The cardiovascular System 4

Question 1

The Cardiac Cycle

Answer 1

Is the period of 1 heartbeat
It has a systole part and a diastole part
- Systole: contraction phase
- Diastile: relaxation phase
Each cycle takes about 0.8 s

Question 2

During one cardiac cycle

Answer 2

• a series of electrical events occur
• a series of presssure and blood volume changes in the heart chambers
• a series of heart sounds are heard
  All of these events can be represented by one(intimidating) graph called the Wigers Diagram

Question 3

The pressure change in the left ventricle

Answer 3

The left ventricle contracts after the left atrium.
At the start of systole, the left ventricle undergoes isovolumetric contraction, increasing pressure without changing volume.
When ventricular pressure exceeds aortic pressure, the aortic valve opens, allowing the ejection of blood into the aorta.
At the start of diastole, the aortic valve closes, resulting in isovolumetric relaxation and a rapid decline in pressure without changing volume.

Question 4

The pressure change in the left atrium

Answer 4

During atrial systole, the left atrium contracts to increase pressure, pushing blood into the left ventricle
• Mitral valve closes during ventricular systole, preventing backflow to the left atrium
• During atrial diastole, the pressure in the left atrium decreases, which allows blood to enter from the pulmonary veins
• Mitral valve opens when ventricular pressure falls below the atrium, allowing passive blood flow from the atrium to the ventricle.

Question 5

The pressure difference in the aorta

Answer 5

Aortic valve opens to receive blood ejected from the left ventricle, rapidly increasing aortic pressure to a maximum of 120 mmHg
• When the aortic valve closes, it creates the dicrotic notch (incisura), a small pressure fluctuation due to the brief backflow of blood against the closed valve.
• Aortic pressure slowly falls to 80 mmHg during ventricular diastole to maintain a continuous blood flow in the systemic circuit.

Question 6

What does isovolumetric relaxation refer to?

Answer 6

Relaxation of the ventricles when both the mitral and aortic valves are closed

Question 7

What drives the flow of blood through the vascular system during diastole?

Answer 7

Elastic recoil of the large arteries

Question 8

True or False
When stimulated by the sympathetic nervous system, the coronary blood vessels undergo vasodilation

Answer 8

True

Question 9

Coronary circulation

Answer 9

The shortest circulation in the body
- blood enters the coronary artery at the base of the aorta and empties into the right atrium through the pulmonary sinus
- the coronary arteries are located in the epicardium and branch into the smaller arteries that supply the myocardium

Question 10

Why does coronary blood flow primarily occur during diastole?

Answer 10

Diastole:
- muscle fibres are relaxed and myocardial blood flow is maximal
Systole:
- contracting fibers collapse the supply vessels and flow falls to zero

Question 11

The term for pain associated with deficient blood delivery to the heart that may be caused by the transient spasm of coronary arteries is

Answer 11

Angina pectoris(chest pain)