Explain the mechanisms that assist in the return of venous blood to the heart.

Which of the following factors would increase peripheral resistance?

a. Increased blood viscosity

b. Shorter vessel

c. Vasodilation

d. An increase in vessel radius

You are babysitting two children who are having a contest to see who can hang upside-down for the longest time. At the end of the contest, both children feel dizzy and are worried they are sick. Explain to them why they feel this way and why the effect is only temporary. (Hint: Consider how the baroreceptor reflex responds when a person hangs upside-down.)