The diagram shows a section through mammalian skin illustrating the regulation of blood flow under specific environmental conditions.
Which of the following correctly identifies the physiological state of the vessels, the nervous control pathway from the thermoregulatory centre, and the primary consequence of the response shown?
Arteriole XXX is constricted (smooth muscle contracted); Shunt vessel YYY is dilated; Hypothalamus increases sympathetic impulse frequency to XXX; Minimises heat loss by radiation from capillaries ZZZ.
Arteriole XXX is dilated (smooth muscle relaxed); Shunt vessel YYY is constricted; Hypothalamus decreases sympathetic impulse frequency to XXX; Maximises heat loss by radiation from capillaries ZZZ.
Arteriole XXX is constricted (smooth muscle contracted); Capillaries ZZZ are constricted (smooth muscle contracted); Medulla increases parasympathetic impulse frequency to ZZZ; Minimises heat loss by conduction from shunt vessel YYY.
Arteriole XXX is dilated (smooth muscle relaxed); Shunt vessel YYY is dilated; Hypothalamus increases parasympathetic impulse frequency to YYY; Maximises heat loss by convection from capillaries ZZZ.
