5 – CSF and BBB

Question 1

Cerebrospinal fluid (CSF):

Answer 1

-clear fluid that surrounds the brain and SC

Question 2

What is the function of the CSF?

Answer 2

-buoyancy
-cushion the brain and SC form injury
-prevention of ischemia
-nutrient delivery and waste removal for CNS

Question 3

Where is CSF manufactured?

Answer 3

-in areas of brain called ventricles
-absorbed by the blood stream
*continuously being manufacture

Question 4

What is CSF derived from?

Answer 4

-blood plasma
>content is similar
-ideally zero RBCs and very few WBCs
*very few proteins and cells are present

Question 5

Hydrocephalus:

Answer 5

-an increased volume in the brain ventricles
>connections can get plugged as they are really little
Ex. brain tumors (can’t drain the CSF out of the brain)

Question 6

How does hydrocephaly occur?

Answer 6

-no connective tissue within
-very little ECS
-no to little lymphatics
*all normal mechanisms for dealing with excess fluid is ABSENT in CNS

Question 7

CNS held within a confined space:

Answer 7

-brain within in skull
-SC within vertebral canal
*doesn’t allow for much expansion in tissues

Question 8

Even a slight accumulation of fluid in CNS can:

Answer 8

-increase the pressure surrounding tissue enough to cause damage

Question 9

Telencephalon makes which ventricles?

Answer 9

-lateral ventricles

Question 10

Diencephalon makes which ventricle?

Answer 10

-third ventricle
>circular shape around the thalamus

Question 11

Metencephalon makes which ventricle?

Answer 11

• mesencephalic aqueduct

Question 12

Myelencephalon makes which ventricle?

Answer 12

-fourth ventricle
>with lateral projections

Question 13

Spinal cord makes the:

Answer 13

-central canal

Question 14

Ventricular system is lined with:

Answer 14

-ependymal cells
>usually smooth surface, few areas more complex=choroid plexus
>ciliated cells: helps with movement of CSF through the ventricular system

Question 15

Choroid plexus:

Answer 15

-where the CSF is produced
-junction of ependymal cells and blood vessels
*blood-CSF barrier

Question 16

Ependyma invaginates in 4 locations=creates 4 plexi:

Answer 16

-lateral ventricle (x2)
-roof of III ventricle (mesencephalon)
-roof of IV ventricle (metencephalon/myelencephalon)

Question 17

Choroid plexus ‘characteristics’:

Answer 17

-simple cuboidal epithelium with increased blood supply
-fenestrated capillaries allow for movement of molecules from blood to CSF
-tight junctions in ependyma (passive and active transfer)
*everything must move through the ependyma

Question 18

Everything must move through the ependyma:

Answer 18

-Bi-directional flow from capillaries to ventricles
>transport of nutrients (glucose, oxygen, vitamins, ions)
>waste and unnecessary solutes absorbed

Question 19

Compared to blood, CSF composition

Answer 19

-increased H2O (99% vs. 93%)
-slightly less glucose (although ependymal cells have lots of glucose transporters present)
-far fewer proteins
-slightly more acidic (b/c there are less proteins to buffer)
-acellular (under normal

Question 20

CSF is continually produced:

Answer 20

Replaced 4-5x daily

Question 21

How is CSF production regulated?

Answer 21

-via pressure gradients (osmotic pressure) + ANS
-when CSF pressure is high=decrease in CSF production

Question 22

How does CSF move?

Answer 22

-via ciliated cells and pressure gradients
*rate of flow is influenced by rate of production

Question 23

What is the clinical significance of CSF production? (example)

Answer 23

-hypertonic blood=decreased CSF production

Question 24

What could you do if an animal has a head trauma (brain swelling)?

Answer 24

-reduce CSF and intracranial pressure by giving patient hypertonic saline or mannitol (20%)
>adding big molecules into the blood system which draws the water out of the ventricles into the blood stream=shrinking ventricles=creating more space

Question 25

What is the CSF movement through the ventricles?

Answer 25

-lateral ventricles
-III ventricle
-mesencephalic aqueduct
-IV ventricle
-central canal
*typically, CSF flows rostral to caudal

Question 26

What happens to some of the CSF in the IV ventricle?

Answer 26

-flows out of lateral apertures of IV ventricle into subarachnoid space

Question 27

Arachnoid has:

Answer 27

-long thin trabeculae, creating a space within the meningeal layer
>space within trabeculae=subarachnoid space

Question 28

Subarachnoid space surrounds:

Answer 28

-the entire CNS
*filled with CSF

Question 29

Reabsorption of CSF:

Answer 29

-subarachnoid space has villi that go into sinuses of dura

Question 30

Where can we collect CSF in animals?

Answer 30

-cervical spinal puncture
>cerebellomedullary cistern
-lumbar spinal puncture
>lumbar cistern (ex. L5, very caudal end of SC after it has ended)
*must be kept cold and looked at within 30mins

Question 31

Where do blood vessels of the BBB initially start?

Answer 31

-in the meninges
-then dive into deeper CNS tissues

Question 32

Astrocytes:

Answer 32

-ALWAYS surrounding the vasculature in the CNS
-create a glial limiting membrane
>induce endothelial cells to make tight junctions to regulate flow of molecules
>most part: it is a unidirectional flow

Question 33

Pericytes:

Answer 33

-provide support to endothelial cells
-paracrine signalling
-important for development of CNS vasculature

Question 34

BBB protects the CNS from:

Answer 34

-many substances and cells
-keeps out circulating immune cells, toxins, pathogens, most viruses, and drugs
>some drugs can penetrate the BBB (Ex. heroin)