Download Chapter 11 The Cardiovascular System

Chapter 11 The Cardiovascular
System
Biology 110
Tri-County Technical College
Pendleton, SC
Functions of CV System
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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
Have a heart…
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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
Location of Heart, Visual
Coverings of the Heart
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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
Walls of the Heart
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Epicardium, Myocardium, Endocardium
Epicardium is thin visceral pericardium
Myocardium (middle layer) is composed of
thick bundles of cardiac muscle twisted &
whorled into ringlike arrangement
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Myocardium that actually CONTRACTS
Endocardium (innermost) is thin, glistening
sheet of endothelium that lines chambers
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Continuous with lining of blood vessels entering
and leaving heart
Heart Chambers
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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
Gross Anatomy of Heart
Great Vessels of the Heart
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Superior and inferior vena cavaright atria
Right ventriclepulmonary truckright and
left pulmonary arterieslungs
O2 rich blood from lungs to heart4
pulmonary veins (pulmonary circuit)left
atrialeft ventricleaortasystemic
arteriesbody tissues (systemic circuit)
Circulation Visual
Heart Valves
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Four valves whose general function is to
prevent backflow of blood
Atrioventricular (AV) valves between atrial
and ventricular chambers on each side
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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
Heart Valves Visual
Blood Flow
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From body into right atrium via vena cava
Right atriumright ventricle via tricuspid
Right ventriclelungs via pulmonary
semilunar valve and pulmonary arteries
Lungsleft atrium via pulmonary veins
Left atriumleft ventricle via bicuspid
Left ventriclebody via aortic semilunar valve
and aorta
Cardiac Circulation
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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
Some Key Terms
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Pericarditis-inflammation of pericardium often
from decrease in amount of serious fluid
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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)
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Forces heart to beat more vigorously than normal
Workload increases, heart weakens, and may fail
Key Terms, cont.
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Myocardial infarction (heart attack or
coronary)-myocardial cells NOT
receiving adequate blood supply
Ischemic heart cells begin to die
Impulse Conduction
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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
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Cross between nervous & muscle tissue
Causes depolarization in only ONE direction-from
atria to ventricles
Impulse, cont.
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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
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Atria contract
Impulse, III
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AV node delays impulse preventing
simultaneous atria/ventricle contraction
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Impulse conducted to AV bundle, bundle
branches, and Purkinje fibers
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allows complete emptying of atria
Ventricles contract
Heart beats to internal rhythm but body can
speed it up or slow it down
Vagus nerve <; Sympathetic fibers >
Impulse Conduction, Visual
Heart Block
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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
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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)
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May progress to fibrillation
Cardiac Cycle
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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
Cardiac Cycle, Visual
Heart Sounds
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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
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Caused by turbulance of blood flow
Fairly common in children/elderly people
Sounds, cont.
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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
Cardiac Output
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CO is amount of blood pumped out by
each side of heart
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Stroke volume is volume of blood
pumped out by each ventricle with each
heartbeat
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Actually each ventricle in ONE minute
SV >s as force of ventricular contraction
>s
CO is PRODUCT of heart rate (HR) x
stroke volume (SV); CO=HR x SV
Output, cont.
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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
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> volume or speed of venous return >s SV &
force of contraction
< volume or speed of venous return <s SV &
force of contraction
Output, cont.
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“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
Output and Regulation, cont.
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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
Output & Regulation, cont.
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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
heatheart rate and coldheart rate
Congestive Heart Failure
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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
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Right side fails = Peripheral congestion occurs
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vessels in lungs swells-fluid leaks-pulmonary edema-if
untreated, person suffocates
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
Electrocardiogram (ECG)
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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
Arterial Pulse
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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
Blood Pressure Points, Visual
Blood Pressure…
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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
Auscultatory Method for BP
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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 110-140/7580
Varies with age, weight, mood, race, activity,
and posture
Blood Pressure, Visual
BP Math…or whatever
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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
Factoring the factors
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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
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Retain or excrete water
Also produce RENIN
Factors, cont.
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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
Enough of factoring, already..
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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 salthypertonic blood which
absorbs water from tissues increasing blood
volume and BP
The end of factoring…Yeah!!
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TOO much fatsexcessive fats in blood
Makes blood more viscous and more
difficult to pump
Peripheral resistance is increased which
increases the blood pressure
Hypotension
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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
Hypertension
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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
Hypertension, cont.
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Most cases (90%+) are primary or essential
which CANNOT be accounted for by any
specific organic cause
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Diet, obesity, heredity, race, stress involved
Treatment for hypertension
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diuretics
vasodilators/beta blockers
ACE-inhibitors (inhibit renin)
Cardiac inhibitors (calcium channel blockers)
Lifestyle changes