Download Nerve activates contraction

Essentials of Human Anatomy & Physiology
Seventh Edition
Elaine N. Marieb
Slides 11.1 – 11.19
Lecture Slides in PowerPoint by Jerry L. Cook
Modified by J. Kalinowski 3/12
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
The Cardiovascular System
 A closed system of the heart and blood
vessels
 The heart pumps blood
 Blood vessels allow blood to circulate to all
parts of the body
 The function of the cardiovascular
system is to deliver oxygen and
nutrients and to remove carbon dioxide
and other waste products
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The Cardiovascular System
 Cells make the exchange of nutrients &
wastes only with the fluid in their
immediate vicinity.
 Changing & refreshing these fluids is
necessary to prevent buildup of wastes
and to replenish the nutrient supply
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The Heart
 Location
 Thorax between the lungs
 Posterosuperior base points toward right
shoulder beneath 2nd rib
 Pointed apex directed toward left hip, rests
on diaphragm at top of 6th rib
 About the size of your fist
 Weighs less than a pound: 250-350 grams
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The Heart
Figure 11.1
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The Heart: Coverings
 Pericardium – a double serous
membrane
 Visceral pericardium/epicardium
 Next to heart
 Parietal pericardium
 Outside layer
 Serous fluid (reduce friction) fills the
pericardial cavity: space between
layers of pericardium
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The Heart: Heart Wall
 Epicardium
 Outside layer
 This layer is aka the visceral pericardium
 Myocardium
 Middle layer
 Mostly cardiac muscle with fibrous CT support
 Actual contracting tissue layer
 Endocardium
 Inner layer
 Endothelium lining reduces friction and
continues into BV
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External Heart Anatomy
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Figure 11.2a
External Heart Anatomy
Pectinate
muscles
Chordae
Tendinae
Trabeculae
carnae
Papillary
Muscle
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Figure 11.2a
The Heart: Chambers
 Four chambers
 Atria - receiving chambers
 Right atrium – receives from body
 Left atrium – receives from lungs
 Thin walled – do not need great pumping
power
 Auricle – flap that increases atrial volume
 Foramen ovale: one structure that bypasses
fetal lungs. (ductus arteriosus is the other)
 Close up when infant starts breathing air –
become fossa ovalis and ligamentum
arteriosum (remnant structures)
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The Heart: Chambers
 Four chambers
 Ventricles - discharging chambers
Right ventricle – goes to lungs
Left ventricle – goes to body
Thick muscular walls – need pumping
power
Left ventricle pumps to entire body
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
The Heart:
 Septum: divides heart into right
and left halves
 Superior vena cava: returns blood
to heart from head, shoulders, and
arms
 Inferior vena cava: returns blood to
heart from rest of body
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
The Heart:
 Pulmonary trunk: BV out of right
ventricle to pulmonary arteries
 Pulmonary arteries: to lungs
 Pulmonary veins: back to left side
of heart
 Aorta: Largest Artery in body
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The Heart: Valves
 Allow blood to flow in only one direction
 Four valves
 Atrioventricular valves – between atria and
ventricles
 Papillary muscles: attached to chordae
tendineae to help prevent valves from
allowing backflow
 Bicuspid valve (left) – aka. Mitral valve
 Tricuspid valve (right)
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The Heart: Valves
Semilunar valves between
ventricle and artery
Pulmonary semilunar valve
(right)
Aortic semilunar valve (left)
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Operation of Heart Valves
Figure 11.4
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 Heart
sounds - result from
closing of valves

1. Lub - AV valve closure –
first sound

2. Dup - semilunar valve
closure – second
sound
The Heart
 Right and left side act as separate
pumps
 Pulmonary circuit – carries blood to lungs &
back – right side of heart
 Superior & inferior vena cava  rt. Atrium 
tricuspid valve  rt. Ventricle  pulmonary
SL valve  pulmonary trunk  pulmonary
arteries  lungs
 Systemic circuit – carries blood to body &
back – left side of heart
 Pulmonary veins  left atrium  bicuspid
valve  left ventricle  aortic SL valve 
aorta  body
 How the Heart Pumps
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Coronary Circulation
•blood contained in the heart does not
nourish the heart
•right & left coronary arteries and their
major branches supply blood to heart
•cardiac veins empty into coronary sinus
which drains into right atrium
•left ventricle works hardest so needs most
blood
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Know both your diagrams:
1.Heart parts
2.Pathway of circulation
Two Events happen in a heart
beat
Electrical event which causes the:
Muscular contraction – described in
terms of ventricular events
 Either event can have problems so
doctors need the ability to check each
one.
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The Heart: Conduction System
 Cardiac muscle needs
organization/rhythm and speed
control for maximum efficiency
 So two controlling/coordinating
systems are required
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The Heart: Conduction System
 2 systems:
 Autonomic NS
 Sympathetic – increases heart rate &
force of contraction (accelerators)
 Parasympathetic – decreases heart rate
& force of contraction (brakes)
 Nodal system (Intrinsic conduction
system)
 Coordinates contraction of muscle cells
to force blood in correct pathway
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The Heart: Conduction System
 Special tissue sets the pace
 Gap junctions – coordinate cell to cell
transmission
 Sinoatrial node
 Pacemaker located in wall of right atria
 Initiates depolarization wave
 Atrioventricular (AV) node
 Delays signal momentarily so atria have
time to fully contract
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The Heart: Conduction System
 AV bundle & Bundle branches
 send signal down into septum for septal
cell excitation
 Purkinje fibers
 Allows electrical signal to penetrate deep
into every cell in the ventricular
myocardium
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Heart : Conduction system
How the Conduction System Works
Figure 11.5
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The Heart: Conduction System
 The conduction system coordinates and
synchronizes heart activity for maximum
efficiency
 Anything that goes wrong with this system
will cause a malfunctioning heart!!!
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Muscular Event: Cardiac Cycle
 Alternate contraction & relaxation of
heart muscle
Systole = contraction
Diastole = relaxation
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The Heart: Cardiac Cycle
 Cardiac cycle – events of one complete
heart beat
 Mid-to-late diastole
 Heart is completely relaxed – AV valves
open, SL valves closed
 Blood flows from atria to ventricles (70% of
filling occurs) then atria contract
 Rising blood pressure closes AV valves
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The Heart: Cardiac Cycle
 Ventricular systole
 AV valves closed due to rising blood
pressure
 Atria begin filling again
 Isovolumetric contraction phase – Both
valves closed while ventricles contract –
builds blood pressure which forces SL
valve open
 Ventricular ejection phase – blood is
expelled into aorta or pulmonary trunk
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
The Heart: Cardiac Cycle
 Early diastole/isovolumetric relaxation
 Ventricles relax
 Pressure drops and backflow closes SL
valves
 Atrial pressure begins to force open AV
valves
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Filling of Heart Chambers –
the Cardiac Cycle – page 337
Figure 11.6
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



Cardiac cycle = 0.8 secs
1. atria systole = 0.1 secs
2. vent systole = 0.3 secs
3. total heart relaxation (quiescent
period) = 0.4 secs
◦ only time heart gets to relax



1. flow of blood is controlled by pressure
changes
2. blood flows along pressure gradient
through any available opening
3. An echocardiogram is a sonogram of the
heart and is used to visualize the
opening/closing of valves and working of
muscles


electrical events caused by conducting
system are recorded as deflection waves
transmitted to entire body by means of
electrolytes.
The recording of heart electrical waves is
called an ECG or EKG - electrocardiogram
Electrocardiography
 Know the info from your notes about each of
these deflection waves
 P wave
 QRS complex
 T wave
 All of these wave patterns have specific
magnitudes and length of time patterns in a
healthy heart
 Any deviation from these norms may mean
a heart defect within the conduction system
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Fibrillation involves
several types of irregular
non-pattern




Diagnose Wenckebach syndrome
Normal ECG to flatline
Examples of various disorders on ECG
echocardiogram
Frank-Starling Law of the Heart
Degree of stretch determines SV
- more stretch = more force of
contraction
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Regulation of Heart Rate
 FUNCTION: ensure that blood is
distributed evenly between system and
pulmonary circuits
 If one side starts pumping more blood, the
other side receives that blood – stretching
ventricles causes increased force of
contraction = more pumping power
 If one side is not responding correctly =
this can cause blood to back up causing
heart disorder
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

Page 336: heart block, tachycardia,
bradycardia
Page 339: congestive heart failure,
pulmonary congestion, peripheral congestion


Ectopic focus: defective pacemaker results
in AV node becoming new pacemaker –
interferes with the pacing of the ventricular
depolarization
Extrasystole: premature contraction – a
section of heart may become
hyperexcitable due to caffeine, nicotine,
etc and start generating a quicker impulse
interfering with normal pacing


Decompensated heart: seriously weakened
heart – irreparable
Congenital heart defects = present at birth
◦ Patent ductus arteriosus: ductus doesn’t close
properly at birth allowing O2 and de-O2 blood
to mix
◦ Septal defect: opening left in septum possibly
due to open foramen ovale or developmental
defect

Tetralogy of Fallot (congenital): SERIOUS 4
defects of heart
◦
◦
◦
◦

Stenosed pulmonary valve
Aorta arising from both ventricles
Interventricular septal opening
Enlarged right ventricle
Surgical repair as soon as possible



Arteriosclerosis (atherosclerosis): fatty
deposits on blood vessel walls –
accelerated by inactivity, smoking, stress,
poor diet
Cardiac tamponade: compression of the
heart due to fluid/blood in pericardial
cavity
Cor pulmonale: pulmonary hypertension
may result in pulmonary embolism –
associated with lung disorders such as
emphysema



Heart palpitation: unusually strong, fast, &
irregular heartbeat
Mitral valve prolapse: incompetent valve flap
on mitral valve allows backflow
Myocarditis: inflammation of heart muscle –
can be caused by infection elsewhere in the
body traveling to heart muscle (ex. Strep
infections)