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103 Cards in this Set

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Starling's law of the heart
The more the myocardium is stretched (up to a certain point) the more forceful the subsequent contraction will be.
resting membrane potential
The electrical charge difference inside a cell membrane measured relative to just outside the cell membrane.
threshold potential
The value of the membrane potential at which an action potential is produced as a result of depolarization in response to a stimulus.
refractory period
The period after effective stimulation during which excitable tissue fails to respond to a stimulus of threshold intensity.
premature atrial complex
A cardiac dysrhythmia characterized by an atrial beat occurring before the expected excitation and indicated on the electrocardiogram as an early P wave.
premature junctional contraction
A cardiac dysrhythmia that occurs during sinus rhythm earlier than the next expected sinus beat and is caused by premature discharge of an ectopic focus in the atrioventricular junctional tissue.
premature ventricular complex
A cardiac dysrhythmia characterized by a ventricular beat preceding the expected electrical impulse and indicated on the electrocardiogram as an early, wide QRS complex without a preceding related P wave.
ventricular tachycardia
A tachycardia that usually originates in the Purkinje fibers.
paroxysmal supraventricular tachycardia
An ectopic rhythm in excess of 100 beats per minute and usually faster than 170 beats per minute that begins abruptly with a premature atrial of junctional beat and is suported by an atrioventricular nodal reentry mechanism or by an atrioventricular reentry involving an accessory pathway.
apex
The lower heart border.
point of maximal impulse (PMI)
The physical examination landmark that is an indicator of the heart's position within the thorax.
fibrous pericardium
The outer, tough, inelastic sac.
serous pericardium
The inner, thin, two-layered, fluid-secreting membrane.
epicardium
The visceral layer of the serous pericardium.
myocardium
The thick, middle, muscular layer that makes up the bulk of the heart wall.
endocardium
The smooth, thin layer of tissue that lines the heart chambers and valves.
systemic circuit
A large circuit; involves the left side of the heart and vessels, which carry blood to the body and back to the right heart.
pulmonary circuit
A small circuit; includes the right side of the heart and vessels, which carry blood to the lungs and back to the heart.
interatrial septum
The wall that divides the two upper chambers.
interventricular septum
The thicker wall that divides the two lower chambers.
tricuspid valve
Separates the right atrium from the right ventricle.
pulmonic valve
Separates the right ventricle from the pulmonary arteries.
mitral valve
Separates the left atrium from the left ventricle.
aortic valve
Separates the left ventricle from the aorta.
atrioventricular (AV) valves
The tricuspid and mitral valves.
chordae tendineae
Thin strands of fibrous cords ("heart strings").
semilunar valves
The aortic and pulmonic valves.
collateral vessels/ collateral circulation
Small arteries that interconnect the right and left coronary artery branches.
sympathetic nervous system
Prepares the body to function under stress.
parasympathetic nervous system
Regulates the calmer functions.
myocardial cells
Working or mechanical cells.
actin and myosin
Contractile protein filaments.
electrolyte
A substance whose molecules dissociate into charged particles (ions) when placed in water, producing positively and negatively charges ions.
cation
An ion with a positive charge.
anion
An ion with a negative charge.
membrane channels (pores)
Openings through which ions pass back and forth between the extracellular and intracellular spaces.
concentration gradient
Particles in a solution move from areas of higher concentration to areas of lower concentration.
electrical gradient
Like charges repel; opposite charges attract.
sodium-potassium pump
A mechanism that actively transports ions across the cell membrane against its electrochemical gradient.
right bundle branch
Conducts the electrical impulse to the right ventricle.
left bundle branch
Divides into two divisions: the anterior fascicle and the posterior fascicle.
anterior fascicle
Carries the electrical impulse to the anterior wall of the left ventricle.
posterior fascicle
Carries the electrical impulse to the posterior wall of the left ventricle.
Purkinje fibers
Conduction fibers.
His-Purkinje system
The bundle of His, bundle branches, and Purkinje fibers.
P wave
Depicts atrial depolarization, or the spread of the impulse from the SA node throughout the atria.
PR interval
Represents the time from the onset of atrial depolarization to the onset of ventricular depolarization.
PR segment
The short isoelectric line from the end of the P wave to the beginning of the QRS complex.
QRS complex
Depicts ventricular depolarization, or the spread of the impulse throughout the ventricles.
ST segment
Represents the end of ventricular depolarization and the beginning of ventricular repolarization.
T wave
Represents the latter phase of ventricular repolarization.
U wave
Is thought to represent further repolarization of the ventricles.
QT interval
Represents both ventricular depolarization and repolarization.
R-R interval
From one R wave to the next R wave.
biphasic deflection
A deflection having both a positive and negative component.
absolute refractory period
During this period the cells absolutely can't respond to a stimulus.
relative refractory period/ vulnerable period of repolarization
During this perios the cardiac cells have repolarized sufficiently to respond to a strong stimulus.
supernormal period
During this period the cardiac cells will respond to a weaker than normal stimulus
The heart has three tissue layers. What are they?
1. Endocardium
2. Myocardium
3. Pericardium
a. Visceral pericardium (epicardium)
b. Parietal pericardium
What are the 4 chambers?
Right atrium, right venticle, left atrium, left ventricle.
Two semilunar valves:
Pulmonary valve- between the right ventricle and the pulmonary trunk
Aortic valve- between the left ventricle and the aorta
Two atrioventricular valves:
Tricuspid valve- between the right atrium and ventricle
Mitral valve- between the left atrium and ventricle
aorta
pulmonary circulation
vena cava
left ventricle
systemic circulation
right atrium
left atrium
righ ventricle
vena cava, right atrium, right ventricle, pulmonary circulation, left atrium, left ventricle, aorta, systemic circulation
How does the heart receive its nutrients from the blood? Is it during systole or diastole?
Blood drains into the coronary arteries during diastole.
What are the three layers of the wall of an artery?
Tunica intima, tunica media, tunica adventia.
cardiac cycle
From the end of one contraction to the next.
diastole
When the myocardium is relaxed and cardiac filling and coronary perfusion occurs.
systole
When the myocardium is contracting.
ejection fraction (What is normal?)
Ratio of the amount of blood pumped from the ventricles to the amount remaining at the end of diastole.
(2/3 is the normal ejection fraction)
stroke volume
The amount of blood ejected by the heart in one contraction.
cardiac output
The volume of blood the heart pumps in 1 minute.
preload
The pressure within the ventricles at the end of diastole; commonly called the end-diastolic volume.
afterload
The resistance against which the heart must pump.
cardiac output = stroke volume x
heart rate
cardiac output x systemic vascular resistance =
blood pressure
What 2 components of the autonomic nervous system regulate the heart?
Parasympathetic system, sympathetic system.
Sympathetic system neurotransmitter?
Norepinephrine.
2 principal types of sympathetic system receptors?
Alpha and beta.
Where are the alpha receptors located? What do they cause?
In the peripheral vessels; vasoconstriction.
There are 2 types of beta receptors- beta 1 and beta 2. Where are they located? What do they cause?
Beta 1 receptors in the heart cause an increase in rate and contractility.
Beta 2 receptors in the lungs cause bronchodilation.
Parasysmpathetic system neurotransmitter?
Acetylcholine.
In the heart, parasympathetic system controlled by the _____ nerve?
vagus
chronotropy
Pertaining to heart rate.
inotropy
Pertaining to cardiac contractile force.
dromotropy
Pertaining to the speed of impulse transmission.
What are the 3 electrolytes that most affect cardiac function?
Na+
K+
Ca++
intercalated discs
Specialized bands of tissue inserted between the myocardial cells that increase the rate at which the action potential is spread from cell to cell.
syncytium
A group of cardiac muscle cells that physiologically function as a unit.
The heart has 2 syncytia...
Atrial syncytium, ventricular syncytium.
The only way the impulse can be conducted is through the ________________ node.
atrioventricular
resting potential
The normal resting state of cardiac cells.
cardiac depolarization
Quick reversal of the resting potential caused by a rapid influx of Na+ into the cell.
action potential
An influx of positive ions into the cell followed by a change of polarity.
repolarization
Return of a muscle cell to its preexcitation resting state.
excitability
The ability of the cells to respond to an impulse.
automaticity
The ability of a cell to spontaneously generate and discharge an impulse.
conductivity
The ability of a cell to transmit an impulse.
contractility
The ability of the cell to shorten and lengthen muscle fibers.
pacemaker cells
Cells that spontaneously depolarize.
normal P wave
Upright, slightly rounded, smooth.
normal PR interval
0.12-0.20 seconds (3-5 small boxes).
normal QRS
Less than 0.12 seconds (less than 3 boxes).
normal T wave
Rounded and upright, usually taller and wider than the P wave.