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46 terms

Cardio: cardiac muscle tissue and the cardiac conduction system

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they branch out, stair stepping appearance, 50-100 micrometers long
what do cardiac muscle tissue look like and how long are they
connects muscle fibers
what do intercalated discs do
hold fibers together
what do desmosomes do
allow muscle action potentials to conduct from one musscle to another
what do gap junctions do
25%
what % is mitochondria in the muscles
they are self excitable fibers, responible for lifelong heart beats, stimulate heart to beat even after it is removed from body
what is autorhythmic fibers and what do they do
1%
what % of fibers become autorhythmic fibers
pacemaker and conduction
what are the two important functions of autorhythmic fibers
setting the rhythm of electrical excitation that cause contraction of the heart
what is a pacemaker
network of specialized cardiac muscle fibers that provide a path for each cycle of cardiac excitation to progress through the heart. contract in a coordinated manner, make heart an effective pump
what is a conduction system
sinoatrial node, they do not have a stable resting membrane potential and depolarize spontaneously, which is a pacemaker potential,
where does an action potential start
when the pacemaker potential reaches threshold it triggers an action potential, travels throughout both atria via gap junctions in intercalated discs, following potential the atria contract
what creates an action potential and how/where does it travel
potential reaches the atrioventricular node in interatrial septum, then enters the atrioventricular bundle.
after sinoartrial node and and the atria contracts where does the potential go
bundle of his, it is the only place where potential conducts from atria to ventricles
what else is the atrioventricular bundle called and what is its significance
enters right and left bundle branches, which extends through the interventricular septum toward apex of heart
after bundle of his where does the potential go
purkinje fibers rapidly conduct the potential beginning at apex of heart upward to remainder of ventricular myocardium. then the ventricle contract pushing the blood upward toward the semilunar valve
after the potential is in the apex then what happens.
SA node, 100 times per minute, faster than other fibers b/c they spread and stimulate other areas before they generate an action potential on their own
what is teh natural pacemaker of the heart, why and how many potentials does it initate per minute
establish the rhythm
nerve impulses from ANS and hormones modify the timing and strength but do not..
-90mV
what is the resting membrane potential V
fibers reach threshold due to voltage-gated fast Na+ channels opening, inflow of Na down the electrochemicla gradient produces a rapid depolarization and the channels automatically inactivate and inflow decreases
explain depolarization
plateau
period of maintained depolarization
due to Ca2+ inflow when voltage gated slow Ca2+ channels open and K+ outflow when some K+ channels open - increase calcium triggers contraction
explain plateau
closure of Ca2+ channels and K+ outflow when additional voltage gated K+ channels open
explain repolarization
binds to troponin allowing the actina dn myosin and sliding filaments to happen which creates tension, if the flow of Ca2+ is altered so is the strength of contraction
what is the importance of Ca2+
time when second contraction cannot be triggerd, last longer than contraction itself
explain refractory period
this is good because if it could blood flow would cease since ventricles rely on the alteration of contraction
tetanus (2nd contraction during refractory) cant occur, why is this good
ATP mainly from aerobic respiration, at rest comes from fatty acids and glucose, during excersie lactic acid from skeletal muscles
where does the heart get atp from at rest and during exersice and anaerobic or aerobic
a recording of electrical signals which are generated by action potentials and can be dectected at the surface of the body, composite record of action potentials produced by all the heart muscle fibers during each heart beat
electrocardiogram
electrocardiograph
instrumnet used to record electrial signals
if conduction pathway is abnorma, heart is enlarged, certain regions are damaged, and cause of chest pain
what can and EKG determine
P wave, QRS complex, T wave
what does the EKG produce (waves)
first wave, small upward deflection, represents atrial depolarizations, spread from SA node through contractile fibers in both atria
P wave - explain
2nd wave, starts down goes upward as a large triangular wave ends as downward wave, represents rapid ventricular depolarization as actio potential spreads through ventricular contractile fibers.
explain QRS complex
3rd wave, dome shpaed upward deflection, indicates ventricular repolarization occurs just as the ventricles are starting to relax
explain T wave
it is flat
during the plateau the EKG is
enlargement of atrium
what does larger P waves indicate
indicate a myocardial infarction
what does larger Q waves indicate
indicates enlarged ventricles
what does larger R waves indicate
heart muscle is receiveng insufficient oxygen
what does flatter T wave indicate
intervals or segments
what is the spans b/w waves mean
beginning of P to beginning of QRS, represents conduction time from beginning of atrial excitation to beginning of ventricular excitation. lengthens when action potential detours around scar tissue
explain P-Q interval and when does it lengthen
begins at end of S wave and ends at beginning of T wave, represents time when ventricular contractile fibers are depolarized during plateau phase. elevated = acute myocardial infarction, depressed = insufficient oxygen
explain S-T segment, when it is elevated and depressed what that mean.
extends from start of QRS complex to end of T wave, beginning of ventricular depolarization to end of ventricular depolarization. lenghened by myocardial damage, decreased blood flow or conduction abnormalities
explain Q-T intereverl and when it is lengthened what does that mean.
phase of contraction
systole
phase of relaxation
diastole
depolarization of atrial contractile fiber produces P wave - atrial systole - depolarization of ventricular contractile fibers produces QRS complex - ventricular systole - repolarization of ventricular contractile fibers produces T wave - ventricular diastole relaxation
explain systlole and diastole inrelation to waves produces through out the heart