Muscle structure and Functions of the muscular systemIn this assignment I will look at the structure of the muscular system and the functions of it.

There are 3 types of muscles which are: Skeletal muscles Smooth muscle Cardiac muscle

Skeletal muscles are the muscles that move and support the skeleton. They make up fifty percent of your body weight. There are 640 individually named skeletal muscles. A skeletal muscle links two bones across its connecting joint. When these muscles contract or shorten, your bone moves. This type of muscle is a voluntary muscle which means it is under conscious control.

Smooth Muscle: This is an involuntary muscle that is moved with out thinking about the movement, These muscles work by functioning under the control of the nervous system which is located in the walls of the digestive system and blood vessels.

Cardiac Muscle: This muscle is found in the wall of the heart. It works continuously. This muscle is involuntary, which means it is not under conscious control. This muscle is made up of it’s own tissue which has it’s own blood supply.

Function of the muscular systemMuscle must cross the joint they move. When a muscle contracts it exerts a pulling force on the bone s causing them to move together around a joint.

In normal circumstances, muscles are in a state of partial contraction, ready to react to a stimulus from the nervous system, but without this muscle tone, the body would collapse and when a stimulus from the nerve supply occurs, muscle fibres work an all or nothing basis .

The strength of muscle contraction in response to the stimulus depends on the number of muscle fibres brought into use, a process known as muscle fibre recruitment . During exercise the muscles of an individual uses energy at a rate that is directly proportional to the intensity of the exercise . If the energy does not get replaced as it gets used up, the muscles are unable to maintain their work rate and you have to reduce the intensity of the activity or stop it.

Antagonist muscle pairsMuscles do not work in isolation, They are assembled in groups and work together to bring about movement, they act only by contracting and pulling.They are able to contract without shortening so hold a joint form and fixed in position.

When the contraction is over the muscle becomes soft but do not lengthen until stretched by the contraction of the opposite muscle.

Agonist: The muscle that shortens to move a joint is called the AGONIST or “Prime Mover”

Antagonist: The muscle that relaxes in opposition to the agonist is called the antagonist. This muscle is responsible for the opposite movement and the one that relaxes as the agonist works. If it did not relax, movement would not be able to take place. Antagonists exert a control over the movement .

Synergist- These muscles work together to enable the agonists to operate more effectively. They work with the agonists to control and direct movement by modifying or altering the direction of pull on the agonists to the most advantageous position.

Fixator: These muscles stop any unwanted movement throughout the whole body by fixing or stabilising the joint or joints involved. These muscles stabilise the origin so that the agonist can achieve maximum and effective contraction. An example of a fixator is riding a bike.

Fibre types

All skeletal muscles contain a mixture of fibre types , each individual has a mix of fibre types and these varies from muscle groups to muscle groups in the individual .There are two main type of striated skeletal muscle can be distinguished on the basis of the speed they conract, type 1 ( slow twitch and type 2 ( fast twitch).

Type 1 muscle fibresType 1 ( slow twitch) fibres contract slowly with less force. They are slow to fatigue and suited to longer duration of aerobic activities, theyt have a rich blood supply and contain many mitochondria to sustain aerobic respiration. An example of an activity that uses these fibres is a marathon runner and a long distance swimmer

Type 2a muscle fibres ( fast twitch fibres) are fast contracting and able to produce a great force, but are also resistant to fatigue , These fibres are suited to middle-distance events.

Type 2b muscle fibres also called fast twitch fibres contract rapidly and have the capacity to produce large amounts of force, but they fatigue more readily, making them better suited to anaerobic activity. These depend mostly on anaerobic metabolism and are recruited for high intensity and short duration activities such as a 100 metre sprint.

All types of muscle fibre are used in all types of activities although type 1 fibres are particularly adapted to low intensity aerobic endurance work, They are usually used at the beginning of exercises regardless of the intensity of the activity an example of an athlete with these fibres is Paula Radcliffe .

Type 2 fibres adapt to high intensity anaerobic exercise involving explosive or powerful movements but are increasingly employed as fatigue sets during low- intensity endurance work.