CVS PHYSIOLOGY

Contractility and stroke volume increases in

• β -blockade

• Acidosis

• ↓ extracellular Na+

• ↓ intracellular Na+

Phase 2 of action potential is due to

• Sodium Influx

• Potassium Influx

• Calcium Influx

• Chloride Influx

Answer explanation

Phase 2 is plateau phase and is due to calcium Influx.

Which of the following about Aortic regurgitation is true ?

• End diastolic volume increases

• Force of contraction decreases

• Stroke volume decreases

• Both b and c

Answer explanation

Force of contraction and stroke volume increases by Frank starling mechanism.

Normal duration of PR interval is

• 0.6 - 1 sec

• 0.12 - 0.20 sec

• 0.35 - 0.45 sec

• < 0.44 sec

Speed of conduction is faster in

• SA Node

• AV Node

• Ventricular Muscle

• Purkinje fibres

Pacemaker potential is due to

• Fast Na+ channel

• Decrease in K+ Permeability

• Slow Ca+ channel

• Rapid repolarization

P wave is absent in

• Atrial fibrillation

• Atrial flutter

• CCF

• PSVT

Chemical structure of Hemoglobin

• Has 2 polypeptide chains with 4 heme

• Has 4 polypeptide chains with 2 heme

• Has 4 polypeptide chains with 4 heme

• Has 2 polypeptide chains with 4 heme

The patient states that his episodes of chest pressure generally last around 5 minutes but never longer than 15 minutes. They often occur when

he uses the push mower to mow the lawn on the steep part of the yard or when he rides his bicycle up a hill but not when he is walking, sitting, or

sleeping. He thinks the severity and pattern of chest pain have stayed pretty much the same since he first noticed it 6 months ago. Diagnosis

• Stable Angina

• Unstable Angina

• HOCM

• Hypertension

Answer explanation

This patient has stable angina. In stable angina, a constant and predictable level of physical exertion elicits the chest

pain.

It is always promptly relieved by rest.

In contrast,

unstable angina is characterized by the development of chest pain at rest or after only mild exertion and can last

longer than 15 minutes.

Major portion oof coronary blood flows during

• Isovolumetric contraction

• Isovolumetric relaxation

• Plateau phase

• Variable

Answer explanation

During isovolumetruc relaxation phase(Diastole).