticulospinal do

A

liberates antigravity muscles (opposite to pontine tract)

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20
Q

what happens in humans with extensive cortical damage and why

A

increased extensor tone bc of the brainstem action

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21
Q

where is the vestibular system located

A

inner ear

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22
Q

what is cranial nerve 8

A

vestibulocochlear

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23
Q

what do the otolith organs detect

A

force of gravity and tilts of head (linear acceleration)

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24
Q

what do semicircular canals detect

A

head rotation and angular acceleration

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25
Q

in both the otolith organs and semicircular canals what converts motions into neural signals

A

hair cells

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26
Q

2 parts of the otolith organs

A

utricle and saccule

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27
Q

what is the macula (same in utricle and saccule)

A

matrix of supporting cells and hair cells that are innervated by sensory nerve fibers

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28
Q

what part of the hair cells penetrates into the gelatinous cap

A

cilia

29
Q

what do cilia sense

A

back and forth movement of the cap

30
Q

what are otoliths

A

calcium carbonate crystals that encrust the surface of the gelatinous gap

31
Q

what is the function of otoliths

A

act as weights that are sensitive to gravity and weigh down the cap

32
Q

what happens to the gelatinous cap when head is titled down

A

the cap bends the cilia downwards which can covert the signal to a neural signal

33
Q

2 types of cilia

A
  • kinocilium

- stereocilia

34
Q

what happens when hair cells are bent so that the stereocilia bend towards the kinocilium

A

depolarisation (more cell firing)

35
Q

what happens when you bend the hair cells away from the kinocilium

A

hyperpolarization (less cell firing)

36
Q

difference between utricle and saccule

A

the macula is horizontal in the utricle but vertical in the saccule

37
Q

what does a horizontal macula mean (e.g in utricle)

A

orientation of hair cells towards the striola (midline)

38
Q

what does a vertical macula mean (e.g in saccule)

A

kinocilia away from striola

39
Q

firing pattern of the vestibular nerve

A

tonically (all the time)

40
Q

what type of movement does utricular macula encode

A

horizontal linear motion/ acceleration

41
Q

what type of movement does saccular macula encode

A

vertical linear motion/ acceleration

42
Q

how many semicircular canals

A

3 - anterior, posterior and horizontal

43
Q

what are semicircular canals filled with

A

endolymph

44
Q

what else is filled with endolymph

A

cochlea

45
Q

where in the canal are the main sensory structures located

A

ampulla

46
Q

what sits inside the ampulla

A

cupula

47
Q

what is embedded into the cupula

A

cilia hair cells

48
Q

what can move the cilia hair cells in the cupula

A

endolymph in the ampulla

49
Q

where does the vestibular branch of CN8 send projections to

A

vestibular nuclei in brainstem

50
Q

where does the lateral vestibular nucleus communicate with

A

cerebellum

51
Q

where does the medial vestibular nucleus communicate with

A

extraocular muscles

52
Q

what is the vestibular ocular reflex (VOR)

A

compensatory movement of the eyes in the opposite direction of head rotation

53
Q

function of VOR

A

maintains stable vision during head movements

54
Q

if head moves the the left what semicircular canal is activated

A

left horizontal

55
Q

when head moves to the left what CN and muscles does the left semicircular canal trigger (eye turns to right)

A
  • right abducens flexes right lateral rectus

- left oculomotor nerve flexes left medial rectus

56
Q

does VOR work in the dark

A

yes

57
Q

what is caloric testing for

A

brainstem function

58
Q

in normal caloric testing what happens

A

ear irrigated with water means eye moves towards that ear

59
Q

in a brain stem lesion what happens with caloric testing

A

no VOR present (no eye movement)

60
Q

what does activation of the medial vestibular nucleus do

A

sends signals to cervical spinal cord –> regulates head position by reflex

61
Q

what does activation of the lateral vestibular nucleus do

A

activates proximal muscles to regulate trunk and limbs

62
Q

what happens in the positive supporting reaction

A

placing a limb on the ground will initiate a set of reflexes to stiffen the limb (extensor leg muscles)

63
Q

Meniere’s syndrome=

A

increase in volume of endolymph disrupting membranous labryrinth

64
Q

symptoms of meniere’s syndrome

A

temporary attacks of vertigo, deafness and tinnitus

65
Q

what does prochlorperazine do

A

relieves severe vomiting/ nausea

66
Q

what causes benighn paroxysmal positional vertigo (BPPV)

A

calcium carbonate crystals dislodged from otolith organs disrupting flow of endolymph in semicircular canals

67
Q

symptoms of BPPV

A

suddenly feeling dizzy on moving head in one direction, nausea and vomiting

68
Q

what is migraine associated vertigo

A

attack of vertigo that may be accompanied by migraine symptoms

69
Q

in VOR what tract can be damaged to cause 1 eye dysfuction

A

medial longitudinal fasiculus

Block 12 Ellen (25 decks)

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