The Ventricular System Flashcards
What is a ventricle?
A small cavity / chamber
What are the ventricles of the brain formed from?
The expansion and folding of the neural plate.
What is the purpose of the ventricles in the brain?
To produce and distribute CSF.
What stimulates the epiblast to differentiate?
The notocord
What does the epiblast differentiate into?
Differentiates neural plate cells
How does the neural tube form?
The neural plate cells grow rapidly, sink down and creates the neural fold.
The neural crest (top levels of cells in the neural plate) join together and seal off the neural plate, forming the neural tube which detaches from the epiblast.
Which embryonic cells detach and become the peripheral nervous system?
The neural crest cells
Which enzyme is found that is produced by the neural plate?
ACh-esterase
What is the name of the process by which the neural tube is formed?
Neuralation
What are the ends of the neural tube called?
Neuropores
What happens if the neuropores do not seal?
Congenital abnormalities
What are the two ends of the neural tube called?
Cranial end
Caudal end
What is spinal dysraphism?
Spinal cord and cranium do not fully develop.
Name two types of spina bifida
Spina bifida occulta
Spina bifida myelomeningocele
Which vitamin deficiency is linked to neural tube abnormalities?
Folate
Which drug is linked to lowering folate levels?
Sodium valporate
Which embryologic structure creates the central nervous system?
Neural tube
What are the three primary brain vesicles?
Prosencephalon
Mesencephalon
Rhombencephalon
Which secondary brain vesicles arise from the Prosencephalon?
Telencephalon & Diencephalon
Which secondary brain vesicles arise from the Rhombencephalon
Metencephalon
Mylencephalon
How does the neural tube fit into the cranium as it grows?
It bends at junctions called flexures
Name 3 brain flexures
Midbrain flexure
Pontine flexure
Cervical flexure
What are the ventricles in the forebrain called?
Lateral ventricles (one in each cerebral hemisphere)
3rd Ventricle
Where is the Aqueduct of Sylvius and what does it do?
Found in the midbrain
Connects 3rd and 4th ventricles
Where is the 4th ventricle found?
Hindbrain
What does the neural tube form in the brainstem?
The central canal.
Which congenital abnormality causes excessive expansion of the 4th ventricle during development?
Dandy-Walker Malformation
What type of cells line the ventricles?
Ependymal cells
What type of cells are ependymal cells?
Glial cells
Which cells produce CSF and what type of cell are they a specialisation of?
Choroid cells produce CSF
They are specialised ependymal cells.
What does plexus mean?
Network
How does CSF differ from serum?
Less K and less protein
How is CSF similar to serum?
Similar osmolality, Na and HCO3.
Where are choroid cells found?
In the choroid plexus within the lateral, 3rd & 4th ventricles.
How is CSF formed?
Is made as an ultra filtrate from blood passing through the choroid plexus
How do solutes move out into the choroid plexus?
The capillaries are fenestrated (pores) which allows solutes to move through.
What type of cell junctions exist between choroid cells?
Tight junctions
Which solutes leave the capillaries and pass through the choroid cells to form CSF?
Na
Cl
HCO3
H20
Which solutes leave CSF and move through choroid cells to the blood?
K+
Which pump controls the movement of Na out & K in of the choroid cells?
Na / K ATPase pump
What drives the movement of water into the CSF through the choroid cells?
The movement of Na into the CSF - H20 follows
Which enzyme in the choroid cells is responsible for the buffering of pH?
Carbonic anhydrase
What happens to CSF levels if you inhibit carbonic anhydrase?
Formation of CSF is reduced.
What happens if you have too much CSF in (a) adults; (b) children
(a). It causes the brain to be compressed
(b). It causes hydrocephaly - with a resulting big head
Why is there a difference between adults and children to the response of having too much CSF?
In adults the sutures are fixed, in children they are not and therefore their skulls can control whilst adult skulls cannot.
How much volume of CSF do we have in our system?
150ml
How much CSF is produced each day?
500 ml each day
Which area produces the majority of the CSF?
The lateral ventricles
Where does CSF reside in the brain?
In the subarachnoid space.
Rate of production needs to = what in regards to CSF?
Rate of reabsorption
What is normal CSF pressure?
8 - 18 cm H20
What is the function of CSF?
Mechanical & chemical protection
Waste removal
What happens if the rate of reabsorption is less than the rate of production of CSF?
Get too much CSF in the cranium & spine - causing compression of the brain and spinal cord.
What happens if the rate of reabsorption is more than the rate of production of CSF?
Is not enough CSF in the cranium - can get positional headaches etc.
What does the BBB do?
Protects brain from rapid changes in electrolyte & metabolites.
Protection from toxins in the blood.
How is the BBB formed?
Blood capillaries are specialised in that they are sealed off (not leaky) - via
- Tight junctions
- Thick basement membrane
- Astrocyte foot processes
Which parts of the brain lack a BBB?
Choroid plexus
Circumventricular organs
Why do the circumventricular organs need to be directly exposed to blood?
Neuroendocrine control
How does CSF move around the brain?
Via the ventricular system
Name 3 exits by which CSF can leave the brain ventricular system
Foramina of Lushka x2
Foramina of Megende
Once CSF has left the ventricular system of the brain - where does it go?
Into the subarachnoid space
How does CSF leave the brain from the subarachnoid space?
Moves into the venous sinuses via arachnoid granulations.
How does CSF leave the venous sinuses?
Eventually empties into the internal jugular vein.
What are perivascular spaces?
Space between the arteries of the brain and the interstitium.
What is the name of the space between the veins and interstitium in the brain?
Perivenous space
What is an alternative name for the perivascular space?
Virchow-Robin space
What is the name of the system that controls fluid levels in the perivascular and perivenous spaces?
Glymphatic system
What is the purpose of the glymphatic system?
Allows waste products to be removed from the brain.
Can the size of the spaces in the glympatic system change?
Yes - can expand in sleep = thought this is due to increased removal of waste products at night
What can cause excess CSF in the system?
- Blockage
- Over production
- Reduced absorption
What can cause over production of CSF?
Malignancy of the choroid plexus - choroid plexus papilloma
What does excess CSF cause in the brain in terms of pressure?
High pressure
What does reduced CSF cause in the brain in terms of pressure?
Low pressure
What can cause low levels of CSF?
Leak of CSF out of the system - e.g. trauma or spinal tap
What happens to the brain when CSF is too low?
Brain sags - causing positional headaches
What are the three layers of meninges?
Dura mater
Arachnoid mater
Pia mater
What are the Pia mater & arachnoid mater known as?
Leptomeninges
What are the dura mater & arachnoid mater known as?
Pachymeninges
What are the 2 types of hydrocephalus?
Communicating / Non-obstructive (blockage outside the ventricular system)
Non-communicating / Obstructive (blockage inside the ventricular system)
What is congenital hydrocephalus usually caused by?
Obstructive hydrocephalus
How can you treat hydrocephalus?
Abdominal-peritoneal shunts
If an LP is done - and the first tube has lots of RBCs, but by the 4th there arent many - what does this suggest?
Traumatic tap - that you’ve nicked a BV on the way in.
If the glucose in CSF is high, but serum levels are also high - what does this suggest?
That the P has diabetes
