<s>[INST] context: - Located in each side of medulla, about 5mm anterior & lateral to dorsal respiratory group of neurons is ventral respiratory group of neurons, found in nucleus ambigus rostrally & nucleus retroambigus caudally. - Neurons of VRG remain almost totally inactive during normal quiet respiration. so, normal quiet breathing is caused only by repetitive inspiratory signals from DRG transmitted mainly to diaphragm & expiration results from elastic recoil of lungs & thoracic cage. - When respiratory drive for increased pulmonary ventilation becomes greater than normal, respiratory signals spill over into VRG from basic oscillating mechanism of DRG - As a consequence, VRG contributes extra respiratory drive as well - Electrical stimulation of few of neurons in VRG cause inspiration & others cause expiration, thus these neurons contribute to both inspiration & expiration. - They are especially impoant in providing powerful expiratory signals to abdominal muscles during very heavy expiration. Pneumotaxic center: Primary effect is to control "switch off" point of inspiratory ramp, thus controlling duration of filling phase of lung cycle. - Main function is to limit inspiration which has secondary effect of increasing rate of breathing because limitation of inspiration also shoens expiration & entire period of each respiration Chemoreceptors: - Sensors that detect changes in Co2, O2, pH. - Based on anatomical position divided into Central chemoreceptors Peripheral chemoreceptors [/INST] question: In forceful expiration, which of the following neurons gets fired? | options: A: VRG B: DRG C: Pneumotaxic centre D: Chemoreceptors | answer: A </s>