Lie detector tests are used in our society by law enforcement agencies to help d

Question

Lie detector tests are used in our society by law enforcement agencies to help determine the guilt or innocence of a suspect. The basis of these exams is to assess the body’s reaction to stress via our sympathetic division of the autonomic nervous system. The effects of the sympathetic nervous system are widespread. Pick one gland, organ, or system that is affected by the sympathetic nervous system, describe the physiology of its actions on the chosen structure/system, and how the lie detector test assesses these changes.

Explanation / Answer

Cardiovascular system is affected by the sympathetic nervous system where the neurotransmitter norepinephrine is involved. Norepinephrine is a neurotransmitter that accelerates the heart and increases the blood pressure. Baroreceptors are pressure sensitive receptors present in the carotid sinus. These receptors respond to an increase in blood pressure by inhibiting the sympathetic motor neurons in the intermediolateral cell column of the spinal cord. The heart rate decreases and the contraction of the heart ventricles reduced. The parasympathetic nervous system, on the other hand is activated, reducing cardiac output. The reverse scenario occurs when the blood pressure decreases. The baroreceptors, thus maintain blood pressure along with reduced adrenergic vasoconstriction.

Blood pressure regulation is however more complex. It can occur even in anticipation of an alteration, before baroreceptors are stimulated. These physiological responses to changes in blood pressure and subsequent heart rate are the basis of the lie detector tests.

During lie detection or polygraphic detection, the person is asked question and the physiological reaction are collected from a) cardiovascular system (heart rate, blood volume, blood pressure, and b) from movement of chest cavity (respiratory) and c) endocrine system (activity of sweat gland). If the person says a wrong or untruth answers, anticipation or fear will cause changes in blood pressure or heart rate. On the other hand, true answers will not activate the cardiovascular systems too much. The differences in physiological changes will allow the lie detector to identify lies.

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