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Sarcolemma is the name of the cell membrane that encloses
each muscle cell (also known as a muscle
fibre).
Structure
Sarcolemma has a similar biochemical composition
to that of plasmalemma, which is another word for cell
membrane. In terms of the overall structure of muscle fibres, tunnel-like
extensions from the sarcolemma pass across muscle fibres from side to side
(transverse). These extensions of the sarcolemma are called
transverse
tubules, which is often abbreviated to simply "T
tubules".
Functions
Sarcolemma perform an important role in the muscle contraction
process.
Specifically,
when Muscle Action Potential (a form of electrical "instruction")
travels along the sarcolemma of
muscle fibres, then into the transverse tubules, calcium ions
(Ca2+)
are released into the
sarcoplasm. The word "sarcolemma" is formed from two parts, sarco- which
means "flesh", and -lemma which means "sheath".
Compare
sarcolemma, which covers muscle cells, with tendon
sheaths,
which cover tendons.
This Section consists of short summaries about the
structures that form the muscles of the body.
This list is not exhaustive but is intended to be appropriate for students
of A-Level Human Biology, ITEC courses in massage and related subjects,
and some other courses in Health Sciences.
For more general information about Muscles see
the pages about: Anterior
Muscles, Posterior
Muscles, Facial
Muscles, Terminology
about Muscles, and the Structure
of Muscles.
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