Modulation of Respiratory System by Limb Muscle Afferents in Intact and Injured Spinal Cord

Figures

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  Figure 1. Schematic diagram of possible interactions between locomotor and respiratory systems. Brainstem respiratory network includes medulla and pons (see Section “Overview of Respiratory and Locomotor Networks”). Afferent inputs from limb muscles, joints and tendons are outlined by dashed line.

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  Figure 2. Simplified hypothetical diagram representing intraspinal connections between locomotor and respiratory spinal circuits. RMn – respiratory motoneuron. LMn – limb motoneuron. X? – shared interneuron that drives/modulates both RMn and LMn and receives afferent feedback from limb muscles. Possible direct inputs to RMn from limb muscle afferents are also shown.

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  Figure 3. Schematic diagram of cardio-respiratory interactions during exercise. Blue color represents afferent feedback from limb muscles. Red color shows afferent feedback from baro- and lung stretch receptors. NA – nucleus ambiguous; DMV – dorsal motor nucleus of vagus; PGNs – preganglionic neurons; Symp – sympathetic outputs; PSymp – parasympathetic output; X – vagus nerve. Open and filled big circles represent excitatory and inhibitory neuron populations, respectively. Filled small circles show inhibitory inputs, open small arrows indicate excitatory inputs. NTS was moved out from the block presenting brainstem respiratory network to show its inputs and outputs in greater details. Peripheral/central chemoreception was not included for simplicity.