Chapter 11 The Cardiovascular System
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Transcript of Chapter 11 The Cardiovascular System
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Chapter 11 The Cardiovascular System
Biology 112Tri-County Technical College
Pendleton, SC
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Functions of CV System Major function is transportation Using blood as transport vehicle, system
carries oxygen, nutrients, cell wastes, hormones, and many other substances vital to homeostasis to and from cells
The force to move blood around the body provided by beating heart
Heart located in body thorax flanked by lungs
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Have a heart… More pointed apex pointed toward
left hip & rests on diaphragm Broader posterosuperior aspect, or
base from which great vessels of body merge, points toward right shoulder and lies beneath the second rib
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Location of Heart, Visual
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Coverings of the Heart Enclosed by double sac of serous membane
(pericardium) Thin visceral pericardium (epicardium)
hugs external surface of heart and is part of heart wall
Epicardium continuous at heart base with loosely applied parietal pericardium
Serous fluid (slippery lubricating) produced by serous pericardial membranes
Allows heart to beat almost frictionless environment as pericardial layers slide across each other
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Walls of the Heart Epicardium, Myocardium, Endocardium Epicardium is thin visceral pericardium Myocardium (middle layer) is composed of
thick bundles of cardiac muscle twisted & whorled into ringlike arrangement Myocardium that actually CONTRACTS
Endocardium (innermost) is thin, glistening sheet of endothelium that lines chambers Continuous with lining of blood vessels entering
and leaving heart
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Heart Chambers Four hollow chambers or cavities Two atria and two ventricles—all lined with
endocardium Superior atria primarily receiving chambers Inferior, thick-walled ventricles discharging
chambers (actual pumps of heart Septum dividing heart longitudinally referred
to as interatrical and interventricular septum
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Gross Anatomy of Heart
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Great Vessels of the Heart Superior and inferior vena cavaright
atria Right ventriclepulmonary truckright
and left pulmonary arterieslungs O2 rich blood from lungs to heart4
pulmonary veins (pulmonary circuit)left atrialeft ventricleaortasystemic arteriesbody tissues (systemic circuit)
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Circulation Visual
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Heart Valves Four valves whose general function is to
prevent backflow of blood Atrioventricular (AV) valves between atrial
and ventricular chambers on each side Left AV valve (bicuspid/mitral) has 2 cusps
(flaps) & prevents backflow into left artium Right AV valve (bicuspid) has 3 cusps &
prevents backflow into right atrium Pulmonary semilunar valve—right
ventricle Aortic semilunar valve—left ventricle
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Heart Valves Visual
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Blood Flow From body into right atrium via vena
cava Right atriumright ventricle via tricuspid Right ventriclelungs via pulmonary
semilunar valve and pulmonary arteries Lungsleft atrium via pulmonary veins Left atriumleft ventricle via bicuspid Left ventriclebody via aortic semilunar
valve and aorta
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Cardiac Circulation Blood in heart does NOT nourish myocardium Right and left coronary arteries responsible Branch from base of aorta, encircle heart in
atrioventricular groove Anterior interventricular & circumflex arteries
on left and posterior interventricular and marginal arteries on right compressed when ventricles contracting and fill when ventricle relax
Myocardium drained by several cardiac veins Empty into coronary sinus (enlarged vessel on
backside of heart Coronary sinus empties into right atrim
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Some Key Terms Pericarditis-inflammation of pericardium often
from decrease in amount of serious fluid Pericardial layers bind and stick to each other Forms painful adhesions interfering with heart
movements Valvular Stenosis-valve flaps become stiff
(repeated bacterial infection of endocardium) Forces heart to beat more vigorously than normal Workload increases, heart weakens, and may fail
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Key Terms, cont. Myocardial infarction (heart attack
or coronary)-myocardial cells NOT receiving adequate blood supply
Ischemic heart cells begin to die
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Impulse Conduction 2 types of controlling systems regulate Nerves of ANS and intrinsic
conduction system (nodal system) ANS acts like “brakes” or “accelerator”
depending on which division is activated Intrinsic system composed of special
tissue found no where else in body Cross between nervous & muscle tissue Causes depolarization in only ONE direction-
from atria to ventricles
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Impulse, cont. Nodal system composed of sinoatrial (SA)
node (right atrium); atrioventricular (AV) node(junction of atria & ventricles); AV bundles (bundle of His); Right and Left bundle branches (interventricular septum); and Purkinje fibers (within muscle of ventricular wall)
SA (Pacemaker) fires Impulse spreads through atria to AV node
Atria contract
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Impulse, III
AV node delays impulse preventing simultaneous atria/ventricle contraction allows complete emptying of atria
Impulse conducted to AV bundle, bundle branches, and Purkinje fibers Ventricles contract
Heart beats to internal rhythm but body can speed it up or slow it down
Vagus nerve <; Sympathetic fibers >
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Impulse Conduction, Visual
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Heart Block UNC, depolarization waves reach
ventricles only through AV node Damage to AV node can
partially/totally release ventricles from control of SA node
Ventricles begin to beat at their own rate (which is much slower) some or all the time
This condition is called heart block
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Three Key Terms Ischemia is lack of adequate blood supply to
heart muscle May lead to fibrillation (rapid, uncoordinated
shuddering of hear muscle) which makes heart useless as pump and major cause of death from heart attacks
Often followed by arrest Bradycardia is heart rate substantially slower
than normal (less than 60 beats per minute) Tachycardia is rapid heartbeat (over 100
beats per minute) May progress to fibrillation
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Cardiac Cycle Refers to events of ONE heartbeat Average is 75 beats per minute so
cycle normally about 0.8 seconds Systole means heart contraction Diastole means heart relaxation Atria are in systole at same time
and ventricles are in systole at the same time
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Cardiac Cycle, Visual
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Heart Sounds Lub-Dup First sound (lub) = closing of AV valves Second sound (dup) caused by closing of
semilunar valves at end of systole Lub sound longer and louder; Dup tends to
be short and sharp Abnormal/unusual sounds called murmurs
Caused by turbulance of blood flow Fairly common in children/elderly people
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Sounds, cont. Murmurs may indicate valve problem If valve does NOT close tightly
(incompetent), swishing will be heard as blood flows back through partially “open” valve
Distinct sounds also heard when blood flows turbulently through “stenosed” (narrowed) valves
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Cardiac Output CO is amount of blood pumped out
by each side of heart Actually each ventricle in ONE minute
Stroke volume is volume of blood pumped out by each ventricle with each heartbeat SV >s as force of ventricular
contraction >s CO is PRODUCT of heart rate (HR)
x stroke volume (SV); CO=HR x SV
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Output, cont. 75 beats/min x stroke volume of 70
ml/beat equals 5250 ml/min Normal blood volume = ~5000 ml, entire
blood supply passes through heart once each minute
SV regulated by many factors > volume or speed of venous return >s SV &
force of contraction < volume or speed of venous return <s SV &
force of contraction
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Output, cont. “Starlings law of the heart: more heart
muscle is stretched, the stronger contraction
Critical factor “stretching” heart muscle is venous return
Insures volume of blood going out equals volume of blood coming in (vice-versa)
REGULATION of heart rate dependent of many factors
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Output and Regulation, cont.
Heart rate can be changed temporarily by autonomic nerves
Sympathetic nerves stimulate SA and AV nodes and heart muscle itself to > rate
Parasympathetic nerves (vagus) slow and steady heart giving rest time during noncrisis
Epinephrine and thyroxine >s heart rate
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Output & Regulation, cont. Physical factors (age, gender, exercise,
and body temperature) influence heart rate
Hypocalcemia (reduced levels of ionic calcium) depress the heart
Hypercalcemia (> levels of ionic calcium) causes prolonged contraction to point heart may stop entirely
Hypokalemia (reduced levels of ionic potassium causes feeble heart beat and abnormal rhythms appear
heatheart rate and coldheart rate
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Congestive Heart Failure Pumping efficiency depressed so circulation
inadequate to meet tissue needs = congestive heart failure
One side can fail independently of the other Left side fails = Pulmonary congestion occurs
vessels in lungs swells-fluid leaks-pulmonary edema-if untreated, person suffocates
Right side fails = Peripheral congestion occurs blood backs up in systemic circulation-edema most
noticeable in distal body parts (swollen feet, ankles, fingers)
Failure of one side puts strain on other side & eventually whole heart fails
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Electrocardiogram (ECG) Impulses cause electrical currents to pass
through body Can be detected by electrocardiograph Three recognizable waves (P, QRS complex, & T) P wave first and small-depolarization of atria
before they contract QRS complex is large wave-depolarization of
ventricles; precedes their contraction T-wave results repolarization of ventricles Atrial repolarization normally hidden by QRS May reveal heart problems: abnormal waves;
changes in timing; fibrillation
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Arterial Pulse Expansion and recoil of artery occurring
with each ventricle beat creates PULSE Pulse rate = heart rate Averages 70-80 per minute Influenced by activity, postural changes,
emotions May be taken at any artery close to
surface Temporal, carotid, brachial, & radial most
common
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Blood Pressure Points, Visual
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Blood Pressure… Is pressure blood exerts against inner
walls of blood vessels Force that keeps blood circulating USD, understood to mean pressure
within large systemic arteries NEAR heart Pressure highest in large arteries and <s
thru pathway Reaches 0 or negative at vena cava Return dependent on valves in larger
veins, milking activity of skeletal muscles, and pressure changes in thorax
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Auscultatory Method for BP
Systemic arterial BP measured indirectly System uses brachial artery of arm Systolic pressure=pressure at peak of
ventricular contraction Diastolic pressure=pressure when
ventricles are relaxed “Normal” is 120/80 but range is 110-
140/75-80 Varies with age, weight, mood, race,
activity, and posture
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Blood Pressure, Visual
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BP Math…or whatever BP = cardiac output x peripheral
resistance Cardiac output increases, BP increases Peripheral resistance increases; BP
increases Cardiac output decreases; BP
decreases Peripheral resistance decreases; BP
decreases
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Factoring the factors Sympathetic division of ANS
causes vasoconstriction >ing peripheral resistance which >s BP
Parasympathetic division of ANS causes vasodilation <ing peripheral resistance which <s BP
Kidneys help regulate BP by altering blood volume Retain or excrete water Also produce RENIN
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Factors, cont. If BP low, kidney cells release enzyme
renin into blood Renin triggers cascade of reactions that
produce Angiotensin II which is potent vasoconstrictor
Vasoconstriction raises BP AT II stimulates adrenal cortex to
release Aldosterone (hormone that >s sodium ion reabsorption by kidneys
Water follows sodium ions thus blood volume and BP both rise
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Enough of factoring, already..
Epinephrine >s heart rate and BP Nicotine >s BP by causing vasoconstriction Alcohol/Histamine < BP by causing
vasodilation Diuretics cause kidneys to excrete more
water which reduces blood volume thereby lowering BP
TOO much salthypertonic blood which absorbs water from tissues increasing blood volume and BP
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The end of factoring…Yeah!!
TOO much fatsexcessive fats in blood
Makes blood more viscous and more difficult to pump
Peripheral resistance is increased which increases the blood pressure
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Hypotension Low BP = systolic < 100 mm Hg Physical conditioning and/or health Orthostatic hypotension = temporary drop
in BP resulting in dizziness upon rising May be slow reacting sympathetic NS and
blood pooling in lower limbs reducing BP and blood delivery to brain
Chronic hypotension may be result of inadequate blood proteins, low viscosity, and/or low pressure
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Hypertension Sustained elevated arterial pressure of
140/90 or higher Heart has to work against increased
resistance and has to work HARDER Myocardium enlarges; when strained
beyond capacity to respond, weakens and becomes flabby
Causes small tears in endothelium of blood vessels that > progress of artherosclerosis
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Hypertension, cont. Most cases (90%+) are primary or
essential which CANNOT be accounted for by any specific organic cause Diet, obesity, heredity, race, stress involved
Treatment for hypertension diuretics vasodilators/beta blockers ACE-inhibitors (inhibit renin) Cardiac inhibitors (calcium channel blockers) Lifestyle changes