In the past sections, we’ve been examining some aspects of the nervous
system. In this section and in this first lecture, we begin to discuss some
specifics of the nervous system and how it works.
The section that we’re going to talk about is called
feedback loops, or what we also call control systems. So, let’s begin by
looking at a control systems; what they are, and how they work. We begin on
slide two. In general, feedback loops and control systems are often
associated with the concepts of motivation. In general, what they’re
designed to do is keep the body at balance. Feedback loops and control
systems are also involved in lots and lots of different systems; for
example, your hunger system, thirst system, endocrine, temperature and many,
many others as well. The classic example of a control system looks similar
to what we see in slide three. You have some kind of controlling elements
which basically consist of behavioral, endocrine, and autonomic systems. We
have some kind of set point, that is, where we are at some kind of balance,
and we have inhibitory and stimulatory elements that are going to influence
the control system. Finally, we have some kind of feedback detector that
tells the set point—am I there or am I not.
So let’s talk about some of these systems in detail and
we’ll start with the discussion of set points. Set points are desired
values within a system, and they’re designed to keep you in some particular
level. The classic example that you might know is temperature; the classic
98.6 degrees as being the normal body temperature, or your body weight, or
your water balance.
Now from there, there’s some kind of a system that we call
an error detector. An error detector generates a signal that indicates some
variable does not match the set point. Once that occurs, it then begins to
drive the systems controlling those elements, and adjust the elements to
some desired direction controlled by both internal and external stimuli.
The controlling elements are (as we see in slide six), are the systems that
make changes after being keyed by the error detector. These systems can be
endocrine, behavioral or autonomic. So, might want to start shivering, or
you might need to drink some more water, or whatever it may be.
The control system or the controller system is a system
that makes the changes. So the specific thing that makes a particular
change. Do you eliminate more water or do you retain more water, or do you
begin to shiver to increase your body temperature or do you begin to sweat
to decrease your body temperature. All these are systems that make some
kind of particular change. And from these particular changes (as we see in
slide eight), we have some feedback detector. The feedback detector
identifies the changes that have occurred. So, it is at the set point and
the homeostatic balance has reoccurred then great, if not, then we need to
do something more. For example, if we’re talking about temperature, one
might begin with just shivering, and as we continue on we get cooler and
cooler, you might begin to shake even more. Pretty soon you start to shut
down blood to particular peripheral systems like in your fingers and toes to
try to get more blood into the core of the body and on and on.
But in addition to all of these systems we also have motor
control systems (shown in slide nine). Motor control systems are similar to
other systems, but they also have motor systems that send information to the
muscles. For example, we have stimulatory motor control systems and
inhibitory motor control systems. Muscles have sensory receptors as we have
with other systems. They send information back to the spinal cord and that
information goes to opposing neurons in the final common pathway or goes on
to the brain. This information ultimately ends up in sensory areas,
cerebellar areas, and other areas. These systems allow for very specific
fine motor control that gives us the capability to write very nicely.
So I’ve talked about a couple of different control systems
and how they work. In general, there are many, many different types of
feedback loops and control systems. They’re very specific to each system
and they’re extremely important for control and home use basis. As we begin
to talk about other structures within the system (especially hypothalamus
and other systems), we discuss this concept in more detail. But for right
now, I just wanted you to have a general overview of what a feedback and
control system are. So until next time, we will look forward to talking
with you.
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