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74 Cards in this Set

  • Front
  • Back
What are the functions of the heart?
generating blood pressure
routing blood: separates pulmonary and systemic
ensures one way flow via valves
regulates blood supply to match metabolic rates
Why does blood flow through the cardiovascular system?
because of pressure differences generated by the heart
What are the 2 major circulations of the heart?
Pulmonary
systemic
explain the pulmonary circulation
heart to lungs to heart

low pressure, low resistance
explain the systemic circulation
heart to all other organs to heart

high pressure, high resistance
Where is the heart located?
mediastinum
What cavity is divided into right and left and what separates them?
thoracic cavity separated by the mediastinum
What organs does the mediastinum contain?
heart
trachea
oesophagus
thymus
blood vessels and nerves
What are the coverings of the heart?
fibrous pericardium
serous pericardium
explain fibrous pericardium
for anchorage and protection
explain serous pericardium
has 3 layers
parietal layer
visceral layer
pericardial cavity between fill with pericardial fluid
What does the pericardial fluid help with?
friction against other organs
What are the 3 wall layers of the heart?
epicardium (visceral pericardium)
myocardium (cardiac muscle)
endocardium (lines chambers, covers walls)
What is the left atrioventricular valve called?
bicuspid
What is the right atrioventricular valve called?
tricuspid
Where are the semilunar valves located?
between ventricles and great vessels
Where is the semilunar pulmonary valve?
between the right ventricle and pulmonary trunk
Where is the semilunar aortic valve?
between left ventricle and the aorta
When the bicuspid valve is open are the papillary muscles contracted or relaxed?
relaxed
When the bicuspid valve is closed are the chordae tendinae taut or slack?
taut
What is the fibrous skeleton of the heart?
dense CT ring around the 4 valves
What does the fibrous skeleton provide?
anchorage
structural stability
electrical insulation between atria and ventricles
What is coronary circulation?
blood supply to the myocardium itself
What are the first branches of the ascending aorta?
R and L coronary arteries
large arteries travel in sulci on the heart surface
smaller branches penetrate the myocardium
How does blood return?
via cardiac veins which drain into the coronary sinus on posterior surface of the heart and then into the R atrium
explain cardiac muscle fibres
striated
branched
intercalated discs
desmosomes
gap junctions
Myocardial fibres are very __________ with many mitochondria, and oxidise fatty acids and __________ for energy
aerobic
glucose
What are the specialised cardiac tissue?
sino-atrial (SA) node
atroventricular (AV) node
AV bundle and purkinjie fibres
What is the normal pacemaker of the heart?
SA node
What are some things that specialized cells do?
very fast conduction system
spontaneously depolarise
have autorythemicity
What is the cardiac cycle?
one complete heartbeat
atrial systole and diastole and ventricular systole and diastole
What must cardia muscle do before it can contract and relax?
depolarise before contract
repolarise before relax

electrical events preceded mechanical events
What is the depolarisation sequence?
SA node
Atrial muscle
AV node (delay)
Atrioventricular bundle
R & L bundle branches
Purkinjie fibres
Ventricular muscle
When does atrial repolarisation occur?
during ventricular depolarisation
When is ventricular repolarisation complete?
prior to next cardiac cycle
Does the SA node have a stable resting membrane potential?
NO
membrane slowly depolarises until it reaches threshold when an action potential is triggered
the membrane then depolarises and immediately begins slow depolarisation again.......
Is the SA node more reliant on calcium or sodium?
calcium
What does calcium do?
rushes in to cause action potential
What has a stable RMP (resting membrane potential)?
myocardial fibres
When is an action potential initiated?
when stimulated by adjacent current flow
fibres remain depolarised for a long period what does this prevent?
premature re-exicitation and tetany
allows time for ventricular contraction
What happens on depolarisation?
membrane potential returns to RMP
What is a ECG?
sum of all the electrical events during the cardiac cycle as measured on the body surface
What are the electricals changes?
P wave
QRS wave
T wave
What does the P wave represent?
atrial depolarisation
What does the QRS wave represent?
ventricular depolarisation
What does the T wave represent?
ventricular repolarisation
What are the mechanical phases of the cardiac cycle?
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*
What is the sound of the lub?
closure of the AV valves
What is the sound of the dub?
closure of semilunar valves
What is the normal resting HR?
75 bpm
how long is each cardiac cycle?
.8 sec
What is EDV?
end diastolic volume

volume of blood in each ventricle at the end of filling
What is ESV?
end systolic volume

volume of blood in each ventricle at the end of emptying
What is SV?
stroke volume

volume of blood ejected per beat

SV=EDV-ESV e.g. 120-50=70ml
What is CO?
cardiac output

volume of blood ejected per ventricle per minute
What are the typical values at rest?
CO = 75bpm x 70ml per beat = 5250ml/min or 5.25l/min
What is cardiac reserve?
difference between CO at rest and the max CO a person can achieve
What are factors affecting heart rate?
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
What are 3 factors that can affect SV?
Preload (insintric)
contractability
Afterload
explain preload
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
What is Starlings law of the heart?
the greater the filling of the ventricles the greater is the emptying
What should the venous return be the same as?
CO
What is the major determinant of EDV?
venous return, this is venous flow back to the heart
What factors affect venous return?
blood volume (filling pressure)
central venous pressure/right atrial pressure
venous tone and capacity of veins to hold blood
skeletal muscle pump
respiratory pump
What is contractibility?
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
What is myocardial contractibility increased by?
sympathetic stimulation
adrenaline and noradrenaline
digoxin

Positive inotropic effect
What is myocardial contractibility decreased by?
decrease sympathetic stimulation
decreased adrenaline and noradrenaline
B blockers

Negative inotropic effect
What is after load?
the force against which the ventricles eject blood
What is the mean pulmonary arterial pressure for the right ventricle?
15-20mmHg
What is the aortic pressure for the left ventricle?
100mmHg
Each ventricle must develope enough __________ or wall tension to exceed this ___________ in order to eject blood into these ___________
force
pressure
arteries
compared to the RV the LV has....
higher afterload and therefore higher workload
greater muscle mass
greater O2 consumption
Why are myocardial infarctions more common in left ventricle than the right?
LV has a greater requirement of O2 for aerobic metabolism