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75 Cards in this Set
- Front
- Back
Which cardiac muscle has a longer refractory period?
How long is it? |
Ventricular muscle
0.25 to 0.3 sec. |
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What is responsible for preventing the heart from undergoing reentry, which would not allow the heart to relax and refill with blood?
What does this keep the muscle from undergoing? |
Long refractory period or Absolute refractory period
Tetanus |
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What increases the strength of cardiac contractions?
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Increase in extracellular Ca++
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What is the time required for the excitation to spread throughout the heart?
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0.22 sec.
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What period occurs when another action potential cannot be elicited, no matter how large the stimulus?
What determines this period? |
Absolute Refractory Period
Duration of sodium inactivation gate closure |
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What period begins at the end of the absolute refractory period and continues until the membrane potential returns to the resting level? A second action potential is possible only if the stimulus is larger than usual.
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Relative refractory period.
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What valve is located between the right atrium and right ventricle, surrounding the AV orifice?
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Tricuspid valve
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What valve is located between the left atrium and left ventricle, surrounding the AV orifice, and is the only valve to have a different number of cusps than the others?
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Mitral valve
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What opens the tricuspid and mitral valves?
What closes them? |
Ventricular diastole
Forced shut as pressure in ventricles increases |
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What valves are opened during ventricular systole?
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Pulmonary semilunar valve
Aortic semilunar valve |
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The T wave of an electrocardiogram wave segment represents the _____ of the _____.
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Repolarization
Ventricles |
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What is the test that measures the electrical activity of the heart?
What is the natural pacemaker of the heart? |
Electrocardiogram (ECG or EKG)
Sinoatrial node |
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What are the principal ECG intervals represented by?
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P waves
QRS waves T waves |
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What is the electrical recording from the body surface of atrial depolarization and precedes atrial contraction?
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P wave
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What wave represents ventricular depolarization?
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QRS complex
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What represents closure of the AV valves at the onset of systole?
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First heart sound
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What represents closure of the semilunar valves at the onset of diastole?
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Second heart sound
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What does it mean if an ECG shows extra P waves before each QRS complex?
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Partial heart block
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What does it mean if an ECG shows the P wave and the QRS complex being dissociated?
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Complete heart block
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Cardiac function is the volume of blood pumped each minute, and is expressed by what equation?
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CO=SV x HR
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What is perhaps the single most important factor that is used in relation to the circulation and is responsible for transport of substances to and from the tissues?
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Cardiac output (CO)
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what is the avg. resting CO?
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5.6 L/min. - Men
about 10-20% less in women |
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What is directly proportional to cardiac output, and is an intrinsic factor of the SA node in the heart and is modified by _____, _____, and _____ factors?
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Heart Rate (HR)
autonomic humoral local |
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What is determined by three factors; preload, afterload, and contractility?
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Stroke Volume (SV)
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What is normal avg. human heart rate?
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80-100 beats per minute
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What gives the volume of blood that the ventricle has available to pump, as well as the end diastolic length of the muscle?
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Preload
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What is the force that the muscle can create at the given length?
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Contractility
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What is the arterial pressure against which the muscle will contract?
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Afterload
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What is the equation for stroke volume?
What is the avg.? |
SV = End diastolic volume - End Systolic volume
70-80ml |
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What is the sum of the resistance of all peripheral vasculature in the systemic circulation?
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Total peripheral volume (TPR)
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What is the equation for blood pressure?
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BP = CO x TPR
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The bainbrain reflex also called the _____ reflex, is an increase in heart rate due to an increase in the blood volume.
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Atrial
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The bainbridge reflex increases HR and CO, which then transfers blood volume where? to where?
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From pulmonary circulation to systemic circulation
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What is the dominant cardiovascular mechanism responsible for the control of blood pressure?
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Baroreceptor reflex
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What nerves transmit signals from the stretch receptors in the carotid sinus and aortic arch to the solitary nucleus located in the cardiovascular center of the medulla?
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Glossopharyngeal and Vagus nerves
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How long does a cardiac cycle last?
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0.8 seconds
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In the _____ phase, the heart ventricles are relaxed, and the heart fills with blood.
In the _____ phase, the ventricles contract and pump blood into the arteries |
Diastole
Systole |
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Blood flow to the coronary arteries would be greatest during _____ _____ in a resting individual.
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Ventricular relaxation
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Ventricular volume is _____ following atrial systole.
Ventricular pressure is _____ during ventricular ejection. |
Greatest
Greatest |
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The first heart sound or _____ is associated with the closure of the _____ valves at the beginning of ventricular contraction.
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Lub
Atrioventricular (mitral and tricuspid) |
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Which sound is louder and longer?
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First heart sound
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The second heart sound or _____ is associated with the closure of the _____ valves as the ventricles begin to relax following their contraction.
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Dub
Semilunar valves (pulmonary and aortic) |
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_____ begins with the second heart sound
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Diastole
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The aortic valve closes _____ the pulmonary valve; this causes _____ of the second heart sound.
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Before
Splitting |
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What arises from the fact that cardiac myocytes are electrically coupled to one another via gap junctions?
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Cardiac conduction system
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What is located within the posterior wall of the right atrium near the opening of the superior vena cava, and contains specialized pacemaker cells that depolarize at an intrinsic rate that drives the depolarization of the remainder of the heart?
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SA (sinoatrial node)
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What rapidly transmits the wave of depolarization to the left atrium and to the AV node?
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Internodal pathways
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What is located within the lower right interatrial septum, and delays an impulse for about _____ seconds to allow the atria to contract before ventricular contraction?
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AV (atrioventricular node)
0.13 |
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What originates in the AV node, dividing into two bundle branches that extend down the two sides of the interventricular septum?
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AV bundle (bundle of his)
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What originates from the right and left bundle branches, extending to the papillary muscles and lateral walls of the ventricles? The wave of depolarization hear is extremely fast.
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Purkinje fibers
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What represents atrial depolarization prior to the atria's contraction?
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P wave
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What represents ventricular repolarization?
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T wave
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What represents ventricular depolarization?
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QRS complex
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What represents the period when the ventricles are depolarized and is isoelectric?
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S-T segment
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What represents the length of time between depolarization of the atria and depolarization of the ventricles?
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P-R interval
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What represents the period between ventricular depolarization and the ventricles' repolarization?
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Q-T interval
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What is the most important determining factor for preload?
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Venous return
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Under steady state conditions, venous return must equal _____ when averaged over time because the cardiovascular system is essentially a closed loop.
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CO (cardiac output)
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Blood flow is directly proportional to the pressure difference between the two ends of the vessel but is inversely proportional to the fractional resistance to the blood flow through a vessel. This relationship can be expressed as:
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Flow = pressure difference / resistance
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Factors which influence resistance are expressed as:
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Resistance = viscosity (of blood) x length (of vessel) / radius^4
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The _____ the vessel the _____ resistance.
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Larger
Less |
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What are the factors that influence venous return?
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Skeletal muscle contraction
Decreased venous compliance Respiratory activity Vena cava compression |
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An increase in _____ activation decreases venous compliance and increases _____ ____.
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Sympathetic activation
Venous return |
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An increase in _____ _____ will decrease venous return.
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Intrathoracic pressure
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During exercise, the total peripheral resistance (TPR) is caused by the accumulation of what?
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Vasodilator Metabolites (lactate, potassium ions, adenosine)
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What accounts for the overal decrease of TPR?
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Arterial vasodilation
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When you have an anxious dental patient that may have a higher systolic blood pressure than previously noted, what is this most likely due to?
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Decreased arterial compliance
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What primarily controls Heart rate?
Where is the control of this system take place? |
ANS
Medulla oblongata |
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Parasympathetic fibers innervate the heart by way of the _____ nerves. The _____ _____ goes to the SA node and the _____ _____ goes to the AV node.
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Vagus
Right vagus Left vagus |
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Where do the sympathetic fibers of the heart which increases cardiac function come from?
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First four thoracic spinal nerves (accessory nerves)
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If a patient's SA and AV nodes fail, what is the most likely situation the patient will be in?
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Both atria and ventricles will continue to contract on the pace of the bundle of His (30-40 impulses)
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What makes up the AV junctional tissue?
Where is this considered to be located? What is its intrinsic rate or beats per minute? |
AV node and Bundle of His
Supraventricular 40-60 beats per minute |
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What are the three bundle branches of the Bundle of His?
What does this comprise? |
Rt.
Lt. anterior-superior Lt. posterior-inferior Trifascicular system |
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What are the fibers which conducta signal from the bundle of His to the ventricular muscles?
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Purkinje fibers
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what is the system of the Bundle branches and Purkinje fibers known as?
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Ventricular conduction system
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