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그물체 & 소뇌

(Reticualr formation & Cerebellum)

충남의대 해부학교실

김 동 운

그물체 (reticular formation, 망상체)

뇌줄기의 뒤쪽부분 상당히 넓은 부분을 차지하며, 신경세포무리와그 섬유다발들이 그물모양으로 배열 모든 단계의 CNS와 직접적인 그리고 간접적인 연결을 가짐으로써

Control of movement

Sleep-arousal cycle [의식 &각성]

Perception of pain

Regulation of visceral activity

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Motor control centers in the brainstem

Serve to organize a variety of somatic movements

Maintenance of balance

Regulation of posture

Orientation of visual gaze

Vestibular complex, reticular formation,

V-S: a rapid compensatory feedback response to any

postural instability from ear

Reticular formation:

controlled largely by other motor centers in the Cx,

hypothalamus, or brainstem.

Initiate feedforward adjustments that stabilize

posture during ongoing movements

Feedforward and feedback mechanisms of

postural control

- Feedforwad postural responses are “programmed” and typically precede the onset of limb movement. - Feeback responses are initiated by sensory inputs that detect postural instability.

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Vestibulospinal tract

Medial V-S tr.

Terminate in the medial ventral

horn of spinal cord

Head position by reflex activation

of neck m.

Lateral V-S tr.

Terminate a slightly more lateral

position relative to the medial V-S

tr.

Regulate proximal m. of the limbs

Limb extensor (antigravity)

Vestibulo-cervical reflex (VCR)

Vestibulo-spinal reflex (VSR)

교차(X)

The reticular formation: 2 catogories

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Reticular formation

- modulates forebrain activity

Conscious state

Pain modulation

Periaqueductal gray mater (PGM)

Raphe nu.

Consciousness (의식): 자신과 자신을 둘러싼 환경을인지

정상적인 의식소실: 수면 (sleep)

비정상적인 의식소실: 뇌손상, 뇌질환

단계

1. Alert

2. Drowsy: ligth stimuli (기면)

3. Stupor: painful stimuli (혼미)

4. Coma

Locus coerulus: noradenregic neurons

Raphe nu.: serotonergic neurons

Magnocellular neurons in Pedunculopontine

nu.: cholinergic neurons

• Central tegmental tr.• 1. 의식유지(LC CT)• 2. 미각

* 의식상태를 유지하기 위해선 CT 경로가 온전해야 한다.

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그림 8-14

미각(Gustatory sense)

VII, IX, X

Solitary nu.

Central tegmental tr.

VPM of thalamus

Gustatory cortex

Spinothalamic tract

Red line: 다리Blue line: 팔

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Reticular formation (II): Premotor functions

Gaze movements

PPRF (paramedian pontine reticular formation)

Orofacial behavior

Mastication

Facial expression

Sneezing, hiccupping, yawning, swallowing

Autonomic centers

Respiratory, cardiovascular function

Vomiting, laughing, crying

** 하지만, Reticulospinal tract은 reticular formation전장에 걸쳐 있다.

Reticulospinal tract:Indirect pathways from the motor cortex to the spinal cord

Temporal and spatial

coordination of limb and

trunk movements

* Neurons in the motor cortex that

supply the lateral part of the ventral

horn to initiate movements of the

distal limbs, also terminate on

neurons in the reticular formation to

mediate postural adjustments that

support the movement. The

reticulospinal pathway terminates in

the more medial parts of the ventral

horn, where lower motor neurons

that innervate axial and proximal

muscles are located. Thus, the motor

cortex can influence the activity of

spinal cord neurons via both direct

and indirect routes.

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소뇌 (cerebellum)

평형유지, 근육의 수축과 이완을 조절, 운동에 관련된학습과 학습된 운동명령의 실행에도 관여

소뇌의 질환이 있을 때 운동장애가 발생하기는 하지만수의운동의 마비가 일어나지 않는다. 이러한 이유로 소뇌는 의식과 무관하다고 알려졌으나 최근에는 다른 의견도 제시되고 있다.

The Cerebellum

Function: Sequence of muscle contractions

Execution of planned, voluntary, multijoint

movements

Programming the cerebellum

Process of learning a new skill

New motor program created to ensure smooth

movement

Ataxia Uncoordinated and inaccurate movements

Caused by cerebellar lesions

Symptoms

Dysynergia, dysmetric

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Median plane; Arbor vitae

Sagittal plane; dentate nucleus

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Organization and subdivisions of the cerebellum

소뇌핵 (cerebellar nuclei)

Fastigial nucleus (꼭지핵)

Interposed nucleus

Globose nucleus (둥근핵)

Emboliform nucleus (마개핵)

Dentate nucleus (치아핵)

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소뇌의 기능적 구획

Vestibulocerebellum: Flocculonodular lobe

Afferent: vestibular nucleus

=Archicerebellum (어류, 하등 양서류)

Maintain equlibrium, control head and eye movement

Spinocerebellum

Vermis of ant. lobe & paravermal zone of the hemisphere

Palocerebellum (고등 양서류, 파충류, 조류)

Afferent: proprioception of muscle, tendon, from spinal cord

Efferent: vestibulospinal, rubrospinal, reticulospinal tract

Pontocerebellum (=cerebrocerebellum)

Lat. hemisphere

Neocerebellum (포유류)

Afferent: cerebropontocerebellar tract, olivecerebellar tract

Efferent: thalamus cerebral cortex

Smooth, accurate, coordinated voluntary movement

소뇌의 계통발생학적 구획 소뇌의 기능적 구획

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Functional organization of the inputs to the

cerebellum

1. Major route: via middle cb ped: pontocerebellar tr.

2. Minor route: via inf cb ped: 1. vestibulocerebellar tr.

2. dorsal nucleus of Clarke (cervical) cuneate nucleus (medulla)mesencephalic nu. of CNV spinocerebellar tr.

3. Inferior olivary nu. learning & memory

Pontocerebellum

1. corticospinal tract,

corticoreticular tract,

reticulspinal tract의 활성을 조절

2. Purkinje cell의억제작용으로 대뇌

겉질의 운동영역에 영향을 끼쳐 수의

운동시 여러 근육이 순차적으로 부드

럽게 수축하도록 할뿐만 아니라 수축

력, 운동의 방향과 범위등을 세밀하게

조절한다.

3. 소뇌반구는 소뇌다리교차를 통해 대

뇌겉질과 연결되기때문에 같은쪽 신체

부위의 근육을 조절한다.

4. 소뇌의 손상등으로 인한 운동조절기

능의 장애를 ataxia (조화운동불능)이

라 한다.

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Spinocerebellum: 동측, 고유감각정보

Somatic sensory system: 무의식적 고유감각 unconscious proprioception

1) 척수내 위치: Golgi tendon or muscle spindle로부터 고유감각

2) 구성섬유: Nucleus dorsalis (of Clarke) 및 Lamina VII의 axon

3) 경로

- Post. spinocerebellar tr (thoracicolumbar segment, T1-L3)

; dorsal nucleus of Clarke post. spinocerebellar tr.

non-X

via inf. cerebellar peduncle)

Cerebellar cortex

* Cuneocerebellar tract는 post. spinocerebellar tr의 일부로 간주됨 (above T1)

- Cervical dorsal root Cuneate fasiculus Accessory cuneate nu.

cuneocerebellar tract (via inf. cerebellar tract) Cb

* 목과 팔의 고유감각

** 시냅스가 매우 적어 가장 빠름

-결국 ant. 와 post spinocerebellar tract은 모두 한쪽 상하지의 고유감각을 같은쪽소뇌에 전달한다.

-마지막에 mossy fiber로 종결

- Post는 몸통과 다리Cuneo는 목과 팔의 무의식적인고유감각이고 Ant는 스넬책에서는 몸통과 팔 다리 모두이지만bar책에서는 다리의 고유감각이라고 나왔는데 다른책에서는 아

직 밝혀진것은 없다고 나와있다.

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Vestibulocerebellum: 동측, 평형

1. Affererent:

1) Vestibular ganglion

2) Vestibular nucleus

* 직접적으로 뇌줄기에 연접하는매우 드문경우

3) Fastigial nuclues

4) contralateral inf. olivary complex

2. Efferent

1) Fastigial nucleus

2) Vestibular nuclei

3) Fastigila nucleus reticular formation (eye movement)

Homunculi illustrating the somatotopicorganization of the cerebellar cortex

- Spinocerebellum contains at least two maps of the body

- Note that the body is represented on the cerebellar cortex more than once and that the axialmusculature is represented in a medial position, whereas the distal musculature is represented more laterally. The neuronal regions associated with regulation of the distal musculature are shown in green, and the regions associated with the axial musculature are shown in red.

Spinocerebellum: IpsilateralCS tract: contralateral

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Functional organization of cerebellar outputs

VOR

Functional organization of the major outputs

from the cerebellum to cortical motor systems

1. Thalamus Cx

2. Red nucleus: feedback for the adaptive functions of cerebellar circuits

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Functional organization of the major outputs from the

cerebellum to brainstem motor systems

Spinocerebellum

Efferent:

Fastigial nucleus

via inf. cerebellar peduncle reticular formation

Control of axial and proximal limb musculature in the

medial ventral horn of spinal cord

Interposed nucleus

via sup. cerebellar peduncle red nucleus or thalamus

Globose-Emboliform-Rubral pathway

After twice decussation, finally rubrospinal tract

Interact with motor regions in the frontal lobe concerned

with voluntary movements of the limbs

Function synergistically with the later C-S tract

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Neurons and circuits of the cerebellum

1. Input1. Major: Mossy fiber from Pontine nu.2. Minor: Climbing fiber from inf. olivary nu.

2. Output: Purkinje cells

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1. 하나의 Purkinje cell에는 단 하나의 Climbing fiber와 수많은 연접을 한다 training signal

2. Mossy fiber는 parallel fiber가 되어 여러 개의 purkinje cell과 연접한다3. 또한 여러 개의 parallel fiber가 하나의 purkinje cell에 연접한다.

4. 흥분성전달물질: Glutamate, 억제성 신경물질: GABA

Inferior olivary complex of Nuclei

다양한 부위에서 기원하는 들신경섬유를 받는다.

척수 전 높이의 반대쪽 뒤뿔: spino-olivary tr.

같은쪽 red nucleus

중간뇌의 red nucleus와 periaqueductal gray

matter (중심회색질)에서 기원하여 아래올리브핵으로 향하는 경로: central tegmental tract

같은쪽 대뇌피질

날신경섬유

Olivocerebellar tract: 아래소뇌다리의 가장 중요한 성분 climbing fiber

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Vertebrate models of learning

Synaptic plasticity in the cerebellar cortex

Cerebellum: Important site for motor learning

Anatomy of the cerebellar cortex

Features of Purkinje cells

Dendrites extend only into molecular layer

Cell axons synapse on deep cerebellar nuclei

neurons

GABA as a neurotransmitter

Marr-Albus-Ito theory of motor learning

Excitatory and inhibitory connections in the

cerebellar cortex and deep cerebellar nuclei

- The inhibitory projections of Purkinje cells serve to shape the discharge patterns that deep nuclei neurons generate in response to this direct mossy and climbing fiber input.

- Excitatory vs. inhibitory loops

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Pathological changes can provide insights

about cerebellar function

Alchohol abuse

-선택적으로 ant. Spinocebellum에 손상

-주로 발 (somatotopic 참조)

- a wide and staggering gait

Genetic analysis of cerebellar function

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Genetic analysis of cerebellar function

reeler gene의 기능은 우연히 발견,Tenascin, laminin, fibronectin등과 homology가 있으며granular cell의 migration에 문제가 생겨 granular cell의 분포가 정상과 다르나 climbing, mossy fiber의 synaptic targeting은 그대로 유지됨.

Weaver gene의 문제시Granular cell이 사라짐기전은 잘 모름