 | Term | Definition |
| |
cardiology |
scientific study of the heart and treatment of its disorders |
| |
cardiovascular system |
consists of the heart and the blood vessels that carry the blood to and from the body's organs. two major sytems include the pulmonary and systemic circuit. |
| |
pulmonary circuit |
carries blood to the lungs for gas exchange and returns it to the heart |
| |
systemic circuit |
supplies blood to every organ of the lungs and the wall of the heart itself |
| |
pericardium |
a double-walled sac that encloses the heart |
| |
parietal pericardium |
the outer, tough, superficial fibrous layer of dense irregular connective tissue and a deep, thin serous layer. |
| |
visceral pericardium |
covering of the heart surface that is anchored by ligaments to the diaphrogm below and the sternum anterior to it |
| |
pericardial cavity |
the space betwen the visceral and parietal membranes, and contains pericardial fluid |
| |
pericardial fluid |
found in the pericardial cavity, exuded by the serous pericardium, lubricates the membranes and allows the heart to beat almost without friction; isolates the heart from other organs, allows the heart room to expand and yet prevents excessive expansion |
| |
epicardium |
a serous membrane on the surface of the heart |
| |
endocardium |
layer of tissue that lines the interior of the heart chambers |
| |
myocardium |
layer of tissue of the heart that is composed of cardiac muscle, the thickest layer, and performs the work of the heart |
| |
fibrous skeleton |
meshwork of collagenous and elastic fibers, concentrated in the walls between the heart chambers, in fibrous rings around the openings of the heart valves, and in sheets of tissues that interconnect these rings. This functions as: structural support for the heart, an anchor for the myocyte and gives something to pull against, an electrical insulation between the atria and the ventricles, the elastic recoil aids in the refilling after each beat |
| |
pectinate muscles |
internal ridges of myocardium |
| |
trabculae carneae |
intenal ridges in both ventricles |
| |
atrioventricular valves |
regulate the openings between the atria and the ventricles. right is the tricuspid, and left is the bicuspid |
| |
chordae tendineae |
tendonous cords that conncect the valve cusps to conical papillary muscles on the floor of the ventricles |
| |
semiulnar valves |
rgulate the flow of blood from the ventricles into the great arteries. the pulmonary and aortic valves |
| |
coronary circulation |
blood vessels of the heart wall constitute this system. provides blood to the myocarium and all of its muscle cells. approximately 5% of the circulating blood goes to meet the metabolic needs of the heart |
| |
left coronary artery |
travels through the coronary sulcus and under the left auricle where it divides two branches...one of which is the cirfumflex branch which gives rise to the marginal artery |
| |
right coronary artery |
supplies the right atrium and the sinoatrial node. gives off two branches...one of which is the posterior interventicular branch |
| |
myocardial infarction |
aka heart attack, caused by a fatty deposit or blood clot in a coronary artery |
| |
anastomoses |
points where two arteries come together and combine their blood to points where two arteries come together and combine their blood flow to points farther downstream |
| |
collateral circulation |
provided by anastomoses, an alternate route that can supply the tissue with blood if the primary route becomes obstructed |
| |
venous drainage |
route which blood leaves an organ |
| |
cardiac nerves |
sympathetic nerves that arise from the cervical ganglia and lead to the venticular myocardium. the parasympathetic pathway to the hear is through the vagus nerves. The ventricles receive little or no vagal stimulation, the vagus nerve is what slows the heartbeat. These sympathetic and parasympathetic nerves are not what make it bear; the heart beat is set off by the heart's internal pacemaker and is simply modified by these nerves |
| |
vagal tone |
the steady background firing of the vagus nerves |
| |
autorhythmic |
label of cardiac myocytes because they are able to depolarize spontaneously at regular time intervals |
| |
cardiac conduction |
cells that control the route and timing of electrical conduction to ensure that the four chambers are coordinated with each other |
| |
sinoatrial node |
a patch of modified monocytes in the right atrium, under the epicardium near the superior vena cava, this is the pacemaker that initiates each heartbeat and determines the heart rate. the signals spread throughout the atria |
| |
atrioventricular mode |
node, located near the right AV valve at the lower end of the interarterial septum, which acts as an electrical gateway to the ventricals. The fibrous skeleton acts as an insulator to prevent currents from getting to the ventricles by another route |
| |
bundle of His |
aka the atrioventricular (AV) bundle, a pathway by which signals leave the AV node |
| |
Right and Left bundle branches |
after the fork in the AV bundle, these enter the interventricular septum and descend toward the apex |
| |
Purkinje fibers |
nervelike processes that arise from the lower end of the bundle branches and turn upward to spread throughout the ventricular myocardium. THey distribute the electrical excitation to the myocytes of the ventricles; they form an elaborate network in the left ventricle than in the right |
| |
intercalated discs |
thick connections that join the myocytes end to end. three distinctive features: interdigitating folds, mechanical junctions (fascia adherens and desmosomes), and gap junctions |
| |
myoglobin |
a short-term source of stored oxygen for aerobic respiration, very rich in the cardiac cells for aerobic respiration |
| |
glycogen |
a stored energy source, found in cardiac muscle for aerobic respiration |
| |
systole |
contraction in the cardiac cycle |
| |
diastole |
relaxation in the cardiac cycle` |
| |
sinus rhythm |
the name of the normal heart beat, triggered by the SA node |
| |
premature ventricular contraction |
aka extrasystole, stimuli can cause other parts of the conduction system to fire before the SA node does, setting off an extra heart beat |
| |
ectopic focus |
any region of spontaneous firing other than the SA node. If the SA node is damaged, this may take over the governance of the heart rhythm. Most common is the AV node |
| |
nodal rhythm |
the slower heartbeat of about 40-50 bpm by the AV node, which is sufficient to sustain life. other ectopic foci fire at rates of about 20-40 bpm but this is too little blood flow to the brain to be able to sustain life |
| |
arrhythmia |
any abnormal cardiac rhythm |
| |
heart block |
failure of any part of the cardiac conduction system to transmit signals, usually as a result of disease and degeneration of conduction system fibers. examples include: bundle branch block-due to damage of one/both bundle fibers, total heart block- damage to the AV node, the atria fail to reach the ventricles and the ventricles beat their own intrinsic rhythm |
| |
pacemaker potential |
the SA node's unstable resting membrane potential starts at about -60mV and drifts upward, showing a gradual depolarization as a result of a slow inflow of Na+ without compensating outflow of K+ |
| |
fast calcium channels |
when the pacemaker potential reaches a threshold of -40mV, these channels open and Ca2+ flows in from the ECF. this produces a rising (depolorizing) phase of the action potential which peaks slightly above 0mV. this causes the K+ channels to open and the K+ leaves the cell. which makes the cytosol increasingly negative and creates a falling (repolorizing) phase of the action potential. When the repolarization is complete, the K+ channels close and the pacemaker potential starts over. each depolorization of the SA node sets off one heartbeat |
| |
electrocardiogram |
a composit recording of all the action potentials produced by the nodl and myocardial cells. a moving paper chart that records the simultaneous recordings made from electrodes at different distances from the heart. it provides a comprehensive image of the heart's electrical activity. |
| |
P wave |
produced when a signal from the SA node spreads through the atria and depolarizes them. atrial systole begins about 100 msec after the p wave begins |
| |
QRS complex |
consists of a small downward deflection, followed by a tall, sharp peak, and a final downward deflection. This is the result of the signal as it spreads from the AV node through the ventricular myocardium. the shape is due to the complex shape of the ventricles and the different times required for them to depolarize. ventricular systole begins soon after this segment. Atrial repolarization and diastole also occur during this interval. |
| |
T wave |
generated by ventricular repolorization immediately before diastole. ventricles take longer to repolorize than to depolorize, therefore this wave is more spread out than the QRS complex and has a rounded peak. |
