Download Muscle Physiology PPT

Muscle Physiology
Anatomy & Physiology/Tissues, Bones and Muscles
Muscle Functions

Muscles have four major roles in our bodies:
1.
2.
3.
4.
Produce movement
Maintain posture
Stabilize joints
Generate heat: a by-product of
muscle activity
Anatomy of a Muscle

To understand how muscles move, it is essential to understand their basic
anatomy.

The outermost layer of a muscle is called the epimysium, which is a very
tough connective tissue
Epimysium
Muscle Anatomy Continued…

Below the epimysium is another layer of connective tissue called the
perimysium, which covers bundles of muscle cells called a fascicle.
Fascicle
Perimysium
Epimysium
Anatomy of a Muscle Continued…

Each muscle fiber in the fascicle is wrapped by a thin connective tissue
called an endomysium.
Fascicle
Perimysium
Epimysium
Endomysium
Muscle Fibers

Successful muscle movement (contraction or relaxation of a muscle)
depends on a very organized coordination of many parts of the muscle.

A single muscle cell is often called a muscle fiber, because it is long and
contains multiple nuclei.
Myofibrils

A single muscle fiber is made of many myofibril organelles.
Actin and Myosin Filaments
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Each myofibril is made of a combination of actin filaments, which are thin,
and myosin filaments, which are thick.

The actin and myosin are arranged in repeating units called sarcomeres.
Parts of the Sarcomere

Each area of the sarcomere has a specific name, because these units are
essential for understanding how muscles contract and relax:

Thin (actin) filaments are attached to membranes called Z discs (or Z lines). A
full sarcomere extends from one Z disc to another.

A bands contain both thin (actin) and thick (myosin) filaments.

I bands contain only thin (actin) filaments and span parts of two sarcomeres.

Alternating light (I) and dark (A) bands give the myofibril a striped appearance.

The H zone contains only thick (myosin) filaments.
Muscle Movement

When muscles contract (shorten) the Z discs move closer together. This
means that the H zone becomes smaller and the the I bands shorten.

When muscle relax (lengthen), the Z discs move apart. The means that the H
zone becomes larger and the I bands get longer.
Muscle Movement Continued…

The movement of sarcomeres is controlled by crossbands that connect actin
and myosin.

These crossbands attach the myosin and actin filaments and use ATP as a
source of energy to slide the filaments across each other.

This model of muscle movement is known as the Sliding Filament Theory.
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http://highered.mcgrawhill.com/sites/0072437316/student_view0/chapter42/animations.html#
Prentice Hall Muscle Contraction Video

4 minutes

http://www.youtube.com/watch?v=83yNoEJyP6g