Plants need nitrogen in order to grow. Nitrogen is abundant in the earth's atmosphere, but plants cannot use it in that particular form (nitrogen gas). Certain bacteria which reside on some plant roots are able to change atmospheric nitrogen into a form that plants can use (ammonia).
Answer:
Negative feedback loop
Explanation:
The feedback loop that would allow the blood pressure to go back down to normal would be a negative feedback loop. This type of loop basically causes the body to decrease the effects that are currently taking place while at the same time implementing the opposite effects in order for the system to stabilize itself once again. This can be seen in the depiction below where an effect takes place in the body (positive feedback loop) and the negative feedback loop kicks into re-stabilize the body's system.