Physiology

Question 1

What produces the cerebrospinal fluid?

Answer 1

secretory epithelium of the choroid plexus

Question 2

What are the main functions of the cerebrospinal fluid?

Answer 2

• shock-absorbing to protect brain tissue
• pH of CSF affects pulmonary ventilation and cerebral blood flow
• exchange of nutrients and waste

Question 3

How is cerebrospinal fluid obtained for analysis?

Answer 3

lumbar puncture

Question 4

What is meant by the brain’s ventricles?

Answer 4

larger areas of the neural canal

Question 5

How is the choroid plexus formed?

Answer 5

• Developing arteries invaginate the ventricle to form the choroid fissure
• These then enlarge into villi and form the choroid plexus

Question 6

Plasma from the blood vessels in the choroid plexus contributes to the CSF. TRUE/FALSE?

Answer 6

TRUE
epithelial cells absorb plasma and modify it
then released from opposite

Question 7

What constituents are found in higher concentrations in CSF than in plasma?

Answer 7

CO2
Cl
Na

Question 8

What constituents are in higher concentrations in plasma than CSF?

Answer 8

Protein

Cholesterol

Question 9

What connects the lateral ventricle to the third ventricle?

Answer 9

intraventricular foramina (of Monroe)

Question 10

What connects the third and fourth ventricles?

Answer 10

Cerebral Aqueduct (of Sylvius)

Question 11

What structures allow the CSF to exit the ventricles and enter the subarachnoid space?

Answer 11

Foramen of Magendie

Foramina of Luschka

Question 12

What creates the blood brain barrier?

Answer 12

Tight junctions between brain endothelial cells prevent paracellular movement of molecules

Question 13

What parts of the brain do NOT contain the blood brain barrier?

Answer 13

circumventricular organs or pineal gland

Question 14

What tumours most commonly arise in the ventricles, choroid plexus and CSF?

Answer 14

• Colloid cyst (found at interventricular foramen)
• Ependymomas (from ependymal cells lining ventricles)
• Choroid plexus tumours

Question 15

An arterial haemorrhage between the skull and dura matter is known as what?

Answer 15

Epidural hematoma

Subarachnoid hemorrhage

Question 16

A subdural hematoma occurs between which layers?

Answer 16

venous bleed

between dura matter and arachnoid

Question 17

what is hydrocephalus?

Answer 17

• accumulation of CSF in ventricular system (obstruction or overproduction)
• enlargement of one or more ventricles and increase in CSF pressure

Question 18

How is papilloedema caused?

Answer 18

optic disc swelling due to increased intracranial pressure

transmitted to the subarachnoid space surrounding the optic nerve

Question 19

How does the optic disc appear on the fundus exam if there is papilloedema?

Answer 19

optic disc bulges and appears blurred

Question 20

Describe the course of the aqueous humour

Answer 20

ciliary body 
posterior chamber 
flows into the anterior chamber
drains to the scleral venous sinus 
through trabecular meshwork and the canal of Schlemm

Question 21

Describe the 2 layer structure of the ciliary epithelium

Answer 21

pigmented epithelium faces the blood

non-pigmented epithelium faces opposite direction

Question 22

Briefly describe how Na and Cl make their way into the aqueous humour

Answer 22

Carbonic anhydrase catalyses a reaction to produce H+ and HCO3
H+ is exchanged for Na into the pigmented cell
HCO3 is exchanged for Cl into the pigmented cell
Na and CL then pass to non-pigmented cell via gap junctions
Na and Cl use the Na/K/CL co transporter to leave non-pigmented cell and enter aqueous humour

Question 23

What drugs can be used to halt the production of aqueous humour?

Answer 23

Carbonic anhydrase inhibitors

Question 24

Give examples of carbonic anhydrase inhibitors which can be used in glaucoma

Answer 24

Dorzolamide - eye drops (=> avoids systemic side effects )

Acetazolomide - oral (beware of kidney acidosis)

Question 25

After light hits the photoreceptors, what cells does the signal pass to?

Answer 25

photoreceptor -> bipolar cell -> ganglion cell

Question 26

Where are Action Potentials generated after light is sensed at the photoreceptors?

Answer 26

Only at ganglion cell | the rest only depolarise the membrane, but dont generate an AP

Question 27

What are the two shapes of photoreceptors?

Answer 27

Rods | Cones

Question 28

What effect does light have on the cell membrane potential?

Answer 28

hyperpolarizes | closes cGMP gated Na channel => less positive into cell

Question 29

How do photosensitive rods hyperpolarize the membrane?

Answer 29

Cis-retinal + opsin = Trans-retinal Trans-retinal activates transducin Transducin activates cGMP phosphodiesterase (PDE) PDE hydrolyses cGMP and prevents Na influx => HYPERPOLARISED

Question 30

What characteristics of photoreceptors can increase visual acuity?

Answer 30

spacing of photoreceptors (closer increases acuity) | volume of photoreceptors

Question 31

Rod photoreceptors are usually used for seeing in normal daylight. TRUE/FALSE?

Answer 31

FALSE cone receptors are for seeing in daylights rod receptors are for seeing in dim light

Question 32

How do photoreceptors allow us to see different shades of the same colour?

Answer 32

mixture of long, middle and short wave cones can create different shades

Question 33

What part of the retina contains cones rather than rods?

Answer 33

Fovea (centre of macula)