균형 balance에 대한 탐구 by 김송준

[문형철]

감사합니다. ㅎㅎㅎ

panic bird..

balance and equilibrium의 차이

1. balance는 visual function, vestibular function, somatosensory function의 통합기능

# visual function은 초점시와 주변시의 개념이해, 초점시를 이용한 균형증진의 이해

  vestibulo-ocular reflex

  pertubation 바닥에서 balance training을 할때, 초점시를 이용하면 균형능력이 순간적으로 증진함. 

# vestibular function

   vestibulo-spinal reflex의 개념이해

   vestibulo-spinal tract의 이해

# somatosensory function

  articular neurology의 deep mechanoreceptor

  muscle spindle and GTO의 muscle mechanoreceptor

  skin, fascia의 mechanoreceptor and afferent input 그리고 pathway

 somatosensory pathway and sensorimotor control의 개념이해

이러한 개념들의 통합해야!!

올바른 지식을 바탕으로 한 올바른 상상력(연상력)...

The vestibulo-ocular reflex (VOR), sometimes known as but not completely synonymous with^[1] the oculocephalic reflex (which itself is colloquially known as the "doll's head reflex" and is used to assess the health of coma patients, along with VOR)^[1] is a reflex eye movement that elicits eye movement by stimulating the vestibular system. This reflex functions to stabilize images on the retinas (in yoked vision) during head movement by producing eye movements in the direction opposite to head movement, thus preserving the image on the center of the visual field(s). 

- 전정안구반사는 oculocephalic reflex로 알려져있으나 완전 동의어는 아님.

- reflex eye movement는 전정계 자극에 의해 눈움직임을 유도함. 

- 이 반사기능은 머리 움직임 동안 망막에 이미지를 안정화시킴. 

For example, when the head moves to the right, the eyes move to the left, and vice versa. Since slight head movement is present all the time, the VOR is very important for stabilizing vision: patients whose VOR is impaired find it difficult to read using print, because they cannot stabilize the eyes during small head tremors, and also because damage to the VOR can cause vestibular nystagmus.^[2] The VOR does not depend on visual input. It can be elicited by caloric (hot or cold) stimulation of the inner ear, and works even in total darkness or when the eyes are closed. However, in the presence of light, the fixation reflex is also added to the movement.^[3]

- 예를들어, 머리를 우측으로 움직일때 눈은 좌측으로 움직이고 반대로 똑같음. 약간의 머리움직임이 항상 존재하기 때문에 전정안구반사는 시각을 안정화시키는데 매우 중요함. 

- 전정안구반사가 손상된 환자는 머리의 작은 움직임 동안 눈을 고정할 수없기 때문에 프린트를 이용하여 읽는 것에 어려움을 겪음. 뿐만 아니라 전정안구반사 손상은 전정안진을 야기할 수 있음. 

- 전정안구반사는 시각입력정보 의존하지 않음. 그것은 뜨거움 또는 차가움 자극이 귀에 전달되는 자극에 의해서 유도될 수 있음. 가벼운 불빛이 존재할때 반사고정은 움직임을 더함. ...

In other animals, the gravity organs and eyes are strictly connected. A fish, for instance, moves its eyes by reflex when its tail is moved. Humans have semicircular canals, neck muscle "stretch" receptors, and the utricle (gravity organ). Though the semicircular canals cause most of the reflexes which are responsive to acceleration, the maintaining of balance is mediated by the stretch of neck muscles and the pull of gravity on the utricle (otolith organ) of the inner ear.^[3]

- 다른 동물에서는, 중력기관과 눈은 엄격하게 연결됨. 예를들어 물고기는 꼬리가 움직일때 반사에 의해서 눈을 움직임. 

- 인간의 경우 반원형 canal, 목 근육 신장 수용기와  중력기관인 utricle(내이의 타원낭)을 가짐. 반원형 canal이 가속에 반응하는 반사의 대부분을 야기하고, 균형유지는 목근육의 신장과 내이의 타원낭에서 중력 당김에 의해서 매개됨. 

The VOR has both rotational and translational aspects. When the head rotates about any axis (horizontal, vertical, or torsional) distant visual images are stabilized by rotating the eyes about the same axis, but in the opposite direction.^[4] When the head translates, for example during walking, the visual fixation point is maintained by rotating gaze direction in the opposite direction, by an amount that depends on distance.^[5]

- 전정안구반사는 회전과 평행이동 측면을 가짐. 머리가 어떤 축에 대해서 회전할때, 먼거리 시각이미지는 같은 축에 대해서 눈을 회전함에 의해서 안정화함. 머리가 평행이동할때, 예를들어 앞으로 걸어갈때, 시각고정점은 반대쪽 방향에서 응시방향회전에 의해서, 거리에 의존하는 양에 의해서... 시각고정점은 유지됨. 

The VOR is ultimately driven by signals from the vestibular apparatus in the inner ear. The semicircular canals detect head rotation and drive the rotational VOR, whereas the otoliths detect head translation and drive the translational VOR. The main "direct path" neural circuit for the horizontal rotational VOR is fairly simple. It starts in the vestibular system, where semicircular canals get activated by head rotation and send their impulses via the vestibular nerve (cranial nerve VIII) through Scarpa's ganglion and end in the vestibular nuclei in the brainstem. 

- 전정안구반사는 궁극적으로 내이에서 전정기관부속물로부터의 신호에 의해서 유도됨. 반원 canals은 머리 회전을 발견하고, 회전성 전정안구반사를 유도함. 반면에 이석은 머리 평행이동을 발견하고, 평행이동성 전정안구반사를 유도함. 평행회전 전정안구반사를 위한 direct path 신경서킷은 매우 간단함. 그것은 전정계에서 시작하고 반면에 반원 canal은 머리 회전에 의해 활성화된 신호를 얻고, 전정신경을 통해 임펄스를 중뇌로 전달함. 

From these nuclei, fibers cross to the contralateral cranial nerve VI nucleus (abducens nucleus). There they synapse with 2 additional pathways. One pathway projects directly to the lateral rectus of eye via the abducens nerve. Another nerve tract projects from the abducens nucleus by the medial longitudinal fasciculus to the contralateral oculomotor nucleus, which contains motorneuronsthat drive eye muscle activity, specifically activating the medial rectus muscle of the eye through the oculomotor nerve.

- 이러한 신경핵으로부터 섬유는 반대측 cranial nerve(외전 신경)을 가로지름. 두개의 길이 있음. 하나 길은 직접적으로 외전신경을 통해 외측 rectus of eye로 투사됨. 

- 다른 신경은 외전신경으로부터 .....

Another pathway (not in picture) directly projects from the vestibular nucleus through the ascending tract of Dieters to the ipsilateral medial rectus motoneuron. In addition there are inhibitory vestibular pathways to the ipsilateral abducens nucleus. However no direct vestibular neuron to medial rectus motoneuron pathway exists.^[6]

- 다른 ..

Similar pathways exist for the vertical and torsional components of the VOR.

In addition to these direct pathways, which drive the velocity of eye rotation, there is an indirect pathway that builds up the position signal needed to prevent the eye from rolling back to center when the head stops moving. This pathway is particularly important when the head is moving slowly, because here position signals dominate over velocity signals. 

David A. Robinson discovered that the eye muscles require this dual velocity-position drive, and also proposed that it must arise in the brain by mathematically integrating the velocity signal and then sending the resulting position signal to the motoneurons. Robinson was correct: the 'neural integrator' for horizontal eye position was found in the nucleus prepositus hypoglossi^[7] in the medulla, and the neural integrator for vertical and torsional eye positions was found in the interstitial nucleus of Cajal^[8] in the midbrain. The same neural integrators also generate eye position for other conjugate eye movements such as saccades and smooth pursuit.

Excitatory example[edit]

For instance, if the head is turned clockwise as seen from above, then excitatory impulses are sent from the semicircular canal on the right side via thevestibular nerve (cranial nerve VIII) through Scarpa's ganglion and end in the right vestibular nuclei in the brainstem. From this nuclei excitatory fibers cross to the left abducens nucleus. There they project and stimulate the lateral rectus of the left eye via the abducens nerve. In addition, by the medial longitudinal fasciculus and oculomotor nuclei, they activate the medial rectus muscles on the right eye. As a result, both eyes will turn counterclockwise.

Furthermore, some neurons from the right vestibular nucleus directly stimulate the right medial rectus motoneurons, and inhibits the right abducens nucleus.

Speed[edit]

The vestibulo-ocular reflex needs to be fast: for clear vision, head movement must be compensated almost immediately; otherwise, vision corresponds to a photograph taken with a shaky hand. To achieve clear vision, signals from the semicircular canals are sent as directly as possible to the eye muscles: the connection involves only three neurons, and is correspondingly called the three neuron arc. Using these direct connections, eye movements lag the head movements by less than 10 ms,^[9] and thus the vestibulo-ocular reflex is one of the fastest reflexes in the human body.

Gain[edit]

The "gain" of the VOR is defined as the change in the eye angle divided by the change in the head angle during the head turn. Ideally the gain of the rotational VOR is 1.0. The gain of the horizontal and vertical VOR is usually close to 1.0, but the gain of the torsional VOR (rotation around the line of sight) is generally low.^[4] The gain of the translational VOR has to be adjusted for distance, because of the geometry of motion parallax. When the head translates, the angular direction of near targets changes faster than the angular direction of far targets.^[5]

If the gain of the VOR is wrong (different from 1)—for example, if eye muscles are weak, or if a person puts on a new pair of eyeglasses—then head movement results in image motion on the retina, resulting in blurred vision. Under such conditions, motor learning adjusts the gain of the VOR to produce more accurate eye motion. This is what is referred to as VOR adaptation.

Ethanol consumption can disrupt the VOR, reducing dynamic visual acuity.^[10]

Testing[edit]

This reflex can be tested by the Rapid head impulse test or Halmagyi-Curthoys-test, in which the head is rapidly moved to the side with force, and is controlled if the eyes succeed to remain looking in the same direction. When the function of the right balance system is reduced, by a disease or by an accident, quick head movement to the right cannot be sensed properly anymore. As a consequence, no compensatory eye movement is generated, and the patient cannot fixate a point in space during this rapid head movement.

Another way of testing the VOR response is a caloric reflex test, which is an attempt to induce nystagmus (compensatory eye movement in the absence of head motion) by pouring cold or warm water into the ear. Also available is bi-thermal air caloric irrigations, in which warm and cool air is administered into the ear.

Comatose patients[edit]

In comatose patients, once it has been determined that the cervical spine is intact, a test of the vestibulo-ocular reflex can be performed by turning the head to one side. If the brainstem is intact, the eyes will move conjugately away from the direction of turning (as if still looking at the examiner rather than fixed straight ahead). Negative "doll's eyes" would stay fixed midorbit, and having negative "doll's eyes" is therefore a sign that a comatose patient's brainstem is functionally not intact.

Testing complications[edit]

Currently, vestibulo-ocular reflexes can only be comprehensively tested in specially equipped laboratories. The tests sometimes provide valuable diagnostic information; however, the tests can be time-consuming and expensive to administer^{[citation needed]}. The scleral search coil can be used to assess the vestibulo-ocular reflex.

Role of cerebellum[edit]

The cerebellum is essential for motor learning to correct the VOR in order to ensure accurate eye movement. Motor learning in the VOR is in many ways analogous to classical eyeblink conditioning, since the circuits are homologous and the molecular mechanisms are similar.

[참마음]

감사합니다~덕분에 공부하가 쉽고 즐겁습니다.~