Peripheral chemoreceptors are located in the aorta and carotid arteries. The efferent fibres of the aortic body chemoreceptors are relayed by the vagus nerve. Central chemoreceptors in the medulla also recognize chemical variations in H. Larval stages have many kinds of sensory receptors, including light receptors and chemoreceptors. The carotid body chemoreceptors are also sensitive to pH and P, but only secondarily. PNECs may play a role with chemoreceptors in hypoxia detection. So, because of the central chemoreceptors, respiration rate would be increased. Sensitivity and physiology of the peripheral chemoreceptors changes throughout the lifespan. The decrease in [H+] suppresses the peripheral chemoreceptors, which are sensitive to pH. This is immediately sensed by the carbon dioxide chemoreceptors on the brain stem. Several studies suggest peripheral chemoreceptors play a role in ventilation during exercise. The role of the central chemoreceptors in the Cushing reflex is unclear. Particular chemoreceptors, called ASICs, detect the levels of carbon dioxide in the blood. The response to stimulation of chemoreceptors on the heart rate is complicated. Large numbers of chemoreceptors concentrate near its mouth.