What are the two main gasses in the atmosphere?

In what for do plants utilize nitrogen? why do they need nitrogen?

Baroreceptors in the aortic arch and carotid bodies are mechanoreceptors that respond to the stretch that occurs in these arterial walls with changes in blood pressure. if pressure changes rapidly, the baroreceptors initiate a feedback mechanism that reduces blood pressure; however, if pressure changes slowly, as in developing hypertension, the receptors do not respond. given this information, the baroreceptors are most likely which type of receptor?

Which best describes the chemical reaction taking place?