The amounts of mood-elevating chemicals in the brain are

a. nonexistent in sedentary people but not in those who are physically active.
b. the same in sedentary people and in those who are physically active.
c. lower in sedentary people than in those who are physically active.
d. higher in sedentary people than in those who are physically active.

Check all that occur during ventricular systole. a. the av valves open to allow blood to enter the ventricles from the atria. b. the av valves open to allow blood to enter the ventricles from the atria. c. the semilunar valves remain closed throughout systole to prevent backflow of blood into the ventricles. d. the semilunar valves remain closed throughout systole to prevent backflow of blood into the ventricles. e. the semilunar valves open to allow blood to flow into the large arteries. f. the semilunar valves open to allow blood to flow into the large arteries. g. the av valves close to prevent backflow of blood into the atria.