Heart

Question 1

why does the left ventricle have a thicker wall?

Answer 1

so it can contract more forcefully since the blood is being pumped out into the body

Question 2

with each beat where does the left and right side send blood?

Answer 2

right side - deoxygenated blood from body => lungs
left side - oxygenated blood from lungs => body

Question 3

why is it good that the septum separates the two sides of the heart?

Answer 3

• separates oxygenated + deoxygenated blood
• means you can have a higher pressure in left side vs right side of heart (higher pressure required to push blood round body vs just to the lungs)

Question 4

what does the cardiac cycle consist of?

Answer 4

systole = contraction
diastole = relaxation

Question 5

what are the three stages of the cardiac cycle?

Answer 5

atrial systole => ventricular systole => diastole
(sequence repeats after diastole)

Question 6

describe atrial systole

Answer 6

• AV valves are open (pressure in atria greater than pressure in ventricles)
• both atria contract (increases pressure in atria)
• blood forced into ventricles

Question 7

describe ventricular systole

Answer 7

• both ventricles contract increases pressure in ventricles
• blood forced into pulmonary artery/aorta
• AV valves close pressure in ventricles higher than in atrium
• semi-lunar valves open pressure in ventricles higher than in artery

Question 8

describe diastole

Answer 8

• atria and ventricles relax (pressure in aorta/pulmonary artery is greater than in ventricles)
• semi-lunar valves close
• AV valves open pressure in ventricles drops below pressure in atria
• blood flows into the atria and ventricles from the body and lungs

Question 9

MODEL ANSWER explain how the atrioventricular valve maintains a unidirectional flow of blood [2]

Answer 9

1. pressure in atrium is higher than in ventricle causing valve to open
2. pressure in ventricle is higher than in atrium causing valve to close
   OR
   pressure below valve is higher than above valve it closes

Question 10

how do you calculate cardiac output?

Answer 10

cardiac output = stroke volume x heart rate

Question 11

how do you calculate stroke volume?

Answer 11

stroke volume = cardiac output/ heart rate

Question 12

how do you calculate heart rate?

Answer 12

heart rate = cardiac output/ stroke volume

Question 13

units for the cardiac output equation?

Answer 13

• heart rate, number of beats per minute (BPM)
• stroke volume, volume of blood leaving left ventricle per heart beat (cm^3)
• cardiac output, volume of blood pumped per minute (cm^3min^-1)