Module 2: Figure temporal aspects
Temporal aspects of Ca2+ signalling.
In almost every example where Ca2+ is used as a signal, it is presented as a brief transient, which is the digital signal used to set up complex temporal patterns of Ca2+ signalling. In some cells, these pulses are produced on demand in that they are generated in response to periodic stimulation (blue arrows) as occurs in muscle contraction where a brief burst of Ca2+ activates the contractile machinery, which then recovers when the Ca2+ signal is removed. Likewise, the release of neurotransmitters from nerve terminals is triggered by a brief localized pulse of Ca2+. In many other tissues, which receive a continuous stimulation over a prolonged period (blue bar), the Ca2+ signal is again presented as brief spikes that are produced rhythmically to give highly regular Ca2+ oscillations whose frequencies vary with the level of cell stimulation.