Neuroanatomy Lecture #21: Transport W/in The Cns

Front 1

General differences btwn the CSF and the blood plasma:

• CSF less concentrations of these components (4)
• CSF has a higher concentration of this ion
• How does the pH differ and the molecular reason behind it

Back 1

General differences btwn the CSF and the blood plasma:

• it is lower in Protein, glucose, Na+ and Ca2+
• it has a higher [Cl-]
• CSF has a lower pH - the buffering capacity is lower due to the low [protein]

Front 2

List the 3 fluid ECF compartments of the CNS in order of decreasing volume

Back 2

Interstitial fluid, CSF and blood plasma

Front 3

Fxns of the CSF (5)

Back 3

• Buoyancy
• Shock absorption
• Chemical stability through nutrition and removal and metabolic waste
• Reduce ischemia
• Protection of the traction btwn nerves and vessels

Front 4

The Blood Brain Barrier:
• Groups of cells that comprise it (3)
• These cell types serve as the barrier
• It allows passage of these two major molecules
• These complexes prevent passage of substances via this route trans-/para-cellular which means substances must pass through in this direction trans-/para-cellularly

Back 4

The Blood Brain Barrier:
• Endothelial cells, Astrocyte endfeet and capillary basement membrane
• Capillary endothelial cells
• blood gases and gases
• Tight jxns, prevent passage paracellularly which means substance must pass transcellularly

Front 5

Transcellular Transport:
• Depends on this intrinsic property of molecules
• can be estimated by looking at this distribution ratio
• Significance of a high distribution ratio

Back 5

Transcellular Transport:
• Lipophilicity
• Oil/Water partition coefficient
• The higher the value, the more likely the substance will be able to cross the endothelial membrane

Front 6

Both Glucose and L-Dopa have low oil/water partition coefficients yet have a high rate of transfer from water to lips. How is this possible?

Back 6

Glucose and L-Dopa do not rely on passive diffusion through the BBB.

Both Glucose and L-Dopa also cross by facilitated diffusion, Glucose via Glut 1
L-Dopa via a system of carriers for neutral AAs

Front 7

How Glycine crosses the BBB and in what direction

Back 7

Glycine crosse from brain to blood using Na-dependent co-transport system, an example of 2ndry active transport

Front 8

Conditions that lead to the BBB becoming permeable (6)

Back 8

• Hypertension
• Hyperosmolarity of the blood
• Infection
• Trauma
• Ischemia
• Inflammation

Front 9

Circumventricular organs:
• def and their significance
• Name them (7)

Back 9

They are organs that surround the ventricle that lack tight jxns in their capillaries

- Posterior pituitary
- Neurohypophysis
- Median eminence
- OVLT
- Subfornical organ
- Subcommissural organ
- Area Postrema

Front 10

Two groups of ventricular lining including two differences btwn them and where they are found

Back 10

Group 1 cells - Specialized secretory ependymal cells formed from the choroid plexus. They have tight jxns to prevent paracellular transport and are found in some regions of the lateral, 3rd and 4th ventricles

Group 2 cells are ependymal cells that carry bundles of rapidly moving kinocilia. They have gap jxns and are found in most areas of the ventricular system.

Front 11

Group 1 Cells of the ventricles;
• are joined by these structures which allow only is kind of transport
• The different types of transporters located in the basal (3) and apical membranes (2)
• Both the basal and apical membranes share these transporters (5)
• The net result of their transport

Back 11

Group 1 Cells of the ventricles;
• are joined by tight jxns which allow only transcellular transport
• Basal membrane: Na+, K+ and Cl- cotransporters
Apical membrane: K+ and Cl- co-transporters
• Na+, K+, and Cl- ion channels, Na+/K+ pumps and Aquaporins (AQP 1)
• Na+, K+, Cl- and water move into the ventricles

Front 12

Describe the flow of CSF from the Lateral ventricles to the subarachnoid space and to the Superior sagittal sinus

Back 12

• CSF flows rostrally in the lateral ventricles and enters the 3rd ventricle through the IV foramen

• Using the cerebral aqueduct, it flows to the 4th ventricle

• It passes through the F. of Lushkas and Magendie, into the subarachnoid space

• After flowing over the surfaces of the brain and spinal cord, CSF is rerouted to the apex of the head and into the arachnoid granulations

• The granulations absorb and send it to the lumen of the superior sagittal sinus

Front 13

In Bacterial meningitis, describe the features of the CSF in terms of:

• The types of cells found
• [Protein] relative to normal (35 mg/dl)
• [Glucose] relative to normal (60 mg/dl)

• Also, which two molecules are elevated?

Back 13

• Cells in CSF: High WBCs (~1000/mm3)
• [Protein] = High (500 mg/dl)
• [Glucose] = Low (20 mg/dl)

Front 14

In Viral meningitis, describe the features of the CSF in terms of:

• The types of cells found
• [Protein] relative to normal (35 mg/dl)
• [Glucose] relative to normal (60 mg/dl)

Back 14

• Cells in CSF: High WBCs (~500/mm3) and increased lymphocytes
• [Protein] = High (500 mg/dl)
• [Glucose] = Normal (60 mg/dl)

Front 15

In a brain tumor/abcess, describe the features of the CSF in terms of:

• The types of cells found
• [Protein] relative to normal (35 mg/dl)
• [Glucose] relative to normal (60 mg/dl)

Back 15

• Cells in CSF: High lymphocytes (~500/mm3)
• [Protein] = High (500 mg/dl)
• [Glucose] = Normal (60 mg/dl), but can be lower in some tumors

Front 16

In Multiple Sclerosis, describe the features of the CSF in terms of:

• The types of cells found
• [Protein] relative to normal (35 mg/dl)
• [Glucose] relative to normal (60 mg/dl)

Back 16

• Cells in CSF: Elevated IgGs and increased T-lymphocyte count
• [Protein] = Normal (35 mg/dl)
• [Glucose] = Normal (60 mg/dl)

Front 17

In Guillain-Barre, describe the features of the CSF in terms of:

• The types of cells found
• [Protein] relative to normal (35 mg/dl)
• [Glucose] relative to normal (60 mg/dl)

Back 17

• Cells in CSF: <10 mononuclear leukocyctes/mm3
• [Protein] = Slightly high (>50 mg/dl)
• [Glucose] = Normal (60 mg/dl)

Front 18

In Subarachnoid hemorrhage, describe the features of the CSF in terms of:

• The types of cells found
• [Protein] relative to normal (35 mg/dl)
• [Glucose] relative to normal (60 mg/dl)

Back 18

• Cells in CSF: RBCs
• [Protein] = High
• [Glucose] = Normal (60 mg/dl)

Front 19

Two categories of hydrocephalus and two general feature shared by each

Back 19

Non-communicating and Communicating

Both lead to
- an increase in the size of the ventricles
- an increase in ICP

Front 20

Non-communicating hydrocephalus:
• Another term
• its cause
• common sites of blockage (3)
• These ventricles ALWAYS enlarge

Back 20

Non-communicating hydrocephalus:
• Obstructive hydrocephalus
• Blockage of CSF flow, CSF can't reach the subarachnoid space
• IV foramen, Cerebral aqueduct, Apertures of the 4th ventricle
• Lateral

Front 21

Communicating hydrocephalus:
• Another term
• its cause
• Possible etiology (2)
• These ventricles ALWAYS enlarge

Back 21

Communicating hydrocephalus:
• Non-obstructive hydrocephalus
• Impaired or blocked CSF absorption
• Possible etiology:
- Thickening of the arachnoid villi
- Tumors of the choroid plexus (papillomas) causing excess CSF production
• common sites of blockage (3)
• All of them do

Front 22

Normal Pressure Hydrocephalus:
• a feature it does not share w/ the other categories of hydrocephalus
• Condition with which it is associated
• Behavioral/Physiological changes (3)
• Anatomical changes (4)

Back 22

Normal Pressure Hydrocephalus:
• a feature it does not share w/ the other categories of hydrocephalus
• Condition with which it is associated
• Decreased cognitive ability, urinary incontinence and disturbances of walking
• The reduction in brain volume leads to: enlarged (ventricles, sulci & fissures) with cortical gyri flattening against the skull

Front 23

Intracerebral Pressure:
• As explained by the Monroe-Kellie Doctrine
• Normal range of ICP
• Method to measure ICP under normal conditions
- also, another term for "normal conditions" for measuring ICP
• Appropriate method to measure ICP when there is a tumor or obstruction of CSF
• ICP in relation to the Cerebral Perfusion Pressure

Back 23

Intracerebral Pressure:
• If a fluid compartment in the brain increases, there most be a corresponding decrease in another compartment or ICP will rise

• (5 - 15) mmHg
• Lumbar puncture
- equivalent pressure throughout the neural axis
• Intraventricular measurement
• CPP = Mean AP - ICP

Front 24

Brain Edema:
• Definition
• can be of these two origins, include definitions

• These cells can help regulate the initial swelling during the onset of damage

Back 24

Brain Edema:
• An excess accumulation of water in the intra- or extra- cellular spaces of of both the grey and white matter of the brain

• can be of these two origins
- Vasogenic: a disruption in the BBB causes the endothelial brain capillaries to be more permeable

- Cytotoxic edema: Caused by direct tissue damage or inadequate blood supply to neurons and glia causing insufficient oxygen and glucose delivery. The Na+/K+ ATPase can no longer fxn due to an absence of cellular energy leading to the dissipation of ionic gradients and cellular swelling

• Astroglial cells

Front 25

Congenital hydrocephalus is due to a deficit at this part of the ventricular system

Back 25

Due to blockage or developmental failure of the Cerebral aqueduct

Front 26

Dandy-Walker Syndrome:
• etiology
• conequence

Back 26

Dandy-Walker Syndrome:
• Failure of development of the 4th ventricle apertures (Lushka and Magendie)

• Dilation of all 4 ventricle

Front 27

Three conditions that can cause a rise of ICP

Back 27

Hydrocephalus, Tumor growth, intracerebral hemorrhage

Front 28

Three conditions that can cause subnormal ICP

Back 28

Head injury, dehydration failure of communication of the lumbar subarachnoid space with the cerebral space. The latter can be caused by a spinal tumor causing a communicating block of CSF movement

Front 29

Four general sx of ICP

Back 29

Nausea, bradycardia, increase in system blood pressure, and loss of consciousness

Front 30

Papilledema:
• Definition
• Explain how an increase in ICP can cause it

Back 30

Papilledema:
• swelling of the optic disc
• ICP can cause the optic disk to elevate and increased pressure in the subarachnoid space lying adjacent to the optic nerve