Sinoatrial node rate, and increasing heart rate. An increase in heart rate is known as positive chronotropy. The parasympathetic nerves supplying the SA node (in particular the Vagus nerves) originate in the brain. These nerves release a neurotransmitter called acetylcholine (ACh). ACh binds to a receptor called an M2 muscarinic receptor, located on the SA node membrane. Activation of this M2 receptor, then activates a protein called a G-protein (in particular G protein, i for inhibitory). Activation of this G-protein, blocks the cAMP pathway, reducing its effects, therefore inhibiting sympathetic activity and slowing action potential production. As well as this, the G-protein
Node (Well of Echoes) or node-drainers that drain the node of the field and render anything that draws power from it useless. Mancers who cannot draw from a distat node's field must rely on charged crystals, while clankers, constructs and any other devices of the Art will not work. There are also rare places called anti-nodes, where the Art does not work or is at least greatly reduced. Node (Well of Echoes) Nodes are fictional, naturally occurring phenomena in Ian Irvine’s "The Three Worlds Cycle" of novels. They often occur in places where there is a significant landmark, such as on a hill or