The heart is a complex muscle that pumps blood through the three divisions of the circulatory system: the coronary (vessels that serve the heart), pulmonary (heart and lungs), and systemic (systems of the body). Coronary circulation intrinsic to the heart takes blood directly from the main artery (aorta) coming from the heart. For pulmonary and systemic circulation, the heart has to pump blood to the lungs or the rest of the body, respectively. In vertebrates, the lungs are relatively close to the heart in the thoracic cavity. The shorter distance to pump means that the muscle wall on the right side of the heart is not as thick as the left side which must have enough pressure to pump blood all the way to your big toe.

Complete the tasks on the list below:

• Read the following page in the OpenStax textbook
• Mammalian Heart and Blood Vessels 
• Read the entire page
• Follow the link to Your Heart's Electrical System, and watch the animation
• Use the Glossary at the bottom of the page to help with the vocabulary for this week
• Use the Review Questions and Free Response questions to check for understanding

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