academics+

q27)
B: 記住aorta/所有血管都唔會自己contract，一定係靠heart chamber的bumping action/ contraction of skeletal muscles that squeezes the veins.
D: left atrium relaxes from V. Its pressure increases from W to Y only because contraction of ventricle makes blood press the atrial wall, so when the ventricle also relaxes from X, atrial pressure decreases.

q28) 3 is medulla (oblongata), it is for controlling reflex actions only.