Cardiovascular Structure & Function Flashcards
What is myocardium?
Cardiac muscle fibres arranged in 4 chambers: 2 atria, 2 ventricles
What is the conduction system?
Specialised tissue to conduct nerve impulses through heart, SAN + AVN, Bundle of His, bundle branches + Purkinje fibres
What us the nerve supply?
Nerve branches from both sympathetic + parasympathetic divisions of autonomic nervous system
What does the nerve supply regulate?
HR + force of contraction
Is the myocardium of left ventricle thicker than the right?
YES
What does the right + left coronary arteries branch off from?
Aorta
Where does the cardiac veins deliver blood to?
Coronary sinus + back to right atrium
What causes coronary artery disease?
Coronary artery cannot deliver blood = plaque on arterial walls
What is myocardium infarction?
When blood supply to heart is completely blocked, muscle dies
What is the pericardium?
Double-walled sac around heart
What is pericardium composed of?
Superficial fibrous pericardium
Deep two-layer serous pericardium
Parietal layer lines on internal surface
Visceral layer or epicardium line surface of heart
What is the pericardium separated by?
Fluid-filled pericardial cavity
What is the function of the pericardium?
Protects + anchors heart
Prevents overfilling of heart with blood
Allows heart to work relatively friction-free environment
What is the structure of veins + arteries?
Tunica interna Internal elastic lamina Tunica media External elastic lamina Tunica externa
What is the difference between veins and arteries?
Veins have valves and are wider
What is the structure of capillaries?
Endothelial cells
What is the function of the heart?
Regulate blood supply
Generate blood pressure
What is the function of valves?
Ensure one-way flow
What are the 2 circuits?
Pulmonary
Systemic
What is the pulmonary circuit?
Blood to + from the lungs
What is the systemic circuit?
Blood to + from rest of body
What type of vessels are arteries?
Pressure vessels
What type of vessels are veins?
Capacitance vessels + can distend to match blood volume
What is the cardiac cycle?
Electrical, pressure + vol changes that occur in functional heart between 2 heart beats
What is the diastolic phase?
Phase of cycle when myocardium is relaxing
What is the systolic phase?
Phase of cycle where myocardium is contracting
What happens in the ventricular filling period?
1
Ventricular diastole
Atrial systole
What happens in isovolumetric contraction period?
2
Ventricular systole
What happens in ventricular ejection period?
3
Ventricular systole
What happens in isovolumetric relaxation period?
4
Ventricular diastole
Atrial diastole
Describe the cardiac cycle
Venous returns to RA
Venous flow arrives in RV
Venous blood is sent to lung via pulmonary artery
After oxygenation in lung, the blood returns LA
Blood arrives at LV
Blood sent to arteries in tissues
Describe the flow of blood
RA –> Tricuspid valve –> RV –> Pulmonary semi-lunar valve –> Pulmonary trunk –> Pulmonary arteries –> Lungs –> Pulmonary veins –> LA –> Bicuspid valve –> LV –> Aortic semi-lunar valves –> Aorta –> Body tissue –> Superior + inferior vena cava –> RA
What are the phases of the cardiac cycle
Atrial diastole + systole
Ventricular filling: mid to late diastole
Ventricular systole
Ventricular diastole
Describe what happens in atrial diastole + systole
Blood flows into + passively out of atria; AV valves open
Atrial systole pumps about 20% blood into ventricles
Describe what happens in ventricular filling: mid to late diastole
Heart blood pressure is low as blood enters atria + flows into ventricles
80% of blood enters ventricles passively; atrial systole occurs pumping other 20%
Describe what happens in ventricular systole
Atria relax; rising ventricular pressure closes AV valves
Isovolumetric contraction phase
Ventricles contract, no blood leaving
Ventricular ejection phase opens semilunar valves
Describe what happens in ventricular diastole
Ventricles relax; blood backflow, closes semilunar valves
Blood once again flowing into relaxed atria + passively into ventricles
What sounds does the heart make?
“LUB”
“DUB”
Why does the heart make “LUB” sound?
Closure of AV valves (mitral + bicuspid) + tricuspid valves: mitral before tricuspid
What does the “LUB” sound correlate with?
Carotid pulse
Where is the “LUB” loudest?
Cardio apex
Why does the heart make “DUB” sound?
Closure of semilunar valves
Where is the “DUB” sound loudest?
Base of heart
What is pulse?
Surge of pressure in artery
What is the pulse of infants?
120 bmp or more
What is the pulse of young females?
72-80 bpm
What is the pulse of young males?
64-72 bpm
What happens to pulse when someone becomes elderly?
Gets higher again
What is tachycardia?
Resting HR in excess 100 bpm
What is tachycardia caused by?
Stress, anxiety, drugs, heart disease
What is bradycardia?
HR less than 60 bpm
What are premature atrial contractions?
Occasional shortened intervals between 1 contraction + next
What is cardiac output (CO)?
Amount of blood pumped out by each ventricle in 1 minute
What is the cardiac output equation?
CO = HR X SV
What is CO measured in?
ml/min
What is HR measured in?
bpm
What is stroke volume measured in?
ml/beat
What is cardiac reserve?
Difference between resting + max CO
What factors effect HR?
Autonomic innervation
Hormones
What factors effect SV?
End-diastolic vol
End-systolic vol
What is SV?
Vol of blood pumped by a ventricle per beat
How do you work out SV?
End-diastolic vol (EDV) - end-systolic vol (ESV)
What is EDV?
Amount of blood in a ventricle at end of diastole
What is ESV?
Amount of blood remaining in ventricle after contraction
What is the ejection factor?
% of EV pumped by ventricle
What factors effect EDV?
Venous return (VR) Filling time (FT)
What factors effect ESV?
Contractility of muscle cells
Afterload
What happens to EDV when you increase VR?
EDV increases
What happens to EDV when you increase FT?
EDV increases
What happens to ESV when you increase afterload?
ESV increases
What happens to ESV when you increase contractility of muscle cells?
ESV decreases
What is blood flow affected by?
Pressure + resistance
What is blood pressure?
The force exerted by blood against blood vessel walls
What detects blood pressure changes?
Baroreceptors
Where is blood pressure highest?
In largest arteries
When is blood pressure highest?
With ventricular systole
When is blood pressure lowest?
With ventricular diastole
What increases blood pressure?
Blood vol increases HR increases SV increases Blood viscosity increases Peripheral resistance increases
What happens when blood pressure gets too high?
Cardiac output increases Blood pressure increases Baroreceptors in aortic arch + carotid sinuses stimulated Sensory impulses to cardiac centre Parasympathetic impulses to heart SA node inhibited HR decreases Blood pressure returns to normal
What is preload?
Tension applied before muscle performs any work
EDV
What happens when you increase filling pressure?
Preload increases
What is afterload?
Load that preloaded muscle has to work against
Aortic pressure present at the instant that aortic valve open
What does it mean if there is a higher aortic diastolic pressure?
Greater work to pump blood into heart
What is preload + afterload estimated using?
Laplace’s law
What is Laplace’s law?
WWS = Pressure X radius / 2 (wall thickness)
What is the Frank-Starling mechanism?
Change of heart’s force of contraction in response to change in venous return
Describe the Frank-Starling mechanism
Increased venous return increases ventricular filling (EDV) + preload
What does myocyte stretching cause?
Increase in force of generation
What does the Frank-Starling mechanism enable?
The heart to eject additional venous return, thereby increasing SV
What happens to CO if afterload increases?
CO decreases
What happens to CO if preload increases?
CO increases
What is systolic heart failure?
Less blood pumped out of ventricles
= weakened heart muscles can’t squeeze as well
What is diastolic heart failure?
Less blood fills ventricles
= stiff heart muscle can’t relax normally