Heart Rate Nerve cells monitor blood for changes. If there's too much Carbon Dioxide (CO) and not enough
Oxygen (O), the oxygen sensing nerve cells send a signal to the brain. The brain sends a signal
to the pacemaker cells in the heart, which makes the heart beats faster, pushing more blood

Find the stimulus and control center effector and receptor
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Nerves are problay the number 1 thing in the body

It depends on the surface of the levels. the rougher the surface, the greater is the frictional force. for rougher surfaces, you would need to exert greater force to move the object. the concept is that, you must overcome the frictional force in order to bring the object into motion. this is the reason why we add lubricants to the joints so they could easily move. this answer was on

Other organisms can change their behavior to take the place of the plants in the ecosystem.