1.4 Homeostasis Flashcards
Homeo-, ___ ____; -stasis, __ _____
Homeo-, the same; -stasis, to stop
Maintenance of a relatively constant internal environment despite fluctuations in the external environment
Homeostasis
How to achieve Homeostasis?
The body must actively regulate body conditions that are constantly changing
Body conditions that are constantly changing?
Variables
Mechanism that maintain normal body conditions
Homeostatic Mechanism
Example of a Homeostatic Mechanism
Shivering and sweating to maintain body temp
Ideal normal value that homeostatic mechanism aims to achieve
Set Point
What systems regulates most homeostatic mechanisms?
Nervous or Endocrine Sytem
Increase and decrease slightly around a set point
Normal range of values
Average Body Temp
98.6
“Negative” feedback Meaning
“Negative” - to decrease
Mechanisms that maintain homeostasis
- Negative Feedback
- Positive Feedback
Three components of Negative Feedback
Receptor, Control Center, Effector
___________ signal the _______, which regulates the action of the __________.
Receptors signal the control center, which regulates the action of the effectors.
Monitors the value of a variable (ex. Body temp) by detecting stimuli.
Receptor
Determines the set point for the variable and receives input from the receptor about the variables and receives input from the receptor about the variable (ex. Part of the brain)
Control Center
can adjust the value of the variable when directed by the control center, usually back toward the set point (ex. Sweat glands).
Effector
A changed variable because it initiates a homeostatic mechanism.
Stimulus
Hallmark of Negative Feedback
Effectors stop their response once the variable has returned to its set point.
“Positive” Feedback Meaning
“Positive” - to increase
This type of response is required to return to homeostasis.
Positive Feedback
Example of Positive Feedback
- During blood loss, thrombin, a chemical responsible for blood clot formation, stimulates production of even more thrombin.
- Giving Birth (See Transes Page 5)
2 Basic Principles about homeostatic mechanisms
- Many disease states result from the failure of negative-feedback mechanisms to maintain homeostasis, and
- Some positive-feedback mechanisms can be detrimental instead of helpful.
