Physiology

Question 1

role of CSF

Answer 1

supplies nutrients and removes metabolites
shock absorbing
affects pulmonary ventilation and blood flow

Question 2

how does CSF affect pulmonary ventilation and blood flow?

Answer 2

pH of the CSF

Question 3

what is a choroid plexus?

Answer 3

network of capillaries in the ventricles

Question 4

what does secretion of CSF depend on?

Answer 4

Na+ AT across the cells which pulls along Cl- and H20

Question 5

ion concentrations in normal CSF?

Answer 5

high Na+
high Cl-
low K+
low glucose
low protein

Question 6

what does the BBB consist of?

Answer 6

capillary endothelium
basal membrane
perivascular astrocytes with tight junctions

Question 7

what substance bathes the eye?

Answer 7

aqueous humour

Question 8

what metabolites are in the aqueous humour and what is its role?

Answer 8

HCO3- which buffers H+ produced by the cornea and lens by anaerobic glycolysis

Question 9

what is the ciliary body and posterior surface of the iris covered by?

Answer 9

two layers that are a continuation of the retina- NPE and PE

Question 10

how are HCO3- and H+formed in the eye?

Answer 10

hydration of CO2 catalysed by carbonic anhydrase

Question 11

where is HCO3- and H+ formed in the eye transported to?

Answer 11

PE in exchange for Na+ and Cl-

Question 12

where are Na+ and Cl- transported to once in the PE?

Answer 12

into the aqueous humour via Na+/K+/2Cl- which is accompanied by water

Question 13

what is glaucoma?

Answer 13

raised intra-ocular pressure due to excess aqueous humour

Question 14

what is used in glaucoma?

Answer 14

CA inhibitors as it prevents formation of HCO3- and H+ which stops Na+ and Cl- being moved into aqueous humour and bringing water with it

Question 15

what cells are in the retina?

Answer 15

photoreceptors
horizontal cells
bipolar cells
amacrine cells
ganglion cells

Question 16

what is the resting membrane potential of photoreceptors?

Answer 16

-20mV as Na+ channels are open in the dark

Question 17

what happens to the membrane potential in photoreceptors when there is light exposure?

Answer 17

hyperpolarisation as Na+ closes

-90mV

Question 18

where are rods located on the retina?

Answer 18

all across

Question 19

describe rods

Answer 19

achromatic
peripheral retina
high convergence
high light sensitivity (see in dim light)
low visual acuity

Question 20

describe cones

Answer 20

chromatic
central retina
low convergence
low light sensitivity
high visual acuity

Question 21

where are cones located on the retina?

Answer 21

central retina, concentrated at the fovea

Question 22

colour of short wave

Answer 22

blue

Question 23

colour of medium wave

Answer 23

green

Question 24

colour of long-wave?

Answer 24

red

Question 25

what is the retina divided into?

Answer 25

at the fovea it is split into:

• nasal
• temporal

Question 26

do nasal retina cross at the optic chiasm?

Answer 26

yes

Question 27

what does each eye see?

Answer 27

monocular visual field +/- 45 degrees

overlap to create a binocular field +/- 45 degrees

Question 28

what is amblyopia?

Answer 28

cortical blindness

no problem with the eye, but one eye has better vision than the other

Question 29

causes of amblyopia

Answer 29

strabismus (wandering eye) if not corrected if infancy

need to cover good eye so connections can grow in weak eye

Question 30

define Hebb’s postulate

Answer 30

cells that fire together, wire together

lack of visual acuity leads to less branching- if one neurone is no longer present then the working neurone invades space (competition)