08 Jan Muscle – Functional Anatomy

Muscles

Functional Anatomy

Muscles are most easily described as a series of bundles of muscle fibres. These fibres are in turn made up of a series of myofibrils which are composed of sacromeres lined up end to end. These sacromeres are the vital component of the muscle, the functional contractile element of the muscle, whose function is to actively produce the force which the muscle is present for.

Actin and myosin are the proteins present in the sarcomere that help this functional component. Unlike sarcomeres than are lined up end to end, these filaments like parallel to one another and when the muscle shortens through contraction the actin filament slides over the myosin and allows shortening. Although small, the sheer volume of sacromeres allows substantial change in length.

“The sliding filament theory explains the mechanism of muscle contraction based on muscle proteins that slide past each other to generate movement. According to the sliding filament theory, the myosin (thick filaments) of muscle fibers slide past the actin (thin filament) during muscle contraction, while the two groups of filaments remain at relatively constant length.”

The energy we get from the food we consume is stored chemically within ATP (Adeninine Triphosphate) and as it is converted to ADP (Adeninine Diphosphate) it produces chemical energy that converts to mechanical force. The volume of force that can be produced by the muscle is affected by:

1. The number of cross bridges
2. The time available for these to form and exert force
3. Type of contraction i.e. muscle lengthening, shortening or not changing

An understanding of these functions is vital to understanding muscle behavior. We will discuss this more in coming days.