● `color{violet}("Each muscle")` is made of many `color{violet}("long, cylindrical fibres")` arranged in parallel arrays.

● These `color{violet}("fibres")` are composed of numerous fine fibrils, called `color{brown}("myofibrils.")`

● `color{violet}("Muscle fibres")` contract (shorten) in response to stimulation, then relax (lengthen) and return to their uncontracted state in a `color{violet}("coordinated fashion.")`

● Their action moves the body to adjust to the changes in the environment and to maintain the positions of the various parts of the body.

● In general, `color{violet}("muscles")` play an active role in all the movements of the body.

● `color{violet}("Muscles")` are of three types, `color{brown}("skeletal, smooth, and cardiac.")`

● `color{brown}("Skeletal muscle")` tissue is closely attached to `color{violet}("skeletal bones.")`

● In a `color{violet}("typical muscle")` such as the `color{violet}("biceps, striated (striped) skeletal muscle fibres")` are bundled together in a parallel fashion.

● A sheath of tough `color{violet}("connective tissue encloses")` several bundles of `color{violet}("muscle fibres.")`

● The `color{brown}("smooth muscle")` fibres taper at both `color{violet}("ends (fusiform)")` and do not show striations.

● `color{violet}("Cell junctions")` hold them together and they are `color{violet}("bundled")` together in a connective tissue sheath.

● The wall of `color{violet}("internal organs")` such as the `color{violet}("blood vessels, stomach")` and intestine contains this type of `color{violet}("muscle tissue.")`

● `color{violet}("Smooth muscles")` are `color{violet}("‘involuntary’")` as their functioning cannot be directly controlled.

● We usually are not able to make it contract merely by thinking about it as we can do with `color{violet}("skeletal muscles.")`

● `color{brown}("Cardiac muscle tissue")` is a `color{violet}("contractile tissue")` present only in the heart.

● `color{violet}("Cell junctions")` fuse the `color{violet}("plasma membranes")` of `color{violet}("cardiac muscle cells ")` and make them stick together.

● `color{violet}("Communication junctions (intercalated discs)")` at some fusion points allow the cells to contract as a unit, i.e., when one cell receives a signal to contract, its neighbours are also stimulated to contract.