Chap 19 - Before you go on book review

The amount of blood ejected by each ventricle in 1 minute. CO = HR X SV. Typical resting values: CO = (75bpm)(70mL/beat)= 5250mL/beat >>the bodies total volume of blood (4-6L) passes through the heart every minute

Define cardiac output in words and with a simple formula.

SYSTOLE - contraction. DIASTOLE - relaxation

Define systole and diastole.

CARDIAC CENTER: initiates autonomic output to heart (reticular formation of medulla oblongata). CARDIOSTIMULATORY EFFECT: sympathetic pathway. CARDIOINHIBITORY: communicated by way of VAGUS nerves

Describe the cardiac center and innervation of the heart.

PULMONARY: supplied by RIGHT side of heart; carries blood TO the lungs for gas exchange and returns it to the heart. SYSTEMIC: supplied by LEFT side of heart; supplies blood to every organ (incl. other parts of the lungs and the heart itself)

Distinguish between the pulmonary and systemic circuits and state which part of the heart supplies each one.

The heart valve opens when pressure on one side of a valve is greater than pressure on the other, forcing the blood through

Explain how a pressure gradient across a heart valve determines whether a ventricle ejects blood? .

The ventricles tend to eject as much blood as they receive. SV is proportional to the EDV. W/in limits, the more the ventricles are stretched, the harder they contract on the next beat

Explain the principle behind Frank-Starling law of the heart. How does this mechanism normally prevent pulmonary or systemic congestion?

CHRONOTROPIC agents: affect HR >positive - increase HR (epinephrine, norepi, sympathetic stim). Negative - decrease HR (too much K, ACH, parasym). ISOTROPIC agents: contractility >positive - increase contractility (too much Ca, epi., norepi., caffeine) > negative - decrease contractility (decrease Ca & increase in K, myocardial hypoxia, acidosis)

Explain what is meant by positive and negative chronotropic and isotropic agents.

INCREASE preload > increase contractility > increase SV > increase CO. INCREASE afterload > decrease SV > decrease CO.

How do preload, contractility, and after load influence stroke volume and cardiac output?

SAME: both have signal that causes depolarization. DIFFERENT: SM waits for signal and has a stable resting potential whereas CM doesn't

How does excitation-contraction coupling in cardiac muscle resemble that of skeletal muscle? How is it different?

Cells of the SA node do not have a stable membrane potential. It drifts up, showing a gradual depolarization >> creating a regular beat

How does the pacemaker potential of the SA node differ from the resting membrane potential of a neuron? Why is this important in creating the heart rhythm?

P wave: atrial depolarization. PQ segment: atrial systole. QRS: atrial repolarization/ ventricular depolarization. ST segment: ventricular systole. T wave: vent. Repolarization. T-P: vent. Diastole.

Identify the portion of the ECG that coincides with each of the following events: atrial depolarization, atrial systole, atrial repolarization, ventricular depolarization, ventricular systole, ventricular depolarization, and ventricular diastole.

EPICARDIUM: serous membrane of the EXTERNAL heart surface. ENDOCARDIUM: lines INTERIOR; covers valve surface and is continuous with the endothelium of blood vessels. MYOCARDIUM: MIDDLE; cardiac muscle; thickest layer and performs the work of the heart.

Name 3 layers of the heart and describe their structural differences

It is not prone to fatigue.

Cardiac muscle rarely uses anaerobic fermentation to generate ATP. What benefit do we gain from this fact?

RT atrium > R AV (tricuspid) > R ventricle > pulmonary valve > pulmonary trunk > pulmonary arteries > lung > pulmonary veins > L atrium > L AV (bicuspid) > L ventricle > aortic valve

Trace the flow of blood through the heart, naming each chamber and valve in order.

Great cardiac vein. Posterior interventricular vein (middle cardiac) and Left marginal vein.

What are the 3 major veins that empty into the coronary sinus?

LEFT: (1) anterior ventricular (2) circumflex branch (3) left marginal branch. RIGHT: (1) right marginal branch (2) posterior interventricular branch

What are the 3 principal branches of the left coronary artery? Where are they located on the heart surface? What are the branches of the right coronary artery and where are the located?

Provides structural support for the heart -anchors cardiocytes and gives them something to pull against -electrical insulation between atria and ventricles - provide elastic recoil to aid in filling heart chamber

What are the functions of the fibrous skeleton?

Thick connections that join cardiocytes end to end. Interdigitating folds - cells interlock. Mechanical junctions - prevent cells from pulling apart. Electrical junctions (gap) - enable cardiocytes to electrically stimulate each other >> creates unified action

What exactly is an intercalated disc and what function is served by each of its components?

S1 - lubb - louder > AV valves CLOSE. S2 - dupp - softer > aortic valve closes.

What factors are thought to cause the first and second heart sounds? When do these sounds occur?

Provides a backup pathway to supply blood if way is blocked

What is the medical significance of anastomoses in the coronary arterial system?

LESS: SR lacks terminal cisternae, no satellite cells (so repair of damaged muscle is almost entirely fibrosis). MORE: mitochondria (because the heart relies exclusively on aerobic respiration)

What organelles are less developed in cardiac muscle than in skeletal muscle? Which are more developed? What is the functional significance of the differences between muscle types?

Volume remains constant, no blood is ejected. Occurs during the contraction and relaxation phases. The semilunar valves are closed, the AV valves have not yet opened & the ventricles are taking in no blood.

What phases of the cardiac cycle are isovolumetric? Explain what this means

Ca2+ entering through slow Ca+ channels prolonging depolarization of membrane and myocardial contraction >>more sustained contraction for expulsion of blood from the heart chambers; as long as the AP is in its plateau, the cardiocytes contract

What produces the plateau in the action potentials of cardiocytes? Why is this important to the pumping ability of the heart?

The SA node in the RIGHT atrium. SA node > AV node > AV bundle (bundle of His) > R & L bundle branches > Purkinje fibers

Where is the pacemaker of the heart located? Trace the path of electrical excitation from there to a cardiocyte of the L ventricle naming each component of the conduction system along the way.

SYSTOLE compresses arteries and aortic valves are open covering opening to coronary arteries. DIASTOLE blood rushes backward against closed valves rushing into coronary arteries

Why do the coronary arteries carry a greater blood flow during ventricular diastole that they do during ventricular systole?

To modify the heart rate and contraction strength.

Why does the heart have a nerve supply, since in continues to beat even without one?