The shiver is also usually accompanied by a momentary rise in blood pressure and a temporary feeling of euphoria, often causing people to say "ahhh...".

It is the SNS which acts to control bladder function; it makes sure that the bladder is relaxed and that the urethral sphincter is contracted. Part of the SNS response causes the brain to produce a number of chemicals, including the catecholamines epinephrine, norepinephrine, and dopamine. It is a switch to PNS, and the resulting switch in catecholamine production which most likely produces the shiver.