30 Coronary and cerebral circulation

Question 1

____________ store blood
temporarily during diastole in the heart ; this blood is released into coronary capillaries during the initial phase of systole.

Answer 1

Precapillary sinuses (PS)

Question 2

_________ drain venous blood

from coronary circulation into cardiac chambers. They are independent of the capillary bed.

Answer 2

Thebesian vessels

Question 3

Where does most of the coronary venous blood drain to? Via?

Answer 3

Right atrium

Via coronary sinus

Question 4

When does the highest LEFT coronary flow occurs in?

Answer 4

early diastole

just being freed from compression

Question 5

When does the RIGHT coronary flow is highest ?

Answer 5

during systole

Question 6

When is the compression of the coronary vessels most significant?

Answer 6

When the cardiomyocytes are contracted but the cardiac chamber volume is kept constant i.e. during isovolumetric contraction.

Question 7

When does the coronary flow resume? What will happen to the diameter of the vessels? Why?

Answer 7

Diastole,

Vasodilation, due to buildup of metabolic by-product (reactive hyperemia)

Question 8

What is the difference between active and reactive hyperemia?

Answer 8

Active hyperemia is the increase in organ blood flow (hyperemia) that is associated with increased metabolic activity of an organ or tissue.

Reactive hyperemia is the transient increase in organ blood flow that occurs following a brief period of ischemia (e.g., arterial occlusion).

Question 9

Increase in wall stretch triggers vasoconstriction of coronary vessels to dampen the change in flow rate. This is regulated by _________.

Answer 9

Myogenic regulation in autoregulation

Question 10

Which plays the most important role in coronary blood flow?
A. Myogenic regulation
B. Metabolic regulation
C. Sympathetic regulation

Answer 10

B

C is minor

Question 11

What does increased myocardial O2 consumption suggest in coronary blood flow?

Answer 11

increase in flow, active hyperemia

Question 12

_______ release is increased in ischaemic conditions, which further promotes vasodilation as it promotes the release of __________.

Answer 12

Adenosine;

NO

Question 13

State the 2 ways that sympathetic stimulation control coronary blood flow.

(although it is minor to metabolic control)

Answer 13

1. on heart: b1 receptors, trigger the increase in heart rate and contractility > more metabolic by products > coronary vasodilation due to active hyperemia
2. on vessels directly: a1 mediated vasoconstriction and b2 mediated vasodilation

Question 14

What is glyceryl trinitrate? What is the effect by Glyceryl trinitrate on collateral vessels?

Answer 14

A NO donor;
it only causes vasodilation in collateral vessels
thus the ischemic area will receive more blood

slide 13

Question 15

Which parts of the brain does basilar artery supply to?

Answer 15

Cerebellum, midbrain and pons

Question 16

Venous sinuses collect blood from the brain and drain all into ____________.

Answer 16

Internal jugular veins

Question 17

The brain has the highest O2 consumption rate despite it only receives ______% of cardiac output.

Answer 17

15

Question 18

loss of consciousness occurs when flow rate drops to ____

mL/min (all per 100 g); irreversible brain damage at ____ mL/min

Answer 18

20;

10

Question 19

Which of the following is incorrect?
A. The brain has high dependence on glucose oxidation as energy source
B. The brain is very sensitive to changes in metabolic by-products
C. Sympathetic stimulation plays a very important role in overall vasoconstriction in cerebral arteries
D. Coronary blood flow is pulsatile in large vessels

Answer 19

C
just a minor role
(metabolic control is the most important)

Question 20

When there is a change in cerebral perfusion pressure, ________ response will be triggered.

Answer 20

Myogenic

Question 21

Suggest metabolites that will cause active hyperemia in the brain.

Answer 21

CO2, H+, K+ and adenosine