Bacteria!

random cool fact: our bodies contain more bacterial cells than human cells! we have trillions of healthy (and essential) bacteria in our digestive tracts that help us break down and absorb our food. surrounded by lots of anti-bacterial sentiment (anti-bacterial soap, bleach, pasteurized foods, purell) lets also appreciate the vital importance of the bacteria that live in symbiosis with (and outnumber) our human cells.

Breath

it feels appropriate that the first post of this blog be about breath. most of us take it for granted that we inhale and exhale 24 hours a day for our entire lives, though we do quickly recognize its importance as soon as we feel unable to breathe. both of my moms have a particular appreciation for breath: all of my elementary school friends grew accustomed to taking a breath together anytime barbra came in to lead an activity in the classroom and i have memories of terese, the yogi, teaching my sister and i how to take deeps breaths "down into our feet" to relax before bed. now i have spent the last two weeks immersed in learning about the respiratory system. i am in awe of how smart are bodies are to be able to regulate our breathing in response to whatever we are doing.

i like to think about lungs as big balloons with billions of tiny balloons inside, called alveoli. with all the alveoli together, the lung looks (and feels) a bit like a sponge. note on spongy appearance on the microscopic slide below (the spaces are the alveoli).

when we inhale, we contract our diaphragm (the dome shaped muscle seen at the bottom of the graphic image that separates our bellies from our chests).  when the diaphragm contracts, it pushes all of our abdominal organs down to make space in our chest cavity to draw air in like a vacuum.  the alveoli stretch and inflate with air to exchange oxygen and carbon dioxide with blood vessels that surround all the alveoli. we use muscles that require energy to inhale but a healthy relaxed exhale requires no work. it is simply a matter of relaxing the diaphragm and allowing the elastic alveoli to recoil, like releasing an inflated balloon.

normal lung tissue at 25X magnification

the cooperative task of the heart and the lungs is to deliver oxygen and remove carbon dioxide from all of the cells in the body. the oxygen is needed to make energy to power whatever the cell's job is and the carbon dioxide is produced during this process. the cell uses the oxygen and releases carbon dioxide back into the blood to be brought to the lungs for exhale out of the body. for our bodies to function well, it is critical to maintain certain levels of oxygen and carbon dioxide in the blood at all times.

what makes our bodies decide when to breathe fast or slow, deep or shallow? the primary regulator of our breathing is not oxygen concentration but the level of carbon dioxide in our blood. for example, when you try to hold your breath under water, after awhile you can't hold it any longer and you have to inhale. this urge to breathe is not your body saying "i need more oxygen" but instead "there is too much carbon dioxide, let it out!" this close regulation is because carbon dioxide makes the fluid in the body more acidic. all of our enzymes can only function properly in a very small range of acidity so it is important to maintain a fairly constant concentration of carbon dioxide in our blood. when carbon dioxide builds up and makes the blood slightly more acidic (this happens in a matter of seconds), receptors notice this change and send signals through our nerves telling our diaphragm to take more frequent and deeper breaths so that we exhale more carbon dioxide out. (there are also other receptors that signal us to breathe based on the amount of oxygen in our blood, but these only kick in when out oxygen levels get dangerously low). I find this close regulation fascinating! You can feel this regulation in your own body in just a couple of minutes (i have done this several times this week and think it is really cool!):

1. while comfortably sitting down, notice your easy, relaxed breathing.

2. start hyperventilating: take many fast shallow breaths to try to get a lot of carbon dioxide out of your body. do this for about 20 seconds (really, breathe fast, but, as always, listen to your body - if you start to feel at all light headed, stop. no passing out in this self-learning exercise).

3. stop hyperventilating and relax. notice that your breathing slows way down and you don't feel like taking many breaths. this is because there is a low level of carbon dioxide in your blood so your body slows down your breathing rate until the carbon dioxide builds back up to its normal level. Sit there for about a minute until you feel your breathing rate resume to normal.

4.  now hold your breath for as long as you can. during this time, your cells are releasing carbon dioxide into your blood but you are not exhaling it so it is getting more concentrated. when you can't hold it any longer, take a breath. notice your breathing now. you are likely taking deeper, more frequent breaths to let the excess carbon dioxide out until the acidity of your blood resumes to normal.

*practical conclusion of this exercise: if you want to win a breath-holding contest, hyperventilate right before.