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Neuromuscular Physiology
Published in Michael H. Stone, Timothy J. Suchomel, W. Guy Hornsby, John P. Wagle, Aaron J. Cunanan, Strength and Conditioning in Sports, 2023
Michael H. Stone, Timothy J. Suchomel, W. Guy Hornsby, John P. Wagle, Aaron J. Cunanan
Action potential propagation requires that a RMP threshold must be reached; typically this requires a positive increase of 10 to 15 mV in the RMP. In neurons, alterations in the RMP are initiated by increased Na+ permeability; however, if the influx of Na+ is small and the threshold value is not reached, no AP will occur. Physiologically, the threshold value can be reached by several mechanisms. For example, through temporal summation in which an increased frequency of impulses arrives from the same neuron (or a few), by spatial summation when a large number of separate neurons excite the effector cell simultaneously or both temporal and spatial summation.
Is Fibromyalgia a Central Pain State?
Published in Robert M. Bennett, The Clinical Neurobiology of Fibromyalgia and Myofascial Pain, 2020
Temporal summation means a progressive increase in action potential discharge from nociceptive nerve cells in the dorsal horn in response to repetitive stimulation by identical stimuli [windup]. Staud et al. recently published a study of 59 FMS patients and 65 normal controls, where the response to repetitive thermal stimulation was recorded (6). The stimuli were of equal intensity. The amount of temporal summation was greater in FMS patients than in controls. Staud et al. discuss both peripheral and central mechanisms as causes of the increased temporal summation.
The cell
Published in Laurie K. McCorry, Martin M. Zdanowicz, Cynthia Y. Gonnella, Essentials of Human Physiology and Pathophysiology for Pharmacy and Allied Health, 2019
Laurie K. McCorry, Martin M. Zdanowicz, Cynthia Y. Gonnella
Temporal summation occurs when multiple EPSPs (or IPSPs) produced by a single presynaptic neuron in close sequence exert their effect on the membrane potential of the postsynaptic neuron. For example, an action potential in the presynaptic neuron produces an EPSP and partial depolarization of the postsynaptic neuron (see Figure 1.9). While the postsynaptic neuron is still depolarized, a second action potential in the presynaptic neuron produces another EPSP in the postsynaptic neuron that adds to the first EPSP and further depolarizes this neuron. As more and more EPSPs add together, the membrane depolarizes closer and closer toward threshold until an action potential is generated. Although temporal summation is illustrated in Figure 1.8 with the summation of relatively few EPSPs, the addition of up to 50 EPSPs may be necessary to reach threshold. Because a presynaptic neuron may generate up to 500 action potentials per second, temporal summation occurs quite readily. The strength of the signal to the postsynaptic neuron is, therefore, influenced by the frequency of nerve impulses generated by the presynaptic neuron.
Questionnaire-based somatosensory profiling in breast cancer survivors: are we there yet? Associations between questionnaires and quantitative sensory testing
Published in Disability and Rehabilitation, 2023
Lore Dams, Elien Van der Gucht, Vincent Haenen, Nele Devoogdt, Ann Smeets, Bart Morlion, Koen Bernar, Tessa De Vrieze, Niamh Moloney, An De Groef, Mira Meeus
Advanced QST protocols may provide insight into an individual’s central somatosensory processing. First, conditioned pain modulation (CPM) explores the physiological phenomenon that noxious stimuli exert inhibitory effects over subsequent noxious stimuli (diffuse noxious inhibitory control) and is, as such, a way of evaluating the anti-nociceptive or inhibitory activity of the central nervous system [18,19]. Second, temporal summation (TS) is related to "wind-up" of repeated nociceptive input to the central nervous system, in which the neuronal output increases with successive stimuli [20]. When somatosensory processing is altered, wind-up is exaggerated in amplitude and duration [21]. Besides CPM and TS protocols, assessing pain thresholds at an area distant from the breast surgery may also provide more information on the extra segmental spreading of sensitization. In the case of altered central somatosensory processing, increased sensitivity often extends beyond the innervation area of a peripheral nerve [20,22]. Altered central somatosensory processing has already been identified in breast cancer survivors with persistent pain [13,14,23].
Pro-nociceptive pain modulation profile in patients with acute and chronic shoulder pain: a hypothesis-generating topical review
Published in Physical Therapy Reviews, 2021
Rani Othman, Nicola Swain, Steve Tumilty, Prasath Jayakaran, Ramakrishnan Mani
Conditioned pain modulation (CPM) is a commonly used protocol to measure descending control mechanisms in humans [80]. CPM is believed to represent the human behaviour correlate of diffuse noxious inhibitory controls mechanism. In contrast, temporal summation (TS) reflects the wind-up process within the dorsal horn wide-dynamic range neuron [31, 72, 81]. Further, MEP is a form of sensitivity testing and it might link to QST outcomes [82, 83]. MEP paradigms such as sensitivity to physical activity can be used in addition to QST measure, which assesses natural pain reactions in response to repeated functional movement [82, 83]. Outcomes of such testing protocols (i.e. QST, MEP, and CSI) can provide insights into the mechanisms behind persistent pain experience. They can be a useful clinical tool in which it can predict future pain [79, 84, 85].
Timing matters: the interval between acute stressors within chronic mild stress modifies behavioral and physiologic stress responses in male rats
Published in Stress, 2018
Sonia A. Cavigelli, Alexander D. Bao, Rebecca A. Bourne, Michael J. Caruso, Jasmine I. Caulfield, Mary Chen, Joshua M. Smyth
We tested three hypotheses: (i) the temporal summation hypothesis, (ii) the anticipatory hypothesis, and (iii) the null hypothesis. The temporal summation hypothesis proposes that health consequences are more extensive when daily acute stressors occur in rapid succession as opposed to spread out over the day. This is based on the assumption that biologic responses to temporally clustered acute stressors summate over time if there is not enough time between stressors to allow for return to basal activity. If supported, we expected that rats exposed to daily stressors in rapid succession (“Clustered”) would show the greatest evidence of slowed growth, dampened hedonic behavior, glucocorticoid dysregulation (slower daily decline, dampened acute response, and/or slower recovery following acute stressor), and increased inflammatory responses compared to Control rats. The anticipatory hypothesis proposes that health consequences are worse when daily stressors are dispersed across the day because the organism must maintain elevated physiologic preparedness throughout the day. If this hypothesis is accurate, we expected that rats exposed to daily acute stressors throughout the day (“Dispersed”) would show the greatest evidence of slowed growth, decreased hedonic behavior, greater glucocorticoid dysregulation, and increased peripheral inflammatory responses. Under the null hypothesis, the temporal pattern of acute stressors within chronic stress is of no consequence, and both forms of chronic stress (“Clustered” versus “Dispersed”) will lead to similar outcomes.