r/Physiology

Sometimes when I get up and stretch/contract my torso I let out a guttural loud scream and it feels so good. Is there an evolution component to this?

I read that people generally breath in 21% oxygen air and breath out 16% oxygen air. If you kept recycling that air (like if you were breathing in and out of a paper bag) presumably the oxygen concentration would get lower and lower till you pass out or get brain damage or something bad.

If people fall asleep face to face cuddling, it is not sealed like a paper bag, but also not a well mixed environment. Presumably there is some sort of steady state percentage where oxygen used by person matches oxygen being mixed in from the fresh surrounding air. What is that steady state percentage?

Maybe some people end up breathing in as the other is breathing out as they sleep (and them breathing on eachothers faces significantly), and that is some sort of worst case. Why would that be worst case?

Person A breath out 16% and person B breathes in 16%
Then Person B breaths out 11% and Person A in 11% etc etc until dangerously low. Ik there is at least some mixing with the more oxygenated air. Idk how the percentage exchange would go.

I am using presumably pretty loosely. These assumptions are in question.

Also, do people have a reflex to move during sleep if they arent getting much oxygen?

There are many organ systems in the body, but it seems impractical to assess or optimize each one directly. I recently had my spine checked and it seemed to be MAJOR. But then each discipline would say that?

In practice, most health interventions seem to target global regulators like the autonomic nervous system or neurons. The hubs rather than spokes.

So my question: Is modern health optimization mostly about improving system-level regulation rather than organ-by-organ tuning?

Which systems give the highest “return on effort” for whole-body health? I don't think anyone can check each organ or even system, but spinal work seemed to be a big deal. Does each system impact the body THAT much?

I’ll get straight to the point.

I’m starting an MSc in Molecular Physiology this year and plan to pursue a PhD afterward.

To become a certified clinician in my hometown, I need a clinical PhD or a physiology program that involves human-based research not cell/lab work.

The challenge is that most university websites are vague, and supervisors rarely specify whether their research involves human subjects or cells, they typically only list their disease area or research interests.

Is there a reliable way to determine whether a university’s PhD program will issue a certificate specifically recognizing clinical studies?​​​​​​​​​​​​​​​​

I am from a tech background.

I have an interest in human physiology and philosophy but I don't know what to choose?

I am from a tech background. Idk what is the roadma

From Where I have to start.

Plz help me it's so confusing