Yuck

Question 1

What is the neuronal tissue of the eye

Answer 1

Retina

Question 2

Which visual field activates which half of the brain.

Answer 2

The right visual field activates the left brain.

The left visual field activates the right brain.

Question 3

Functions of the retina

Answer 3

The main one is image acquisition.

Also processes info and make sure only important parts are sent to the brain.

Question 4

Where does the info from the eye go and what does this structure do and what are the neurons like.

Answer 4

Lateral geniculate nucleus.
Which also processes info.

The neruons here and similar to ganglion neurons.

Question 5

Where does eye info go after the LGN.

Answer 5

Down the optic radiation.

To the primary visual cortex at the back of the brain.

The main processing happens here.

Question 6

What are the two main cortex pathways for visual info.

Answer 6

Info will leave the primary visual cortex and choose one of two pathways.

Ventral- the what pathway. Includes V2 and 4 and the inferior temporal cortex. It is responsible for object recognition. DOWN

Dorsal- where pathway. Important for processing spatial info. It includes the position and speed of the object. It is in the posterior parietal area. UP

Question 7

Pupil

Lens

Answer 7

Regulates the amount of light that falls on the retina.

Focuses the image on the fovea. The part of the retina that is densely packed with photoreceptors. It processes the fine details. Contains mostly cones.

Question 8

Periphery of the retina.

Answer 8

Contains rods.

Identifies key features of the visual field.

More sensitive to light. You can see better in the dark in your peripheral view.

Question 9

Muller cells

Answer 9

Serve as a light guide to the retina.

Question 10

Retina structure.

Answer 10

3 layers of neurons and 2 layers of synapses.

The first layer to be activated are the photoreceptors. Then bipolar and then ganglion then to the brain. These are all feed forward neurons.

Feedback neurons are horizontal cells and amacrine cells which send inhibitory signals.

OPL between photoreceptors and bipolar. This has horizontal cells.
IPL between bipolar and ganglion. This has amacrine

Question 11

Horizontal cells

Answer 11

Shape the way bipolar cells process their info.

Question 12

Where does processing happen a lot

Answer 12

In synapses of retina.

Question 13

Rods and cones 4

Answer 13

Rods are active in dim light and cones are active in bright light.

Have polarised structure.

Phototransduction happens in the outer segment of the cells.

When light hits the photoreceptors they hyperpolarise.

Question 14

What happens to photoreceptors in the dark.

Answer 14

There is lots of cGMP in the cytoplasm and this will hold the channels open.
Ca and Na will enter the cells and cause depolarisation.

Question 15

What happens to photoreceptors in the light.

Answer 15

G proteins are activated that activate photodiesterase.
This turns cGMP into GMP.
Channels will close as there is low levels of cGMP.
Causing hyperpolarisation.

Question 16

Photoreceptors to bipolar cell activation

Answer 16

Some bipolar cells hyperpolarise while others depolarise in response to light.

ON cells depolarise when light goes on.
OFF cells hyperpolarise when light goes on.

Question 17

Sign inverting synapse.

Answer 17

All photoreceptors hyperpolarise in response to light.
So how does this cause the next cell in the pathway (ON cells) to depolarise and switch the sign.

When photoreceptors depolarise they release glutamate to the bipolar cells.
ON cells have a G protein receptor which is inhibitory.
OFF cell have a ligand receptor that is excitatory.

NOTES DONT MAKE SENSE BUT LEARN THIS FOR NOW

Question 18

Receptive fields

Answer 18

An area in the retina which when illuminated activates a visual neuron.

They have centre surround organisation. The illumination of the centre leads to a response that has an opposite polarity than illumination of the surround.

When the centre is illuminated it causes depolarisation. When the surround is illuminated it causes hyperpolarisation.

Question 19

How to stimulate certain areas of the visual field

Answer 19

You could use a spotlight to activate the centre cells.

You could use an annulus to stimulate the outer ring.

Question 20

One bipolar cell receives information from

Answer 20

Many photoreceptors

This is most seen in the retina periphery and not the fovea.

Question 21

How can photoreceptors activate bipolar cells.

Answer 21

Some activate them directly by synapsing to them and this is found mostly in the centre of the receptive field.
This causes hyperpolarisation of bipolar cells.

Some activate bipolar cells via horizontal cells. This is found in the surround of the receptive field.
This will depolarise the bipolar cells.

Question 22

Help

Answer 22

Photoreceptors always are hyperpolarised by light.

And then ON bipolar cells depolarise which is strange but it happens.

Question 23

IPL

Answer 23

After info is processed by bipolar cells it goes to the IPL.

this contains ganglion, bipolar and amacrine cells.

It contains presynapses of bipolar. Dendrites of ganglion and amacrine. And the post synapses of ganglion.
Both post and pre synapse of amacrine.

Question 24

Different ganglion cells

Answer 24

Ganglion with dense dendrites are responsible for visual acuity and object recognition.

Ganglion with a large dendritic field are responsible for positional information.

The dendrites can be asymmetrical and all point in one direction.

Question 25

Ganglion cell receptive fields.

Answer 25

Centre surround organisation

Off centre ganglion cells will cause spiking to stop when light is on the centre.
On centre ganglion cells will cause spiking to increase when light is on the centre.

Off centre ganglion cells will increase spiking when light is on the surround.
On centre ganglion cells will stop spiking when light is on the surround.

Question 26

What does illumination of the whole receptive field do to ganglion cells.

Answer 26

Ganglion cells are not activated because they are designed to respond to differences in illumination that occur within the receptive field.

Question 27

Two classes of ganglion cells

Answer 27

Parvocellular- very small dendritic tree and a small receptive field.
Slower conductance velocity. Responsible for processing shape and colour information.

Magnocellular- large dendritic tree and a large receptive field. Responsible for motion detection.

Question 28

Adaption of the visual system

Answer 28

If the same stimulus is seen several times the respond will change.

Desensitisation is where the sensitivity is decreased.
Sensitisation is where sensitivity is increased.

This can be the reason for visual illusions.

Question 29

what to look at when studying a new neuron

Answer 29

describe the size and shape of their dendritic trees as this will link to the function
map connections of the neruon
describe their activity and what stimulates them

Question 30

what is sparse labelling

what is fine detail labelling

Answer 30

this was done by golgi and not every cell is labelled so they could characterize neuron morphology.

done by cajal where you can see the individual dendrites. but this doesnt allow the staining of individual neurons and the neurons will be dead so you cannot see the function

Question 31

what is patch clamp and why is it good/bad

Answer 31

a glass electrode containing electrolyte is put against the cell membrane.
suction is applied and some of the membrane enters the electrode and the current in that small bit of membrane can be measured.
if you want to record the activity of the entire cell you can break a hole in the membrane by applying stronger suction.

this will allow recording of the neurons activity while it is still alive but this is very complicated. Using GFP instead may be better?

Question 32

what happens in a simple fluorescent microscope

what do the filters do?

Answer 32

blue light is shone onto the sample through an excitation filter, it hits a dichroic mirror to be deflected onto the sample.
then the sample will emit green light which can pass through the dichroic mirror, then through an emission filter and into the lens so we can see an image.

the excitation and emission filters make sure that the blue light is actually blue and that the light entering the camera is actually green.

Question 33

what happens to GFP to allow it to study function

Answer 33

a modification of GFP called Gcamp is used.
it is the fusion of GFP and two Ca binding proteins, MI3 and calmodulin.
where there is ca in the cell the two proteins interact and it makes the GFP brighter.
this means active neurons can be detected because they release ca when they are active.
this will create a movie of flashes of white neurons turning on and off when they are active and then inactive.
different neurons will light up when different stimulations are given, this helps us to study function.

Question 34

why is using a simple animal good for neuron study

Answer 34

they have less neurons and you can do a whole brain viewing because are simple.

Question 35

what do we have to do to generate the movies for the GFP

which type of microscopy is best

Answer 35

we need to use high resolution microscopes.
wide field microscopy collects light from above and below the focal plane.
confocal microscopy rejects light that isnt from the focal plane and decreases the area of excitation.
this allows for a massive increase in spatial resolution, normal wide field microscopy would produce a much blurrier image than confocal.

Question 36

what happens when you record the brain activity of a living mouse and why is it good/bad

Answer 36

take a mouse, fix the head in place, open the skull, attach the microscope, the mouse is given stimulation and the brains response is recorded.
it is usually sedated with Na channel blockers to calm it down but this will affect the neuronal activity being recorded, but without sedation the animal would be too stressed to give a normal response.
if the mouses head is fixed it will also respond differently to its natural behavior.
to solve this you could try and use virtual reality on the mouse.

Question 37

how can you use virtual reality on mice

how can you record freely moving mice

Answer 37

the mouse is placed on a ball that moves when it runs, and the visual field is set with the ball to act as virtual reality, the head is fixed but the mouse still feels like it is moving.

a tiny fluorescent microscope is placed in the skull, a microendoscope is attached to the brain area of interest, the mice will be stimulated and you can record their brain activity as they move and see white flashes of activity.

Question 38

optogenetics

Answer 38

channel rhodopsin is an ion channel which is activated by light.
when the channel is open the cell depolarises and it can transmit many different ions.
halorhodopsin is a channel stimulated by yellow light and it mostly transports Cl, it will hyperpolarise the cell when open.