CH 17 functional anatomy of heart

Where is the point of maximal impact (PMI) located, and why is it important?

At the 5th intercostal space, mid-clavicular line; helps detect thoracic abnormalities like pneumothorax.

How do the shapes of the left and right ventricles support their functions?

Left = spherical (high-pressure systemic flow); Right = crescent-shaped (low-pressure pulmonary flow).

What is the primary purpose of the atrioventricular (AV) valves?

To prevent backflow into the atria during ventricular contraction.

What happens when a ventricular septal defect (VSD) is present?

Blood flows from left to right ventricle, overloading pulmonary circulation and stressing the heart.

How does mitral valve stenosis lead to pulmonary edema?

It backs up blood into pulmonary veins, increasing pressure and causing fluid to leak into alveoli.

During which phase does most coronary perfusion occur, and why?

During diastole, when relaxed ventricles allow coronary arteries to fill.

Why is the lack of collateral circulation in coronary arteries significant?

Blockages can lead to ischemia or infarction due to limited alternate pathways.

What causes angina pectoris, and how is it treated?

Myocardial ischemia from restricted blood flow; treated with CABG, angioplasty, or stents.

Why does the heart extract 70% of oxygen from coronary blood flow at rest?

Because of its high, constant energy demands.

What is the function of the sinoatrial (SA) node?

Acts as the pacemaker; initiates electrical impulses that trigger heartbeat.

How does the Frank-Starling mechanism adjust cardiac output?

Greater venous return stretches ventricles more → stronger contractions → increased output.

What is the normal duration of a complete cardiac cycle?

About 0.8 seconds.

How is mean arterial pressure (MAP) calculated?

MAP = (Systolic + 2 × Diastolic) ÷ 3

How do veins serve as blood reservoirs?

They store ~64% of total blood volume due to high stretchability.

What does an increased systemic vascular resistance indicate?

Higher resistance = more work for the heart to pump blood.

What are the potential complications of chronic hypertension?

Heart failure, stroke, kidney damage, and vascular damage.

What is the role of beta-2 receptors in vascular regulation?

Cause vasodilation to increase blood flow.

Why are alpha receptor blockers beneficial for patients with high vascular resistance?

They reduce vasoconstriction, lowering resistance and easing heart workload.

What is the role of elastic recoil in the arteries during the cardiac cycle?

Maintains blood flow during diastole when the heart relaxes.

How is pulse pressure calculated, and what does it indicate?

Pulse Pressure = Systolic – Diastolic; indicates arterial stiffness/compliance.

Calculate cardiac output if the stroke volume is 80 mL and the heart rate is 70 bpm.

80 × 70 = 5600 mL/min (5.6 L/min)

Why does the heart extract such a high percentage of oxygen from coronary blood flow?

To meet its continuous, high metabolic demands.

How does systemic vascular resistance (SVR) affect cardiac output?

Higher SVR = higher afterload → can decrease cardiac output.

What is the relationship between hypertension and left ventricular hypertrophy?

Chronic high BP causes the left ventricle to thicken to overcome resistance.

Describe how local metabolic byproducts influence blood vessel diameter.

Substances like CO₂, lactic acid, and H⁺ cause vasodilation.

How does sympathetic stimulation affect vascular resistance?

It increases resistance by causing vasoconstriction.

What is the effect of beta-2 receptor activation on blood flow?

Promotes vasodilation → increased blood flow.

How does muscular contraction aid venous return?

Compresses veins to push blood toward the heart (muscle milking).

What is the role of the thoracic pump in facilitating venous return?

Changes in chest pressure during breathing draw blood to the heart.

Why are patients with high vascular resistance at increased risk for heart failure?

The heart works harder against resistance, which can lead to failure.

How do the elastic properties of veins contribute to their function as blood reservoirs?

Their stretchiness allows them to hold large volumes of blood.

Calculate the MAP if systolic BP is 120 mmHg and diastolic BP is 80 mmHg.

MAP = (120 + 2×80) ÷ 3 = 93.3 mmHg

Why is pulse pressure a useful indicator of arterial compliance?

It reflects how stiff or flexible arteries are.

What happens to cardiac output when stroke volume or heart rate increases?

Cardiac output increases.

How do alpha blockers