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Related Concept Videos

Actin and Myosin in Muscle Contraction01:16

Actin and Myosin in Muscle Contraction

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

Excitation-Contraction Coupling in Skeletal Muscles

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 potential...
Overview of Skeletal Muscle01:15

Overview of Skeletal Muscle

Skeletal muscles are composed of a bundle of muscle fibers and are attached to bones through tendons. Each skeletal muscle fiber is a single muscle cell. The sarcolemma, the plasma membrane of a skeletal muscle cell, consists of a lipid bilayer and glycocalyx that supports muscle fibers. The sarcolemma extends into the muscle cells to form tubular structures called transverse or T-tubules. Each side of the T-tubules consists of a membrane-bound structure called the sarcoplasmic reticulum,...
The Sarcomere01:08

The Sarcomere

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 myosin...
Motor Unit Stimulation01:20

Motor Unit Stimulation

When the neuron of a motor unit fires an action potential, it triggers a series of events, leading to a twitch contraction in the muscle fibers. The process of excitation-contraction coupling is crucial in relaying the action potential to the muscle fibers.
The latent period of contraction marks the onset of excitation-contraction coupling, when the action potential propagates across the sarcolemma, preparing the muscle fibers for contraction. As the fibers enter the contraction phase, the...
Relaxation of Skeletal Muscles01:29

Relaxation of Skeletal Muscles

The period of muscle contraction primarily influences the duration of stimulation at the neuromuscular junction (NMJ), the presence of free calcium ions in the sarcoplasm, and the availability of energy or ATP to support contractions.
When an action potential reaches the axon terminal, it depolarizes the membrane and opens voltage-gated sodium channels. Sodium ions enter the cell, further depolarizing the presynaptic membrane. This depolarization causes voltage-gated calcium channels to open.

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Ex Vivo Assessment of Contractility, Fatigability and Alternans in Isolated Skeletal Muscles
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Published on: November 1, 2012

Sarcomere dynamics during muscular contraction and their implications to muscle function.

Ivo A Telley1, Jachen Denoth

  • 1ETH Zurich, Institute for Biomechanics, HCI E 357.1, 8093 Zurich, Switzerland.

Journal of Muscle Research and Cell Motility
|May 29, 2007
PubMed
Summary

This study explores sarcomere inhomogeneity and length changes during muscle contraction. Understanding these dynamics is crucial for a comprehensive model of myofibril mechanics and force generation.

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Area of Science:

  • Muscle physiology
  • Biophysics
  • Skeletal muscle mechanics

Background:

  • Traditional muscle force generation models assume uniform sarcomere behavior.
  • Sarcomere inhomogeneity and length dynamics significantly impact force kinetics, especially during stretch/relaxation.
  • Existing models often overlook the role of internal strain redistribution.

Purpose of the Study:

  • To identify key aspects of sarcomere inhomogeneity and length dynamics in muscle contraction.
  • To understand myofibril mechanics as series-connected biological motors (half-sarcomeres).
  • To link force generation, crossbridge kinetics, and sarcomere movements for a comprehensive contraction model.

Main Methods:

  • Analysis of muscle contraction experiments.
  • Focus on mechanics of myofibrils and muscle fibers as independent units.
  • Review of studies on internal strain redistribution and sarcomere dynamics.

Main Results:

  • Sarcomere inhomogeneity and length dynamics are critical factors in muscle contraction.
  • Internal strain redistribution within myofibrils influences force generation.
  • Crossbridge kinetics are affected by sarcomere dynamics, challenging uniformity assumptions.

Conclusions:

  • A comprehensive myofibril contraction model requires integrating sarcomere inhomogeneity and dynamics.
  • Understanding half-sarcomere mechanics as series-connected motors is essential.
  • Future models must account for complex sarcomere movements and their link to force generation.