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Essential Hypertension and Its Causes - Neural and Non-Neural Mechanisms (Hardcover)
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Essential Hypertension and Its Causes - Neural and Non-Neural Mechanisms (Hardcover)
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This new account of the pathogenesis of essential hypertension (EH)
represents a detailed analysis of the main components of the
circulatory control system. The latter's properties resemble those
of man-made adaptive control systems in which regulatory parameters
are altered when operating conditions exceed certain limits, often
through neural mechanisms.
Inheritance of EH depends on both genes and environment. The high
blood pressure (BP) genes have not yet been definitively
identified, whilst the main environmental causes are mental stress,
high dietary salt intake and obesity. EH occurs as two major
syndromes, each initiated by chronic stress: 1) Stress-and-salt
related EH, and 2) Hypertensive obesity. Stress is perceived by the
cortex, from which increased dopaminergic (DA) neuron activity
stimulates the hypothalamic defense area, raising sympathetic
neural activity (SNA) and BP. Normally these subside quickly when
the stress is over, but in those susceptible to EH the DA synapses
become sensitized so that the defense response is evoked by ever
lower levels of stress. Sensitization is common in memory circuits,
but not in autonomic neurons, so that this property in EH may be
genetically determined.
Stress-related hypertension increases hypothalamic responsiveness
to high salt, resulting in further rises in SNA and BP. Later,
non-neural functional changes (e.g. reduction in nitric oxide) and
the structural remodeling of resistance vessels further enhance the
vasoconstriction. In contrast, in those developing hypertensive
obesity food consumption is excessive, which transiently alleviates
stress-related anxiety. The brain ignores the leptin-mediated
signals that normally curbappetite, contrasting with normal energy
regulation in SSR-EH. In hypertensive obesity, the SNA pattern is
similar to that in SSR-EH, but vasoconstriction is masked by
vasodilatation and fluid retention due to hyperinsulinemia. This
syndrome is a volume overload hypertension, where high cardiac
output, renal impairment and other non-neural factors contribute to
the elevation of BP.
Other topics include the role of various transmitters in autonomic
regulation; the place of baroreflexes in the intact organism; why
exercise training lowers resting BP; obstructive sleep apnea;
non-pharmacological and drug treatment of EH; the role of the
kidney in EH and in different types of renal hypertension and the
pathogenesis of the Japanese spontaneously hypertensive rat, which
provides a valuable animal model for EH.
The work suggests that physiological systems analysis in a complex
disorder like EH is a valuable tool for using the great advances in
molecular biology to best advantage.
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