Ch 14 mastering

As blood flows away from the heart, how does overall blood pressure in vessels change? Why?

Blood pressure decreases, because of the effects of friction between the vessel walls and the moving blood.

AV node:

Delay(s) occurs here while atria contract

The anatomy of the intrinsic conduction system causes contraction of the ventricles to begin at the apex and move superiorly. Why is this important?

so blood is forced upward, toward the semilunar valves

The movement of _______________ into the cardiac muscle cell depolarizes the cardiac muscle cell.

sodium and calcium

When the cardiac muscle cell is at rest, the concentration of _____________ is greater on the outside of the cell.

sodium and calcium

Calcium ions are removed from the sarcoplasm of the cardiac cell by the action of the sarcoplasmic reticulum (SR) Ca2+-ATPase pump and which other mechanism?

sodium-calcium exchanger on the sarcolemma

An electrode placement technique that uses three leads in order to record an electrocardiogram.

Einthovens Triangle

AV bundle :

Electrical link(s) between atria and ventricles

An extracellular recording of electrical activity of both autorhythmic and contractile cells of the heart is known as a(n)

Electrocardiogram

Which two mechanisms influence the force of cardiac contraction?

End diastolic volume and sympathetic nervous system stimulation

Which portion of a normal ECG represents ventricular depolarization?

QRS complex

Total time it takes for the ventricular muscle to depolarize and repolarize

QT interval

Which part of the conduction system initiates the depolarizing impulse, which spreads throughout the heart?

SA node

Which part of the intrinsic conduction system normally initiates the depolarizing impulse that causes a heartbeat?

SA node

The ventricles are in their depolarized state

ST segment

SA node:

Set(s) the pace for the entire heart

Ventricular repolarization

T wave

Through which valve must blood pass as it moves from the right atrium to the right ventricle?

Tricuspid

Ordering Electrical and Mechanical Events of the Heart

* P wave * Atrial contraction (systole) * QRS complex * Ventricular contraction (systole) * T wave * Ventricular relaxation (diastole)

Why does blood flow through the cardiovascular system?

Because the heart establishes a pressure gradient

Which cells act as the heart's pacemaker? Why are they the pacemaker cells?

Cells of the SA node are the usual pacemaker, because they are autorhythmic cells and set the pace of the heart rate.

Which of the following can be heard with a stethoscope most easily?

Closing of atrioventricular valves. * The first heart sound, often described as a lubb, corresponds to the closing of the atrioventricular valves. The second heart sound is a sharper and crisper dupp that corresponds to the closing of the semilunar valves. Consequently, the two heart sounds mark the beginning and the end of ventricular systole.

Bundle branches:

Convey(s) the impulse down the interventricular septum

Purkinje fibers:

Convey(s) the impulse throughout the ventricular walls

Which of the following events is NOT represented on an ECG?

atrial repolarization

The beginning of the QRS complex of the electrocardiogram (ECG) immediately precedes which of the following events?

closing of the atrioventricular valves

An increase in sympathetic stimulation of the heart would increase stroke volume by increasing __________.

contractility. * Increased sympathetic activity increases heart contractility. This causes cardiac fibers to contract more forcefully at all levels of preload. Regardless of end diastolic volume, this mechanism increases stroke volume by reducing end systolic volume.

What is the role of heart valves?

Heart valves ensure one-way flow of blood through the heart chambers.

What causes the aortic semilunar valve to close?

greater pressure in the aorta than in the left ventricle

The sinoatrial node is located _______.

in the right atrial wall of the human heart

Which chamber receives blood from the superior and inferior vena cavae?

right atrium

Which heart chamber pumps unoxygenated blood out the pulmonary trunk?

right ventricle

What does the QRS complex represent in the ECG wave tracing?

ventricular depolarization

Isovolumetric relaxation and ventricular filling (two phases of the cardiac cycle) take place during __________.

ventricular diastole

Skeletal muscle is capable of which of the following?

wave summation and fused tetanus

The heart is actually (one, two, or three) pumps?

2

Calculate the cardiac output if heart rate (HR) is 90 beats per minute, stroke volume (SV) is 110 ml/beat, end diastolic volume (EDV) is 140 ml, and end systolic volume (ESV) is 30 ml.

9.9 L/min * Cardiac output is the product of heart rate times stroke volume. Cardiac output increases to meet increased metabolic demand, often by increasing both heart rate and stroke volume at the same time. This occurs, for example, during maximal exercise, when cardiac output may increase to four or five times the resting level.

Which of these is the best definition of an artery?

A vessel that carries blood away from the heart

Which part of the intrinsic conduction system delays the impulse briefly before it moves on to the ventricles?

AV node

Which of these structures conduct(s) action potentials the slowest?

AV node * Action potentials slow down as they pass through the AV node. This gives the atria time to finish contracting before the ventricles are depolarized

Increased pressure in the ventricles would close what valve(s)?

AV valves only

An intracellular recording of electrical activity in either a contractile cell or autorhythmic cell is known as a(n)

Action potential

Consider three blood vessel segments of equivalent length and diameter: vessels A, B, and C. Pressure at the beginning of each segment is as follows: A) P = 100 mmHg; B) P = 80 mmHg; C) P = 60 mmHg. Pressure at the end of each segment is as follows: A) P = 70 mmHg; B) P = 50 mmHg; C) P = 30 mmHg. Which vessel has the greatest blood flow through the described segment?

Flow rate is the same in all three segments. All three vessels have the same resistance and the pressure gradient is the same in all three segments: A) ΔP = 100 - 70 = 30 mmHg; B) ΔP = 80 - 50 = 30 mmHg; C) ΔP = 60 - 30 = 30 mmHg.

Why does the pressure in the arteries and arterioles fall as the blood moves away from the heart?

Friction causes a loss of energy.

The balance between parasympathetic and sympathetic stimulation to the heart controls heart rate.

Increased parasympathetic activity decreases heart rate, and sympathetic activity increases heart rate.

In skeletal muscle cells, action potentials cause the release of calcium from the SR by directly opening SR voltage-gated calcium channels. What causes the release of calcium from the SR in cardiac muscle cells?

Influx of extracellular calcium ions opens ryanodine receptors allowing Ca2+ to flow out of the SR.

A two electrode pair constitutes a __________ which records the electrical activity of the heart.

Lead

Internodal pathways:

Link(s) between the SA node and AV node

Atrial depolarization

P wave

Contraction of the atria results from which wave of depolarization on the ECG tracing?

P wave

Conduction through the atrioventricular (AV) node

PR segment

Describe the pressures in the atria and ventricles that would cause the opening of the AV valves.

Pressure in the atria would be greater than the pressure in the ventricles

Conduction through the atrioventricular (AV) bundle

Q wave

Based on the typical shapes of ECG waves, which wave does this 11th cardiac cycle most resemble?

QRS complex

What is an advantage to the longer duration of cardiac action potential compared to the skeletal muscle action potential?

The longer duration prevents tetanic contraction, which ensures that the heart chambers will relax and refill with blood before the next contraction.

Which of these would cause an increase in blood flow through a vessel?

Vasodilation

Which blood vessels have the lowest blood pressure?

Veins

QRS complex

Ventricular depolarization

Excessive vagal stimulation of the heart will result in _______.

a decrease in heart rate and, eventually, a temporary cessation of the heartbeat

Which of the following is the best definition of an artery?

a vessel that carries blood away from the heart

Most of the oxygen exiting the blood and entering the tissues does so from the ________.

capillaries

Arteries are most accurately defined as blood vessels that ________.

carry blood away from the heart

Modifiers that affect heart rate are _______.

chronotropic

How would a decrease in blood volume affect both stroke volume and cardiac output?

decreased stroke volume and no change in cardiac output. * ecreased blood volume would decrease the end diastolic volume, thus lowering the stroke volume. Although this would initially lead to a decrease in the cardiac output, heart rate would increase because of increased activity of the sympathetic nervous system in an effort to maintain cardiac output.

Would you call this QRS early, on time, or late compared to when other QRS complexes are formed?

early

What does the ECG wave tracing represent?

electrical activity in the heart

Which of the following would increase heart rate?

epinephrine and norepinephrine

Arrange these elements of the intrinsic conduction system in the order that a depolarizing impulse travels during a normal heartbeat.

first element depolarized * SA node * Internodal pathways * AV node * AV bundle * Bundle branches * Purkinje fibers last element depolarized

Along with nutrients, hormones, water, and gases, the cardiovascular system also transports _____________

immune cells, cellular wastes, heat. * All of these substances are transported by the cardiovascular system.

The effect of the sympathetic nervous system on the heart is to _______.

increase the heart rate and increase the force of contraction

How would an increase in the sympathetic nervous system increase stroke volume?

increased contractility. * by increasing available calcium), thus increasing stroke volume. Contractility causes an increase in stroke volume by decreasing end systolic volume; it does not change end diastolic volume.

By what mechanism would an increase in venous return increase stroke volume?

increased end diastolic volume. * an increase in venous return increases the end diastolic volume. The fibers are stretched more, resulting in an increase in the force of contraction (preload, or the Frank-Starling Mechanism).

Which of the following would increase cardiac output to the greatest extent?

increased heart rate and increased stroke volume. * cardiac output = heart rate x stroke volume.

Modifiers that affect the force of contraction of the heart are _______.

inotropic

The total refractory period of cardiac muscle _______.

is longer than the total refractory period for skeletal muscle

Put the phases of the cardiac cycle in the correct order, starting after ventricular filling.

isovolumetric contraction, ventricular ejection, isovolumetric relaxation

Which heart chamber receives blood from the pulmonary veins?

left atrium

Which chamber pumps oxygenated blood out the aorta to the systemic circuit?

left ventricle

Which of the following is correct about the filling of the ventricles?

most blood flows passively into the ventricles through open AV valves.

As part of a blood drive on campus for the American Red Cross, you and your friends have just donated 500 ml of blood. You are now relaxing at the student lounge, waiting for A&P lab to begin. Unfortunately, even though you are thirsty, you haven't bothered to buy yourself a drink. Other than a little soreness of the skin and tissue around your median cubital vein, you feel fine. How has your 500 ml decrease in blood volume most likely affected your cardiac output, heart rate, and stroke volume?

no change in cardiac output, increased heart rate, decreased stroke volume

The autorhythmicity of cardiac pacemaker cells is made possible by the reduced permeability of _______.

potassium

The repolarization of cardiac muscle is due to _______

potassium exiting the cell

The electrocardiogram represents ________.

the electrical activity of all of the cardiac muscle cells

Heart rate (HR):

the number of heart beats per minute

Which branch of the autonomic nervous system dominates after a large meal?

the parasympathetic branch

Which of the following statements best describes the electrical events recorded by an ECG?

the sum of the electrical activity of all cells in the heart

End systolic volume (ESV):

the volume of blood in one ventricle after contraction

End diastolic volume (EDV):

the volume of blood in one ventricle before contraction

Stroke volume (SV):

the volume of blood per heart beat pumped out by one ventricle

Venous return (VR):

the volume of blood per minute flowing into one atrium

Cardiac output (CO):

the volume of blood per minute pumped out by one ventricle

Which blood vessels return blood to the heart?

veins