Related Experiment Video
Updated: Jul 10, 2026
Cardiac Catheterization in Mice to Measure the Pressure Volume Relationship: Investigating the Bowditch Effect
Published on: June 14, 2015
Inferring vagal effects on the heart from changes in cardiac cycle length: implications for cycle time-dependency
M Velden1, J M Karemaker, C Wölk
1University of Osnabrück, F.R.G.
Abstract:
Since the now classical experiments by Brown and Eccles in 1934, the effect of a stimulation of the vagus nerve on the heart has been derived from changes in the length of cardiac periods. Based on a simple model for the genesis of heartbeats, it is shown that the procedure employed by Brown and Eccles gives a distorted picture of the actual vagal effect. A corrected procedure for inferring the vagal effect from changes in heart period length is proposed. This new procedure is applied to empirical data from animal experiments with direct stimulation of the vagus nerve. It is shown that, if the vagal effect depends on time of stimulation within the cardiac cycle (cycle time-dependency), single vagal effect curves for each time of stimulation within the cycle have to be constructed. Other data reduction procedures are reviewed with respect to their appropriateness for demonstrating cycle time-dependency.
Related Concept Videos
01:13The Cardiac Cycle
The Process
Electrical signals—sent from the sinoatrial (SA) node in the right atrial wall to the atrioventricular (AV) node between the right atrium and right ventricle—cause both atria to simultaneously contract. When the signal reaches the AV node, it pauses for approximately a tenth of a second, allowing the atria to contract and empty blood into the...
01:30Factors Influencing Heart Rate
Let us explore the significant factors affecting heart rate, including age, body temperature, posture, acute pain, chemical influences,...
01:29Cardiac Cycle
During the cardiac cycle, blood flow through the heart is regulated entirely by changing pressure gradients. This sequence of events begins with the heart in a state of total relaxation, known as mid-to-late diastole, during which blood passively flows from...
01:25Correlation between ECG and Cardiac Cycle
A cardiac action potential originates in the SA node and spreads throughout the atria and the AV node in approximately 0.03 seconds. This results in the P wave in an ECG and triggers atrial contraction. The action potential is then briefly slowed at the AV node, allowing the atria to contract and fill the ventricles with blood before...
01:18Physiology of the Heart: The Cardiac Cycle
Diastole: The Relaxation Phase
During diastole, all four heart chambers relax. The atrioventricular (AV) valves open, and the semilunar valves close. This phase sees the lowest chamber pressures, promoting ventricular filling. Venous blood enters the heart through the...
01:19Cardiac Output I:Effect of Heart Rate on Cardiac Output
Cardiac output (CO) refers to the total amount of blood ejected by one of the ventricles in liters per minute (L/min). In a resting adult, CO ranges from 5 to 6 L/min, adjusting according to the body's metabolic requirements.
Effect of Heart Rate on Cardiac Output
Cardiac output adapts to metabolic demands during stress, physical activity, or illness. The autonomic nervous system regulates heart rate via the sinoatrial node. The parasympathetic nervous system decreases heart rate...