Actin - ️️A globular protein that links into chains, two of which twist helically about
each other, forming microfilaments in muscle and other contractile elements in cells
The muscle tissue represents the greatest - ️️The greatest tissue mass in the body
at around half of the bodys tota...
PHGY 215 Final
Actin - ✔️✔️A globular protein that links into chains, two of which twist helically about
each other, forming microfilaments in muscle and other contractile elements in cells
The muscle tissue represents the greatest - ✔️✔️The greatest tissue mass in the body
at around half of the bodys total weight.
Thick filaments (myosin) - ✔️✔️Myosin myofilament with heads that bind to actin by
reaching up and ratcheting forward
About 300/filament
The majority of muscles tissue is - ✔️✔️The majority is skeletal muscle (represents
40% of bw in men and 32% in women)
muscle - ✔️✔️tissue composed of fibers that can contract, causing movement of an
organ or part of the body
Muscle fibre - ✔️✔️a single muscle cell. They are much longer than normal cells and
are multinucleate.
Myofibrils - ✔️✔️protein structures that make up muscle fibers
A band - ✔️✔️dark area; extends length of the thick filaments
I band of sarcomere - ✔️✔️the light band between the ends of thick filaments
H zone - ✔️✔️The region at the center of an A band of a sarcomere that is made up of
myosin only. The H zone gets shorter (and may disappear) during muscle contraction.
Slightly lighter portion of A band
M line of sarcomere - ✔️✔️mid-line of sarcomere
Made of proteins that hold thick filaments together
Z line - ✔️✔️A dark thin protein band to which actin filaments are attached in a striated
muscle fiber, marking the boundaries between adjacent sarcomeres.
, Sacromere - ✔️✔️Basic contracting unit of muscle cell consits of actin and myosin
filaments between z-lines in a muscle cell
Muscle cross bridge - ✔️✔️Connection formed when mobile myosin heads bind to actin
molecules in muscles
Myosin - ✔️✔️The contractile protein that makes up the thick filaments of muscle fibers
Dimer of two subunits that looks like a golf club in that it has a long shaft with a globular
head
Thin filaments (actin) - ✔️✔️Made up of proteins actin, tropomyosin, troponin. The
main structural component is two actin filaments.
Tropomyosin - ✔️✔️Thin double helix protein that lies end to end along the actin helix
structure. Regulatory protein that covers the actin binding sites preventing interaction of
actin and myosin
Troponin - ✔️✔️Regulatory protein complex made up of 3 polypeptides. 1 binds
tropomyosin, 1 binds actin, 1 binds Ca 2+
muscle contraction - ✔️✔️The activation of tension generating sites within muscle
fibres when a muscle contracts it shortens
sliding filament mechanism - ✔️✔️Thin filaments slide over thick filaments, by the z
discs pulling together. The I band and H zone shorten, and the A band remains the
same length
concentric contraction - ✔️✔️muscle shortens
power stroke - ✔️✔️action of myosin pulling actin inward (toward the M line)
cross bridge cycle - ✔️✔️sequence of events between binding of a cross-bridge to
actin, its release, and reattachment during muscle contraction
1) binding 2) power stroke 3) detachment 4) binding
sacroplasmic reticulum - ✔️✔️specialized smooth endoplasmic reticulum, releases
calcium on demand when the muscle fiber is stimulated to contract
Runs parallel to the fibres. The lateral sacs of the SR are in close proximity to the T-
tubules. Storage sites for Ca +2
T tubules - ✔️✔️invaginations of the sarcolemma. At the junction of A & I bands, t-
tubules dip into the fibre and run perpendicular to the fibres
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