The peripheral nervous system is divided into
the somatic nervous system, which controls organs under voluntary control (mainly muscles)
and the autonomic nervous system, which regulates individual organ function and
homeostasis, and for the most part is not subject to voluntary control.
Autonomic Nervous System
The
Autonomic Nervous System is most important in two situations, those emergency situations
that cause stress and require us to "fight" or take "flight" (run
away) and those non-emergency situations that allow us to "rest" and
"digest". The autonomic nervous system consists of sensory neurons and motor
neurons that run between the central nervous system (especially the hypothalamus and
medulla oblongata) and various internal organs such as the brain, lungs, viscera, glands
(both exocrine and endocrine). The autonomic nervous system is responsible for monitoring
conditions in the internal environment and bringing about appropriate changes in them.
There are two major components of the autonomic nervous system, the sympathetic and the
parasympathetic systems.
The autonomic NS consists of small diameter axons, which supply the visceral organs
(stuff you cannot consciously regulate like hearts, guts, glands, etc.). For the case with
somatic motor neurons, it takes two efferent neurons for the autonomic NS to get from the
CNS to the effector cells. Effector cells are cells, which can do something when
instructed (e.g., cardiac, smooth and skeletal muscle, and all gland cells).
Procedure
The
autonomic NS is used for lie detection tests known as polygraphs. In this lab we ran a
simple lie detector exam to demonstrate the autonomic nervous systems role in lie
detection. A full scale, conventional lie detection exam hooks you up to a physiological
recorder to monitor functions controlled by the autonomic NS, but most specifically
actions set off by mass discharge of the sympathetic NS when the subject has an emotional
response associated with the telling of a falsehood. The sympathetic NS tends to fire off
all at once (flight or fight response) in such situations and all sorts of physiological
functions are altered. For example, heart rate goes up, pattern of respiration changes,
blood pressure goes up, and production of sweat by glands in the skin of the hand goes up.
We used a device called a Galvanic Skin Response (GSR) amplifier to monitor the production
of sweat by the glands in the skin of the hand.. To monitor the GSR we placed two
electrodes on the hand. One was wrapped around the finger of the subject without use of
conductive cream, and the second was attached to the wrist of the subject with the use of
conductive cream. The GSR passes a small current through the tissues of the hand. The
amount of current passing is dependent primarily on the electrical resistance under the
finger electrode. When the sympathetic NS discharges after any question, but particularly
in response to a critical question, sweat production goes up, the electrical resistance of
the skin goes down, more current flows, and a peak is registered on the recorder.
Setup
The
subject gets hooked up to GSR. Then the subject picks a number between 1 and 10 in front
of witnesses, however, the examiner must be absent. The examiner then is let back into the
room and must determine the number picked my the subject by asking the subject questions
answerable with a yes or no. A sample question might be, "was the number 1?" and
so on. The subject must answer truthfully or it will be detected by the polygraph machine.
The examiner checks the chart readout looking for peaks of tension, which are larger
responses. The examiner might be required to run through the series of numbers more than
once in order to check for consistency.
Here are some pictures of my lab section performing this experiment.
Equipment
Two
metal plates that are attached on the ring and index finger, conductive cream, and a
polygraph machine.
Polygraph machine
 |
A polygraph is an instrument that simultaneously records changes in
physiological processes such as heartbeat, blood pressure, and respiration. The underlying
theory of the polygraph is that when people lie they also get measurably nervous about
lying. The heartbeat increases, blood pressure goes up, breathing rhythms change,
perspiration increases, etc. A baseline for these physiological characteristics is
established by asking the subject questions whose answers the investigator knows.
Deviation from the baseline for truthfulness is taken as sign of lying. |
Finger Electrodes
|
Results
Here
are the results from of polygraph test from two different subjects in my lab. The first
picked the number eight; however, somehow the subject fooled the machine because the
results were unclear. The second subject, however, picked the number nine and as you can
see on the graph below there is an obvious fluctuation in the graph every time the subject
was asked if the number was nine.
ZOOLOGY 310 GUIDE
TO AUTONOMIC NERVOUS SYSTEM & POLYGRAPHY
