神经解剖学课件：internal structure of spnial cord

1、Spinal cordInternal structureFunctions of spinal cordInternal structures Grey matter White matter Functions of the spinal cordTransmittingreflexes Functions of the spinal cord Functions of the spinal cordInternal Structure gray matter white matter. Internal Structure Grey matterventral, lateral(T1L1

2、3) dorsal horns/columns White matterdorsal, lateral and ventral funiculi. Grey matterGrey matter is mainly formed by the nucleiforms a butterfly-shaped or “H”-shaped core of the spinal cord.Nuclei in the Anterior Horn somatic motor neurones mainly innervate the skeletal muscle and produces contracti

3、le tension within a muscle. Three main kinds of neurons2 groups -motor neuron innervates the extrafusal fibers of the skeletal muscle and produces movement.The smaller -motor neurongives rise to efferent fibers, these fibers also emerge via the ventral rootlet and supplies the intrafusal muscle fibe

4、rs of neuromuscular spindles, which play important role in the reflex regulation of muscle tonus. Renshaw cell recurrent inhibitory pathway form motor axon collaterals via Renshaw cell back to -motor neuron is regarded as a negative feedback mechanism. a-motor neurons, g-motor neurons. Nuclei in the

5、 Anterior Hornmedial nuclear group most segments of the spinal cord, innervate the skeletal muscles of the neck and trunk including the diaphragm, intercostal and abdominal musculaturelateral nuclear group cervical and lumbar enlargements supplying the muscles of the limbs.3 types, 2 groups of anter

6、ior hornThe groups or nuclei of nerve cells in the grey columns Nuclei in the lateral or intermediolateral hornThere are several cells collections in the intermediate zone.Nuclei of lateral horn:lateral nucleus T1L3: neuron of sympathetic preganglia fiber S24: parasympathetic intermediomedial nucleu

7、s: posterolateral to the central canalreceives the collateral branches of the dorsal root fibers and gives rise to fibers which constitute the spinocerebellar tract of both side of the spinal cord.Nuclei in the Posterior Horn 1. marginal layer2. Substantia gelatinosa3. nucleus proprius4. dorsal nucl

8、eus/ nucleus thoracicusNuclei in the Posterior Horn dorsal nucleus (thoracic nucleus) this nucleus is situated in the medial portion of the base of posterior horn. It begins to be well defined in C8 and extends throughout the thoracic and upper lumbar segments. It receives the collateral branches of

9、 the primary afferent fibers. The axons contribute fibers to the posterior spinocerebellar tractsposterior median septum White matter surrounds the grey matter divided into three pairs of funiculi: the posterior, lateral and anterior funiculi. consists of ascending , descending fibers (tracts), and

10、fasciculus proprius Long tracts ascending tracts carry sensory impulses to brain descending tracts modulate the activity of the spinal cord short tracts ascending and descending connect with the segments of spinal cord Long ascending tractsFasciculus gracilis and fasciculus cuneatus posterior spinoc

11、erebellar tract anterior spinocerebellar tract lateral spinothalamic tract anterior spinothalamic tract spinoreticular fibers Ascending spinal tractscarry impulses of pain, thermal, tactile, and joint receptors to the brain. Some of this information eventually reaches a conscious level(the cerebral

12、cortex) some is for subconscious centers (e.g. the cerebellum)common characteristics of ascending spinal tracts: 3 order neurons first neuron3 order neurons of ascending pathway Second neuroncell body in the spinal cord or medulla.axons crosses over (decussate) to opposite side of the CNS and ascend

13、s to the thalamus, where it terminates upon the third neuron.Third neuroncell body in the thalamus.axon passes to the somatosensory cortex of parietal lobe of the cerebral hemisphere.In its course, axon pass through the internal capsule Fasciculus gracilis and fasciculus cuneatus: Fasciculus gracili

14、s situated mediallyFasciculus cuneatus situated laterallyThe tracts carry impulses concerned with proprioception (movement, and joint position sense) and discriminative touch.spinothalamic tract:the first order neurons: the spinal ganglion, enter the spinal cord through dorsal roots of the spinal ne

15、rve , then end the nucleus proprius The fibers from the nucleus proprius cross in the anterior white commissure and ascend in the opposite lateral funiculus to form spinothalamic tract. The tract passes through the brain stem and ends directly to the thalamus. carry information related to pain and t

16、hermal sensations, and also non-discrimination touch and pressure.Anterior and lateral spinothalamic tract lateral spinothalamic tract- pain and thermal sense Lissauers tract ascend one to two segments before crossing. somatotopically arranged anterior spinothalamic tract touch and pressure Anterior

17、 and lateral spinothalamic tractSpinothalamic Tractposterior spinocerebellar tract inferior cerebellar peduncle. anterior spinocerebellar tract superior cerebellar peduncle. They convey subconscious proprio-ceptive sensation to the cerebellum. spinocerebellar tractOther Ascending Pathways:Spinotecta

18、l TractSpinoreticular TractSpino-olivary TractVisceral Sensory TractsLong Descending Tractssomatic movement (motor function), visceral innervation and the modification of muscle tone. mostly arise from the cerebral cortex or brain stem.Corticospinal system: arises from the cerebral cortex, descends

19、throughout the internal capsule and brain stem, and divides into two tracts:lateral and anterior corticospinal tracts lateral corticospinal tract decussates in the medulla and descends medial to the posterior spinocerebellar tract in the spinal cord. extends to the most caudal part of the cord and p

20、rogressively diminishes in size as more and more fibers leave to terminate in the anterior horn of the grey matter. has somatotopical arrangement from medial to lateral in cervical, thoracic, lumbar and sacral order. anterior corticospinal tractIt occupies a strip带 area adjacent to the anterior medi

21、an fissure. normally extends only to the upper thoracic cord, most of these fibers decussate in the anterior white commissure before they terminate in the anterior horn. Corticospinal systemLower motor neurons Upper motor neuronsRubrospinal红核脊髓tractventral to and partially intermingled部分混合 with fibe

22、rs of the lateral corticospinal 皮质脊髓tract.arise from the red nucleus of the midbrain中脑, and synaptic contact with the cell in the contralateral对侧 posterior horn and intermediate zone of upper cervical cord facilitate flexor motor neurons and control the muscle tone of the flexor muscle groups.Vestib

23、ulospinal tractarise from the lateral vestibular nucleus of the same side and descends to the entire length of the spinal cord in the anterior funiculus and adjacent part of the lateral funiculus. Vestibulospinal fibers enter the base of the anterior horn and the intermediate zone. The function of t

24、his tract is to increase the extensor muscle tone and inhibites the motor neurons of flexors.Reticulospinal tractThe pontine and medullary reticular formations give off fibers to form reticulospinal tract descending to the spinal levels, but its position has not been established in man. This tract is thought to play significant role in moderation of muscle tone. Short Ascending and Descending Tracts Fasciculus proprius/intersegmental fasciculussurrounds the grey matter of the spinal co