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Chapter 18

The Cardiovascular System - Cardiac Cycle, ECG's, Intrinsic Conduction System

pacemaker cells set the pace, one special thing about them is: they can spontaneously depolarize
this type of cell has an unstable resting potential. pacemaker cells
___ causes depolarization calcium
what is the pacemaker of the heart? SA node
3 steps of the cardiac action potentials. pacemaker potential -> depolarization -> repolarization
what happens in the pacemaker potential? the K+ channels close because of the opening of Na+ channels
in the depolarization phase the pacemaker potential __ reaches threshold - calcium causes depolarization
due to calcium channels and potassium channels opening the membrane potential goes back to negative voltage. this is because of __ repolarization
what is the fastest depolarization rate? SA node
this sets the rhythm via sinus rhythm & has the fastest depolarization rate SA node
step 1 of the intrinsic conduction system SA node generates impulses
after the SA node generates impulses. what happens? the wave spreads through the atrium to AV node
why is there a delay when the wave spreads from the atrium to AV node? because the muscle fibers are so small
step 3 of the intrinsic conduction system the AV bundle connects the atria to the ventricle
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
when the pukinje fibers network it: spread impulses to both ventricles, depolarizing the cells
there are no gap junctions connecting the __ and __ atria - ventricles
what is the purpose of the AV node/? it slows down impulses so contraction can occur
depolarization contracting
repolaruzation relaxing
what is an electrocardiogram (ECG) graphic record of the electrical activity of the heart
sequence of events when the atria & ventricles are contracting or relaxing is known as the: cardiac cycle
diastole refers to __, while systole refers to __ relaxation - contraction
heart murmur abnormal heart sounds that results from valve problems
condition of rapid & irregular heart contractions fibrillation
what are the 3 steps of the cardiac cycle? ventricular filling (mid to late diastole) ventricular systole early diastole
in ventricular filling (mid-to-late diastole) what happens? atrial contracts --> pumps blood to ventricle
during the ventricular filling the __ stays open allowing: mitral valve - blood to move in
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
in the early diastole ___ occurs. the ventricular filling then begins to open the __ and __ relaxation - AV valve , pushes blood to large ventricles
the semilunar valve closes during which step of the cardiac cycle? early diastole
the lub sound comes from the: AV valves closing
the dub sounds come from the: SV valves closing
arrythmias are __ irregular heart rhythms
extrasystole is a __ contraction premature
ectopic pacemakers with functional SA nodes can lead to: extrasystole
in defective SA nodes when the pacemaker is abnormal, what happens? the AV node becomes pacemaker
___ can cause uncoordinated atrial & ventricular contractions arrythmias
heart block occurs when __ there is damage to intrinsic network
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)
unlike skeletal muscles, cardiac cells can be__ autorhythmic
in cardiac cells, the heart contracts as a unit due to : gap junctions
muscle spasms cannot occur in cardiac muscles because... the refractory period is the same as contraction
atrial diastole occurs at__ QRS point
isovolumetric contraction & ejection are apart of: systole
in isovolumetric contraction, what is happening? no blood is leaving the heart - just pressure building up
in isovolumetric both valves are __ so the volume is ___ closed - constant, just increasing pressure
continued contraction and increase in pressure forces aortic valve to open & cause: ejection
isovolumetric relaxation and filling deals with: diastole
what happens at the P point of an ECG? atrial depolarization - systole starts
what happens at the QRS point of an ECG? ventricular depolarization - beginning of ventricular contraction
at the T point of an ECG, ventricular ___ takes place repolarization
ventricles are depolarized at the ___ segment ST
at the PR segment, atrial __ and ___ takes place depolarization & AV node conduction
condition of rapid & irregular heart contractions fibrillation
in fibrillation, blood vessels ___ aren't coordinated enough to deliver blood
aorta is the __ major systemic artery - arises from left ventricle of heart
heart murmurs are common in: children
the amount of blood pumped out of the ventricles to the body per minute is: cardiac output
the heart rate is set by the__ SA node
heart rate units: beats/min
stroke volume units: ml/beat
the normal stroke volume is__ 70 ml/beat
maximum amount of blood AFTER contractions is known as: End systolic volume (ESV)
End diastolic volume (EDV) maximum amount of blood BEFORE contractions
cardiac output = heart rate x stroke volume
the amount of blood pumped out of your heart with each heartbeat is known as__ stroke volume
average adult CO 75 beats/min (5.25L/min)
cardiac output has a direct relationship with __ heart rate & stroke volume
the volume pumped by each ventricle is the same, however.... the pressure is different
pressure is higher in which ventricle?" left
how do you calculate stroke volume? EDV-ESV
EDV is determined by __ length of ventricular diastole & venous return
ESV is determined by ___ arterial blood pressure & force of ventricular contraction
ESV is usually __ ml 50
EDV is usually __ ml 120
frank-starling law states: the greater the stretch, the greater the SV
preload is the degree to which cardiac muscle has stretched __ contarction before
preload means increase in __ which means increase in __ EDV - SV
low venous return results from __ blood loss of rapid heart rate - doesn't allow time for ventricular filling
excersise __ venous return through sympathetic activation & __ increases - squeezing action of skeletal muscles on veins
more calcium that enters, __ the contractions stronger
increase in contractility means ___ more blood is ejected, ESV decreases while SV increases
afterload is normally __ mmHg in the aorta 80
the CAC and CIC are located where? medulla
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
the CAC can effect ___, while the CIC effects the __ contractility - heart rate
exercise acts through the __ nervous system sympathetic
baroreceptors respons to : blood pressure changes
blood pressure changes when __ changes cardiac output
atrial reflex is initiated by: increase in venous return
when one autonomic division is activated by sensory input, the other is ___ temporarily inhibited
what is contractility? muscle cells ability to move by shortening
Created by: Mariahj25