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Neuroanatomy Exam 1 > Biochemistry - Metabolism of the Brain > Flashcards

Biochemistry - Metabolism of the Brain Flashcards

1
Q 
What is the function of:
   Oligodendrocytes
   Astrocytes
   Microglia
   Ependymal Cells
A

Oligodendrocytes: Produce myelin sheath in the CNS- provide structural framework
Astrocytes: Provide the metabolic support and protection
Microglia: Migratory cells that remove pathogens and cell debris by phagocytosis
Ependymal cells: Line ventricles and central canal. Involved in production and maintenance of CSF.

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2
Q

What are some substances that can pass through the BBB?

A
  • caffeine
  • Nicotine
  • Alcohol
  • Cocaine
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3
Q

When will penicillin but allowed to pass through the BBB?

A

When the brain is inflamed

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4
Q

What is a major glucose transporter into the brain and what allows it to function efficiently?

A

Glut 1 - BBB
Glut 3 - neurons in the brain
- a low Km allows for glucose to be taken up at all physiological glucose levels

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5
Q

What are the 4 types of amino acid transporters in the BBB?

A

1 - acid a.a. (ex. glu, asp)
2 - basic a.a. ( arg, lys, orn)
3 - neutral a.a. (gly, ala)
4 - neutral (bulky, hydrophobic - Phe, Tyr, Try)

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6
Q

How do sports drinks exploit a.a. receptors to help athletes?

A

They contain Branched Chain Amino Acids that compete for type 4 receptors with Tryptophan that would normally be responsible for serotonin and melatonin production that would produce whiny MR’ers.

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7
Q

What a.a. transporter is relavent in phenylketonuria?

A
  • a.a. type 4 transporter. Normally Phe competes with other a.a. for this transporter but higher levels (such as in PKU due to phenylalanine hydoxylase deficiency) would allow Phe to outcome for it.
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8
Q

What are the 4 products of tyrosine processing that are deficient in PKU?

What changes about the body’s need for tyrosine?

A
  • Tissue proteins
  • Melanin
  • Catecholamines
  • Fumarate / Acetoacetate
  • Tyrosine becomes essential. Phe competes with Tyr and Try for uptake by brain
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9
Q

What type of oder does PKU patient have?

A

Mousy oder

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10
Q

What are the 3 general function of the Blood Brain Barrier?

A
  • Regulation/control of transport of specific metabolites in and out of the brain
  • Protection from systemic fluctuation in molecules in neurotransmitters
  • Protection form potentially toxic substances (ex. billirubin)
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11
Q

What is the main sources of energy for the brain in fed/fasting state?
What is the energy required chiefly for?

A
  • Norm - glucose, starvation- ketone bodies. Does not catabolize fats for energy and there is a very small supply of glycogen.
  • Energy required chiefly for: Transport processes, synthesis of neurotransmitters.
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12
Q

When do Ketone bodies begin to get produced?

A
  • Gluconeogenesis depletes oxaloacetate in the liver which is normally needed for the TCA cycle and Acetyl CoA begins to accumulate. Acetyl CoA can change into ketone bodies.
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13
Q

When does Ketone bodies become a major source of energy?

A
  • about 1-1 1/2 days gluconeogenesis starts to decrease and ketones bodies become the main source to maintain glucose levels
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14
Q

Where does the glucose come from after free glucose is used up during starvation for the brain in acute hypoglycemia?

A
  • glucose comes from breakdown of glycogen in the liver for about 24 hours than the liver produces ketone bodies.
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15
Q

Glutamate is made from glucose via what intermediate of the Kreb’s Cycle?

A
  • a-ketoglutarate
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16
Q

What are some derivatives of glutamate?

A
  • GABA and glutathione ( is a component of the anti-oxidant system which is very important in the brain), and Glutamine (gets rid of ammonia)
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17
Q

What two brain processes is the Pentose phosphate pathway essential for?

A
  • Anti-oxidant system and lipogenesis
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18
Q

What are some other requirements for glucose?

A
  • Synthesis of glutamate and GABA
  • Synthesis of glutathione
  • Pentose phosphate pathway
  • Synthesis of acetyl choline
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19
Q

What are the two divisions and the different types of sphingosine?

A
  • Glycosphingolipids ( Cerebrosides, sulphatides, and ganliosides)
  • Sphingomyelin
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20
Q

What is the structure of a sphingomyelin?

A
  • The structure is a sphingosine and a fatty acid (the combo is called a ceramide), and a choline.
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21
Q

What is the structure of a Glycolipid?

A
  • Is a sphingosine and a fatty acid (ceramide) and a carbohydrate.
22
Q

What is the structure of Glucocerebroside and what disease is it’s accumulation relevant in?

A
  • Glucocerebroside is a ceramide and a glucose and it accumulates in Gaucher’s disease **
23
Q

What is the structure of Galactocerebroside and what disease is it’s accumulation relevant in?

A
  • Galactocerebroside is a ceramide and a galactose and it accumulates in Krabbe’s disease **
24
Q

What is a main feature of Tay-Sachs disease and what accumulates in it?

A
  • Cherry red spot on macula and gangliosides (ceramide oligosaccharides) accumulate.
25
Q

What accumulates in metachromatic leukodystrophy MLD?

A

Sulphatides (ceramide and a sulphated galactose)

26
Q

What is a general accumulation of sphingolipidoses?

A

Lipid substrate accumulation:

  • particularly in liver, spleen, and bone marrow.
  • Sometimes brain with consequent mental impairment
27
Q

What is the type of inheritance pattern for Fabry’s disease?

A
  • X-linked
28
Q

What is the deficient enzyme in Neimann-Pick disease and what is the accumulation?

A
  • Sphingomyelinase

- sphingomyelin

29
Q

What are the 6 sphingolipidoses that we need to know?

A

1) Gaucher
2) Tay-Sachs
3) Fabry
4) MLD
5) Krabbe
6) Niemann-Pick

30
Q

What is the accumulated substance in Gauchers?

A

glucocerebroside

31
Q

What types of Neimann-Pick disorder has to do with cholesterol accumulation?

A
  • Neimann-Pick (C&D) while Niemann-Pick (A&B) sphingomyelin
32
Q

What is a unique symptom missing from Type 1 Gaucher’s as opposed to the other sphingolipidoses?

A
  • Don’t get MR
33
Q

What are the symptoms of Gaucher type 1?

A
  • Hepatosphlenomegaly and MR. Crumpled tissue paper appearance of Gaucher cells
34
Q

What are the symptoms of Tay-Sachs?

A
  • MR, blindness, death in infancy. With a characteristic cherry red spot on macula.
35
Q

What are the symptoms of Niemann-Pick?

A
  • Hepatosplenomegaly (especially liver and spleen), MR, and cholesterol accumulation in types C and D have different etiology from A & B
36
Q

What are the symptoms of Fabry symptoms?

A

Skin rash, kidney failure

37
Q

What are the Krabbe disease?

A

Mental retardation, absence of myelin

38
Q

What are the 3 types of Gaucher disease variants?

A

Type 1 Non-neuronopathic (more common and very treatable) *
Type 2: Acute neuronopathic (patients don’t live past age 2 or 3, neuropathic) *
Type 3: incredibly rare

39
Q

What is the treatment for Sphingolipidoses?

A
  • Enzyme Replacement Therapy (administration of recombinant form of missing/defective enzyme. Can treat Gaucher type 1, Fabry’s, and Niemann-Pick Slide 57
40
Q

What is the potential problems with ERT?

A
  • Cost
  • Vascular access
  • Infusion - associated reactions
  • Antibody production
  • Lack of CNS penetration
41
Q

What is a potential alternative for ERT?

A
  • Oral administration of glucosylceramide synthase inhibitor. Inhibits production of glycosphingolipids (termed “substrate reduction”. Effective for Gaucher’s disease.
42
Q

What are the physical symptoms of Krabbe’s disease?

A
  • underdeveloped for age, reflexes hyperactive, suckling weak.
43
Q

What 2 types of deficiency are involved in megaloblastic anemia?

A

folate deficiency and B12 deficiency

44
Q

What is the accumulation in porphryria?

A

accumulation of propionylCoA or the accumulation of MethylmalonylCoA

45
Q

What might an accumulation of methylmalonyl CoA result in?

A

interference with myelin sheath formation. They essentially disrupt membrane structure through incorporation of methylmalonyl CoA producing branched fatty acids.

46
Q

By what reaction is ammonia removed from the system?

A

Ammonia is removed by from the brain by conversion of glutamate to glutamine via glutamine synthetase reaction

47
Q

What is a byproduct of producing glutamine from glutamate to get rid of ammonia from the body?

A
  • reduces ATP production, excess glutamine increases mitochondrial permeability.
48
Q

Overall what are the toxic effects of ammonia on the brain?

A
  • decrease ATP (removing of alpha-ketoglutarate)
  • cerebral edema
  • Depletion of glutamate and GABA
49
Q

What is the cause of acquired hyperammonemia?

What is the cause of hereditary hyperammonemia?

A
  • normally a consequence of liver disease

- Consequence of genetic deficiency of a urea cycle enzyme

50
Q

What 2 types of urea enzymes deficiency do we need to know?

A

Type I - carbamoyl phosphate synthesase I (autosomal recessive)
Type II- Omithine transcarbamoylase
(X-linked)

Neuroanatomy Exam 1 (4 decks)

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