Parasympathetic nervous system act in a complementary way increasing or slowing the heart rate. In this context, the vagus nerve acts on sinoatrial node slowing its conduction thus actively modulating vagal tone accordingly. This modulation is mediated by the neurotransmitter acetylcholine and downstream changes to ionic currents and calcium of heart cells. The vagus nerve plays a crucial role in heart rate regulation by modulating the response of sinoatrial node, vagal tone can be quantified by investigating heart rate modulation induced by vagal tone changes. As a general consideration, increased vagal tone (and thus vagal action) is associated with a diminished and more
Exposed node problem Exposed node problem In wireless networks, the exposed node problem occurs when a node is prevented from sending packets to other nodes because of a neighboring transmitter. Consider an example of 4 nodes labeled R1, S1, S2, and R2, where the two receivers (R1, R2) are out of range of each other, yet the two transmitters (S1, S2) in the middle are in range of each other. Here, if a transmission between S1 and R1 is taking place, node S2 is prevented from transmitting to R2 as it concludes after carrier sense that it will interfere with the transmission by