What Is Threshold in Muscle Contraction

Note: These activities involve the application of electrical currents to the muscle through electrodes placed on the skin. People who have pacemakers or who suffer from neurological or heart diseases should not volunteer for these activities. Muscle contraction and sensations (such as tingling or short discomfort) may be associated with nerve stimulation. If the volunteer feels very uncomfortable during the activities, stop the exercise immediately. Question: When the current has reached the following stages, what proportion of the fibers in the muscle has contracted?: Students learn practically by applying electrodes to their own body and electrically stimulating the nerves in their forearm to demonstrate muscle recruitment. The answer depends on the students` own data. At 0 mA, there can be no measurable response. Usually, the first contraction begins around 4-6 mA and the maximum contraction force begins around the range of 12-15 mA. Teach your students a lesson they will never forget with the Muscle Twitch Response Experience. Engage your students and improve their understanding of how nerve stimulation controls muscle contraction in this memorable active learning experience where students perform nerve stimulation on themselves. In these activities, students stimulate the ulnar nerve at the elbow or wrist and record muscle activity (compound muscle action potential) and the digiti minimi abductor. There are three main types of skeletal muscle fibers. These are called rapid contractions, slow contractions and intermediate stage.

In general, fast-twitch fibers produce high strength for short periods of time. Slow-twitch fibers produce less force, but can do so over longer periods of time. Intermediate fibers have certain properties of fast and slow contraction fibers. Fast-twitch fibers are also known as type II fibers. Fast-twitch fibers are the predominant fibers in the body. They react quickly to stimuli and can generate a lot of power. They have a large diameter due to the large amount of myofibrils. Their activity is driven by ATP, which is produced from anaerobic metabolism.

Slow-twitch fibers react much more slowly to stimuli than fast-twitch fibers. They have a smaller diameter and contain a large number of mitochondria. They are able to maintain long contractions and get their ATP from aerobic metabolism. Slow-twitch fibers are surrounded by capillary networks that provide oxygen-rich blood for use in aerobic energy systems. They also contain a red pigment called myoglobin. Myoglobin can bind oxygen (like hemoglobin) and provide a large oxygen reserve. Due to the reddish color of myoglobin, these fibers are often called red muscle fibers. Slow-twitch fibers are also known as type I fibers. Intermediate fibers resemble fast-twitch fibers in that they contain small amounts of myoglobin. They also have a capillary network around them and don`t get tired as easily as fast-twitch fibers. They contain more mitochondria than fast contractions, but not as much as slow-twitch fibers.

The speed of contraction and endurance is also between fast and slow contraction fibers. Intermediate fibers are also called type IIa fibers. Muscles that have a predominance of slow fibers are sometimes called red muscles as in the back and in the leg areas. Similarly, muscles that have a predominance of fast fibers are called white muscles. Interestingly, there are no slow-twitch fibers in the eye muscles or hand muscles. The law of all or nothing was first described in 1871 by physiologist Henry Pickering Bowditch. In his descriptions of heart muscle contraction, he explains: “An induction shock produces a contraction or does not do so depending on its strength; If it does this, it produces the greatest contraction that can be produced by any stimulus force in the state of the muscle at that time. “If the contracting muscle is stimulated again before the end of the relaxation phase of a muscle contraction, the next contraction creates greater strength or tension. This is called wave summation. The increase in the frequency of muscle stimulation leads to sustained strength generation.

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