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Related Concept Videos

Mechanism of Cardiac Arrhythmias01:28

Mechanism of Cardiac Arrhythmias

Arrhythmias are irregular heart rhythms occurring when the heart's electrical impulses become abnormal. These disturbances can lead to various symptoms, depending on their severity and the underlying cause. Some common factors contributing to arrhythmias include hypoxia, ischemia, electrolyte imbalances, excessive catecholamine exposure, drug toxicity, and muscle overstretching. Arrhythmias can be classified into two main types based on the rate and site of origin of abnormal heart rhythms.
Specialized Characteristics of Cardiac Muscles01:27

Specialized Characteristics of Cardiac Muscles

The primary role of cardiac muscles is to propel blood throughout the cardiovascular system. The cardiac muscle cells, or cardiomyocytes, exhibit specialized characteristics that allow them to perform this function.
Cardiac muscle cells are smaller than skeletal muscles, averaging 10–20 mm in diameter and 50–100 mm in length. However, they have large energy demands for continuous contraction and relaxation. This energy is almost exclusively derived from aerobic metabolism of energy reserves in...
Electrophysiology of Normal Cardiac Rhythm01:19

Electrophysiology of Normal Cardiac Rhythm

The normal cardiac rhythm is a synchronized electrical activity that facilitates the regular and coordinated contraction of the heart muscle. This process is essential for efficient blood circulation throughout the body. The fundamental elements involved in establishing and maintaining this rhythm include the unique electrical properties of cardiac muscle cells, the sinoatrial (SA) node's pacemaker function, the specialized conducting system, and the ionic mechanisms underlying each phase of...
Cardiac Action Potential01:30

Cardiac Action Potential

Cardiac action potentials are essential for proper heart function, enabling the rhythmic contractions needed for adequate blood circulation. Nodal cells and Purkinje fibers, specialized for electrical conduction, generate these action potentials.
The cardiac action potential process involves a series of phases characterized by the movement of ions across the cardiac cell membranes, leading to the depolarization and repolarization of the cardiac myocytes.
Ionic Basis of Cardiac Action Potentials
Conduction System of the Heart01:19

Conduction System of the Heart

Autorhythmicity is a term that refers to the heart's inherent ability to generate electrical signals and instigate muscle contractions. This self-regulating conduction system within the heart consists of two key components: the pacemaker cells and specialized conducting cells.
The pacemaker cells are located in two primary nodes: the sinoatrial (SA) node and the atrioventricular (AV) node. The SA node pacemaker cells can autonomously depolarize, triggering an action potential that leads to the...
Conduction System of the Heart01:20

Conduction System of the Heart

The cardiac conduction system produces and transmits electrical impulses that prompt myocardial contraction, ensuring efficient heart function. This intricate system ensures that the heart beats in a coordinated and efficient manner, beginning with the atria and then the ventricles. The conduction system optimizes cardiac output by maintaining this precise sequence, which is crucial for adequate blood circulation.
This system relies on the unique properties of nodal and Purkinje cells:...

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Electromechanical Assessment of Optogenetically Modulated Cardiomyocyte Activity
12:52

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Published on: March 5, 2020

Cardiac mechanoreceptor function implicated during premature ventricular contraction.

M Zamir1, D S Kimmerly, J K Shoemaker

  • 1Neurovascular Research Laboratory, The University of Western Ontario, London, Canada. zamir@uwo.ca

Autonomic Neuroscience : Basic & Clinical
|January 10, 2012
PubMed
Summary
This summary is machine-generated.

Premature ventricular contractions (PVCs) lack the normal blood pressure peak that stops sympathetic outflow. Cardiac mechanoreceptors may instead signal the heart

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Area of Science:

  • Cardiovascular Physiology
  • Autonomic Nervous System Regulation

Background:

  • Normal sympathetic outflow termination relies on baroreflex mechanisms triggered by systolic pressure peaks.
  • Premature ventricular contractions (PVCs) disrupt this mechanism due to the absence of a systolic pressure peak.

Observation:

  • PVCs lead to prolonged hypotension and a subsequent surge in sympathetic activity.
  • The termination of this sympathetic surge during a PVC occurs without the expected baroreceptor activation.

Findings:

  • Analysis of ECG, arterial blood pressure, and muscle sympathetic neural activity revealed specific latencies during PVCs.
  • The end of ventricular filling during a PVC correlated with a physiologically plausible latency for sympathetic outflow termination.

Implications:

  • Cardiac mechanoreceptors may provide an alternative pathway for sympathoinhibition when baroreceptors are not activated.
  • This finding offers a new perspective on autonomic regulation during cardiac arrhythmias like PVCs.