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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 dorsal respiratory group, which is located near the nucleus tractus solitarius where afferents of the glossopharyngeal (IX) and vagus (Xt) nerves terminate. It consists of mainly inspiratory neurons that control the diaphragm and are responsible for normal tidal inspiration. The dorsal group is mainly concerned with timing of respiratory cycle.
Brainstem and Spinal Control of Respiratory Muscles During Breathing
Published in Alan D. Miller, Armand L. Bianchi, Beverly P. Bishop, Neural Control of the Respiratory Muscles, 2019
The medullary respiratory neurons sending axons down to the spinal cord, i.e., the bulbospinal neurons,7 are concentrated in the vicinity of the solitary tract (referred to as the dorsal respiratory group, DRG), and in the ventrolateral column extending from the nucleus retroambigualis to the retrofacial nucleus (referred to as the ventral respiratory group, VRG). Inspiratory bulbospinal neurons belong to both DRG and VRG whereas expiratory bulbospinal neurons are located either in the caudal part or in the most rostral parts of the VRG. This rostral group is functionally defined as the Bötzinger complex (BötC). The main properties of these neurons are reported in other chapters.
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
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).