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Related Concept Videos

Conduction System of the Heart01:19

Conduction System of the Heart

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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.
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Conduction System of the Heart01:20

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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.
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According to Newton’s second law of motion, the rate of change of the momentum of an object is the net external force acting on it. The total change in momentum between two timepoints thus depends on both the external force acting on it and the time over which it acts. Describing this mathematically, the total change of an object’s motion is proportional to the force vector and the time over which it is applied. This product is called impulse.
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The impulse response is the system's reaction to an input impulse. In an RC circuit, the voltage source is the input, and the capacitor's voltage is the output. The system's state and output response before and after input excitation are distinctly defined.
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Specialized staining techniques play a vital role in microbiology by enabling the visualization of specific bacterial structures that remain undetectable with standard microscopy methods. These techniques not only enhance the structural visualization of bacterial cells but also provide critical insights into their pathogenicity and classification. Additionally, they support diagnostic and research endeavors in microbiology by identifying key bacterial features.Capsule Staining for Virulence...
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Sensory receptors play an integral part in comprehending our external and internal environments. They receive diverse stimuli, converting them into the nervous system's electrochemical signals. This conversion occurs as the stimulus alters the sensory neuron's cell membrane potential, instigating the generation of an action potential. This action potential is subsequently transmitted to the central nervous system (CNS), which integrates with other sensory data or higher cognitive...
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Related Experiment Video

Updated: Feb 12, 2026

Optocardiography and Electrophysiology Studies of Ex Vivo Langendorff-perfused Hearts
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Specialized impulse conduction pathway in the alligator heart.

Bjarke Jensen1, Bastiaan J Boukens1,2, Dane A Crossley3

  • 1Department of Medical Biology, Heart Failure Research Center, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands.

Elife
|March 23, 2018
PubMed
Summary

Crocodiles possess a functional atrioventricular bundle, a key cardiac component, but lack the specialized Purkinje network found in warm-blooded animals. This suggests the bundle evolved before high heart rates and endothermy.

Keywords:
American alligatorTbx3Ventricular septumconduction systemdevelopmental biologyevolutionevolutionary biologygenomicsstem cells

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Area of Science:

  • Cardiovascular Physiology
  • Evolutionary Biology
  • Comparative Anatomy

Background:

  • Mammals and birds exhibit specialized cardiac conduction systems for rapid ventricular activation, supporting endothermy.
  • This system appears absent in ectothermic vertebrates, from which mammals and birds evolved independently.

Purpose of the Study:

  • Investigate the cardiac conduction system in crocodiles (Alligator mississippiensis), ectotherms with a complete ventricular septum.
  • Identify homologous markers of mammalian conduction system components.
  • Determine the functional basis of ventricular conduction in crocodiles.

Main Methods:

  • Studied the conduction system in Alligator mississippiensis.
  • Identified homologues of key mammalian conduction system markers (Tbx3-Tbx5, Scn5a, Gja5, Nppa-Nppb).
  • Assessed the presence and function of the atrioventricular bundle and Purkinje network.

Main Results:

  • Homologues of mammalian conduction system markers were identified in crocodiles.
  • A functional atrioventricular bundle was present.
  • The ventricular Purkinje network was absent; conduction relied on trabecular myocardium.

Conclusions:

  • The evolution of the atrioventricular bundle likely preceded high heart rates and endothermy, following ventricular septum formation.
  • The ventricular Purkinje network's evolution is strongly linked to high heart rates and endothermy.