15. Endomysium – around
single muscle fiber
Perimysium – around
a fascicle (bundle) of
fibers
Epimysium – covers
the entire skeletal
muscle
16. The light bands are called I bands and the dark bands are called A bands. In
the middle of the I bands there is a line called the Z line (or disc). In the middle
of the A bands (or dark bands) there is a light zone called the H zone. In the
middle of the H zone there is another line, the M line. The precise arrangement of
these features is due to a chain of functional units in the myofibrils, sarcomeres.
17.
18. Thick filaments = myosin
filaments
Composed of the protein
myosin
Has ATPase enzymes
19.
20. Sarcoplasmic reticulum (SR) membranes in close proximity to a
T-tubule. 'RyR' are proteins the aid in the release of calcium
from the SR, 'SERCA2' are proteins that aid in the transport of
calcium into the SR (Brette and Orchard 2007).
28. A muscle fiber is excited via a motor nerve that generates an
action potential that spreads along the surface membrane
(sarcolemma) and the transverse tubular system into the deeper
parts of the muscle fiber. A receptor protein (DHP) senses the
membrane depolarization, alters its conformation, and activates
the ryanodine receptor (RyR) that releases Ca2+ from the SR.
Ca2+ then bind to troponin and activates the contraction process
(Jurkat-Rott and Lehmann-Horn 2005).
38. • If only a single impulse or stimulus is delivered to a muscle a
contraction occurs and is quickly followed by relaxation of the muscle.
This is called a muscle twitch.
• If many impulses or stimuli are delivered to the muscle the muscle
contracts but does not have time to relax before it contracts again. This
is called tetanus.
• If the frequency of stimulation permits the muscle to relax to an even
slight degree between contractions, the tetanus is unfused or
incomplete.
• If the frequency is so high that relaxation does not occur during
contraction, the tetanus is fused or complete