A hormone Cascade occurs when

 A hormone can stimulate the release of series of other hormones, the last of which activates a nonendocrine target the cell this is called a hormone cascade pathway. The release of thyroid hormone results from a hormone cascade pathway the hypothalamus, anterior, and thyroid gland.

blood enters the heart through two large veins, the inferior and superior vena cava, emptying oxygen-poor blood from the body into the right atrium of the heart. as the ventricle contracts, blood leaves the heart through the pulmonic valve, into the pulmonary artery and to the lungs where it is oxygenated.