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Control of Ventilation
Published in Peter Kam, Ian Power, Michael J. Cousins, Philip J. Siddal, Principles of Physiology for the Anaesthetist, 2020
Peter Kam, Ian Power, Michael J. Cousins, Philip J. Siddal
The ventral respiratory group, which contains both inspiratory and expiratory neurons, is mainly associated with intercostal muscle control during expiration. The ventral respiratory group consists of a column of cells which includes the nucleus ambiguous (involved in larynx and pharyngeal dilation), nucleus retroambigualis (expiratory muscle control), the Botzinger, nucleus paraambigualis (control of inspiratory muscle contraction force), Botzinger complex (expiration) and the pre-Botzinger complex (respiratory pacemaker activity described above). The ventral respiratory group neurons, excluding the pre-Botzinger complex, are inactive during quiet breathing until active expiration is required in exercise.
Organization of Central Respiratory Neurons
Published in Alan D. Miller, Armand L. Bianchi, Beverly P. Bishop, Neural Control of the Respiratory Muscles, 2019
Armand L. Bianchi, Rosario Pásaro
Respiratory neurons within the brainstem are located in two well-circumscribed regions, i.e., a dorsal respiratory group (DRG) located in the ventrolateral subnucleus of the NTS, and a ventral respiratory group (VRG) which corresponds to a longitudinal column of neurons extending from the cervical spinal cord (CI level) to the facial nucleus in a region including the nucleus ambiguus. The DRG is mainly composed of inspiratory bulbospinal neurons whereas the VRG is more heterogenous, and composed of various classes of respiratory neurons. The respiratory neurons exhibit various patterns of activity depending on their intrinsic membrane properties, and on the timing of the excitatory and inhibitory influences they receive throughout the respiratory cycle. These influences, which result from interconnections among respiratory neurons, provide the respiratory motor output to the cranial and spinal motoneurons to insure production of respiratory movements and control of the air flow. However, the origin of the respiratory rhythm remains speculative because we do not know precisely all the possible synaptic interactions among respiratory neurons within the network, and how these modulate their intrinsic membrane properties.
The respiratory system
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
Aggregates of cell bodies within the medulla of the brainstem comprise the medullary respiratory center. There are two distinct functional areas: Dorsal respiratory groupVentral respiratory group
Diaphragmatic recovery in rats with cervical spinal cord injury induced by a theophylline nanoconjugate: Challenges for clinical use
Published in The Journal of Spinal Cord Medicine, 2019
Fangchao Liu, Yanhua Zhang, Janelle Schafer, Guangzhao Mao, Harry G. Goshgarian
Based on the demonstration of transsynaptic transport of WGA-HRP in the phrenic motor system following a C2Hx,14 WGA-HRP was utilized to target drug delivery to the motoneurons of the phrenic nucleus (PN) and the pre-motor rostral ventral respiratory group (rVRG) neurons involved in diaphragm function. It was demonstrated that the WGA-HRP was retrogradely transported to the PN and then to the rVRG over the CPP.14 To bind theophylline (or potentially any drug or molecule of choice) to WGA-HRP, a coupler (or carrier) was needed to facilitate the chemical conjugation. In vivo application of gold nanoparticles (AuNPs) has been established in the literature and are known for their biocompatibility, low toxicity, and easy attachment of various structures via chemical bonds to the AuNPs.15–24 Following injection into the left hemidiaphragm (LHD, paralyzed by the C2 hemisection), the synthesized tripartite nanoconjugate, comprised of WGA-HRP chemically conjugated to AuNPs which in turn is chemically conjugated to theophylline, undergoes WGA-HRP-receptor-mediated endocytosis. Once endocytosed the nanoconjugate is transported in a retrograde manner to the PN in the spinal cord followed by retrograde transsynaptic transport to the rVRGs in the medulla.25 The ester bond linking the AuNP to theophylline is biodegradable, designed to release theophylline following endocytosis.25 The expected result is the recovery of the hemidiaphragm previously paralyzed by the C2Hx.
Spinal cord injury and diaphragm neuromotor control
Published in Expert Review of Respiratory Medicine, 2020
Matthew J. Fogarty, Gary C. Sieck
The neuromotor circuitry involved in the activation of the diaphragm muscle during ventilatory behaviors has been very well described (Figure 2). These previous studies reflect an intense focus on the ventilatory central pattern generator in the PreBötzinger complex, which represent the spontaneously active ‘kernel’ of neurons for the metronomic drive for inspiratory activation of the diaphragm [2,48]. The location of inspiratory premotor neurons in the ventrolateral medulla (ventral respiratory group) and dorsomedial medulla (dorsal respiratory group) has been well documented. These medullary premotor neurons provide a predominantly ipsilateral monosynaptic drive to phrenic motor neurons during inspiration (Figure 3) [49–55]. If this descending bulbospinal presynaptic input is uniformly distributed, the recruitment of phrenic motor neurons would solely depend on intrinsic, size-dependent electrophysiological properties of motor neurons (i.e., the Size Principle). However, in a recent study, we found that glutamatergic presynaptic terminal density is higher on smaller phrenic motor neurons [37], that likely innervate type S and FR motor units that are involved in ventilatory behaviors. Similarly, we recently reported that expression of glutamatergic NMDA and AMPA receptors depends on phrenic motor neuron size with smaller motor neurons having a greater density of NMDA and AMPA receptor mRNA transcripts compared to larger motor neurons [56]. Thus, in addition to intrinsic motor neuron properties, the recruitment of fatigue resistant type S and FR motor units is guaranteed by the differential distribution of excitatory bulbospinal glutamatergic drive to smaller phrenic motor neurons (Figure 3).
Intranasal trigeminal function in chronic rhinosinusitis: a review
Published in Expert Review of Clinical Immunology, 2023
Anna Kristina Hernandez, Thomas Hummel
Only one study in our review directly investigated the relationship of inflammation with trigeminal function. Zhang et al. found that tissue eosinophil count was correlated with tERP N1 and P2 peak latencies, but not amplitudes, for ethyl alcohol as a stimulus [24]. Also, in the same study, they found a correlation between tERP latency and sneezing visual analogue scale (VAS) ratings, where worse ratings corresponded to longer latencies (Kendall’s tau-b=−0.40, p = 0.005). However, since Kendall’s tau was the analysis used, the quantitative effect this corresponds to is uncertain, as this analysis only gives an ordinal association between the two variables. Sneezing was found to be mediated by TRPV1 in mice [65]. TRPV1+ nasal neurons were found to selectively express neuromedin B, a peptide that activates neuromedin B receptor + (NMBR+) neurons in the area of the brainstem related to sneezing. These NMBR+ neurons were found to synapse with the caudal ventral respiratory group to induce sneezing when prompted by chemical irritants or allergens [65]. Interestingly, however, trigeminal function appears to be preserved, or even better, in allergic rhinitis (AR) patients [23,25,66]. Trigeminal CO2 thresholds (t63 = 2.69; p < 0.05) were lower. Responses to a nasal mucosal signal (negative mucosal potential, NMP) had shorter latencies (N1: t57 = 2.20, p < 0.05; P2: t57 = 2.30, p < 0.05) and tERP P1 (t26 = 2.12, p < 0.05), N1 (t26 = 2.12, p < 0.05), and P2 (t26 = 2.08, p < 0.05) peak latencies were also significantly shorter in patients with AR [25]. Trigeminal lateralization was also found to be significantly better in patients with AR compared to CRS (p = 0.002), but the difference between scores of AR patients and healthy controls remained non-significant [23]. On the other hand, patients with asthma were found to have lower pre-operative scores on chemosensory function tests than patients without asthma (p < 0.005), but having asthma did not influence the effect of surgery on post-operative chemosensory function [19].