Muscle contraction fibre types

In contrast, skeletal muscle contraction is more rapid than that of smooth muscle but skeletal muscle cannot maintain the same tone for long periods of time. As indicated in Table 7.1, we can distinguish sub-types of muscle fibre within... 

The function of muscle is to generate a force on contraction, either to maintain or change the position of a joint. There are two main types of muscle fibres Type 1 (slow twitch), which allow sustained low energy contraction, and Type 2 (fast twitch), which allow rapid forceful contractions. Muscles are comprised of varying proportions of both types of fibres. Postural muscles are composed mainly of Type 1 fibres, with a predominantly linear arrangement of fibres, whereas non-postural muscles... 

By selecting specific muscle types the authors were able to separate different myofibrillar protein types slow-contracting, fast-contracting and heart. Since each muscle fibre type contains its own specific myosin chain, the gelation properties of fractions prepared from them vary. In fact, most muscles contain a mixture of both types of myosin, as well as a third (fast-contracting) type. Salt was required to produce gels however, once... 

Modern representations of the virtual heart, therefore, describe structural aspects like fibre orientation in cardiac muscle, together with the distribution of various cell types, active and passive electrical and mechanical properties, as well as the coupling between cells. This then allows accurate reproduction of the spread of the electrical wave, subsequent contraction of the heart, and effects on blood pressure, coronary perfusion, etc. It is important to point out, here, that all these parameters are closely interrelated, and changes in any one of them influence the behaviour of all others. This makes for an exceedingly complex system. 

In the periphery at the mammalian neuromuscular junction each muscle fibre is generally influenced by only one nerve terminal and the one NT acts on one type of receptor localised to a specific (end-plate) area of the muscle. The system is fitted for the induction of the rapid short postsynaptie event of skeletal muscle fibre contraction and while the study of this synapse has been of immense value in elucidating some basic concepts of neurochemical transmission it would be unwise to use it as a universal template of synaptic transmission since it is atypical in many respects. 

In the cells of this tissue, which are known as fibres, the two major proteins, actin and myosin, are orgaiused to form myofibrils. These are structural rods that can contract (Figure 1.11). This enables muscle cells to shorten, which provides for movement and locomotion (Figure 1.12). There are three types ... 

Smooth muscles can be divided into two main groups phasic and tonic muscle types. Phasic muscle, e.g. taenia coli, exhibits spontaneous action potentials and have faster contractile kinetics whereas tonic muscle, e.g. the aorta, do not have spontaneous activity and contract more slowly (cf. Somlyo and Somlyo 1968, Horiuti et al. 1989). Comparative studies have revealed that the shortening velocity of smooth muscles span of over a wide range (Malmqvist and Arner 1991). A fast smooth muscle, e.g. rabbit rectococcygeus, can have a shortening velocity that is about 7-fold faster than that of a slow smooth muscle, e.g. the aorta. This difference in velocity is similar to that between fast and slow skeletal muscle fibres. Thus smooth muscle is a heterogeneous group of muscles with a span of different kinetic properties in their contractile systems. 

The third type of muscle is that found in the heart. This shows some striated fibres under the microscope but is not under voluntary control and is not entirely dependent on its nerve supply. A pacemaker within the heart muscles produces, at a rate appropriate to the body s need for oxygen, electrical impulses which cause the heart muscles to contract thus producing heart beats. 

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