CSF

Question 1

Body fluid breakdown

Answer 1

Question 2

Give an example of a transcellular fluid

Answer 2

Saliva (modified in some way)

Question 3

BBB is under direct control by _____ ______

Answer 3

Glial cells - they control what can and cannot gain access to IS fluid of brain

Question 4

Explain vesicular transfer

Answer 4

Exocytosis - release of substance

Endocytosis - captured

Transcytosis - the whole process

Question 5

What do the glial cells form

Answer 5

Very tight junctions => BBB

Ensures endothelial cells of vasculature of the BVs delivering blood to brain are wedged

Question 6

What is the rate of passage of lipid soluble substances proportional to

Answer 6

Directly proportional to lipid solubility and inversely proportional to size

Question 7

What structure creates the tight junctions

Answer 7

Endfeet of astrocytes induce tight junctions

Question 8

Name the 2 places where CSF is produced

Answer 8

1. Within ventricles - choroid plexi capillary network
2. Around SA of everywhere in the brain, by astrocytes

Question 9

What cells share a function with astrocytes

Answer 9

Ependymal cells

Question 10

What are the choroid plexi

Answer 10

Network of capillaries found within ventricles (2 lateral and a 3rd and a 4th - reservoirs of CSF)

Question 11

Define CSF

Answer 11

A ‘sink’ of EC fluid filtered from blood that supplies and drains the interstitium

Question 12

How much CSF is in our body

Where is it found and in what proportion

Answer 12

140-150ml

Ventricles - 25ml

Spinal cord central canal - 30ml

Sub-arachnoid space - majority of volume

Question 13

How does the movement of CSF occur

Answer 13

Through systolic pulsations of arterial system - compression of ventricles and subarachnoid space

Question 14

Diagram of brain

Answer 14

Question 15

Rate of production of CSF

Answer 15

550 ml/day (0.35ml/min)

=> turns over 3.7 times/day

Question 16

50-70% of CSF is produced by ______ ______

Answer 16

Choroid plexi

Question 17

What is the 2nd way in which CSF is produced

Answer 17

Blood vessel to IS transfer - regulated by astrocytes

Question 18

How is CSF reabsorbed

Answer 18

Through arachnoid villi into veins via venous sinuses

Question 19

The CSF production by BV to IS transfer facilitates what

Answer 19

Rapid delivery of O2 and nutrients to a local area

Question 20

How much does the brain weigh in air

Answer 20

1400g

Question 21

What is the effective weight of brain floating in CSF

Answer 21

50g

Question 22

Components of meninges

Answer 22

Dura, arachnoid and pia mater

CSF fills subarachnoid space

Question 23

What does the buoyancy of CSF permit

Answer 23

Attachments to support brain

• BVs
• Nerve roots
• Fine fibrous arachnoid trabeculae

Question 24

What is a less invasive way of measuring ICP

Answer 24

CSF pressure is often a guide of ICP

Question 25

What is the normal range of CSF pressure

How can it be taken

Answer 25

65-195 mmCSF or 5-15 mmHg

Lumbar puncture procedure (between L3-L4)

Question 26

How can ICP be raised

Answer 26

Through obstruction of venous system, intracranial mass, brain oedema

Question 27

CSF composition overview

Answer 27

Question 28

what ion has a profound effect on electrically excitable tissues

Answer 28

Ca2+

Question 29

Analysis of CSF

Answer 29

Question 30

What is the composition of EC fluid in CNS highly regulated by

Answer 30

BBB (hence glial cells)

Question 31

What parts of the brain receive blood in an unfiltered form

What are these sites

Answer 31

Circumventricular organs

• Neurohypophysis (senses hormones - need to know real practical picture)
• Area postrema
• Hypothalami nuclei e.g. OVLT, supraoptic and paraventricular nuclei
• Subfornical organ

* Sites of physiological and endocrine feedback systems within the brain

Question 32

What allows the maintenance of the integrity of the BBB, despite these circumventricular organs

Answer 32

Rapid venous drainage from these sites