Athena Vale
Muscle tetanus is a sustained muscle contraction that occurs when a muscle's motor unit is stimulated by multiple impulses at a sufficiently high frequency. This is also known as a tetanic contraction, tetanized state, or physiologic tetanus. During this state, a motor unit has been maximally stimulated by its motor neuron and remains that way for some time. This is different from a twitch, where the activity of the muscle is so brief that the contractile elements cannot extend the elastic elements completely before relaxation begins.
| Characteristics | Values |
|---|---|
| Muscle contraction | Sustained |
| Motor nerve | Emits action potentials at a very high rate |
| Motor unit | Maximally stimulated by motor neuron |
| Stimulus | Multiple impulses at a high frequency |
| Stimulus rate | 50-100 Hz |
| Muscle tension | Remains constant |
| Muscle length | Can shorten, lengthen or remain constant |
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What You'll Learn
Twitching and tetanus responses
A muscle contraction produced by a single action potential is a twitch. During a twitch, the activity of the muscle is so brief that the contractile elements cannot extend the elastic elements completely before relaxation begins; as a result, the tension at the ends of the muscle does not reach the maximum possible level.
A sustained contraction is produced by the summation of the tension of multiple frequent action potentials. Each stimulus causes a twitch. If the stimuli are delivered slowly enough, the tension in the muscle will relax between successive twitches.
Tetany is produced with a high-frequency stimulus (50-100 Hz), where no relaxation occurs between stimuli. This is called fused tetanus, and it occurs when there is no relaxation of the muscle fibres between stimuli during a high rate of stimulation. During this state, a motor unit has been maximally stimulated by its motor neuron and remains that way for some time.
During tetanus, the activity of the contractile elements is maintained, and they can eventually shorten enough to extend fully the series of elastic elements. When this has been accomplished, the maximum tension is apparent at the ends of the muscle. The force developed by a muscle, whether it is contracting or resting, is strongly dependent on the length of the muscle.
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Fused tetanus
A tetanic contraction (also called tetanized state, tetanus, or physiologic tetanus) is a sustained muscle contraction evoked when the motor nerve that innervates a skeletal muscle emits action potentials at a very high rate. During this state, a motor unit has been maximally stimulated by its motor neuron and remains that way for some time. This occurs when a muscle's motor unit is stimulated by multiple impulses at a sufficiently high frequency. Each stimulus causes a twitch. If stimuli are delivered slowly enough, the tension in the muscle will relax between successive twitches.
During a tetanus, the activity of the contractile elements is maintained, and they can eventually shorten enough to extend fully the series of elastic elements. When this has been accomplished, the maximum tension is apparent at the ends of the muscle. The force developed by a muscle, whether it is contracting or resting, is strongly dependent on the length of the muscle.
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Muscle tone
During a tetanic contraction, the motor unit has been maximally stimulated by its motor neuron and remains that way for some time. Each stimulus causes a twitch, and if the stimuli are delivered slowly enough, the tension in the muscle will relax between successive twitches. However, if the stimuli are delivered at a high enough frequency, no relaxation occurs between stimuli, and this is known as fused tetanus.
Fused tetanus occurs when there is no relaxation of the muscle fibres between stimuli, and it is the strongest single-unit twitch in contraction. During this state, the contracting tension in the muscle remains constant, and the muscle can shorten, lengthen, or remain at a constant length. For example, when holding up a heavy box, or maintaining a crouching position, some muscles require sustained contraction to hold the position.
The force developed by a muscle, whether it is contracting or resting, is strongly dependent on the length of the muscle. During a tetanus, the activity of the contractile elements is maintained, and they can eventually shorten enough to extend fully the series of elastic elements. When this has been accomplished, the maximum tension is apparent at the ends of the muscle.
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Muscle length
Muscle tetanus is a sustained muscle contraction that occurs when a muscle's motor unit is stimulated by multiple impulses at a high frequency. During this state, a motor unit has been maximally stimulated by its motor neuron and remains that way for some time.
The length of a muscle can also affect the type of contraction that occurs. For example, during a fused tetanus, there is no relaxation of the muscle fibres between stimuli, and the contracting tension in the muscle remains constant. This occurs when the muscle is stimulated at a high rate. The length of the muscle can be shortened, lengthened, or remain constant during a fused tetanus.
Additionally, muscles often exhibit some level of tetanic activity to maintain posture. For example, in a crouching position, some muscles require sustained contraction to hold the position. This results in a constant muscle length.
Overall, the length of a muscle plays a crucial role in achieving muscle tetanus and determining the force developed by the muscle.
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Motor unit stimulation
Muscle tetanus is a sustained muscle contraction that occurs when a muscle's motor unit is stimulated by multiple impulses at a sufficiently high frequency. Each stimulus causes a twitch, and if the stimuli are delivered slowly enough, the tension in the muscle will relax between successive twitches.
During a fused tetanic contraction, the contracting tension in the muscle remains constant in a steady state. This is the maximal possible contraction, where the muscle fibres are fully extended and the maximum tension is apparent at the ends of the muscle. The force developed by the muscle during a fused tetanus is dependent on the length of the muscle, with shorter muscles generating more force.
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Frequently asked questions
Muscle tetanus is a sustained muscle contraction that occurs when the motor nerve that innervates a skeletal muscle emits action potentials at a very high rate.
Muscle tetanus is achieved when a muscle's motor unit is stimulated by multiple impulses at a sufficiently high frequency.
A twitch is when the activity of the muscle is so brief that the contractile elements cannot extend the elastic elements completely before relaxation begins, resulting in the tension at the ends of the muscle not reaching the maximum possible level. During muscle tetanus, on the other hand, the activity of the contractile elements is maintained, and they can eventually shorten enough to extend fully the series of elastic elements, resulting in maximum tension at the ends of the muscle.
The force developed by a muscle, whether it is contracting or resting, is strongly dependent on the length of the muscle.
Fused tetanus is when there is no relaxation of the muscle fibres between stimuli and it occurs during a high rate of stimulation.
