system
Given the following post, respond as if you're commenting on Reddit:
human
How do certain senses inside our bodies measure certain parameters? For instance, how do cells measure our blood pressure, or body warmth?

Recently, in biology class, we came across the subject of nerves, and all things related. There was stated that our body can measure certain parameters for instance our osmotic values or our blood pressure. I was wondering how our cells could measure this.
gpt
Our bodies have sensor cells located in very strategic places.  Lets take, for example, blood pressure.  The baroreceptor cells, located in the aortic arch and carotid arteries of the neck, provide a signal to the brain telling it to slow the heart down (a negative-feedback loop).  As blood pressure increases, the baroreceptor cells get physically stretch, or distended, and are thus more and more stimulated - sending more signal to the brain, which in turn, tells the heart to beat less frequently and drops the blood pressure.  

It gets a little more complicated when we look into the sympathetic outflow inhibition of norepinephrine, which through another mechanism, can relax blood vessels dropping systemic pressure. 

These baroreceptor cells are based off of relative distention, so it's not really absolute values that determine the signal outflow.  

An interesting note; Patients with Chronic Obstructive Pulmonary Disease (COPD) or emphysemia have an interesting situation when it comes to their oxygen sensing cells.  As a patient develops COPD, the oxygen that gets into their blood stream diminishes over time due to decreasing efficiency of their lungs.  Their body becomes accustomed to this drop of oxygen saturation and sets a new 'normal' lower than before.  So in this new 'normal state', oxygen levels have to be pretty low for their body to say "Take a breath" again.  Now, if a poorly trained EMT decides to put this patient on pure 100% oxygen, their blood is now much more saturated with O2.  Their body senses this abundance of oxygen way above their 'normal level' and thinks, "Hey, we have so much oxygen, we don't even need to take a breath now", so this patient, if not actively taking breaths, will stop breathing!

Hope this helps/is interesting.