Chapter 19- Heart Flashcards
Pulmonary circuit
carries blood to the lungs for gas exchange and returns it to the heart; supplied by right side of heart
- pumps oxygen-poor blood to the lungs via the
pulmonary trunk which divides into the left and right
pulmonary arteries (deoxygenated blood)
Systemic circuit
– supplies blood to every organ of the body including other parts of the lungs and the wall of the heart; supplied by left side of heart
- Pulmonary veins return oxygen-rich (oxygenated)
blood to the heart; blood heart leaves via the aorta
and returns via the inferior and superior vena cavae
artery
systemic - oxygenated
pulmonary - deoxygenated
vein
systemic - deoxygenated
pulmonary - oxygenated
Position of Heart in the Thoracic Cavity
Heart located in mediastinum, between lungs
Base—wide, superior portion of heart,
large vessels attach here
Apex—tapered inferior end, tilts to the
left
Pericardium
-double-walled sac that encloses the heart
-Allows heart to beat without friction, provides room to expand, yet resists excessive expansion
- Anchored to diaphragm inferiorly and sternum anteriorly
Fibrous pericardium
outer wall, not attached to heart
Serous pericardium
-Parietal layer—lines fibrous pericardium
-Visceral layer (epicardium)—covering heart surface
Pericardial cavity
space between parietal and visceral layers of
serous pericardium, filled with 5 to 30 mL of pericardial fluid
Pericarditis
painful inflammation of the membranes
3 layers of heart wall
epicardium, myocardium, and
endocardium
Epicardium (visceral layer of serous pericardium)
- Serous membrane covering heart
- Adipose in thick layer in some places
- Coronary blood vessels travel through this layer
Endocardium
- Smooth inner lining of heart and blood vessels
- Covers the valve surfaces and is continuous with endothelium
of blood vessels
Myocardium
- Layer of cardiac muscle proportional to workload
-Muscle spirals around heart which produces wringing motion, vortex of the heart - Fibrous skeleton of the heart: framework of collagenous and elastic fibers
-Provides structural support and attachment for cardiac muscle and anchor for valve tissue
-Electrical insulation between atria and ventricles; important in timing and coordination of
contractile activity
Two upper chambers
-L and R atria
-The atria are receiving chambers that
receive blood returning to the heart.
Two lower chambers
– L and R ventricles
-R ventricle wraps around the L ventricle in
a C-shape, but both ventricles have the
same volume.
-The ventricles are the “pumps” that eject
blood.
Atrioventricular valves (AV valves)
Regulate the openings between the
atria an the ventricles
R AV valve
three cusps; tricuspid
valve
L AV valve
two cusps; mitral valve
Chordae tendinae
attach the valves to the papillary muscles on the floor of the ventricle and stop valves from flipping inside out or bulging into the atria when the ventricles contract
Semilunar valves
Regulate blood flow from the ventricles
into the great arteries; both have three
cusps
aka. =Aortic valve, Pulmonary valve
Aortic valve
controls opening from L ventricle to the aorta
Pulmonary valve
controls opening from R ventricle to the pulmonary trunk
The Coronary Circulation
5% of blood pumped by heart is pumped to the heart itself through the coronary
circulation to sustain its strenuous workload
* 250 mL of blood per minute
* Needs abundant O2 and nutrients
Anterior interventricular branch
Supplies blood to both ventricles and anterior two-thirds of the interventricular septum
left coronary artery branches off __________
the ascending aorta
Circumflex branch
- Passes around left side of heart in coronary sulcus
- Gives off left marginal branch and then ends on the posterior side of the heart
- Supplies left atrium and posterior wall of left ventricle
Right coronary artery (RCA) branches off ___________
the ascending aorta
-Supplies right atrium and sinuatrial node (pacemaker
Right marginal branch
Supplies lateral aspect of right atrium and ventricle
Posterior interventricular branch
Supplies posterior walls of ventricles
Angina pectoris
-chest pain from partial obstruction of coronary blood flow
-Pain caused by ischemia of cardiac muscle
-Obstruction partially blocks blood flow
-Myocardium shifts to anaerobic fermentation, producing lactate and thus
stimulating pain
Myocardial infarction
-sudden death of a patch of myocardium resulting from long-term obstruction of coronary circulation
-Atheroma (blood clot or fatty deposit) often obstructs
coronary arteries
-Cardiac muscle downstream of the blockage dies
-Heavy pressure or squeezing pain radiating into the left arm
-Some painless heart attacks may disrupt electrical
conduction pathways, leading to fibrillation and cardiac arrest
Cardiomyocytes
striated, short, thick, branched cells, one central nucleus surrounded by light-staining mass of
glycogen
Intercalated discs
join cardiomyocytes end to end with three features:
interdigitating folds, mechanical junctions, and electrical junctions
Sinus rhythm
normal heartbeat triggered by the SA node
* Adult at rest is typically 70 to 80 bpm (vagal tone)
Ectopic focus
a region of spontaneous firing other than the SA node
* May govern heart rhythm if SA node is damaged
Nodal rhythm
if SA node is damaged, heart rate is set by AV node, 40 to 50 bpm
* Other ectopic focal rhythms are 20 to 40 bpm and too slow to sustain life
P wave
SA node fires, atria depolarize and contract; atrial systole begins 100 ms after SA signal
PR interval
signal conduction through AV node, before activating ventricles
QRS complex
ventricular depolarization; complex shape of spike due to
different thickness and shape of the two ventricles
QT interval
duration of ventricular depolarization; shorter during exercise
ST segment
ventricular systole; corresponds to plateau in myocardial action potential
T wave
ventricular repolarization and relaxation
difference between cardiac and sk AP
-prolonged repolarization
-action potential is longer
-much longer refractory period
ventricular fibrillation
- Serious arrhythmia caused by electrical signals traveling randomly
- Heart cannot pump blood; no coronary perfusion
- Hallmark of heart attack
- Defibrillation—strong electrical shock with intent to depolarize entire myocardium and reset heart to sinus rhythm
Atrial fibrillation
chaotic depolarizations that do not
stimulate ventricles; common in elderly and alcoholics
Heart block
failure of any part of the cardiac conduction system to conduct signals, usually result of disease or degeneration of conduction system
Premature ventricular contraction
ventricular ectopic focus with extra beat; may result from stress, lack of sleep or stimulants
what governs fluid movement
pressure causes flow and resistance opposes it
the flow of fluid
- Fluid will only flow if there is a pressure gradient (pressure difference)
- Fluid flows from high-pressure point to low-pressure point
- Pressure measured in mm Hg with a manometer (sphygmomanometer for BP)
Cardiac cycle
one complete contraction and relaxation of all four chambers of the heart, total duration of the cardiac cycle is approx. 0.8 second in a heart
beating 75 bpm
diastole
relaxation
systole
contraction
Opening and closing of valves are governed by these pressure changes
- AV valves limp when ventricles relaxed
- Semilunar valves under pressure from blood in vessels when
ventricles relaxed
First heart sound (S1)
louder and longer “lubb,” occurs with closure of
AV valves, turbulence in the bloodstream, and movements of the heart wall
Second heart sound (S2)
softer and sharper “dupp,” occurs with closure of
semilunar valves, turbulence in the bloodstream, and movements of the heart wall
Ventricular filling – three phases
a) Rapid filling
b) Diastasis (slower filling) – P wave at end
c) Atrial systole
Isovolumetric contraction
- Ventricles depolarize, generate the QRS
complex, ventricles contract
Ventricular ejection
- Ventricular pressure exceeds arterial pressure;
- T wave occurs late in this phase
Isovolumetric relaxation
- Ventricular diastole
Control centers are in the medulla oblongata
-1 – 4 show the sympathetic autonomic nervous
system (ANS) innervation to the heart (via the
cardiac nerves)
-5 & 6 show the parasympathetic autonomic
nervous system innervation to the heart (via the
vagus nerve, CNX)
CO = SV x HR
-Cardiac Output = CO (ml/min or L/min), the amount of blood ejected per minute
-SV = stroke volume (ml/beat)
-HR = Heart Rate (beats/min)
Tachycardia
- resting adult heart rate above 100 bpm
- Stress, anxiety, drugs, heart disease, or fever
- Loss of blood or damage to myocardium
Bradycardia
-resting adult heart rate of less than 60 bpm
-In sleep, low body temperature, and endurance-trained athletes
Positive chronotropic agents
factors that raise the heart rate
Negative chronotropic agents
factors that lower the heart rate
Three variables govern stroke volume
- Preload - the amount of tension in ventricular myocardium immediately before it begins to contract
- Contractility - refers to how hard the myocardium contracts for a given preload
- Afterload - sum of all forces opposing ejection of blood from ventricle
