Test One Flashcards

Question

What are veins

Answer 1

Toward the heart Compliant Thin walls with large lumens Valves in limbs and inferior to the heart Three tissue layers, tunics: intima, smooth, no elastic membrane media, thin, with collagenous fibers and nerves, no elastic membrane externa, thick, with collagenous fibers, smooth fibers, smooth muscle and nerves Carry blood toward heart More compliant Thin vessel wall, irregularly shaped, larger lumen Medium- positioned inferior have valves correct blood flow Tunic Intima- thinner Opposite direction of blood flow Compliant- stretches easily, extends Thinner walled, lumen is irregular shaped Not wavy Intima, smooth, no elastic membrane Media- collagen External- thickest, smooth muscle appearance Venule- closest to capillary Vein are resevoir of blood- 60%, processing more blood than arteries Valves help push the blood flow towards the heart

Answer 2

Continuous: water, small solutes and lipid- soluble material Fenestrated: rapid exchange of water and large solutes peptides Sinusoid (rarest): exchange of largest molecules (plasma, cells) in bone marrow, liver and glands Other vessel Capillary bed Arteriole and venule empty into smaller vessels- capillary, network= bed Have different openings in the layers Sinusoid- many openings, let cell through support infiltration of cells, lymph glands Continuous- small solutes fee started- middle Have full membrane but can allow for rapid exchange of water and large solutes Lecture Mesh network- capillary bed- vessel circuits connect to cappilary on either side Venule- receives from capillary Filtration or exchange, here need higher chance for exchange, need to exhange many things- extra peatrive layers allow for molecules to go through Most perforated , exchanges largest

Answer 3

Elastic arteries and venae cavae have the largest diametiencfralusdt(ecsdt.?losest to the heart) Arterioles and venules have the smallest diameter (closest to the capillary beds) Different properties and factors of changes of blood vessels They have different diamanter Aorta and artery- larger so are veins Higher diameter, more blood flow Larger diameter, lower resistance Increasing diameter Dec resistanxce Lecture Blood vessel types and diameter Largest vessel, largest diameter Order of vessel in closest to farthest from heart Dimatater, directly proportional to blood flow, inversely related to resistance, higher diameter, lower resistance

Answer 4

Areas with vessels that have small diameter have the highestincfcalusdrteosdt.?ss- sectional area Increase in cross- sectional area increases surface available for exchange Cross sectional area Area with vessels that have smal diameter have large area What it to be larger so more elements can be exchanged through the tissues and body, not getting diameter , maximize space Small diameter- highest area Increases exhange of elements

Answer 5

Blood flows fastest in the arteriesI with large diameter Blood flows slowest in vessels with small diameters High blood flow in the largest diameter Connected to some of the layers lowest in small diameters Veins have s larger diameter, why not as fast as arteries, they are more compliant and brings it toward heart, have harder time As get closer to cappiliary want it to slow down, allows for exchange High elastic pressure= artery Venous- more compliance, less muscle Artery work at higher speeds and pressures Veins- don’t reach speed, more compliant and agianst gravity

Answer 6

There is a lot more blood volumeI that needs to be supported In large part, this blood volume needs to be circulated againts gravity One-way valves to ensure unidirection al flow of blood (in limbs and vessels inferior to the heart) The valves help the velocity inc, blood pushes through valve closes so there’s no backflip, helps push good up towards eart Veins have more challenges, upport more blood volume Artery can help take away Blood needs to be circulated against gravity One way vta;be help push blood up Valves open one at a time, needs to pass through for valve to open first

Answer 7

Pressure is the highest in arteries with the largest diameter and most elastic/muscular tunics Pressure is the lowest in the largest veins Blood pressure changes relates to large musculature tunic, thicker walled (muscular system veins Related to resistance Tunica media- thickest= highest power

Answer 8

Blood pressure: peak systolic over peak diastolic Arterial pressure is higher during ventricular systole (walls contract) and lower during diastole (walls stretch and recoil) There is a pressure difference between the vessels, peace vessels in systole and lowest pressure in diastole Arterial pressure is the average of the two contractile systems Systolic- walls contracting Lowest when diastole- walls of ventricles in stretch and recoil Measuring this pressure- good presssure Can help tell about heart health Pressure during contraction and relaxation Mean of presssure= average between relation and contraction

Answer 9

Bulk flow: fluid moves I from pressure area (capillary bed) lower pressure area (tissues) via filtration Net filtration pressure is the interaction of the hydrostatic (the force exerted by the blood in a vessel - forces fluids out of capillary) and osmotic pressures (the movement of fluid from the interstitial fluid - forces fluids into the capillary) Filtration Hydrostatic pressure > osmotic pressure Positive net filtration (fluid exits capillary, filtration) No net movement ydrostatic pressure = osmotic pressure 0 net filtration (no fluid movements) Reabsorption Hydrostatic pressure < osmotic pressure Negative net filtration (fluid enters capillary, reabsorption) Surface area exchange and increase- exchange of blood and materials in tissue Exchange in capillary beed Fluid moves fom higher pressure(in blood vessel To lower pressure area- tissue Done via filtration Can tell which direction it’s going out or in Out- filtration In- venous end- becomes venule drains into veins and back to heart Return of the fluid- reabsorptiuon Direction of bulk flow- can determine through the filtration pressure-NFP Interaction of two pressures(hydrostatic- by blood vessel) osmotc(movement of fluid from interstitial fluid- moves back into capillary bed) Higher pressure in capillary bed or higher osmotic pressure- positive net filtration- fluids moving from high to low, exiting capillary bed- filtration Hydrostatic Lower than osmotic- negative net filtration The fluid is moving bac- higher to lower pressure - reabsoprion Equalized- zero movement Bulk flow- fluid moves from high to low pressure via filtration Hydrostatic- pressure in blood vessels Osmotic pressure outside space Are they moving from high to low- hydrostatic high and osmotic low- move from high to low Hydrostatic pressure is low and osmotic is high, allows material into blood to be sent back

Answer 10

Cells, tissues, organs and organ systems of the body are impacted by or depend on the cardiovascular system Delivering hormones Transports white blood cells, antibodies and excess fluids from lymphatic Transport for oxygen and carbon dioxide Sexual arousal and erection, delivery of sex hormones Delivers resting circulation to kidneys for filtering Connections between blood and different body systems These are the key riles Major vessels- connect back to heart

Answer 11

Pulmonary veins- right vs left- from and to lung Aortic arch- ascending and descending aorta Branches into 3 main arteries- brachiceohlaic trunk, common carotid artery Most to left- subclavia atery’ Bring blood into right atriria Right Inferior and superior vena cava Pulmonary trunk branches into pulmonary artery Aortic arch Coming from left atrium You should be able to locate: - aorta (ascending and descending) - aortic arch - vena cave (inferior and superior) - pulmonary arteries (and pulmonary trunk - the base leaving the right ventricle) - pulmonary veins

Answer 12

Brachiocephlaic branch Scamming carotid artery descending aorta beach SES into ilia and femoral artery - into legs Braciocheplaic trunk and sublavian, auxiliary artery connect to upper limb Veins Systemic veins bringing back to hart- right side Brachiocephalic vein, axillary and cephalic vein Iliac vein and femoral vein Jugular vein] Subclaviean You should be able to locate: - common carotid artery - brachiocephalic trunk - internal and external jugular vein - subclavian artery and vein - axillary vein and artery - brachial artery and vein - radial and ulnar artery and vein - renal artery and vein - iliac artery and vein - femoral artery and vein - tibial and fibular artery and vein

Answer 13

Amount of blood pumped by each ventricle in one minute

Answer 14

Heart rate and stroke volume We assess or measure cardiac function through cardiac output. Specifically cardiac output (amount of blood pumped through the heart in a minute) depends on heart rate and stroke volume. Heart rate is affected by autonomic innervation, hormones (see Slide 4) as well as fitness level and age

Answer 15

contractions per minute or beats per minute • Affected by sympathetic and parasympathetic innervation. Here you are seeing how heart rate is affected by autonomic innervation. Vagus nerve has a parasympathetic signal to the heart to slow down the heart rate, while the sympathetic cardiac nerves send a signal to increase the heart rate. You can see some examples of when parasympathetic and sympathetic nerves can be activated in the slide but you don’t have to remember all the details yet - we will come back to this when we talk about regulation of heart function in more details. We already discussed the regular action potential signal through the conducting cells of the heart.

Answer 16

Stroke volume (SV): how much volume of blood can the heart pump • SV = end-diastolic volume (EDV) - end-systolic volume (ESV)

Answer 17

Stroke volume (how much volume of blood can the heart pump) is determined by heart size, fitness levels, gender, contractility of the heart muscles, duration of contraction, how much blood did the heart receive (preload) and how much resistance is there to sending blood out of the heart (after load). You will discuss cardiac output in relation to exercise in much more detail in next case study in tutorials (just before your first term test).

Answer 18

The higher the EDV (more blood enters the heart), the higher the stroke volume. The lower the amount of blood left in the heart (ESV), the higher the stroke volume. EDV depends on preload, which is how fast and how much venous blood is returning to the heart (more blood or faster return increases EDV, thus increasing SV). ESV depends on resistance too flow (after load) and contractility of the heart . The higher the resistance or afterload, the more blood is left in the heart or higher the ESV, which therefore reduces SV. The higher the contractility, the less blood stays in the heart so the ESV is lower, meaning that SV is higher Increase in EDV increases SV . Decrease in EDV = decreases SV • Increase in ESV decreases SV • Decrease in ESV increases SV

Answer 19

• HR affected by autonomic innervation, hormones and input by venous return • SV affected by preload, contractility, and afterload The higher the EDV (more blood enters the heart), the higher the stroke volume. The lower the amount of blood left in the heart (ESV), the higher the stroke volume. EDV depends on preload, which is how fast and how much venous blood is returning to the heart (more blood or faster return increases EDV, thus increasing SV). ESV depends on resistance too flow (after load) and contractility of the heart . The higher the resistance or afterload, the more blood is left in the heart or higher the ESV, which therefore reduces SV. The higher the contractility, the less blood stays in the heart so the ESV is lower, meaning that SV is higher.

Answer 20

Parasympathetic nervous system; release of acetylcholine; decreased levels of CO2, high blood pressure; rest; decreased thyroid hormones; decrease in calcium; increase in sodium and/or potassium; decrease in body temperature; opiates and depressants Sympathetic nervous system; release of norepinephrine; increased levels of CO2, low blood pressure; exercise or anticipation of physical exercise; increased thyroid hormones; decrease in sodium, potassium and/or calcium; increase in body temperature; stimulants (nicotine, Here you are seeing how heart rate is affected by autonomic innervation. Vagus nerve has a parasympathetic signal to the heart to slow down the heart rate, while the sympathetic cardiac nerves send a signal to increase the heart rate. You can see some examples of when parasympathetic and sympathetic nerves can be activated in the slide but you don’t have to remember all the details yet - we will come back to this when we talk about regulation of heart function in more details. Parasympathetic nervous system; release of acetylcholine; decreased levels of CO2, high blood pressure; rest; decreased thyroid hormones; decrease in calcium; increase in sodium and/or potassium; decrease in body temperature; opiates and depressants. Sympathetic nervous system; release of norepinephrine; increased levels of CO2, low blood pressure; exercise or anticipation of physical exercise; increased thyroid hormones; decrease in sodium, potassium and/or calcium; increase in body temperature; stimulants (nicotine, caffeine)

Answer 21

Vascular resistance: friction between blood and vessel walls; depends on diameter and length of vessel, ΔP represents the difference in pressure, r4 is the radius (one-half of the diameter) of the vessel to the fourth power, η is the Greek letter eta and represents the viscosity of the blood, λ is the Greek letter lambda and represents the length of a blood vessel. By examining this equation, you can see that there are only three variables: viscosity, vessel length, and radius, since 8 and π are both constants. The important thing to remember is this: Two of these variables, viscosity and vessel length, will change slowly in the body. Only one of these factors, the radius, can be changed rapidly by vasoconstriction and vasodilation, thus dramatically impacting resistance and flow. Resistance is inversely proportional to the radius of the blood vessel and a slight increase or decrease in diameter causes a huge decrease or increase in resistance. Most of the time and in the summary diagram above, we are talking about arteriole vasoconstriction or vasodilation but it does happen elsewhere, like in the veins. Venoconstriction increases the return of blood to the heart or increases the preload of the cardiac muscle

Answer 22

Neural mechanisms that regulate blood chemistry and pressure are: sympathetic/parasympathatic innervation as well as overall radius of peripheral vessels (vasconstriction/vasodilation) Neural mechanisms Blood pressure- cardiac centre, vasomotor centers Sympathetic stimulation: increasing cardiac output and increasing blood flow Parasympathetic sumulation. decreasing cardiac output and decreasing blood flow Blood chemistry Cardiac Vasomotor centers Vasoconstriction of most peripheral vessels - norepinephrine (NE): decreasing flow, veins increasing flow Vasodilation of select peripheral vessels - primarily acetylcholine and nitric oxide (NO)

Answer 23

Inc blood pressure Increased baroeexeptor firing Increased inhibition of cardiac and decrease in activity of accelerator and vasomotor centres Inc cardiac inhibitor centres Lower cardiac accelerator centres Decrease vasomotor centre Decrease cardiac output HR and SV (decrease in venous return) decreases CO Inc vasodilation Increase in diameter decreases resistance Blood pressure drops When blood pressure rises too high, the baroreceptors fire at a higher rate and trigger parasympathetic stimulation of the heart. As a result, cardiac output falls. Paraympathetic stimulation of the peripheral arterioles will also decrease, resulting in vasodilation. Combined, these activities cause blood pressure to fall.” Blood Pressure (BP)=Cardiac Output (CO)×Peripheral Resistance Here, peripheral resistance refers to the resistance the blood encounters as it flows through the arteries. If blood pressure increases and peripheral resistance remains constant, it may impact cardiac output.

Answer 24

Dec blood pressure Dec baroreceptor firing Dec cardiac inhibitors centers Inc cardiac accelerators Inc vasomotor centers Inc cardiac output Inc vasodilation Blood pressure increase When blood pressure decreases, the baroreceptors fire at a slower rate and trigger sympathetic stimulation of the heart. As a result, cardiac output rises Sympathetic stimulation of the peripheral arterioles will also decrease, resulting in vasoconstriction. Combined, these activities cause blood pressure to raise.”

Answer 25

Endocrine mechanisms that regulate blood volume and pressure are related to hormones from renal, adrenal system, such as EPO, ADH, Aldestorone and others help regulate the radius of peripheral vessels (vasconstriction/vasodilation), which affects blood pressure and its regulation

Answer 26

For example, when blood pressure and blood volume is low, renin (angiotensin II) and EPO secretion increases, which together increase thirst and RBC formation, which together increase blood volume. Blood volume increases while also sympathetic NS increases cardiac output and peripheral vasoconstriction, which ultimately increases blood pressure as well

Answer 27

force the ventricles must develop to effectively pump blood against the resistance in the vessels

Answer 28

movement of blood through a vessel, tissue, or organ that is usually expressed in terms of volume per unit of time

Answer 29

force exerted by the blood against the wall of a vessel or heart chamber; can be described with the more generic term hydrostatic pressure

Answer 30

cardiac output (CO) amount of blood pumped by each ventricle during one minute; equals HR multiplied by SV

Answer 31

cardiac plexus paired complex network of nerve fibers near the base of the heart that receive sympathetic and parasympathetic stimulations to regulate HR

Answer 32

cardiac reflexes series of autonomic reflexes that enable the cardiovascular centers to regulate heart function based upon sensory information from a variety of visceral sensors

Answer 33

also, preload) the amount of blood in the ventricles at the end of atrial systole just prior to ventricular contraction

Answer 34

amount of blood remaining in each ventricle following systole

Answer 35

filling time duration of ventricular diastole during which filling occurs

Answer 36

number of times the heart contracts (beats) per minute

Answer 37

also, end diastolic volume) amount of blood in the ventricles at the end of atrial systole just prior to ventricular contraction

Answer 38

stroke volume (SV) amount of blood pumped by each ventricle per contraction; also, the difference between EDV and ESV

Answer 39

larger number recorded when measuring arterial blood pressure; represents the maximum value following ventricular contraction

Answer 40

relaxation of the smooth muscle in the wall of a blood vessel, resulting in an increased vascular diameter

Answer 41

irregular, pulsating flow of blood through capillaries and related structures

Answer 42

volume of blood contained within systemic veins in the integument, bone marrow, and liver that can be returned to the heart for circulation, if needed

Answer 43

largest artery in the body, originating from the left ventricle and descending to the abdominal region where it bifurcates into the common iliac arteries at the level of the fourth lumbar vertebra; arteries originating from the aorta distribute blood to virtually all tissues of the body

Answer 44

arc that connects the ascending aorta to the descending aorta; ends at the intervertebral disk between the fourth and fifth thoracic vertebrae

Answer 45

arteriole (also, resistance vessel) very small artery that leads to a capillary

Answer 46

artery blood vessel that conducts blood away from the heart; may be a conducting or distributing vessel

Answer 47

initial portion of the aorta, rising from the left ventricle for a distance of approximately 5 cm

Answer 48

axillary artery continuation of the subclavian artery as it penetrates the body wall and enters the axillary region; supplies blood to the region near the head of the humerus (humeral circumflex arteries); the majority of the vessel continues into the brachium and becomes the brachial artery

Answer 49

axillary vein major vein in the axillary region; drains the upper limb and becomes the subclavian vein

Answer 50

blood colloidal osmotic pressure (BCOP) pressure exerted by colloids suspended in blood within a vessel; a primary determinant is the presence of plasma proteins

Answer 51

movement of blood through a vessel, tissue, or organ that is usually expressed in terms of volume per unit of time

Answer 52

force blood exerts against the walls of a blood vessel or heart chamber

Answer 53

force exerted by the blood against the wall of a vessel or heart chamber; can be described with the more generic term hydrostatic pressure

Answer 54

brachiocephalic artery single vessel located on the right side of the body; the first vessel branching from the aortic arch; gives rise to the right subclavian artery and the right common carotid artery; supplies blood to the head, neck, upper limb, and wall of the thoracic region

Answer 55

brachiocephalic vein one of a pair of veins that form from a fusion of the external and internal jugular veins and the subclavian vein; subclavian, external and internal jugulars, vertebral, and internal thoracic veins lead to it; drains the upper thoracic region and flows into the superior vena cava

Answer 56

capillary smallest of blood vessels where physical exchange occurs between the blood and tissue cells surrounded by interstitial fluid

Answer 57

capillary bed network of 10–100 capillaries connecting arterioles to venules

Answer 58

right common carotid artery arises from the brachiocephalic artery, and the left common carotid arises from the aortic arch; gives rise to the external and internal carotid arteries; supplies the respective sides of the head and neck

Answer 59

branch of the aorta that leads to the internal and external iliac arteries

Answer 60

one of a pair of veins that flows into the inferior vena cava at the level of L5; the left common iliac vein drains the sacral region; divides into external and internal iliac veins near the inferior portion of the sacroiliac joint

Answer 61

degree to which a blood vessel can stretch as opposed to being rigid

Answer 62

most common type of capillary, found in virtually all tissues except epithelia and cartilage; contains very small gaps in the endothelial lining that permit exchange

Answer 63

portion of the aorta that continues downward past the end of the aortic arch; subdivided into the thoracic aorta and the abdominal aorta

Answer 64

diastolic pressure lower number recorded when measuring arterial blood pressure; represents the minimal value corresponding to the pressure that remains during ventricular relaxation

Answer 65

(also, conducting artery) artery with abundant elastic fibers located closer to the heart, which maintains the pressure gradient and conducts blood to smaller branches

Answer 66

continuation of the external iliac artery after it passes through the body cavity; divides into several smaller branches, the lateral deep femoral artery, and the genicular artery; becomes the popliteal artery as it passes posterior to the knee

Answer 67

drains the upper leg; receives blood from the great saphenous vein, the deep femoral vein, and the femoral circumflex vein; becomes the external iliac vein when it crosses the body wall

Answer 68

fenestrated capillary type of capillary with pores or fenestrations in the endothelium that allow for rapid passage of certain small materials

Answer 69

In the cardiovascular system, the movement of material from a capillary into the interstitial fluid, moving from an area of higher pressure to lower pressure

Answer 70

hepatic portal system specialized circulatory pathway that carries blood from digestive organs to the liver for processing before being sent to the systemic circulation

Answer 71

large systemic vein that drains blood from areas largely inferior to the diaphragm; empties into the right atrium

Answer 72

lumen interior of a tubular structure such as a blood vessel or a portion of the alimentary canal through which blood, chyme, or other substances travel

Answer 73

mean arterial pressure (MAP) average driving force of blood to the tissues; approximated by taking diastolic pressure and adding 1/3 of pulse pressure

Answer 74

muscular artery (also, distributing artery) artery with abundant smooth muscle in the tunica media that branches to distribute blood to the arteriole network

Answer 75

force driving fluid out of the capillary and into the tissue spaces; equal to the difference of the capillary hydrostatic pressure and the blood colloidal osmotic pressure

Answer 76

one of two branches, left and right, that divides off from the pulmonary trunk and leads to smaller arterioles and eventually to the pulmonary capillaries

Answer 77

pulmonary circuit system of blood vessels that provide gas exchange via a network of arteries, veins, and capillaries that run from the heart, through the body, and back to the lungs

Answer 78

pulmonary trunk single large vessel exiting the right ventricle that divides to form the right and left pulmonary arteries

Answer 79

two sets of paired vessels, one pair on each side, that are formed from the small venules leading away from the pulmonary capillaries that flow into the left atrium

Answer 80

alternating expansion and recoil of an artery as blood moves through the vessel; an indicator of heart rate

Answer 81

difference between the systolic and diastolic pressures

Answer 82

reabsorption in the cardiovascular system, the movement of material from the interstitial fluid into the capillaries

Answer 83

any condition or parameter that slows or counteracts the flow of blood

Answer 84

subclavian artery right subclavian arises from the brachiocephalic artery, whereas the left subclavian artery arises from the aortic arch; gives rise to the internal thoracic, vertebral, and thyrocervical arteries; supplies blood to the arms, chest, shoulders, back, and central nervous system

Answer 85

located deep in the thoracic cavity; becomes the axillary vein as it enters the axillary region; drains the axillary and smaller local veins near the scapular region; leads to the brachiocephalic vein

Answer 86

superior vena cava large systemic vein; drains blood from most areas superior to the diaphragm; empties into the right atrium

Answer 87

systolic pressure larger number recorded when measuring arterial blood pressure; represents the maximum value following ventricular contraction

Answer 88

tunica externa (also, tunica adventitia) outermost layer or tunic of a vessel (except capillaries)

Answer 89

tunica intima (also, tunica interna) innermost lining or tunic of a vessel

Answer 90

tunica media middle layer or tunic of a vessel (except capillaries)

Answer 91

blood vessel that conducts blood toward the heart

Answer 92

volume of blood contained within systemic veins in the integument, bone marrow, and liver that can be returned to the heart for circulation, if needed

Answer 93

venule small vessel leading from the capillaries

Answer 94

atrioventricular (AV) node clump of myocardial cells located in the inferior portion of the right atrium within the atrioventricular septum; receives the impulse from the SA node, pauses, and then transmits it into specialized conducting cells within the interventricular septum

Answer 95

atrioventricular bundle (also, bundle of His) group of specialized myocardial conductile cells that transmit the impulse from the AV node through the interventricular septum; form the left and right atrioventricular bundle branches

Answer 96

atrioventricular bundle branches (also, left or right bundle branches) specialized myocardial conductile cells that arise from the bifurcation of the atrioventricular bundle and pass through the interventricular septum; lead to the Purkinje fibers and also to the right papillary muscle via the moderator band

Answer 97

atrioventricular septum cardiac septum located between the atria and ventricles; atrioventricular valves are located here

Answer 98

atrioventricular valves one-way valves located between the atria and ventricles; the valve on the right is called the tricuspid valve, and the one on the left is the mitral or bicuspid valve

Answer 99

atrium (plural = atria) upper or receiving chamber of the heart that pumps blood into the lower chambers just prior to their contraction; the right atrium receives blood from the systemic circuit that flows into the right ventricle; the left atrium receives blood from the pulmonary circuit that flows into the left ventricle

Answer 100

extension of an atrium visible on the superior surface of the heart

Answer 101

(also, mitral valve or left atrioventricular valve) valve located between the left atrium and ventricle; consists of two flaps of tissue

Answer 102

(also, atrioventricular bundle) group of specialized myocardial conductile cells that transmit the impulse from the AV node through the interventricular septum; form the left and right atrioventricular bundle branches

Answer 103

cardiac cycle period of time between the onset of atrial contraction (atrial systole) and ventricular relaxation (ventricular diastole)

Answer 104

cardiac notch depression in the medial surface of the inferior lobe of the left lung where the apex of the heart is located

Answer 105

paired complex network of nerve fibers near the base of the heart that receive sympathetic and parasympathetic stimulations to regulate HR

Answer 106

series of autonomic reflexes that enable the cardiovascular centers to regulate heart function based upon sensory information from a variety of visceral sensors

Answer 107

chordae tendineae string-like extensions of tough connective tissue that extend from the flaps of the atrioventricular valves to the papillary muscles

Answer 108

branches of the ascending aorta that supply blood to the heart; the left coronary artery feeds the left side of the heart, the left atrium and ventricle, and the interventricular septum; the right coronary artery feeds the right atrium, portions of both ventricles, and the heart conduction system

Answer 109

coronary sinus large, thin-walled vein on the posterior surface of the heart that lies within the atrioventricular sulcus and drains the heart myocardium directly into the right atrium

Answer 110

coronary veins vessels that drain the heart and generally parallel the large surface arteries

Answer 111

period of time when the heart muscle is relaxed and the chambers fill with blood

Answer 112

electrocardiogram (ECG) surface recording of the electrical activity of the heart that can be used for diagnosis of irregular heart function; also abbreviated as EKG

Answer 113

innermost layer of the heart lining the heart chambers and heart valves; composed of endothelium reinforced with a thin layer of connective tissue that binds to the myocardium

Answer 114

innermost layer of the serous pericardium and the outermost layer of the heart wall

Answer 115

duration of ventricular diastole during which filling occurs

Answer 116

sounds heard via auscultation with a stethoscope of the closing of the atrioventricular valves (“lub”) and semilunar valves (“dub”)

Answer 117

inferior vena cava large systemic vein that returns blood to the heart from the inferior portion of the body

Answer 118

physical junction between adjacent cardiac muscle cells; consisting of desmosomes, specialized linking proteoglycans, and gap junctions that allow passage of ions between the two cells

Answer 119

left atrioventricular valve (also, mitral valve or bicuspid valve) valve located between the left atrium and ventricle; consists of two flaps of tissue

Answer 120

myocardium thickest layer of the heart composed of cardiac muscle cells built upon a framework of primarily collagenous fibers and blood vessels that supply it and the nervous fibers that help to regulate it

Answer 121

component of the electrocardiogram that represents the depolarization of the atria

Answer 122

cluster of specialized myocardial cells known as the SA node that initiates the sinus rhythm

Answer 123

extension of the myocardium in the ventricles to which the chordae tendineae attach

Answer 124

pericardial cavity cavity surrounding the heart filled with a lubricating serous fluid that reduces friction as the heart contracts

Answer 125

also, pericardium) membrane that separates the heart from other mediastinal structures; consists of two distinct, fused sublayers: the fibrous pericardium and the parietal pericardium

Answer 126

also, pericardial sac) membrane that separates the heart from other mediastinal structures; consists of two distinct, fused sublayers: the fibrous pericardium and the parietal pericardium

Answer 127

(also, spontaneous depolarization) mechanism that accounts for the autorhythmic property of cardiac muscle; the membrane potential increases as sodium ions diffuse through the always- open sodium ion channels and causes the electrical potential to rise

Answer 128

pulmonary arteries left and right branches of the pulmonary trunk that carry deoxygenated blood from the heart to each of the lungs

Answer 129

capillaries surrounding the alveoli of the lungs where gas exchange occurs: carbon dioxide exits the blood and oxygen enters

Answer 130

blood flow to and from the lungs

Answer 131

also, pulmonary semilunar valve, the pulmonic valve, or the right semilunar valve) valve at the base of the pulmonary trunk that prevents backflow of blood into the right ventricle; consists of three flaps

Answer 132

pulmonary veins veins that carry highly oxygenated blood into the left atrium, which pumps the blood into the left ventricle, which in turn pumps oxygenated blood into the aorta and to the many branches of the systemic circuit

Answer 133

specialized myocardial conduction fibers that arise from the bundle branches and spread the impulse to the myocardial contraction fibers of the ventricles

Answer 134

component of the electrocardiogram that represents the depolarization of the ventricles and includes, as a component, the repolarization of the atria

Answer 135

right atrioventricular valve (also, tricuspid valve) valve located between the right atrium and ventricle; consists of three flaps of tissue

Answer 136

semilunar valves valves located at the base of the pulmonary trunk and at the base of the aorta

Answer 137

plural = septa) walls or partitions that divide the heart into chambers

Answer 138

sinoatrial (SA) node known as the pacemaker, a specialized clump of myocardial conducting cells located in the superior portion of the right atrium that has the highest inherent rate of depolarization that then spreads throughout the heart

Answer 139

sinus rhythm normal contractile pattern of the heart

Answer 140

spontaneous depolarization (also, prepotential depolarization) the mechanism that accounts for the autorhythmic property of cardiac muscle; the membrane potential increases as sodium ions diffuse through the always-open sodium ion channels and causes the electrical potential to rise

Answer 141

(plural = sulci) fat-filled groove visible on the surface of the heart; coronary vessels are also located in these areas

Answer 142

blood flow to and from virtually all of the tissues of the body

Answer 143

period of time when the heart muscle is contracting

Answer 144

component of the electrocardiogram that represents the repolarization of the ventricles

Answer 145

term used most often in clinical settings for the right atrioventricular valve

Answer 146

in the cardiovascular system, a specialized structure located within the heart or vessels that ensures one-way flow of blood

Answer 147

one of the primary pumping chambers of the heart located in the lower portion of the heart; the left ventricle is the major pumping chamber on the lower left side of the heart that ejects blood into the systemic circuit via the aorta and receives blood from the left atrium; the right ventricle is the major pumping chamber on the lower right side of the heart that ejects blood into the pulmonary circuit via the pulmonary trunk and receives blood from the right atrium

Answer 148

Action potential: change in voltage of a cell membrane in response to a stimulus that results in transmission of electrical signal

Answer 149

the tubes of the circulatory system that close blood within it

Answer 150

substance in blood vessels that is used for transport of gasses, hormones, pathogens, and antibodies. Components (most to least) are: plasma (water, proteins, nutrients, hormones, etc…), hematocrit (RBC), and buffy coat (WBC and platelets)

Answer 151

hormone secreted by the thyroid gland to regulate calcium levels in the body through bone and kidney

Answer 152

Vitamin D3, produced by the small intestines during calcium deficiency

Answer 153

Erythrocytes: RBC, contains hemoglobin that carry gasses

Answer 154

Hematocrit: volume of the blood that consists of only RBC

Answer 155

Hemoglobin: the protein on RBC’s that oxygen binds to for transportation. The oxygen bind to its 4 heme sites that contain iron, the iron is what oxygen attaches to

Answer 156

chemical messenger/signal transported by the bloodstream for long distance signaling and bind to receptors on target cells. Slow signalling

Answer 157

Leukocytes: WBC, mainly released during pathogen introduction

Answer 158

small, bean shaped organ of the lymphatic system secondary lymphatic organ that works to remove debris and pathogens from the lymph. A site of adaptive immune responses

Answer 159

the tubes of the lymphatic system where interstitial fluid enters the lymphatic system to become lymph. Include lymphatic trunks and lymphatic ducts

Answer 160

interstitial fluid after it enters the lymphatic system – the fluid of the lymphatic system

Answer 161

WBC’s (B-cells, T-cells, plasma cells, and natural killer cells) used in the adaptive immune response to fight against pathogens

Answer 162

body’s first line defence against viruses and some cancers. Contain cytoxic granules in its cytoplasm

Answer 163

signaling chemical released by nerve terminals that bind to and activate receptors on target cells

Answer 164

Osteoblasts: bone builders, responsible for creating osseous tissue

Answer 165

Osteoclasts: bone breakers, responsible for releasing calcium into the bloodstream

Answer 166

Parathyroid gland: 4 part small gland a part of the endocrine system that regular calcium in our bodies

Answer 167

Parathyroid hormone: hormone secreted by the parathyroid glands to regulate calcium levels in the body through the bone, kidney, and intestine

Answer 168

synthesized in the liver, consist of (most to least) albumin, globulins, and fibrinogen. Their main function is for transportation, maintaining osmotic concentration, and blood clotting

Answer 169

Largest component of the blood, made of water, proteins, nutrients, hormones, pathogens, and more. Everything in the blood other than blood cells

Answer 170

: tiny blood cells that bunch up together to form clots and stop bleeding. Signals are sent to the platelets during injury to a blood vessel

Answer 171

Signalling mechanism: way in which a signal in the body is sent. Can be electrical (action potential) or chemical (neurotransmitter or hormone

Answer 172

Thyroid gland: butter-fly shaped organ that releases hormones to control metabolism

Answer 173

Cardiac output Any factor that causes cardiac output to increase, by elevating heart rate or stroke volume or both, will elevate blood pressure and promote blood flow. These factors include sympathetic stimulation, the catecholamines epinephrine and norepinephrine, thyroid hormones, and increased calcium ion levels. Compliance The greater the compliance of an artery, the more effectively it is able to expand to accommodate surges in blood flow without increased resistance or blood pressure. Veins are more compliant than arteries and can expand to hold more blood. Volume of the blood blood volume decreases, pressure and flow decreases Viscosity of the blood viscosity to increase will also increase resistance and decrease flow. Blood vessel length and diameter The length of a vessel is directly proportional to its resistance: the longer the vessel, the greater the resistance and the lower the flow. As with blood volume, this makes intuitive sense, since the increased surface area of the vessel will impede the flow of blood. Likewise, if the vessel is shortened, the resistance will decrease and flow will increase. Recall that blood moves from higher pressure to lower pressure. It is pumped from the heart into the arteries at high pressure. If you increase pressure in the arteries (afterload), and cardiac function does not compensate, blood flow will actually decrease. In the venous system, the opposite relationship is true. Increased pressure in the veins does not decrease flow as it does in arteries, but actually increases flow. Since pressure in the veins is normally relatively low, for blood to flow back into the heart, the pressure in the atria during atrial diastole must be even lower. It normally approaches zero, except when the atria contrac Only one of these factors, the radius, can be changed rapidly by vasoconstriction and vasodilation, thus dramatically impacting resistance and flow. Further, small changes in the radius will greatly affect flow, since it is raised to the fourth power in the equation.

Answer 174

arterioles as resistance vessels, because given their small lumen, they dramatically slow the flow of blood from arteries. In fact, arterioles are the site of greatest resistance in the entire vascular network. the total cross-sectional area of the body’s capillary beds is far greater than any other type of vessel. Although the diameter of an individual capillary is significantly smaller than the diameter of an arteriole, there are vastly more capillaries in the body than there are other types of blood vessels. Part (c) shows that blood pressure drops unevenly as blood travels from arteries to arterioles, capillaries, venules, and veins, and encounters greater resistance. However, the site of the most precipitous drop, and the site of greatest resistance, is the arterioles. This explains why vasodilation and vasoconstriction of arterioles play more significant roles in regulating blood pressure than do the vasodilation and vasoconstriction of other vessels.

Answer 175

Arteries General appearance Thick walls with small lumens Generally appear rounded Tunica intima Endothelium usually appears wavy due to constriction of smooth muscle Internal elastic membrane present in larger vessels Tunica media Normally the thickest layer in arteries Smooth muscle cells and elastic fibers predominate the proportions of these vary with distance from the heart) External elastic membrane present in larger vessels Tunica externa Normally thinner than the tunica media in all but the largest arteries Collagenous and elastic fibers Nervi vasorum and vasa vasorum present Arteries Conducts blood away from the heart Rounded High Thick Higher in systemic arteries Lower in pulmonary arteries Not present Veins Thin walls with large lumens Generally appear flattened Endothelium appears smooth Internal elastic membrane absent Normally thinner than the tunica externa Smooth muscle cells and collagenous fibers predominate Nervi vasorum and vasa vasorum present External elastic membrane absent Normally the thickest layer in veins Collagenous and smooth fibers predominate Some smooth muscle fibers Nervi vasorum and vasa vasorum present Conducts blood toward the heart Irregular, often collapsed Low Thin Lower in systemic veins Higher in pulmonary veins Present most commonly in limbs and in veins inferior to the heart

Answer 176

The cardioaccelerator centers stimulate cardiac function by regulating heart rate and stroke volume via sympathetic stimulation from the cardiac accelerator nerve. The cardioinhibitor centers slow cardiac function by decreasing heart rate and stroke volume via parasympathetic stimulation from the vagus nerve. The vasomotor centers control vessel tone or contraction of the smooth muscle in the tunica media. Changes in diameter affect peripheral resistance, pressure, and flow, which affect cardiac output. The majority of these neurons act via the release of the neurotransmitter norepinephrine from sympathetic neurons.

Answer 177

Baroreceptors are specialized stretch receptors located within thin areas of blood vessels and heart chambers that respond to the degree of stretch caused by the presence of blood. They send impulses to the cardiovascular center to regulate blood pressure. When blood pressure rises too high, the baroreceptors fire at a higher rate and trigger parasympathetic stimulation of the heart. As a result, cardiac output falls. Sympathetic stimulation of the peripheral arterioles will also decrease, resulting in vasodilation. Combined, these activities cause blood pressure to fall. When blood pressure drops too low, the rate of baroreceptor firing decreases. This will trigger an increase in sympathetic stimulation of the heart, causing cardiac output to increase. It will also trigger sympathetic stimulation of the peripheral vessels, resulting in vasoconstriction. Combined, these activities cause blood pressure to rise.

Answer 178

In addition to the baroreceptors are chemoreceptors that monitor levels of oxygen, carbon dioxide, and hydrogen ions (pH), and thereby contribute to vascular homeostasis. Chemoreceptors monitoring the blood are located in close proximity to the baroreceptors in the aortic and carotid sinuses. They signal the cardiovascular center as well as the respiratory centers in the medulla oblongata. The chemoreceptors respond to increasing carbon dioxide and hydrogen ion levels (falling pH) by stimulating the cardioaccelerator and vasomotor centers, increasing cardiac output and constricting peripheral vessels. The cardioinhibitor centers are suppressed. With falling carbon dioxide and hydrogen ion levels (increasing pH), the cardioinhibitor centers are stimulated, and the cardioaccelerator and vasomotor centers are suppressed, decreasing cardiac output and causing peripheral vasodilation. In order to maintain adequate supplies of oxygen to the cells and remove waste products such as carbon dioxide, it is essential that the respiratory system respond to changing metabolic demands. In turn, the cardiovascular system will transport these gases to the lungs for exchange, again in accordance with metabolic demands.

Answer 179

The catecholamines epinephrine and norepinephrine are released by the adrenal medulla, and enhance and extend the body’s sympathetic or “fight-or-flight” response They increase heart rate and force of contraction, while temporarily constricting blood vessels to organs not essential for flight-or-fight responses and redirecting blood flow to the liver, muscles, and heart. Antidiuretic hormone (ADH), also known as vasopressin, is secreted by the cells in the hypothalamus and transported via the hypothalamic-hypophyseal tracts to the posterior pituitary where it is stored until released upon nervous stimulation. The primary trigger prompting the hypothalamus to release ADH is increasing osmolarity of tissue fluid, usually in response to significant loss of blood volume. ADH signals its target cells in the kidneys to reabsorb more water, thus preventing the loss of additional fluid in the urine. This will increase overall fluid levels and help restore blood volume and pressure. In addition, ADH constricts peripheral vessels. The renin-angiotensin-aldosterone mechanism has a major effect upon the cardiovascular system (Figure 20.19). Renin is an enzyme, although because of its importance in the renin-angiotensin-aldosterone pathway, some sources identify it as a hormone. Specialized cells in the kidneys , called juxtaglomerular (JG) cells, respond to decreased blood pressure by secreting renin into the blood. Renin converts the plasma protein angiotensinogen, which is produced by the liver, into its active form—angiotensin I. Angiotensin I circulates in the blood and is then converted into angiotensin II in the lungs. This reaction is catalyzed by the enzyme angiotensin-converting enzyme (ACE). Angiotensin II is a powerful vasoconstrictor, greatly increasing blood pressure. Erythropoietin (EPO) is released by the kidneys when blood flow and/or oxygen levels decrease. EPO stimulates the production of erythrocytes within the bone marrow. Erythrocytes are the major formed element of the blood and may contribute 40 percent or more to blood volume, a significant factor of viscosity, resistance, pressure, and flow. In addition, EPO is a vasoconstrictor. Overproduction of EPO or excessive intake of synthetic EPO, often to enhance athletic performance, will increase viscosity, resistance, and pressure, and decrease flow in addition to its contribution as a vasoconstrictor. Secreted by cells in the atria of the heart, atrial natriuretic hormone (ANH) (also known as atrial natriuretic peptide) is secreted when blood volume is high enough to cause extreme stretching of the cardiac cells. Cells in the ventricle produce a hormone with similar effects, called B-type natriuretic hormone. Natriuretic hormones are antagonists to angiotensin II. They promote loss of sodium and water from the kidneys, and suppress renin, aldosterone, and ADH production and release. All of these actions promote loss of fluid from the body, so blood volume and blood pressure drop.

Answer 180

neither specialized nervous stimulation nor endocrine control. Rather, these are local, self-regulatory mechanisms that allow each region of tissue to adjust its blood flow—and thus its perfusion. These local mechanisms include chemical signals and myogenic controls. Chemical signals work at the level of the precapillary sphincters to trigger either constriction or relaxation. As you know, opening a precapillary sphincter allows blood to flow into that particular capillary, whereas constricting a precapillary sphincter temporarily shuts off blood flow to that region. The factors involved in regulating the precapillary sphincters include the following: Opening of the sphincter is triggered in response to decreased oxygen concentrations; increased carbon dioxide concentrations; increasing levels of lactic acid or other byproducts of cellular metabolism; increasing concentrations of potassium ions or hydrogen ions (falling pH); inflammatory chemicals such as histamines; and increased body temperature. These conditions in turn stimulate the release of NO, a powerful vasodilator, from endothelial cells (see Figure 20.17). Contraction of the precapillary sphincter is triggered by the opposite levels of the regulators, which prompt the release of endothelins, powerful vasoconstricting peptides secreted by endothelial cells. Platelet secretions and certain prostaglandins may also trigger constriction.

Answer 181

For a healthy young adult, cardiac output (heart rate × stroke volume) increases in the nonathlete from approximately 5.0 liters (5.25 quarts) per minute to a maximum of about 20 liters (21 quarts) per minute. Accompanying this will be an increase in blood pressure from about 120/80 to 185/75. However, well-trained aerobic athletes can increase these values substantially. For these individuals, cardiac output soars from approximately 5.3 liters (5.57 quarts) per minute resting to more than 30 liters (31.5 quarts) per minute during maximal exercise. Along with this increase in cardiac output, blood pressure increases from 120/80 at rest to 200/90 at maximum values. In addition to improved cardiac function, exercise increases the size and mass of the heart. The average weight of the heart for the nonathlete is about 300 g, whereas in an athlete it will increase to 500 g. This increase in size generally makes the heart stronger and more efficient at pumping blood, increasing both stroke volume and cardiac output. Tissue perfusion also increases as the body transitions from a resting state to light exercise and eventually to heavy exercise result in selective vasodilation in the skeletal muscles, heart, lungs, liver, and integument. Simultaneously, vasoconstriction occurs in the vessels leading to the kidneys and most of the digestive and reproductive organs. The flow of blood to the brain remains largely unchanged whether at rest or exercising, since the vessels in the brain largely do not respond to regulatory stimuli, in most cases, because they lack the appropriate receptors. As vasodilation occurs in selected vessels, resistance drops and more blood rushes into the organs they supply. This blood eventually returns to the venous system. Venous return is further enhanced by both the skeletal muscle and respiratory pumps. As blood returns to the heart more quickly, preload rises and the Frank-Starling principle tells us that contraction of the cardiac muscle in the atria and ventricles will be more forceful. Eventually, even the best-trained athletes will fatigue and must undergo a period of rest following exercise. Cardiac output and distribution of blood then return to normal.

Answer 182

The pericardium is made up of two serous membrane layers, each composed of an epithelial lining with an underlying connective tissue. The pericardium keeps the heart in place, limits its motion, prevents it from over expanding, whilst the pericardial fluid reduces the friction between it and its surrounding structures. Pericardial sac The heart wall is made up of three layers, the endocardium, myocardium, and epicardium: Endocardium A smooth, thin membrane that lines the inner surface of the heart chambers, the endocardium is composed of a thin layer of endothelial cells, which lies over a thin layer of connective tissue. This innermost layer also covers the valves of the heart, and helps to prevent resistance as blood passes through the vessels and chambers of the heart. Myocardium The myocardium - the heart muscle itself, varies in thickness depending on its location, being thin in the atria and thick in the ventricles. It is composed of cardiac muscle fibers, which exhibit striations diagonally across the heart. Epicardium The epicardium is the thin, outer serous membrane of the heart wall, which is also described as the inner-most layer of the serous pericardium, known as the visceral pericardium. It is composed mainly of connective tissue mesothelial cells, which gives a smooth texture on the outer surface of the heart.

Answer 183

Initially, physiological conditions that cause HR to increase also trigger an increase in SV. During exercise, the rate of blood returning to the heart increases. However as the HR rises, there is less time spent in diastole and consequently less time for the ventricles to fill with blood. Even though there is less filling time, SV will initially remain high. However, as HR continues to increase, SV gradually decreases due to decreased filling time. CO will initially stabilize as the increasing HR compensates for the decreasing SV, but at very high rates, CO will eventually decrease as increasing rates are no longer able to compensate for the decreasing SV.

Answer 184

The cardiovascular center receives input from a series of visceral receptors with impulses traveling through visceral sensory fibers within the vagus and sympathetic nerves via the cardiac plexus. Among these receptors are various proprioreceptors, baroreceptors, and chemoreceptors, plus stimuli from the limbic system. Collectively, these inputs normally enable the cardiovascular centers to regulate heart function precisely, a process known as cardiac reflexes. Increased physical activity results in increased rates of firing by various proprioreceptors located in muscles, joint capsules, and tendons. Any such increase in physical activity would logically warrant increased blood flow. The cardiac centers monitor these increased rates of firing, and suppress parasympathetic stimulation and increase sympathetic stimulation as needed in order to increase blood flow. Similarly, baroreceptors are stretch receptors located in the aortic sinus, carotid bodies, the venae cavae, and other locations, including pulmonary vessels and the right side of the heart itself. Rates of firing from the baroreceptors represent blood pressure, level of physical activity, and the relative distribution of blood. The cardiac centers monitor baroreceptor firing to maintain cardiac homeostasis, a mechanism called the baroreceptor reflex. With increased pressure and stretch, the rate of baroreceptor firing increases, and the cardiac centers decrease sympathetic stimulation and increase parasympathetic stimulation. As pressure and stretch decrease, the rate of baroreceptor firing decreases, and the cardiac centers increase sympathetic stimulation and decrease parasympathetic stimulation Parasympathetic stimulation originates from the cardioinhibitory region with impulses traveling via the vagus nerve (cranial nerve X). The vagus nerve sends branches to both the SA and AV nodes, and to portions of both the atria and ventricles. Parasympathetic stimulation releases the neurotransmitter acetylcholine (ACh) at the neuromuscular junction. ACh slows HR by opening chemical- or ligand-gated potassium ion channels to slow the rate of spontaneous depolarization, which extends repolarization and increases the time before the next spontaneous depolarization occurs.

Answer 185

At the beginning of the cardiac cycle, both the atria and ventricles are relaxed (diastole). Blood is flowing into the right atrium from the superior and inferior venae cavae and the coronary sinus. Blood flows into the left atrium from the four pulmonary veins. The two atrioventricular valves, the tricuspid and mitral valves, are both open, so blood flows unimpeded from the atria and into the ventricles. Approximately 70–80 percent of ventricular filling occurs by this method. The two semilunar valves, the pulmonary and aortic valves, are closed, preventing backflow of blood into the right and left ventricles from the pulmonary trunk on the right and the aorta on the left. Atrial Systole and Diastole Contraction of the atria follows depolarization, represented by the P wave of the ECG. As the atrial muscles contract from the superior portion of the atria toward the atrioventricular septum, pressure rises within the atria and blood is pumped into the ventricles through the open atrioventricular (tricuspid, and mitral or bicuspid) valves. At the start of atrial systole, the ventricles are normally filled with approximately 70–80 percent of their capacity due to inflow during diastole Ventricular systole (see Figure 19.27) follows the depolarization of the ventricles and is represented by the QRS complex in the ECG. It may be conveniently divided into two phases, lasting a total of 270 ms. At the end of atrial systole and just prior to ventricular contraction, the ventricles contain approximately 130 mL blood in a resting adult in a standing position. This volume is known as the end diastolic volume (EDV) or preload. Initially, as the muscles in the ventricle contract, the pressure of the blood within the chamber rises, but it is not yet high enough to open the semilunar (pulmonary and aortic) valves and be ejected from the heart. However, blood pressure quickly rises above that of the atria that are now relaxed and in diastole. This increase in pressure causes blood to flow back toward the atria, closing the tricuspid and mitral valves. Since blood is not being ejected from the ventricles at this early stage, the volume of blood within the chamber remains constant. Consequently, this initial phase of ventricular systole is known as isovolumic contraction, also called isovolumetric contraction (see Figure 19.27). In the second phase of ventricular systole, the ventricular ejection phase, the contraction of the ventricular muscle has raised the pressure within the ventricle to the point that it is greater than the pressures in the pulmonary trunk and the aorta. Blood is pumped from the heart, pushing open the pulmonary and aortic semilunar valves. Pressure generated by the left ventricle will be appreciably greater than the pressure generated by the right ventricle, since the existing pressure in the aorta will be so much higher. Nevertheless, both ventricles pump the same amount of blood. This quantity is referred to as stroke volume. Stroke volume will normally be in the range of 70–80 mL. Since ventricular systole began with an EDV of approximately 130 mL of blood, this means that there is still 50–60 mL of blood remaining in the ventricle following contraction. This volume of blood is known as the end systolic volume (ESV). Ventricular Diastole Ventricular relaxation, or diastole, follows repolarization of the ventricles and is represented by the T wave of the ECG. It too is divided into two distinct phases and lasts approximately 430 ms. During the early phase of ventricular diastole, as the ventricular muscle relaxes, pressure on the remaining blood within the ventricle begins to fall. When pressure within the ventricles drops below pressure in both the pulmonary trunk and aorta, blood flows back toward the heart, producing the dicrotic notch (small dip) seen in blood pressure tracings. The semilunar valves close to prevent backflow into the heart. Since the atrioventricular valves remain closed at this point, there is no change in the volume of blood in the ventricle, so the early phase of ventricular diastole is called the isovolumic ventricular relaxation phase, also called isovolumetric ventricular relaxation phase (see Figure 19.27). In the second phase of ventricular diastole, called late ventricular diastole, as the ventricular muscle relaxes, pressure on the blood within the ventricles drops even further. Eventually, it drops below the pressure in the atria. When this occurs, blood flows from the atria into the ventricles, pushing open the tricuspid and mitral valves. As pressure drops within the ventricles, blood flows from the major veins into the relaxed atria and from there into the ventricles. Both chambers are in diastole, the atrioventricular valves are open, and the semilunar valves remain closed (see Figure 19.27). The cardiac cycle is complete.

Answer 186

When there is venous constriction in the veins, it typically leads to an increase in preload. Preload refers to the volume of blood in the ventricles at the end of diastole, just before the heart contracts. Venous constriction results in increased venous return to the heart, as it enhances the force driving blood from the veins back into the heart. This increased venous return leads to an increase in the volume of blood in the ventricles during diastole, thus increasing preload. In summary, venous constriction increases venous return, which increases preload by increasing the volume of blood in the ventricles before contraction. This, in turn, can lead to an increase in stroke volume and cardiac output.

Answer 187

Increasing EDV increases the sarcomeres' lengths within the cardiac muscle cells, allowing more cross bridge formation between the myosin and actin and providing for a more powerful contraction.

Answer 188

Arterioles are also called resistance vessels due to their ability to increase vascular resistance, which is a significant determinant of blood pressure.

Answer 189

False. The plasma proteins suspended in blood cannot cross the semipermeable capillary cell membrane, and so they remain in the plasma within the vessel, where they account for the blood colloid osmotic pressure.

Answer 190

The brain receives blood from two sources: the internal carotid arteries, which arise at the point in the neck where the common carotid arteries bifurcate, and the vertebral arteries (Figure 1.20). The internal carotid arteries branch to form two major cerebral arteries, the anterior and middle cerebral arteries.

Answer 191

This plateau phase allows for a longer muscle contraction and gives time for the nearby cardiac muscle cells to depolarize. This is important in allowing the heart to contract in a steady, uniform and forceful manner. Following the plateau phase is phase 3, also known as the repolarization phase.

Answer 192

The recommended 3-wire ECG lead placement is as follows. Place RA (white) electrode under right clavicle, mid-clavicular line within the rib cage frame. Place LA (black) electrode under left clavicle, mid-clavicular line within the rib cage frame.

Answer 193

both cases, as the valves close, the openings within the atrioventricular septum guarded by the valves will become reduced, and blood flow through the opening will become more turbulent until the valves are fully closed. There is a third heart sound, S3, but it is rarely heard in healthy individuals. It may be the sound of blood flowing into the atria, or blood sloshing back and forth in the ventricle, or even tensing of the chordae tendineae. S3 may be heard in youth, some athletes, and pregnant women. If the sound is heard later in life, it may indicate congestive heart failure, warranting further tests. Some cardiologists refer to the collective S1, S2, and S3 sounds as the “Kentucky gallop,” because they mimic those produced by a galloping horse. The fourth heart sound, S4, results from the contraction of the atria pushing blood into a stiff or hypertrophic ventricle, indicating failure of the left ventricle. S4 occurs prior to S1 and the collective sounds S4, S1, and S2 are referred to by some cardiologists as the “Tennessee gallop,” because of their similarity to the sound produced by a galloping horse with a different gait. A few individuals may have both S3 and S4, and this combined sound is referred to as S7.