Feedback loops suck.
The podcasts are meandering through the maze of the endocrine system and that involves learning about feedback loops
You got your positive and you negative for starters, but what the heck does that mean?
Well, let me tell you.
You already know about feedback.
Feedback is simple. Everyone else makes this so damn complicated. I think they like to show off how smart they are or hide how smart they aren’t by making you feel dumb.
Circulating Nurse: “Doc what suture would you like next.”
Surgeon angrily and with disdain, “The same suture I’ve been using for twenty years.” Inferring that it should be on the preference card, and the stupid nurse should just do her job.
Me, “You have no idea what you need do you?”
Surgeon with a wry smile, “No idea.”
If we make other people look dumb, then we look better right?
How about we just make it easy?
Feedback is just feedback. It means when you do something, you get information back about that thing you did.
I create a podcast. You leave a review on iTunes. That’s feedback for me. I can use that feedback to either stop what I’m doing or do more of what I’ve been doing.
Negative feedback might get me to do less of something.
Positive feedback might get me to do more of something.
Somebody leaves an iTunes review “These are the best podcasts ever. I’ve learned so much. I owe Brian at least my first month’s salary.”
That might get me to do more podcasts = positive feedback.
Someone else might leave an iTunes review, “This podcast stinks. All Brian does is talk about his kids. He can’t pronounce anything, and the music is terrible.”
This might get me to do fewer podcasts = negative feedback.
Simple so far, right?
Now it gets a little more complicated: a feedback loop.
In a feedback loop, the first thing, let’s call that Thing A, causes the second thing, Thing B. Thing B now loops back and affects Thing A either positively or negatively.
In a positive feedback loop, Thing A would cause thing B, and thing B would cause more of thing A, which would cause more of thing B, which would cause more of thing A, etc…… You can see how this would really ramp up the action.
In a negative feedback loop, Thing A would cause thing B and thing B would inhibit thing A, slowing the whole process down.
Of course, the endocrine system is a little more complicated. Instead of only two steps, there are often more. This allows for regulation at any one step to influence the whole loop.
Things A is stress.
Thing B is the hypothalamus which secretes corticotropin-releasing factor (CRF)
Thing C is the pituitary which secretes adrenocorticotropic hormone (ACTH)
Thing D is the adrenal glands which secrete cortisol.
You get stressed about a test as you walk in the door. You start to get nervous. (Thing A) The hypothalamus kicks in and starts secreting CRF in response to the stress (Thing B). The pituitary sees the CRF and starts creating ACTH in response. (That was thing C). The adrenal glands see all this ACTH and start cranking out cortisol. (That was thing D). Now your bloodstream is flooded with cortisol. That increases available energy by raising blood sugar and encouraging the breakdown of stored fats and proteins.
Now the hypothalamus (thing A) notices these high levels of cortisol in the blood and says “Oh, maybe that’s enough,” so it slows production of CRF. That slows production of ACTH which slows production of Cortisol.
Negative feedback loop. In this case thing, Thing D inhibits Thing A and puts the brakes on.
One last example…
You read this month’s issue of Physician Assistant Exam Scholars. You are a veritable giant of confidence on your rotations. Subsequently, several people start talking to you about a job when you graduate.
You’re so excited that you tear into the following month’s issue (it’s already all planed out) and instead of just talking about a job you figure out exactly how to land the job of your dreams. I mean holy smokes. Of course, you want to keep reading.
The following month you’re dripping with excitement as the mail comes….
That sounds like a positive feedback loop to me.
See you there.
Physician Assistant Exam Scholars
Brian Wallace
