1 4 2 Rhythmicity BIO 361T Fall 2014 1 The graphs to the right show three unusual membrane properties Add labels to the figure that indicate what the top lines represent what the bottom lines represent and what deflections up and down represent Match each graph to the correct description a Involves voltage gated channels that depolarize the cell in response to a hyperpolarizing stimulus Ih postinhib rebound b From a pacemaker cell endogenous bursting c Involves voltage gated K channels that are fast IA plateau potentials Rhythmic behaviors due to pacemaker cells 2 Recall that normal respiratory rate is due to the endogenous rhythms of two pacemaker cells in the medulla the CS and the CI During gasping only the CI fires Bursts of action potentials from CI bursting are blocked by the drug riluzole CS bursting is blocked by the drug flufenamic acid FFA What combination of these drugs would you use to stop gasping What combination would inhibit normal breathing Gasping will be blocked by riluzole Riluzole and FFA together block normal breathing eupnea Rhythmic behaviors due to central pattern generators 3 Recall that the swim network in Tritonia contains CPG interneurons that activate each other but their activity must be initiated by sensory input Use the wiring diagram and graph below to answer the questions Bars in the graph correspond to 20 mV and 8 sec Note that there are two dorsal swim interneurons which are labeled DSI 1 and DSI 2 in the graph they are shown as one in the wiring diagram for simplicity 2 a b c Label which bar is 20 mV vertical and which is 8 sec horizontal Above the graph sketch in the activity you would expect if you recorded from one of the VSI neurons Should fire in gaps between DSI firings Below the graph draw a sequence of sea slugs exhibiting the behaviors that align with the electrophysiological recordings How many cycles did the swim motor program complete Dorsal upward when viewed from the side flexions when DSIs are firing ventral downward when VSIs are firing Six complete cycles of dorsal ventral flexions d Direct electrical stimulation of the DRI elicits the swim motor program What do these results demonstrate about the DRI It is sufficient to elicit swimming e Hyperpolarization of the DRI prevents the swim motor program from initiating even when Tritonia is given aversive stimuli that would normally elicit the swim motor program What do these results demonstrate about the DRI It is necessary to elicit swimming f What would be the most direct effect of hyperpolarizing the VFN No ventral flexion this is the motor efferent 4 Imagine you are standing calmly in a park on a smooth paved sidewalk Suddenly something frightens you and you take off running As your legs are pumping back and forth you leave the path and continue running over the uneven grass adjusting your gait and strides rapidly and unconsciously in response to the bumpy ground Use this scenario to fill in examples of the following concepts or components Sensory afferents neurons that detect the frightening stimulus from eyes ears etc Motor efferents to legs CPG interneurons in brain pons and medulla of brainstem Skeletal muscles in legs Sensory input frightening stimulus Motor output legs moving Reflex arc adjusting gait unconscious Rhythmic behavior running Modified motor output modified gait Complex physiological processes and behaviors often cannot be attributed to only neural circuits that are reflexes or only CPGs They often involve both reflex arcs and pattern generators especially for modulation
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