<< Chapter < Page Chapter >> Page >
By the end of this section, you will be able to:
  • Discuss the role of homeostasis in healthy functioning
  • Contrast negative and positive feedback, giving one physiologic example of each mechanism

Maintaining homeostasis requires that the body continuously monitor its internal conditions. From body temperature to blood pressure to levels of certain nutrients, each condition has a particular set point. A set point    is the value around which the normal range fluctuates. A normal range    is the set of values that is most healthful and stable. For example, the set point for normal human body temperature is approximately 98.6°F. Physiological conditions, such as body temperature and blood pressure, tend to fluctuate within a normal range a few degrees above and below that point. Control centers in the brain play roles in keeping them within the normal range. As the body works to maintain homeostasis, any significant change from the normal range will be resisted and homeostasis will be restored through a process called negative feedback. Negative feedback is a mechanism that prevents a condition from going beyond the normal range by reversing the action once the normal range is exceeded. Negative feedback serves to make the variation smaller, so the imbalance is lessened. The maintenance of homeostasis by negative feedback goes on throughout the body at all times, and an understanding of negative feedback is thus fundamental to an understanding of human physiology.

Negative feedback

A negative feedback system has three basic components ( [link] a ). A receptor , is a part of a feedback system that monitors a physiological value (temperature for example). This value is reported to a control center such as the brain. The control center    is the part in a feedback system that compares the value to the normal range. If the value deviates too much from the set point, then the control center activates an effector. An effector    is the part in a feedback system that causes a change to reverse the situation and return the value to the normal range.

Negative feedback loop

This figure shows three flow charts labeled A, B, and C. Chart A shows a general negative feedback loop. The loop starts with a stimulus. Information about the stimulus is perceived by a sensor which sends that information to a control center. The control center sends a signal to an effector, which then feeds back to the top of the flow chart by inhibiting the stimulus. Part B shows body temperature regulation as an example of negative feedback system. Here, the stimulus is body temperature exceeding 37 degrees Celsius. The sensor is a set of nerve cells in the skin and brain and the control center is the temperature regulatory center of the brain. The effectors are sweat glands throughout the body which inhibit the rising body temperature.
In a negative feedback loop, a stimulus—a deviation from a set point—is resisted through a physiological process that returns the body to homeostasis. (a) A negative feedback loop has four basic parts. (b) Body temperature is regulated by negative feedback.

When a stimulus drives a value is outside of the normal range, the system is set in motion. The value must be beyond its normal range (that is, beyond homeostasis). This abnormal value is detected by a specific sensor. For example, in the control of blood glucose, specific cells in the pancreas detect excess glucose (the stimulus) in the bloodstream. These pancreatic cells respond to the increased level of blood glucose by releasing the hormone insulin into the bloodstream. The insulin signals skeletal muscle fibers, fat cells and liver cells to take up the excess glucose, removing it from the bloodstream. As glucose concentration in the bloodstream returns to normal, the decrease in concentration—the actual negative feedback—is detected by pancreatic cells, and insulin release stops. This prevents blood sugar levels from continuing to drop below the normal range.

Questions & Answers

I only see partial conversation and what's the question here!
Crow Reply
what about nanotechnology for water purification
RAW Reply
please someone correct me if I'm wrong but I think one can use nanoparticles, specially silver nanoparticles for water treatment.
Damian
what is the stm
Brian Reply
is there industrial application of fullrenes. What is the method to prepare fullrene on large scale.?
Rafiq
industrial application...? mmm I think on the medical side as drug carrier, but you should go deeper on your research, I may be wrong
Damian
How we are making nano material?
LITNING Reply
what is a peer
LITNING Reply
What is meant by 'nano scale'?
LITNING Reply
What is STMs full form?
LITNING
scanning tunneling microscope
Sahil
how nano science is used for hydrophobicity
Santosh
Do u think that Graphene and Fullrene fiber can be used to make Air Plane body structure the lightest and strongest. Rafiq
Rafiq
what is differents between GO and RGO?
Mahi
what is simplest way to understand the applications of nano robots used to detect the cancer affected cell of human body.? How this robot is carried to required site of body cell.? what will be the carrier material and how can be detected that correct delivery of drug is done Rafiq
Rafiq
what is Nano technology ?
Bob Reply
write examples of Nano molecule?
Bob
The nanotechnology is as new science, to scale nanometric
brayan
nanotechnology is the study, desing, synthesis, manipulation and application of materials and functional systems through control of matter at nanoscale
Damian
Is there any normative that regulates the use of silver nanoparticles?
Damian Reply
what king of growth are you checking .?
Renato
What fields keep nano created devices from performing or assimulating ? Magnetic fields ? Are do they assimilate ?
Stoney Reply
why we need to study biomolecules, molecular biology in nanotechnology?
Adin Reply
?
Kyle
yes I'm doing my masters in nanotechnology, we are being studying all these domains as well..
Adin
why?
Adin
what school?
Kyle
biomolecules are e building blocks of every organics and inorganic materials.
Joe
anyone know any internet site where one can find nanotechnology papers?
Damian Reply
research.net
kanaga
sciencedirect big data base
Ernesto
Introduction about quantum dots in nanotechnology
Praveena Reply
what does nano mean?
Anassong Reply
nano basically means 10^(-9). nanometer is a unit to measure length.
Bharti
do you think it's worthwhile in the long term to study the effects and possibilities of nanotechnology on viral treatment?
Damian Reply
absolutely yes
Daniel
how to know photocatalytic properties of tio2 nanoparticles...what to do now
Akash Reply
it is a goid question and i want to know the answer as well
Maciej
characteristics of micro business
Abigail
for teaching engĺish at school how nano technology help us
Anassong
How can I make nanorobot?
Lily
how did you get the value of 2000N.What calculations are needed to arrive at it
Smarajit Reply
Privacy Information Security Software Version 1.1a
Good
Got questions? Join the online conversation and get instant answers!
Jobilize.com Reply

Get the best Algebra and trigonometry course in your pocket!





Source:  OpenStax, Introduction to anatomy. OpenStax CNX. Jan 26, 2015 Download for free at http://legacy.cnx.org/content/col11755/1.1
Google Play and the Google Play logo are trademarks of Google Inc.

Notification Switch

Would you like to follow the 'Introduction to anatomy' conversation and receive update notifications?

Ask