Meats: Structure and Function of Muscle

What are the types of muscle?

skeletal (35 to 65 % of carcass weight)

smooth ( component of blood vessels)

cardiac (heart)

What are the other types of muscle?

striated muscles (banding pattern)

voluntary

involuntary

Skeletal Muscle

attached directly or indirectly to bones

\-ligamnets

\-fascia

\-cartilage

\-skin

Fasciculi

Group of muscle fibers

What is the structural unit of a skeletal muscle?

muscle fiber, myofiber, or muscle cell (75 to 92% total muscle volue)

What does the remaining volume of skeletal muscle contain?

connective tissues, blood vessels, nerve fibers, and extracellular fluid

Skeletal muscle fiber description

long, multinucleated, unbranched, threadlike

Sarcolemma

membrane surrounding a muscle fiber

The fiber length is generally

centimeters long and does not extend the length of the entire muscle

The Sarcolemma is

relatively elastic and composed of protein and lipids

What does the elasticity of the Sarcolemma allow it to do?

enables it to endure distortion during contraction, relaxation, and stretching

Transverse tubles

invaginations of the sarcolemma that form a network of tubles

The Sarcoplasm (muscle cytoplasm) contains

organelles, 75-80% water, liquid droplets, glycogen granules, ribosomes, proteins

Is skeletal muscle multinucleated

Yes

Myofibril

unique to muscle, long thin rods, usually parallel to the long axis of the fiber, bathed in the sarcoplasm and extend the length of the muscle fiber

How many muscle fibers can meat animals have?

1000-2000

Myofilament

thick and thin filaments (major proteins in both)

Thin filaments are

aligned precisely across the myofibril and are parallel to each other and the thick filaments

The overlapping of thick and thin filaments produces

the straited look

Across the muscle fiber

myofibril are aligned giving the straited appearance

The I-band

produces the light areas when viewed with a polarized light

A-band

broad dark band anisiotropic in polarized light

Which is denser, the A band or I Band

A band

I band is bisected by the

Z disk, a dark thin band

Two adjacent Z disk is called a

sarcomere

A sacromere includes

A band and two half I bands located on either side of the A band

Sacormere

repeating structural unit of the myofibril and is also the basic unit where muscle contraction and relaxation occur

The length of the muscle is dependent upon

\

the state of contraction at the time the muscle is examined

The other features of the myofibril existes as

zones, lines, or bands with different densities

\-h zone

\-m line

The appearance can change with

contraction state

The A-band consists of

thick filaments of the sarcomere referred to as myosin filaments and is held in position by protein on the M-line

(thin filaments extend into the I-Band)

The I-band consist of

thin filaments of the sarcomere (actin filaments)

Only _____ are present in the H-zone

thick

What are Z filaments?

material of the Z disk and connect with actin filaments on either side of the disk

What 6 proteins account for 90% of the myofibril?

myosin, actin, titin, tropomyosin, troponin, and nebulin

Contractile protein

myosin actin

Cytoskeleton proteins

titin nebulin

Regulatory Proteins

tropomyosin and troponin (role is to regulate actin-myosin interactions during contraction)

Actin is

globular spherical shaped molecule (g actin)

single form of actin

When does the fibrous nature of actin occur?

when G-actin monomers polymerize to form F-actin (fibrous actin)

F-actin and G-actin monomers

are linked together in strands

Super helix

two strands of F-actin are spirally coiled around each other

Myosin Iis

elongated rod shaped with a thick portion at one end

The thickened end of the myosin is called

the head

The rod or tail portion is

the long thin portion that forms the backbone of the thick filament

The neck of the myosin is

the portion between the head and rod region

The head region of the myosin is

double headed and projects laterally from the long axis of the filament

In the center of the A-band

myosin filament contains only the rod portion of myosin without any globular heads

The myosin heads contain

functionally active sites which function during contraction

\-form cross bridges with actin

\-attaches to G-actin