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← Theoretical B

Q49 — CCHa1, Enteroendocrine Cells, and Sleep Arousal in Drosophila

Theoretical B Real exam question — full text reproduced under IBO's CC BY-NC-SA 4.0 license
Nervous System Physiology

In fruit flies, dietary content affects arousal to mechanical vibrations during sleep, a process mediated by enteroendocrine cells in the gut (Figure 1).

Five-panel figure: panel A is a schematic of enteroendocrine (EE) cells secreting CCHa1 into circulation, which binds a CCHa1 receptor on a DA neuron that synapses onto an MBON neuron via dopamine; panel B is a bar chart of CCHa1 mRNA level under four diets (regular food, +sugar, +fat, +protein); panel C is a bar chart of percent flies awoken by stimulation, comparing control to CCHa1-depleted flies; panel D is a bar chart comparing arousal in control versus shi-ts mutant flies; panel E is a bar chart comparing arousal in control versus flies overexpressing TrpA1 in MBON neurons. Figure 1. A The interaction scheme between enteroendocrine (EE) cells (secreting CCHa1) and the central nervous system. B The effect of dietary content on CCHa1 expression (Y-1: CCHa1 mRNA level in the gut; A: regular food, B: +sugar [14 kcal], C: +fat [80 kcal], D: +protein [40 kcal]). C The effect of CCHa1 depletion on arousal during sleep (Y-2: % flies awoken by stimulation). D The impact of the shi-ts mutation (defective endocytosis/exocytosis in the DA neuron) on arousal during sleep. E The impact of overexpressing TrpA1 (a cation channel transporting Na⁺ and Ca²⁺) in MBON neurons on arousal during sleep; Na⁺ and Ca²⁺ concentrations are lower inside the neuron than outside.

On your answer sheet, indicate “T” for true statements and “F” for false ones.

A. CCHa1 expression depends on the caloric content of the consumed food.
B. Results suggest that a protein-rich diet reduces sleep arousal.
C. CCHa1 should result in the excitation of DA neurons to prevent arousal during sleep.
D. The synapse between DA and MBON neurons should be inhibitory to prevent arousal during sleep.
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Question reproduced from IBO 2024, Theoretical Exam Part B, licensed under CC BY-NC-SA 4.0 — attributed to the International Biology Olympiad. Open the full exam PDF