Energy and Blood Flow in the brain L2.2

Question 1

what is the energy currency of the brain and how is energy released from it?

Answer 1

• the energy currency of the brain is ATP (adenosine triphosphate)
• hydrolysis releases the third phosphate group,resulting in ADP and Pi which also releases free energy

Question 2

how is ATP manufactured in the brain?

Answer 2

ATP is manufactured from fatty acids,ketone bodies and glucose

Question 3

does the brain store a lot of glycogen?

Answer 3

No, the brain stores very little glycogen

Question 4

compare and contrast aerobic and anaerobic glycolysis

Answer 4

• Aerobic = breaks down glucose ( glucose → pyruvate → ATP) is slow, but produces 36 ATP via the TCA cycle.
• Anaerobic = produces very little ATP(2) + lactate.its much faster than aerobic

Question 5

How does the brain obtain its energy?

Answer 5

the brain gets most of its energy from oxidative glycolysis
- this is because aerobic glycolysis is much more efficent at ATP production, and brain needs ‘ real-time’ replenshment of energy from the arterial blood supply as it does not have large energy stores

Question 6

describe the brains consumption of blood and oxygen

Answer 6

the brain consumes approx 20% of all available arterial blood and 20% of available oxygen.this is alot compared to its mass

Question 7

Why are functional neuroimaging techniques that are sensitive to blood flow or metabolism useful for studying brain activity?

Answer 7

techniques can be used to make interferences about brain activity because increases in neuronal activity are always accompanied by a local increase in regional CBF (cerebral blood flow )

Question 8

What is the significance of the brain’s vascular density?

Answer 8

brain has a high vascular density,accounting for 20% of the entire blood volume which allows for the close proximity of blood vessels to cells and enough oxygen and nutrient delivery

Question 9

What is neurovascular coupling?

Answer 9

is the process by which local CBF is regulated by neural activity
- involves the release of vasoactive substances from glial cells such as k+ ions, adenosine and NO(nitric acid) that act on the smooth muscle of nearby arterioles to regulate blood flow

Question 10

what is the role of astrocytes in the control of blood flow?

Answer 10

astrocytes play a role in both vasodilation and vasoconstriction
- they release vasodilators like arachidonic acid and also involved in the reuptake of k+, a potent vasodilator.

Question 11

What does “paradoxically” mean in the context of brain activity and oxygen extraction?

Answer 11

oxygen extraction fraction decreases despite increased neuronal activity, which seems counterintuitive.

Question 12

How does the oxygen extraction fraction (E) change with increased neuronal activity?

Answer 12

The oxygen extraction fraction (E) decreases with increases in neuronal activity.

Question 13

What is the formula for oxygen extraction fraction (E)?

Answer 13

E = (oxygen consumed) / (oxygen delivered).

Question 14

What happens to the concentration of deoxyhemoglobin during increased neuronal activity?

Answer 14

Increased neuronal activity leads to a decrease in the concentration of deoxyhemoglobin in the venous space.

Question 15

when brain cells are active they need more 02 but even though they’re using more 02, the 02 extraction factor (E) goes down, why?

Answer 15

• more blood flow to active brain area bringing in more 02
• this extra 02 reduces the amount of dHb in veins
  since there’s less dHb now the fraction of 02 being extracted from the blood appears to be lower