Biology · C Interaction and interdependence. The idea in plain words, the rules to remember, the mistake to avoid and a worked example, written and checked by Mega Lecture.
The body is organized in levels: cells, tissues, organs and organ systems. These parts must work together, and this needs communication. There are two ways to send signals.
Nervous signals are electrical impulses along neurons. They are fast, short-lived and go to a precise target. Hormonal signals are chemicals carried in the blood. They are slower, last longer and reach every cell, but only cells with the right receptor respond.
Many body variables are kept steady by negative feedback: a receptor detects a change, a control centre sends a signal, and an effector reverses the change.
Students say that a low oxygen level is what mainly drives faster breathing. The main signal is the rise in carbon dioxide, which lowers the pH of the blood.
Answer: The medulla lowers the heart rate, which brings the blood pressure back down.
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