Contribution of hind limb flexor muscle afferents to the timing of phase transitions in the cat step cycle
Contribution of hind limb flexor muscle afferents to the timing of phase transitions in the cat step cycle
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DOI：
10.1152/jn.1996.75.3.1126
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发表时间：
1996-03-01
影响因子：
2.5
通讯作者：
Pearson, KG
中科院分区：
文献类型：
--
作者：
Hiebert, GW;Whelan, PJ;Pearson, KG
1. 在这项研究中，我们测试了这样的假设：发出后腿屈肌长度信号的肌梭传入神经参与终止伸肌活动并在行走过程中启动屈曲。在自发行走的去大脑猫中，髋屈肌髂腰肌（IF）、踝屈肌胫骨前肌（TA）和伸指长肌（EDL）在步周期的不同阶段被拉伸或振动。然后检查肌电图振幅、持续时间和时间的变化。还考察了电刺激I组和II组神经传入神经对TA和EDL的影响。 2．在站立阶段，各个屈肌（UP、TA 或 EDL）的伸展会减少伸肌活动的持续时间，并促进屈肌爆发活动的发生。对侧步态周期也受到拉伸的影响，屈肌活动的持续时间缩短，伸肌活动发生得更早。因此，在站立阶段屈肌的伸展可将运动节律重置为同侧屈曲和对侧伸展。3．电刺激 TA 和 EDL 肌肉传入神经的结果表明，不同组的传入神经负责步循环的重置。当刺激强度处于第 II 组范围 (2-5 xT) 时，刺激 TA 神经会重置运动步周期。相比之下，刺激 EDL 神经会产生 1.2-1.4 xT 范围内的步进周期的强烈重置，其中主要来自肌梭的 Ia 组传入神经将被激活。 4．站立期间 IP 或 EDL 的振动减少了伸肌活动的持续时间，其减少量与 Ia 组强度下肌肉拉伸或 EDL 电刺激所产生的减少量相似。这表明来自 IP 和 EDL 的 Ia 组传入神经能够重置运动模式发生器。 TA的振动不影响运动节律。5．在屈曲阶段拉伸 TP 或电刺激 TA 传入神经 (5 xT) 不会改变屈肌活动的持续时间。屈曲期间以 1.8-5 xT 刺激 EDL 神经可增加屈肌活动的持续时间。在我们的准备工作中，我们都没有观察到在屈曲期间激活屈肌传入神经时复位至伸展。6。我们的结论是，当屈肌在步态的站立阶段伸长时，它们的纺锤体传入神经（EDL 和 IP 的 Ia 组传入神经，TA 的 II 组传入神经）会抑制脊柱中枢产生伸肌活动，从而促进摆动的开始。
1. In this investigation, we tested the hypothesis that muscle spindle afferents signaling the length of hind-leg flexor muscles are involved in terminating extensor activity and initiating flexion during walking. The hip flexor muscle iliopsoas (IF) and the ankle flexors tibialis anterior (TA) and extensor digitorum longus (EDL) were stretched or vibrated at various phases of the step cycle in spontaneously walking decerebrate cats. Changes in electromyogram amplitude, duration, and timing were then examined. The effects of electrically stimulating group I and II afferents in the nerves to TA and EDL also were examined.2. Stretch of the individual flexor muscles (UP, TA, or EDL) during the stance phase reduced the duration of extensor activity and promoted the onset of flexor burst activity. The contralateral step cycle also was affected by the stretch, the duration of flexor activity being shortened and extensor activity occurring earlier. Therefore, stretch of the flexor muscles during the stance phase reset the locomotor rhythm to flexion ipsilaterally and extension contralaterally.3. Results of electrically stimulating the afferents from the TA and EDL muscles suggested that different groups of afferents were responsible for the resetting of the step cycle. Stimulation of the TA nerve reset the locomotor step cycle when the stimulus intensity was in the group II range (2-5 xT). By contrast, stimulation of the EDL nerve generated strong resetting of the step cycle in the range of 1.2-1.4 xT, where primarily the group Ia afferents from the muscle spindles would be activated.4. Vibration of IP or EDL during stance reduced the duration of the extensor activity by similar amounts to that produced by muscle stretch or by electrical stimulation of EDL at group Ia strengths. This suggests that the group Ia afferents from IP and EDL are capable of resetting the locomotor pattern generator. Vibration of TA did not affect the locomotor rhythm.5. Stretch of TP or electrical stimulation of TA afferents (5 xT) during the flexion phase did not change the duration of the flexor activity. Stimulation of the EDL nerve at 1.8-5 xT during flexion increased the duration of the flexor activity. In none of our preparations did we observe resetting to extension when the flexor afferents were activated during flexion.6. We conclude that as the flexor muscles lengthen during the stance phase of gait, their spindle afferents (group Ia afferents for EDL and IP, group II afferents for TA) act to inhibit the spinal center generating extensor activity thus facilitating the initiation of swing.