Chapter 14: The cardiovascular system: Heart

The cardiac cycle is divided into which five phases?

(1) passive ventricular filling (2) atrial contraction (3) isovolumetric ventricular contraction (4) ventricular ejection (5) isovolumetric ventricular relaxation.

Where in the conduction system do action potentials propagate most slowly?

Action potentials propagate most slowly through the AV node.

__________ is any activity that works large body muscles for at least 20 minutes, elevates cardiac output and accelerates metabolic rate. ______ to ______ such sessions a week are usually recommended for improving the health of the cardiovascular system.

Aerobics Three to five

True or False: During strenuous activity, a well-trained athlete can achieve a cardiac output double that of a sedentary person, in part because training causes hypertrophy (enlargement) of the heart. Even though the heart of a well-trained athlete is larger, resting cardiac output is about the same as in a healthy untrained person because stroke volume is increased while heart rate is decreased. The resting heart rate of a trained athlete is often only 40-60 beats per minute (resting bradycardia).

All TRUE

True or False: The sinoatrial (SA) node initiates contraction and, if left to itself, would set a constant heart rate of about 100 beats/min. However, tissues require different volumes of blood flow under different conditions. During exercise, for example, cardiac output rises to supply working tissues with increased amounts of oxygen and nutrients. Stroke volume may fall if the ventricular myocardium is damaged or if blood volume is reduced by bleeding. In these cases, homeostatic mechanisms maintain adequate cardiac output by increasing the heart rate and contractility.

All TRUE

True or False: A healthy heart pumps out the blood that entered its chambers during the previous diastole. In other words, if more blood returns to the heart during diastole, then more blood is ejected during the next systole. At rest, the stroke volume is 50-60% of the end-diastolic volume because 40-50% of the blood remains in the ventricles after each contraction (end-systolic volume).

All True

True or False: In addition, the sarcomeres of cardiac muscle fibers have the same zones and bands as those of skeletal muscle fibers due to the arrangement of the thick and thin filaments. The thick filaments contain myosin, and the thin filaments contain actin, troponin, and tropomyosin. The proteins of the thick and thin filaments function in the same way as in skeletal muscle fibers.

All True

True or False: Sustained exercise increases the oxygen demand of the muscles. Whether the demand is met depends mainly on the adequacy of cardiac output and proper functioning of the respiratory system. After several weeks of training, a healthy person increases maximal cardiac output, thereby increasing the maximal rate of oxygen delivery to the tissues. Oxygen delivery also rises because skeletal muscles develop more capillary networks in response to long-term training.

All True

What is the significance of an enlarged Q wave?

An enlarged Q wave may indicate a myocardial infarction (heart attack).

____________ is a progressive disease characterized by the formation of lesions called atherosclerotic plaques in the walls of arteries. It is the most common form of arteriosclerosis, a general term that refers to the _________ and ___________ of arterial walls.

Atherosclerosis thickening; hardening

Decrease in rate of action potential conduction from atria to ventricles: Parasympathetic Regulation Parasympathetic stimulation of the _________ node slows conduction velocity, which decreases the rate at which action potentials are conducted from the atria to the ventricles. The effect of parasympathetic stimulation of the AV node is due to augmented opening of _________ channels, increasing _______ outflow. This hyperpolarizes the AV node membrane, making it more difficult for the AV node to be _________ by action potentials from the ______. So, conduction velocity through the Atrioventricular node _________ and action potentials travel from the atria to the ventricles at a ________ rate.

Atrioventricular acetylcholine-regulated K+ channels (K+ACh); Potassium (K+) excited; atria decreases; slower

If activity of both the SA node and the Atrioventricular node are suppressed, the heartbeat may still be maintained by the ______________ ________, a _______ ________, or _________ _______. These fibers generate action potentials very _________, about ____ to ____ times per minute. At such a low heart rate, blood flow to the brain is ________________.

Atrioventricular bundle, a bundle branch, or Purkinje fibers slowly; 20; 35 inadequate

If the SA node becomes damaged or diseased, the _____________ _______ can pick up the pacemaking task. With pacing by the Atrioventricular node, however, heart rate is ________, only ______ to ____ beats per minute.

Atrioventricular node; slower; 40 to 60;

Increase in rate of action potential conduction from atria to ventricles: Sympathetic Regulation Sympathetic stimulation of the _________ node speeds up conduction velocity, which _________ the rate at which action potentials are conducted from the atria to the ventricles. The effect of sympathetic stimulation of the AV node occurs because of enhanced opening of ___-______ _____ channels, increasing ______ inflow. This depolarizes the AV node membrane, making it easier for AV node cells to be excited by incoming action potentials from the ______. As a result, conduction velocity through the AV node ____________, and action potentials travel from the atria to the ventricles at a _______ rate.

Atrioventricular; increases F-type Na+; Na+ atria increases; faster

________ _________ spontaneously generate action potentials, account for only a very small number of cells in the functional syncytium, are usually grouped together, and contain no myofibrils. A. Contractile fibers B. Autorhythmic fibers

Autorhythmic fibers

You can visualize the heart as a cone lying on its side: The upper, broad portion of the cone is known as the_______. The lower, pointed tip of the cone is referred to as the _______.

Base; Apex

The atria contract _______ the ventricles. This allows the ventricles to fill with blood from the _______, before the ventricles eject blood out of the heart to the rest of the body.

Before; atria

Where in the systemic circulation does blood become deoxygenated?

Blood becomes deoxygenated in the systemic capillaries.

Where in the pulmonary circulation does blood become oxygenated?

Blood becomes oxygenated in the pulmonary capillaries.

________ ________ are tubular structures through which blood flows from the heart to body tissues and then back to the heart.

Blood vessels

________ is a fluid that delivers oxygen and nutrients to cells and removes carbon dioxide and other wastes from cells. It also regulates _____ and _______ ___________, and provides protection against __________.

Blood; pH and body temperature; disease

What are examples of aerobic activities?

Brisk walking, running, bicycling, cross-country skiing, and swimming

****** Phospholamban is a regulatory protein that normally inhibits the ______-________. When phospholamban is phosphorylated, it is ______________, and the inhibition of the ______-_______ is removed.

Ca2+-ATPase inactivated; Ca2+-ATPase

Negative inotropic agents decrease contractility by reducing the amount of _______ available in the ________.

Ca2+; sarcoplasm

_________ are the smallest blood vessels of the body.

Capillaries

________ ________ is the volume of blood ejected from each ventricle of the heart per minute.

Cardiac output (CO)

_________ ________ is the difference between a person's maximum cardiac output and cardiac output at rest.

Cardiac reserve

Heart murmurs in _________ are extremely common and usually do not represent a health condition. These types of heart murmurs are referred to as _________ or ___________ heart murmurs; they often subside or disappear with growth. Although some heart murmurs in adults are innocent, most often an adult murmur indicates a _______ disorder.

Children innocent or functional Valve

Tendonlike, fibrous cords that connect atrioventricular valves of the heart with papillary muscles. A. Smooth muscles B. Papillary muscles C. Chordae tendineae D. Ventricle muscles

Chordae tendineae

__________ _________ constitute the great majority of cells in the functional syncytium, have the necessary myofibrils to contract but do not have the ability to initiate action potentials. A. Autorhythmic fibers B. Contractile fibers

Contractile fibers

__________ _________ _________ is a serious medical problem that affects about 13 million people annually. Responsible for over 500,000 deaths in the United States each year, it is the leading cause of death for both men and women.

Coronary artery disease (CAD)

________ _________ is the enzyme that catalyzes transfer of a phosphate group from creatine phosphate to ADP to make ATP

Creatine Kinase

When heart rate exceeds about 160 beats/min, stroke volume usually ___________ due to the short filling time. At such rapid heart rates, end-diastole volume is ______, and the preload is _________. People who have slow resting heart rates usually have _______ resting stroke volumes because filling time is ___________ and preload is _________.

Declines Less; Lower Large; prolonged; larger

When the heart beats faster, such as during exercise, the amount of time that the heart chambers spend in either diastole or systole ___________, with the duration of ________ decreasing the most.

Decreases; Diastole

Relaxation of cardiac muscle fibers involves _______________ the Ca2+ concentration in the sarcoplasm to resting levels. The sarcoplasmic reticulum of a cardiac muscle fiber contains ________ ________ pumps that actively transport Ca2+ from the sarcoplasm into the sarcoplasmic reticulum. In addition, the sarcolemma of a cardiac muscle fiber contains _______-________ exchangers that actively transport Ca2+ out of the cell in exchange for ________ movement into the cell. As the Ca2+ concentration in the sarcoplasm drops, Ca2+ __________ from troponin, tropomyosin covers the _________-binding sites on _______, and the cardiac muscle fiber ________.

Decreasing Calcium-ATPase Sodium-Calcium; Sodium dissociates; myosin; actin; relaxes

Depolarizing Phase of Contractile Cardiac Muscle Fibers: During the depolarizing phase, ______ voltage-gated _____ channels open. True or False: These channels are referred to as fast because they open very rapidly in response to a threshold-level depolarization. They are the same type of voltage-gated Na+ channels that are present in neurons and skeletal muscle fibers. Opening of these channels increases the membrane permeability to _______ ions, allowing _______ to flow into the cell. This produces a _______ depolarization that _______ the membrane potential to about _______ mV.

Fast; Sodium (Na+) True Sodium (Na+); Sodium (Na+) Rapid; increases; +20 mV

________ ______ is the duration of ventricular diastole. A. Venous return B. Filling time

Filling time

The average person has a cardiac reserve of _____ or ______ times the resting value. Top endurance athletes may have a cardiac reserve ______ or ______ times their resting cardiac output.

Four; Five Seven; Eight

______________ electrically couple cardiac muscle fibers to each other. They allow action potentials to conduct from one cardiac muscle fiber to its neighbors. A. Desmosomes B. Gap Junction

Gap junctions

Cardiac muscle is capable of producing __________ contractions (contractions that vary in strength). These graded contractions do not involve recruitment of a ________ number of muscle fibers because cardiac muscle is a __________ __________: All muscle fibers in the syncytium contract at the ___________ time, so no other muscle fibers can be added to _________ the amount of tension generated. Instead, cardiac muscle produces graded contractions by increasing the _______ of contraction of the existing muscle fibers in the syncytium. This occurs by the addition of more ________ to the sarcoplasm, which in turn increases __________ formation.

Graded Large; functional syncytium; time; increase Strength Calcium; crossbridge

The ________ the end-diastole volume the more forceful the next contraction.

Greater

The _______ is a hollow, muscular organ that is about the size of a closed fist.

Heart

The _______ serves as a pump that generates the pressure needed to circulate blood to the tissues of the body.

Heart

_______ _______ is an arrhythmia that occurs when the electrical pathways between the atria and ventricles are blocked, slowing the transmission of action potentials. The most common site of blockage is the ___________ _______, a condition called atrioventricular (AV) block.

Heart block atrioventricular node

______ _______ is the number of heartbeats per minute

Heart rate

What are some of the cardiovascular benefits of regular exercise?

Helps to reduce blood pressure, anxiety, and depression; control weight; and increase the body's ability to dissolve blood clots by increasing fibrinolytic activity.

Mitochondria are ______ and _________ numerous in cardiac muscle fibers than in skeletal muscle fibers. In a cardiac muscle fiber, the mitochondria take up ______% of the volume of the sarcoplasm; In a skeletal muscle fiber, only _____% of the volume of the sarcoplasm is occupied by mitochondria. This structural feature means that cardiac muscle depends largely on _________ respiration to generate ATP and consequently requires a ___________ supply of oxygen.

Larger; more 25%; 2% aerobic; constant

Transverse (T) tubules and sarcoplasmic reticulum (SR) are also present in cardiac muscle fibers; however, compared to skeletal muscle, the T tubules are _______ abundant and the SR is somewhat _________.

Less; smaller

In contrast to skeletal muscle, cardiac muscle produces ______ of the ATP it needs by _________ glycolysis. Instead, it relies almost exclusively on __________ _________ in its numerous mitochondria. The needed ______ diffuses from blood in the __________ circulation and is released from ___________ inside cardiac muscle fibers. Cardiac muscle fibers use several fuels to power ___________ ATP production. In a person at REST, cardiac muscle's ATP comes mainly from _____________ of fatty acids (60%) and __________ (35%), with smaller contributions from lactic acid, amino acids, and ketone bodies. During exercise, cardiac muscle's use of _________ _______, produced by actively contracting skeletal muscles, rises.

Little; Anaerobic aerobic respiration Oxygen; coronary; myoglobin mitochondrial catabolism; glucose lactic acid

People with severe heart disease may have ______ or ______ cardiac reserve, which limits their ability to carry out even the simple tasks of daily living.

Little; No

During each cardiac cycle, two major heart sounds can be heard with a stethoscope. The first sound (S1), which can be described as a ________ sound, is louder and a bit longer than the second sound. S1 is caused by vibrations associated with closure of the _________ valves soon after ventricular _________ begins. The second sound (S2), which is shorter and not as loud as the first, can be described as a _______ sound. S2 is caused by vibrations associated with closure of the _________ valves at the beginning of ventricular __________. Thus, the heartbeat is heard as lubb-dupp, lubb-dupp, lubb-dupp, and so on.

Lubb Atrioventricular; systole Dupp Semilunar; diastole

The usual rhythm of heartbeats established by the SA node is called?

Normal sinus rhythm

A cardiac muscle fiber usually has ____ nucleus, although an occasional cell may contain two nuclei.

One

A single cardiac cycle includes all of the events associated with ____ heartbeat. A cardiac cycle consists of ____________ and _____________ of the atria plus __________ and _________ of the ventricles.

One diastole (relaxation) and systole (contraction); diastole and systole

The Q-T interval extends from the start of the _____ ________ to the end of the ____ ________. It is the time from the beginning of ventricular ___________ to the end of ventricular ___________. The Q-T interval may be lengthened by? *Hint: 3

QRS complex; T wave depolarization; repolarization 1. Myocardial damage, 2. Myocardial ischemia (decreased blood flow), and 3. Conduction abnormalities.

Deoxygenated blood is dark _______.

RED

Oxygenated blood is bright _________ in color.

RED

Once an action potential is generated in a contractile cardiac muscle fiber, it ultimately causes the muscle fiber to contract by increasing the Ca2+ concentration in the ____________. The sequence of events that connects the muscle action potential to muscle contraction is known as ________-__________ _____________.

Sarcoplasm; excitation-contraction (EC) coupling

When heart rate increases, filling time is ________. Less filling time means a _______ end-diastole volume, and the ventricles may _________ before they are adequately filled. By contrast, when venous return increases, a ________ volume of blood flows into the ventricles, and the end-diastole volume is ____________.

Shorter Smaller; contract Greater; increased

Axons of the parasympathetic postganglionic neurons in turn terminate mainly in the _____________ node and ______________ node, with essentially no inputs to the _____________. Action potentials in parasympathetic postganglionic axons trigger the release of ________, which binds to muscarinic cholinergic receptors on cardiac cells.

Sinoatrial; Atrioventricular; ventricles acetylcholine

In reading an electrocardiogram, the ______ of the waves can provide clues to abnormalities. Larger P waves indicate enlargement of an ______. An enlarged Q wave may indicate a ___________ ________. An enlarged R wave generally indicates enlarged ___________. The T wave is flatter than normal when the heart muscle is receiving _________ ________. For example, in ___________ ___________ disease. The T wave may be elevated in ___________.

Size atrium myocardial infarction ventricles insufficient oxygen; coronary artery hyperkalemia (high blood K+ level)

Final Repolarizing Phase of Contractile Cardiac Muscle Fibers: During the final repolarizing phase of the action potential, the _____ voltage-gated ________ channels fully open. This ___________ the membrane permeability to K+, __________ K+ outflow. At the same time, the ___-______ voltage-gated _______ channels close. This _________ the membrane permeability to Ca2+, ________ Ca2+ inflow. The increase in _______ outflow and decrease in ______ inflow rapidly restore the membrane potential to ________ mV. Once the membrane potential reaches the resting level, the slow voltage-gated K+ channels _______.

Slow; Potassium (K+); Increases; accelerating; L-type; Ca2+ Decreases; Reducing Potassium; Calcium; -90 mV Close

***** Recall that binding of cAMP to F-type channels increases their duration of opening; when fewer cAMP molecules are available, the channels have a greater probability of closing. Closure of the F-type Na+ channels reduces entry of _________ ions into the SA node cell during the pacemaker potential.

Soduim (Na+)

What is stroke volume?

Stroke volume is the amount of blood ejected from the ventricle during each contraction.

Isovolumetric Ventricular Contraction: (Look at Figure 14.19 when studying) Ventricular depolarization causes ventricular _________. While the ventricles are in systole, the atria are in _______. As ventricular systole begins, pressure ______ inside the ventricles and pushes blood up against the ____________ valves, forcing them shut (step 7 in Figure 14.19). For a brief moment, both the ___________ and ____________ valves are closed. This phase of the cardiac cycle is referred to as _________ _____________ contraction. During this interval, cardiac muscle fibers are ___________ and exerting force but are not yet __________. Thus, the muscle contraction is _________ (same length). Moreover, because all four valves are _______, ventricular volume remains the ________ (isovolumic).

Systole Diastole Rises; atrioventricular (AV) atrioventricular (AV); semilunar (SL) isovolumetric ventricular contracting; shortening isometric closed; same

Chemical Regulation of Heart Rate: Ions True or False: Given that differences between intracellular and extracellular concentrations of several ions (for example, Na+ and K+) are crucial for the production of action potentials in all nerve and muscle fibers, it is not surprising that ionic imbalances can quickly compromise the pumping effectiveness of the heart.

TRUE

Other Factors in Heart Rate Regulation: True or False: Age, gender, physical fitness, and body temperature also influence resting heart rate

TRUE

True or False: A variety of factors influence cardiac output by affecting stroke volume and heart rate.

TRUE

True or False: Although the heart has autorhythmic fibers that enable it to beat independently, its operation is governed by events occurring throughout the body. All body cells must receive a certain amount of oxygenated blood each minute to maintain health and life. When cells are metabolically active, as they are during exercise, they take up even more oxygen from the blood. During rest periods, cellular metabolic need is reduced, and the workload of the heart decreases.

TRUE

True or False: Autorhythmic cardiac muscle fibers can initiate their own action potentials because they have unstable resting membrane potentials.

TRUE

True or False: In cardiac muscle, the refractory period (about 250 msec) lasts almost as long as the duration of contraction (300 msec).

TRUE

True or False: Parasympathetic stimulation of the SA node decreases the rate of spontaneous depolarization so that the nodal cells generate action potentials more slowly and heart rate decreases.

TRUE

True or False: An electrocardiogram is a recording of the electrical activity that occurs with each heartbeat.

TRUE

True or False: A positive inotropic effect is an increase in contractility; a negative ionotropic effect is a decrease in contractility.

TRUE

True or False: Adjustments in heart rate are important in the short-term control of cardiac output and blood pressure.

TRUE

True or False: Because ONLY a few Parasympathetic fibers innervate ventricular muscle, parasympathetic stimulation has little or no effect on contractility of the ventricles.

TRUE

True or False: Fibrous rings support the four valves of the heart and are fused to one another.

TRUE

True or False: Regardless of current fitness level, a person's cardiovascular fitness can be improved at any age with regular exercise. Some types of exercise are more effective than others for improving the health of the cardiovascular system.

TRUE

True or False: The chambers of the heart are associated with several large or great blood vessels.

TRUE

True or False: There are no valves guarding the junctions between the venae cavae and the right atrium or the pulmonary veins and the left atrium. As the atria contract, a small amount of blood does flow backward from the atria into these vessels. However, backflow is minimized by a different mechanism: As the atrial muscle contracts, it compresses and nearly collapses the venous entry points.

TRUE; TRUE; TRUE

True or False: Nutrients could NOT possibly diffuse from blood in the chambers of the heart through all of the layers of cells that make up the heart wall. For this reason, the heart wall has its own network of blood vessels, the _________ or __________ circulation

TRUE; coronary or cardiac

_________ refers to a rapid heart rate over 100 beats per minute. _________ refers to a slow heart rate below 60 beats per minute. _________ refers to rapid, uncoordinated heartbeats.

Tachycardia Bradycardia Fibrillation

Which part of the heart has sympathetic innervation but essentially no parasympathetic innervation?

The VENTRICLES have sympathetic innervation but lack parasympathetic innervation.

How much blood remains in each ventricle at the end of ventricular diastole in a resting person? What is this volume called?

The amount of blood in each ventricle at the end of ventricular diastole. Its called the end-diastolic volume It is about 130 mL in a resting person.

Which major blood vessel carries oxygenated blood away from the left ventricle of the heart?

The aorta is the large artery that carries oxygenated blood away from the left ventricle of the heart.

What is the purpose of the chordae tendineae?

The chordae tendineae prevent the cusps of the AV valves from everting into the atria when the ventricles contract.

What are the functions of the desmosomes and gap junctions in the intercalated discs?

The desmosomes mechanically bind cardiac muscle fibers together, which prevents the fibers from pulling apart during contraction. The gap junctions electrically couple cardiac muscle fibers to each other, which allows cardiac muscle to behave as a functional syncytium.

In what two ways does the fibrous skeleton contribute to the functioning of heart valves?

The fibrous skeleton: (1) attaches to the heart valves and (2) prevents overstretching of the valves as blood passes through them.

How does the thickness of the myocardium relate to the workload of a heart chamber?

The greater the workload of a heart chamber, the thicker its myocardium.

What is the purpose of the heart?

The heart is a muscular pump that creates the pressure needed to circulate blood through blood vessels to body tissues.

Considering that there is blood in the chambers of the heart, why does the heart wall need its own blood supply?

The heart wall has its own blood supply because nutrients are unable to diffuse from blood in the chambers through all of the layers of cells that comprise the wall.

Why is the long refractory period of a contractile cardiac muscle fiber important?

The long refractory period of a contractile cardiac muscle fiber prevents the cell from being re-excited until its previous contraction is almost over; consequently, summation of contractions and tetanus do not occur.

Which layer of the heart wall contains cardiac muscle?

The myocardium is the layer of the heart wall that contains cardiac muscle.

Why is the K+ ACh channel so-named?

The name of the K+ACh channel is derived from the fact that this channel is regulated by acetylcholine via activation of a G protein (Gi)

Which component of the conduction system provides the only electrical connection between the atria and the ventricles?

The only electrical connection between the atria and the ventricles is the: Atrioventricular bundle (bundle of His).

What is the pacemaker potential?

The pacemaker potential is the spontaneous depolarization to threshold that occurs in an autorhythmic fiber.

What are the target proteins in this pathway that are phosphorylated to promote an increase in contractility?

The phosphorylated proteins include L-type voltage-gated Ca2+ channels, Ca2+ release channels, phospholamban, and myosin.

When you are exercising, contraction of skeletal muscles helps return blood to the heart more rapidly. Would this tend to increase or decrease stroke volume? What about cardiac output?

The skeletal muscle pump increases stroke volume by increasing preload (end-diastolic volume). It also increases cardiac output, assuming that there is no change in heart rate.

The atria have ______ walls because they deliver blood under less pressure into the ventricles. The ventricles have _______ walls because they pump blood ______ of the heart under higher pressure and over greater distances.

Thin; Thicker; OUT

After the Ca2+ concentration in the sarcoplasm increases, cardiac muscle fibers contract in the same way as skeletal muscle fibers: Ca2+ binds to _________, which in turn undergoes a conformational change that causes _____________ to move away from myosin-binding sites on actin. Once the binding sites are exposed, myosin binds to ________, and the thick and thin filaments begin sliding past one another (sliding filament mechanism).

Troponin; tropomyosin Actin

True or False: Functionally, the heart can be divided into right and left sides, with each side consisting of an atrium and a ventricle.

True

True or False: Positive inotropic agents enhance contractility by increasing the amount of Ca2+ available in the sarcoplasm, during cardiac action potentials.

True

True or False: Sympathetic stimulation of the Sinoatrial node increases the rate of spontaneous depolarization so that the nodal cells generate action potentials more rapidly and heart rate increases.

True

True or False: The heart is innervated by both the sympathetic and parasympathetic divisions of the autonomic nervous system.

True

True or False: A typical cardiac muscle fiber is 50-100 μm long and has a diameter of about 14 μm. Compared to skeletal muscle fibers, most cardiac muscle fibers are ________ in length and _______ in diameter. They also exhibit branching, which gives individual cardiac muscle fibers a _____-______ appearance

True Shorter; smaller stair-step

In an autorhythmic cardiac muscle fiber, an action potential consists of a __________ phase and a ___________ phase. The depolarizing phase of the action potential is caused by the opening of ____-_____ voltage-gated _____ channels. When these channels open, additional ______ enters the cell, and the membrane potential rises above threshold to a positive value. The repolarizing phase of the action potential in an autorhythmic cardiac muscle fiber is caused by (1) the closure of ___-_____ voltage-gated Ca2+ channels and (2) the opening of voltage-gated _______ channels. Opening the voltage-gated K+ channels allows K+ ions to _______ the cell, which decreases the membrane potential back to around ____ mV. Once an action potential is generated in an autorhythmic fiber, it spreads to the __________ _________ of cardiac muscle via gap junctions.

depolarizing; repolarizing; L-type (L for long-lasting because they open for a relatively long period of time).; Ca2+ Ca2+; L-type; Potassium (K+); leave; -60 mV contractile fibers

An intercalated disc contain what two types of cell junctions?

desmosomes and gap junctions

The parallel flow of blood through the systemic circulation is important for two reasons: (1) It allows _______ organ to receive its _____ supply of ________ _______ blood (2) it allows blood ______ to _______ organs to be regulated _________________.

each; own; freshly oxygenated; flow; different; independently

In response to sympathetic stimulation of the heart, norepinephrine __________ a G-protein-signaling pathway that increases contractility by _____________ several target proteins.

activates; phosphorylating

_________ is the pressure that must be exceeded before ejection of blood from the ventricles can occur. A. Postload B. Preload C. Afterload D. Contractility

afterload

As action potentials propagate through the heart, they generate _________ currents that can be detected at the surface of the body. An ____________, is a recording of electrical signals. The electrocardiogram is a composite record of ______ __________ produced by all of the heart muscle fibers during each heartbeat.

electrical electrocardiogram (ECG or EKG) action potentials

Preload is proportional to the _____-_______ ________

end-diastolic volume (EDV)

The ____________ is a thin layer of epithelium that lines the chambers of the heart and covers heart valves.

endocardium

Epithelial cells that line the heart, blood vessels, and lymphatic vessels of the body are referred to as ___________ cells or simply as ____________.

endothelial cells; endothelium

The visceral layer, also called the _________, adheres to the surface of the heart.

epicardium

The coronary arteries branch from the _______ and ______ the heart like a crown encircles the head. While the heart is contracting, little blood ______ through the coronary arteries because they are squeezed _______. When the heart relaxes, however, the ______ pressure of blood in the ________ propels blood through the coronary arteries, into _________, and then into coronary (cardiac) _______. The blood from the coronary veins drains into a large vein called the coronary ________, which empties into the ______ atrium.

aorta; encircle; flows; shut high; aorta; capillaries; veins sinus; right

The term __________ or ___________ refers to an abnormal rhythm as a result of a defect in the conduction system of the heart. The heart may beat irregularly, too quickly, or too slowly.

arrhythmia or dysrhythmia

Problems with the conduction system can result in _____________ (abnormal rhythms) in which the heart beats irregularly, too fast, or too slowly.

arrhythmias

The chordae tendineae prevent the valve cusps from ________ when the ventricles contract and are aligned to allow the valve cusps to tightly close the ________.

everting (opening into the atria); valve

Cardiac muscle does not require any _________ stimulation to contract. Contractions occur because action potentials within cardiac muscle itself are spontaneously generated on a ___________ basis. This built-in rhythm is termed _______________.

external ; periodic; autorhythmicity

If cardiac muscle fibers are stretched beyond their optimal lengths, there are _________ interactions between the thick and thin filaments, the tension that the fibers can produce __________, and stroke volume ________.

fewer; decreases; falls

In addition to cardiac muscle, the heart wall contains connective tissue that forms the _________ _________ of the heart

fibrous skeleton

Contractile fibers become excited and then contract together in response to action potentials conducted to them from autorhythmic fibers via __________ __________.

gap junctions

Capillaries serve as the sites of ______, _________, and _________ exchange between blood and surrounding tissues.

gas, nutrient, and waste

In both circuits, blood is carried away from and then returned to the heart in the following way: Large blood vessels called _______ carry blood away from the heart. Arteries branch to form smaller vessels called ________. Arterioles give rise to even smaller vessels called ________. From capillaries, blood enters larger vessels called _______. Venules give rise to even larger vessels called _______, which carry blood back to the heart.

arteries; arterioles; capillaries; venules; veins

The semilunar valves allow ejection of blood from the heart into _________ but prevent backflow of blood into the ventricles. When the ventricles contract, _______ builds up within the chambers. The semilunar valves open when pressure in the ________ exceeds the pressure in the ________, permitting ejection of blood from the ventricles into the _______ trunk and _______. As the ventricles relax, blood starts to flow ______ toward the heart. This backflowing blood fills the valve cusps, which causes the semilunar valves to _______ tightly.

arteries; pressure; ventricles; arteries; pulmonary; aorta; back; close

When the heart rate is too low, normal heart rhythm can be restored and maintained by surgically implanting an __________ ________.

artificial pacemaker

_________ ________ is a device that sends out small electrical currents to stimulate the heart to contract.

artificial pacemaker

Cardiac muscle usually functions along the __________ limb of the length-tension curve; so, as end-diastolic volume ___________, stroke volume _________.

ascending; increases; increases

The principal cause of coronary artery disease is _______________ of the coronary arteries that supply the heart

atherosclerosis

Atrioventricular (AV) valves lie between the _______ and ___________.

atria and ventricles;

The P-Q interval is the time required for the action potential to travel through the ______, ______ _________, and the remaining fibers of the ___________ __________. When the action potential is forced to detour around scar tissue caused by disorders such as coronary artery disease and rheumatic fever, the P-Q interval ____________.

atria; AV node; conduction system lengthens

To prevent the blood from flowing backward, the heart has four valves, which are: two ______________ valves and two ___________ valves.

atrioventricular; semilunar

The left atrioventricular valve is located between the left ______ and left _______. Because it consists of two cusps, it is also known as the _______ valve. Another name for the left atrioventricular valve is the _________ valve because it resembles a bishop's miter (hat), which is two-sided.

atrium; ventricle bicuspid; mitral

The right atrioventricular valve is located between the right _______ and right __________. It is also called the __________ valve because it consists of three cusps or flaps.

atrium; ventricle tricuspid

The TWO main factors that regulate heart rate are the ___________ nervous system and certain __________. Other factors that contribute to regulation of heart rate? *Hint: 4

autonomic; chemicals (including several hormones and ions) age; gender; physical fitness; body temperature

The accumulation of atherosclerotic plaques in coronary arteries leads to a reduction in ______ _______ to the myocardium. Some individuals have no signs or symptoms; others experience ________ __________, and still others suffer _______ _______.

blood flow angina pectoris (chest pain); heart attacks

The endocardium also continuous with the epithelial cells lining the _______ ________ that are attached to the heart.

blood vessels

What effect does cAMP have on F-type Na+ channels?

cAMP binds to F-type Na+ channels, keeping them open for a longer period of time; this allows more Na+ ions to enter the cell.

Positive inotropic agents increase contractility by increasing the amount of ________ available in the _________ for contraction.

calcium; sarcoplasm

Axons of the sympathetic postganglionic neurons in turn form sympathetic nerves known as ________ ___________ nerves that extend to the _____________ node, _____________ node, and _______________ myocardium. Action potentials in cardiac accelerator nerves trigger the release of _____________, which binds to β1-adrenergic receptors on cardiac cells.

cardiac accelerator; Sinoatrial; Atrioventricular; ventricular norepinephrine

The myocardium consists of _______ muscle and is responsible for the _________ action of the heart.

cardiac; pumping

The cusps of the atrioventricular valves are connected to tendonlike cords called __________ ________ , which in turn are connected to _________ _______, cone-shaped muscle projections located on the inner surface of the ventricles

chordae tendineae; papillary muscles

Agents that alter the heart rate are said to have a ___________ effect.

chronotropic

A pacemaker consists of a battery and impulse generator and is usually implanted beneath the skin just below the _________. The pacemaker is connected to one or two flexible leads (wires) that are threaded through the ________ ______ _______ and then passed into the various chambers of the heart. Many of the new models of pacemakers, namely the activity-adjusted pacemakers, contain _______ and automatically speed up the heartbeat during _________.

clavicle (collarbone) superior vena cava sensors; exercise

The ____________ ____________ ensures that the chambers of the heart contract in a coordinated manner.

conduction system

In _________ _______ ________ there is a loss of pumping efficiency by the heart.

congestive heart failure (CHF)

In a healthy heart, cardiac muscle is usually prevented from stretching beyond its optimal length by ___________ tissues in the wall of the heart, the _________ ________, and the _____________. Thus, cardiac muscle almost always operates along the ascending portion of the length-tension curve.

connective, fibrous skeleton, pericardium

The parietal layer is surrounded by a tough fibrous coat of __________ tissue that _________ the heart in place by attaching to nearby structures in the _____ cavity.

connective; anchors; thoracic

The valves of the heart are composed of ___________ tissue covered by _____________, and they open and close in response to _________ changes as the heart contracts and relaxes. True or False: Each of the four valves helps ensure the one-way flow of blood by opening to let blood through and then closing to prevent its backflow.

connective; endocardium; pressure; TRUE

Essentially, the fibrous skeleton consists of four dense __________ tissue rings that surround the ________ of the heart, fuse with one another, and merge with the interventricular septum.

connective; valves

Because autorhythmic fibers contain essentially no myofibrils, they are unable to ____________.

contract

(2) After the P wave begins, the atria ________. Conduction of the action potential ______ at the ______ _______ because the fibers there have much smaller diameters and fewer gap junctions. (SCENARIO: Traffic slows in a similar way where a four-lane highway narrows to one lane in a construction zone!) The resulting 0.1-sec delay gives the atria time to contract, thus adding to the volume of blood in the _________, before ________ _________ begins.

contract (atrial systole) Slow; AV node ventricles; ventricular systole

_____________ is the forcefulness of contraction of individual ventricular muscle fibers. A. Postload B. Preload C. Afterload D. Contractility

contractility

The second factor that influences stroke volume is myocardial _______________, the strength of contraction at any given preload. Agents that alter contractility are said to have an ___________ effect. Those that increase contractility have a _______ _________ effect, and those that decrease contractility have a ________ ________ effect.

contractility inotropic positive inotropic; negative inotropic

Depolarization causes ____________ and repolarization causes ___________ of cardiac muscle fibers.

contraction; relaxation

Like skeletal muscle, cardiac muscle also produces some ATP from ___________ phosphate. One sign that a myocardial infarction has occurred is the presence in blood of ________ ________. Normally, creatine kinase and other enzymes are __________ within cells. ________ or ________ cardiac or skeletal muscle fibers release creatine kinase into the blood.

creatine Creatine kinase (CK) confined Injured or dying

In contrast to positive inotropic effects, negative inotropic effects _____________ contractility.

decrease

An increase in afterload causes stroke volume to _________ so that more blood remains in the ventricles at the end of ________.

decrease; systole

As afterload increases, the shortening velocity of ventricular muscle fibers ___________.

decreases

Parasympathetic stimulation of the Sinoatrial node ________ heart rate by __________ the rate of spontaneous depolarization in SA node cells so that threshold for an action potential is reached more ________.

decreases; decreasing; slowly

The coronary arteries ________ blood to the heart wall. The coronary veins ______ blood from the heart wall.

deliver; drain

The right atrium receives _____________ blood through what two type of major veins? The ________ vena cava, which brings blood mainly from parts of the body ABOVE the heart; The _________ vena cava, which brings blood mostly from parts of the body BELOW the heart

deoxygenated; 1. The superior vena cava and 2. the inferior vena cava; superior; inferior

In systemic capillaries, blood becomes ___________ as it drops off some of its ______ to cells and picks up ________ _________, a waste product of cellular metabolism.

deoxygenated; oxygen (O2), carbon dioxide (CO2)

The right side of the heart receives ___________ blood from the _________ circulation and pumps it into the __________ circulation. The left side of the heart receives oxygenated blood from the ___________ circulation and pumps it into the _______ circulation.

deoxygenated; systemic; pulmonary; oxygenated; pulmonary; systemic

What is the difference between the base and apex of the heart?

he heart's base is its upper, broad portion; The heart's apex is its lower, pointed tip.

A _________ ________ is an abnormal sound consisting of a clicking, rushing, or gurgling noise that is heard before, between, or after the normal heart sounds, or may mask the normal heart sounds.

heart murmur

Sympathetic stimulation of the Sinoatrial node causes an increase in _______ ___________. This occurs by increasing the rate of spontaneous __________ in Sinoatrial node cells so that threshold for an action potential is reached _____ rapidly

heart rate depolarization; more

The cardiovascular system consists of three interrelated parts such as the ______, ______ _______, and ________.

heart, blood vessels, and blood.

Conditions that can increase afterload include __________________ and ______________ of arteries by ___________.

hypertension (elevated blood pressure); narrowing; atherosclerosis

Thus, for a constant preload: A positive inotropic effect causes an ______________ in stroke volume, and a negative inotropic effect causes a ___________ in stroke volume

increase; decrease

Unlike skeletal muscle fibers, the ends of cardiac muscle fibers are connected to one another by irregular transverse thickenings of the sarcolemma called?

intercalated discs

Cardiac muscle fibers connect to neighboring fibers by __________ _______, which contain ____________ and ______ ________.

intercalated discs; desmosomes; gap junctions

Analysis of an electrocardiogram also involves measuring the time spans between waves, which are called __________ or ___________.

intervals or segments

In mitral insufficiency there is backflow of blood from the ______ _________ into the _________ __________. One cause of mitral insufficiency is ________ ________ _______, in which one or both cusps of the mitral valve protrude into the left atrium during ventricular contraction. ________ _______ _______ is one of the most common valvular disorders, affecting as much as 30% of the population. It is more prevalent in ________ than in ________, and does not always pose a serious threat.

left ventricle; left atrium; mitral valve prolapse (MVP) Mitral valve prolapse; woman; men

The Frank-Starling law is a manifestation of the _______-__________ relationship for cardiac muscle because end-diastole volume influences the length of the _____________ just before contraction begins.

length-tension; sarcomeres

A decreased shortening velocity means that the ventricular muscle fibers eject _____ blood, resulting in a ___________ in stroke volume.

less; decrease

The effect of afterload on stroke volume can be predicted from the _______-_______ relationship of cardiac muscle.

load-velocity

In __________ ________, scar formation or a congenital defect causes narrowing of the mitral valve.

mitral stenosis

The ________ forms the bulk of the heart wall.

myocardium

In aortic stenosis the aortic valve is _________, and in aortic insufficiency there is backflow of blood from the _______ into the _______ ________.

narrowed; aorta; left ventricle

When cardiac muscle fibers are stretched by an increase in end-diastole, the stretch causes the sarcomeres to get closer to their _________ lengths, resulting in _________ tension development when the muscle fibers contract and an _________ in stroke volume.

optimal; greater; increase

In addition to forming a structural foundation for the heart valves, the fibrous skeleton prevents _____________ of the valves as blood passes through them. It also serves as an attachment for bundles of _______ muscle fibers. During atrial contraction, the two atria are pulled _________ toward the fibrous skeleton. During ventricular contraction, the fibrous skeleton _________ the lower chambers as they contract. The connective tissue of the fibrous skeleton also acts as an __________ insulator between the atria and ventricles.

overstretching; cardiac; downward; stabilizes; electrical

Because of the way gas exchange takes place in the pulmonary and systemic capillaries: Blood in pulmonary veins, the LEFT side of the heart, and systemic arteries is _______________. Whereas blood in systemic veins, the RIGHT side of the heart, and pulmonary arteries is ________________.

oxygenated; deoxygenated.

In pulmonary capillaries, blood becomes ___________ as it picks up __________ from inhaled air in the _________ of the lungs and drops off some molecules of _________ ________, which are exhaled from the body.

oxygenated; oxygen; alveoli; carbon dioxide (CO2)

***** F-type channels are involved in producing the _________ potential, the spontaneous depolarization to threshold that occurs in pacemaker cells. Binding of cAMP to F-type channels keeps the channels _______ for a _________ period of time, allowing more _______ ions to enter the cell.

pacemaker open; longer; sodium

Autorhythmic fibers are also known as?

pacemaker cells

In the systemic circulation, blood flows through pathways that are parallel to each other, a design feature known as _______ _______. In most of these pathways, a given portion of blood flows through an artery to only _____ organ and enters only _____ set of capillaries before returning to the heart through a vein. Because of this arrangement, the same portion of blood _____ ______ flow from one organ to the next

parallel flow; one; one; does not

A continually shifting balance exists between sympathetic and parasympathetic stimulation of the heart. At rest, ___________ stimulation predominates. The resting heart rate—about ______ beats/min—is usually lower than the autorhythmic rate of the SA node (about 100 beats/min). True or False: With maximal stimulation by the parasympathetic division, the heart can slow to 20 or 30 beats/min or can even stop momentarily.

parasympathetic 75 TRUE

The pericardium consists of an outer _________ layer and an inner _______ layer

parietal; visceral

Between the parietal and visceral layers of the pericardium is a space called the ___________ cavity that is filled with a thin film of __________ fluid. This fluid, known as _________ fluid, reduces _______ within the pericardium as the heart moves.

pericardial; lubricating pericardial; friction

The heart is enclosed in a membranous sac called the ___________, which confines the heart to its position in the thoracic cavity while allowing sufficient freedom of movement for vigorous and rapid contraction.

pericardium

Those that increase heart rate have a __________ ______________ effect. Those that decrease heart rate have a _________ ______________ effect.

positive chronotropic; negative chronotropic

Parasympathetic innervation of the heart begins with parasympathetic ___________ neurons, which extend from the brain stem via the _______ nerves to synapse with parasympathetic ____________neurons in the heart wall.

preganglionic; brain stem; vagus (X); postganglionic

Sympathetic innervation of the heart begins with sympathetic ___________ neurons, which extend from the ___________ __________ cord to sympathetic _______ ________, where they synapse with sympathetic ___________ neurons.

preganglionic; thoriac spinal;trunk ganglia; postganglionic

________ is the degree of stretch on the heart before it contracts. A. Postload B. Preload C. Afterload D. Contractility

preload

The atrioventricular valves open when __________ in the atria exceeds pressure in the ventricles. When the ventricles are relaxed, the papillary muscles are _______, the chordae tendineae are _______, and blood pushes the atrioventricular valves ______, moving from a higher pressure in the atria to a lower pressure in the ventricles. When the ventricles contract, the pressure of the blood drives the cusps ________ until their edges meet and ________ the opening. At the same time, the papillary muscles _________, which pulls on and __________ the chordae tendineae. This prevents the valve cusps from swinging upward and opening into the _______ in response to the high ventricular pressure. If the atrioventricular valves or chordae tendineae are damaged, blood may __________ into the atria when the ventricles contract.

pressure; relaxed; slack; open; upward; close; contract; tightens; atria regurgitate (flow back)

The septum _________ blood from mixing between the two sides of the heart. The part of the septum located between the two atria is called the ________ septum; The part of the septum between the two ventricles is known as the ______________ septum

prevents; interatrial septum; interventricular septum

The ________ circulation consists of blood vessels that carry blood from the right side of the heart to the alveoli (air sacs) of the lungs and then back to the left side of the heart.

pulmonary

With each beat, the heart pumps blood into TWO CLOSED circuits—the ___________ circulation and the _________ circulation

pulmonary; systemic

The right side of the heart serves as the pump for the ___________ circulation; the left side of the heart serves as the pump for the _________ circulation. Therefore, the heart is actually ______ separate pumps located within the same organ.

pulmonary; systemic; two

If a heart valve cannot be repaired surgically, then the valve must be _________. Tissue (biologic) valves may be provided by ______ donors or _______; sometimes mechanical (artificial) valves made of _______ or ______ are used. The _______ valve is the most commonly replaced heart valve.

replaced; human; pigs; plastic; metal aorta

Autorhythmic fibers can initiate their own action potentials because they have unstable __________ ___________ potentials. The membrane potential starts at about ______ mV and then spontaneously depolarizes to threshold (_____ mV), at which point an action potential is generated. After repolarization, the membrane potential again starts to depolarize and the cycle repeats. The spontaneous depolarization to threshold that occurs in an autorhythmic fiber of cardiac muscle is known as a ___________ __________.

resting membrane; −60 mV; −40 mV pacemaker potential

Certain infectious diseases can damage or destroy the heart valves. One example is __________ ________, an acute systemic inflammatory disease that usually occurs after a streptococcal infection of the throat. The bacteria trigger an immune response in which antibodies produced to destroy the bacteria instead attack and inflame the connective tissues in joints, heart valves, and other organs. Even though _________ ________ may weaken the entire heart wall, most often it damages the mitral and aortic valves.

rheumatic fever; rheumatic fever

Afterload: Ejection of blood from the heart begins when pressure in the _______ ___________ exceeds the pressure in the ________ _________ (about 20 mmHg) and when the pressure in the _______ ________ exceeds the pressure in the _____ (about 80 mmHg). At that point, the higher pressure in the ventricles causes blood to push the __________ valves open. The pressure that must be overcome before a semilunar valve can open is termed the __________.

right ventricle; pulmonary trunk; left ventricle; aorta semilunar afterload

The pulmonary valve, which is located between the ______ ventricle and the __________ trunk. The aortic valve, which is located between the ______ ventricle and the _______.

right; pulmonary; left; aorta

A muscular partition, or _______, separates the right and left sides of the heart.

septum

In cardiac muscle, resting sarcomeres are held at a length that is __________ than the optimum. At such a length, the _____ filaments from each side of the sarcomere overlap, _______ the amount of interaction between the thick and thin filaments. This results in a relatively ______ amount of tension development during contraction that is responsible for the normal stroke volume.

shorter thin; reducing low

Although the right and left ventricles act as two separate pumps that simultaneously eject equal volumes of blood: The right ventricle side has a much _______ workload. The right ventricle pumps blood a ______ distance to the alveoli of the lungs at _______ pressure, and the resistance to blood flow is ______. The left ventricle pumps blood ______ distances to all other parts of the body at ______ pressure, and the resistance to blood flow is _________. Therefore, the left ventricle works much _______ than the right ventricle to maintain the same rate of blood flow. The structure of the two ventricles confirms this functional difference—the muscular wall of the left ventricle is considerably _______ than the wall of the right ventricle

smaller; Short; lower; small; great; higher; larger; harder; thicker

Unlike autorhythmic fibers, contractile cardiac muscle fibers have a __________ resting membrane potential of about _________ mV. This value is a result of the fact that resting contractile fibers are highly permeable to ____ ions and not very permeable to other ions. So the resting membrane potential stabilizes around the ________ equilibrium potential of −90 mV. True or False: When a contractile cardiac muscle fiber is depolarized to threshold by an action potential initiated by an autorhythmic fiber, it produces its own action potential.

stable; −90 mV; Potassium (K+); Potassium (K+) True

A narrowing of a heart valve opening that restricts blood flow is known as _________; failure of a valve to close completely is termed _____________ or ____________.

stenosis; insufficiency or incompetence

The heart is bordered by the ___________ anteriorly, by the ______ laterally, by the _______ ______ posteriorly, and by the ___________ inferiorly.

sternum (breastbone); lungs; vertebral column; diaphragm

Like skeletal muscle fibers, cardiac muscle fibers are ___________ due to repeating sarcomeres consisting of thick filaments and thin filaments that have a regular pattern of overlap. A. Non-striated B. Striated

striated

______ ________the volume of blood ejected by the ventricle during each contraction

stroke volume

Cardiac output equals the _______ ________ multiplied by the _______ ______.

stroke volume; heart rate

The pericardium is a membranous sac that _____________ the heart; The heart wall is composed of three layers: ___________, ________, and ________

surrounds; epicardium, myocardium, and endocardium.

The heart receives innervation from both the _____________ and _____________ divisions of the autonomic nervous system (ANS)

sympathetic and parasympathetic

The _________ circulation consists of blood vessels that carry blood from the left side of the heart to all organs and tissues of the body EXCEPT the alveoli and then back to the right side of the heart.

systemic

Atrial Contraction: (Look at Figure 14.19 when studying) Atrial depolarization causes atrial ________. While the atria are in systole, the ventricles remain in ________. As the atria contract, atrial pressure _________ (step 4 in Figure 14.19) and more blood is forced through the OPEN ___________________ valves into the ventricles. True or False: Atrial contraction contributes a final 25 mL of blood to the volume already in each ventricle (about 105 mL). The end of atrial systole is also the end of ventricular ___________. Thus, each ventricle contains about 130 mL at the end of its ____________ period (diastole). This blood volume is called the _____-______ ________ (step 5 in Figure 14.19). Toward the end of atria systole, the QRS complex appears on the ECG, marking the onset of ______________ depolarization (step 6 in Figure 14.19).

systole; diastole increases; atrioventricular (AV) True Diastole (relaxation) relaxation end-diastolic volume (EDV) ventricular

The heart is located in the ______ cavity, with most of its mass lying to the _______ of the body's midline

thoracic (chest); left

The pulmonary valve and the aortic valve are referred to as semilunar because they are both made up of _______ cusps that are shaped like half ________. The cusps are attached to the _______ of the pulmonary trunk and aorta, and project into the ________ of each of these arteries.

three; moons; walls; lumen

As each chamber of the heart contracts, it pushes a volume of blood into a _________ or out of the heart into an __________.

ventricle; artery

(4) Contraction of ___________ contractile fibers (ventricular systole) begins shortly after the QRS complex appears and continues during the S-T segment. As contraction proceeds from the apex toward the base of the heart, blood is squeezed upward toward the ________ _______.

ventricular semilunar valves

What impact does a decrease in the shortening velocity of ventricular fibers have on stroke volume?

A decreasing in shortening velocity of ventricular muscle fibers causes a decrease in stroke volume.

ALL have NEGATIVE INOTROPIC effects: 1. Inhibition of the ________ nervous system 2. excess ______ ions (from acidosis) 3. increased extracellular _______ levels 4. Drugs known as?

1. sympathetic 2. H+ 3. Potassium 4. Calcium channel blockers

On their own, autorhythmic fibers in the SA node would initiate an action potential about every _____ second, or _____ times per minute. This rate is _______ than that of any other autorhythmic fibers. Because action potentials from the SA node spread through the ____________ ___________ and stimulate other areas before the other areas can generate an action potential at their own, _______ rate, the SA node acts as the ___________ ___________ of the heart. Action potentials from the ___________ __________ system and _______-________ hormones (such as ___________) modify the _______ and __________ of each heartbeat, but they DO NOT establish the fundamental rhythm. In a person at rest, for example, acetylcholine released by the _______________ division of the Autonomic Nervous System ______ SA node pacing to about every _______ second or ____ action potentials per minute. Hence, the resting heart rate is about ______ beats per minute.

0.6; 100 faster; conduction system; slower; natural pacemarker; autonomic nervous; blood-borne; epinephrine; timing; strength parasympathetic; slows; 0.8 or 75 75

In one complete cycle: The atria are in diastole for _____ sec and in systole for ____ sec. The ventricles are in diastole for _____ sec and in systole for _____ sec.

0.7; 0.1 0.5; 0.3

At rest, when the heart rate is 75 beats per minute, a cardiac cycle lasts about ______ sec.

0.8

Decrease in heart rate: Parasympathetic Regulation 1 _________ released from parasympathetic postganglionic neurons binds to __________ receptors in the __________ of an Sinoatrial node cell. 2 Binding of Acetylcholine to its receptor activates an _______ ___ protein 3 Activated inhibitory G protein directly opens a subset of _______ channels known as? 3A. (Opening the K+ channels allows more K+ ions than normal to leave the cell. As a result, the cell membrane ______________, causing the pacemaker potential of the SA node cell to start at a more ___________ value). 4 The activated inhibitory G protein also inhibits _______ _______, causing the production of _______ ________ to decrease. 4A. The decreased concentration of cAMP accelerates the ________ of F-type Na+ channels. ****** 5 _______________ of the SA node membrane (step 3 ) and decreased ____ entry during the pacemaker potential (step 4 ) both have the same effect on the Sinoatrial node cell: They __________ the rate of spontaneous depolarization. As a result, the SA node generates action potentials at a _________ frequency, and heart rate _________.

1. Acetylcholine (ACh); muscarinic; sarcolemma 2. inhibitory G 3. Potassium; acetylcholine-regulated K+ channels or K+ACh channels 3A. hyperolarizes; negative 4. adenylyl cyclase; cyclic AMP (cAMP) 4A. closure 5. Hyperpolarization; Na+; decrease; lower; decreases

What are the two key factors that determine the end-diastole volume?

1. Filling time 2. Venous return

Increase in heart rate: Sympathetic Regulation 1 ______________ from sympathetic postganglionic neurons binds to ____-_____________ receptors in the _____________ of an Sinoatrial node cell. 2 Binding of norepinephrine to the receptor activates a stimulatory ___ _________. 3 Activated Gs stimulates the enzyme ________ _________ to produce __________ __________. 4 * cyclic AMP directly binds to ____-_____ _________ channels in the _________. 5 The increased influx of ________ through F-type channels increases the rate of spontaneous ____________, allowing threshold to be reached _______ quickly. As a result, the Sinoatrial node generates action potentials at a _________ frequency and heart rate ___________.

1. Norepinephrine; β1-adrenergic; sarcolemma 2. G protein 3. adenylyl cyclase; cyclic AMP 4. F-type Sodium; sarcolemma 5. Sodium; depolarization; more; higher; increases

The first half of the pacemaker potential is caused by: (1) the closure of voltage-gated ____ channels that were open during the repolarizing phase of the previous action potential and (2) the opening of ___-______ channels (so-named because they have funny or unusual properties), which are mainly permeable to _____ ions. Closure of the voltage-gated K+ channels ___________ movement of K+ out of the cell (K+ has a higher concentration in the ____________ than in _____________ _________); opening of the F-type channels increases movement of Na+ from _____________ ______ (which has a higher Na+ concentration) into the _____________. The combined effects of these channel activities cause the membrane potential to start drifting slowly above −60 mV. Before the membrane potential reaches threshold, however, the F-type channels ______ and a new set of channels open: ___-______ voltage-gated _____ channels (T for transient because they remain open for only a relatively short period of time). Opening of the T-type voltage-gated Ca2+ channels causes the __________ half of the pacemaker potential. When these channels open, Ca2+ _______ the cell because the Ca2+ concentration is higher in ___________ ___________ than in the ______________. The influx of Ca2+ ___________ the membrane even further, eventually bringing it to threshold. Once threshold is reached, an action potential occurs.

1. Potassium (K+); 2. F-type; 3. Sodium (Na+) 1. decreases; 2. sarcoplasm; 3. extracelluar fluid; 4. extracellular fluid; 5. sarcoplasm 1. close; 2. T-type; 3. Ca2+ 1. second 1. enters; 2. extra cellular fluid; 3. sarcoplasm 1. depolarizes

The wall of the heart consists of what three layers?

1. the epicardium (outer layer), 2. the myocardium (middle layer), 3. the endocardium (inner layer).

Cardiac action potentials propagate through the conduction system in the following sequence: 1. Cardiac excitation normally begins in the ____ _______, cells spontaneously depolarize to threshold by producing a ___________ potential. Once threshold is reached, an action potential is generated and then propagates throughout both ______. Following the action potential, the ______ contract. 2 . The action potential propagates from the atria to the _________ _______. 3. From the atrioventricular node, the action potential enters the ________________ ____________. This bundle is the only site where action potentials can conduct from the atria to the ventricles. Recall that elsewhere the fibrous skeleton of the heart electrically insulates the atria from the ventricles. 4. After propagating along the atrioventricular bundle (bundle of His), the action potential enters both the ________ and _______ ________ branches. 5. From the bundle branches, the action potential propagates to the _________ _______, which in turn conduct the action potential beginning at the _______ of the heart to the remainder of the ventricular myocardium. Then the ventricles contract, pushing the blood upward toward the _________ _________.

1. SA node; pacemaker; atria; atria 2. atrioventricular (AV) node 3. atrioventricular bundle (bundle of His) 4. right and left bundle branches 5. Purkinje fibers; apex; semilunar valves

Which components of the heart contain autorhythmic fibers? *** Repeat question with only the name and no detail****

1. Sinoatrial (SA) node 2. Atrioventricular (AV) node 3. Atrioventricular (AV) bundle 4. Right and left bundle branches. 5. Purkinje fibers

Which components of the heart contain autorhythmic fibers?

1. Sinoatrial (SA) node in the wall of the right atrium close to the opening of the superior vena cava. 2. Atrioventricular (AV) node in the interatrial septum. 3. Atrioventricular (AV) bundle, also known as the bundle of His, in the upper part of the interventricular septum. 4. Right and left bundle branches in the interventricular septum. 5. Purkinje fibers in the ventricular wall.

The two semilunar (SL) valves of the heart are?

1. The pulmonary valve and 2. The aortic valve

Cardiac muscle, as a functional syncytium, consists of what two types of muscle fibers?

1. autorhythmic fibers and 2. contractile fibers.

What are causes of congestive heart failure?

1. coronary artery disease 2. congenital defects 3. long-term high blood pressure (which increases the afterload) 4. myocardial infarctions (regions of dead heart tissue due to a previous heart attack) 5. valve disorders.

What are the four phases of action potentials that occur in contractile cardiac muscle fibers?

1. depolarizing phase 2. initial repolarizing phase 3. plateau phase 4. final repolarizing phase

The autorhythmic fibers of the heart TWO important functions: 1. They act as a pacemaker, setting the rhythm of ____________ excitation that causes _________ of the heart. 2. They form the ______________ ____________, the pathway that rapidly delivers __________ _____________ throughout the heart muscle. Action potentials are able to be conducted throughout the heart by the conduction system because ________ ____________ connect the components of the conduction system to each other and to the contractile fibers of the heart. The conduction system ensures that cardiac chambers become stimulated to contract in a ___________ manner, which makes the heart an effective pump.

1. electrical; contraction 2. conduction system; action potentials; gap junctions; coordinated

Stimulation of the parasympathetic nervous system has TWO main effects on the heart: (1) it decreases ______ _______ (2) it ___________ the rate of action potential conduction from the atria to the ventricles.

1. heart rate 2. Decreases

Stimulation of the sympathetic nervous system has three main effects on the heart: (1) it increases _______ _________ (2) it increases the rate of _________ ________ conduction from the ________ to the ___________ (3) it increases __________

1. heart rate 2. action potential; atria; ventricles 3. contractility

Chemical Regulation of Heart Rate: Which certain chemicals influence both the basic physiology of cardiac muscle and the heart rate? **All depress cardiac activity

1. hypoxia (lowered oxygen level) 2. acidosis (low pH) 3. alkalosis (high pH)

What are the three major factors regulate stroke volume and ensure that the left and right ventricles pump EQUAL volumes of blood?

1. preload 2. contractility 3. afterload

ALL have POSITIVE INOTROPIC effects. 1. Stimulation of the _________ nervous system, hormones such as epinephrine and norepinephrine. 2. increased extracellular _____ levels 3. the drug __________

1. sympathetic 2. Ca2+ 3. digitalis

As an example, consider how an increase in contractility is caused by sympathetic stimulation (Figure 14.23): 1 Norepinephrine released from sympathetic nerve endings binds to ____-____________ receptors in the sarcolemma of a ________ _______ fiber in the _____________ myocardium. 2 Binding of norepinephrine to the receptor activates a stimulatory ____ _________. 3 Activated G protein stimulates ________ _______ to produce the second messenger __________ _______. 4 Cyclic AMP binds to and activates a ________ _________. The activated protein kinase in turn _____________ a variety of proteins with effects that ultimately cause an increase in contractility (see steps 5 through 8). 5 Phosphorylation of L-type voltage-gated Ca2+ channels in the sarcolemma increases the duration of the ________ state of these channels, allowing ________ Ca2+ to move from _________ _________ INTO the sarcoplasm for contraction. 6 Phosphorylation of Ca2+ release channels in the membrane of the sarcoplasmic reticulum (SR) enhances Ca2+ release FROM the __________ _________ _______ INTO the sarcoplasm, providing additional Ca2+ for ______________. 7 Phosphorylation of ____________ in the SR membrane results in an increase in Ca2+ uptake INTO the SR lumen by ______-________ pumps. This speeds ________ and makes _____ Ca2+ available to be released for the next contraction. ****** 8 Phosphorylation of myosin heads of the ______ filaments enhances myosin ATPase activity, which increases the rate of _________ cycling.

1. β1-adrenergic; contractile muscle; ventricular 2. G protein (Gs) 3. adenylyl cyclase; cyclic AMP 4. protein kinase; phosphorylates 5. open; more; extracellular fluid 6. Sarcoplasmic reticulum lumen; contraction 7. phospholamban; Ca2+-ATPase; relaxation; more 8. Thick; crossbridge

The heart serves as a pump that generates the pressure needed to circulate blood to the tissues of the body. Therefore, the heart beats about _______ times every day, which adds up to ____ million beats in a year and about ___ billion beats in an average lifetime.

100,000; 35; 3

Other Factors in Heart Rate Regulation: A newborn baby is likely to have a resting heart rate over ______ beats/min; the rate then gradually _______ throughout life. Adult females often have slightly ______ resting heart rates than adult males, although regular exercise tends to bring resting heart rate _________ in both sexes. A physically fit person may even exhibit _______________. This is a beneficial effect of endurance-type training because a slowly beating heart is more ______ efficient than one that beats more rapidly. ___________ body temperature, as occurs during a fever or strenuous exercise, causes the Sinoatrial node to discharge action potentials more quickly, thereby increasing heart rate. Decreased body temperature __________ heart rate and strength of contraction.

120; declines higher; down bradycardia (a resting heart rate under 60 beats/min); energy increased decreases

In a typical adult male at rest, cardiac output is about ______ L/min. This volume is close to the total blood volume, which is about __ liters. True or False: Thus, your entire blood volume flows through your pulmonary and systemic circulations each minute. Factors that increase stroke volume or heart rate normally increase ________ _______ During mild exercise, for example, stroke volume may increase to 100 mL/beat, and heart rate to 100 beats/min. Cardiac output then would be ____ L/min. During intense (but still not maximal) exercise, the heart rate may accelerate to 150 beats/min, and stroke volume may rise to 130 mL/beat, resulting in a cardiac output of ______ L/min.

5.25 5 True Cardiac output 10 19.5

Plateau Phase of Contractile Cardiac Muscle Fibers: The next phase of the action potential is the plateau, a period of sustained _______________. It is due in part to the opening of _______ voltage-gated _______ channels. When these channels open, _______ ions move from _____________ ________ into the cell. While this is occurring, fast voltage-gated K+ channels _______ and slow voltage-gated K+ channels begin to _______. The slow voltage-gated K+ channels† are so-named because they are activated when the membrane initially _________ but are slow to open. True or False: They are the same type of voltage-gated K+ channels found in neurons and skeletal muscle fibers. Because the fast voltage-gated K+ channels are completely closed and the slow voltage-gated K+ channels are only partially open, the membrane permeability to ______ is relatively low at this time. However, there is just enough efflux of K+ through the ______ voltage-gated K+ channels to balance the _________ influx through the ___-_______ voltage-gated _______ channels, causing the action potential curve to flatten out like a _______. The plateau phase lasts for about ____ sec and the membrane potential of the contractile fiber is close to ____ mV. True or False: By comparison, depolarization in a neuron or skeletal muscle fiber is much briefer, about 1 msec, because it lacks a plateau phase.

Depolarization L-type; Ca2+ Calcium; Extracellular fluid; Close; Open; Depolarizes; True; Potassium (K+); Slow; Calcium (Ca2+); L-Type; Calcium (Ca2+); Plateau 0.2 sec; 0 mV True

____________ mechanically bind cardiac muscle fibers together. They are resistant to mechanical stress, a property that prevents cardiac muscle fibers from pulling apart during contraction. A. Gap Junctions B. Desmosomes

Desmosomes

The atria and ventricles depolarize and then contract at ____________ times because the conduction system routes cardiac action potentials along a specific pathway. The term ___________ refers to the phase of contraction. The phase of relaxation is __________. The ECG waves predict the timing of atrial and ventricular _______ and __________.

Different systole (contraction) diastole (dilation or expansion) systole and diastole.

_____-_______ _______ is the volume of blood that fills the ventricles at the end of diastole.

End-diastole volume

___________ is an infection of the endocardium, which is the inner lining of your heart chambers and heart valves.

Endocarditis

Chemical Regulation of Heart Rate: Hormones Hormones such as ____________ and ____________ (from the adrenal medullae) enhance the heart's pumping effectiveness. These hormones affect cardiac muscle fibers by ______________ heart rate, the rate of action potential conduction from the atria to the ventricles, and contractility. They achieve these functions by binding to the same ______ receptors in cardiac cells Exercise, stress, and excitement cause the ___________ _________ to release more hormones. __________ hormones also enhance cardiac contractility and increase heart rate.

Epinephrine and norepinephrine Increasing β1 adrenal medullae Thyroid

The Frank-Starling law of the heart _________ the output of the right and left ventricles and keeps the same volume of blood flowing to both the systemic and pulmonary circulations. If the left side of the heart pumps a little more blood than the right side, the volume of blood returning to the right ventricle (venous return) ________. The increased end-diastole volume causes the right ventricle to contract more _________ on the next beat, bringing the two sides back into balance.

Equalizes Increases Forcefully

Passive Ventricular Filling: (Look at Figure 14.19 when studying) Our discussion of the cardiac cycle begins during the period when both the atria and ventricles are in diastole. Atrial pressure is _______ than ventricular pressure (step 1 in Figure 14.19) because the atria are filling with blood ____________ to the heart by veins. As a result of the pressure difference, the ______________ valves open, and blood flows from the atria into the ventricles. This phase of the cardiac cycle is known as _________ ________ __________. The term passive is used because no ________ contractions are involved. About ____% of ____________ filling occurs during this phase; the remaining ______% of ventricular filling occurs during _______ contraction. The ___________ valves are closed at this time because aortic pressure is ________ than left ventricular pressure (step 2 in Figure 14.19), and pulmonary trunk pressure is ________ than right ventricular pressure. At the end of atrial diastole, an action potential arises in the _____ _______ and then propagates throughout the atria, causing the atria to _________. _______ __________ is indicated by the P wave on the ECG (step 3 in Figure 14.19).

Higher; returning atrioventricular (AV) passive ventricular filling muscle 80%; ventricular; 20% atrial semilunar (SL); higher; higher SA node; depolarize Atrial depolarization

How does the length-tension curve for cardiac muscle differ from that for skeletal muscle?

In the length-tension relationship for skeletal muscle, resting sarcomeres are held close to their optimal lengths. In the length-tension relationship for cardiac muscle, resting sarcomeres are shorter than the optimum.

Initial Repolarizing Phase of Contractile Cardiac Muscle Fibers: Within a few milliseconds, the fast Na+ channels automatically _________, reducing the membrane permeability to ________. As a result, Na+ inflow ____________. Of the several different types of voltage-gated K+ channels present in a contractile cardiac muscle fiber, a subset known as ______ voltage-gated __________ channels* opens at this time, allowing K+ ions to _________ the cell. The closure of _______ voltage-gated ________ channels and the opening of _________ voltage-gated _______ channels cause the initial repolarizing phase of the action potential. During this phase, the membrane potential begins to ____________.

Inactivate; Sodium (Na+); decreases Fast; Potassium (K+); leave Fast; Sodium (Na+); Fast; (K+) Decrease

A greater preload (stretch) on cardiac muscle fibers prior to contraction _________ their force of contraction. Within limits, the more the heart fills with blood during _________, the greater the force of contraction during __________. This relationship is known as the ________-_______ law of the heart. (In honor of the two physiologists (Otto Frank and Ernest Starling) who first described it)

Increases diastole; systole Frank-Starling

What is Calcium Induced Calcium Release (CICR)?

It refers to the phenomenon by which extracellular Ca2+ triggers the release of additional Ca2+ from the sarcoplasmic reticulum.

Calcium channel blockers inhibit the opening of __-_____ _______-______ ____ channels in the sarcolemma of _________ ________, thereby reducing Ca2+ inflow.

L-type voltage-gated Ca2+ contractile fibers

EC coupling in cardiac muscle involves ___-_____ voltage-gated Ca2+ channels in the membrane of transverse tubules and nearby Ca2+ release channels in the __________ ________ membrane of the ___________ ____________. As the cardiac muscle action potential travels along the sarcolemma and into the T tubules, L-type voltage-gated Ca2+ channels ______, allowing Ca2+ to move from ___________ _________ into the _________________. The entering Ca2+ functions as ________ Ca2+ that _______ to Ca2+ release channels in the sarcoplasmic reticulum, causing the channels to _______ and release an even ________ amount of Ca2+ into the sarcoplasm. The process by which extracellular Ca2+ triggers the release of additional Ca2+ from the sarcoplasmic reticulum is called? About 90% of the calcium needed for contraction of a cardiac muscle fiber comes from the __________ ___________ via ______ ______ ______ ______, and the remaining 10% of the requisite Ca2+ comes from ________ _________.

L-type; terminal cisternal; sarcoplasmic reticulum Open; extracellular fluid; sarcoplasm Trigger; Binds; Open; Larger Calcium-induced calcium release (CICR) sarcoplasmic reticulum; Calcium-induced calcium release; extracellular fluid

The pressures on the right side are considerably ____ than the pressure on the left side of the heart. Each ventricle expels the _______ volume of blood per beat, and the ________ pattern exists for both pumping chambers.

LOWER SAME; SAME

In a typical electrocardiogram, three clearly recognizable waves appear with each heartbeat: The first, called the _____ _____, is a small upward deflection on the electrocardiogram. The P wave represents ________ depolarization, which spreads from the ______ _______ through contractile fibers in both _______. The second wave, called the ________ ________, begins as a downward deflection; continues as a large, upright, triangular wave; and ends as a downward wave. The QRS complex represents ___________ depolarization, as the action potential spreads through ___________ contractile fibers. The third wave is a dome-shaped upward deflection called the ___ _____. It indicates ventricular repolarization and occurs just as the ventricles are starting to ________. The T wave is smaller and wider than the QRS complex because repolarization occurs more ________ than depolarization. During the plateau phase of steady depolarization, the electrocardiogram tracing is ________.

P wave atrial; SA node; atria QRS complex ventricular; ventricular T wave relax Slowly Flat

The P-Q interval, also known as the P-R interval, is the time from the beginning of the _____ ______ to the beginning of the _____ _________. It represents the conduction time from the beginning of _________ excitation to the beginning of __________ excitation.

P wave; QRS Complex Atrial; ventricular

Why is parallel flow through the systemic circulation important?

Parallel flow through the systemic circulation allows each organ to receive its own supply of freshly oxygenated blood, and it allows blood flow to different organs to be regulated independently.

Which of the four phases of the action potential that occur in contractile cardiac muscle fibers is the longest?

Plateau phase

How do positive inotropic agents increase contractility?

Positive inotropic agents increase contractility by increasing the amount of Ca2+ available in the sarcoplasm for contraction.

Chemical Regulation of Heart Rate: Ions Elevated blood levels of ________ or __________ decrease heart rate and contractility. Excess _______ blocks _________ inflow during cardiac action potentials, thereby decreasing the force of contraction, whereas excess __________ blocks generation of action potentials. An increase in extracellular ________ speeds heart rate and strengthens the heartbeat.

Potassium (K+) or Sodium (Na+) Sodium (Na+); Calcium (Ca2+); Potassium (K+) Calcium (Ca2+)

Chemical Regulation of Heart Rate: Ions In particular, the relative concentrations of what three ions have a large effect on cardiac function?

Potassium (K+), Calcium (Ca2+), and Sodium (Na+)

After the right atrium receives deoxygenated blood, then it delivers the deoxygenated blood into the ________ ventricle, which pumps it into an artery called the __________ trunk. The pulmonary trunk divides into the pulmonary ______, which carry the deoxygenated blood to the _______. While in the alveoli of the lungs, blood becomes _________ as it picks up _________ and unloads some of its _________ ________. Once the blood becomes oxygenated in the alveoli of the lungs it is then carried to the ______ atrium via pulmonary _______. From the left atrium the oxygenated blood passes into the ________ ventricle, which pumps the blood into a large artery called the _______. The aorta branches into several smaller _____ that carry the oxygenated blood to all parts of the body except the ________. While in the tissues of the body, blood becomes ________ as it drops off some of its O2 and picks up CO2.

RIGHT; pulmonary; arteries; lungs; oxygenated; oxygen; carbon dioxide Left; veins Left; aorta; arteries; alveoli; deoxygenated

(3) The action potential propagates _______ again after entering the AV bundle. About 0.2 sec after onset of the P wave, it has propagated through the _________ ________, ________ ________, and the entire __________ myocardium. Depolarization progresses down the _______, upward from the _______, and outward from the ____________ surface, producing the _____ complex. At the same time, ________ _______ is occurring, but it is not usually evident in an ECG because the larger QRS complex masks it.

Rapidly bundle branches; Purkinje fibers; ventricular Septum; Apex, Endocardial; QRS atrial repolarization

(6) Shortly after the T wave begins, the ventricles start to _______ (ventricular diastole). By 0.6 sec, ventricular repolarization is complete and ventricular contractile fibers are _________. During the next 0.2 sec, contractile fibers in both the atria and ventricles are relaxed. At 0.8 sec, the P wave appears again on the ECG, the atria begin to _________, and the cycle ________.

Relax Relaxed Relaxed contract; repeats

(5) ____________ of ventricular contractile fibers begins at the apex and spreads throughout the ventricular myocardium. This produces the ____ wave in the ECG about 0.4 sec after the onset of the P wave.

Repolarization T wave

The pulmonary circulation carries blood from the _____ side of the heart to the alveoli of the lungs and then back to the _____ side of the heart; The systemic circulation carries blood from the ______ side of the heart to all ______ and ______ tissues except the ______ and then back to the ______ side of the heart.

Right; alveoli; left; left; organ; body; alveoli; right

Ventricular Ejection: (Look at Figure 14.19 when studying) Continued contraction of the ventricles causes pressure inside the chambers to ______ sharply. When left ventricular pressure surpasses _______ pressure at about 80 mmHg and right ventricular pressure rises above __________ __________ pressure (about 20 mmHg), both _________valves open (step 8 in Figure 14.19). At this point, the ________ _________ phase of the cardiac cycle begins. During this phase, blood is pumped _______ of the heart. The left ventricle ejects about 70 mL of blood into the _______, and the right ventricle ejects the same volume of blood into the __________ _______. The volume remaining in each ventricle at the end of systole, about 60 mL, is the ____-_______ volume (step 9 in Figure 14.19). _______ ________ is the volume ejected per beat from each ventricle. It equals ____-_______ volume minus ____-________ volume. True or False: At rest, the stroke volume is about 130 mL − 60 mL = 70 mL (a little more than 2 oz). The percentage of the end-diastolic volume that is ejected with each stroke volume is called the _______ ________. True or False. Under normal resting conditions, EF is about 54% (70 mL/130 mL × 100). True or False: Changes in stroke volume alter the ejection fraction. Near the end of ventricular systole, the T wave appears on the ECG, marking the onset of ___________ ___________ (step 10 in Figure 14.19).

Rise aortic; pulmonary trunk; semilunar (SL) ventricular ejection OUT Aorta; Pulmonary trunk end-systolic (ESV) Stroke volume; end-diastolic; end-systolic TRUE ejection fraction [(EF): EF = SV/EDV × 100]. TRUE TRUE ventricular repolarization

The S-T segment, which begins at the end of the ____ ______ and ends at the beginning of the _____ _____, represents the time when the ____________ contractile fibers are depolarized during the ______ phase of the action potential. The S-T segment is elevated (above the baseline) in ______ _______ ________ and depressed (below the baseline) when the heart muscle receives _________ _________.

S wave; T wave; ventricular; plateau acute myocardial infarction; insufficient oxygen

(1) A cardiac action potential FIRST arises in the ______ ______. It propagates throughout the atrial muscle and down to the _____ ______ in about 0.03 sec. As the atrial contractile fibers __________, the P wave appears on the ECG.

SA node AV node depolarize

True or False: Cardiac muscle fibers, like neurons and skeletal muscle fibers, have a refractory period, the period of time after an action potential begins when an excitable cell temporarily loses its excitability. The refractory period occurs because voltage-gated ________ channels that are initially activated during the depolarizing phase of the action potential quickly become __________ and must wait until the membrane repolarizes and returns to the ________ state before they are capable of being activated again. In contractile cardiac muscle fibers, the refractory period is _________ (about 250 msec) due to the prolonged _______ phase of the action potential. The refractory period of these fibers lasts almost as long as the duration of ___________ (300 msec). As a result, a contractile cardiac muscle fiber cannot be _________ until its previous contraction is almost over. For this reason, summation of contractions and tetanus ____ ____ occur in cardiac muscle. The advantage is apparent if you consider that the pumping action of the heart depends on alternating _________ and ___________. If cardiac muscle could undergo tetanus, the heart would no longer be able to function as a ______ because it would not have a chance to ______ and ______ with blood—a situation that would be fatal.

True Sodium; inactivated; resting Long; plateau Contraction re-excited DO NOT Contraction (when the heart ejects blood) and Relaxation (when the heart refills). Pump; relax; refill

True or False: There are a few (three) exceptions to parallel flow!!!!! In SOME organs, blood flows between _____ sets of capillaries that are arranged in _______. True or False: The portal system, blood flows from one capillary network into a portal vein and then into a second capillary network before returning to the heart. First exception is, The ______________-____________ portal system that delivers hormones in blood from capillaries in the hypothalamus to capillaries in the anterior pituitary gland. Second exception is, The ___________ portal circulation, which carries absorbed nutrients in blood from capillaries in gastrointestinal organs to capillaries in the liver via the hepatic portal vein. This arrangement allows the liver to store or modify some of the absorbed nutrients before they pass into the general circulation. 3. A final exception to parallel flow in the systemic circulation occurs in the _______, where two sets of capillaries (the glomerulus and peritubular capillaries) are connected by an arteriole

True; Two; series (one right after the other); TRUE; hypothalamic-hypophyseal; hepatic; kidneys

True or False: Because cardiac muscle fibers are interconnected by gap junctions, when an action potential is generated in a mass of cardiac muscle fibers, the action potential quickly spreads to all of the muscle fibers in that mass and then the muscle fibers contract together. Such a mass of interconnected muscle fibers acts as a single, _____________ _______ or __________ _________

True; coordinated unit or functional syncytium

The heart consists of four chambers, which are?

Two upper atria (singular is atrium) and Two lower ventricles

Because the fibrous skeleton of the heart electrically insulates the atria from the ventricles, the atria and ventricles behave as ____ distinct functional syncytiums and therefore contract _____________ of each other.

Two; independently

_______ ________ the volume of blood returning to the right ventricle. A. Filling time B. Venous return

Venous return

The thickness of the myocardium of the chambers varies according to the amount of ________ each chamber has to perform

WORK

Isovolumetric Ventricular: (Look at Figure 14.19 when studying) Relaxation Ventricular repolarization causes ________ ________. As the ventricles relax, pressure within the chambers _______, and blood in the aorta and pulmonary trunk begins to flow __________ toward the regions of ________ pressure in the ventricles. Backflowing blood catches in the valve cusps and closes the __________ valves (step 11 in Figure 14.19). Rebound of blood off the closed cusps of the aortic valve produces the _________ wave on the aortic pressure curve (step 12 in Figure 14.19). After the SL valves close, there is a brief interval when ventricular blood volume does not change because all four valves are _________. This phase is known as ___________ ____________ ____________. As the ventricles continue to relax, the pressure _______ quickly. When ventricular pressure drops below atrial pressure, the ______________ valves open (step 13 in Figure 14.19), and another cardiac cycle repeats as passive ventricular filling begins.

ventricular diastole Falls; backward; lower Semilunar Dicrotic Closed Isovolumertic ventricular relaxation Falls Atrioventricular

Increase in contractility: Sympathetic Regulation Sympathetic stimulation of the __________ ___________ causes an increase in contractility. (Recall that binding of norepinephrine to β1-adrenergic receptors in contractile ventricular fibers activates a G protein signaling pathway that ultimately increases the Ca2+ levels in the sarcoplasm, thereby increasing contractility). As a result, a greater volume of blood is ejected during __________. With a moderate increase in heart rate, stroke volume does not ________ because the increased contractility offsets the decreased _________. With maximal sympathetic stimulation, however, heart rate may reach 200 beats/min in a 20-year-old person. At such a high heart rate, stroke volume is ________ than at rest due to the very short filling time.

ventricular myocardium systole decline; preload lower

The epicardium, also known as the ________ layer of the pericardium, consists of _______ and __________ tissue.

visceral; epithelium and connective