CPR can result in broken ribs

 When performed by untrained or overzealous individuals, CPR can result in broken ribs or a broken sternum, and can inflict additional severe damage on the patient. It is also possible, if the hands are placed too low on the sternum, to manually drive the xiphoid process into the liver, a consequence that may prove fatal for the patient. Proper training is essential.

“Staying Alive,” song recorded in 1977 by the Bee Gees

 “Staying Alive,” recorded in 1977 by the Bee Gees. If you are unfamiliar with this song, a version is available on www.youtube.com. 

Subvalvular apparatus: The papillary muscles and the chordae tendineae, known as the subvalvular apparatus, hold the valves closed so that they do not prolapse.

Papillary muscles, together with the chordae tendineae, make up the subvalvular apparatus. 

Blood flows through an atrioventricular (AV) valve Blood flows through an atrioventricular (AV) valve when blood pressure in the atria becomes high during atrial systole and blood pressure in the ventricles becomes low enough during ventricular diastole, creating a blood pressure gradient.

Papillary muscles, finger-like projections from the wall of the ventricles, connect the chordae tendineae (heartstrings) to the cusps of the atrioventricular valves. This connection prevents the valve from prolapsing under pressure.

 Guiding Questions

Cardiac Cycle: Conduction & Mechanical Events

Explain how pressure gradients drive blood flow in the cardiovascular system.

Ventricular contraction ejects blood into the major arteries, resulting in flow from regions of higher pressure to regions of lower pressure.

Identify the location of high pressure and low pressure during systole and diastole.

Outline the steps of the cardiovascular cycle and describe what happens to pressure and blood flow in each chamber at each step of the cycle. Be sure to identify the status of the AV and semilunar valves during each stage of the cycle.

Explain how the pressure gradients cause the valves open and close during the cardiac cycle.

What is the importance of the gap junctions that connect the autorhythmic cells with the contractile cells?

Outline the steps of the intrinsic conducting system and associate them with the steps of the cardiac cycle.

Describe how the SA node controls heart rate. What happens when the SA node is damaged?

Explain how heart rate is controlled by the parasympathetic system and the sympathetic system. Be sure to discuss the intrinsic heart rate, the neurotransmitters and receptors that operate during control of heart rate.

What is an ECG and what kind of information can be gathered from it?

Draw an ECG trace. Identify the P wave, the QRS complex, and the T wave.

Draw another ECG trace. Identify the part of the ECG trace that correlates with atrial depolarization, atrial hyperpolarization, ventricular depolarization and ventricular hyperpolarization.

Now draw a third trace. Identify the part of the ECG trace that correlates with atrial systole, atrial diastole, ventricular diastole, and ventricular systole (remember that physical events happen AFTER the electrical events).

Describe what is happening to both pressure and volume during each stage of the cardiac cycle. Be sure to use the following terms: Ventricular filling, end diastolic volume, isovolumetric contraction, ejection, and end systolic volume, isovolumetric relaxation.

How does ESV change during exercise?

What is stroke volume? What is the average stroke volume? How does stroke volume change?

 

Cardiac Output

Define cardiac output. How do I determine cardiac output?

Explain how altering heart rate (via sympathetic or parasympathetic stimulation) alters cardiac output.

What is afterload and how does it affect cardiac output? Give an example of how afterload alters cardiac output. 

What is preload and how does it affect cardiac output? Why does EDV determine the force of contraction?

What are some ways that I can alter EDV (and therefore alter stroke volume)?

Describe how the skeletal muscle pump and the respiratory pump affect EDV **(we'll cover this when we discuss blood vessels)

How does total blood volume affect EDV?

How much of the blood is contained in the venous circulation? How can I send more of the blood in the veins to the heart, and how does this affect EDV? **(we'll cover this when we discuss blood vessels)

Define contractility and explain how an inotropic agent affects contractility.

Explain how the sympathetic system modulates contractility. Be sure to name the neurotransmitters and receptors involved.

In a fight or flight response, explain what happens to the following factors and why they are affected this way (be sure to discuss neurotransmitters and receptors): heart rate, venous return, EDV, contractility, stroke volume, cardiac output.