Week 8: Coronary circulation

Question 1

What is the mass of the heart?

Answer 1

300 g

4% total body weight

Question 2

What is the flow rate of the coronary circulation?

Answer 2

150 ml/min

3%

Question 3

What is Vo₂ (oxygen uptake)

Answer 3

30 ml/ min

(250 ml O₂ / min)

Question 4

What is the capillary density of the coronary flow?

Answer 4

3000-4000 cap/ mm³

Question 5

AVDO₂ of coronary circulation

Answer 5

120 ml/l

arterial: 200 ml/ l
vein: 150 ml/l

Question 6

What type of organ is the heart

Answer 6

obligate aerobic organ

meaning: needs O₂ supply at all times

susceptible to O₂ limitations

Question 7

What is the result of the lack of collateral circulation in the coronary circulation?

Answer 7

• abrupt occlusion → ischemia
• slow occlusion → can develop collaterals

Question 8

What is the mechanical aspect of coronary circulation?

Answer 8

Ohms Law: Q= deltaP/R

R ~ 1/r⁴

Left ventricle: systole R↑↑↑ ⇒ Q↓↓↓

diastole R↓↓↓ ⇒ Q↑↑↑

Question 9

What is the systole time

Answer 9

.27 s

Question 10

What is the diastole time?

Answer 10

.53 s

Question 11

How is blood flow in the coronary circulation regulated?

Answer 11

1. Metabolic regulation
2. Autoregulation
3. Neurohumoral regulation

Question 12

What happens in the metabolic regulation of coronary circulation?

Answer 12

[O₂] ↓

[CO₂] ↑

[K+] ↑

[lactate] ↑

pH ↓

adenosine ↑

all lead to dilation

Question 13

What is the graph displaying autoregulation in coronary circulation?

Answer 13

Question 14

Describe the sympathetic part of the neurohumoral regulation in coronary circulation?

Answer 14

NE, E, adrenal

direct: alpha1 = constriction

beta2 = dilator

indirect: HR ↑

contractility ↑

⇕

↑↑↑ metabolism

dilation

Q↓

Question 15

Describe the parasympathetic part of the neurohumoral regulation in coronary circulation?

Answer 15

endothelial cells

mACHr → Ca²⁺ (NO reduction) → dilation → Q↑

Question 16

What is the weight of the brain?

Answer 16

1400g

Question 17

What is rate of the cerebral blood flow?

Answer 17

750- 850 ml/min

carotid: 2 x 330 ml/min
vertebral: 2 x 75 ml/min

Question 18

What is the V_O2 of the cerebral blood flow?

Answer 18

50 ml/min

Question 19

What kind of organ is the brain?

Answer 19

obligate aerobic organ for glucose and oxygen

Question 20

What would happen if we closed the arteries?

Answer 20

5 seconds = loss of consiousness

3 minutes = reversible

5 minutes = irreversible damage

Question 21

What is the volume of the intracranial compartment of the blood?

Answer 21

150 ml

Question 22

What is the volume of the intracranial compartment of the CSF?

Answer 22

150 ml

Question 23

What is the volume of the intracranial compartment of the IS?

Answer 23

75 ml

Question 24

What is the intracranial pressure?

Answer 24

5-13 mmHg

Question 25

What does the CBF depend on?

Answer 25

1. perfussion pressure 2. resistance

Question 26

What is the perfussion pressure?

Answer 26

deltaP = Pa - Pv deltaP = Pa- ICP deltaP ≈ 90 mmHg (ICP ↑ → deltaP → Q↓)

Question 27

What are the 4 components of the resistance in regards to cerebral circulation?

Answer 27

A.) Local control B.) CO₂ , O₂ in blood C.) Autoregulation D.) Neural control

Question 28

Discuss the A. (Local control) component of resistance

Answer 28

metabolic: [CO₂] → pH ↓ adenosine↑ [K+] ↑ [O₂] ↓ **local dilation** astrocytes: neural activity ↑ [Ca²⁺] **dilation** neuron: NO

Question 29

Discuss the D. (Neural Control) component of resistance

Answer 29

sympathetic innervation BP↑ autoregulatory curve shifted to autoregulatory range

Question 30

What is the graph displaying the PCO₂ v.s CBF

Answer 30

Question 31

What is the graph displaying the PO2 v.s CBF

Answer 31