• At rest and during exercise, the diameter of arteries and arterioles and the opening/closing of capillaries must be adjusted.
• Why? To keep the blood pressure steady and ensure the heart does its job right.

Did you know? 🤔
The walls of these blood vessels have smooth muscles that can either relax or contract. It's like a water hose – if it's too open, the water pressure will drop.

• If all the smooth muscle relaxed, blood pressure would drop too much, and the heart couldn't do its thing.
• The brain ensures there's a balance - some vessels relax while others contract. It's like choreographing a dance!

Real-world analogy 🌍: Think of a traffic control system. If all roads were open without control, there'd be chaos and crashes. Similarly, our body directs blood where it's needed most.

• Exercising muscles need more blood because they need more oxygen and nutrients.
• They also produce waste and heat which needs to be taken away.
• Result? More blood vessels in the muscles open up!

Real-world analogy 🌍: Imagine a big sale in one store in a mall. More people (or blood) would flock to that store, and mall security would direct foot traffic accordingly.

• When muscles hog the blood during exercise, other organs get less.
• BUT... essential organs like the brain and heart always get enough.
• Fun Fact: Muscles can demand up to 90% of total blood flow during exercise but only 20% at rest.

Real-world example 🌍: Picture a busy restaurant kitchen. The chef (your brain) ensures that VIP dishes (brain and heart) always get their ingredients on time, even if others have to wait a bit.