A patient reports the frequent use of the Valsalva maneuver to expel hard, impacted stools. Which physiologic change occurs during this type of straining?
a) Increased intrathoracic pressure leading to decreased venous return to the heart.
b) Increased heart rate and cardiac output due to sympathetic nervous system activation.
c) Decreased intracranial pressure resulting in improved cerebral perfusion.
d) Decreased abdominal pressure leading to relaxation of the pelvic floor muscles.
