CNS and Meninges Flashcards
Describe the appearance of CSF
Clear, colourless mostly composed of water
Where is CSF produced?
Secretory epithelium of the choroid plexus in the ventricles
What is the volume of CSF circulating in the CNS at any one time?
150ml
State three major function of CSF
- Mechanical protection (shock absorber of which the brain sits in)
- Homeostatic function (pH and transport of hormones)
- Circulation (exchange of nutrients/waste)
How obtained for analysis?
Lumbar puncture
How does the choroid fissure develop?
Arteries invaginate the roof of the ventricle to form the choroid tissue, this causes the ependymal cells and vessels to enlarge to villi and form the plexus
What causes hydrocephalus?
CSF outflow obstruction which can cause enlargement of the ventricular space
How are the ependymal cells held together?
Tight junctions
What ions are involved in the production of CSF from blood?
Na+
Cl-
HCO3-
How does fluid move across the membrane?
Active sodium transport, electrical gradient pull chloride and water moves by osmosis
How is CSF different to blood?
Lower potassium, glucose and protein
Higher sodium and chlorine
Is the production of CSF active or passive?
Active process does not depend on arterial BP
How many ventricles are there?
Two lateral, a third and a fourth
State the connections between the ventricles
Foramen of monroe - laterals to third
Aqueduct of sylvius - third to fourth
Foramen of magendie and foramen of luschka - fourth ventricle to subarachnoid space
Where does the CSF go from the subarachnoid space?
Drains into the arachnoid villi of dural venous sinuses
What does the blood brain barrier consist of?
Capillary endothelium, its basal membrane and perivascular astrocytes
In the BBB what type of junction are between the endothelial cells?
Tight junctions - prevent paracellular movement
Do all areas of the brain have a BBB?
No - circumventricular organs and the pineal gland do not
Name three types of tumour related to CSF
- colloid cyst (often in interventricular foramen)
- ependymonas
- choroid plexus tumour
What can ventricular haemorrhage result in?
- epidural haematoma
- subdural haematoma
- subarachnoid haematoma
What are the symptoms of idiopathic intracranial hypertension?
Headache and visual disturbance
What is papilloedema?
Optic disc swelling due to increased intracranial pressure as a result of excess CSF
What are the symptoms of papilloedema?
Enlarged blind spot, blurring of vision and visual obscurations
What is the serious complication of papilloedema?
Compression of optic nerve which can lead to loss of vision
What conditions can increase intracranial pressure?
- tumours
- head injury
- hydrocephalus
- meningitis
- stroke
What is the Monro Kellie Hypothesis?
Intracranial volume is constant and the cranial cavity is inelastic so there is no room for expansion
What are the ocular symptoms for increased intracranial pressure?
Blurred vision Double vision Loss of vision Papilloedema Pupillary changes
What is special with the optic nerve?
They are tracts of the CNS covered by meninges
What happens to the optic nerve when ICP increases?
It gets compressed as well as the central artery and vein which leads to a bulging/swollen optic disc
What is a swollen optic disc known as?
papilloedema
If compression of the oculomotor nerve occurs what happens?
Only the superior oblique and lateral rectus still have innervation so the pupil will be turned down and out
How will oculomotor nerve compression present?
Dilated pupil, ptosis, down and out look
How can the oculomotor nerve be stretched or compressed?
The brain can herniate through folds created by the dura mater and if the medial temporal lobe herniates through the tectorial notch the oculomotor nerve can be affected
Why is the trochlear nerve susceptible to damage?
It has a long intracranial course
What is the effect of compression of the trochlear nerve?
Paralysis of the superior oblique which means the inferior oblique is unopposed
How will trochlear nerve compression present?
Eye cannot move inferomedially - diplopia when looking down
What will stretching of the abducent nerve cause?
Paralysis of the lateral rectus muscle
How will stretching of the abducens present?
Medial deviation of the eye
Name the five regions of the brain
Telencephalon - cerebral hemispheres Diencephalon - thalamus and hypothalamus Mesencephalon - midbrain Metencephalon - pons and cerebellum Myelencephalon - medulla
Name four types of glial cell
Astrocyte
Oligodendrocyte
Microglia
Ependymal
