Hi,
My
name is Franz Devantier, creator of this blog. I
am an Herbalist, who uses local and indigenous herbs when available, in
preference to imported herbs. Because
Herbalists deal with living human beings, it is important to have an
understanding of Anatomy and Physiology, as well as many other related
subjects,
such as How to grow old gracefully with Stem
Cell Enhancers.
Negative
Feedback Mechanisms
Most Homeostatic control
mechanisms are “Negative Feedback Mechanisms”.
A good example of a mechanical negative feedback system is a Home
Cooling system, which is connected to a temperature-sensing thermostat. The thermostat houses both the receptor and
the control center in this example. If
the thermostat is set to a comfortable temperature such as 22 degrees celcius,
then the cooling effect or the Effector
is triggered when the house temperature rises above 22 degrees. As the air conditioner comes back on line and
the air is cooled, it drops to below 22 degrees again, and the air conditioner
is switched off again. The result is
that the temperature is maintained at fairly close to 22 degrees. The set point is 22 degrees, and so the state
of Homeostasis is close to 22 degrees.
In the human body you have a
similar temperature control mechanism or thermostat that is located in a part
of your brain called the Hypothalamus, this is your body thermostat. This mechanism would operate in a similar
way. Various responses such as sweating
and constricting the blood vessels close to the skin will help to control the
body temperature at the ideal temperature.
There are other types of neural
control mechanisms. For example the
“withdrawal reflex”, in which the hand is withdrawn quickly from a painful
stimuli. In the withdrawal reflex, the
control center is not the brain, but the nerves structures that are present, long
before the stimuli would have reached the central nervous system. The endocrine system also has very important
mechanisms that it maintains, in order to maintain Homeostasis.
A good example of an endocrine or
hormonal control mechanism is the negative feedback system that is in place to
control the blood glucose levels, by means of the pancreatic hormones.
In order for normal body
metabolism to take place, normal body cells must have access to plenty of
glucose. This is the major fuel for
cells to produce energy, or ATP. Blood
sugar levels are normally maintained at around 90 milligrams of glucose per 100
millilitres of blood. Let’s assume that
you have lost your willpower, and have eaten an entire slab of sugar packed
chocolate. The chocolate is quickly
broken down to sugars, by your digestive system, and the surplus sugars, flood
the blood stream. As a result your blood
sugar levels have spiked upwards, and that delicately balanced balance of the
blood sugar level has been disrupted.
Homeostasis has been disrupted.
The rising glucose levels
stimulate the insulin producing cells of the pancreas, which responds by
secreting insulin directly into the blood.
Insulin accelerates the uptake of glucose by most body cells, and
encourages the storage of excess glucose as glycogen in the liver, as well as
the muscles of the body. This results in
a reserve of Glucose in the larder if you like.
As a result of this process blood sugar levels ebb back towards the
normal set point which is around 90 milligrams of glucose per 100 millilitres
of blood. As this happens the stimulus
for insulin release from the pancreas decreases. The above process ended with the Negative
feedback mechanism, as the body eased back into Homeostasis.
Glucagon, is the other pancreatic
hormone, and it has the opposite effect to Insulin. Suppose you have missed lunch, and your blood
sugar levels drop to lower levels, the release of Glucagon is triggered in the
pancreas. Glucagon is secreted directly
into the blood stream. Glucagon target
the liver, and stimulates the release of the Glucose or glycogen to be released
as Glucose into the bloodstream. As a
result the blood sugar levels start to increase, back towards their Homeostatic
range, and the stimuli for glucagon release diminishes.
The body’s ability to regulate its
internal environment is fundamental for survival, and all negative feedback
mechanisms have the same goal. To
prevent sudden severe changes within the body, and to maintain the body in a
state of Homeostasis. There are hundreds
of negative feedback mechanisms in the body, that helps to keep the body in a
state of homeostasis. Mechanisms that
regulate the heart rate or heart beat, blood pressure, the rate and depth of
breathing, and the blood levels of oxygen, carbon dioxide, and minerals.
Lets step through this process again:
Stimulus: Rising blood glucose levels.
-> message goes to the pancrease which is the control
center, and can determine the set point.
Insulin is secreted into the blood stream.
-> Most body cells take up more glucose, and the liver
stores the surplus glucose as glycogen.
-> Blood glucose levels declines to the set point, and
the stimulus for insulin decreases or ceases. (Negative Feedback Mechanism)
Homeostasis has been re-established.
Stimulus: Declining blood glucose levels:
-> message goes to pancreas or the control center, and
the pancreas causes glucagon to be released into the bloodstream.
-> Liver breaks down the Glycogen stores and release
glucose into the bloodstream.
-> Blood glucose level rises to set point, and the
stimulus for glucagon release diminishes. (Negative feedback Mechanism)
Homeostasis has been re-established.
Franz Devantier,
How to grow old gracefully with Stem
Cell Enhancers.
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