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Related Concept Videos

Electrophysiology of Normal Cardiac Rhythm01:19

Electrophysiology of Normal Cardiac Rhythm

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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...
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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.
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The human body has three types of muscle tissue: skeletal, smooth, and cardiac. Each class has unique properties that enable them to perform specific functions. However, all muscle tissues share certain properties, including elasticity, contractility, and excitability. 
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Conduction System of the Heart01:19

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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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Structure of Cardiac Muscles01:13

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Cardiac muscle, or myocardium, is a specialized type of muscle found exclusively in the heart. Its unique structural and functional characteristics enable the heart to perform its vital role of pumping blood throughout the body continuously and rhythmically. The cardiac muscle cells, or cardiomyocytes, possess an endomysium and perimysium but do not have an epimysium.
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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...
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Related Experiment Video

Updated: May 22, 2025

Generation of Murine Cardiac Pacemaker Cell Aggregates Based on ES-Cell-Programming in Combination with Myh6-Promoter-Selection
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Tissue elasticity modulates cardiac pacemaker cell automaticity.

Young Hwan Choi1,2, Jing Leng1,2, Jinqi Fan1,2

  • 1The Blalock-Taussig-Thomas Pediatric and Congenital Heart Center, Johns Hopkins Children's Center, Baltimore, Maryland, United States.

American Journal of Physiology. Heart and Circulatory Physiology
|March 13, 2025
PubMed
Summary
This summary is machine-generated.

Stiffer gelatin hydrogels enhanced cardiac pacemaker cell automaticity and Hcn4 expression. This study offers a new in vitro model for studying heart rhythm and fibrosis.

Keywords:
TBX18elastic modulusgelatin hydrogelpacemaker cellssinoatrial node

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Area of Science:

  • Cardiovascular Biology
  • Biomaterials Science
  • Cellular Mechanobiology

Background:

  • Tissue elasticity is crucial for cardiac function, but conventional cell cultures on rigid plastics limit studying its effects.
  • The cardiac conduction system, particularly pacemaker cells, requires specific mechanical environments.
  • Gelatin hydrogels offer a tunable platform to mimic tissue elasticity for cell culture.

Purpose of the Study:

  • To investigate the impact of varying tissue stiffness on cardiac pacemaker cell function.
  • To utilize transcription factor-reprogrammed pacemaker cells on gelatin hydrogels of defined elasticity.
  • To model mechanoelectric feedback in cardiomyocytes and conduction system cells.

Main Methods:

  • Culturing pacemaker cells on gelatin hydrogels with controlled elasticity (e.g., 14 kPa).
  • Measuring cell automaticity via rhythmic contractions and intracellular calcium (Ca2+) transients.
  • Assessing gene expression of key ion channels (Hcn4) and gap junctions (Cx43).
  • Analyzing Ca2+ transient propagation and fibroblast proliferation.

Main Results:

  • Increased matrix stiffness (14 kPa) enhanced pacemaker cell automaticity, evidenced by rhythmic contractions and Ca2+ oscillations.
  • Stiffer matrices led to increased Hcn4 expression and decreased Cx43 expression.
  • Ca2+ transient propagation was slower on stiffer hydrogels, mimicking native tissue, and linked to fibroblast proliferation.
  • Culture on rigid plates resulted in irregular contractions and prolonged Ca2+ transient durations.

Conclusions:

  • Pacemaker cell automaticity is augmented by stiffer extracellular matrix substrates within the physiological range of myocardial elasticity.
  • This tunable hydrogel approach provides a physiologically relevant in vitro model for studying cardiac mechanoelectric feedback.
  • The findings offer a framework for investigating heart rhythm regulation and the role of fibrosis in cardiac disease.