The ventricular system and circulation of cerebrospinal fluid Flashcards
What does a ventricle mean?
- small cavity/chamber
How do ventricles form?
- forms from the neural canal
- neural canal dilates within the prosencephalon, leading to the formation of the lateral ventricles and third ventricle
What is the purpose of the ventricles?
- to produce and circulate CSF
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
1 - notochord
2 - neural plate
3 - neural crest
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?
- neuropores and can cause congenital abnormalities (spina bifida/anencephaly)
- nanapores and can cause congenital abnormalities (spina bifida/anencephaly)
- neural ends and can cause congenital abnormalities (spina bifida/anencephaly)
- caudal pores and can cause congenital abnormalities (spina bifida/anencephaly)
- neuropores and can cause congenital abnormalities (spina bifida/anencephaly)
What is spina bifida?
- neural tube fails to seal correctly at the caudal end and there is no skin, can be:
- occulta = vertebral arch defects (not able to be seen as in the latin name
- cystica = meninges (and sometime the nerves) project out of vertebrae
What is anencephaly?
- 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
What do the neural crest cells associated with the nervous system go on to develop?
- PNS
The neural tube will develop into the CNS. What are the 3 primary vesicles called?
- diencephalon, prosencephalon, mesencephalon
- rombencephalon, prosencephalon, mesencephalon
- diencephalon, prosencephalon, mesencephalon
- telencephalon, prosencephalon, mesencephalon
mesencephalon
- rombencephalon, prosencephalon, mesencephalon
- Prosencephalon (forebrain)
- Mesencephalon (midbrain)
- Rombencephalon (hindbrain)
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?
1 - telencephalon (Prosencephalon)
2 - diencephalon (Prosencephalon)
3 - mesencephalon (Mesencephalon)
4 - metencephalon (Rombencephalon)
5- myelencephalon (Rombencephalon)
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
- left and right hemisphere
- thalamus
- hypothalamus
- midbrain
- cerebellum
- pons
- medulla oblongata
- spinal cord
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
- lateral, 2nd, aqueduct of slyvius and 5th ventricle
- medial, 3rd, aqueduct of slyvius and 4th ventricle
- lateral, 3rd, aqueduct of slyvius and inferior ventricle
- lateral, 3rd, aqueduct of slyvius and 4th ventricle
- 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)
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?
- aqueduct of slyvius (also called cerebral aqauduct)
- arachnoid granulocytes
- glymphatic system
- vein
- aqueduct of slyvius (also called cerebral aqauduct)
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?
- congenital abnormality
- expansion of the 4th ventricle (huge in image) means little or no cerebellum develops
What are choroid plexus and where can this be found in the brain?
- plexus of cells arising from ventricles
- arachnoid granules
- ventricular zone
- subarachnoid space
- 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
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?
- capillaries invaginate within the choroid plexus and CSF is formed here
- choroid plexus cells filter fluid to form the CSF
The choroid plexus, is responsible for CSF production. Where can the choroid plexi be found?
- in each of the 4 ventricles inside the brain
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
- arterial blood is filtred creating an ultrafiltrate of plasma
- ultrafiltrte collects in choroid stroma
- ultrafiltarte has to actively or passively diffuse across choroid cells due to tight junctions
- once it passes choroid cells it enters the CSF
Where is the Na/K+ pump on the choroid epithelium cells of the ventricles?
- 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
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?
- aquaporin 1 (choroid cells) and aquaporin 4 (ependymal cells)
- diffusion passively between tight junctions
- with Na+/H2O ATPase pumps
- by binding to K+
- aquaporin 1 (choroid cells) and aquaporin 4 (ependymal cells)
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)?
- increased number of aquaporin 4 channels
- decreased number of aquaporin 4 channels
- damage to aquaporin 4 channels so H2O cannot pass
- damage to aquaporin 4 channels so H2O cannot pass
- bodies immune system (IgG) attacks host cells including aquaporin 4 channels and the optic nerve
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?
- lactate dehydrogenase
- creatine kinase
- carbonic anhydrase enzymes
- phosphocreatine
- carbonic anhydrase enzymes
- facilitate the following:
- CO2 + H2O arrow ➡️ H2CO3 ➡️ H+ + HCO−3
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?
- draws H20 so important for making CSF
- ensures balance between Na+ and K+ in
- acts as a buffer, maintaining pH of CSF
- involved in maintaining osmosis
- acts as a buffer, maintaining pH of CSF
- able to buffer any acid produced in the brain ensuring optimal pH for the brain
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?
- 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
Although CSF and plasma have the same osmolarity, there are 3 key differences between them in regards to their composition. What are they?
- plasma has higher K+ and lower amino acid concentration than CSF
- plasma has lower K+ and lower amino acid concentration than CSF
- plasma has higher K+ and higher amino acid concentration than CSF
- plasma has lower K+ and higher amino acid concentration than CSF
- 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)
CSF is a specialised form of plasma. How much is generally circulating in the brain and produced each day?
- 1.5ml in brain and 5ml produced/day
- 15ml in brain and 50ml produced/day
- 150ml in brain and 500ml produced/day
- 1500ml in brain and 5000ml produced/day
- 150ml in brain and 500ml produced/day
* 500ml is produced where 2/3 are produced in choroid plexus, specifically lateral
Why is a high turnover over CSF a good thing?
- shows effective waste removal from the brain via the glymphatic system and venous sinuses via arachnoid granulations
- CSF provides mechanical and chemical protection
What is normal CSF pressure?
- 8-18cmH2O
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?
- tight junctions between endothelial cells, astrocytes, pericytes
- tight junctions between endothelial cells, microglial, pericytes
- tight junctions between endothelial cells, oligodendrocytes, pericytes
- tight junctions between endothelial cells, astrocytes, glomeruli
- 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
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?
- pituatory gland secretes hormones into arterial blood
What is a CSF cisterns?
- cistern means closed space acting as a reservoir
- they are named based on their location
Cisterns, means large space or pools. When CSF leaves the ventricles where does it go?
- moves through ventricles of the brain into the spinal cord
- through arachnoid granulations and into venous sinuses
- directly into sub-clavian veins
- back into capillaries in choroid plexus
- 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
The venous system in the brain sits between which the 2 layers of which meningeal layer?
- periosteum and meningeal layer, which make up the dura matter
- periosteal and meningeal layer, which make up the dura matter
- pia and meningeal layer, which make up the dura matter
- periosteal and subarachnoid layer, which make up the dura matter
- periosteal and meningeal layer, which make up the dura matter
What 2 things drain into the venous system (NOT VEINS) of the brain?
1 - CSF
2 - blood
- both then drain into the internal jugular vein
What is the perivascular space, also referred to as the Virchow–Robin space?
- 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
What is the glymphatic system?
- 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
What is a Choroid plexus papilloma?
- benign tumour that forms in the choroid plexus
- results in over expression of CSF, increasing intercranial pressure
If the subarachnoid granules or the ventricular system is blocked due to stenosis or a cyst what can this cause in the brain?
- decreased intercranial pressure
- tumour formation
- increased intercranial pressure
- ischaemia of arteries in the brain
- 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
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?
- congenital abnormality and trauma
- trauma and infection
- trauma and too much fluid fluid removed during spinal tap
- too much fluid fluid removed during spinal tap and infection
- trauma and too much fluid fluid removed during spinal tap
What does hydrocephalus mean, which is greek for hydro = water and cephalus = head?
- not enough fluid in the brain causing low intercranial pressure
- too much fluid in the brain causing low intercranial pressure
- not enough fluid in the brain causing increased intercranial pressure
- too much fluid in the brain causing increased intercranial pressure
- too much fluid in the brain causing increased intercranial pressure
- excessive CSF accumulates in the brain
- increases intercranial pressure
There are 2 main types of hydrocephalus (too much CSF in the brain), communicating and non-communicating. What are these 2 forms of hydrocephalus?
- communicating/non obstructive = blockage outside of the ventricular system
- non communicating/obstructive = blockage inside the ventricular system (ventricular system cannot communicate with each other)
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?
- cranium is not fused
- cranium can expand
What type of imaging and what does this image show below?
- CT scan
- hydrocephalus, all ventricles have expanded in size
What are 2 of the most common ways can we assess the intercranial pressure?
- lumbar puncture and fundoscopy
- MRI scan and fundoscopy
- lumbar puncture and MRI
- lumbar puncture and blood pressure test
- lumbar puncture and fundoscopy
- lumbar puncture
- examine back of the eyes (fundoscopy), if blurred, suggest increased pressure
What is a common mechanical method that can be used to treat hydrocephalus?
- 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
What is a lumbar puncture/spinal tap?
- 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)
In a lumbar puncture/spinal tap, in addition to measuring CSF fluid and pressure, what other things are commonly measured in CSF?
- cell types (red and white blood cells)
- glucose levels
- culture, PCR
- protein levels
What is one of the most common reasons why we would perform a lumbar puncture?
- meningites (inflammation of the meninges)
- analysis of CSF fluid can determine what cause of meningitis can be (infection or haemorrhage)
