6 - Metabolism, CSF, Barriers

Question 1

Normal rate of CBF

Answer 1

750-800 mL/min which is 40-55 mL/min/100gm

Question 2

CBF rate for irreversible brain damage

Answer 2

<15mL/100g per min (really, <20 for several minutes+)

Question 3

Total CSF Volume

Answer 3

135-150 mL

Question 4

Stroke

Answer 4

Lesion due to interruption of blood supply

Question 5

Four mechanisms to regulate CBF

Answer 5

1. Autoregulation (homeostasis)
2. Metabolic Factors (CO2)
3. Neurogenic Factors
4. Blood Viscosity

Question 6

Impaired CBF autoregulation:

1. Arteriosclerosis =
2. Old age =
3. Epilepsy =

Answer 6

1. Arteriosclerosis = decreased CBF
2. Old age = decreased CBF
3. Epilepsy = increased CBF

Question 7

CBF Autoregulation:

1. Increased BP =
2. Decreased BP =

Answer 7

1. Increased BP = vasoconstriction
2. Decreased BP = vasodilation

Question 8

Issues when BP is over threshold:

Answer 8

1. Vessel damage
2. Edema
3. Raised ICP

Question 9

Metabolic Factors in CBF

Answer 9

1. CO2
   
   1. Increased = increased CBF
2. O2
   
   1. Incresed = decreased CBF (inverse)
3. pH
   
   1. Low = increased CBF (inverse)

Question 10

CBF in PET

Answer 10

Glucose utilization

Question 11

CBF in SPECT

Answer 11

Blood flow

Question 12

CBF in fMRI

Answer 12

Blood oxygen levels

Question 13

Neurogenic Factors in CBF

Answer 13

• Sympathetic postganglionic stimulation from superior cervical ganglion causes vasoconstriction of arteries
• Also, some postganglionic parasympathetic fibers from pterygopalatine ganglion (CN VII) provide a vasodilatory innervation to the larger cerebral arteries

Question 14

Blood Viscosity and CBF

Answer 14

• Inversely proportional
• Polycythemia (increased hematocrit) = decreased CBF
• Anemia = increased CBF

Question 15

CSF Travel

Answer 15

1. Lateral ventricle
2. Interventricular foramen (of monro)
3. 3rd ventricle
4. Cerebral acqueduct
5. 4th ventricle
6. One of 3 subarachnoid spaces:
   
   • Foramen of Luschka (one for each hemisphere)
     
     • Then ventral pontine cistern
   • Foramen of Magendie (single)
     
     • Then dorsa cisterna magna
7. Subarachnoid Granules
8. Dorsal Venous Sinuses

Question 16

CSF Function

Answer 16

• Maintains constant environment for neurons. glia
• Functional waste clearance
• Allows brain to float, provides cushion
• Protects, routes hormones
• Homeostasis

Question 17

CSF is produced by ______ cells in the _________

Answer 17

Ependymocytes, choroid plexus

Question 18

CSF-Blood Barrier

Answer 18

Tight junctions made by ependymocytes in the choroid plexus ensures that blood doesn’t make contact with CSF in ventricles

Question 19

Important Cisterns

Answer 19

1. Cisterna Magna (from foramen of Magendie)
   
   1. Cisterna qudrigeminal (superior)
2. Pontine cistern
   
   1. Basal cistern
      
      1. Cistern of the lateral fissure (brings everything to the top)
      2. Cisterna ambiens (connects superior and basal cistern)

Question 20

Answer 20

A) Cisterna Ambien

B) Basal Cistern

C) Pontine Cistern

D) Cisterna Magna

E) Superior (quadrigeminal) cistern

*Cistern of lateral fissure not pictured)

Question 21

3 ways to cross Blood- CSF or Brain Barrier

Answer 21

1. Diffusion of lipid-soluble substances
2. Receptor-mediated transport (proteins)
3. Ion channels