Hello @marcosmilano71,
Good day to you from my side of the world. It's a beautiful bright, sunny morning and the air is fresh, so I'm very happy.

You've asked some important questions.

Yes, our body's natural defenses do help with common functions such as yawning. However, the muscles in our face weaken as we grow older, and reduce the ability to provide some brain signals.
That's one of the reasons why the elderly might drool, have difficulty chewing their food, or even have trouble speaking.

Personally, the use of my face muscles is limited, which is not good. When I rotate my eyes, it pains. That's because the muscle is weak. Facial yoga (doing things like moving my eyes like a pendulum movement) which strengthens the muscles.

Starting facial yoga is difficult because of all the bad habits I have developed over the years.

I hope you'll gather more understanding in my follow up blogs:)

Wishing you a lovely day!