Lecture 8 9/5/23 Flashcards

1
Q

What are the characteristics of normal cerebrospinal fluid?

A

-clear and colorless
-small amount of protein
-few lymphocytes
-very similar to water

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2
Q

How can disease impact CSF?

A

increase the amount of protein and/or lymphocytes in the fluid

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3
Q

What are the ventricles in the brain?

A

-2 lateral
-3rd
-4th

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4
Q

What structure allows the 3rd ventricle to drain into the 4th ventricle?

A

mesencephalic aqueduct

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5
Q

What is the role of the lateral apertures of the 4th ventricle?

A

allow CSF to drain into the sub-arachnoid space

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6
Q

If the CSF doesn’t drain from the 4th ventricle into the sub-arachnoid space, where does it go?

A

central canal of the spinal cord

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7
Q

What is the function of the choroid plexus?

A

produce CSF

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8
Q

What are the characteristics of CSF production?

A

-occurs in each ventricle
-by-product of brain metabolism
-constant production
-involves active transport of Na+ (needs energy!)

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9
Q

How does the choroid plexus produce CSF?

A

-choroid plexus is very vascular
-blood flows into choroid plexus and is filtered
-excess serum fluid becomes CSF

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10
Q

Which enzyme is involved in CSF production?

A

carbonic anhydrase

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11
Q

How does the CSF flow?

A

-rostrally to caudally
-from lateral ventricles, to 3rd ventricle, to 4th ventricle and out

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12
Q

What causes the CSF to flow?

A

pulsation of blood in the choroid plexus with each heart beat

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13
Q

Where is CSF reabsorbed?

A

in the sub-arachnoid space

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14
Q

What structures allow for reabsorption of CSF?

A

arachnoid villi

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15
Q

How do arachnoid villi allow for reabsorption of CSF?

A

-arachnoid villi protrude up into venous sinus
-when pressure increases, villi act as one way valve and allow CSF out into bloodstream
-one way valve prevents blood flow into CNS

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16
Q

What are the functions of CSF?

A

-cushion the brain
-pressure regulation
-source of nourishment/waste removal
-chemical buffer

17
Q

What is hydrocephalus?

A

dilation/enlargement of ventricular system caused by obstruction of CSF flow

18
Q

Why do toy breeds often present with an “enlarged head?”

A

-they have a genetic brain malformation causing a CSF flow blockage
-enlarged ventricles prevent skull sutures from closing properly

19
Q

What are the clinical signs of hydrocephalus?

A

-behavior changes
-ataxia
-seizures
-altered mentation
-enlarged, dome-shaped skull
-persistent fontanelle/soft spots

20
Q

What is a ventriculoperitoneal shunt?

A

-a tube that inserts into the ventricular system and the abdomen to drain CSF
-one-way valve on the tube allows for drainage when pressure is too high

21
Q

Why can sulci not be seen on MRI in an animal with hydrocephalus?

A

the pressure from the dilated vesicles presses on the CSF in the sulci and prevents them from being seen on MRI

22
Q

What is the blood-brain barrier?

A

selective barrier between systemic circulation and central nervous system

23
Q

Why does the BBB exist?

A

there is a lot of stuff in blood that we do not want to allow into the CNS

24
Q

What are the components of the BBB?

A

-tight junctions between the cells of the capillary walls
-thick basement membrane surrounding endothelial cells
-layer of foot processes from astrocytes providing extra support

25
Q

What substances is the BBB highly permeable to?

A

-water
-CO2
-O2
-most lipid soluble substances

26
Q

What substances is the BBB slightly permeable to?

A

electrolytes

27
Q

What substances are unable to permeate the BBB?

A

-plasma proteins
-most non-lipid soluble and/or large organic molecules

28
Q

Why is the permeability of the BBB an issue when treating infections?

A

the BBB does not let therapeutic levels of some antibiotics enter the CNS

29
Q

What happens when proteins enter the brain during infection/tumor?

A

-the proteins pull water with them
-leads to brain swelling

30
Q

What areas of the brain lack the BBB?

A

-hypothalamus
-area postrema
-pineal gland
-choroid plexus

31
Q

Why do some areas of the brain lack the BBB?

A

in order to monitor what is going on in the blood and respond accordingly

32
Q

How is CSF collected for testing?

A

spinal tap