A&P chapter 15
Where does the pointed apex lie?
at the 5th intercostal space
During atrial systole and ventricular diastole
atria contract and ventricles are relaxed the AV valves open and the semilunar valves close Atrial systole pushes remaining 30% of blood into the ventricles, causing ventricular pressure to increase
cardiac cycle
atria contracts (atrial systole) while ventricles relax (ventricular diastole) THEN ventricles contract (ventricular systole) while atria relax (atrial diastole) THEN both chambers relax briefly
cardiac muscle cells in the atrial walls
atrial syncytium
sympathetic and parasympathetic fibers modify the heart rate in response to changing conditions, such as:
physical exercise, body temperature, fight-or-flight response, concentration of various ions, such as K+ and Ca+2
Where does the base of the heart lie?
beneath the second rib
Branches of the right coronary artery
posterior interventricular artery: supplies posterior ventricles. right marginal branch: supplies right atrium and ventricle
the rings of dene connective tissue also
provide attachments for heart valves and muscle fibers and prevent excess dilation of heart chambers during contraction.
Two closed circuits (pathways) are included in the cardiovascular system
pulmonary circuit and systemic circuit
Right side of the heart
pumps blood to the pulmonary circuit, blood returns to the left side
Left side of the heart
pumps to the systemic circuit, blood returns to the right side
Sympathetic impulses that innervate heart
reach heart on accelerator nerves increase heart reate, due to influence on SA and AV nodes, atrial and ventricular myocardium
Parasympathetic impulses that innervate heart
reach heart via vagus nerves lower SA node rate of 100 beats/minute to 60-80 beats/min decrease heart rate, due to influence ono SA and AV nodes
Right atrium
receives blood returning from systemic circuit (from the superior and inferior vena cava and coronary sinus); pumps blood to right ventricle
What is "hidden" in the large QRS complex?
record of atrial replorization is "hidden" since the ventricular or depolorization is a much larger event
Heart transplant
replacement of most of a failing heart with a donor heart
pulmonary valves
return blood from lungs to left atrium
superior and inferior vena cavae
return oxygen poor blood to the heart
Interatrial septum
separates left and right atria
interventricular septum
separates left and right ventricles
Mitral (bicuspid) valve
separates left atrium from left ventricle
aortic semilunar valve
separates left ventricle from aorta
tricuspid valve
separates right atrium from right ventricle
pulmonary semilunar valve
separates right ventricle from pulmonary trunk
The size of the heart
size of fist, varies with body size, averages 14 cm long, 9cm wide
cardiac muscle in the ventricular walls
called the ventricular syncytium
Stem Cell Technology
cardiac muscle tissue can now be cultured from altered somatic cells or from stem cells; may allow "stem cell heart patches" in the future
pulmonary circuit
carries oxygen poor blood from heart to lungs, drops off carbon dioxide, picks up oxygen, flows back to heart
Branches of the left coronary artery
circumflex branch: supplies left atrium and ventricle Anterior interventricular (left anterior descending) artery: supplies walls of ventricles
Junctional fibers
conducts impulses from SA node to AV node
Internodal atrial muscle
conducts impulses from SA node to atria
Systole
contraction of the heart chamber
parietal pericardium
deep to fibrous pericardium, outer layer of serous membrane
Coronary sinus
enlarged vein into which other cardiac veins drain; drains into right atrium
Portions of the pericardium
fibrous pericardium, parietal pericardium, visceral pericardium, pericardial cavity
chordae tendinae
fibrous strings that attach cusps of tricuspid and mitral valves to papillary muscle in the wall of the heart
Auricles
flap-like projections from atria, which allow atrial expansion
The heart wall
has 3 distinct layers
Regulation of the cardiac cycle
heart rate and volume of blood pumped change to meet requirements
pericardial cavity
space between visceral and parietal layers of serous pericardium
Visceral pericardium
inner layer of serous membrane; attached to surface of heart; also called epicardium
HEART
is a hollow, cone-shaped organ, containing a double pump, it is divided into left and right halves
Heart
is a hollow, cone-shaped, muscular pump; generates HYDROSTATIC force to transport respiratory gases , nutrients, and wastes throughout the body
Electrocardiogram (ECG, EKG)
A recording of electrical changes that occur in the myocardium during the cardiac cycle. Used to assess ability of heart to conduct impulses
cardiovascular system
Consists of the heart and blood vessels
Cardiac conduction system
Specialized group of cardiac muscle cells, which initiate and distribute cardiac action potentials through myocardium
Diastole
relaxation of the heart chamber
(Erythrocytes ) red blood cells)
44% total blood volume, carry oxygen around the body on an iron-containing protein(hemoglobin)
purkinje fibers
large fibers that conduct impulses to ventricular myocardium; conduct impulses to apex first; whorled pattern of muscle in ventricles contract with twisting motion
Heart sounds
A heartbeat through a stethescope sounds like "lubb-dupp" Sounds are due to closing of heart valves, and vibrations associated with a sudden slowing of blood flow during contraction/relaxation of chambers
Left Ventricular Assist Device (LVAD)
mechanical half-heart, used in some cases temporarily, until donor heart is available.
Cardiac center is __________________________ performs neural regulation of heart
medulla oblongota
AV (atrioventricular) bundle
Conducts impulses rapidly between AV node and bundle branches
AV (atrioventricular) node
Conducts impulses to AV Bundle; delays impulse, so that atria finish contracting before ventricles contract
pericardium (pericardial sac)
Covering over heart and proximal ends of large blood vessels
Pressure and volume changes of a cardiac cycle
During a cardiac cycle, the pressure in the heart chambers rises and falls Pressure changes open and close the valves
Characteristics of cardiac muscle cells
Have central nucleus, and form branching networks Intercalated discs between cells contain DESMOSOMES for structural support, and GAP JUNCTIONS to spread action potentials through a network of cells. Form a functional syncytium mass of merging cells that function as a unit: 2 such masses exist in the heart
Where is the heart located?
Inside the thoracic cavity, in mediastinum, behind sternum, above diaphragm, near lungs
The deflections in the normal ECG, or waves include:
P WAVE: atrial depolorization; occurs just prior ro atrial contraction QRS COMPLEX (3 waves): ventricular depolorization; occurs just prior to ventricular contraction
Left ventricle
Receives blood from the left atrium; pumps blood to systemic circuit
Left atrium
Receives blood from the pulmonary veins pumps blood to left ventricle
Right ventricle
Receives blood from the right atrium; pumps blood to lungs
Left and right bundle branches
Split off from AV bundle, conduct impulses to Purkinje fibers on both sides of heart
SA node (pacemaker)
normally controls the heart rate, and heart rate changes occur due to factors that influence the SA node
"Lubb"
The first heart sound (S1) Occurs during the ventricular systole Associated with closing of the AV valves
How do the heart chambers function?
The heart chambers function in a regulated coordinated manner
"Dupp"
The second heart sound (S2) occurs during ventricular diastole associated with closing of the pulmonary and aortic semilunar valves
Epicardium
outer layer, thin. forms inner lining of all heart chambers
What make up the skeleton of the heart?
These rings along with other fibrous masses in the interventricular septum make up the skeleton of the heart
Atria
Thin-walled upper chambers; receive blood returning to heart
SA (sinoatrial) node
pacemaker, initiates rhythmic contractions of the heart
Cardiac veins drain blood from myocardium
paths of veins lie nearly parallel to those of coronary arteries
Murmur
abnormal heart sound derived from incomplete closure of cusps of a valve
The coronary arteries
are the first two branches of the aorta
Left and right coronary arteries
supply blood tissues of the heart
rings of dense connective tissue
surround origins of pulmonary trunk and aorta, and orifices between atria and ventricles
CARDIAC CYCLE
the events that occur during a heartbeat
Ventricles
thick-walled lower chambers; pump blood into arteries
Fibrous pericardium
tough, outer Layer that surrounds double-layered serous membrane
Arteries
transport blood away from the heart
Capilllaries
transport blood between arteries and veins, and perform nutrient, gas, and waste exchange
Blood vessels
transport blood throughout the body
Veins
transport blood to the heart
systemic circuit
transports oxygen rich blood and nutrients to body cells, removes waste from cells, flows back to the heart
Early in the ventricular diastole
ventricular pressure is lower than the atrial pressure atria and ventricles are relaxed AV valves open, and semilunar valves are closed About 70% of blood flows passively from atria into ventricles
T wave
ventricular repolorization; occurs just prior to ventricular relaxation
During ventricular systole and atrial diastole
when ventricular pressure rises about atrial pressure, AV valves close CHORDAE TENDINAE prevent the cusps of the valves from bulging too far backward into the atria atria relax blood flows into atria from venae cavae and pulmoonary veins ventricular pressure continues to increase, and opens semilunar valves Blood flows into the pulmonary trunk and aorta