Physiology

Question 1

Where is CSF produced

Answer 1

The secretory epithelium of the choroid plexus

This is found in the ventricles of the brain (spaces)

Question 2

Describe the appearance of the CSF

Answer 2

Clear, colourless liquid

Mostly water

Question 3

Roughly how much CSF is produced daily

Answer 3

150ml is present at any time and is replaced 3-4x per day

Question 4

What does CSF give to tissues

Answer 4

Water
Amino acids
Ions
Removes metabolites

Question 5

Describe how CSF ‘circulates’

Answer 5

Produced from lateral ventricles
Passes through interventricular foramen to 3rd and then through the cerebral aqueduct to 4th ventricle
They add to CSF as it drains through
Passes through the median and lateral apertures to subarachnoid space
Then absorbed back into venous circulation by passing through arachnoid villi into the SSS

Question 6

What are the main functions of CSF

Answer 6

Mechanical protection - shock absorber that protects brain
Homeostasis - pH affects pulmonary system and cerebral blood flow
Some hormones are transported in it
Provides nutrients

Question 7

How do you analyse CSF clinically

Answer 7

Lumbar puncture
Should be completely clear
Presence of blood or pus indicates a problem

Question 8

What is the choroid plexus

Answer 8

Network of capillaries are lined by the ependymal cells of the ventricles
Good connection between blood and brain

Question 9

The apical surface if the ependymal cells faces the circulation - true or false

Answer 9

FALSE
basolateral surface faces capillary
CSF is secreted through the apical membrane

Question 10

Which ions are transported in the production of CSF

Answer 10

Na, Cl and HCO3

Water also moves across due to ion movement

Question 11

What drives the ion movement needed for CSF production

Answer 11

The distribution of ion channels

NOT arterial blood pressure

Question 12

Are the ventricles in the brain connected to each other?

Answer 12

YES

There are 4 - 2x lateral and the third + fourth

Question 13

How many ventricles are in the brain

Answer 13

4
2x lateral
The third
The fourth

Question 14

How does CSF pass from the ventricles to the subarachnoid space

Answer 14

There are 3 holes in the roof of the 4th ventricles
The median aperture
2x lateral apertures

Question 15

How does CSF return to the venous system

Answer 15

Passes into the superior sagittal sinus via

Gets there by entering arachnoid villi - areas of arachnoid layer that push up into dura to be nearer blood

Question 16

What forms the blood brain barrier

Answer 16

Tight junctions between endothelial cells in the brain capillaries- prevent molecules passing through

Question 17

What are the pros and cons of the BBB

Answer 17

Pro = protects brain from many bacterial infections and toxins
Con - barrier to drug delivery into the CNS

Question 18

What is the aqueous humour

Answer 18

Specialized fluid that bathes the structures within the eye.
It provides oxygen and metabolites and contains bicarbonate

Question 19

Where is aqueous humour produced

Answer 19

Epithelial layer of the ciliary body

Question 20

Describe the path of aqueous humour

Answer 20

Produced in ciliary body
Flows into anterior chamber
Drains into the scleral venous sinus
Continuous process of secretion and reabsorption

Question 21

How do you block the production of aqueous humour

Answer 21

Block carbonic anhydrase (involved in its production)

Can be used to reduce pressure in glaucoma

Question 22

Which ions are involves in the production of aqueous humour

Answer 22

carbonic anhydrase in the cells generates HCO3

The bicarb is used to drive Na and Cl movement in the cell

Question 23

What 4 things must happen for us to see an object

Answer 23

Pattern of object must fall on the visual receptors in the retina
Amount of light entering must be regulated
The energy from light must be transduced to electrical signals
The brain must receive these signals

Question 24

Describe the layers of the retina

Answer 24

Photoreceptors are the furthest back
Bipolar cells sit in front and Ganglion cells in front of those

Light passes to back of eye and signal passes forward again

Question 25

What are the 2 types of photoreceptors

Answer 25

Rods and cones | 3 different types of cones

Question 26

What is the function of photoreceptors

Answer 26

Converts electromagnetic radiation to neural signals

Question 27

Describe the changes in membrane potential in photoreceptors

Answer 27

When exposed to light the photoreceptor becomes hyperpolarised Doesn't quite trigger a AP Releases less glutamate

Question 28

How is an AP triggered in the eye

Answer 28

Hyperpolarisation of photoreceptor then bipolar cells causes AP generation in ganglion cells Caused by light

Question 29

What is the dark current in the eye

Answer 29

A cGMP-gated Na+ channel that is open in the dark and closes in the light More glutamate is released in the dark so more sodium moves in

Question 30

What is rhodopsin

Answer 30

A visual pigment molecule Made of retinal and opsin Undergoes a conformational change when exposed to light When active it triggers a cascade involving G proteins which closes the Na channel Causes AP

Question 31

What is visual acuity and what determines it

Answer 31

Ability to distinguish two nearby points. Determined largely by photoreceptor spacing and refractive power

Question 32

What cells allow us to see colour

Answer 32

Cones cells | Different types absorb different wavelengths of light

Question 33

List features of cone cells

Answer 33

``` See colour Found in central retina - fovea Low convergence Low light sensitivity - work in well lit High visual acuity ```

Question 34

List features of rod cells

Answer 34

``` Achromatic - no colour vision Peripheral retina High convergence High light sensitivity - used in dark places Low visual acuity ```

Question 35

Why is the left visual field perceived by the right side of the brain

Answer 35

The nerves cross over at the optic chiasm

Question 36

Where is visual information processed

Answer 36

Visual cortex in the brain

Question 37

What are the meninges

Answer 37

3 layers of tissue surrounding the entire brain Dura mater - tough, fibrous layer Arachnoid mater - thinner, spidery layer Pia mater - single cell layer

Question 38

CSF is found between which layer of the meninges

Answer 38

Deep to the arachnoid layer (subarachnoid space) | Between arachnoid and pia

Question 39

What passes through the tentorial notch in the dura mater

Answer 39

The brain stem and some cranial nerves

Question 40

The optic nerves are covered by meninges - true or false

Answer 40

TRUE | therefore some consider optic nerves as extensions of the brain/CNS

Question 41

Which type of fibres are contained in the oculomotor nerves

Answer 41

Motor | Parasympathetic

Question 42

Describe the trochlear nerve

Answer 42

Long intracranial course | Very thin as only supplies 1 muscle - superior oblique

Question 43

Describe the abducent nerve

Answer 43

Also has a long intracranial course | Innervates the lateral rectus in eye

Question 44

What do the parasympathetic fibres of the oculomotor nerve supply

Answer 44

Constrictor papillae Responsible for constricting the pupil If damaged the eye will dilate

Question 45

What are the 3 components of the accommodation reflex

Answer 45

Fattening of the lens Constriction of the pupil Convergence of the eyes

Question 46

What is the purpose of the accommodation reflex

Answer 46

It is used to focus on near objects