Brain Metabolism

Question 1

oxygen flow to the brain is regulated by

Answer 1

neuronal activity and cerebral blood flow

Question 2

diagnostic functional imaging is done on what substrate

Answer 2

glucose

Question 3

how much of the bodys O2 consumption is done by the brain

Answer 3

20%

Question 4

what are the fuels of the brain?

Answer 4

glucose, and under prolonged fast ketone bodies

Question 5

where does the brain use its energy

Answer 5

to power Na-K ATPase which maintains membrane potential

Question 6

does the brain store glycogen?

Answer 6

yes very little

Question 7

below what level of glucose leads to brain dysfunction

Answer 7

<2-2.5mM

Question 8

how much energy is used by glial cells ?

Answer 8

17%-40%

Question 9

the brain has metabolic compartmentation, what does this mean?

Answer 9

presence in a tissue of more than one distinct

pool of a given metabolite.

Question 10

uses of compartmentation

Answer 10

Separate pools of a metabolite are not in rapid equilibrium with one another,
but rather maintain their own integrity and turnover rates.
• Compartmentation makes metabolism in the brain complex and continuous
interactions of neurons and glial cells essential for brain function.

Question 11

what makes up the blood brain barrier

Answer 11

• endothelium
• basement membrane
• astrocytes
• pericytes
• vasculr smooth muscle cells
• microglia

Question 12

what is the function of the blood brain barrier selectivity

Answer 12

To establish a stable ionic environment ensuring appropriate firing of neurons and
propagation of membrane potentials

Question 13

what can pass the BBB by passive diffusion

Answer 13

small molecules: H2O, O2
, CO2
, NH3
, ethanol
- soluble lipids: steroid hormones

Question 14

what can pass through carrier mediated transport

Answer 14

glucose using GLUT2 (insulin independant)

amino acids

Question 15

what role do astrocytes have in the BBB

Answer 15

• tightening of tight junctions (physical barrier)
• modulation of expression and polarized localization of transporters (transport barrier)
• controlling specialized enzyme systems (metabolic barrier)

Question 16

what are the major nutrient transporters in the BBB

Answer 16

GLUT1, MCT1 (monocarboxylc acid transporter)

Question 17

side note on MCT1

Answer 17

High amounts of MCT1 are present
in the brain microvasculature during
nursing/suckling, and decline
significantly after 14 days of age (in
the rat brain), with a concomitant
dramatic increase in the GLUT1
content.
• This phenomenon is paralleled by a
metabolic switch to glucose as the
predominant energy fuel of the
brain.

Question 18

levels of x and y increase with cerebral maturation and synaptogenesis

Answer 18

GLUT1 GLUT3

Question 19

in a neonate what does the brain use for metabolism?

Answer 19

ketone bodies

Question 20

what are ketone bodies?

Answer 20

the acetyl-CoA produced by fatty acid oxidation in liver mitochondria is
converted to acetone, acetoacetate and b-hydroxybutyrate (ketone bodies)
−These are transportable forms of fatty acids
−In starving state oxaloacetate is mainly used in gluconeogenesis, therefore acetyl
CoA produced by b-oxidation cannot enter TCA
−Source of fuel for brain, heart and muscle (major energy source for brain during
starvation)

Question 21

is succinyl-coA present in the liver

Answer 21

no

Question 22

an increase in glucose metabolism during brain maturation is accompanied by

Answer 22

increased oxidation of glycolytically derived pyruvate via the TCA cycle.

Question 23

in the brain, what is the % of glucose and oxygen extraction?

Answer 23

glucose: 10%
O2: 50-70%

Question 24

neurovascular coupling has 2 subsets

Answer 24

Cerebral autoregulation: ensures constant cerebral blood flow over a wide range of arterial
pressures (60-150 mmHg).
Functional hyperemia: ensures rapid delivery of oxygen and glucose to active neurons

Question 25

net uptake of glucose is x on plasma glucose concentration

Answer 25

independant, it is transported by facilitated diffusion. It has a significant tissue glucose [].

Question 26

is there glycogen in the brain?

Answer 26

• yes, very little
• glycogen granules are only present in the astrocytes of adult animals.
• glycogen phosphorylase in in astrocytes only

Question 27

brain glycogen metabolism is affected by

Answer 27

• vasoactive intestinal peptide, noradrenaline, insulin

Question 28

glycogen [] increases

Answer 28

s in conditions of decreased
electrical activity (e.g., deep pentobarbital anesthesia)

Question 29

glycogen [] and its enzymes are modulated by

Answer 29

sleep deprivation

Question 30

glycogen is needed for

Answer 30

maintaining intense firing in an isolated axon