• Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

The Structure of Skeletal Muscle.

Extracts from this document...

Introduction

The Structure of Skeletal Muscle Skeletal muscles are all muscles that are attached to the skeleton such as the biceps and the hamstring. Within each muscle cell (also known as a muscle fibre) are structures called myofibrils as shown in the picture below: (Ref. The picture above was found at www.google.com) Myofibrils are made up of tiny units called sarcomeres. Sarcomeres are the smallest structures in a muscle that can contract; they are long filament-like structures, arranged in series - end to end - that run lengthways in the myofibril. Within the sarcomeres are two types of protein filaments that are actin and myosin - running lengthways, parallel to each other. The myosin filaments have 'cross-bridges' across to the actin filaments, which during contraction allow them to bond with the actin filaments. The source of energy for this bonding is the molecule adenosine triphosphate (ATP). During the bonding, energy is released by the breaking down of ATP into adenosine diphosphate (ADP) and Pi at another site - the ATPase site - on the myosin cross-bridge (by the action of the enzyme ATPase). ...read more.

Middle

A picture of skeletal muscle is as follows: (www.google.com) Motor Neurone The Motor Neurone forms synaptic junctions with either extrafusal muscle fibres (skeletal muscle) or intrafusal muscle fibres (thread-like muscle that adjusts tension). Stimulation of these motor neurones induces contraction or shortening of the muscle fibres. Alpha motor neurones induce the contraction of extrafusal muscle fibres upon stimulation, whereas gamma motor neurones induce the contraction of intrafusal muscle fibres upon stimulation. Alpha motor neurones control muscle contraction involved in voluntary movement, whereas gamma motor neurones control muscle contraction in response to external forces acting on the muscle. In response to these external forces, the gamma motor neurones induce the involuntary, reflexive movement called the stretch reflex. Intrafusal motor neurones adjust the length of intrafusal muscle fibres to maintain an appropriate level of tension on the muscle spindle receptor. The control of intrafusal muscle fibres occurs independently of the length of skeletal muscle fibres. This independent function allows the spindle to maintain a high degree of sensitivity over a wide range of muscle lengths, and in effect acts as a means of encoding muscle length. ...read more.

Conclusion

FT fibres are brought into play by either the effort to more a heavy load or by the need to move an object faster than is possible with ST fibres. Type IIB fibres can twitch three times faster (and therefore, more often) than ST fibres. Type IIAs can also twitch faster and more often than ST fibres. Because of this, and the recruitment pattern, a FT fibre may begin its contraction after a ST fibre but actually finish at the same time or before. This leads to another contributor to the FT fibres abilities to produce greater force - their enhanced frequency of firing. Because they complete the firing sequence more quickly they can fire more often than ST fibres, thus developing more tension. The force developed by a muscle depend on the number of fibres that are forced to contract (the more units contracting, the more force developed). A sudden increase in force is met by the involvement of more motor units. So a weight lifter will be using more motor units than a cross-country runner at any one time. If the weight lifter increased his weights to a degree that the units are under fatigue then they will increase the frequency of firing therefor meeting the muscles demand. 1 ...read more.

The above preview is unformatted text

This student written piece of work is one of many that can be found in our AS and A Level Anatomy & Physiology section.

Found what you're looking for?

  • Start learning 29% faster today
  • 150,000+ documents available
  • Just £6.99 a month

Not the one? Search for your essay title...
  • Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

See related essaysSee related essays

Related AS and A Level Anatomy & Physiology essays

  1. Btec sport, skeletal system

    Cardiac muscle Your heart is made of cardiac muscle. This type of muscle only exists in your heart. Unlike other types of muscle, cardiac muscle never gets tired. It works automatically and constantly without ever pausing to rest. Cardiac muscle contracts to squeeze blood out of your heart, and

  2. Physiology Within Sport

    increased rapidly and then after the 3 minutes the heart rate begins to plateaux, however with each client there initial heart rate increases rapidly this is where the heart would be pumping excessively to increase the Venous Return, however it then slightly plateaux's then slightly increases again where it would plateaux for the duration of the exercise.

  1. Health screening questionnaire and muscle analysis of two individuals

    Mine was 121/59 which is average. P4/M2 The males results show what he is healthy and the right weight for his age. He does have more skeletal muscle in his body but he has not enough body fat mass. His lean balance in both his arms is over which he

  2. Anatomy and Physiology.

    However the knee is not capable of moving in a circle at all. Circumduction is actually a sequence of flexion, abduction, extension, and adduction. Abduction: Abduction is movement of a body part away from the midsagittal line, which is the midline of the body, which runs vertically and divides into equal right and left halves.

  1. The skeletal system in the body and what it does within the body

    After understanding the importance of bone structure for its function I was then better able to expand and clearly understand my knowledge of the relationship between bones and the complementary type of joint in providing an appropriate means of movement.

  2. A level Project, Personal Exercise Program on Netball.

    (10) The performer carried out fitness tests to show pre and post exercise program muscular abilities. Athletes use fitness tests to monitor the progress of their condition. A fitness test motivates the performer to start and continue exercising. You can compare the results of a fitness test to own prior results or to a set of norms i.e.

  1. Cardiovascular responses When or before exercising, a number of changes happen within the ...

    Although the muscle fibers of a given motor unit tend to be located near one another, motor units have overlapping areas. To sustain muscle contraction, the motor units must be repeatedly activated (John V Basmajian). As the firing rates of motor units active in a contraction increase, the twitches connected with each firing will eventually combine to produce large forces.

  2. Movement within the Body and the Cardiovascular System

    Trachea The air then travels to the trachea; this is a passage tube on average around 12 cm long and about 2.5 cm wide. The trachea is kept open by ring of cartilage its physically appears to be shaped like a horseshoe.

  • Over 160,000 pieces
    of student written work
  • Annotated by
    experienced teachers
  • Ideas and feedback to
    improve your own work