Pt 1: Chemistry, Ions, and Body Fluids

Calcium in skeletal/cardiac muscle contraction

binds to troponin C which moves tropomyosin

Calcium in smooth muscle contraction

binds to calmodulin which activates MLCK

Calcium sensor for secretion

synaptotagmin

Calcium as a secondary messenger

activates enzymes like CaMKII, calcineurin, protein kinase C, and nitric oxide synthase

Calcium in electrical signaling

carries the plateau phase of the cardiac action potential, helps set threshold for excitation in neurons and smooth muscle

Extracellular cations

Na, K, Ca, Mg, H

Extracellular anions

Cl, HCO, protein phosphate, sulfate, organic acids

Interstitial fluid cations

Na, K, Ca, Mg

Interstitial fluid anions

Cl, HCO

Intracellular fluid cations

K, Mg, Na

Intracellular fluid anions

phosphate and organic phosphates, protein, HCO

Polar bonds

covalent bonds when an atom is more electronegative than the other

Hydration shells

allow ions to pass more easily through the cell membrane

pH scale

one pH unit is a tenfold change in H+

Osmolarity vs. tonicity

tonicity counts only the solutes that cannot cross the membrane ex. urea crosses membranes freely, so a urea solution has high osmolarity but low tonicity