1.7: Physiology 1

Question 1

Describe CSF

Answer 1

Clear, colourless fluid (mainly composed of water)

Question 2

Where is CSF produced?

Answer 2

Produced by the secretory epithelium of the choroid plexus

Question 3

How much CSF is produced per day? How much of this is in the CNS?

Answer 3

500-600mls per day 150mls in the CNS

Question 4

The CSF in the CNS is replaced XXXX times per day?

Answer 4

3-4 times per day

Question 5

Give a very brief overview of CNS production and circulation?

Answer 5

Produced in ventricles Circulates around the subarachnoid space Reabsorbed into the venous circulation

Question 6

The CSF is able to supply XXXXX and is able to remove XXXXX

Answer 6

Water/Ions/Amino Acids Metabolites

Question 7

What are the functions of the CSF?

Answer 7

Protection (Cushions the brain so it floats in the cranial cavity) Homeostatic (pH affects pulmonary ventilation and cerebral blood flow - also contains hormones) Circulation (Medium for transporting nutrients and waste products)

Question 8

How do you obtain CSF?

Answer 8

Lumbar Puncture

Question 9

What can analysis of CSF tell us?

Answer 9

Helps to diagnose the brain, spinal cord and meninges

Question 10

Describe what normal CSF contains/looks like?

Answer 10

Clear and colourless Contains a small amount of protein (15-45mg/dl) Contains a small amount of immunoglobulin Contains a small number of cells (1-5/ml)

Question 11

Describe embryological development of CSF apparatus?

Answer 11

The developing nervous system is made up of a tube called the neural canal. The cavity later develops into the ventricles of the adult brain and the spinal cord canal. From the cells in the walls of the ventricles, the choroid plexus develops. The choroidal cells are specialised secretory cells that secrete the CSF

Question 12

What produces the choroid fissure?

Answer 12

Developing arteries invaginate into the roof of the ventricle to form the choroid fissure

Question 13

Where is the choroid plexus of the adult brain found?

Answer 13

In the 3rd, 4th and lateral ventricles

Question 14

What is the choroid plexus?

Answer 14

A plexus (network) of cells that produce CSF

Question 15

How many ventricles of the brain are there? What are they?

Answer 15

Four ventricles of the brain They are interconnected cavities where CSF is produced

Question 16

Describe the structure of the choroid plexus?

Answer 16

Internal capillary Layer of ependymal cells that tight junctions between them Surrounded by CSF

Question 17

How is CSF secreted?

Answer 17

CSF secretion depends on active transport of ions The movement of polarised ions across the apical and basolateral membranes allows for the secretion of CSF

Question 18

Describe the movement of ions into the CSF?

Answer 18

Na+ by active transport into CSF from blood This pulls along Cl- Water is pulled along by both ions

Question 19

Describe the composition of CSF compared to blood?

Answer 19

More Na+ More Cl- Less K+ Less Protein Less Glucose

Question 20

Describe the relationship between CSF secretion and arterial blood pressure

Answer 20

CSF secretion by the choroid plexus is an active process and is not determined by the arterial blood pressure

Question 21

Name the ventricles?

Answer 21

Two lateral ventricles 3rd 4th

Question 22

In which ventricle(s) is CSF first formed?

Answer 22

Choroid Plexus of the lateral ventricles

Question 23

Describe CSF circulation? (Just through ventricles)

Answer 23

Formed by choroid plexus of lateral ventricles Passes through inter ventricular foraminae into 3rd More CSF added by choroid plexus in room of 3rd Passes into cerebral aqueduct Into fourth ventricle More CSF added by choroid plexus of 4th ventricle

Question 24

Where does CSF go after it has been in the 4th ventricle?

Answer 24

Circulates in the subarachnoid space Some enters the central canal of the spinal chord Reabsorbed by the arachnoid granulations in the superior saggital sinus

Question 25

Where is the blood brain barrier?

Answer 25

This is at the endothelial cells in brain capillaries

Question 26

Function of the blood brain barrier?

Answer 26

This protects the brain from many common bacterial infections and toxins

Question 27

What is the main obstacle for drug delivery to the CNS?

Answer 27

The blood brain barrier

Question 28

Describe tumours that can affect the ventricles, choroid plexus and CSF?

Answer 28

• Choroid Plexus Tumours - Colloid Cyst

Question 29

Describe ventricular haemorrhage?

Answer 29

This is accumulation of blood in the ventricles

Question 30

What is an epidural haetoma?

Answer 30

Arterial bleed between dura and skull

Question 31

What is an subdural haemorrhage?

Answer 31

Venous bleed between the dura and the arachnoid

Question 32

What is a subarachnoid haemorrhage?

Answer 32

Haemorrhage into the subarachnoid space

Question 33

What is hydrocephalus?

Answer 33

Accumulation of CSF in the ventricles or around the brain (either due to obstruction or overproduction) Causes increase in CSF pressure and ventricular enlargmenet

Question 34

Describe idiopathic intracranial hypertension?

Answer 34

This is increased CSF pressure for no obvious reason May have headaches and visual field disturbances due to papilloedema

Question 35

What is papilloedema?

Answer 35

This is swelling of the optic discs due to raised intra-cranial pressure Presents with visual symptoms - blurring, loss of vision, enlarged blind spot

Question 36

Function of aqueous humour?

Answer 36

This bathes the structures within the eyes Provides oxygen and metabolites Contains bicarbonate to buffer H+ produced by eye structures

Question 37

Where is aqueous humour produced?

Answer 37

Ciliary Body

Question 38

Describe aqueous humour circulation?

Answer 38

Ciliary Body Posterior Chamber Anterior Chamber Drains into the canal of Schlemm