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Figures
Neuromodulatory Pathways in the Stomatogastric Nervous System
Neuromodulatory Pathways in the Stomatogastric Nervous System
Neuromodulation can occur through direct or indirect pathways. My focus is on the labral sensory neurons which indirectly modulate the gastric mill rhythm through the decending neurons within the commisural ganglion (CoGs)
Interruption of the Gastric Mill Rhythm by the Labral Nerve
Interruption of the Gastric Mill Rhythm by the Labral Nerve
Electrical stimulation of the labral nerve interrupts the gastric mill rhythm (n=5). This appears to occur via inhibition of descending modulatory neurons (n=5).
Number of Cell Bodies Observed in Each Location
Number of Cell Bodies Observed in Each Location
The number of cells observed in each population varied between individuals except for locations B and D.
Dissection Methods
Dissection Methods
In order to trace the labral nerves, I dissected out the labrum and pinned it out as flat as possible. I then dyed it with Methylene Blue vital dye to label the axons and cell bodies. The green arrows in the figure indicate the labral nerves in each stage of dissection.
Sensory Neurons Found in the Crustacean Labrum
Sensory Neurons Found in the Crustacean Labrum
5 bilaterally symmetrical locations of neural cell bodies have been observed in the crab labrum extending from branches of the labral nerve. In the location noted as "b", two cell bodies were observed in only one individual and these have not been observed on the left side.
Swallowing Response Initiated from Physical Touch and Saline Application
Swallowing Response Initiated from Physical Touch and Saline Application
Resting Labrum
Resting Labrum
This is how the labrum sits above the esophagus in absence of stimulus in the live crab and in dead crabs. The arrow indicates where touch with forceps was applied to elicit the swallowing behavior.
Opened
Opened
After touching the labrum with forceps in the area indicated in the previous figure, the labrum retracts to uncover the esophagus and the esophagus opens. This also occurs when saline is applied to the labrum and mouth area.
Closed
Closed
Following the opening in the previous figure, the labrum moves past its resting position and further over the esophagus to cover the opening and the esophagus closes as well. This cycle repeats a few times following 1 stimulus application.
Video of swallowing response after touch stimulus.
Video of swallowing response after touch stimulus.
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