Cerebrospinal fluid and blood brain barrier

Question 1

The brain and the spinal cord are enveloped by 3 sheets of connective tissue called …

Answer 1

meninges

Question 2

What are the 3 meninges?

Answer 2

• Dura mater
• Arachnoid mater
• Pia mater

Question 3

Dura mater

Answer 3

• thick layers of fibroblast
• it fuses with the bone inner surface of the skull bone

Question 4

Arachnoid mater

Answer 4

• Spiderweb-like
• thin layer of fibroblast that trap CSF between it and Pia mater

Question 5

Pia mater

Answer 5

single layer of fibroblasts

Question 6

What is the cerebrospinal fluid?

Answer 6

is a clear fluid present in the:

• ventricles of the brain
• central canal of the spinal cord
• subarachnoid space (brain and spinal cord)

Question 7

What are the functions of the cerebrospinal fluid (CSF) ?

Answer 7

• to cushion the brain (buffering blows to the head)
• maintaining a consistent extracellular microenvironment for the neurons and glia cells
• waste control system for the removal of potentially harmful cellular metabolites
• Distribution medium for the peptide hormones and the growth factors that are secreted into the CSF

Question 8

Where is CSF produced?

Answer 8

in specialized ependymal cells in the choroid plexus located in each of the 4 ventricles (floor or roof) at a constant rate

Question 9

Where are the lateral ventricles located ?

Answer 9

respectively located in the two cerebral hemispheres

Question 10

Location of the third ventricle

Answer 10

found at the midline of the diencephalon.

Question 11

Location of the fourth ventricle

Answer 11

located between the cerebellum and the dorsal surface of the hindbrain (pons and medulla)

Question 12

The __________ consist of tufts of capillaries covered by _______________ that form a selective, tight-juction barrier to the secretions of the leaky capillaries and to other surrounding fluids (e.g. CSF, extracellular fluids)

Answer 12

plexus, ependymal cells

Question 13

relevant processes in regards to the plexus and what it does:

Answer 13

• active transport of sodium ions (Na+) and chloride (Cl-) into the ventricles
• water flows the NaCl passively into the ventricles
• Metabolization of some potentially harmful waste products

Question 14

CSF flows down a pressure gradient from its site of formation at the _____________ through the ventricular system and the subarachnoid space into the venous system.

Explain the order of that flow

Answer 14

• Choroid plexus

1. lateral ventricles
2. into the third ventricle through the interventricular foramina (foramina of monro)
3. through the cerebral aqueduct (aqueduct of Sylvius) of the midbrain
4. into the fourth ventricle
5. into the subarachnoid space through the foramina of Luschka

Question 15

CSF can be sample by placing a stilettoed spinal needle where ?

Answer 15

into the subarachnoid space.

• in most veterinary species between the skull and the first cervical vertebra (atlas) in anesthetized animals.

Question 16

How is normal CSF suppose to be?

Answer 16

clear and translucent

• turbidity indicates increased cellularity
• pink tint suggest the presence of blood

Question 17

Where does the absorption of the CSF into the venous system take place ?

Answer 17

in the dura-lined venous sinuses within the skull

Question 18

Most of the fluid is absorb from the subarachnoid space into the _______________ through _______________.

Answer 18

dural sinuses, arachnoid villi

Question 19

What are arachnoid villi?

Answer 19

small, fingerlike projections of the arachnoid membrane that poke through the walls of the sinus.

Question 20

Absorption appear to be _________ dependent and is ______________.

Answer 20

pressure, unidirectional

Question 21

The entire volume of CSF is replaced ____________ times a day.

Answer 21

several

Question 22

Hydrocephalus

Answer 22

Increased CSF volume in the skull, often associated with an increased ventricular volume and increased intracranial pressure

Question 23

Non-communicating hydrocephalus

Answer 23

Normally caused by an obstruction to CSF flow ( narrow cerebral aqueduct or blocked exits from the fourth ventricle.

• this causes the ventricular regions inside the brain to expand at the expense of the surrounding brain tissue, and intracranial pressure rises

Question 24

Communicating hydrocephalus

Answer 24

Impairment of absorption (can be secondary to meningitis or hemorrhage)

• this can increase CSF volume in the subarachnoid space, which increases pressure on the outside surface of the brain and increases intracranial pressure.

Question 25

The blood brain barrier consist of specialized capillary endothelial cells that are lined by the:

Answer 25

• basal lamina
• astrocytic endfeet
• pericytes
  -microglial cells

Question 26

In ___________, passage through ______________ is blocked by tight junctions, and exchange of blood solutes is highly selective.

Answer 26

brain capillaries, intercellular clefts

Question 27

Blood brain barrier histological characteristics

Answer 27

• few or no fenestrations
• pinocytes very uncommon to observe at the BBB
• tight junctions
• luminal and abluminal side of the endothelium (polarized)
• specific carrier systems for the uptake of solutes
• Endothelium is surrounded by pericytes and astrocytes

Question 28

BBB functional characteristics

Answer 28

• Molecules that are small, uncharged, lipid soluble, and unbound to plasma proteins (O2, CO2, ethanol, nicotine) can easily pass across the capillary endothelium of the BBB
• Molecules that don’t fit this profile (glucose, some amino acids) are able to pass through the BBB by specific, carrier-mediated transport mechanisms
• Many antibiotics, anti parasitic drugs, as well as various potentially harmful substances will be “repelled” by the BBB (carrier-mediated process) and will never reach the nervous system

Question 29

Pgp: MDRs (Multidrug Resistance Protein) is an example of what ?

Answer 29

One of many transport systems in the BBB.