01.09 Homeostasis

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Included In This Lesson



  1. Homeostasis- Life maintaining balance in both chemical and physical conditions
    1. Adaptive response- refers to changes in brain/cell activity to maintain homeostasis
      1. Positive feedback- stimulus enhances/increases the condition (less common)
        1. examples: Blood clotting, childbirth, breastfeeding
      2. Negative Feedback- stimulus reduces or shuts off the condition (more common type of feedback)
        1. examples osmoregulation, blood pH, thermoregulation, Blood sugar, Blodd calcium
    2. Like an adaptive response in cells = cellular dysfunction (aka disease)


Today is are all about maintaining a balance in life….aka homeostasis!

SO we will start by breaking down the word, homeo meaning same and stasis means keeping the same status. And whether we are thinking about it or not, or body, our cells are working very hard to keep things balanced.  And its not like it can find a balance and chill out. We are always changing…. As energy flows in and out of us matter is cycling and creating change and our cells must observe these changes and adjust when needed. That adjustment is referred to as a response and it had better happen! So change must occur (no energy entering our cells they die) and we must respond to those changes accordingly.

So changes in and around are cells are dealt with through feedback mechanisms. A stimulus makes a cell or an organ aware of a change and the control center then generates an appropriate response. There are 2 type of feedback mechanisms…. one in which the response to a stimulus increases the original state. Like in childbirth or blood clotting, the other called negative feedback receives a signal and actually decreases or shuts off the original stimulus. In this manner most things are regulated in out bodies… blood calcium, body temperature, blood sugar. 

So, for example, our cells control what can enter and leave a cell. So maintaining water balance is vital to life and requires our cells to be in the know and adjust accordingly. If solute concentrations are getting to high and water is low we just might need some ADH and trigger some thirst. The flip would require water loss aldosterone to the rescue and urination would occur. 

Blood pH is balanced thanks to these two buffers that can be made. Should cell fins the pH too low, bicarbonates are secreted in the blood, too high of a pH and release carbonic acid. Body temp too low? Let’s generate some goose bumps, shiver and constrict blood flow in skin. Feelin’ hot, hot, hot….. send that hot blood to the surface by dilating those capillaries in the skin and releasing that sweat. 

So you can imagine…. cells sending signals,  receiving and then responding is vital… any part of this not happening and you’ve got dysfunction… more affectionately called disease.  Here is a great example of a disease… diabetes. Blood sugar not regulated (due to lack of hormone insulin) or cell’s not responding to insulin (stubborn things!). 

So in summary…. homeostasis is all about that balance.

Feedback mechanisms are in place to alert a change and respond accordingly. Postive feedback is just gonna amplify the signal…this is rare. And negative feedback is gonna shut that signal down.

And when cells don’t respond for whatever reason…. we’ve got a disease folks.

Thank you so much for reviewing homeostasis with me today. No go out and be your best self and happy nursing!