Now, by far, the most important physiological factor that influences the resistance inside our blood vessel is the blood vessel diameter. And that's because the blood vessel length. And our viscosity of that blood under normal conditions does not actually change considerably. But because our autonomic nervous system innervates and controls the smooth muscle found inside the blood vessel, the diameter and the radius can easily be controlled by our body. And that's exactly why it's the diameter that actually influences the resistance of blood vessels the most in our body. So the next question is, what exactly is the relationship between the resistance and these three different factors that we mentioned just a moment ago?