Chapter 18 (Lecture) - Heart Flashcards
when the mitral valve closes, it prevents backflow from the
left ventricle into the left atrium
what is the purpose of the chordae tendineae
anchor the AV valves in the closed position
what makes the heart valves open and close?
blood pressure
what valve separates the left atrium and left ventricle
bicuspid (mitral) valve
valve between the right atrium and right ventricle
tricuspid valve
prevents backflow of blood into the left ventricle
aortic semilunar valve
where does the blood leave from the left atrium
mitral (bicuspid) valve
a condition in which the valve flaps of the heart becomes stiff and consticts the opening
stenosis
separates the left ventricle and the aorta
aortic semilunar valve
separates the right ventricle and the pulmonary trunk
pulmonary semilunar valve
separates the right atrium from the right ventricle
tricuspid valve
where does blood leave from the left ventricle
aortic semilunar valve
prevents backflow of blood into the right ventricle
pulmonary semilunar valve
attached to the AV valve flaps
chordae tendineae
where does the blood leave from the right ventricle
pulmonary semilunar valve
what prevents the atrioventricular valves from everting during ventricular contraction
papillary muscles
which valve is most often faulty in the heart
mitral (bicuspid) valve
where does the blood leave from the right atrium
tricuspid valve
failure of which heart valve would allow blood to move from the left ventricle to the left atrium
mitral (bicuspid) valve
the right side of the heart pumps blood through which circuit
pulmonary
- the left side of the heart pumps blood through which circuit
- associated with the left ventricle
- long pathway throughout the entire body and encounters about 5x as much friction, or resistance to blood flow
systemic circuit
the right side of the heart receives what type of blood from where
oxygen-poor blood from body tissues
the left side of the heart receives what type of blood from where
oxygen-rich blood from the lungs
pumps blood to supply oxygen and nutrients to body tissues
- blood vessels that carry blood to and from the lungs
- served by the right ventricle
- short, low pressure circulation
pulmonary circuit
the blood vessels that carry blood to and from all body tissues
systemic circuit
receives blood returning from the systemic circuit
right atrium
receives blood returning from the pulmonary circuit
left atrium
- pumps blood INTO the pulmonary circuit
- forms most of the anterior surface of the heart
right ventricle
- pumps blood INTO the systemic circuit
- dominates the inferoposterior aspect of the heart and forms the apex
left ventricle
the medial cavity of the thorax containing the heart, great vessels, thymus and parts of the trachea, bronchi, and esophagus
mediastinum
posterior surface of the heart that is directed toward the right shoulder
base
inferiorly pointed part of the heart that points toward the left hip
apex
double-layered sac enclosing the heart and forming its superficial layer; has fibrous and serous layers
pericardium
- loosely fitting part of the pericardium
- made up of tough, dense CT
- functions to: protect the heart, anchors the heart to surrounding structures, and prevents the overfilling of the heart with blood
fibrous pericardium
- deep to the fibrous pericardium
- a thin, slippery, two-layer serous membrane that forms a closed sac around the heart
serous pericardium
- lines the internal surface of the fibrous pericardium
- attaches to the large arteries exiting the heart and continues over the external heart surface as the visceral layer (epicardium)
parietal layer of pericardium
- located between the parietal and visceral layers of the pericardium
- contains a film of serous fluid
pericardial cavity
- inflammation of the pericardium
- roughens surface membrane surfaces
pericarditis
- the visceral layer of the serous pericardium
- most superficial layer of the heart wall
- often infiltrated with fat, especially in older people
epicardium
- composed mainly of cardiac muscle and forms the bulk of the heart
- the layer of the heart that contracts
- contains CT fibers arranged in circular bundles that link all parts of the heart together
myocardium
CT fibers in the myocardium that reinforce it internally and anchors the cardiac muscle fibers
cardiac skeleton
- the innermost layer of the heart
- a glistening white sheet of endothelim (squamous epithelium) resting on a thin CT layer
- located on the inner myocardial surface and lines heart changers and covers the fibrous skeleton of the valves
endocardium
the internal partition that divides the heart longitudinally and separates the atria
interatrial septum
the internal partition that divides the heart longitudinally and separates the ventricles
interventricular septum
- also known as the atrioventricular groove
- encircles the junction of the atria and ventricles like a crown
coronary sulcus
- cradles the anteriorventricular artery (LAD)
- marks the anterior position of the septum separating the right and left ventricles
- continues as PI sulcus
anterior interventricular sinus
the right ventricle pumps blood into … which routes blood to the lungs where gas exchange occurs
pulmonary trunk
the largest artery in the body
aorta
returns blood from body regions superior to the diaphragm
superior vena cava
returns blood from body areas below the diaphragm
inferior vena cava
collects blood draining from the myocardium
coronary sinus
irregular ridges of muscle that mark the internal walls of the ventricular chambers
trabeculae carneae
muscle bundles that project into the ventricular cavity and play a role in valve function
papillary muscles
landmarks the posterior position of the septum that separates the left and right ventricles
posterior interventricular sulcus
- located in the interatrial septum, faces the right atrium
- marks the location of the fetal foramen ovale in the heart
fossa ovalis
small, wrinkled, protruding appendages which increase the atrial volume somewhat
auricles
- located the anterior portion of the right atrium and in the auricle of the left atrium
- look like the teeth of a comb
pectinate muscles
a C-shaped ridge that separates the posterior and anterior regions of the right atrium
crista terminalis
tributaries of the coronary sinus
- great cardiac vein
- small cardiac vein
- middle cardiac vein
several of these empty directly into the right atrium anteriorly
anterior cardiac veins
- empties the blood into the right atrium
- cardiac veins form this
coronary sinus
after passing through the capillary beds of the myocardium, the venous blood is collected by
cardiac veins
artery that courses to the right side of the heart
right coronary artery
two branches of the right coronary artery
- right marginal artery
- posterior interventricular artery (posterior inferior descending artery)
artery that serves the myocardium of the lateral right side of the heart
right marginal artery
- runs to the heart apex and supplies the posterior ventricular walls
- near the apex of the heart, this artery merges (anastomoses) with the anterior interventricular artery (LAD)
posterior interventricular artery
otherwise known as the posterior inferior descending artery
- runs toward the left side of the heart
- branches into the anterior interventricular artery (LAD) and circumflex artery
left coronary artery
- known clinically as the left anterior descending artery
- follows the anterior interventricular sulcus and supplies blood to the interventricular septum and anterior walls of both ventricles
anterior interventricular artery
supplies the left atrium and the posterior wals of the left ventricle
circumflex artery
which ventricle generates more pressure
left ventricle
the functional blood supply of the heart and the shortest circulation in the body
coronary circulation
- located at each atrial-ventricular junction
- prevent backflow into the atria when the ventricles contract
atrioventricular (AV) valves
- attached to each AV flap
- tiny white collagen chords that anchor the cusps to the papillary muscles protruding from the ventricular walls
- also known as the heart strings
chordae tendineae
act as tethers that anchor the valve flaps in their closed position
chordae tendineae and papillary muscles
- guard the bases of the large arteries issuing from the ventricles and prevent backflow into the associated ventricles
- crescent moon cusp shaped
aortic and pulmonary semilunar (SL) valves
- arise from the base of the aorta and encircle the ehart in the coronary sulcus
- provide arterial supply of coronary circulation
left and right coronary arteries
the act of listening to the heart with a stethoscope
auscultating
what is happening during the “pause” phase when the heart is resting/relaxing?
the ventricles are filling
what causes the abnormal swishing or whooshing sound that is heard as blood regurgitates back into an atrium from its associated ventricle
blood turbulence
which chamber of the heart has the highest probability of being the site of a myocardial infarction (MI)
left ventricle
the presence of an incompetent tricuspid valve would have the direct effect of causing
reduced efficiency in the delivery of blood to the lungs
The tricuspid valve separates the right atrium and the right ventricle. It must remain tightly closed during ventricular contraction so blood can be pumped out of the ventricle and into the pulmonary arteries.
if the mitral valve is unable to close properly,
blood could flow back into the left atrium
Failure in a particular structure of the heart tends to cause a backup of blood in the lungs, known as pulmonary congestive heart failure. Failure of which structure of the heart would lead to such a backup?
left ventricle
Failure in the left ventricle can cause increased blood hydrostatic pressure in the lungs, causing fluid buildup in the alveoli.
the left ventricular wall of the heart is thicker than the right wall in order to
pump blood w/ greater pressure
the source of blood carried to the capillaries in the myocardium
coronary arteries
what separates the parietal and visceral pericardium
pericardial cavity
excessive amount of fluid in the pericardial cavity
prevents the heart from filling properly with blood
true or false:
the left side of the heart pumps the same volume of blood as the right
true
lines the internal surface of the fibrous pericardium
parietal pericardium
true or false:
the role of the chordae tendineae is to open the AV valves at the appropriate time
false
Chordae tendineae anchor the cusps of the AV valves to the papillary muscles protruding from the ventricular walls. The chordae tendineae and the papillary muscles act as tethers that anchor the valve cusps in their closed position. If the cusps were not anchored, they would be blown upward (everted) into the atria, in the same way an umbrella is blown inside out by a gusty wind. The papillary muscles contract with the other ventricular musculature so that they take up the slack on the chordae tendineae as the full force of ventricular contraction hurls the blood against the AV valve cusps.
heart sounds are caused by
heart valve closure
what receives blood during ventricular systole
both the aorta and pulmonary trunk
the AV valves are closed when
the ventricles are in systole
during the period of ventricular filling,
blood flows mostly passively from the atria through the atrioventricular (AV) valves into the ventricles
what BP is necessary to force blood through vessels and effect cellular exchange of gases, wastes, and nutrients
120/80
what is responsible for the Lub sound
closure of the AV valves
what is responsible for the Dup sounds
closure of the semilunar valves
what does the QRS wave of the ECG represent
ventricular depolarization
cardiac temponade results in ineffective pumping of blood by the heart; because the excessive amount of fluid in the pericardial cavity will
prevent the heart from filling properly with blood
why are gap junctions a vital part of the intercellular connection of cardiac muscles?
gap junctions allow action potentials to spread to connected cells
Gap junctions are a form of electrical synapse that allow action potentials to spread to connected cells. This property allows the signal to spread efficiently through the heart.
pathway of the stimulation through the heart
- AV node
- AV bundle
- interventricular septum
- subendocardial conducting network
Suppose a patient develops a myocardial infarction that disables the sinoatrial node. Would the heart still pump blood to the aorta and the pulmonary trunk?
Yes, because the atrioventricular node will still stimulate ventricular systole.
The atrioventricular node spontaneously depolarizes similarly to the sinoatrial node, but more slowly. It can lead to the ventricles pumping blood to the aorta and pulmonary trunk around 50 times per minute.
Which portion of the electrocardiogram represents the wave-like change in charge in the positive direction received by the atria from the sinoatrial (SA) node?
p wave
The P wave represents the depolarization of the left and right atria and the beginning of atrial systole
Which portion of the ECG cycle overlaps with the expected ventricular contraction (or systole)?
Q-T interval
The Q-T interval is the period from the beginning of ventricular depolarization through ventricular repolarization, during which the ventricles are in systole.
The plateau phase of an action potential in cardiac muscle cells is due to the
influx of Ca2+ through slow Ca2+ channels
true or false:
an ECG provides direct information about valve function
false
at what point in the cardiac cycle is pressure in the ventricles the highest (around 120 mm Hg in the left ventricle)
ventricular systole
what causes heart sounds
heart valve closure
which part of the heart receives blood during ventricular systole
both the aorta and pulmonary trunk
the AV valves are closed when
the ventricles are in systole
refers to the short period during ventricular systole when the ventricles are completely closed chambers
isovolumetric contraction
As your skeletal muscles contract during physical activity, more blood is returned to the heart. Which variable would be affected and what would be the outcome of this action?
Preload would be increased, which would result in a larger cardiac output.
More blood returning to the heart would increase the volume of blood in the ventricles at the end of their filling phase (called end diastolic volume, or EDV). A larger EDV results in greater stretching of the myocardium, or a greater preload. Stretching (lengthening) the contractile cells brings them closer to their optimal length, allowing them to produce more force when stimulated to contract. The stronger contraction results in a larger stroke volume, and therefore a larger cardiac output.
true or false:
increasing end-diastolic volume (EDV) and end-systolic volume (ESV) will increase stroke volume
false
Stroke volume (the volume of blood ejected from the ventricle during systole) is equal to the difference between EDV (the volume of blood in the ventricle before it contracts) and ESV (the volume of blood remaining in the ventricle after it contracts). Increasing EDV will result in a larger stroke volume; however, increasing ESV will result in a smaller stroke volume.
hypercalcemia could cause
prolonged T wave
The T wave on an ECG tracing represents ventricular repolarization. Repolarization requires the net efflux of K+ ions. Recall that changes in normal concentrations of ions (like Ca2+) in the plasma can affect the ability of other ions to move in and out of the cell.
which cranial nerve carries efferent parasympathetic motor impulses to the heart and other major organs
vagus nerve
which part of the intrinsic conduction system is slowed by impulses from the vagus nerve
SA node
Which term describes an area of the heart conduction system where the impulse is delayed for 0.1 sec?
AV node
Which of the following factors gives the myocardium its high resistance to fatigue?
Large number of mitochondria in the cytoplasm
the cells of the myocardium behave as a single, coordinated unit called a
functional syncytium
the role of the atrioventricular node (AV node) is to
slow down impulses so that atria can contract to fill the adjacent ventricles with blood
the absolute refractory period refers to the time during which
the muscle cell is not in a position to respond to a stimulus of any strength
ventricular repolarization is indicated by which wave
T wave
the ability of some cardiac muscle cells to initiate their own depolarization and cause depolarization of the rest of the haert is called
automaticity
another term for contraction
systole
the area of the heart conduction system with the fastest depolarizing pacemaker cells
SA node
which wave signifies atrial depolarization
P wave
what is a difference between cardiac muscle and skeletal muscle
unlike skeletal muscle cells, cardiac muscle has gap junctions between cells that allow them to be autorhythmic
carries parasympathetic fibers to the sinoatrial (SA) node
vagus nerve (X)
signifies ventricular depolarization
QRS complex
sequence of current flow through the intrinsic conduction system of the heart
- SA node
- AV node
- AV bundle
- right and left bundle branches
- subendocardial conducting network
the P wave of an ECG represents
atrial depolarization
Given an end diastolic volume (EDV) of 120 ml / beat and an end systolic volume (ESV) of 50 ml / beat, the stroke volume (SV) would be
70 ml / beat
true or false:
if blood volume decreased dramatically due to massive bleeding, the autonomic nervous system will attempt to maintain cardiac output by increasing the heart rate.
true
true or false:
when released in large quanities, thyroxine, a thyroid gland hormone, causes a sustained increase in heart rate
true
striated and uninuclear; short, and branched
cardiac muscle cells
- connects cardiac muscle cells
- special anchors that hold the cells together and allow them to communicate via gap junctions
intercalated discs
opening of fast sodium channels
rapid depolarization
plateau phase is when slow calcium channels open and prevent rapid repolarization
rapid partial repolarization
calcium channels shut and membrane is again most responsive to potassium
repolarization
steps to action potential generation in cardiac muscles
- rapid depolarization
- partial repolarization
- repolarization
how long does it take for skeletal muscles to generate an action potential
2 milliseconds
how long does it take for cardiac muscle to generate an action potential
300-500 milliseconds
why is the refractory period of cardiac muscle action potential so prolonged
so that fatigue doesn’t set in when the cardiac muscle beats
which hormones increase heart rate
- epinephrine
- norepinephrine
- thyroid hormone
what effect does parasympathetic innervation have on heart rate and cardiac output?
decreased heart rate and lower cardiac output
what effect does sympathetic innervation have on heart rate and cardiac output
increases heart rate and cardiac output, along with increased contractility
the degree of stretch in cardiac muscle fibers before they contract
preload
end diastolic volume - end systolic volume
stroke volume
cardiac output =
stroke volume x heart rate
increasing the stretch in the ventricles by increasing what will increase stroke volume
increasing venous return
nerves run to the heart muscle and to the SA and AV nodes to accelerate the heart
sympathetic innervation of the heart
travels to the heart mainly via the vagus nerve and impacts the SA and AV nodes
parasympathetic innervation of the heart
what prevents rapid depolarization
slow Ca2+ channels
what occurs before contraction
depolarization
which part of the intrinsic conduction system depolarizes the fastest
SA node
what ions are the main effectors of cardiac output
- calcium
- sodium
- potassium
if stroke volume increases and heart rate stays the same, then what happens to cardiac output?
cardiac output increases
the amount of blood pumped out by each ventricle per minute
cardiac output
sounds heard in the 2nd intercostal space at the right sternal margin
aortic valve
sounds heard in the 2nd intercostal space at the left sternal margin
pulmonary valve
sounds heard over heart apex (in 5th intercostal space) in line with the middle of the clavicle
mitral valve
sounds typically heard in right sternal margin of 5th intercostal space
tricuspid valve
diagram that ties electrical and mechanical events together
Wigger’s diagram
steps to the cardiac cycle
- ventricular filling (ventricular filling and atrial contraction)
- ventricular systole (isovolumentric contraction –> ventricular ejection)
- early diastole (isovolumetric relaxation)
measures the electrical activity in the heart
electrocardiography
atrial depolarization initiated by the SA node causes this wave
P wave
atrial depolarization is complete and the impulse is delayed at the AV node
PQ interval
- ventricular depolarization begins at apex, causing this wave
- atrial repolarization occurs
QRS complex
ventricular depolarization is complete
ST interval
ventricular repolarization begins at the apex, causing this wave
T wave
- SA node nonfuncitonal
- P waves are absent
- heart is paced by AV node at 40-60bpm
junctional rhythm
- some P waves are not conducted through the AV node
- more P than QRS waves seen
- ratio of P waves to QRS waves is mostly 2:1
second degree heart block
- the volume of blood pumped out by one ventricle with each beat
- correlates with the force of ventricular contraction
stroke volume
- the difference between resting and maximal CO
- in nonathletes is typically 20-25 L/min
cardiac reserve
the degree to which cardiac muscle cells are stretched just before they contract
preload
the higher the preload,
the higher the stroke volum
- the relationship between preload and stroke volume
- higher preload = higher stroke volume
Frank-Starling
- most important factor stretching cardiac muscle
- the amount of blood returning to the heart and distending its ventricles
venous return
resting fetal heart rate
140-160bpm
avg female resting heart rate
72-80bpm
male resting heart rate
64-72 bpm
- raises HR by acting through the sympathetic nervous system
- increases systemic blood pressure and routes more blood to working muscles
exercise
what happens when the right side of the heart fails
peripheral congestion
blood stagnates in body organs, and pooled fluids in the tissue spaces impair the ability of body cells to obtain adequate nutrients and oxygen and rid themselves of waste
edema in extremities
what are common treatments for damaged heart muscle
- removing excess leaked fluid w/ diuretics
- reducing afterload with drugs that drive down bp
- increasing contractility w/ digitalis derivatives
- heart transplants and other surgical remedies
- when the left side of the heart fails
- right side of the heart continues to propel blood to the lungs but the left side doesn’t adequately eject the returning blood into systemic circulation
causes pulmonary edema due to engorged vessels w/ increased bp, and fluid leaks from vessels into lung tissue
pulmonary congestion
- ventricles stretch and become flabby and the myocardium deteriorates, often for unknown reasons
- drug toxicity and chronic inflammation may be involved
dilated cardiomyopathy (DCM)
- a succession of myocardial infarctions (heart attacks) depresses pumping efficiency because noncontractile fibrous (scar) tissue replaces the dead heart cells
multiple myocardial infarctions
- fatty buildup that clogs the coronary arteries, impairs blood and oxygen delivery to cardiac cells
- heart becomes increasingly hypoxic and begins to contract ineffectively
coronary athersclerosis
- the heart is such an inefficient pump that blood circulation is inadequate to meet tissue needs
- a progressively worsening disorder that reflects the weakening of the myocardium by various conditions that damage it in different ways
- common causes include: coronary atherosclerosis, persistent high bp. multiple MIs, dilated cardiomyopathy (DCM)
congestive heart failure (CHF)
- an abnormally fast resting heart rate (>100 bpm) that may result from elevated body temp, stress, certain drugs, or heart disease
- if persistent, considered pathological because it occasionally promotes fibrillation
tachycardia
- a resting heart rate slower than 60bpm
- may result from low body temperature, certain drugs, or parasympathetic NS activation
- often a warning of brain edema after head trauma
bradycardia
increases HR by enhancing the metabolic rate of cardiac cells
heat
- an autonomic reflex initiated by increased venous return and increased atrial filling
- stretching the atrial walls increases heart rate by stimulating both the SA node and the atrial stretch receptors, triggering reflexive adjustments of autonomic output to the SA node, increasing HR
atrial (Bainbridge) reflex
factors that increase heart rate
positive chronotropic factors
factors that decrease heart rate
negative chronotropic factors
exerts the most important extrinsic controls affecting heart rate
ANS
in what condition is afterload particularly important and why
hypertension; reduces ability of the ventricles to eject blood
- the pressure that ventricles must overcome to eject blood
- essentially the back pressure that arterial blood exerts on the aortic and pulmonary valves (~80 mmHg in the aorta and 10 mmHg in the pulmonary trunk)
afterload
the major intrinsic factor influencing stroke volume
end diastolic volume
- the contractile strength achieved at a given muscle length
- rises more when more Ca2+ enters the cytoplasm from the extracellular fluid and the SR
contractility
what is the effect of enhanced contractility
more blood is ejected from the heart (greater SV) and lower ESV
- substances that increase contractility
- epinephrine, thyroxine, glucagon, the drug digitalis, high levels of extracellular Ca2+
positive inotropic agents
- impair or decrease contractility
- induce acidosis
- include rising EC K+ levels and also calcium channel blockers
negative inotropic agents
