Cardiovascular Physiology and Pharmacology Flashcards

Which of the following best describes Poiseuille's law as applied to vascular resistance?

Answer: Resistance is inversely proportional to the fourth power of radius

Poiseuille's law states resistance = 8ηL/πr⁴, meaning resistance is inversely proportional to the fourth power of radius—a small change in radius causes a large change in resistance.

In a patient receiving norepinephrine infusion, which hemodynamic change is expected?

Answer: Increased SVR, reflex bradycardia, variable CO

Norepinephrine predominantly activates alpha-1 receptors, increasing SVR and MAP; reflex vagal bradycardia may occur, and CO may decrease, stay unchanged, or increase depending on baseline status.

The plateau of the oxygen-hemoglobin dissociation curve has clinical significance because it means:

Answer: SaO2 remains high over a wide range of PaO2 values above 60 mmHg

The flat upper portion of the oxyhemoglobin dissociation curve means SaO2 remains above 90% across a wide PaO2 range (60-100 mmHg), providing a safety margin.

Adenosine terminates paroxysmal supraventricular tachycardia by:

Answer: Transiently blocking AV nodal conduction via A1 receptor activation

Adenosine activates A1 receptors in the AV node, activating GIRK channels and hyperpolarizing the node, causing transient AV block that interrupts re-entrant circuits.

Which statement about the Windkessel effect of the aorta is correct?

Answer: Aortic compliance buffers systolic pressure and maintains diastolic flow

The Windkessel effect describes how aortic compliance stores energy during systole and releases it in diastole, maintaining forward flow and reducing pulse pressure.

Which of the following is a direct effect of acute hyperkalemia on cardiac electrophysiology?

Answer: Decreased resting membrane potential (less negative) causing partial depolarization

Hyperkalemia reduces the electrochemical gradient for potassium, making the resting membrane potential less negative, partially inactivating fast sodium channels and slowing conduction.

In a patient with distributive shock, which hemodynamic profile is expected?

Answer: High CO, low SVR, low to normal PCWP

Distributive shock (e.g., septic shock) is characterized by high cardiac output, low systemic vascular resistance, and inappropriately low tissue perfusion despite high flow.