Related Experiment Video
Updated: Jun 13, 2026
09:04
Skeletal Muscle Neurovascular Coupling, Oxidative Capacity, and Microvascular Function with 'One Stop Shop' Near-infrared Spectroscopy
Published on: February 20, 2018
Muscle metaboreflex-induced coronary vasoconstriction functionally limits increases in ventricular contractility
Matthew Coutsos1, Javier A Sala-Mercado, Masashi Ichinose
1Department of Physiology, Wayne State University School of Medicine, Detroit, MI, USA.
Journal of Applied Physiology (Bethesda, Md. : 1985)
|April 24, 2010
Summary
During exercise, the muscle metaboreflex increases cardiac work. Sympathetic vasoconstriction limits coronary vasodilation, which restrains left ventricular contractility increases.
Area of Science:
- Cardiovascular Physiology
- Exercise Physiology
Background:
- Muscle metaboreflex activation during exercise significantly increases cardiac work and oxygen demand.
- This increased demand should trigger coronary vasodilation, but sympathetic vasoconstriction limits this response.
Purpose of the Study:
- To investigate if sympathetic restraint of coronary vasodilation functionally limits left ventricular contractility during exercise.
Main Methods:
- Conscious dogs (n=9) were instrumented to measure cardiovascular parameters at rest and during exercise.
- Muscle metaboreflex was activated before and after alpha(1)-adrenergic blockade (prazosin).
- Key measurements included cardiac output, circumflex blood flow, and ventricular contractility indices (dP/dt(max), PRSW).
Main Results:
- Alpha(1)-adrenergic blockade significantly enhanced increases in coronary vascular conductance, blood flow, and cardiac output during metaboreflex activation.
- Blockade also led to greater increases in left ventricular contractility (dP/dt(max) and PRSW).
Conclusions:
- Sympathetic-mediated coronary vasoconstriction functionally limits the increase in left ventricular contractility during exercise.
- Blocking alpha(1)-adrenergic receptors alleviates this limitation, allowing for greater cardiac performance.
Related Concept Videos
01:29Pathophysiology of Cardiac Performance
Typical heart performance is influenced by heart rate, rhythm, myocardial contraction, and metabolism or blood flow. The cardiac muscle exhibits distinct electrophysiological features, including pacemaker activity and calcium channel control, which play a vital role in the heart's response to various drugs. The autonomic nervous system, comprising the sympathetic and parasympathetic branches, regulates heart rate. Sympathetic activation increases heart rate, while parasympathetic activation...
01:22Heart Failure Drugs: β-Blockers
β-adrenergic antagonists, commonly known as β-blockers, block the effects of sympathetic neurotransmitters such as noradrenaline (NA) and adrenaline (ADR). They have several beneficial effects in heart failure treatment. They reduce heart rate, the force of contraction, and cardiac muscle relaxation. They also slow the atrial-ventricular conduction rate and raise the threshold for arrhythmias. The concentration of β-blockers determines their effects on bronchodilation, vasodilation, and...
01:29Heart Failure II: Pathophysiology
Systolic Heart Failure and Compensatory MechanismsSystolic heart failure (also termed HFrEF, Heart Failure with Reduced Ejection Fraction) is the most prevalent type of heart filure. It results in a decreased volume of blood being pumped from the ventricle. The aortic arch and carotid sinuses have baroreceptors that detect reduced blood pressure, triggering the sympathetic nervous system (SNS) to release epinephrine and norepinephrine. Initially, this response aims to boost heart rate and...
01:25Smooth Muscle Contraction
Smooth muscle contraction is a complex process vital for various bodily functions, from maintaining blood vessel tension to facilitating the movement of food through the digestive tract. Unlike striated muscles, smooth muscle contraction begins more slowly and lasts longer.
The onset of contraction is triggered by an increase in calcium ions within the sarcoplasm, similar to the process in striated muscle. However, smooth muscles have a relatively smaller reservoir of the sarcoplasmic...
The onset of contraction is triggered by an increase in calcium ions within the sarcoplasm, similar to the process in striated muscle. However, smooth muscles have a relatively smaller reservoir of the sarcoplasmic...
01:20Exercise and Cardiovascular Response
Exercise significantly impacts cardiovascular response, which is crucial for understanding patient health and designing effective treatment plans.
Light to moderate physical activity initiates a series of interconnected responses in the body. The heart rate modestly increases in anticipation of the workout, followed by widespread vasodilation as oxygen consumption by skeletal muscles increases. This results in decreased peripheral resistance, increased capillary blood flow, and accelerated...
Light to moderate physical activity initiates a series of interconnected responses in the body. The heart rate modestly increases in anticipation of the workout, followed by widespread vasodilation as oxygen consumption by skeletal muscles increases. This results in decreased peripheral resistance, increased capillary blood flow, and accelerated...
01:17Autoregulation of Blood Flow
Autoregulation mechanisms are characterized by their inherent capacity for self-regulation without necessitating specific nervous stimulation or endocrine control. These mechanisms facilitate the adjustment of blood flow and, therefore, perfusion specific to each tissue region. This self-regulation encompasses chemical signals and myogenic controls.
Chemical Signaling in Autoregulation
Chemical signaling operates at the precapillary sphincter level, inciting either contraction or relaxation.
Chemical Signaling in Autoregulation
Chemical signaling operates at the precapillary sphincter level, inciting either contraction or relaxation.