Cardiac Definitions and Heart Sounds

Question 1

left ventricle

Answer 1

palpated in the 5th intercostal space and mid-clavicular line, responsible for the apex beat

Question 2

stroke volume

Answer 2

volume of blood ejected from each ventricle during sytosole

Question 3

cardiac output

Answer 3

volume of blood each ventricle pumps as a function of time (litres per minute)

Question 4

total peripheral resistance

Answer 4

total resistance to flow in systemic blood vessels from beginning aorta to vena cava - arterioles provide the most resistance

Question 5

preload

Answer 5

volume of blood in left ventricle which stretches the cardiac myocytes before left ventricular contraction (end diastolic volume)

when veins dilate, it results in decrease in preload (since by dilating veins the venous return increases)

Question 6

afterload

Answer 6

pressure the left ventricle must overcome to eject blood during contraction (dilate arteries –> decrease in afterload)

Question 7

contractility

Answer 7

force of contraction and change in fibre length - how hard the heart pumps. when muscle contracts myofibrils stay the same length but sarcomere shortens, force of heart contraction is independent of sarcomere length

Question 8

elasticity:

Answer 8

myocardial ability to recover normal shape after systolic stress

Question 9

diastolic dispensibility

Answer 9

the pressure required to fill the ventricle to the same diastolic volume

Question 10

compliance

Answer 10

how easily the heart chamber expands when filled with blood volume

Question 11

Starlings law

Answer 11

force of contraction is proportional to end diastolic length of cardiac muscle fibre - the more ventricle fills, the harder it contracts

below optimal length means force of contraction is decreased –> inefficient

increased venous return = increased end diastolic volume = increased preload = increased sarcomere stretch = increased force of contraction = increased stroke volume and force of contractions

Question 12

why does standing cause a decrease in venous return?

Answer 12

gravity

cardiac output decreases ==> blood pressure drops –> baroreceptors stimulated –> blood pressure increases

Question 13

intrinsic autoregulation

Answer 13

when arterioles either vasoconstrict or vasodolate in response to changes in resistance, with the aim of maintaining constant blood flow

Question 14

myogenic autoregulation

Answer 14

when blood flow is increased and stretches vascular smooth muscle, the muscle automatically constricts until the diameter is normalised or slightly reduced. Similarly, when the smooth muscle isn’t getting stretched as much due to low blood pressure, the muscle relaxes and dilates in response.

Question 15

hypermia

Answer 15

increased blood flow

Question 16

active hypermia

Answer 16

increased blood flow when metabolic activity is increased

Question 17

reactive hypermia

Answer 17

when an organ/tissue has its blood supply completely occluded (stopped/closed up), a profound transient increase in its blood flow occurs if blood flow is established (extreme form of autoregulation)

Question 18

what are the three heart sounds?

Answer 18

1. soft, low pitched lub associated with closure of atrioventricular valves
2. second, louder dub asociated with the closure of aortic and pulmonary valves
3. sound of blood rushing into left ventricle