40. Circulatory System

Which of the following is often called the pacemaker of the heart?

Which structures prevent heart valves from being forced backward into the wrong chamber?

Approximately how many times does the human heart beat in a single day?

Which chamber(s) of a human heart receive(s) and pump(s) oxygenated blood?

Which of the following decreases blood pressure?

Which of the following best explains how a young, healthy individual could develop a serious heart condition?

A mutation that results in a nonfunctioning nitric oxide receptor would cause __________.

Your blood pressure is 120/70. The "120" indicates __________, and the "70" indicates __________.

What is the physiological cause of a heart attack?

Heart valves function to __________.

A recording of the electrical activity of a patient's heart shows that the atria are contracting regularly and normally, but every few beats the ventricles fail to contract. Which of the following is probably functioning improperly?

Blood leaves the inferior vena cava and flows directly into the __________.