Welcome back to BOGObiology. This is 5 minute bio, where we discuss a key
concept in 5 minutes or less. Today's topic is homeostasis. Homeostasis is a dynamic equilibrium or balance
which is actively regulated to maintain a variable a constant level. In biology, homeostasis is often related to
an internal balance within a cell or organism because so many creatures have a very narrow
range of conditions in which they can survive. Two examples of homeostasis you might be familiar
with are body temperature and blood glucose level. The human body has an ideal temperature of
about 98.6 degrees Fahrenheit, or about 37 degrees Celcius. If the human body gets too hot or too cold,
the proteins and chemical reactions that are crucial to make our bodies work will not function
properly. If the problem is not fixed, there is a distinct
risk of tissue or even organism death. Blood glucose level is also a common example
of homeostasis although one that you are probably less familiar with. Your body needs sugar in order to run the
process of cellular respiration and provide energy for your cells. There is an ideal amount of sugar to have
in one's blood, which is about 90-120 milligrams per deciliter. Having the wrong amount of sugar in one's
blood can have serious consequences, particularly if your blood sugar dips too low. While skipping a meal might cause someone
to be irritable or have low energy, having blood sugar that is severely below normal
can cause coma and even death. Before we move on, see if you can think of
other examples of homeostasis and also think about the consequences of deviating from a
set point for too long. Hopefully you figured out that prolonged deviation
from an ideal set of conditions can cause cell, tissue and organism death. Maintaining homeostasis often requires that
an organism have an internal environment that is different from its external environment. Barriers between internal and external environments
allow the organism to maintain an internal environment despite what's going on in the
external environment. A great example of this is the cell membrane. Organisms, including humans, use something
called a feedback loop to help maintain homeostasis. Feedback loops are broken into three parts;
the stimulus, the sensor and the response. Let's start with this loop over here on the
left. Imagine that it's a very hot day and the individual's
body temperature is rising. The rising temperature is the stimulus. The stimulus is then detected by the sensor
located in the brain. In humans, a temperature change would be detected
by the hypothalamus, but obviously Homer Simpson's brain is a little different (!). Because high
temperatures can cause cell death, the body then goes into action to bring its core temperature
down. Blood vessels will dilate, allowing heat to
radiate outwards. The person will also begin to sweat in order
to decrease their body temperature via evaporative cooling. Hopefully, the overall effect of these steps
will be enough to bring the individual's body temperature back down towards normal. This phenomenon is called a negative feedback
loop, not because it is bad, but because it helps to make the situation less extreme. See if you can figure out what would happen
on the right side of this loop when the temperature gets too cold, rather than too hot. Ideally, if your body temperature gets too
cold, you begin to shiver after detecting the decreased temperature in your hypothalamus. The shivering generates heat, which should
bring your body temperature back up. Positive feedback is pretty rare in nature
because it tends to make a situation more extreme. However, we do have two examples here; the
clotting of blood and the increase in uterine contractions during labor. Both passive and active transport can be used
to help maintain homeostasis. In passive transport, such as osmosis and
diffusion, particles flow from an are of high concentration to an area of low concentration
and can very effectively fill a space. If deviation from a set point has been detected,
ATP can also be spent in order to pump particles against the concentration gradient and restore
homeostasis. A few key concepts to remember: First, homeostasis
is a desirable state of equilibrium. Generally, maintaining homeostasis in biology
also means maintaining ideal internal survival conditions. Second, most organisms use negative feedback
loops to maintain the state of homeostasis. Finally, we also use passive and active transport
in order to maintain this desirable state of equilibrium. That's it for today! As always, make sure to cite your sources. If you'd like to cite BOGObiology, there is
an APA citation in the video description. Thanks again for stopping by and don't forget
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