Physiology: Lecture 1 Flashcards
Study of normal function of the body and how the body maintains those normal functions
Physiology
Inputs change and produce error but outputs remain normal; requires input of energy
Homeostasis - steady state
How we sense and react to input changes
Feedback control
Output reduces initial error (reduces input)
System is generally good
Negative feedback
Output is the same as the initial change (leads to an EVENT)
System is generally bad
Positive feedback
Examples of positive feedback
Ovulation
Clot formation
What do feedback mechanisms regulate?
Health
What happens when errors exceed the ability of the control system to adjust?
Disease and pathology occur; body will attempt to compensate for any deviation from set point
(Ex: drinking more and more and more water where your body can’t get rid of it all anymore and it begins diluting your blood and everything else, causing many problems)
When is compensation never complete?
As long as the error signal still exists
What is the bodies best response?
Full compensation (normal function may not be restored)
What happens to compensatory mechanisms as time progresses?
They break down or initiate changes that lead to pathology and disease
Normal serum potassium levels
Roughly 4 mEq/L
Pathological range of normal serum potassium
3.5-5.0 mEq/L
Pathological potassium levels (death)
Less than 2.5 mEq/L
Greater than 5 mEq/L
What can cause pathological potassium?
- Progressive change in electrical activity (heart)
- As little as 1 mEq/L change can lead to death
Pt presents with macular edema; they are overweight, drink a lot of soda, and has diabetes. What’s the outcome?
Pt needs to get diabetes under control or he’ll lose his eyesight. This re establishes his normal homeostasis physiology and everything else gets better.
Q: What type of feedback is this?
A –> B –> C -x-> A
Negative feedback
Because output feeds back on A to stop release
Q: Pt presents with abnormally high levels of B and C, but low levels of A. What is the likely defect?
A –> B –> C-x-> A
Tumor secretion of B
Cut tumor out to come back to homeostasis
Water is about how much of body weight?
60%
Avg = 50% to 70%
Variations of water per body weight?
Age
Race
Gender (male’s have more, typically)
Fitness level
Average percent of water per body weight in males: Adult? Elderly?
Adult: 70% BW
Elderly: 50% BW
Average percent of water per body weight in females: Adult? Elderly?
Adult: 50% BW
Elderly: 45% BW
What is water weight inversely correlated with?
Body fat
What is the ratio of intracellular fluid (ICF) to total body water (TBW)?
IDF is 2/3 of TBW (27L)