Define the following terms: a) Treppe b) Muscle twitch Wave summation Incomplete tetanus C) Complete tetanus f) Motor unit g Recruitment
The correct answer and explanation is:
a) Treppe
Treppe is the phenomenon where muscle contractions become progressively stronger when a muscle is stimulated repeatedly at a set frequency, after an initial period of rest. This occurs because the muscle’s fibers have increased availability of calcium ions and other resources necessary for contraction. Initially, when a muscle is stimulated, each contraction is of the same strength. However, as the muscle is repeatedly stimulated, each contraction is slightly stronger than the last, leading to a step-like increase in tension.
b) Muscle Twitch
A muscle twitch is a brief, single contraction and relaxation cycle of a muscle fiber in response to a single stimulus. It occurs in three phases: the latent period, the contraction phase, and the relaxation phase. During the latent period, the muscle is receiving the stimulus but has not yet started contracting. The contraction phase follows, where the muscle shortens. Finally, in the relaxation phase, the muscle returns to its resting state.
c) Wave Summation
Wave summation refers to the increase in the strength of a muscle contraction when a muscle is stimulated repeatedly at a frequency greater than its relaxation time. If stimuli are provided rapidly enough, the muscle does not have time to fully relax between contractions, leading to a stronger, more sustained contraction. This summation of force is due to the increased availability of calcium ions, leading to more actin-myosin interactions.
d) Incomplete Tetanus
Incomplete tetanus occurs when a muscle is stimulated at a frequency that does not allow it to fully relax between stimuli. The muscle fibers contract and relax repeatedly, but the relaxation phase is partial. As a result, the muscle produces a sustained contraction that is stronger than a single twitch but not as strong as complete tetanus.
e) Complete Tetanus
Complete tetanus is the sustained maximal contraction of a muscle that results from continuous high-frequency stimulation, where the muscle does not relax at all between stimuli. This leads to a smooth, sustained contraction with maximal force. The tension generated in complete tetanus is the greatest because the muscle’s fibers are constantly contracted.
f) Motor Unit
A motor unit consists of a motor neuron and all the muscle fibers it innervates. The number of muscle fibers in a motor unit varies depending on the type of muscle and the precision required for its movements. Small motor units control fine motor movements, while larger motor units control gross motor functions.
g) Recruitment
Recruitment refers to the process by which additional motor units are activated to produce a stronger contraction. As the intensity of the stimulus increases, more motor units are recruited to assist in the contraction. This allows the muscle to generate more force in response to the demands placed on it.