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The Sympathetic Neural Control Of The Circulation At Rest And During Exercise: Effects Of Age, Biological Sex, And Sex Hormones, Andrew W. D'Souza
The Sympathetic Neural Control Of The Circulation At Rest And During Exercise: Effects Of Age, Biological Sex, And Sex Hormones, Andrew W. D'Souza
Electronic Thesis and Dissertation Repository
The overall objective of this dissertation was to determine the impact of age, sex, and sex hormones on the discharge behaviours of muscle sympathetic action potentials (APs) as well as the corresponding changes in peripheral vasoconstriction and blood pressure at rest and during exercise. The microneurographic technique was employed to record multi-unit muscle sympathetic nerve activity (MSNA), with a continuous wavelet transform applied post-hoc to evaluate APs within the recorded neurogram. Study One examined the impact of aging on the central and peripheral arcs of the sympathetic baroreflex under resting conditions. This study revealed that middle-aged-to-older adults demonstrated heightened sympathetic …
Heterogeneous Baroreflex Control Of Sympathetic Action Potential Subpopulations In Humans, Stephen A. Klassen, M. Erin Moir, Charlotte W. Usselman, J. Kevin Shoemaker
Heterogeneous Baroreflex Control Of Sympathetic Action Potential Subpopulations In Humans, Stephen A. Klassen, M. Erin Moir, Charlotte W. Usselman, J. Kevin Shoemaker
Bone and Joint Institute
© 2020 The Authors. The Journal of Physiology © 2020 The Physiological Society Key points: Emission patterns in muscle sympathetic nerve activity stem from differently sized action potential (AP) subpopulations that express varying discharge probabilities. The mechanisms governing these firing behaviours are unclear. This study investigated the hypothesis that the arterial baroreflex exerts varying control over the different AP subpopulations. During baseline, medium APs expressed the greatest baroreflex slopes, while small and large APs exhibited weaker slopes. On going from baseline to lower body negative pressure (LBNP; simulated orthostatic stress), baroreflex slopes for some clusters of medium APs expressed the …
Fifty Years Of Microneurography: Learning The Language Of The Peripheral Sympathetic Nervous System In Humans, J Kevin Shoemaker, Stephen A. Klassen, Mark B. Badrov, Paul J. Fadel
Fifty Years Of Microneurography: Learning The Language Of The Peripheral Sympathetic Nervous System In Humans, J Kevin Shoemaker, Stephen A. Klassen, Mark B. Badrov, Paul J. Fadel
Kinesiology Publications
As a primary component of homeostasis, the sympathetic nervous system enables rapid adjustments to stress through its ability to communicate messages among organs and cause targeted and graded end organ responses. Key in this communication model is the pattern of neural signals emanating from the central to peripheral components of the sympathetic nervous system. But what is the communication strategy employed in peripheral sympathetic nerve activity (SNA)? Can we develop and interpret the system of coding in SNA that improves our understanding of the neural control of the circulation? In 1968, Hagbarth and Vallbo (Hagbarth KE, Vallbo AB. Acta Physiol …
Ventilation Inhibits Sympathetic Action Potential Recruitment Even During Severe Chemoreflex Stress, Mark B. Badrov, Otto F. Barak, Tanja Mijacika, Leena N. Shoemaker, Lindsay J. Borrell, Mihajlo Lojpur, Ivan Drvis, Zeljko Dujic, J. Kevin Shoemaker
Ventilation Inhibits Sympathetic Action Potential Recruitment Even During Severe Chemoreflex Stress, Mark B. Badrov, Otto F. Barak, Tanja Mijacika, Leena N. Shoemaker, Lindsay J. Borrell, Mihajlo Lojpur, Ivan Drvis, Zeljko Dujic, J. Kevin Shoemaker
Bone and Joint Institute
© 2017 the American Physiological Society. This study investigated the influence of ventilation on sympathetic action potential (AP) discharge patterns during varying levels of high chemoreflex stress. In seven trained breath-hold divers (age 33 ± 12 yr), we measured muscle sympathetic nerve activity (MSNA) at baseline, during preparatory rebreathing (RBR), and during 1) functional residual capacity apnea (FRCApnea) and 2) continued RBR. Data from RBR were analyzed at matched (i.e., to FRCApnea) hemoglobin saturation (HbSat) levels (RBRMatched) or more severe levels (RBREnd). A third protocol compared alternating periods (30 s) of FRC and RBR (FRC-RBRALT). Subjects continued each protocol until …
Recruitment Strategies In Human Sympathetic Nerve Activity, Mark B. Badrov
Recruitment Strategies In Human Sympathetic Nerve Activity, Mark B. Badrov
Electronic Thesis and Dissertation Repository
The overall objectives of the current dissertation were to 1) establish the neural coding principles employed by the sympathetic nervous system (SNS) in response to acute physiological stress; and 2) to determine the various mechanisms of control underlying these sympathetic neural recruitment strategies. This research tested the working hypothesis that efferent post-ganglionic muscle sympathetic nerve activity exhibits neural coding patterns reflecting increased firing of lower-threshold axons, recruitment of latent sub-populations of higher-threshold axons, as well as malleable synaptic delays, and further, that these strategies are governed by factors such as reflex-specificity, stress severity, perception of effort or stress, age, and …
Methods And Considerations For The Analysis And Standardization Of Assessing Muscle Sympathetic Nerve Activity In Humans., Daniel W White, J Kevin Shoemaker, Peter B Raven
Methods And Considerations For The Analysis And Standardization Of Assessing Muscle Sympathetic Nerve Activity In Humans., Daniel W White, J Kevin Shoemaker, Peter B Raven
Kinesiology Publications
The technique of microneurography and the assessment of muscle sympathetic nerve activity (MSNA) are used in laboratories throughout the world. The variables used to describe MSNA, and the criteria by which these variables are quantified from the integrated neurogram, vary among studies and laboratories and, therefore, can become confusing to those starting to learn the technique. Therefore, the purpose of this educational review is to discuss guidelines and standards for the assessment of sympathetic nervous activity through the collection and analysis of MSNA. This review will reiterate common practices in the collection of MSNA, but will also introduce considerations for …
Methods And Considerations For The Analysis And Standardization Of Assessing Muscle Sympathetic Nerve Activity In Humans, Daniel W. White, J. Kevin Shoemaker, Peter B. Raven
Methods And Considerations For The Analysis And Standardization Of Assessing Muscle Sympathetic Nerve Activity In Humans, Daniel W. White, J. Kevin Shoemaker, Peter B. Raven
Bone and Joint Institute
© 2015 Elsevier B.V.. The technique of microneurography and the assessment of muscle sympathetic nerve activity (MSNA) are used in laboratories throughout the world. The variables used to describe MSNA, and the criteria by which these variables are quantified from the integrated neurogram, vary among studies and laboratories and, therefore, can become confusing to those starting to learn the technique. Therefore, the purpose of this educational review is to discuss guidelines and standards for the assessment of sympathetic nervous activity through the collection and analysis of MSNA. This review will reiterate common practices in the collection of MSNA, but will …
Sympathetic Neural Recruitment Strategies: Responses To Severe Chemoreflex And Baroreflex Stress, Mark B. Badrov, Charlotte W. Usselman, J Kevin Shoemaker
Sympathetic Neural Recruitment Strategies: Responses To Severe Chemoreflex And Baroreflex Stress, Mark B. Badrov, Charlotte W. Usselman, J Kevin Shoemaker
Kinesiology Publications
This study tested the hypothesis that neural coding patterns exist within the autonomic nervous system. We investigated sympathetic axonal recruitment strategies in humans during chemoreflex- and baroreflex-mediated sympathoexcitation using a novel action potential (AP) analysis technique. Muscle sympathetic nerve activity (microneurography) was collected in 11 young individuals (6 females) during baseline and two subsequent protocols: 1) severe chemoreflex stimulation (maximal end-inspiratory apnea following rebreathe), and 2) severe baroreceptor unloading (−80 mmHg lower body negative pressure; LBNP). When compared with each respective baseline, apnea and LBNP increased AP frequency and mean AP content per sympathetic burst (all P < 0.01). When APs were binned according to peak-to-peak amplitude (i.e., into “clusters”), total clusters detected increased during both apnea (Δ7 ± 5; P …
Sex Hormones And Sympathetic Nerve Activity, Charlotte W. Usselman
Sex Hormones And Sympathetic Nerve Activity, Charlotte W. Usselman
Electronic Thesis and Dissertation Repository
The purpose of this thesis was to test the hypothesis that changes in circulating sex hormone levels are associated with changes in muscle sympathetic nerve activity. The hypothesis was tested through the comparison of low- (early follicular [EF]) and high-hormone (midluteal [ML]) phases of the menstrual cycle and of hormonal contraceptive use (low hormone [LH] versus high hormone [HH]). The microneurography technique was used to compare both the frequency and size of bursts in muscle sympathetic nerve activity (MSNA) at baseline and during two sympatho-excitatory maneuvers: baroreceptor unloading elicited through lower body negative pressure, and chemoreflex stimulation elicited through a …
Representation Of Somatosensory Afferents In The Cortical Autonomic Network, Ruma Goswami
Representation Of Somatosensory Afferents In The Cortical Autonomic Network, Ruma Goswami
Electronic Thesis and Dissertation Repository
The relationship between somatosensory stimulation and the autonomic nervous system has been established with effects on heart rate (HR) and sympathetic tone. However, the involvement of the cortical autonomic network (CAN) during muscle sensory afferent stimulation has not been identified. The main objective of the research in this dissertation was to determine the representation of somatosensory afferents in the CAN and their physiologic impact on cardiovascular control. Somatosensory afferent activation was elicited by electrical stimulation of type I and II afferents (sub-motor threshold) and type III and IV afferents (motor threshold), and CAN patterns were assessed using blood-oxygenation level-dependent functional …