Related Experiment Video
Updated: Aug 14, 2026

Recording and Analysis of Circadian Rhythms in Running-wheel Activity in Rodents
Published on: January 24, 2013
Endogenous circadian control of the human autonomic nervous system
M F Hilton1, M U Umali, C A Czeisler
1Circadian, Neuroendocrine and Sleep Disorders Section, Brigham and Women's Hospital/Harvard Medical School, Boston, USA. mhilton@gcrc.bwh.harvard.edu
Abstract:
To determine if an endogenous circadian rhythmicity, independent from sleep/wake cycles, exists in autonomic nervous system (ANS) function, heart rate variability analysis of electrocardiogram R-R intervals was applied to data collected during a 27-day forced desynchrony protocol. Results during wakefulness indicate that the circadian pacemaker may control both the sympathetic and vagal limbs of the ANS. Vagal tone was maximal during the circadian phase corresponding to the usual sleep episode (although these measurements were made in the absence of sleep) with an acrophase at 4 AM to 5 AM. Sympathovagal balance was minimal between 9 AM and 1 PM. These endogenous circadian rhythms in ANS function may contribute to mortality from cardiovascular disease and nocturnal asthma.
Related Concept Videos
The Parasympathetic Nervous System
Circadian Rhythms and Gene Regulation
Autonomic Nervous System: Overview
Autonomic Nervous System
The ANS comprises two main divisions: the sympathetic and parasympathetic divisions. These divisions function antagonistically to maintain a dynamic...
Neural Regulation of Blood Pressure
Baroreceptor Reflex
Baroreceptors, located in the carotid sinuses and aortic arch, detect changes in blood pressure. When blood pressure rises, these stretch-sensitive receptors...
Chronopharmacokinetics: Circadian Rhythms and Influence on Drug Response
The time of drug administration is an important factor to consider, as it can influence the toxic dose of a drug. For example, a study conducted by Prins et al. in 1997 examined the effects of the timing of...

