Sarcoplasm
Sarcoplasm is the cytoplasm of a myocyte. It is comparable to the cytoplasm of other cells, but it contains unusually large amounts of glycosomes and significant amounts of myoglobin, an oxygen-binding protein. The calcium ion concentration in sarcoplasma is also a special element of the muscle fiber; it is the means by which muscle contractions take place and are regulated.
It contains mostly myofibrils, but its contents are otherwise comparable to those of the cytoplasm of other cells. It has a Golgi apparatus near the nucleus, mitochondria just inside the cell membrane, and a smooth endoplasmic reticulum.
While sarcoplasm and myoplasm, viewed etymologically, might seem to be synonyms, they are not. Whereas sarcoplasm is a type of cytoplasm, myoplasm is the entire contractile portion of muscle tissue.
