Unit 3
Which of these structures conduct(s) action potentials the slowest?
AV node
The ________ is the regulation of blood flow by local mechanisms within a capillary bed.
Autoregulation
Why does tetany not occur in cardiac muscle?
Cardiac muscle has a long refractory period that continues until relaxation is well under way. As a result, another action potential cannot arrive quickly enough for summation to occur, and thus tetany cannot occur.
Which of the following can be heard with a stethoscope most easily?
Closing of atrioventricular valves
The beginning of the QRS complex of the electrocardiogram (ECG) immediately precedes which of the following events?
Closing of the atrioventricular valves The QRS complex is a recording of ventricular depolarization. This depolarization begins just prior to the ventricular contraction it initiates. As the ventricles contract, the increase in ventricular pressure closes the atrioventricular valves, beginning isovolumetric contraction. As ventricular pressure increases above the corresponding blood vessel, only then do the semilunar valves open, initiating ventricular ejection.
The ________ lines the chambers of the heart, covers the heart valves, and is continuous with the endothelium.
Endocardium
P-R interval
Period from start of atrial depolarization to start of ventricular depolarization
Which chamber receives blood from the superior and inferior vena cavae?
Right Atrium
Which part of the intrinsic conduction system normally initiates the depolarizing impulse that causes a heartbeat?
SA Node
The volume of blood ejected from each ventricle during a contraction is called the
Stroke Volume
Resting heart rate
Varies with age, general health, physical conditioning Normal range is 60-100 bpm
V fib
Ventricular fibrillation a chaotic quivering of the heart muscle, is the most common dysrhythmia that results in sudden cardiac arrest (SCA). In V-Fib, the heart is not beating effectively and is not pumping blood; therefore, the patient will not have a pulse.
V-tach
Ventricular tachycardia (an increased ventricular heart rate).
Cardiac arrhythmias
abnormal patterns of cardiac electrical activity About 5% of healthy people experience a few abnormal heartbeats each day
During a period of moderate exercise:
arterioles to the skeletal muscles dilate
coronary artery disease
atherosclerosis of the coronary arteries that reduces the blood supply to the heart muscle
P wave
atrial depolarization (contraction)
During the isovolumetric contraction phase of ventricular systole, the
atrioventricular valves and semilunar valves are closed.
cardiac regurgitation
backflow of blood due to imperfect closure of the heart valves
What do semilunar valves prevent?
backflow of blood into the ventricles
Which of the following is not associated with the right side of the heart?
bicuspid valve
Exchange between a blood vessel and the cells that surround it can occur only in
capillaries
Vessels that allow exchange of materials to occur between blood and surrounding tissues are the:
capillaries
One of two factors that determine mean arterial pressure is:
cardiac output
Why is ventricular fibrillation fatal?
causes the condition known as cardiac arrest fatal because the ventricles merely quiver and do not pump blood into the systemic circulation.
Blood flow through the coronary circuit is maintained by
changing blood pressure and elastic rebound
Atherosclerosis
condition in which fatty deposits called plaque build up on the inner walls of the arteries
An increase in sympathetic stimulation of the heart would increase stroke volume by increasing __________.
contractility
Venous return is aided by:
contraction of skeletal muscles one-way valves thoracic pressure ***All of the above***
valvular heart disease
disorders involving valves of the heart that impact the heart's ability to pump blood effectively to the lungs or tissues of the body and cause the heart to work harder
cardiac tampanade
excess accumulation of pericardial fluid - heart fills with fluid so it can't expand
True or False: The AV node serves as a "bridge" that transmits the depolarization wave from the ventricles to atria.
false because the AV node transmits signals from the atria to the ventricles
Purkinje fibers
fibers in the ventricles that transmit impulses to the right and left ventricles, causing them to contract
atrial fibrillation
rapid, random, ineffective contractions of the atrium
electrocardiogram
record of the electrical activity of the heart
isovolumetric contraction
refers to the short period during ventricular systole when the ventricles are completely closed chambers
cardiac skeleton
reinforces the myocardium internally and anchors the cardiac muscle fibers
Which heart chamber pumps unoxygenated blood out the pulmonary trunk?
right ventricle
The pressure within the large arteries of the systemic circulation:
rises if the cardiac output is increased
Mediastinum
space or region in thorax between the two pleural cavities (between the lungs)
As a result of the long refractory period in the cardiac action potential, cardiac muscle cannot exhibit
tetany
If the cells of the SA node failed to function, how would the heart rate be affected?
the heart would still continue to beat, but at a slower rate; the AV node would act as the pacemaker
Heart rate (HR)
the number of heart beats per minute
End Systolic Volume (ESV)
the volume of blood in one ventricle after contraction
End Diastolic Volume (EDV)
the volume of blood in one ventricle before contraction
Stroke Volume (SV)
the volume of blood per heart beat pumped out by one ventricle
Venous Return (VR)
the volume of blood per minute flowing into one atrium
Cardiac Output (CO)
the volume of blood per minute pumped out by one ventricle
The heart is actually (one, two, or three) pumps?
two pumps
Which of the following refers to a decrease in vessel diameter due to smooth muscle contraction?
vasoconstriction
The amount of blood returning to the heart is the
venous return
QRS complex
ventricular depolarization Larger wave due to larger ventricle muscle mass
phases of cardiac cycle
ventricular filling isovolumetric contraction ventricular ejection isovolumetric relaxation
T wave
ventricular repolarization
Heart Sounds: S3 and S4
very faint; rarely heard in adults S3—blood flowing into ventricles S4—atrial contraction
End Diastolic Volume (EDV)
volume of blood in each ventricle at end of ventricular diastole
End Systolic Volume (ESV)
volume of blood remaining in each ventricle after systole
heart sounds: S1 (Lubb)
when AV valves close; marks start of ventricular contraction
Heart Sounds: S2 (Dub)
when semilunar valves close
Cardiac Muscle vs Skeletal Muscle
Intercalated discs = branching interconnections between cells
the heart wall has 3 layers
pericardium, myocardium, endocardium
Damage to the semilunar valve on the right side of the heart would affect blood flow to which vessel?
pulmonary trunk
The difference between the systolic and diastolic pressures is called the ________ pressure.
pulse
when ventricles are relaxed
*Diastole* they fill AV valves are open Semilunar are closed
when ventricles are contracted
*systole* they empty AV valves are closed Semilunar are Open
Left coronary artery supplies
-Left Atrium -Left Ventricle -Interventricular septum
Components of conducting system:
-Sinoatrial node (SA node) action potential generated -Internodal pathways -Atrioventricular node (AV node) -AV bundle and bundle branches -Purkinje fibers
Right coronary artery supplies
-right atrium -most of the right ventricle -part of the left ventricle -the SA and AV nodes
Match the cardiac components in the left column to the blanks near their functions on the right.
1. AV node: Delay(s) occurs here while atria contract 2. SA node: Set(s) the pace for the entire heart 3. AV bundle : Electrical link(s) between atria and ventricles 4. Purkinje fibers: Convey(s) the impulse throughout the ventricular walls 5. Bundle branches: Convey(s) the impulse down the interventricular septum 6. Internodal pathways: Link(s) between the SA node and AV node
Tachycardia
Heart rate faster than normal (>100 bpm)
Bradycardia
Heart rate slower than normal (<60 bpm)
In cardiac muscle, the fast depolarization phase of the action potential is the result of ________ membrane permeability to ________ ions.
Increased; Sodium
internodal pathways
Interconnect the SA Node with the AV Node, conducts impulses through to the atrial working cells.
Pericardium
Membrane surrounding the heart
Premature atrial contractions (PACs)
Often occur in healthy people Normal atrial rhythm momentarily interrupted by "surprise" atrial contraction Increased incidences caused by stress, caffeine, various drugs that increase permeability of the SA pacemakers
Blood flowing into the heart from the venae cavae flows next through the ________ valve.
Tricuspid
Q-T interval
Time for ventricles to undergo a single cycle
heart failure
a chronic condition in which the heart is unable to pump out all of the blood that it receives
The force of contraction of the left ventricle is
greater than that of the right ventricle
arteriosclerosis
hardening of the arteries
Why is it important for impulses from the atria to be delayed at the AV node before they pass into the ventricles?
if the impulses from the atria were not delayed at the AV node, they would be conducted through the ventricles so quickly by the bundle branches and Purkinje cells that the ventricles would begin contracting immediately, before the atria had finished their contraction. As a result, the ventricles would not be as full of blood as they could be, and the pumping of the heart would not be as efficient, especially during activity.
Which of the following factors will not increase cardiac output?
increased parasympathetic stimulation.
pericarditis
inflammation of the pericardium
endocardium
innermost layer of the heart
Right and left atria are separated by the
interatrial septum
Right and left ventricles are separated by
interventricular septum (much thicker)
In which direction would fluid move between the interstitial fluid (fluid around cells) and the capillary at the venule end of the capillary?
into the capillaries
two phases of ventricular systole
isovolumetric contraction phase and ejection phase
Why can cardiac tamponade be a life-threatening condition?
it interferes with the performance of the heart that if left untreated results in dangerously low blood pressure, shock and death.
The purpose of a stent is to
keep an artery open
coronary ischemia
lack of blood flow to the heart muscle due to a blockage
Which heart chamber receives blood from the pulmonary veins?
left atrium
The pulmonary veins carry blood to the
left atrium of the heart
Which chamber pumps oxygenated blood out the aorta to the systemic circuit?
left ventricle
The space between the pleural cavities containing only the heart, great vessels, thymus, trachea and esophagus is called the
mediastinum
Myocardium
muscular, middle layer of the heart
interventricular septum
partition between the right and left ventricles