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Related Concept Videos

Smooth Muscle Contraction01:25

Smooth Muscle Contraction

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...
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...
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...
Muscle Contraction01:10

Muscle Contraction

In skeletal muscles, acetylcholine is released by nerve terminals at the motor endplate—the point of synaptic communication between motor neurons and muscle fibers. The binding of acetylcholine to its receptors on the sarcolemma allows entry of sodium ions into the cell and triggers an action potential in the muscle cell. Thus, electrical signals from the brain are transmitted to the muscle. Subsequently, the enzyme acetylcholinesterase breaks down acetylcholine to prevent excessive muscle...
Muscle Contraction01:15

Muscle Contraction

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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Related Experiment Video

Updated: Jun 14, 2026

Ex Vivo Assessment of Contractility, Fatigability and Alternans in Isolated Skeletal Muscles
14:02

Ex Vivo Assessment of Contractility, Fatigability and Alternans in Isolated Skeletal Muscles

Published on: November 1, 2012

Changes in MR diffusion properties during active muscle contraction in the calf.

Yoshikazu Okamoto1, Akira Kunimatsu, Tatsuo Kono

  • 1Department of Radiology, Institute of Clinical Medicine, University of Tsukuba Hospital, Tsukuba, Ibaraki, Japan. yokamoto@md.tsukuba.ac.jp

Magnetic Resonance in Medical Sciences : MRMS : an Official Journal of Japan Society of Magnetic Resonance in Medicine
|March 27, 2010
PubMed
Summary

Muscle diffusion properties change with contraction. Fractional anisotropy (FA) increased in the gastrocnemius medialis, while perfusion and temperature changes influenced both gastrocnemius medialis and anterior tibialis muscles.

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Intact Short, Intermediate, and Long Skeletal Muscle Fibers Obtained by Enzymatic Dissociation of Six Hindlimb Muscles of Mice: Beyond Flexor Digitorum Brevis
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Intact Short, Intermediate, and Long Skeletal Muscle Fibers Obtained by Enzymatic Dissociation of Six Hindlimb Muscles of Mice: Beyond Flexor Digitorum Brevis

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Quantitative Magnetic Resonance Imaging of Skeletal Muscle Disease
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Quantitative Magnetic Resonance Imaging of Skeletal Muscle Disease

Published on: December 18, 2016

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Last Updated: Jun 14, 2026

Ex Vivo Assessment of Contractility, Fatigability and Alternans in Isolated Skeletal Muscles
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Ex Vivo Assessment of Contractility, Fatigability and Alternans in Isolated Skeletal Muscles

Published on: November 1, 2012

Intact Short, Intermediate, and Long Skeletal Muscle Fibers Obtained by Enzymatic Dissociation of Six Hindlimb Muscles of Mice: Beyond Flexor Digitorum Brevis
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Intact Short, Intermediate, and Long Skeletal Muscle Fibers Obtained by Enzymatic Dissociation of Six Hindlimb Muscles of Mice: Beyond Flexor Digitorum Brevis

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Quantitative Magnetic Resonance Imaging of Skeletal Muscle Disease
09:30

Quantitative Magnetic Resonance Imaging of Skeletal Muscle Disease

Published on: December 18, 2016

Area of Science:

  • Musculoskeletal imaging
  • Diffusion tensor imaging
  • Muscle physiology

Background:

  • Diffusion tensor imaging (DTI) provides insights into tissue microstructure.
  • Understanding muscle diffusion changes during contraction is crucial for biomechanics and clinical applications.

Purpose of the Study:

  • To investigate alterations in muscle fiber diffusion properties between rest and active contraction using DTI.
  • To quantify changes in fractional anisotropy (FA) and eigenvalues during muscle activity.

Main Methods:

  • 10 healthy volunteers underwent DTI scans of their calves at rest and during plantar flexion.
  • Fractional anisotropy (FA) and eigenvalues (lambda1, lambda2, lambda3) were measured in gastrocnemius medialis (GCM) and anterior tibialis (AT) muscles.
  • Ratios of FA and eigenvalues between contracted and resting states were calculated and compared.

Main Results:

  • Gastrocnemius medialis (GCM) showed increased FA and elevated lambda1 and lambda2 ratios post-contraction.
  • Anterior tibialis (AT) exhibited decreased lambda1 and lambda2 ratios during elongation.
  • Statistically significant differences were observed in GCM's FA, lambda1, and lambda2, and AT's lambda1 and lambda2.

Conclusions:

  • Elevated FA and eigenvalue values in contracted muscles suggest microscopic morphological changes.
  • Changes in focal temperature and perfusion are implicated in the observed diffusion alterations.
  • Perfusion significantly affects the AT, while focal perfusion and temperature influence the GCM.