Chapter 20 - The Heart

What is the function of the pulmonary circuit?

Carries blood between the heart and the gas exchange surfaces of the lungs.

What is the function of the systemic circuit?

Transports blood to and from the tissues of the body.

Which type of blood vessels carry blood towards the heat? Which type of blood vessels carry blood away from the heart? 

Veins; Arteries

What property of capillaries permits them to function in the exchange of nutrients, dissolved gases (called gas exchange), and wastes between the blood and surrounding tissues?

They have very thin walls.

Which side of the heart supplies blood to the systemic circuit? Which side of the heart supplies blood to the pulmonary circuit?

The LEFT SIDE supplies blood to the SYSTEMIC circuit.
The RIGHT SIDE supplies blood to PULMONARY circuit.

What is the name of the region located between the two plural cavities that the heart is positioned in?  

Mediastinum

What organ does the pericardium surround?

The heart!

Name the two layers of the serous pericardium and describe their locations. 

Outer parietal layer and the inner visceral layer (epicardium). In between is a pericardial cavity.

What is the function of pericardial fluid? 

Fills the Pericardial Cavity between the outer parietal layer and inner visceral layer. This acts as a lubricant to reduce friction between the two layers as the heart beats.

What is pericarditis?

Inflammation of the pericardium due to pathogenic infection.

What causes cardiac tamponade? 

Pericardial fluid build up (usually resulting from pericarditis or injuries that produce bleeding into the pericardial cavity) which restricts the movement of the heart. In other words, it’s due to EXCESS FLUID (pericardial or blood) in the pericardial cavity.

What is an auricle? 

The expandable extension of an atrium (shows up when the atrium isn’t filled with blood and the outer portion deflates. Looks like the external ear). AKA the ATRIAL APPENDAGE.

List the three layers of the heart from superficial to deep. (Knowledge of prefixes will help you remember where the layers are located) 

Epicardium < Myocardium < Endocardium

Which heart layer contains cardiac muscle cells? Note: You can remember this since the root word myo- describes muscle. 

The Myocardium (forms the atria and ventricles).

What is the structure and function of septa? 

Septa separate the four chambers of the heart. There is the INTER-ATRIAL SEPTUM (separates the atria) and INTER-VENTRICULAR SEPTUM (thicker and separates the ventricles).

Name the two great veins that bring blood directly to the heart. 

Superior vena cava and Inferior Vena Cava (brings blood from systemic circuit to the right atrium)

Where would you find the tricuspid valve? What is another name for the tricuspid valve?

Between the right atrium and the right ventricle. It is also called the Right Atrioventricular (AV) Valve. It has three flaps (cusps).

What is the function of the chordae tendineae?

Prevents valves from opening into atria, ensuring that blood flows in one direction (atrium to ventricles). When the ventricles contract, the blood flowing back toward the atria swings the cusps together, closing the valves.

Contraction of which muscles pull the chordae tendineae? 

Papillary muscles

What is another name for the pulmonary valve? Where do you find this valve? 

Pulmonary Semilunar Valve; found between the right ventricle and the pulmonary trunk (start of the pulmonary circuit).

Which blood vessels bring blood to the left atrium? 

Two left and two right pulmonary veins.
Blood passes through the left atrium to the left ventricle through the mitral valve (left AV valve or the bicuspid valve).

What is the function of the mitral (bicuspid) valve? 

Guards the entrance to the left ventricle.
Transports blood between the left atrium and the left ventricle

What is another name for the aortic valve? Which vessels receive the blood that passes through the aortic valve?   

Aortic (left) semilunar valve.
Blood leaves the left ventricle to the aortic valve, and enters the ASCENDING AORTA. The ASCENDING aorta then makes a U-turn (aortic arch) and becomes the DESCENDING AORTA. Coronary arteries receive some of this blood.

What is the function of the atria?  

Collect blood that is returning to the heart and convey it to the ventricles. Both left and right atria are similar and have similar demands.

Why does the left ventricle have thicker walls even through it pumps the same amount of blood as the right ventricle?  

Because the blood has to travel further in the body (generate more pressure than the right ventricle and has a round cross-sectional area). It has to push up blood into the ASCENDING aorta.

The heart has two pairs of one-way valves. What do the values prevent? 

Prevents back-flow of blood as the chambers contract. (These two valves are the left and right atrioventricular valves).

What happens during regurgitation?

Backflow of blood into the atria

What is the cause of rheumatic fever? 

Infection by streptococcal bacterial, which induces an inflammatory autoimmune response. (occurs in children). This can lead to carditis (heart inflammation).

What is coronary artery disease? 

Build up of plaque causing particle or complete blockage of coronary circulation.

What is coronary ischemia? 

Reduced blood flow leading to inadequate perfusion (process of delivering oxygen rich blood and nutrients to tissues and organs) and reducing heart performance.

What is the usual cause of coronary ischemia?  

Formation of a fatty deposit, or ATHEROSCLEROTIC PLAQUE, in the wall of a coronary vessel. The plaque, or a thrombus (clot), narrows the passageway and reduces blood flow.

What is angina pectoris? 

Sensation of pressure, chest constriction, and pain that radiates from the sternum to arms, back, and neck. (may feel comfortable at rest, but any exertion of the heart may cause this sensation to arise). First most common sigh of coronary artery disease.

What is the medical term for a heart attack? 

Myocardial infarction (MI). This is when part of the coronary circulation becomes blocked and cardiac muscles die from lack of oxygen, creating a nonfunctional area called an infarct.

What is the most common cause of a heart attack?  

CORONARY THROMBOSIS!!! Severe CAD and Coronary thrombosis (clot formation at a plaque, which obstructs vessel).

What is done during an atherectomy? 

A noninvasive surgery in which blockage by a single, soft plaque can be reduced with a long, slender catheter inserted into the coronary artery to the plaque.

What is done during a ballon angioplasty? 

A noninvasive surgery in which the tip of a catheter contains an inflatable balloon. Once in position, the balloon is inflated, pressing the plaque against the vessel walls. This opens up the vessel. A stent may be inserted to hold the vessel open.

What is done during a coronary artery bypass? 

A small section is removed from a small artery or peripheral vein and is used to create a detour around the obstructed portion of the coronary artery. (Up to four grafts can be done during a single operation).

What is autorhythmicity? 

The ability of cardiac muscle tissues to contract on their own without neural or hormonal stimulation. (Hint: AUTO - RHYTHM)

What is another name for the cardiac pacemaker?  

SINOATRIAL (SA) NODE

Embedded in the posterior wall of the right atrium near the entrance of the superior vena cava.(Primary driver of heart rate).

It takes about 100 msec for an action potential to pass through the AV node. Why is this delay important?  

This allows the atria to contract before the ventricles do.

Define bradycardia and tachycardia. 

Bradychardia: Slow heart rate
Tachycardia: Fast heart rate

What is an electrocardiogram? 

A recording of the electrical events in the heart. Obtained by placing electrodes at specific locations on the body surface.

What is heart arrhythmia? 

Irregular heart rhythm or heartbeat force. Can indicate damage to the myocardium, pacemaker cells, or conducting cell pathways.

What is the function of intercalated discs? 

Interconnect cardiac contractile cells and holds membranes of adjacent cells using desmosomes and linked gap junctions. They help transfer the force of contraction and propagate action potentials.

Which type of cardiac arrhythmia is responsible for the condition known as cardiac arrest? 

Ventricular fibrillation (VF). Ventricles quiver and stop pumping blood.

What occurs during the absolute refractory period? 

Cardiac contractile cells cannot generate another action potential (regardless of a strong stimulus) because the fast sodium channels are already open or closed and inactivated. The membrane doesn’t response at all.

Cardiac muscle tissue is highly sensitive to changes in the concentration of which ion in the extracellular fluid? 

Calcium (they have direct and indirect effects on cardiac contractile cell contraction).

Define the cardiac cycle. 

Period between the start of one heartbeat and the next. Involves the alternating periods of contraction and relaxation.

What occurs during systole? What occurs during diastole? 

Systole: Aka contraction. The chamber contracts and pushes blood into an adjacent chamber or into an arterial trunk.
Diastole: Aka relaxation. The chamber fills with blood and prepared for the next cardiac cycle.

What is end-systolic volume (ESV)? 

The amount of blood remaining in the ventricle when the semilunar valve closes.

What occurs in a heart murmur? 

Turbulent blood flow that accompanies regurgitation creates rushing, gurgling sounds.

Define cardiac output. 

Amount of blood pumped by the left ventricle in 1 minute. Indication of blood flow through the peripheral tissues and ventricular efficiency.

Define heart rate. 

The number of heartbeats per minute (can be changed via ANS or hormones).

Define stroke volume. 

The amount of blood pumped out of a ventricle during each contraction (systole)

How is cardiac output calculated? Note: you won’t have to calculate cardiac output on exams. 

Heart Rate X Avg Stroke Volume

How is stroke volume calculated? Note: you won’t have to calculate stroke volume on exams. 

End-diastolic volume (EDV) - End-systolic volume (ESV)

Define end-diastolic volume. 

The amount of blood in each ventricle at the end of ventricular diastole.

Define end-systolic volume. 

The amount of blood in each ventricle at the end of ventricular systole.

What is the cardiac plexus? Is it innervated by the sympathetic division or the parasympathetic division or both or neither? 

A nerve network by which the sympathetic AND parasympathetic division of the ANS innervate the heart.

Where are the cardiac centers which contain the headquarters for autonomic cardiac control located in the brain? 

The medulla oblongata

The cardiac centers monitor baroreceptors and chemoreceptors innervated by which two cranial nerves? 

Glossopharyngeal (IX) and Vagus (X) Nerves.

Define venous return. 

The amount of blood returning to the heart through the veins, which directly affects pacemaker cells. More blood = More stretching = Faster depolarization = Faster heart rate

What is the Bainbridge reflex? 

Aka the ATRIAL REFLEX. Reflex that responds to increased venous return (ATRIAL stretch) by sympathetic stimulation and increase in heart rate.

Which three hormones increase heart rate by their effects on cells in the SA node? 

Epinephrine (E), Norepinephrine (NE), Thyroid hormone (TH).

What is the Frank-Starling principle? 

Rule that says that increasing the EDV = increase in Stroke Volume. (More in = More out).

Define cardiac reserve. 

The difference between resting cardiac output and maximal cardiac output.