What is a simple twitch? What are the stages of a simple twitch? What does a simple twitch look like?

What does a simple twitch look like:


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What is a simple twitch:
A simple muscle twitch is when the muscle contracts and relaxes. It takes a tenth of a second for the contraction to reach it’s maximum height and about .3 seconds for the entire action to be completed.

-Alternative Names
Muscle fasciculation; Fasciculations of muscle

-Definition
Muscle twitches are fine movements of a small area of muscle.

-Considerations
Muscle twitching is the result of minor local muscle contractions or the uncontrollable twitching of a single muscle group served by a single motor nerve fiber or filament.

Muscle twitches are minor and often go unnoticed. Some are common and normal, while others indicate a neurologic disorder.

-Causes
  • Benign twitches (not caused by disease or disorders)
o Often affecting the eyelids, calf, or thumb
o Normal and quite common, often triggered by stress or anxiety
  • A diet deficiency
  • Drug overdose (caffeine)
  • Drug side effect (such as diuretics, corticosteroids and estrogens)
  • Exercise
  • Exhaustion

Symptoms suggestive of a neurological cause of fasciculations include:
  • Wasting of muscle
  • Weakness
  • Other findings of nerve dysfunction

Neurological illnesses where fasciculations are seen include:
  • Chronic denervation of muscle due to disk compression of nerve exiting the spinal cord
  • ALS (Lou Gehrig's disease)
  • Spinal muscular atrophy
  • Muscular dystrophy
  • Myopathy
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Stages of a Simple Twitch:
-A simple twitch can be divided into a
latent period, a contraction phase, and a relaxation phase

1.The latent period begins at stimulation and typically lasts about two milliseconds. Over this period, the action potential sweeps across the sarcolemma and the sarcoplasmic reticulum releases calcium ions. The muscle fiber does not produce tension during the latent period, because the contraction cycle has yet to begin. The time it takes the muscle to react to the stimulus is called the latent period.

2.In the contraction phase, tension rises to a peak. As tension rises, calcium ions are binding to troponin, active sites on thin filaments are being exposed, and cross-bridge interactions are occurring. The contraction phase ends roughly fifteen milliseconds after stimulation. The contraction period is the time where the muscle is actually contracting.

3.The relaxation phase then continues for about another twenty-five milliseconds. During this period, calcium levels are falling, active sites are being covered by tropomyosin, and the number of active cross-bridges is declining. The last period is when the muscle length returns back to normal.