The Cardiovascular System - Cardiac Cycle, ECG's, Intrinsic Conduction System
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| pacemaker cells set the pace, one special thing about them is: | they can spontaneously depolarize
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| this type of cell has an unstable resting potential. | pacemaker cells
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| ___ causes depolarization | calcium
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| what is the pacemaker of the heart? | SA node
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| 3 steps of the cardiac action potentials. | pacemaker potential -> depolarization -> repolarization
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| what happens in the pacemaker potential? | the K+ channels close because of the opening of Na+ channels
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| in the depolarization phase the pacemaker potential __ | reaches threshold - calcium causes depolarization
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| due to calcium channels and potassium channels opening the membrane potential goes back to negative voltage. this is because of __ | repolarization
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| what is the fastest depolarization rate? | SA node
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| this sets the rhythm via sinus rhythm & has the fastest depolarization rate | SA node
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| step 1 of the intrinsic conduction system | SA node generates impulses
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| after the SA node generates impulses. what happens? | the wave spreads through the atrium to AV node
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| why is there a delay when the wave spreads from the atrium to AV node? | because the muscle fibers are so small
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| step 3 of the intrinsic conduction system | the AV bundle connects the atria to the ventricle
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| after the AV bundle connects the atria to the ventricle, the ___ and lastly the __ | bundle branches conduct impulses to the inter-ventricular septum - the punkinje fibers connect
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| when the pukinje fibers network it: | spread impulses to both ventricles, depolarizing the cells
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| there are no gap junctions connecting the __ and __ | atria - ventricles
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| what is the purpose of the AV node/? | it slows down impulses so contraction can occur
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| depolarization | contracting
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| repolaruzation | relaxing
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| what is an electrocardiogram (ECG) | graphic record of the electrical activity of the heart
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| sequence of events when the atria & ventricles are contracting or relaxing is known as the: | cardiac cycle
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| diastole refers to __, while systole refers to __ | relaxation - contraction
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| heart murmur | abnormal heart sounds that results from valve problems
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| condition of rapid & irregular heart contractions | fibrillation
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| what are the 3 steps of the cardiac cycle? | ventricular filling (mid to late diastole)
ventricular systole
early diastole
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| in ventricular filling (mid-to-late diastole) what happens? | atrial contracts --> pumps blood to ventricle
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| during the ventricular filling the __ stays open allowing: | mitral valve - blood to move in
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| the ventricular systole is known as the ___ phase. during this phase no ___ . after this phase the ___ occurs | isovolumetric contraction - blood has left yet - ventricular ejection
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| in the early diastole ___ occurs. the ventricular filling then begins to open the __ and __ | relaxation - AV valve , pushes blood to large ventricles
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| the semilunar valve closes during which step of the cardiac cycle? | early diastole
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| the lub sound comes from the: | AV valves closing
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| the dub sounds come from the: | SV valves closing
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| arrythmias are __ | irregular heart rhythms
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| extrasystole is a __ contraction | premature
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| ectopic pacemakers with functional SA nodes can lead to: | extrasystole
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| in defective SA nodes when the pacemaker is abnormal, what happens? | the AV node becomes pacemaker
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| ___ can cause uncoordinated atrial & ventricular contractions | arrythmias
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| heart block occurs when __ | there is damage to intrinsic network
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| 5 distinct characteristics in cardiac muscle thats not in skeletal. | no muscle spasms.
extracellular fluid involved -> triggers calcium release.
self excitable.
heart contracts as a unit.
heart relies on aerobic respiration (lots of mitochondria - resistance to fatigue)
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| unlike skeletal muscles, cardiac cells can be__ | autorhythmic
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| in cardiac cells, the heart contracts as a unit due to : | gap junctions
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| muscle spasms cannot occur in cardiac muscles because... | the refractory period is the same as contraction
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| atrial diastole occurs at__ | QRS point
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| isovolumetric contraction & ejection are apart of: | systole
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| in isovolumetric contraction, what is happening? | no blood is leaving the heart - just pressure building up
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| in isovolumetric both valves are __ so the volume is ___ | closed - constant, just increasing pressure
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| continued contraction and increase in pressure forces aortic valve to open & cause: | ejection
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| isovolumetric relaxation and filling deals with: | diastole
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| what happens at the P point of an ECG? | atrial depolarization - systole starts
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| what happens at the QRS point of an ECG? | ventricular depolarization - beginning of ventricular contraction
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| at the T point of an ECG, ventricular ___ takes place | repolarization
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| ventricles are depolarized at the ___ segment | ST
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| at the PR segment, atrial __ and ___ takes place | depolarization & AV node conduction
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| condition of rapid & irregular heart contractions | fibrillation
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| in fibrillation, blood vessels ___ | aren't coordinated enough to deliver blood
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| aorta is the __ | major systemic artery - arises from left ventricle of heart
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| heart murmurs are common in: | children
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| the amount of blood pumped out of the ventricles to the body per minute is: | cardiac output
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| the heart rate is set by the__ | SA node
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| heart rate units: | beats/min
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| stroke volume units: | ml/beat
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| the normal stroke volume is__ | 70 ml/beat
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| maximum amount of blood AFTER contractions is known as: | End systolic volume (ESV)
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| End diastolic volume (EDV) | maximum amount of blood BEFORE contractions
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| cardiac output = | heart rate x stroke volume
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| the amount of blood pumped out of your heart with each heartbeat is known as__ | stroke volume
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| average adult CO | 75 beats/min (5.25L/min)
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| cardiac output has a direct relationship with __ | heart rate & stroke volume
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| the volume pumped by each ventricle is the same, however.... | the pressure is different
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| pressure is higher in which ventricle?" | left
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| how do you calculate stroke volume? | EDV-ESV
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| EDV is determined by __ | length of ventricular diastole & venous return
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| ESV is determined by ___ | arterial blood pressure & force of ventricular contraction
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| ESV is usually __ ml | 50
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| EDV is usually __ ml | 120
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| frank-starling law states: | the greater the stretch, the greater the SV
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| preload is the degree to which cardiac muscle has stretched __ contarction | before
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| preload means increase in __ which means increase in __ | EDV - SV
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| low venous return results from __ | blood loss of rapid heart rate - doesn't allow time for ventricular filling
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| excersise __ venous return through sympathetic activation & __ | increases - squeezing action of skeletal muscles on veins
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| more calcium that enters, __ the contractions | stronger
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| increase in contractility means ___ | more blood is ejected, ESV decreases while SV increases
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| afterload is normally __ mmHg in the aorta | 80
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| the CAC and CIC are located where? | medulla
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| the cardioaccelatory system (CAC) is more global, therefore it talks to the __ while the cardioinhibitory system (CIC) talks to the __ | SA node, AV node and other parts of heart - SV & AV nodes
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| the CAC can effect ___, while the CIC effects the __ | contractility - heart rate
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| exercise acts through the __ nervous system | sympathetic
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| baroreceptors respons to : | blood pressure changes
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| blood pressure changes when __ changes | cardiac output
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| atrial reflex is initiated by: | increase in venous return
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| when one autonomic division is activated by sensory input, the other is ___ | temporarily inhibited
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| what is contractility? | muscle cells ability to move by shortening
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