DEFINITIONS - LETTER S

SARCOPLASM - the cytoplasm of a muscle cell.

SARCOPLASMIC RETICULUM - the equivalent to the ER in other cells; this organelle is the major site of Ca²⁺ storage inside muscle cells.  Action potentials release this Ca²⁺ to permit muscle contraction.

SEMIPERMEABILITY - A characteristic of biological membranes; membranes selectively allow some substances to pass.  Membranes generally allow water and some ions to pass but prevent passage of proteins and large colloid molecules.

SHOCK - profound mental and physical depression following severe physical injury or emotional disturbance

SOLUTE - a substance dissolved in a solvent

SOLUTION - a mixture of solute in solvent

SOLVENT - here, a liquid in which solute molecules are dissolved; the solvent in the body is water

SOMATIC - the voluntary nervous system; refers to functions over which you have voluntary control

SPERMATOGENESIS - production of sperm

STEROIDOGENESIS - the production of steroids

STROMA/STROMAL TISSUE - the connective tissue framework of an organ; the stuff that holds the organ together

SYNAPSE - a very narrow fluid-filled space between a nerve and the cell or tissue which the nerve joins: eg. synapses exist between adjoining nerves

SYNCYTIUM - cells which act together as a functional unit

SYNCOPE - fainting because of a lack of blood flow to the brain, often because the heart stops temporarily - the heart generally stops for 1 of 2 reasons ---> i) a lack of blood return to the heart causes it to skip a few beats or ii) the vasomotor center shuts the heart off if blood pressure gets dangerously high

SYNCYTIOTROPHOBLAST - the highly invasive cells of fetal origin which invade the maternal endometrium; the syncytiotrophoblast of the invading embryo initiate the "dedidual" reaction of the maternal endometrium (an immune like reaction), which takes place in the area of implantation of the embryo