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The process by which muscle fibres produce voltage is known as excitation-contraction coupling (ECC). ECC involves the electrical depolarisation of muscle fibres, which leads to muscle contraction. This process has been understood since the 18th century, but recent advances in electrical and optical measurements have provided an elegant view of ECC in skeletal muscle. Studies have demonstrated a close correlation between the voltage sensor charge movement and just-detectable contractile activation of muscle fibres.
| Characteristics | Values |
|---|---|
| Process by which muscle fibre electrical depolarisation is linked to activation of muscle contraction | Excitation-contraction coupling (ECC) |
| Understanding of ECC | Dates back to the 18th century |
| Depolarising pulses that produce detectable muscle fibre movement | Displace a set amount of charge |
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What You'll Learn
Excitation-contraction coupling (ECC)
The process by which muscle fibre electrical depolarisation is linked to the activation of muscle contraction is known as excitation-contraction coupling (ECC). ECC was first described by Galvani in the eighteenth century, but our understanding of the process has increased enormously since then.
ECC involves the movement of charge during depolarisation, which is an essential prerequisite for the release of SR Ca2+. This release is activated by depolarising pulses, which produce a detectable muscle fibre movement. The amount of charge that is moved can be termed the 'pre-activating' charge, as it must be moved prior to the steps that actually activate contraction.
The relationship between the peak rate of Ca2+ release and the activating charge moved in the same pulse has been studied empirically. It has been found that the time needed to reach the contractile threshold can be decreased by applying prepulses. This demonstrates a close correlation between the voltage sensor charge movement and just-detectable contractile activation of muscle fibres.
ECC in skeletal muscle has been studied using electrical and optical measurements, such as muscle fibre voltage clamp, as well as electron microscopy to reveal structural details. This has provided an elegant view of ECC in skeletal muscle.
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Depolarizing pulses
The process by which muscle fibre electrical depolarisation is linked to the activation of muscle contraction is known as excitation-contraction coupling (ECC).
Depolarising pulses produce a just-detectable muscle fibre movement by displacing a set amount of charge, known as the "pre-activating" charge. This is because the charge must move in order to attain detectable fibre activation. The pre-activating charge moves during depolarisation, but prior to the charge for the actual activation step in the control mechanism for Ca2+ release.
The shortening of the test pulse duration for just-detectable contraction can be predicted from the charge movement recordings as the time to move the prepulse charge at the test pulse voltage. Studies have demonstrated a close correlation between the voltage sensor charge movement and just-detectable contractile activation of muscle fibres. The charge required to attain a just-detectable contraction is the pre-activating charge, which must be moved in a step or sequence of steps prior to the step(s) that actually activate contraction, but it does not itself activate contraction.
In addition, the empirical (linear) relationship between the peak rate of Ca2+ release produced by a given pulse and the activating charge moved in the same pulse has been considered.
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Pre-activating charge
The process by which muscle fibre electrical depolarisation is linked to the activation of muscle contraction is known as excitation-contraction coupling (ECC).
Depolarising pulses that produce a just-detectable muscle fibre movement displace a set ("threshold") amount of charge, which can be termed "pre-activating" charge. This is because it must move in order to attain detectable fibre activation. Pre-activating charge moves during depolarisation, but prior to the charge for the actual activation step in the control mechanism for Ca2+ release.
The pre-activating charge is an essential prerequisite for depolarisation-activated SR Ca2+ release. It is also closely correlated with the voltage sensor charge movement and just-detectable contractile activation of muscle fibres.
The charge required to attain a just-detectable contraction is termed "pre-activating" charge since it must be moved in a step or sequence of steps prior to the step(s) that actually activate contraction. However, it does not itself activate contraction.
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Charge movement
The process by which muscle fibre electrical depolarisation is linked to the activation of muscle contraction is known as excitation-contraction coupling (ECC). An appreciable fraction of the total charge movement that is recorded from a fibre is pre-activating charge, which moves during depolarisation, but prior to the charge for the actual activation step in the control mechanism for Ca2+ release. The charge required to attain a just-detectable contraction is termed 'pre-activating' charge since it must be moved in a step or sequence of steps prior to the step(s) that actually activate contraction, but it does not itself activate contraction.
Depolarising pulses that produce a just-detectable muscle fibre movement displace a set ('threshold') amount of charge. Charge movement is recorded during muscle fibre depolarisation to indicate voltages. The shortening of the test pulse duration for just-detectable contraction could be predicted from the charge movement recordings as the time to move the prepulse charge at the test pulse voltage. These studies demonstrated a close correlation between the voltage sensor charge movement and just-detectable contractile activation of muscle fibres.
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Calcium release
The process by which muscle fibre electrical depolarisation is linked to the activation of muscle contraction is known as excitation-contraction coupling (ECC). ECC was first described by Galvani in the eighteenth century, and since then, advances in electrical and optical measurements have allowed for a better understanding of the phenomenon.
The peak rate of Ca2+ release produced by a given pulse can be related to the activating charge moved in the same pulse. The charge required to attain a just-detectable contraction is termed 'pre-activating' charge, as it must be moved in a step or sequence of steps prior to the steps that actually activate contraction. However, it does not itself activate contraction.
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Frequently asked questions
Excitation-contraction coupling (ECC).
Pre-activating charge.
The empirical (linear) relationship.
