title: A theoretical study of hypothalamo-pituitary-adrenocortical axis dynamics.
abstract: Does the hypothalamo-pituitary-adrenocortical (HPA) axis itself generate oscillations? The affirmative answer to this question is commonly assumed, because a regular daily rhythm of its hormones is observed. We offer another plausible explanation of the origin of this pattern: HPA just responds to an external pacemaker. A qualitative mathematical model is constructed wherein all the terms in the equations are physicochemically interpretable. Linear stability analysis shows that this system does not generate oscillations. Computer simulation yields oscillations that are the system's response to an external pulsing activator, implying that the observed pattern does not have to be an intrinsic property of this system.
authors.affiliation: Institute of Nuclear Sciences Vinca, Laboratory for Theoretical and Condensed Matter Physics, Belgrade, Serbia and Montenegro. dankasav@eunet.yu
authors.forename: Danka
authors.initials: D
authors.lastname: Savić
authors.forename: Smiljana
authors.initials: S
authors.lastname: Jelić
mesh_terms: D000305:Adrenal Cortex Hormones / Q000502:physiology*; D000818:Animals; D001683:Biological Clocks / Q000502:physiology; D000697:Central Nervous System Stimulants / Q000494:pharmacology*; D002940:Circadian Rhythm / Q000502:physiology; D003198:Computer Simulation; D006054:Goldfish; D007030:Hypothalamo-Hypophyseal System / Q000502:physiology*; D008954:Models, Biological; D017711:Nonlinear Dynamics; D010913:Pituitary-Adrenal System / Q000502:physiology*
chemical_list: D000305:Adrenal Cortex Hormones; D000697:Central Nervous System Stimulants