Chapter 18 - Cardiovascular System: The Heart Part B
Cardiac muscle contraction: What opens voltage-gated fast Na+ channels in the sarcolemma?
Depolarization wave in T tubules causes the SR to release what?
Depolarization also opens slow _____ channels in the sarcolemma
In cardiac muscle contraction, there is a reversal of membrane potential from _____ mV to _____ mV
Repolarization results from inactivation of _____ channels and opening of voltage-gated ____ channels
A network of noncontractile cells that initiate and distribute impulses to coordinate the depolarization and contraction of the heart
intrinsic cardiac conduction system
What has unstable resting potentials (pacemaker potentials) due to open slow Na+ channels?
Sequence of excitation: What is present in the right atrium and generates impulses about 75 times/minute?
sinoatrial (SA) node (pacemaker)
Sequence of excitation: what depolarizes faster than any other part of the myocardium?
Sequence of excitation: What has smaller diameter fibers, fewer gap junctions, and delays impulses approximately 0.1 second?
atrioventricular (AV) node
What depolarizes 50 times per minute in the absence of SA node input?
Sequence of excitation: What is the only electrical connection between the atria and ventricles - divides into the left and right bundle branches?
atrioventricular (AV) bundle (bundle of His)
What are the two pathways in the inter-ventricular septum that carry the impulses toward the apex of the heart?
right and left bundle branches
What completes the pathway into the apex and ventricular walls?
What depolarize only 30 times per minute in the absence of AV node output?
AV bundle and Purkinje fibers
What are irregular heart rhythms?
What are rapid, irregular contractions, useless for pumping blood?
A defective SA node may result in?
ectopic focus (abnormal pacemaker takes over) or if AV node takes over, a junctional rhythm (40-60 bpm)
A defective AV node may result in?
partial or total heart block; few or no impulses from SA node reach the ventricle
Intrinsic innvervation of the heart involves:
SA node generating impulse, which pauses at AV node; AV bundle connects atria to ventricles; bundle branches conduct impulses through interventricular septum; Purkinje fibers depolarize contractile cells of both ventricles
Defects in the intrinsic conduction system may result in?
arrhythmias; uncoordinate atrial and ventricular contractions; fibrillations
Extrinsic innervation of the heart: heartbeat is modified by the?
Extrinsic innervation of heart: what center innervates SA and AV nodes, heart muscle, and coronary arteries through sympathetic neurons?
Extrinsic innervation of the heart: What center inhibits SA and AV nodes through parasympathetic fibers in vagus nerves?
What part of the ANS increases heart rate?
Which part of the ANS slows heart rate?
What is a composite of all the action potentials generated by nodal and contractile cells at a given time?
What are the three waves of an EKG?
P wave, QRS complex, T wave
Which EKG wave is the depolarization of the SA node?
Which EKG wave is ventricular depolarization (activation of muscle fibers, contraction, blood pumped out)?
Which EKG wave is ventricular repolarization (coming back to the original state, heart filled with blood)?
When atrials contract, what do ventricles do?
What is low oxygen tension in the blood called?
What is low oxygen tension called?
An EKG that shows no irregularites is called?
normal sinus rhythm
An EKG that shows the SA node is nonfunctional, P waves are absent, and the heart is paced by the AV node at 40-60bpm is called?
An EKG that shows some P waves are not conducted through the AV node, resulting in more P waves than QRS complexes (ratio 2 to 1) is called?
second-degree heart block
Chaotic, grossly irregular EKG deflections are seen in acute heart attack and electrical shock. They are called?
Hearts sounds are caused by what?
closing heart valves
Which heart sound occurs as AV valves close, signifying the beginning of systole/ blood pumping away from the heart?
the first sound (lub)
Which heart sound occurs when SL valves close at the beginning of ventricular diastole/blood going back into the heart?
the second sound (dup)
What are abnormal heart sounds most often indicative of valve problems
Which heart sound is the closing of the mitral and tricuspid valves?
the first sound
Which heart sound is the closure of semilunar walls of aorta and pulmonary trunk?
the second sound
All events associated with blood flow through the heart during a complete heartbeat is called?
What are the phases of the cardiac cycle?
ventriuclar filling, ventricular systole, isovolumetric relaxation
What is the volume of blood in each ventricle at the end of ventricular diastole?
End diastolic volume (EDV)
What is the volume of blood remaining in each ventricle after the end of systole?
End systolic volume (ESV)
When does isovolumetric relaxation occur?
in early diastole
What is a brief rise in aortic pressure that leads to the closure of the semilunar valves?
What is the volume of blood pumped by each ventricle in one minute?
cardiac output (CO)
How do you determine cardiac output?
heart rate (HR) x stroke volume (SV)
Heart rate is?
number of beats per minute
Stroke volume is ?
volume of blood pumped out by a ventricle with each beat
What is the difference between resting and maximum cardiac output?
What are the three main factors affecting stroke volume (SV)?
preload, contractibility, after load
What is the degree of stretch cardiac muscle cells have before they contract ?
What is the Frank-Starling law of the heart?
the shorter the fiber, the shorter the power of contractibility
What is the contractile strength at a given muscle length, independent of muscle stretch and EDV?
What is the pressure that must be overcome for ventricles to eject blood?
Hypertension increases afterload, resulting in ?
increased ESV and reduced SV
What hormones are involved with regulation of heart rate?
epinephrine and thyroxine
What is an abnormally fast heart rate called?
What is the bpm of tachycardia?
What is a heart rate slower than 60 bpm called?
What is a progressive condition where the cardiac output is so low that blood circulation is inadequate to meet tissue needs?
congestive heart failure
What is dilated cardiomyopathy?
muscle fibers elongate and stretch - heart enlarges/bursts
Why do you see swelling/edema in the ankles of someone with congestive heart failure?
there is no venous return, blood pools to lower extremeties
Blood travels into the right atrium via what?
superior and inferior vena cava
Blood travels from the right atrium to the right ventricle via?
Blood travels from the right ventricle through _____ to the lungs
Blood travels from the left atrium to the left ventricle through what?
What is the final valve blood travels though to get to the rest of the body?
the aortic valve (through the aorta)