heart and circulation

Question 1

1. Describe the general pattern of blood circulation in a mammal. Name the blood vessels to and from the heart, lungs and kidneys, and the arteries that give oxygen to the heart.

Answer 1

Mammals have a double circulatory system. Blood passes through the heart twice on a complete circuit of the body. Oxygenated blood leaves the heart through the aorta to the rest of the body, oxygen is given to respiring tissue, then deoxygenated blood enters the heart through the vena cava. The blood leaves to the lungs via the pulmonary artery, becomes oxygenated, then enters the left side of the heart via the pulmonary vein, ready to be pumped out through the aorta. The renal artery takes blood to the kidneys, where it leaves by the renal vein. The coronary arteries take oxygenated blood to heart cells.

Question 2

3. Describe how blood only travels in one direction through the heart.

Answer 2

The heart creates pressure gradients, and blood flows from high to low pressure. Valves prevent backflow in places when the pressure gradient would send blood the wrong way.

Question 3

4. What is the equation for cardiac output?

Answer 3

CO = stroke volume x heart rate Stroke volume = volume of blood pumped out of the left ventricle each heart beat Heart rate = heart beats per minute

Question 4

5. Explain why the highest blood pressure is produced in the left ventricle.

Answer 4

The left ventricle has the most muscle in its wall, and therefore causes the strongest contractions.

Question 5

6. What is the function of the coronary arteries?

Answer 5

Carry oxygen and glucose to the heart muscle tissue

Question 6

7. Explain how the heart muscle and the heart valves maintain a one-way flow of blood from the left atrium to the aorta.

Answer 6

When the atria contract the atrium has higher pressure than ventricle causing atrioventricular valves to open; The ventricle now has higher pressure than atrium due to filling with blood and contraction causing atrioventricular valves to close; Ventricle has higher pressure than aorta causing semilunar valve to open; Higher pressure in aorta than ventricle as heart relaxes causing semilunar valve to close; Muscle contraction cause the increases in pressure;

Question 7

8. What does one cardiac cycle consist of?

Answer 7

Atrial systole, ventricular systole, diastole.