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THE CORPORATE CHAMELEON. What Lizards Can Tell Us About Stress and Dominance Neil Greenberg University of Tennessee Department of Ecology and Evolutionary Biology. STRESS . . . . Is both a cause and a consequence; to be more precise, we should speak of
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THE CORPORATE CHAMELEON What Lizards Can Tell Us About Stress and Dominance Neil Greenberg University of Tennessee Department of Ecology and Evolutionary Biology
STRESS . . . Is both a cause and a consequence; to be more precise, we should speak of • STRESSORS: challenge our capacity to meet our needs, and • STRESS RESPONSE: our body's attempt to cope with a stressor by evoking neural and endocrine compensatory mechanisms.
HOMEOSTASIS . . . "It is the fixity of the milieu interieur which is the condition of free and independent life" (Claude Bernard, 1878)
HOMEOSTASIS . . . “The highly developed living being is an open system having many relations to its surroundings. . . changes in the surroundings excite reactions in this system, or affect it directly, so that internal disturbances are produced. . . the coordinated physiological reactions which maintain most of the steady states in the body are so complex, and so peculiar to the living organism, that it is suggested that a specific designation for these states be employed-- homeostasis"(W.B. Cannon 1929)
Many challenges, few responses • ”[the manifest] versatility [of the organism’s coping responses] presupposes a nervous system endowed with an unfailing sense of biological priorities, [and] is characteristic of the economy with which the body defends itself. • Instead of depending on a large number of separate mechanisms, each one of which is exclusively reserved for its own particular type of emergency, the body improvises responses to the threat of injury by assembling new combinations of pre-existing functions." (Miller, 1978:118).
STRESS helps us cope so we can satisfy our needs Maslow’s need hierarchy • Physiology (food, drink, exercise) • Safety (security, order, protection) • Belonging ( sociability, acceptance, love) • Esteem (status, prestige, acknowledgment) • Self-Actualization (personal fulfillment)
PATHOLOGY • There are many systems in the body which, because of misuse or misfortune, may have their services to the organism as a whole so altered as to be actually harmful. • Thus vicious circles of causation become established which may lead to death . . .
The Response: Nervous System • Central Integrative System • neural interpretation and integration of information leading to appropriate response. • Peripheral System • Autonomic Nervous System • Endocrine System
Optimal Arousal • A range of stimulation is not only tolerable, it is desirable (“adaptive scope”) • But stimuli from different sources may contribute to this range • So a stimulus is meaningful only in the context of possible convergence with others
EUSTRESS • A little stress is a good thing
DYSTRESS • A lot of stress is a bad thing
The Inverted U • The Inverted U theory , which is referred to as the Yerkes-Dodson Law, implies that performance is optimal at a moderate level of arousal, and that performance progressively declines as arousal increases or decreases from a moderate level.
The Green Anole • Small and inexpensive • Not endangered • Easily maintained • display wide range of behavioral patterns in the lab • Set up social dominance relationships quickly
Lizard Dominance • After an initial period of mutual testing for strength and stamina • Dominants remain green and subordinates become brown and adopt distinctive postures.
Chromomotor model for the stress response • Acute, repetitive, or sustained stressors are integrated in the CNS • Autonomic neurons activate the adrenal medullary response • H-P-A axis integrates the adrenal cortical response • The Anolis chromatophore reflects coping activities