CHAPTER 15 THE HEART - Part A
I. INTRODUCTION
the continuous, rhythmic beating of the human heart ensures circulation of blood throughout the body. This circulation
1. Delivers oxygen, nutrients, hormones & regulatory molecules.
2. Removes waste products from organs.
3. Pumps blood into 2 closed circuits: the systemic circulation and the pulmonary circulation (fig. 15.1)
II. STRUCTURE OF THE HUMAN HEART
A. Size & location Fig. 15.3 & 15.4
1. Cone shaped, fist sized, ______ grams, _____cm long
________ cm wide, _______ cm thick
a. Rests on _______________________
b. Near middle of thoracic cavity in __________________________________
(mass of tissues between lungs, extending from sternum to
vertebral column)
c. __________ of mass of heart lies to left of body's mid-line
d. ____________ is the pointed end formed by tip of the left ventricle == apical heart beat felt or heard between 5th and 6th ribs, 7.5cm to left of the midline
e. Base is the wide superior & _______________ margin of heart
B.Coverings of heart Fig. 15.4 & 15.5
1. Heart is 4-chambered, hollow, muscular organ enclosed in a layered pericardium
a._______________________________ pericardium
1.) Forms strong protective sac
2.) Serves to _____________________________________
3.) Surrounds double layered sac
b. Double layered sac
1.) Inner layer = thin serous membrane called __________ that covers muscle of heart
2.) Outer layer = fibrous conn. tissue called ___________ that forms inner layer of fibrous pericardium
c. Pericardial cavity is a space between the visceral & parietal layers
C.Wall of heart is made of _______ layers Fig. 15.5 and Table 15.1
1._________________________ -find description in table
2.__________________________________________�
a. largest mass of heart;
b. thick layer of cardiac muscle;
c. contraction pumps blood;
d. regional differences in thickness
e. reflects resistance offered by blood vessels
3._______________________________________ � endothelium of connective tissue
DFour heart chambers � right & left atria and rt. & left ventriclesFig. 15.6
1. Right atrium
a. Functions as a reservoir between contractions
b. Receives blood from
1.)__________________________________,
2.)__________________________________,
3.)__________________________________
4.)Pumps blood into right ventricle
5.)Thinner walls than ventricle; smooth walls
6.)Rt. Atrium is _____________________________
than left
7.)Separated from ventricle by ______________________
2. Right ventricle (involved in pulmonary circulation)
a. Receives blood from right atrium
b. Pumps blood to ___________________
c. Pulmonary valve separates rt. ventricle from ________
3. Left atrium
a.Receives blood returning from lungs via ___________
b. Functions as reservoir between contractions
c. Separated from ventricle by ______________________
d. Pumps blood ---------------> left ventricle
4. Left ventricle �
a. Receives blood from left atrium
b. Pumps blood -> aorta through aortic valve
c. Involved in systemic circulation.
d. Forms ______________________________ of heart
e. muscle layer is ______________________ than that of rt. ventricle
E. Ventricles are lined by trabeculae carneae (muscular bundles);
contain papillary muscles & chordae tendineae (heart strings)
III. Skeleton of heart Fig. 15.8 & 15.9
A. __________________________________________________ tissue encloses
proximal end of pulmonary artery, aorta, & A-V orifices
B. Rings of tissue are attachments for valves & muscle fibers; prevent orifices from
dilating excessively during contractions.
IV. Septa of heart Fig. 15.6
A.________________ between the chambers; separate heart into left & right
portions
1.Interatrial septum: between rt & left atria; location of fossa ovalis (foramen ovale in fetus)
2. Interventricular septum: between rt. & left ventricles; carries large branched
bundles of specialized conducting fibers
V. Other structures
A. ______________________________________(fig. 15.12) � small dog ear flaps that
function to increase volume of their respective atria; contain musculi pectinati
(pectinate muscle) � roughened, inner surface of groups of small, muscular
bundles
B._________________________________ � prevent backflow of blood;
1.Between atria & ventricles & between ventricles & vessels
2.Right ___________________________________
3.Left bicuspid = ____________________________
4.Each valve consists of cusps that project from heart wall into opening
between atria & ventricles
C.Tricuspid valve � anterior, posterior & septal cusp
D.Mitral valve � anterior & posterior cusp
1.Tricuspid and mitral valves are regulated by
___________________________________
E.Semilunar valves � at root of aorta & pulmonary trunk; prevent backflow into
ventricles; work by gravity
F. Fetus - ductus arteriosus becomes liagamentum arteriosum after birth
VI.Path of blood through heart Fig. 15.10 & 15.11
A.Right atrium receives blood __________ in O2 &___________ in CO2 from
venae cavae & coronary sinus
B. Rt. ventricle pumps this blood into pulmonary circulation via pulmonary
artery
C.Blood is oxygenated in lungs, CO2 removed
D.Left atrium ___________________________________ blood with O2
E.Left ventricle pumps this blood into aorta & coronary arteries
F.Blood supply to heart muscle
1. Supplied via ____________________________,
2. Emptied via ________________________________________________
VII.Heart Actions Fig - 15.16 (very important graph)
A.Cardiac cycle : atria contract while ventricles relax; ventricles contract while
atria relax; pressure within chambers rises & falls in cycles. Cardiac cycle
initiated by generation of action potentials within the _____________
B.Cycle has 2 basic components:
1._________________________ � contraction phase � blood ejected from
chambers
2._________________________________ � relaxation phase; blood fills
chambers
C.Changes in blood pressure & volume are reflected in phases of the cycle:
D.Chamber fills ----> pressure increases
E.Chamber empties ----> pressure decreases
F.Can you explain the increases and decreases in volume and pressure that are
illustrated by the graph in Fig. 15.16 ?
G. Can you locate the dicrotic notch in this
graph?
H. Why does the pressure in the atrium rise after the A-V valve closes?
I. Why does the volume begin to increase in the ventricle before the atrium
contracts? (Exercise)
VIII.Heart sounds Fig. 15.17
A. _________________________________ � listening to heart through a
stethoscope
1.Lubb-dupp sounds are reflective of the closure of valves & blood hitting the
valves
B.________________________ sound ----> results from closure of tricuspid &
mitral valves (beginning of systole); blood hits inferior aspect of AV valves
C._______________________ sound ------> results from closure of aortic &
pulmonary semilunar valves when pressure begins to fall (ventricular diastole)
1.Blood falls back (gravity) & hits anterior aspect of valves
D. A 3rd sound sometimes found in young individuals results from rapid influx of
blood into partially filled ventricles
IX.Cardiac muscle fibers
A.Cardiac muscle fibers interconnect
B.Form a FUNCTIONAL ________________________________________
C.When any part of syncytium is stimulated, whole structure contracts as 1 unit
D.Atrial syncytium separated from ventricular syncytium by fibrous skeleton
1.EXCEPT: small region in floor of _______________________________
X.Cardiac conduction system FIG. 15.18 & 15.19
A.The human heart possesses its own conduction system; it can beat
independently of the body even after being separated from its nerve supply.
Nerves serve to modulate intrinsic rhythm. Conduction system is made of
nodes & fiber bundles throughout the heart
1. Conduction system--made of specialized cardiac muscle tissue
2. This tissue initiates & conducts depolarization waves through myocardium 3.Impulses begin in _____________ node = sinoatrial node.
a. Cells of SA node are special cardiac muscle cells with the property
of automatic excitation; these cells initiate the beat == pacemaker
3. Impulses pass slowly to the ________ node = atrioventricular node
a. Internodal fiber bundles around atrial muscle fibers conduct action potential to A-V node
B. A-V node causes _________________________ in transmission of impulse to
ventricles;
1.This pause permits atria to empty ******
C. A-V bundle == Bundle of His - makes up mass of muscle fibers
D.______________________________________________ fibers send rapid
impulses throughout walls of ventricles via 2 branches: rt. & left bundle
branches
E. Muscle fibers in ventricular walls arranged in whorls: squeeze blood out of
contracting ventricles as action potential passes through cardiac conduction
system FIG. 15.20
XI.The electrocardiogram: ECG or EKG Fig. 15.21
A. Amplification & recording of heart impulses can be transmitted to an
electrocaridograph
B.Calibration lines on all ECGs
1.Horizontal lines are used for _________________________
2.Vertically placed lines are used for ____________________
3.Three basic features of an ECG
a.___________ wave: depolarization of ________________________
b.______________ complex: depolarization of ventricles
c._________ wave: _____________________________________ of
ventricles
4. Shapes of the waves & time intervals are important for proper evaluation
5. ECG: most important indicator of cardiac function
C.Tachycardia (clinical 15.2): fast heart rate from fever, hormones, drugs = >_______ beats/min
D.Bradycardia: slow heart rate common in atheletes == <__________ beats/min
E.Arrhythmia: alteration in the normal heart rhythm
F.Atrial flutter __________________ contractions/min; contractions are
synchronous
G.Fibrillation- rapid contractions; contractions are asynchronous: atrial fib ==
patient can live since veins will push blood in; ventricular fib == fatal (shock)
**********
H.Heart block-transmission of action potential becomes delayed or blocked at
some point in conduction system
1.Conditions that may block conduction
a.Lack of adequate blood supply
b.presence of scar tissue
c.Inflammatory processes with AV bundle or AV node
d.Excessive stimulation of vagus nerve
e.Impulses in regions other than the SA node -- called ectopic foci
I.Conditions leading to ectopic foci
1.Calcified regions that press on cardiac muscle
2.Areas of ischemia
3.Stress
XII. What regulates the cardiac cycle & heart rate? Fig. 15.23
Neural control by autonomic nervous system, hormones, temperature,
concentration of ions, physical exercise, gender, age, disease, athletic training
A. Neural control
1. Branches of sympathetic & parasympathetic nerve fibers innervate
S-A & A-V nodes
2. Parasympathetic impulses ____________________________ heart action
3. Sympathetic impulses _________________________________ heart action
4. Cardiac center in medulla oblongata regulates autonomic impulses
B. Parasympathetic innervation
1. Originates in cardiac inhibitory center in ____________________________
2. Conveyed to heart by vagus nerve
3. Slows heart by releasing ________________________________________
4. Parasympathetic innervation is dominant
5. Ventricular escape � new rhythmic impulses generated in an abnormal site:
Ectopic beat
C. Sympathetic innervation
1. Originates in cardiac acceleratory center in ______________________
2. Carried to heart by accelerator nerves
3. Accelerator nerve stimulation � releases ______________________
a. Leads to : ____ heart rate & ____ strength of contraction
4. Medulla: responsible for maintaining balance of inhib. & stim. effects
XIII. Hormones
A. Stress --------> epinephrine & norepinephrine released -------> ______heart rate
B. Thyroid hormones ___________________________________ heart rate:
C. Amount of hormone affects strength of contraction
XIV. Temperature
A. High temp ----->___________ heart rate
B.Low temp -----> ___________ heart rate; hypothermia�can result in death
XV. Ionic concentration
A. K+ --excess ----------> _________ of heart rate & strength of contraction
B. Ca++ --- excess ------> causes spasticity
C. Na+ --- excess --------> depresses function; deficiency: cardiac fibrillation
XVI. Gender, age and condition
A. Adult female: __________ beats/minute
B. Adult male: ___ beats/minute
C. Infant: _______ beats/minute
D. Child: _______ beats/minute
E. Trained athlete: heart enlarges & ____ pumping efficiency (50 beats/minute)
F. Diseased heart �can't beat effectively; can result in failure
Interesting Web Sites