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Related Concept Videos

Actin and Myosin in Muscle Contraction01:16

Actin and Myosin in Muscle Contraction

11.6K
Actin and myosin are contractile proteins that form the sarcomere found in skeletal muscle tissues for regulating muscle contraction. Actin, a globular contractile protein, interacts with myosin for muscle contraction. The skeletal tissue appears striped or striated under a microscope due to the repeated arrangement of contractile proteins actin and myosin along the length of myofibrils. Dark A bands and light I bands repeat along myofibrils, and the alignment of myofibrils in the cell causes...
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The Sarcomere01:08

The Sarcomere

8.1K
A sarcomere is a microscopic segment repeating in a myofibril. The sarcomere fundamentally consists of two main myofilaments: thick filaments called myosin and thin filaments called actin. These filaments interact by sliding past each other in response to stimulus. In addition to myosin and actin, several other proteins, such as tropomyosin, troponin, titin, nebulin, myomesin, α-actinin, and dystrophin, play crucial roles in regulating, structuring, and functioning of the sarcomere.
Each...
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Cross-bridge Cycle01:26

Cross-bridge Cycle

117.5K
As muscle contracts, the overlap between the thin and thick filaments increases, decreasing the length of the sarcomere—the contractile unit of the muscle—using energy in the form of ATP. At the molecular level, this is a cyclic, multistep process that involves binding and hydrolysis of ATP, and movement of actin by myosin.
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Smooth Muscle Contraction01:25

Smooth Muscle Contraction

3.0K
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...
3.0K
Excitation-Contraction Coupling in Skeletal Muscles01:20

Excitation-Contraction Coupling in Skeletal Muscles

8.3K
Excitation-contraction coupling is a series of events that occur between generating an action potential and initiating a muscle contraction. It occurs at the triad, a structure found in skeletal muscle fibers that comprise a T-tubule and terminal cisternae of the sarcoplasmic reticulum on each side. These triads are visible in longitudinally sectioned muscle fibers. They are typically located at the A-I junction — the junction between the A and I bands of the sarcomere.
When an action...
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The Role of Actin and Myosin in Non-muscle Cells01:10

The Role of Actin and Myosin in Non-muscle Cells

3.5K
Actin and myosin or actomyosin filaments also play a significant role in cells other than those involved in muscle contraction (which occurs within the sarcomere of muscle cells). The mechanism of non-muscle cell contractile bundles was first observed in Dictyostelium and Acanthamoeba. In non-muscle cells, two bundles are commonly found: stress fibers and actomyosin adherence belts. These contractile bundles are smaller and less organized than the ones found in muscle cells. They  are held...
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Related Experiment Video

Updated: Jul 9, 2025

Isolating Myofibrils from Skeletal Muscle Biopsies and Determining Contractile Function with a Nano-Newton Resolution Force Transducer
07:55

Isolating Myofibrils from Skeletal Muscle Biopsies and Determining Contractile Function with a Nano-Newton Resolution Force Transducer

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Titin-based force regulates cardiac myofilament structures mediating length-dependent activation.

Anthony L Hessel1, Michel N Kuehn1, Nichlas M Engels2

  • 1Institute of Physiology II, University of Muenster; Muenster, Germany.

Biorxiv : the Preprint Server for Biology
|November 28, 2023
PubMed
Summary

The Frank-Starling mechanism, crucial for heart function, is supported by titin

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In Vitro Assessment of Cardiac Function Using Skinned Cardiomyocytes
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Probing Myosin Ensemble Mechanics in Actin Filament Bundles Using Optical Tweezers
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Related Experiment Videos

Last Updated: Jul 9, 2025

Isolating Myofibrils from Skeletal Muscle Biopsies and Determining Contractile Function with a Nano-Newton Resolution Force Transducer
07:55

Isolating Myofibrils from Skeletal Muscle Biopsies and Determining Contractile Function with a Nano-Newton Resolution Force Transducer

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In Vitro Assessment of Cardiac Function Using Skinned Cardiomyocytes
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Probing Myosin Ensemble Mechanics in Actin Filament Bundles Using Optical Tweezers
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Probing Myosin Ensemble Mechanics in Actin Filament Bundles Using Optical Tweezers

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Area of Science:

  • Cardiovascular Physiology
  • Molecular Biology
  • Biophysics

Background:

  • The Frank-Starling law describes how increased heart preload enhances stroke volume.
  • This phenomenon is linked to molecular changes in sarcomere structure and calcium sensitivity.
  • Titin, a spring-like protein, is hypothesized to play a role by influencing myofilament structure.

Conclusions:

  • Titin plays a regulatory role in cardiac myofilament structure.
  • These structural regulations support the Frank-Starling mechanism.
  • The findings elucidate a key molecular aspect of cardiac adaptation.