As I indicated in Chapter 2, the performance of the heart is determined by both the rate and the force at which it beats. The net result of this interaction is the CO, which, with respect to metabolic homeostasis, is the ultimate criterion of how effectively the heart is functioning. Our concern in psychophysiology is to ascertain the significance of neurohumoral mechanisms in the control of myocardial performance. Since it is usually impractical to measure the CO in humans and evaluate the role of neurogenic influences in this manner, we have to evaluate HR and/or myocardial force. HR, although one of the simplest biological events to measure, can provide equivocal information on neurogenic mechanisms (see Chapter 2). Although I have argued in Chapters 4 and 6 that the HR can be used to evaluate β-adrenergic influences under certain conditions because of our ability to tease out neurogenic effects pharmacologically, I am not entirely comfortable with this procedure because, in principle, it requires pharmacological intervention any time conditions are noticeably modified. Also, such interventions are not always practical. Because of these considerations, we have been engaged for some 10 years in an effort to assess whether β-adrenergic influences could be simply and accurately depicted by measuring myocardial force.
KeywordsCold Pressor Myocardial Performance Pulse Transit Time Passive Coping Tonic Level
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