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74 Cards in this Set
- Front
- Back
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What are the functions of the heart?
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generating blood pressure
routing blood: separates pulmonary and systemic ensures one way flow via valves regulates blood supply to match metabolic rates |
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Why does blood flow through the cardiovascular system?
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because of pressure differences generated by the heart
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What are the 2 major circulations of the heart?
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Pulmonary
systemic |
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explain the pulmonary circulation
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heart to lungs to heart
low pressure, low resistance |
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explain the systemic circulation
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heart to all other organs to heart
high pressure, high resistance |
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Where is the heart located?
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mediastinum
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What cavity is divided into right and left and what separates them?
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thoracic cavity separated by the mediastinum
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What organs does the mediastinum contain?
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heart
trachea oesophagus thymus blood vessels and nerves |
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What are the coverings of the heart?
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fibrous pericardium
serous pericardium |
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explain fibrous pericardium
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for anchorage and protection
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explain serous pericardium
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has 3 layers
parietal layer visceral layer pericardial cavity between fill with pericardial fluid |
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What does the pericardial fluid help with?
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friction against other organs
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What are the 3 wall layers of the heart?
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epicardium (visceral pericardium)
myocardium (cardiac muscle) endocardium (lines chambers, covers walls) |
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What is the left atrioventricular valve called?
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bicuspid
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What is the right atrioventricular valve called?
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tricuspid
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Where are the semilunar valves located?
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between ventricles and great vessels
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Where is the semilunar pulmonary valve?
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between the right ventricle and pulmonary trunk
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Where is the semilunar aortic valve?
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between left ventricle and the aorta
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When the bicuspid valve is open are the papillary muscles contracted or relaxed?
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relaxed
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When the bicuspid valve is closed are the chordae tendinae taut or slack?
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taut
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What is the fibrous skeleton of the heart?
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dense CT ring around the 4 valves
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What does the fibrous skeleton provide?
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anchorage
structural stability electrical insulation between atria and ventricles |
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What is coronary circulation?
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blood supply to the myocardium itself
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What are the first branches of the ascending aorta?
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R and L coronary arteries
large arteries travel in sulci on the heart surface smaller branches penetrate the myocardium |
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How does blood return?
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via cardiac veins which drain into the coronary sinus on posterior surface of the heart and then into the R atrium
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explain cardiac muscle fibres
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striated
branched intercalated discs desmosomes gap junctions |
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Myocardial fibres are very __________ with many mitochondria, and oxidise fatty acids and __________ for energy
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aerobic
glucose |
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What are the specialised cardiac tissue?
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sino-atrial (SA) node
atroventricular (AV) node AV bundle and purkinjie fibres |
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What is the normal pacemaker of the heart?
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SA node
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What are some things that specialized cells do?
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very fast conduction system
spontaneously depolarise have autorythemicity |
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What is the cardiac cycle?
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one complete heartbeat
atrial systole and diastole and ventricular systole and diastole |
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What must cardia muscle do before it can contract and relax?
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depolarise before contract
repolarise before relax electrical events preceded mechanical events |
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What is the depolarisation sequence?
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SA node
Atrial muscle AV node (delay) Atrioventricular bundle R & L bundle branches Purkinjie fibres Ventricular muscle |
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When does atrial repolarisation occur?
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during ventricular depolarisation
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When is ventricular repolarisation complete?
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prior to next cardiac cycle
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Does the SA node have a stable resting membrane potential?
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NO
membrane slowly depolarises until it reaches threshold when an action potential is triggered the membrane then depolarises and immediately begins slow depolarisation again....... |
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Is the SA node more reliant on calcium or sodium?
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calcium
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What does calcium do?
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rushes in to cause action potential
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What has a stable RMP (resting membrane potential)?
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myocardial fibres
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When is an action potential initiated?
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when stimulated by adjacent current flow
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fibres remain depolarised for a long period what does this prevent?
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premature re-exicitation and tetany
allows time for ventricular contraction |
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What happens on depolarisation?
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membrane potential returns to RMP
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What is a ECG?
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sum of all the electrical events during the cardiac cycle as measured on the body surface
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What are the electricals changes?
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P wave
QRS wave T wave |
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What does the P wave represent?
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atrial depolarisation
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What does the QRS wave represent?
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ventricular depolarisation
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What does the T wave represent?
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ventricular repolarisation
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What are the mechanical phases of the cardiac cycle?
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atrial systole follows atrial depolarisation
ventricular systole follows ventricular depolarisation ventricular diastole follows ventricular depolarisation *learn these in more detail from slide in lecture 2/2* *learn last page as well* |
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What is the sound of the lub?
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closure of the AV valves
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What is the sound of the dub?
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closure of semilunar valves
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What is the normal resting HR?
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75 bpm
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how long is each cardiac cycle?
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.8 sec
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What is EDV?
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end diastolic volume
volume of blood in each ventricle at the end of filling |
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What is ESV?
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end systolic volume
volume of blood in each ventricle at the end of emptying |
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What is SV?
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stroke volume
volume of blood ejected per beat SV=EDV-ESV e.g. 120-50=70ml |
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What is CO?
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cardiac output
volume of blood ejected per ventricle per minute |
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What are the typical values at rest?
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CO = 75bpm x 70ml per beat = 5250ml/min or 5.25l/min
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What is cardiac reserve?
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difference between CO at rest and the max CO a person can achieve
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What are factors affecting heart rate?
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Neural- controlled through cardiovascular centre in medulla oblongata
Parasympathetic nerves (via vagus)- slow HR, dominant at rest Sympathetic "accelerator" nerves- increase HR Hormones- adrenaline, noradrenaline, thyroid hormones other- body temp, phycological factors through defending CVS |
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What are 3 factors that can affect SV?
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Preload (insintric)
contractability Afterload |
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explain preload
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the force or load on ventricular muscle just prior to contraction
determined by EDV, as EDV increases so does SV if EDV is decreased so does SV this is insintric control of SV |
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What is Starlings law of the heart?
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the greater the filling of the ventricles the greater is the emptying
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What should the venous return be the same as?
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CO
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What is the major determinant of EDV?
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venous return, this is venous flow back to the heart
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What factors affect venous return?
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blood volume (filling pressure)
central venous pressure/right atrial pressure venous tone and capacity of veins to hold blood skeletal muscle pump respiratory pump |
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What is contractibility?
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refers to the inotropic state of the heart
the strength of ventricular contraction at any given preload dependant on Ca+ concentration in muscle fibres during contraction, increase of Ca+ increase contractibility, decrease of Ca++ decrease contractibility this is extrinsic control of SV |
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What is myocardial contractibility increased by?
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sympathetic stimulation
adrenaline and noradrenaline digoxin Positive inotropic effect |
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What is myocardial contractibility decreased by?
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decrease sympathetic stimulation
decreased adrenaline and noradrenaline B blockers Negative inotropic effect |
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What is after load?
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the force against which the ventricles eject blood
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What is the mean pulmonary arterial pressure for the right ventricle?
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15-20mmHg
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What is the aortic pressure for the left ventricle?
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100mmHg
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Each ventricle must develope enough __________ or wall tension to exceed this ___________ in order to eject blood into these ___________
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force
pressure arteries |
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compared to the RV the LV has....
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higher afterload and therefore higher workload
greater muscle mass greater O2 consumption |
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Why are myocardial infarctions more common in left ventricle than the right?
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LV has a greater requirement of O2 for aerobic metabolism
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