<< Chapter < Page Chapter >> Page >
By the end of this section, you will be able to:
  • Define homeostasis
  • Describe the factors affecting homeostasis
  • Discuss positive and negative feedback mechanisms used in homeostasis
  • Describe thermoregulation of endothermic and ectothermic animals

Animal organs and organ systems constantly adjust to internal and external changes through a process called homeostasis (“steady state”). These changes might be in the level of glucose or calcium in blood or in external temperatures. Homeostasis means to maintain dynamic equilibrium in the body. It is dynamic because it is constantly adjusting to the changes that the body’s systems encounter. It is equilibrium because body functions are kept within specific ranges. Even an animal that is apparently inactive is maintaining this homeostatic equilibrium.

Homeostatic process

The goal of homeostasis is the maintenance of equilibrium around a point or value called a set point    . While there are normal fluctuations from the set point, the body’s systems will usually attempt to go back to this point. A change in the internal or external environment is called a stimulus and is detected by a receptor; the response of the system is to adjust the deviation parameter toward the set point. For instance, if the body becomes too warm, adjustments are made to cool the animal. If the blood’s glucose rises after a meal, adjustments are made to lower the blood glucose level by getting the nutrient into tissues that need it or to store it for later use.

Control of homeostasis

When a change occurs in an animal’s environment, an adjustment must be made. The receptor senses the change in the environment, then sends a signal to the control center (in most cases, the brain) which in turn generates a response that is signaled to an effector. The effector is a muscle (that contracts or relaxes) or a gland that secretes. Homeostatsis is maintained by negative feedback loops. Positive feedback loops actually push the organism further out of homeostasis, but may be necessary for life to occur. Homeostasis is controlled by the nervous and endocrine system of mammals.

Negative feedback mechanisms

Any homeostatic process that changes the direction of the stimulus is a negative feedback loop    . It may either increase or decrease the stimulus, but the stimulus is not allowed to continue as it did before the receptor sensed it. In other words, if a level is too high, the body does something to bring it down, and conversely, if a level is too low, the body does something to make it go up. Hence the term negative feedback. An example is animal maintenance of blood glucose levels. When an animal has eaten, blood glucose levels rise. This is sensed by the nervous system. Specialized cells in the pancreas sense this, and the hormone insulin is released by the endocrine system. Insulin causes blood glucose levels to decrease, as would be expected in a negative feedback system, as illustrated in [link] . However, if an animal has not eaten and blood glucose levels decrease, this is sensed in another group of cells in the pancreas, and the hormone glucagon is released causing glucose levels to increase. This is still a negative feedback loop, but not in the direction expected by the use of the term “negative.” Another example of an increase as a result of the feedback loop is the control of blood calcium. If calcium levels decrease, specialized cells in the parathyroid gland sense this and release parathyroid hormone (PTH), causing an increased absorption of calcium through the intestines and kidneys and, possibly, the breakdown of bone in order to liberate calcium. The effects of PTH are to raise blood levels of the element. Negative feedback loops are the predominant mechanism used in homeostasis.

Questions & Answers

what is cell?
V.S.Nikhil Reply
The smallest structure and functional unit
vinod
Hydra reproduce through which process
Saint Reply
which is smallest organ in our body
Techi
pineal gland
Himangshu
Yh in the ears...
Mozua
why you hand plam is sweating in everytime
Techi
who is the father of mycology
Sagar Reply
Heinrich Anton de Bary
Delissa
describe the similarities and differences between cytokinesis mechanism found in animal cells versus in plant cells
hiro Reply
are humans beings considered to have the eukaryotic cells
success Reply
yes.....
Delissa
eukaryotes are organisms that possess cells with a nucleus enclosed in a membrane, humans, and all complex organisms are eukaryotes.
Delissa
so humans and animals also have cell membranes.... cause I did this test prep and they said plants...I just want to be sure
success
and thank you for your reply it was helpful👍✌
success
eu= "perfect", "good", karyon= nut, amound, nucleus
Tiago
you're welcome. Plants are also eukaryotes.
Delissa
plants, like animals, possess a nucleus bound by a membrane.
Delissa
similarities and differences between cytokinesis mechanism found in animal cell vs cell division
Raymark Reply
what is the name of a male flower?
Ikeomu Reply
staminate means flower containing only stamen
Falak
what is the definition of evolution in a population?
Homero Reply
the slow changing of a species to adapt to any changes in the environment or how it feeds/hunts. im not good at explaining things lol.
Eclipse
the organ which is sensitive to light in euglena
Fatimah Reply
the organ which is sensitive to light in euglena is
Fatimah
all chlorophyll containing motile cells are sensitive to light
Himangshu
there is no more other chapter
Sandeep Reply
Give tow examples for nutritional deficiency Diseases-
Singampalli Reply
How does a plant cell look like
Sang Reply
in a sleepers form
David
what do you mean ? I could not understand
Gul
they have a regular shape and a large vacoule
Fatimah
I thought it looked like rectangle
Abrahán
a stage in mitosis wherein in spindle fibers begin to shorten to pu the sister chromatids away from each other towards the opposite ends of the cell
Earl Reply
a stage in interphase where chromosome s are duplicated
Earl
What is biodiversity
Sp Reply
Hmm
Hele
Name two secretions of Golgi apparatus
Daniel Reply

Get the best Biology course in your pocket!





Source:  OpenStax, Biology. OpenStax CNX. Feb 29, 2016 Download for free at http://cnx.org/content/col11448/1.10
Google Play and the Google Play logo are trademarks of Google Inc.

Notification Switch

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

Ask