3. Chest pain

Question 1

describe relationship of BP & SVR with parasympathetic nervous system

Answer 1

no parasympathetic innervation of blood vessels

Question 2

describe relationship of SVR & BP with the sympathetic nervous system

Answer 2

sympathetic nerves decrease peripheral blood vessel diameter thereby increasing systemic vascular resistance and increasing blood pressure

Question 3

occlusion of what is most likely to result in a fatal heart attack

Answer 3

left main coronary artery

Question 4

which nerve innervates the pericardium?

Answer 4

Phrenic nerve

Question 5

what is the stroke volume of the average person

Answer 5

70 mls

Question 6

stroke volume equation

Answer 6

SV = end diastolic volume (EDV) - end-systolic volume (ESV)

Question 7

what increases to signify left heart failure?

Answer 7

left ventricular end-diastolic pressure

Question 8

what increases to indicate mitral valve stenosis

Answer 8

left atrial end-systolic pressure

Question 9

what is the purpose of the Ductus Arteriosus in the foetal cardiovascular system?

Answer 9

allow blood to bypass the foetal lungs by shunting it from the pulmonary artery to the aorta

Question 10

cardiac output equation

Answer 10

CO = HR x SV

Question 11

pulmonary oedema in the presence of a normal central venous pressure is a sign of

Answer 11

left heart failure

Question 12

severe pulmonary hypertension is a cause of

Answer 12

right heart failure

Question 13

shortness of breath, severe peripheral oedema and ascites after a heart attack indicates

Answer 13

biventricular failure

Question 14

which artery most frequently supplies the AVN?

Answer 14

right coronary artery

Question 15

define cardiac output

Answer 15

volume of blood expelled by either ventricle of the heart

the amount of blood the heart pumps through the circulatory system in a minute

Question 16

what is the normal cardiac output of an adult

Answer 16

4.7 litres of blood per minute

Question 17

cardiac output equation

Answer 17

CO=SV x HR

Question 18

define stroke volume

Answer 18

is the volume of blood pumped out of each ventricle each time the heart beats

Question 19

Starling’s law of the heart

Answer 19

• ‘the strength of the heart’s systolic contraction is directly proportional to its diastolic expansion, with the result that under normal physiological conditions the heart pumps out of the right atrium all the blood returned to it without letting any back up in the veins’
• The Frank-Starling Law states that the stroke volume of the left ventricle will increase as the left ventricular volume increases due to the myocyte stretch causing a more forceful systolic contraction

Question 20

when is myocardial perfusion

Answer 20

• myocardial perfusion occurs during heart relaxation when the subendocardial coronary vessels are open
perfused by the coronary arteries during the ventricular systole. The origins of the coronary arteries is behind the aortic semilunar valve which fills with blood during the ventricular diastole which then allows blood to be pumped into the coronary artery

Question 21

cardiac cycle - systole

Answer 21

systole - 
•	L ventricle contracts
•	pressure increases
•	mitral + AV valves closed 
0.3 seconds 
pressure reaches 75mm Hg - just higher than pressure in aorta - AV valve opens

Question 22

cardiac cycle - ejection phase

Answer 22

Ejection phase:
• 75mm Hg - at beginning - lowest BP in aorta - diastolic BP
• 0.25s
• blood ejected from LV to aorta - L ventricular volume decreases
• L ventricle continues to contract - pressure increases
• aortic pressure also increases (both equal)
• peak of 120 mm Hg reached - systolic BP - then decreases again
• difference in systolic and diastolic = pulse pressure (PP)
when aortic pressure increases pressure in L ventricle, AV valve closes - S2 (2nd heart sound) -
end systolic point reached - volume inside L ventricle = 50ml
ejection fraction = stroke volume / end diastolic volume

Question 23

diastole

Answer 23

Ventricular relaxation and blood filling - 0.5 seconds:
• reduced ejectioon
• ventricles relax - aortic and pulmonary valves close - AV valves closed so no blood enters or leaves ventricles - isovolumetric relaxation (decrease in pressure, volume same)
• rapid ventricle filling and ventricle suction - blood in atria slightly pressurised due to
venous return from superior and inferior vena cava + pulmonary vein.
o pressure enough to open mitral and tricuspid valves
o lower pressure in ventricles than atria - mitral valve opens - pressure gradient -
blood moves down it - responsible for 80% of ventricular filling before atrial
contraction (other 20% from atrial contraction)

Question 24

stroke volume equation

Answer 24

stroke volume = end diastolic volume - end systolic volume

Question 25

ventricular tachycardia

Answer 25

not filling before it contracts

Question 26

ventricular fibrillation

Answer 26

not enough blood pumped around the body

Question 27

describe the coronary circulation of the heart

Answer 27

two coronary arteries arise from the aorta just beyond the semilunar valves; during diastole, the increased aortic pressure above the valves forces blood into the coronary arteries and thence into the musculature of the heart. Deoxygenated blood is returned to the chambers of the heart via coronary veins; most of these converge to form the coronary venous sinus, which drains into the right atrium

Question 28

occlusion of the LAD

Answer 28

• Over time fatty deposits and calcium build up on inner artery walls and form plaque (atherosclerosis)
• It is the most commonly occluded of the coronary arteries Depending on where the occlusion is the left ventricle, right ventricle and IV septum can be affected.
symptoms: chest pain, sweating, difficulty breathing etc.

Question 29

effects on the cardiac conduction pathway of occlusion of LAD

Answer 29

• Occlusion of the LAD artery leads to necrosis in the conducting system
• This can completely block impulse conduction between the atria and the ventricles
• Impulse conduction between the atria and ventricles can also be blocked (right/left bundle branch block)
• This can lead to Ventricular tachycardia (VT) and ventricular fibrillation (VF) which can lead to death