Cardiac Cycle And Metabolism

Question 1

Draw the pressure volume loop- label the events of A-F

Answer 1

A- diastole, mitral valve is open (left)
B- slight pressure dip
C- mitral valve closes, inc pressure as atria squeeze
C to D- isovolumetric contraction, aortic valve closed
D- aortic valve opens
D to E- rapid ejection phase
E- change from rapid ejection to slow ejection
E-F- slow ejection phase
F- aortic valve closes
F to A- isovolumetric relaxation

Question 2

What is the left ventricle volume at EDV and ESV

Answer 2

ESV- 50mL
EDV- 120mL

Question 3

What phase of pressure-volume loop is most important for old people

Answer 3

slight increase in pressure as the atria squeeze rest of blood into ventricle before mitral valve closes at C

Question 4

Equation for ejection fraction and standard %

Answer 4

Ejection fraction= SV/EDV
Normal = 55%
Low = <50% (pump compromised)

Question 5

Calculate rest stroke volume and provide equation

Answer 5

SV= EDV - ESV = 120-50= 70mL
70mL blood leaves the left ventricle at rest

Question 6

Calculate pulse press, provide equation

Answer 6

Pulse pressure = systolic - diastolic = 120 mm Hg - 80 mm Hg
Pulse pressure = 40 mm Hg

Question 7

What causes the pressure difference in the heart

Answer 7

Contraction

Question 8

Put the ECG complexes onto the pressure-volume loop

Answer 8

P- atria depolarization= just before C, atrial contraction right before atrial kick (slight pressure increase)
QRS- ventricle depol= Start at C
T- ventricle repolarization- at E

Question 9

What elements of heart crest the sounds?

Answer 9

1- closure of mitral valve
2- closure of aortic valve
3/4- can’t hear

Question 10

What is the dicrotic notch

Answer 10

Brief increase in pressure of aorta
Caused by closure of aortic valve, elastic recoil of aorta (turbulence in aorta)

Question 11

What is the name given to the pressure increase in aorta

Answer 11

Dicrotic notch

Question 12

What happens if you increase the preload? How does this change the pressure-volume loop

Answer 12

Inc volume, inc stretch, inc length, inc tension, INC STROKE VOLUME (frank-starling)
C to D shift right (larger volume)
E shift up and right (longer ejection)
B shift right (larger SV)

Question 13

What happens if you increase the afterload? How does this change the pressure-volume loop

Answer 13

Inc pressure to open aortic valve, inc isovolumetric contraction time, early closing of aortic valve, inc ESV, DECREASE STROKE VOLUME
A- larger ESV, shift right
B- shift right (but not larger SV because A also shifted)
D- endpoint shift up, need more time to build pressure before opening aortic valve since afterload increased
E- shift up
F- shift right (close earlier, inc pressure in aorta, more volume left), shift up
(larger pressure to overcome)

Question 14

What happens if you increase the contractility? How does this change the pressure-volume loop

Answer 14

Inc contractility, inc force contraction, inc max systolic pressure, dec ESV, INCREASE STROKE VOLUME
F to A- shift left, more blood gets out
B- shift left
C to D- stays same, no volume increase (no change in preload)
E- shift left and up (longer rapid ejection)

Question 15

How can we increase cardiac work

Answer 15

Increased work requires increased ATP
- requires increased oxygen
- therefore increase coronary artery blood supply
heart is aerobic organ (needs oxygen)

Question 16

How does the heart produce ATP?

Answer 16

70-90% free fatty acids
Fat is main reliable fuel source
Others include glucose, glycogen, lactate

Question 17

How does skeletal muscle produce ATP

Answer 17

5% free fatty acids
Glucose metabolism is dominant
Note skeletal can work anaerobically, unlike the heart

Question 18

How is the heart designed for fat use?

Answer 18

1. High expression of FABP- fatty acid binding protein
2. High expression of CAT- in mitochondrial matrix, regulate what fuel is used in mitochondria to generate energy
3. High number of mitochondria

Question 19

Explain cycle used in heart to generate energy

Answer 19

FABP -> fatty acid activation (-2 ATP expense) -> acyl chain + coA (18-C) coA allows entry into mitochondria -> mitochondria breaks down chain, acetyl coA enters citric acid cycle and produces energy

Question 20

Explain beta oxidation

Answer 20

Fats are broken down by beta oxidation to produce energy
18-C (acyl chain) breaks into acetyl coA (2-C x9) which produces ATP. 2-C enters citric acid cycle and produces ATP. Electron transport chain produces ATP. Total ATP 134 (large)

Beta oxidation occurs in mitochondria, needs oxygen to occur

Question 21

Regulation of glucose metabolism

Answer 21

1. Glucose uptake- concentration gradient, insulin increases GLUT4
2. Enzymatically- PDH vs LDH choice is determined by the presence of O2
3. High beta-oxidation of FFA suppresses glucose metabolism

Question 22

Glycolysis pathway

Answer 22

Glucose -> glucose-6-phosphate -> 2 trios phosphate -> 2 pyruvate -> lactate

Pyruvate-lactate= 2 ATP generation
Pyruvate can convert to acetyl coA which enters citric acid cycle

Question 23

What does glucose metabolism vs fat metabolism show

Answer 23

Fat 134 ATP
Glucose 36 ATP
fat has more ATP yield

Question 24

Explain Lactate metabolism

Answer 24

Lactate to pyruvate (lactate dehydrogenase)
1. Lactate co-transporter
2. Cardiac specific LDH that allows production of pyruvate