The classical “knee-jerk” stretch reflex illustrates the critical role of voltage-gated Ca2+ channels in converting electrical signals to biochemical and mechanical signals. Upper panel, sequence of events in the stretch reflex depicted schematically. Lower panel, corresponding mechanical, electrical and chemical steps in the pathway, with the participating channel types, ions and transmitters indicated. Note that Ca2+ channels are required in every case of conversion from membrane electrical activity (ELEC) to intracellular biochemical signaling (CHEM). A, actin (thin filament); ACh, acetylcholine; AChR, acetylcholine receptor; Ca, calcium; glu, glutamate; GluR, glutamate receptor; K, potassium; M, myosin (thick filament); MF, muscle fiber; MN, motoneuron; MS, muscle spindle; Na, sodium; NT, nerve terminal; SR, sarcoplasmic reticulum; T, transverse tubule.
From: A Brief History of Calcium Channel Discovery
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