Exam 7: Cardiac Physiology

Cardiac muscle receives its blood supply primarily during ventricular systole when blood is being pumped out into the aorta.

The plateau phase of the action potential in a contractile cardiac muscle cell occurs as a result of activation of slow Ca²⁺ channels.

Indicate the proper order of the events during the cardiac cycle by placing numbers in the blanks preceding the events in sequence.The first and last events are already indicated as a guide. _____ AV valve open; aortic valve closed; ventricular filling occurring _____ blood ejected from the ventricle _____ isovolumetric ventricular relaxation _____ atrial contraction _____ AV valve opens; ventricular filling occurs again; one cardiac cycle is complete _____ aortic valve opens _____ SA node discharges _____ ventricular filling complete _____ ventricular relaxation begins _____ aortic valve closes _____ isovolumetric ventricular contraction _____ ventricular contraction begins; AV valve closes

Why do the heart valves open and close?

The refractory period in cardiac muscle is much shorter than the refractory period in skeletal muscle to ensure that the heart can quickly be restimulated to produce alternate periods of contraction and relaxation.

Which function is done by the aortic valve?

Complete the following statements by using the answer code (options may be used more than once or not at all): -Heart rate can be increased by increasing _____.

What is the result of vagal influences on the heart?

The second heart sound occurs when the semilunar valves close.What does this mark?

What happens in an insufficient AV valve?

Match heart characteristic with correct anatomical structure by using the answer code (options may be used more than once or not at all): -its fast Ca²⁺ channels help initiate

Which of the following will NOT increase stroke volume?

An increase in parasympathetic activity ____________________ the atrial contractility.

Indicate which factor involved in the initiation and spread of cardiac excitation is being identified by using the answer code (options may be used more than once or not at all): -has the fastest rate of pacemaker activity

Match the EKG feature with the correct characteristic by using the answer code: -ventricular depolarization

The right ventricle pumps out blood low in oxygen content,whereas the left ventricle pumps out blood high in oxygen content.

Indicate which pressure relationship exists during the time in question by using the answer code (options may be used more than once or not at all): -when the atrioventricular valve opens

According to the Frank-Starling law of the heart,the shorter the initial length of the cardiac muscle fibres prior to contraction,the more forceful will be the subsequent contraction because the fibres are already partially contracted.

Complete the following statements by using the answer code (options may be used more than once or not at all): -The volume of blood ejected by each ventricle each minute is known as the _____.

The ____________________ is the volume of blood pumped by each ventricle/beat.