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