The Autonomic Nervous System

The autonomic nervous system (ANS), together with the somatic nervous system, are the two subdivisions of the peripheral nervous system. For temperament research the ANS is of special interest. Many physiological reactions that are regulated by means of the ANS are considered physiological correlates of several temperament characteristics. A few examples of such phenomena are electroder-mal activity (EDA), cardiovascular changes (e.g., heart rate, blood pressure), respiratory movements, and salivation may be mentioned.

The autonomic nervous system, which controls many vegetative and involuntary body functions, has two major divisions differently organized, namely, the sympathetic and the parasympathetic branches. Most organs innervated by the ANS are under the control of both branches, but in opposite relationships. In general, the parasympathetic NS is concerned with the storage and preservation of energy in the body; it tends to reduce the level of functioning. The sympathetic NS, on the other hand, is active during energy release, especially in situations demanding high concentration of energy mobilization, when the individual acts under stressful situations. The sympathetic NS, also responsible for the manifestation of emotions, tends to increase the level ofthe organism's functioning.

The neurotransmitter involved in the activity of the parasympathetic NS is acetylcholine, produced in the cholinergic terminals. The terminals of the sympathetic NS are noradrenergic, that is, they release noradrenaline. The sympathetic NS innervates not only the viscera and blood vessels but also the adrenal gland. Thus adrenaline and to some extent also noradrenaline are secreted from the adrenal gland when activated by the sympathetic NS which, however, in this section is mediated by acetylcholine. Table 4.1 provides summarized information about the functional differences between the sympathetic and parasympathetic branches of the ANS.

Despite the old beliefthat the ANS acts independently ofthe CNS, it has now become clear that the brain regulates the functions of the ANS. According to the hierarchical organization of the brain, lower nervous structures are under the control of higher nervous centers.

TABLE 4.1. The Functional Differences between the Sympathetic and

Parasympathetic Branches of the ANS

Autonomous Nervous System

Sympathetic Parasympathetic

TABLE 4.1. The Functional Differences between the Sympathetic and

Parasympathetic Branches of the ANS

Autonomous Nervous System

Sympathetic Parasympathetic

Catabolism

Anabolism

Activity of noradrenaline

Activity of acetylcholine

Diffuse, long lasting

Discrete, short-lasting

activity

activity

Dilates pupil of eye

Constricts pupil of eye

Scanty secretion of

Profuse secretion of

salivary glands

salivary glands

Increase of HR

Decrease of HR

Constricts blood vessels

Slight effect on blood vessels

Dilates bronchial tubes

Constricts bronchial tubes

oflungs

oflungs

Regulates ejaculation

Regulates erection

Stimulates sweat glands

Stimulates lacrimal gland

Contracts sphincters

Relaxes sphincters

Note. From Psychobiology of Personality ): (p. 257). by M. Zuckerman, 1991, New York: Cambridge University Press. Copyright 1991 by Cambridge University Press. Adapted with permission.

Note. From Psychobiology of Personality ): (p. 257). by M. Zuckerman, 1991, New York: Cambridge University Press. Copyright 1991 by Cambridge University Press. Adapted with permission.

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