When baseline tension is observed at any one length, we wonder whether it is due to the active contraction of the muscle or to passive parallel elastic elements. Above rest length, the active tension also decreases (for a different reason), but this occurs in a region where the total tension increases, the difference being due to passive tension. Anything below rest length, i.e., the region in which active contractile tension decreases as a function of length, does not involve passive tension. Passive tension then increases as the muscle is stretched further. One simply looks for the point of maximal tension development as a function of length, which usually occurs at the point where passive tension just appears. In skeletal muscle it is easy to solve this problem.
What is the origin of this baseline tension? It may arise as the result of tonic activity in the muscle. The baseline pressure was approximately half the peak pressure of the wave. However, I noticed that the pressure baselines or, one might say, the tension baselines were high in Malin's, Morales’, and Barry's records. I do not think an active “drinking” is going to occur in the ureter. The controversy regarding active relaxation in skeletal muscle was settled years ago. Barr has implied that there is no evidence that muscles can actively relax. This discussion brings up the question of muscle tone. This damage then results in an imbalance between messages from the nervous system to the muscles causing altered excitability of this stretch reflex ( Britton, 2004). Disturbances in muscle tone occur when there is an imbalance in the excitatory and inhibitory input to motor neurons, which is caused by damage to the spinal cord and/or the CNS. Their relaxation is brought about via an inhibitory neuron within the spinal cord. While agonist muscles (prime movers) contract in response to stretching, antagonist (opposing) muscles must relax. Here the sensory neuron synapses (connects) with the motor neuron, and the transmitted impulse results in muscle contraction. When a muscle is stretched, an impulse is generated in the muscle spindle and is transmitted via the sensory neuron to the grey matter of the spinal cord. This tension is known as muscle tone and is ultimately controlled by impulses from the brain and nervous system and occurs through a mechanism known as the stretch reflex. Without this tension, we would not be able to maintain and control an upright posture and resist the force of gravity conversely, too much tension can lead to movement difficulties and other problems. Jane Chantry, Sarah Crombie, in Handbook of Electronic Assistive Technology, 2019 What Is Muscle Tone?Īll muscles maintain a level of residual tension or resistance to stretch, even when relaxed and at rest this enables them to respond and move quickly and easily when required.
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