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Year 2 > Posture And Balance > Flashcards

Posture And Balance Flashcards

1
Q

What is posture?

A

Relative position of the body parts to each other, the environment and gravity, automatically maintained by extensor muscles.

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2
Q

What is postural equilibrium?

A

State where all forces acting on the body are equal.

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3
Q

What is static posture?

A

Postural equilibrium when the body is still.

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4
Q

What is dynamic posture?

A

Postural equilibrium when the body is moving.

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5
Q

What are the inputs to the postural system?

A

Somatosensory receptors from the muscle and propioreceptors
Visual system
Vestibular system

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6
Q

What is the centre of the postural system?

A

Brainstem

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7
Q

What is the output for the postural system?

A

Motor neurons to act on extensor muscles to increase tone.

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8
Q

What is the ventromedial pathways?

A

Descending pathways originating in the brainstem and have tracts that act on the spinal cord for involuntary control of posture and balance.

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9
Q

What is the tectospinal tract?

A

Arises from the superior and inferior follicular to act on the head and neck muscles to orientate these muscles towards visual stimuli to maintain balance.

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10
Q

What is the recticulospinal tract?

A

Arises from the reticular formation to responsible for posture and locomotion. Reticulospinal tract receives input from the cerebellum to co-ordinate movement.

It is divided into a pontine and medullary tract, depending on the region of the brainstem.

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11
Q

What is the vestibulospinal tract?

A

Originates from the vestibular nuclei of medulla to increase the tone of the ipsilateral extensor muscles to maintain balance. It receives input from the cerebellum and inner ear vestibular labyrinth.
Divided into a medial and lateral tract depending on the spinal cord segment that they exit.

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12
Q

What is the role of the medial vestibulospinal tract?

A

Exits from the cervical segment of the spinal cord to act on the head and neck ipsilateral extensor muscles for posture and balance.

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13
Q

What is the role of the lateral vestibulospinal tract?

A

Exits from the thoracic segment of the spinal cord to act on the axial and appendicular ipsilateral extensor muscles for balance and posture.

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14
Q

What is the role of the pontine reticulospinal tract?

A

Arises from the reticular formation of the pons to control the extensor muscles for locomotion and posture.

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15
Q

What is the role of the medullary reticulospinal tract?

A

Arises from the reticular formation of the medulla to control the flexor muscles for locomotion and posture.

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16
Q

How are the lower motor neurons arranged in the spinal cord?

A

Somatotropin fashion where the neurons controlling the proximal muscles are more medial and distal muscles are more lateral.

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17
Q

What is decerebrate rigidity?

A

Loss of cerebral (and cerebellar) input to the brainstem means that there is a high resting tone of the extensor muscles, caused by lack of inhibition to the lateral vestibular and pontine reticulospinal tracts.

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18
Q

What is the vestibular system and its components?

A

Sensory system which provides information on the head position, spatial direction and motion. It is located in the labyrinth of the inner ear.

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19
Q

What are the components of the vestibular system?

A

Labyrinth contains semicircular canals, otolithic organs and the cochlea, making up the vestibular system.
Innervated by cranial nerve 8, the vestibulocochlear nerve.

20
Q

What is inertia?

A

An object in motion will stay in motion unless it receives another force; a stationary object will remain stationary unless it receives another force.

21
Q

What are the semicircular canals?

A

They make up the bony labyrinth of the vestibular system, consisting of 3 ducts called anterior, lateral and posterior semicircular canals which converge at the ampulla and contain endolymph fluid.

They respond to rotational movements of the head via stimulation of ciliated hair cells, converted into electrical signals sent to the CNS.

It is named based on its relation to the cochlea.

22
Q

What is the composition of the semicircular canals?

A

The ducts of all 3 semicircular canals contains endolymph rich in k+ and in response to movement, this endolymph travels to the ampulla. The ampulla contains ciliated hair cells in a crista embedded in a gel matrix called the cupula.

23
Q

How are the semicircular canals stimulated?

A

Endolymph enters the ampulla at a slower and opposite direction to movement due to inertia and causes stereocilia of hair cells to bend, generating action potential which travels to the nerve. Half will move away from the endolymph and cause hyperpolarisation, known as capula displacement.

24
Q

What are the otolithic organs?

A

Located in the vestibule, consisting of two membranous sacs called utricle and saccule. These contain patches of hair cells which respond to gravitational movements in linear tilts of the horizontal or vertical direction.

25
Q

What is the composition of the otolithic organs?

A

Otolithic organs contain sensory epithelium with ciliated hair cells lined with calcium carbonate crystals called otoconia as well as supporting cells contained in a gelatinous cap called the cupula. Otoconia bear down on the ciliate in response of gravity.
The hair cells in the otolithic organs uniquely have a mid line called the striola, where kinocilium angle.

26
Q

What is the structure of the hair cells in the vestibular system?

A

Each individual hair cell contains numerous stereocilium and ONE kilocilium. The kiliocilium is angled towards the ampulla.

When endolymph acts on hair cells, it bends half of the stereocilium towards the kinocilium, which triggers depolarisation of the hair cell to stimulate the auditory nerve. Half of the stereocilium remains bent away from the kinocilium.

27
Q

What happens when sound is not being produced?

A

Endolymph does not flow towards ampulla, so stereocilium are no longer being tilted towards kiliocilium and this results in hyperpolarisationa dn decrease in afferent impulses.

28
Q

What is the role of the anterior/superior semicircular canal?

A

Responds to tilting head up and down.

29
Q

What is the roe of the posterior semicircular canal?

A

Depolarises in response to tilting the head left and right towards the shoulder.

30
Q

How can the semicircular canals output be inhibited?

A

Rotating head in the opposite direction.

31
Q

What is the role of the lateral semicircular canal?

A

Depolarises in response to the head rotating from side to side.

32
Q

What is the utricle?

A

It is the larger membranous sac of the otolithic organs which is horizontally orientated. Utricle containing a macule of sensory epithelium ciliated hair cells with otoconia.

The kinocilium is orientated towards the striola, and due to horizontal movement forwards and backwards, it causes the kinocilium to bend away from striola and results in depolarisation.

33
Q

What is the saccule?

A

Smaller membranous sac of the otolithic organs containing epithelia which is vertically orientated. It responds to vertical UP and DOWN movements. The kinocilium is bent away from the striola so when vertical movements occur, it moves the kinocilium towards the striola and causes depolarisation of the hair cell to transmit information to the auditory nerve.

34
Q

What is the resting state of the vestibular fibres?

A

They are tonically fired, so information about head movement is always generated.

35
Q

How does auditory input travel to the brain?

A

Sensory nerve fibres travel along the vestibuocochlear cranial nerve to project to the vestibular nuclei in the brainstem. Vestibular nuclei uses this information to maintain posture and balance by sending efferent fibres to the cerebellum, extra-ocular muscles and limbs.

36
Q

What is the vestibulo-ocular reflex?

A

Gaze stabilising reflex where the eyes move in the opposite direction to the head to maintain balance, stimulating the lateral semicircular canal.

37
Q

What is the mechanism of the vestibulo-ocular reflex?

A

When the head moves quickly to the left, the eyes must move to the right.
The left head movement stimulates the left semicircular canal. This projects to the vestibular nuclei and stimulates the oculi motor nuclei for the right abducens for right lateral rectus and left oculomotor for left medial rectus. This moves the eyes to the right.

Right semicircular canal is being inhibited by the left head movement stimuli, due to direction of endolymph.

38
Q

What is nystagmus?

A

Involuntary eye movements

39
Q

How to determine medial longitudinal fasiculus in brainstem lesion?

A

Only one eye moves in response to water insertion.

40
Q

How to tell a lower brainstem lesion in caloric test?

A

Neither eye moves in response to water insertion.

41
Q

What is the protective reflex?

A

When falling, the head tips forward and stimulates the anterior semicircular canal which projects to the vestibular nuclei.This activates the medial vestibulospinal tract to stimulate the neck muscles for extension upwards and lateral vestibulospinal tract to stimulate the extensor muscles of the limb and proximal muscles to prevent injury.

Vestibular plasticity can occur where it adjust to new altitudes like a boat..

42
Q

What is the hopping reaction?

A

When there is poor stable balance, the body will hop to a new position.

43
Q

What is the anticipatory postural control?

A

Activation of limb muscles before movement occurs in order to stabilise the body and maintain posture. It is learned before it eventually becomes automatic. The reticular formation is an important structure for central command, and vestibular nuclei provide compensatory control.

44
Q

What is the positive supporting reflex?

A

When a limb is placed on the ground, brainstem stimulates the stiffening of the limb by increasing the extensor muscle tone, with some input from the spinal cord via the Ia afferents which increase firing of alpha motor neurons.

45
Q

What is Meniere’s syndrome?

A

Idiopathic increase in endolymph fluid volume results in temporary attacks of deafness, tinnitus or vomiting. Only the symptoms of nausea and vomiting can be treated with anti-histamines or prochlorperazine.

46
Q

What is benign paroxysmal vertigo?

A

Dislodging of calcium carbonate crystals in the otolith organs disrupts the flow of endolymph and causes dizziness in certain head directions. Can be treated using Epley or Semont manoeuvre.

47
Q

What is migraine associated vertigo?

A

Vertigo which occurs in people with a history of migraine.

Year 2 (247 decks)

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