MODULE SUPPLEMENT: NEUROLOGICAL SYSTEM
Why Does This Decreased Responsivity Occur?

While there is still debate about where the primary problem lies, there are alterations in the receptor mediated activation of either adenylate cyclase or a more distal step in the sequence required for activation of the cellular response to B-adrenergic stimulation (Lakatta & Sollott, 2002). Probably because of this decreased responsiveness, circulating levels of norepinephrine are increased, rise more readily in response to most stimulation, and return to baseline more slowly.