Final answer:
Ganglions in the volley principle integrate multiple EPSPs to reach the threshold for an action potential and do not need to fire at the same phase. The volley principle is associated with the summation process in the nervous system, rather than waves in strings or the sexual response cycle.
Step-by-step explanation:
The volley principle refers to the summation process of multiple presynaptic inputs which create excitatory postsynaptic potentials (EPSPs) around the same time, allowing the postsynaptic neuron to reach the threshold for firing an action potential. Ganglions involved in the volley principle do not necessarily have to fire at the same phase like the peak of an input wave because neurons can integrate these EPSPs over time to reach the threshold required for action potential generation.
When addressing the concept of waves in a string, if all inputs end at the same time with equal force, the waves would exhibit destructive interference when out of phase, potentially canceling each other out, resulting in a wave of zero displacement at points where they overly completely (180° out of phase).
In a different context, an orgasm's peak phase in the sexual response cycle involves rhythmic muscle contractions which do not necessarily relate to the firing of ganglions or the creation of waves in a physical medium like a string.