able to: Understand what the components of a muscle fibres - - PDF document

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Neuromuscular Arrangement, Sliding Filament Theory Lecture 5

Image used with consent from McArdle, et al ., (2009)

Aims

By the end of the session you should be able to:

• Understand what the components of a muscle fibres
• Describe the sliding filament theory
• Describe the role of the sarcoplasmic reticulum.

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Muscle fibres

• Muscle development has occurred during the

embryonic stage.

• The number of muscle fibres are set before

you are born, muscle fibres can not divide after birth but can undergo hypertrophy.

• During growth Testosterone enables muscle

fibre growth. Muscle make up = Water = 75% , Protein = 20% and Salts and

• ther substances = 5% (McArdle, Katch and Katch, 2010)

Cross Section of a muscle

Muscle fibres are made up

• f myofibrils

Myofibrils are composed of thousands of sarcomeres joined together. These are stimulated at the same time to initiate contraction. The sarcomeres are surrounded by a coating called sarcoplasmic reticulum and t-tubules

Myofibrils / muscle fibres

Image used with consent from McArdle et al., (2009)

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Muscle cross section

Image used with consent from McArdle et al., (2009)

A sarcomere

Image used with consent from McArdle et al., (2009)

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PROPERTIES Allow user to leave interaction: Anytime Show ‘Next Slide’ Button: Show upon completion Completion Button Label: Next Slide

Sliding Filament Theory

• Huxely, 1954, Nobel prize winner
• During contraction the thin filaments (actin)

slide past thick filaments (myosin) so that the actin and myosin overlap.

• The Z lines are pulled towards the myosin
• The I bands shorten
• The H zone disappears
• A bands move more closely together but do

not diminish in length

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How?

 Signal from brain is passed down to sarcolemma from the axon terminals of a motor neuron.  This signal passes down through the t-tubules.  This stimulates the release of calcium from the sarcoplasmic reticulum.  Calcium then initiates the start of cross bridge formation

Sliding filament theory

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PROPERTIES On passing, 'Finish' button: Goes to Next Slide On failing, 'Finish' button: Goes to Next Slide Allow user to leave quiz: At any time User may view slides after quiz: At any time User may attempt quiz: Unlimited times

References. McArdle, W.D., Katch, F.L. & Katch, V.L., 2009. Exercise Physiology: Nutrition, Energy and Human Performance 7th ed., Lippincott Williams and Wilkins. Tortora, G.J. & Derrickson, B.H., 2008. Principles of Anatomy and Physiology 12th ed., John Wiley & Sons.