L12 - correction of faulty neural circuits

Question 1

what is channelrhodopsin

Answer 1

non-selective channel, stimulated with light, causing channel to open

Question 2

what light is channel rhodopsin stimulated by

Answer 2

blue light 460nm

Question 3

what happens if switch of the light

Answer 3

closes faster when stimulated with 360nm

Question 4

what happens when switch on the light - channelrhodopsin

Answer 4

neuron is depolarised and sufficient to trigger a strike

the spike occurs everytime the neuron is stimulated

Question 5

halorhodopsin

Answer 5

stimulated by yellow light 570nm. causes hyperpolarisation of the membrane

Question 6

what is the problem with using rhodopsin channels in humans

Answer 6

don’t have the technologies to do so - express them in viruses which may not be safe

Question 7

what can be used instead of channelrhodopsin

Answer 7

2 small molecules - optical isomers of each other

Question 8

important parts of the small molecules

Answer 8

maleimide - binds to a specific channel
azobenzene - functions to change depending on stimulation of light
quaternary ammonium - serves as a block of the channel

Question 9

at what light does the trans isomer turn into the cis isomer

Answer 9

380nm

Question 10

at what light does the cis isomer turn back into the trans isomer

Answer 10

500nm

Question 11

what does the trans isomer do?

Answer 11

block the channel - when turned into cis isomer, the block is removed

Question 12

how does the small molecule work ?

Answer 12

enters the TRPV1 channel and acts on the channels from the inside of the cell

Question 13

why is it important that it works inside the cell

Answer 13

stays inside the cell longer

Question 14

what is the GABA receptor important for

Answer 14

regulating the overall excitability of the NS

Question 15

what causes epileptic seizures

Answer 15

overexitability of neurons in the brain

Question 16

what wavelength can activate the GABA receptors

Answer 16

380nm light

Question 17

what occurs when the GABA receptors are activated

Answer 17

hyper polarise the cells and remove hyperexcitabiltiy of the neurons

Question 18

what is retinitis pigmentosa

Answer 18

a disease in which the field of view becomes smaller and smaller until the patient becomes blind

Question 19

what causes retinitis pigmentosa

Answer 19

retinal degeneration which starts with the dying of the photoreceptors - rods and cones
as it progresses other cells in the retina become degernated (bipolar and ganglion cells)

Question 20

what is the treatment for retinitis pigmentosa

Answer 20

artificial retina or gene therapy

can use electrodes or tools to stimulate the visual system

Question 21

problems with using electrodes to stimulate neurons

Answer 21

chronic implantation of electrodes in the brain/retina will cause degeneration of the tissue around the electrodes as electrodes may hear up and kill surrounding neurons

Question 22

what are the 2 areas needed to stimulate to cure blindness

Answer 22

retina - for retinitis pigmentosa

visual cortex - when optic nerve didn’t develop/destroyed

Question 23

how are the retina and visual cortex stimulated

Answer 23

either by electric stimulation of channelrhodopsin and halorhodopsin

Question 24

problems with artificial stimulation of retina

Answer 24

stimulates ganglion cells but not photoreceptors or bipolar cells

Question 25

what are the 2 main classes of ganglion cells

Answer 25

parvocellular and magnocellualr

Question 26

size of parvocellular dendritic tree

Answer 26

small

Question 27

size of magnocellular dendritic tree

Answer 27

large

Question 28

what type of receptive fields to ganglion cells have

Answer 28

centre surround organisation

Question 29

what is a centre surround organisation

Answer 29

if stimulate ganglion cell in centre of the receptive field will have increase / decrease in spiking rate. if stimulate outside of receptive field will get opposite result in spiking rate

Question 30

what happens when switch of the light stimulating a ganglion cell

Answer 30

decrease in spiking rate

Question 31

what occurs when stimulate halorhodopsin in photoreceptors

Answer 31

get hyperpolarisation - leads to decrease in release of glutamate from the synapses

Question 32

what does intact centre surround organisation of RGCs in retinitis pigmentosa show

Answer 32

shows that can restore the basic properties of the cells

Question 33

what is intact during retinitis pigmentosa

Answer 33

diversity
center surround organisation
direction selectivity

Question 34

what are the 2 ways to control seizures

Answer 34

• use halorhodopsin expressed in excitatory cells - hyperpolarise the excitatory cell

use channelrhodpsin - depolarise inhibitory cells - so when stimulate the cell with blue light they release more GABA

Question 35

what tools are used to inject a virus to treat seizures

Answer 35

ontogenetic tools

Question 36

questions needed to ask to treat

Answer 36

where to express optogenetic tools
where is the seizure of the origin
excitatory or inhibitory neurons