The ventricular system and circulation of cerebrospinal fluid

Question 1

What does a ventricle mean?

Answer 1

• small cavity/chamber

Question 2

How do ventricles form?

Answer 2

• forms from the neural canal
• neural canal dilates within the prosencephalon, leading to the formation of the lateral ventricles and third ventricle

Question 3

What is the purpose of the ventricles?

Answer 3

• to produce and circulate CSF

Question 4

Neurolation is the formation of the neural plate, which then bends up and later fuses to form the hollow tube that will eventually differentiate into the brain and the spinal cord of the central nervous system. In the image below, label the items numbered 1-3 using the labels below?

• neural crest
• neural plate
• notochord

Answer 4

1 - notochord

2 - neural plate

3 - neural crest

Question 5

The neural crest cells begin to seal the remaining space at the cranial (top) and caudal (bottom) ends of the neural tube, what are the ends called and what can happen if these are not sealed correctly?

1. neuropores and can cause congenital abnormalities (spina bifida/anencephaly)
2. nanapores and can cause congenital abnormalities (spina bifida/anencephaly)
3. neural ends and can cause congenital abnormalities (spina bifida/anencephaly)
4. caudal pores and can cause congenital abnormalities (spina bifida/anencephaly)

Answer 5

1. neuropores and can cause congenital abnormalities (spina bifida/anencephaly)

Question 6

What is spina bifida?

Answer 6

• neural tube fails to seal correctly at the caudal end and there is no skin, can be:

1. • occulta = vertebral arch defects (not able to be seen as in the latin name
2. • cystica = meninges (and sometime the nerves) project out of vertebrae

Question 7

What is anencephaly?

Answer 7

• where the neural tube has not sealed correctly at the cranial end
• a serious birth defect in which a baby is born without parts of the brain and skull

Question 8

What do the neural crest cells associated with the nervous system go on to develop?

Answer 8

• PNS

Question 9

The neural tube will develop into the CNS. What are the 3 primary vesicles called?

1. diencephalon, prosencephalon, mesencephalon
2. rombencephalon, prosencephalon, mesencephalon
3. diencephalon, prosencephalon, mesencephalon
4. telencephalon, prosencephalon, mesencephalon

mesencephalon

Answer 9

2. rombencephalon, prosencephalon, mesencephalon

• Prosencephalon (forebrain)
• Mesencephalon (midbrain)
• Rombencephalon (hindbrain)

Question 10

The neural tube will develop into the CNS. There are 3 primary vesicles called the Prosencephalon (forebrain), Mesencephalon (midbrain) and the Rombencephalon (hindbrain). What are the secondary vesicles these will go on to develop?

Answer 10

1 - telencephalon (Prosencephalon)

2 - diencephalon (Prosencephalon)

3 - mesencephalon (Mesencephalon)

4 - metencephalon (Rombencephalon)

5- myelencephalon (Rombencephalon)

Question 11

As the brain continues to develop, label the key parts of the brain that from from the 5 secondary vesicles (telencephalon, diencephalon, mesencephalon, metencephalon, and myelencephalon), numbered in the image 1-8 using the labels below?

• • spinal cord
• • cerebellum
• • left and right hemisphere
• • thalamus
• • pons
• • midbrain
• • hypothalamus
• • pons
• • medulla oblongata

Answer 11

1. left and right hemisphere
2. thalamus
3. hypothalamus
4. midbrain
5. cerebellum
6. pons
7. medulla oblongata
8. spinal cord

Question 12

As the brain continues to develop from from the 5 secondary vesicles (telencephalon, diencephalon, mesencephalon, metencephalon, and myelencephalon), 4 ventricles form. What are these called and what connects them

1. lateral, 2nd, aqueduct of slyvius and 5th ventricle
2. medial, 3rd, aqueduct of slyvius and 4th ventricle
3. lateral, 3rd, aqueduct of slyvius and inferior ventricle
4. lateral, 3rd, aqueduct of slyvius and 4th ventricle

Answer 12

4. lateral, 3rd, aqueduct of slyvius and 4th ventricle

• 1 - lateral ventricles (one on each side of hemisphere)
• 2 - 3rd ventricle (below thalamus)
• 3 - aqueduct of slyvius (connects 3rd and 4th ventricle)
• 4 - 4th ventricle (between pons and cerebellum)

Question 13

As the brain continues to develop from from the 5 secondary vesicles (telencephalon, diencephalon, mesencephalon, metencephalon, and myelencephalon), 4 ventricles form. What connects the 3rd and 4th ventricles?

1. aqueduct of slyvius (also called cerebral aqauduct)
2. arachnoid granulocytes
3. glymphatic system
4. vein

Answer 13

1. aqueduct of slyvius (also called cerebral aqauduct)

Question 14

If the ventricle system is damaged or it does not develop properly then this can cause problems. One such problem is the Dandy-Walker malformation, what is this?

Answer 14

• congenital abnormality
• expansion of the 4th ventricle (huge in image) means little or no cerebellum develops

Question 15

What are choroid plexus and where can this be found in the brain?

1. plexus of cells arising from ventricles
2. arachnoid granules
3. ventricular zone
4. subarachnoid space

Answer 15

1. plexus of cells arising from ventricles
   - ependymal cell (form of glial cell) line the ventricles of the brain
   - collectively the ependymal cells make up the choroid plexus

Question 16

Ependymal cells become specialised turning into choroid cells, which make up the choroid plexus. What do these cells produce in the brain and interact with in the brain?

Answer 16

• capillaries invaginate within the choroid plexus and CSF is formed here
• choroid plexus cells filter fluid to form the CSF

Question 17

The choroid plexus, is responsible for CSF production. Where can the choroid plexi be found?

Answer 17

• in each of the 4 ventricles inside the brain

Question 18

CSF is created in the choroid plexus of the ventricles in the brain. Using the labels below, order the process of how CSF is created:

• ultrafiltrte collects in choroid stroma
• arterial blood is filtred creating an ultrafiltrate of plasma
• once it passes choroid cells it enters the CSF
• ultrafiltarte has to actively or passively diffuse across choroid cells due to tight junctions

Answer 18

1. arterial blood is filtred creating an ultrafiltrate of plasma
2. ultrafiltrte collects in choroid stroma
3. ultrafiltarte has to actively or passively diffuse across choroid cells due to tight junctions
4. once it passes choroid cells it enters the CSF

Question 19

Where is the Na/K+ pump on the choroid epithelium cells of the ventricles?

Answer 19

• located on the apical side (closest to CSF) of the cell instead of the basal lateral membrane
• creates a net effect of Na⁺ crossing into CSF creating an osmotic gradient

Question 20

The Na/K+ pump on the choroid epithelium cells of the ventricles is located on the apical side (closest to the CSF) of the cell instead of the basal lateral membrane. The Na/K+ pump creates an osmotic gradient due to the flow of Na+ into the CSF inside the ventricles. This means that H₂O will also want to flow, which can be used to create CSF. How is H₂O transported into the CSF?

1. aquaporin 1 (choroid cells) and aquaporin 4 (ependymal cells)
2. diffusion passively between tight junctions
3. with Na+/H2O ATPase pumps
4. by binding to K+

Answer 20

1. aquaporin 1 (choroid cells) and aquaporin 4 (ependymal cells)

Question 21

What can happen to the aquaporin 4 channels in neuromyelitis optica (NMO), also known as Devic’s disease, a rare condition where the immune system damages the spinal cord and the nerves of the eyes (optic nerves)?

1. increased number of aquaporin 4 channels
2. decreased number of aquaporin 4 channels
3. damage to aquaporin 4 channels so H2O cannot pass

Answer 21

3. damage to aquaporin 4 channels so H2O cannot pass
   - bodies immune system (IgG) attacks host cells including aquaporin 4 channels and the optic nerve

Question 22

What enzyme present inside the choroid epithelial cells that helps transport ions in and out of the cells? This is also important for maintaining pH in the body?

1. lactate dehydrogenase
2. creatine kinase
3. carbonic anhydrase enzymes
4. phosphocreatine

Answer 22

3. carbonic anhydrase enzymes
   - facilitate the following:
   - CO₂ + H₂O arrow ➡️ H₂CO₃ ➡️ H₊ + HCO⁻₃

Question 23

Bicarbonate can be created in the choroid epithelial cells due to carbonic anhydrase and pass into the CSF along with a Na+ cation. Why is this important?

1. draws H20 so important for making CSF
2. ensures balance between Na+ and K+ in
3. acts as a buffer, maintaining pH of CSF
4. involved in maintaining osmosis

Answer 23

3. acts as a buffer, maintaining pH of CSF
   - able to buffer any acid produced in the brain ensuring optimal pH for the brain

Question 24

Furosemide generally affects the distal tubules in the kidneys. Furosemide acts by blocking Na⁺/Cl^-/K⁺co-transporter being re-absorbed in the kidney tubules, meaning H2O is also not re-absorbed, thus increasing urine output. Why might this be useful in the brain?

Answer 24

• less Na+ in the body, so less can be absorbed into CSF
• less Na+ means less H2O and a reduction in the production of CSF
• important in patients who have increased inter-cranial pressure

Question 25

Although CSF and plasma have the same osmolarity, there are 3 key differences between them in regards to their composition. What are they?

1. plasma has higher K+ and lower amino acid concentration than CSF
2. plasma has lower K+ and lower amino acid concentration than CSF
3. plasma has higher K+ and higher amino acid concentration than CSF
4. plasma has lower K+ and higher amino acid concentration than CSF

Answer 25

4. plasma has higher K+ and higher amino acid concentration than CSF

• lower K⁺ (plasma 2.9 vs. 4.7 mEq CSF)
• lower protein (plasma 7 vs. 0.03 g/dL CSF)
• lower amino acids (plasma 2.6 vs. 0.03 CSF)

Question 26

CSF is a specialised form of plasma. How much is generally circulating in the brain and produced each day?

1. • 1.5ml in brain and 5ml produced/day
2. • 15ml in brain and 50ml produced/day
3. • 150ml in brain and 500ml produced/day
4. • 1500ml in brain and 5000ml produced/day

Answer 26

3. 150ml in brain and 500ml produced/day
   * 500ml is produced where 2/3 are produced in choroid plexus, specifically lateral

Question 27

Why is a high turnover over CSF a good thing?

Answer 27

• shows effective waste removal from the brain via the glymphatic system and venous sinuses via arachnoid granulations
• CSF provides mechanical and chemical protection

Question 28

What is normal CSF pressure?

Answer 28

• 8-18cmH₂O

Question 29

Although the choroid plexus allows fluid to move into the brain via the ventricles from the ultrafiltrate of blood, this is not the case throughout the brain as this would allow too much fluid in the brain. This is where the blood brain barrier (BBB) functions to ensure there are no dramatic shifts in electrolytes. What are the 3 key components that ensure the BBB stops shifts in electrolytes?

1. tight junctions between endothelial cells, astrocytes, pericytes
2. tight junctions between endothelial cells, microglial, pericytes
3. tight junctions between endothelial cells, oligodendrocytes, pericytes
4. tight junctions between endothelial cells, astrocytes, glomeruli

Answer 29

1. tight junctions between endothelial cells, astrocytes, pericytes

• tight junctions between endothelial cells initially
• astrocytes (glia cells) surround the endothelial cells
• pericytes (vascular smooth muscle cells wrap around endothelial cells

Question 30

There are parts of the brain that lack a blood brain barrier. These are called circumventricular structures, which are in or near the base of the brain that differ from normal brain tissue in having capillaries that lack the usual blood-brain barrier and thus are not isolated from certain compounds in the blood. They are leaky and allow things to flow from and into arterial blood, similar to the choroid plexus. What is 1 key example of a circumventricular organs where the secretion of something into arterial blood is required?

Answer 30

• pituatory gland secretes hormones into arterial blood

Question 31

What is a CSF cisterns?

Answer 31

• cistern means closed space acting as a reservoir
• they are named based on their location

Question 32

Cisterns, means large space or pools. When CSF leaves the ventricles where does it go?

1. moves through ventricles of the brain into the spinal cord
2. through arachnoid granulations and into venous sinuses
3. directly into sub-clavian veins
4. back into capillaries in choroid plexus

Answer 32

2. through arachnoid granulations and into venous sinuses

• leaves the ventricular system and into subarchnoid space
• travels superiorly to the arachnoid granulations in the superior sagittal sinus
• moves through arachnoid granulation into the venous sinuses
• eventually drains back into the venous system

Question 33

The venous system in the brain sits between which the 2 layers of which meningeal layer?

1. periosteum and meningeal layer, which make up the dura matter
2. periosteal and meningeal layer, which make up the dura matter
3. pia and meningeal layer, which make up the dura matter
4. periosteal and subarachnoid layer, which make up the dura matter

Answer 33

2. periosteal and meningeal layer, which make up the dura matter

Question 34

What 2 things drain into the venous system (NOT VEINS) of the brain?

Answer 34

1 - CSF

2 - blood

• both then drain into the internal jugular vein

Question 35

What is the perivascular space, also referred to as the Virchow–Robin space?

Answer 35

• contained within the subarachnoid space (between arachnoid and pia mater)
• arteries, called penetrating arteries enter the brain
• space surrounding arteries is called the perivascular space

Question 36

What is the glymphatic system?

Answer 36

• CSF moves from subarachnoid space into the perivascular space
• CSF then enters the interstitial space in the brain
• CSF has a convective flow that moves through the brain and into the venous system
• essentially the brains lymphatic system, more so when asleep

Question 37

What is a Choroid plexus papilloma?

Answer 37

• benign tumour that forms in the choroid plexus
• results in over expression of CSF, increasing intercranial pressure

Question 38

If the subarachnoid granules or the ventricular system is blocked due to stenosis or a cyst what can this cause in the brain?

1. decreased intercranial pressure
2. tumour formation
3. increased intercranial pressure
4. ischaemia of arteries in the brain

Answer 38

3. increased intercranial pressure

• CSF continues to be produced as normal
• CSF cannot drain via venous sinuses and glymphatics system
• increased fluid in form CSF increases intercranial pressure that presses on the brain

Question 39

In addition to increasing pressure in the brain either through over production of CSF due to choroid plexus papilloma, or a blockage in the subarachnoid granules due to a cyst or stenosis there can be too little pressure as not enough CSF is being made. What are the 2 most common cause of this?

1. congenital abnormality and trauma
2. trauma and infection
3. trauma and too much fluid fluid removed during spinal tap
4. too much fluid fluid removed during spinal tap and infection

Answer 39

3. trauma and too much fluid fluid removed during spinal tap

Question 40

What does hydrocephalus mean, which is greek for hydro = water and cephalus = head?

1. not enough fluid in the brain causing low intercranial pressure
2. too much fluid in the brain causing low intercranial pressure
3. not enough fluid in the brain causing increased intercranial pressure
4. too much fluid in the brain causing increased intercranial pressure

Answer 40

4. too much fluid in the brain causing increased intercranial pressure
   - excessive CSF accumulates in the brain
   - increases intercranial pressure

Question 41

There are 2 main types of hydrocephalus (too much CSF in the brain), communicating and non-communicating. What are these 2 forms of hydrocephalus?

Answer 41

• communicating/non obstructive = blockage outside of the ventricular system
• non communicating/obstructive = blockage inside the ventricular system (ventricular system cannot communicate with each other)

Question 42

In hydrocephalus there is an increase in CSF and intercranial pressure, which is trapped within the cranium and can be dangerous in adults. Why can this be less dangerous in paediatrics?

Answer 42

• cranium is not fused
• cranium can expand

Question 43

What type of imaging and what does this image show below?

Answer 43

• CT scan
• hydrocephalus, all ventricles have expanded in size

Question 44

What are 2 of the most common ways can we assess the intercranial pressure?

1. lumbar puncture and fundoscopy
2. MRI scan and fundoscopy
3. lumbar puncture and MRI
4. lumbar puncture and blood pressure test

Answer 44

1. lumbar puncture and fundoscopy

• lumbar puncture
• examine back of the eyes (fundoscopy), if blurred, suggest increased pressure

Question 45

What is a common mechanical method that can be used to treat hydrocephalus?

Answer 45

• put a shunt in the brain, specifically the lateral ventricles
• drains CSF out of the brain and into the GIT
• normally stays in the patient for life, but can block and get infected

Question 46

What is a lumbar puncture/spinal tap?

Answer 46

• needle is inserted into the subarachnoid space
• generally down in the spinal cord, generally L3-L4
• probably the chordae equina (no spinal cord, so less risk of damage)

Question 47

In a lumbar puncture/spinal tap, in addition to measuring CSF fluid and pressure, what other things are commonly measured in CSF?

Answer 47

• cell types (red and white blood cells)
• glucose levels
• culture, PCR
• protein levels

Question 48

What is one of the most common reasons why we would perform a lumbar puncture?

Answer 48

• meningites (inflammation of the meninges)
• analysis of CSF fluid can determine what cause of meningitis can be (infection or haemorrhage)