主动脉压力感受器编码血压信号的新机制

发布时间：2018-04-22 06:16

本文选题：压力感受器 + 血压　；参考：《陕西师范大学》2010年博士论文

【摘要】： 压力感受器如何感受血压变化是感觉神经生理学的一个重要问题。神经生理学已经建立压力感受器通过调节动作电位频率进而感受静态和动态压力的基本概念：神经脉冲发放平均频率编码了外界刺激的强度,脉冲发放的频率数正比于刺激的强度值。由于感受器神经末梢的解剖结构非常微小,目前还不能直接通过实验观察其感受电位。随着神经科学、非线性科学、信息技术和计算机技术的交叉融合,已经形成了以理论和实验结合的神经动力学研究方向。利用非线性动力学的概念,可以对生命中复杂的神经放电模式、模式分岔(转迁)规律进行研究,为认识复杂多变的神经放电节律,揭示神经动态放电和动态外界信息之间的关系,探讨动态放电如何编码动态外界信号的机制。本文采用理论与实验相结合的研究方法,研究主动脉弓压力感受器编码动脉血压信号这个具体的编码环节的生物物理机制和生理学意义。通过对家兔和大鼠动脉压力感受器动态、静态血压变化作用下,神经单纤维放电模式及其转迁规律的研究。实验发现了感受器的5种活动状态：2类静息(分别对应低压阈值和高压阈值)和3类放电行为。放电行为是由血压变化过程中跨越两个阈值产生的。对应动态血压,跨越低压阈值,感受器在收缩压放电；跨越高压阈值,感受器表现为在收缩压放电的反常簇放电；位于两个阈值之间,持续放电。对应静压力,跨越低压阈值,感受器on-off放电；跨越高压阈值,感受器on-off放电或整数倍放电；位于阈值之间,周期一放电并随压力增加频率加快。实验静压力下出现了on-off放电和整数倍放电等非周期放电模式,模型仿真了这类结果,提示它们分别对应跨越超临界Hopf分岔和亚临界Hopf分岔的动力学行为。神经动力学的应用,为理解实验现象的机理提供了有力的理论依据。主要结果有 1.实验获得了随动态平均血压变化的感受器神经单纤维的放电模式转迁规律。随着平均压力升高,感受器神经单纤维放电依次经历低压静息-收缩压放电-连续放电-舒张压放电的“反常簇放电”-高压静息。识别了感受器神经单纤维的5种活动状态：3种放电和2种静息。在多例标本发现了新的“反常簇放电”现象,并认识到“反常簇放电”存在于高压力区间,其机理是“去极化阻滞”。 2.实验观察了静压力下感受器神经单纤维放电模式的转迁规律。随着静压力升高,感受器神经单纤维放电依次经历了低压静息-on-off放电-持续周期一放电-on-off放电或者整数倍放电-高压静息。和动态平均血压下的转迁规律类似,感受器的2种静息分别对应了低压和高压阈值。其中非周期的on-off放电和整数倍放电,提示在跨越阈值时,感受器放电遵循动力学的Hopf分岔机制。进而利用神经动力学的分岔理论可以解释感受器编码血压信号的机理。 3.构建了基于血压压力感受器感知血压过程的生物写实数学模型。该模型利用不同的函数,对应血管区、感受器区和编码区,分别仿真了血管壁的机械形变、感受器局部电位产生和编码区动作电位产生,进而构成完整的感受器数学模型。调节与实验相一致的参数变化,研究了该数学模型在静压力和动态血压变化下的放电模式及其转迁规律。 4.数学模型仿真结果揭示了放电节律的转迁规律的机制。随着静压力的增加,确定性模型会表现出静息、连续放电、静息的转迁历程。考虑噪声因素的作用,静压力增加时,放电节律会表现出静息、on-off放电、连续均匀放电、整数倍放电、静息的转迁历程,与实验中静压力增加的现象一致。在动压力作用下,随着平均压力的增加,放电会经历静息、血压峰值放电谷值不放电、连续放电、血压峰值不放电血压谷值放电、静息的历程,与实验一致。 5.对数学模型进行分析,随着静压力的增加,从静息变到放电对应亚临界Hopf分岔,从连续放电再到静息是超临界Hopf分岔。静压力下的on-off放电和整数倍放电是噪声分别在超临界和亚临界Hopf点附件诱发的随机节律。而“反常簇放电”是由于在动压力作用下电活动行为因为血压压力在跨越Hopf分岔点引起的：血压峰值处于静息而血压谷值时处于放电引起的。这就从理论上解释了这些新节律的产生的动力学机制。。上述结果表明,血压信号的改变会引起感受器兴奋性的变化,也就是去极化电流的动态变化。使得压力感受器的放电节律在以去极化电流作为分岔参数的放电节律静态分岔结构中,在平均血压对应的位置附近按照血压信号的时间历程“动态游走”,形成动态放电节律；动态放电节律的时间历程与血压信号的时间动态历程有较好的对应。利用非线性动力学分岔理论不仅从理论上揭示了血压信号引起感受器神经放电的机理,而且可以在包含放电频率在内的多个层面上,在理论层次上建立动态血压信号与相应动态放电之间的联系,进一步认识了感受器的编码机制。
[Abstract]:How bareporeceptor feelings of blood pressure change is an important problem in sensory neurophysiology. Neurophysiology has established the basic concept that bareporeceptor can feel static and dynamic pressure by regulating the frequency of action potential, which encodes the intensity of external stimuli, and the frequency of pulse distribution is proportional to the number of pulses. As the anatomical structure of the nerve endings of the receptor is very small, the sensory potential can not be observed directly by experiment. With the cross fusion of neuroscience, nonlinear science, information technology and computer technology, the research direction of the combination of theory and experiment has been formed. The concept of dynamics can be used to study the complex pattern of neural discharge and pattern bifurcation (transfer) in life, to understand the complex and changeable rhythms of neural discharge, to reveal the relationship between the dynamic discharge of the nerve and the dynamic external information, and to explore the mechanism of how dynamic discharge encodes the dynamic external signal.
This paper studies the biophysical and physiological significance of the specific coding link of aortic arch baroreceptor encoding arterial pressure signal by combining theoretical and experimental methods. Through the dynamic and static blood pressure changes in rabbit and rat arterial baroreceptor, the pattern of neural single fiber discharge and its transfer rules are used. The experiment found 5 active states of the receptor: 2 types of resting (corresponding to low pressure threshold and high pressure threshold respectively) and 3 types of discharge behavior. The discharge behavior is produced by two thresholds in the process of blood pressure change. It corresponds to the dynamic blood pressure, across the low pressure threshold, the receptor in the systolic pressure discharge, the threshold of the high pressure, the receptor performance. An anomalous cluster discharge in a systolic discharge; between two thresholds, continuous discharge. Corresponding static pressure, crossing low pressure threshold, receptor on-off discharge; crossing high pressure threshold, receptor on-off discharge or integer multiple discharge; between threshold, periodic discharge and increasing frequency with pressure force. Under experimental static pressure, on-off appears. The models of non periodic discharge, such as discharge and integer discharge, have simulated these results, suggesting that they correspond to the dynamic behavior of crossing over the supercritical Hopf bifurcation and subcritical Hopf bifurcation, and the application of neural dynamics provides a powerful theoretical basis for understanding the mechanism of the experimental phenomena.
The main results are
The 1. experiment obtained the change rule of the discharge mode of the sensory nerve single fiber with the dynamic mean blood pressure change. With the increase of the average pressure, the single fiber discharge of the receptor nerve underwent the "abnormal cluster discharge" - the high pressure resting with the low pressure resting - systolic pressure discharge - the continuous discharge diastolic discharge, and identified the 5 of the receptor nerve single fiber. Activity state: 3 kinds of discharge and 2 kinds of resting. A new phenomenon of "abnormal cluster discharge" is found in several specimens, and it is recognized that "abnormal cluster discharge" exists in the high pressure range, and its mechanism is depolarization block.
2. the transition law of the single fiber discharge mode of the receptor nerve under static pressure was observed under the static pressure. With the increase of static pressure, the single fiber discharge of the receptor nerve experienced the low pressure resting -on-off discharge - the continuous cycle one discharge -on-off discharge or the integer multiple discharge - the high pressure resting. The 2 kinds of resting rest respectively correspond to the low pressure and high pressure threshold, in which the non periodic on-off discharge and the integer multiple discharge indicate that the Hopf bifurcation mechanism of the receptor discharge follows the dynamics when the threshold is crossed. Then the mechanism of the blood pressure signal encoded by the receptor can be explained by the bifurcation theory of the neural dynamics.
3. a biorealistic mathematical model is constructed based on the blood pressure baroreceptor, which uses different functions, corresponding to the vascular area, the receptor area and the coding region, to simulate the mechanical deformation of the blood vessel wall, the local potential generation of the receptor and the generation of the action potential of the coded region, and then form a complete mathematical model of the receptor. Adjusting the parameter changes consistent with the experiment, we studied the discharge pattern and transition rule of the mathematical model under static pressure and dynamic blood pressure.
4. the simulation results of the mathematical model reveal the mechanism of the transition law of the discharge rhythm. With the increase of static pressure, the deterministic model will show resting, continuous discharge, and resting transition course. Considering the effect of the noise factors and the increase of the static pressure, the discharge rhythm will show resting, on-off discharge, continuous uniform discharge, integer discharge, resting. Under the action of dynamic pressure, with the increase of average pressure, the discharge will go through resting, the peak discharge valley of the blood pressure peak does not discharge, continuous discharge, the peak of blood pressure does not discharge the value of the blood pressure Valley, and the resting course is consistent with the experiment.
5. analysis of the mathematical model, with the increase of static pressure, from resting to discharge to subcritical Hopf bifurcation, from continuous discharge to rest to resting is a supercritical Hopf bifurcation. The on-off discharge and the integer multiple discharge under static pressure are random rhythms induced by the noise at supercritical and subcritical Hopf points respectively. The activity of electrical activity under the action of pressure is caused by the pressure of blood pressure across the Hopf bifurcation point: the peak of blood pressure is at the resting and the value of the blood pressure Valley at the discharge. This explains the kinetic mechanism of these new rhythms.
The above results show that the change of blood pressure signal causes the change in the excitatory of the receptor, that is the dynamic change of the depolarization current. It makes the discharge rhythm of the baroreceptor in the static bifurcation structure of the discharge rhythm with depolarization current as a bifurcation parameter, and the time course of the mean blood pressure near the corresponding position according to the blood pressure signal. "Dynamic walk" forms a dynamic discharge rhythm, and the time history of the dynamic discharge rhythm corresponds well with the time dynamic process of the blood pressure signal. The theory of nonlinear dynamics bifurcation not only reveals the mechanism of the nerve discharge caused by the blood pressure signal, but also can be in the multiple layers including the discharge frequency. On the theoretical level, the relationship between ambulatory blood pressure signals and corresponding dynamic discharges is established to further understand the coding mechanism of receptors.

【学位授予单位】：陕西师范大学
【学位级别】：博士
【学位授予年份】：2010
【分类号】：R35

【参考文献】