Physiology

Question 1

Appearance of CSF

Answer 1

clear, colourless

Question 2

functions of CSF

Answer 2

mechanical protection for the brain
homestasis of pH in the brain and transport of hormones
circulation of nutrients and waste excretion

Question 3

describe the embryological development of the choroid plexus

Answer 3

3 weeks - cavity in neural canal forms ventricles and spinal canal
developing arteries invaginate roof of ventricle to form choroid fissure
forms the choroid plexus in conjunction to ependymal cells

Question 4

what ions have a higher and lower concentration in CSF compared to serum

Answer 4

higher, sodium, chloride

lower - glucose, potassium, proteins, cholesterol

Question 5

describe ion movement across ependymal cells causing CSF secretion

Answer 5

polarised nature
Na and Cl absorbed by epithelial cells and draws water from it and these are secreted at apical end with water into brain ventricles

Question 6

describe the circulation of CSF

Answer 6

CSF released in all brain ventricles
lateral ventricle to third ventricle by interventricular foramina
through aqueduct of midbrain into 4th
flows into subarachnoid space by single median/paired lateral apertures
circulates in central canal cord and drains to superior sagittal sinus

Question 7

what is the BBB made up iof and how does it work

Answer 7

capillary epithelia with basal membrane and perivascular astrocytes
tight junctions between capillary epithelia prevent paracellular movement of molecules

Question 8

possible pathologies causing issues within CSF, ventricles or choroid plexus

Answer 8

tumour
ventricular/subarachnoid haemorrhage 
epidural/subdural haematoma 
hydrocephalus 
idiopathic intracranial hypertension

Question 9

what is papilloedema and how may it appeasr

Answer 9

optic disk swelling due to increased ICP transmitted to subarachnoid space around optic nerve
blurred/lost vision, enlarged blind spot

Question 10

functions of aqueous humour

Answer 10

bathes structures within eye
nutrients to lens and cornea
buffers H ions produced by lens and cornea in anaerobic glycolysis by bicarb

Question 11

describe the movement of aqueous humour

Answer 11

produced in ciliary body in posterior chamber
flows into anterior chamber and then drains to scleral venous sinus through canal of schlemm, small diffusion into vitreous

Question 12

describe the movement of ions across the ciliary epithelia contributing to aqueous secretion

Answer 12

CO2 broken down byt carbonic anhydrase to H and HCO3
passes to pigmented epithelial cells to cause Na and Cl entry
net movement of Na and Cl across pigmented and non pigmented cells to be released in post chamber with water from aquaporins, osmotic gradient and ciliary channels

Question 13

how can carbonic anhydrase inhibitors be beneficial in glaucoma

Answer 13

prevents bicarb production so prevents net recruitment of Na and Cl and water drawing to slow aqueous production to try to match aqueous production to drainage

Question 14

4 factors required for successful vision

Answer 14

accomodation to focus light on visual receptors of retina
regulated light into eye
energy from light needs converted to electrical energy
brain needs to receive and interpret signals

Question 15

what is hebbs postulate

Answer 15

loss of binocularity

axon of cell A can excite cell B due to being close, leading to metabolic change and cell A having a greater efficiency

Question 16

what is amblyopia

Answer 16

cortical blindness

no issue with the eye but one has better vision than another

Question 17

what may strabismus cause and how can it be managed

Answer 17

can cause amblyopia
cover babys good eye with patch to strengthen poorer eye
surgical correction

Question 18

describe how signal transmission occurs in the retina

Answer 18

phoptoreceptors synapse with bipolar cells that synapse with ganglion cells
ganglion cell axons collate to form optic nerve

Question 19

decribe how lateral connections may occur in the retina

Answer 19

horizontal cells have input from other photoreceptors and project to other photoreceptors and bipolar cells
amacrine cells have input from bipolar cells and project to ganglion cells, bipolar cells or other amacrine cells

Question 20

regions of a photoreceptor

Answer 20

main body
outer segment
inner segment
synaptic terminal

Question 21

types of photoreceptors

Answer 21

rods

cones

Question 22

describe the dark current and how this causes signal transduction of light

Answer 22

photoreceptors have Em of -20mV

exposure to light causes closure of cGMP Na channel which causes hyperpolarisation to cause transduction

Question 23

what causes the closure of the cGMP Na channels

Answer 23

rhodopsin - retinal and opsin
light converts 11-cis-retinal to all-trans-retinal
closure of Na channels

Question 24

what is visual acuity

Answer 24

ability to distinguish between two points

Question 25

describe the larger convergence seen in rods

Answer 25

they are less dense and more rods to one ganglion cell so more adapted to seeing in dimmer light

Question 26

describe the smaller convergence seen in cones

Answer 26

cones are higher density and there are less of them per ganglion cell
they are better adapted to daylight

Question 27

there is greater convergence in rods/cones and there is greater acuity in rods/cones

Answer 27

rods

cones

Question 28

describe how cones have colour vision

Answer 28

they have opsins sensitive to different wavelengths of light

Question 29

true/false - rods have specific photosensitive opsins

Answer 29

false

Question 30

where are rods located in the retina

Answer 30

peripheral retina

Question 31

where are cones located in the retina

Answer 31

fovea and central retina