circulation questions

Assume a blood cell is in the right ventricle of the heart. Arrange the following list of structures in the order the blood cell would visit them in one trip around the body:

right atrium, aorta, liver capillaries, pulmonary artery, venule (in liver), lung capillaries, inferior vena cava, left ventricle

Pulmonary artery, lung capillaries, left ventricle, aorta, liver capillaries, venule, inferior vena cava, right atrium

What are two important differences between veins and arteries?

Veins carry blood to the heart and have one-way valves. Arteries carry blood away from the heart and do not have valves

When you check a person’s pulse, you must touch an artery, not a vein. Why?

The blood flowing in an artery moves by the force of the heartbeat. By the time the blood reaches a vein, that force has largely dissipated

What is special about the functioning of the cells of the SA node (the pacemaker), in contrast to the other cells of the heart?

The cells of the SA node can initiate an electrical signal that causes the myocardial cells to contract

What sort of gated ion channel (voltage-gated, mechanically-gated, or ligand-gated) would you expect to find in the SA node?

Voltage-gated

Why must the signal from the SA node be delayed at the AV node before it is passed to the ventricles?

The signal from the SA node, being an electrical signal, moves very fast; the delay at the AV node gives time for the ventricles to fill with blood before the signal for ventricular contraction is passed along

How does the size of the conducting cells in the AV node contribute to the slowing of this signal?

The cells have a narrow diameter. The speed of conduction of an action potential (electrical signal) decreases with decreasing diameter of the conducting cell

What are two ways arterioles contribute to the regulation of circulation?

One, arterioles can either contract or dilate, thus restricting or increasing the blood supply to a capillary bed. Two, arterioles have precapillary sphincters that can open and close, according to the tissue’s need for oxygen

Why is diastolic blood pressure not equal to zero?

During systole, arteries do not empty completely; the arterioles receiving the blood will offer resistance to blood flow. This resistance maintains some positive pressure in the arteries even during diastole