Heart

In calcium-induced calcium release, the second wave of calcium comes from

sarcoplasmic reticulum

The channels responsible for the second influx of calcium into the cytosol of cardiac contractile cells are:

Ryanodine receptors

The picture shows four time traces corresponding to different heart locations: SA node, AV node, atrial muscle and ventricular muscle. Which one corresponds to the ventricular muscle?

4

Match ion to the role its influx plays in cardiac pacemaker cells

Brings membrane potential to a threshold 

Na+

Stimulate rapid depolarization  

Ca2+

Terminate depolarization

K+

Does the Frank-Starling law apply to skeletal muscles?

No, because the length-tension curve for skeletal muscles passes through a maximum

The broken line shows the normal AV nodal potential. Additional stimulation of acetylcholine muscarinic receptors shifts the curve. The new curve is … (enter 1 or 2)

2

Estimate the cardiac output (in liters/min) for an untrained individual at 100 beats/minute. SV, stroke volume.

12

Which formula correctly expresses the relationship between the cardiac output (O), the end-diastolic volume of the ventricle (V), the ejection fraction (E) and the heartbeat rate (R)?

O = VER

The volume of the ventricle is the smallest

 

At the end of systole

The vertical axis shows the force developed in the heart muscle and the horizontal axis shows the concentration... of what? (Hint: The concentrations are in the physiological range)

Intracellular Ca²⁺

Which statement is correct?

Depolarization does not directly affect the atrioventricular valves

A chemical that reduces the activity of F channels would be expected to

Reduce the heart rate

What is the common requirement for heart, skeletal and smooth muscle activation?

Calcium increase

Beta blockers are antagonists of β-adrenergic receptors. What would be their effect on the heart?

Decrease the heart rate

The following questions refer to the Wiggers diagram in the slide 9-5. 

Tension in the ventricle increases but its volume remains constant in region 2

Aortic valve is open, tension in the ventricle continues to increase in region 3

Refilling of the ventricle begins in region 6

Both valves are closed, the ventricle is relaxing in region 5

2,3,6,5

What is the direct effect of an increased afterload?

The duration of ventricular ejection is decreased