Local control of venous function.

摘要: Abstract The main physiological role of the veins is to adjust capacity vascular system, ensuring an appropriate return blood heart. are also a determinant capillary pressure. can behave as passive reservoir, due connective structure their wall and presence valves in limbs. amount which passively mobilized from this reservoir towards heart determined by venous distending pressure, dependent on hydrostatic pressure load degree arteriolar constriction. contain adrenergically innervated smooth muscle. splanchnic capacitance vessels act active mobilization under sympathetic control; cutaneous linked more specifically thermoregulatory centers. Given constant drive, local factors modulate reactivity. Among these, effects temperature variations particular importance for veins, where they reinforce central control greatly facilitate heat preservation or dissipation. Metabolic regulation factors, such anoxia acidosis have little effect function, marked contrast at precapillary level; may explain behavior situations cardiovascular shock. Many neurohumoral substances (e.g. acetylcholine, histamine, adenine nucleotides) alter function both adrenergic nerves muscle cells wall; certain them (e.g., angiotensin II) modulation neurotransmission probably represents mechanism function. Different commonly used therapeutic agents interfere with neuroeffector interaction be beneficial patient nitrites cardiac glycosides) cause unwanted dysfunction halothane).