The brain works together with the spinal cord and what to form the nervous system?

Nerves and Nervous tissue. The Nervous system is the general and broad name for the system comprised of the Brain, Spinal Cord, and Nerves, that provides sensory, motor, and psychological function. The system is also split into different groups of nervous system. CNS (the Central Nervous System) contains the brain and spinal cord, and the PNS (Peripheral Spinal Cord) is comprised of the nerves that branch out of the CNS. 

Additionally you have the Sympathetic (which controls "fight or flight"; Epinephrine production, Vasodilation and Constriction, Increased HR, BP, RR) or the Parasympathetic (controls the "Breed, Rest and Digest" which controls sexual urges, muscle relaxation, widespread vasodilation, and slowing down of bodily processes, via Acetylcholine production. 

Inaccuracy is a disadvantage

10/10 recommend bring pads/tampons with you no matter what. im 16 & i’ve had mine since i was 12 and they’re still it regular, but id suggest using the glow app, many women use it for fertility reasons but i use mine specifically for the period tracking portion and it guesses when your next period will most likely be for the next two months. i dont believe theres any way to delay your period, so id say hope for the best but make sure to bring all of your stuff just incase. have a good cruise!