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Fig. 9 | The Journal of Physiological Sciences

Fig. 9

From: The respiratory control mechanisms in the brainstem and spinal cord: integrative views of the neuroanatomy and neurophysiology

Fig. 9

a Possible neuronal mechanism in which inhibitory spinal interneurons are involved in the rostrocaudal gradient of the inspiratory motor activity. The inspiratory depolarizing optical signals in the motoneuron and interneuron areas of the rostral thoracic segments are larger than those in the caudal thoracic segments (b, e) [101]. Many of the thoracic respiratory interneurons had an axon descending a few segments, which would be inhibitory [97, 100]. Based on these studies, it is possible that the inhibitory synaptic inputs to motoneurons gradually increase to reach the caudal segments (d). In order for the motoneurons to be activated during the inspiratory phase, it is necessary to receive excitatory synaptic inputs (c). Thus, in this model, the combination of inhibitory and excitatory synaptic inputs to motoneurons forms the rostrocaudal gradient of the thoracic inspiratory motor activity

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