Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

PNB 2XB3 (Neuroanatomy) > Lecture 5 > Flashcards

Lecture 5 Flashcards

1
Q

Anatomy of the human eye

A

Cornea

Pupil
- expands or dilates depending on light due to iris

Lens
- curved and brings light to focus

Retina
- sensory region of the eye

Optic nerve
- 1 million axons
- goes back to thalamus

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Emmetropia, myopia, hyperopia

My friends are near, they are around

A

Emmetropia
- normal vision
- focus point on retina

Myopia
- nearsighted
- lens too curved or eyeball too long
- focus point in front of retina

Hyperopia
- farsighted
- lens not curved enough or eyeball too short
- focus behind the retina
= think of cornea and eye as entire eyeball squished

Friends far = you long for them

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Snell’s law

A

n1Sinθ1 = n2Sinθ2

θ is the angle relative to the normal / vertical line

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Snell’s law - sample n

A

if n2 > n1

θ2 is smaller

Smallest n
vacuum
air
water
cornea
lens
diamond
Biggest n

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Bending line with a curved surface - cornea

A

more curved / round cornea
= light bends more

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Lens vs Cornea

A
  • Cornea bends light but it is not adjustable
  • Lens is the one that brings the light into focus by moving and bending light
  • Cornea bends light more than the cornea bc the density of the cornea is compared to the density of air → much bigger difference
    But once it gets into the eye, it’s in the vitreous humour (basically water)
  • Cornea bends the light a lot, lens fine tunes it
  • Cornea has greater focusing power
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Flippy retina

A
  • What hits your retina is upside down and left to right switched
  • Your brain knows how to interpret the image and flip it back
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Inside-out retina

A

Light
1. Retinal ganglion cells = neurons
2. Bipolar cells
3. Photoreceptors = rods and cones absorb light
Optic nerve

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

The blind spot

A
  • no photoreceptors where 1 million axons converge
    = optic disk

near the nasal retina

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Structure and function of the retina - photoreceptors and RPE

A
  • Photoreceptors make a voltage change
  • 2 main types rods and cones
  • Outer segment and cell body
  • In outer segment a bunch of disks filled with molecules called photopigments that absorb light

RPE
- pigment epithelium cells
- absorbs light so it doesn’t bounce = prevents blurring
- nourishes the photoreceptors

  • photoreceptors at the back so they can access RPE
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Pulse chase experiment - disks move over time

A

Injected a radioactive AA (3H methionine)
→ looked at different time point
→ could see where the radiation was
→ gets taken up into proteins
→ over the course of a few week migrate into retinal epithelium
→ shed their disks into retinal epithelium and add new ones in

3H: tritium
methionine: amino acid

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Why do we shed photoreceptors disks

A
  • light is damaging to tissue
  • damages molecules in the disks
  • phagocytosis swallowed by the RPE, degraded and recycled
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Phototransduction

A
  • physical stimulus (light) converted into nervous system response
  • done by photoreceptors
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Whole-cell patch clamp for hyperpolarization of photoreceptors

A

Result
- light causes photoreceptor hyperpolarization (depolarization in the light)

hyperpolarization = inward current

brighter light = hyperpolarizes more

  • doesn’t matter for AP, just a signal
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Photoreceptor ______ in the dark

A

depolarized

+ charge enters the cell
Na, Ca enter, K leaves
- current
current reduced by the light flash

Ca/Na ions enter through channels controlled by an intracellular ligand

K through leak channels

cGMP = cyclic guanosine monophosphate
- opens channel and lets ions flow in

  • neurotransmitter glutamate released in dark and binds to bipolar cells
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Photoreceptor ______ in the light

A

hyperpolarized

same as dark but less Na and Ca enter, K still leaves

  • this is because cGMP degraded when the photoreceptor absorbs light
  • cGMP usually binds to let in Ca and Na

graded action potential
Ca closed so no/little neurotransmitter release

17
Q

Photoisomerization

what in which protein

A
  • opsin proteins
  • rhodopsin in rods

retinal in opsins
- ret absorbs light
- conformational change forming an isomer
- is a form of vit. A
- absorbs light = chromophore

changes shape of retinal cis to trans

18
Q

Phototransduction

A
  • photoisomerization of retinal in opsin
  • activates transducin enzyme
  • transducin activates phosphodiesterase (PDE)
  • breaks down cGMP
    = ion channels close
19
Q

Photoadaptation

A
  • hyperpolarize when light first turns on but slowly depolarize
  • reduction due to sustained constant response
  • when cGMP not there and ion channels close, less Ca inside cell
  • Ca usually inhibits guanylate cyclase function
  • guanylate cyclase is an enzyme that produces cGMP

no more inhibition = produces cGMP again = channels reopen
- causes depolarization

20
Q

Phototransduction and adaptation loop

A

Transduction
- Light
- phosphodiesterase activated
- cGMP down
- close Na and Ca channels
- hyperpolarization

Adaptation
- guanylate cyclase activated
- cGMP up
- open Na and Ca channels
- depolarization

21
Q

Colour - rods and cones graph

A

three different types of cones

smallest wavelength / purple
- short cones (blue)
- rods (greyscale)
- medium cones (green)
- long cones (red)
red / largest wavelength

brain infers colour from the relative activation of the three cone types

22
Q

Rods vs. cones - 3 reasons for light sensitivity

A

Most sensitive to light
= rods

Length
- longer so they contain more photopigment
- sensitive enough to see at night

Convergence
- many rods converge onto the same bipolar cell so there is a higher probability that one of them will see the light

Amplification
- have greater amplification, close more Na channels in response to same amount of light absorbed
1 photon = 1mV hyperpolarization
- cones need 100 photons to have the same effect

23
Q

Rods vs. cones - 2 reasons for spatial acuity

A

Better spatial acuity
= cones

  • cones densely packed at the fovea which lacks blood vessels and axons on top of it = no light scattering
  • less convergence, knows exactly where signal came from
24
Q

General rod/cone differences

A

Rods
- eccentric
- 1 type
- grayscale
- high sensitivity
- low spatial acuity
- 90 million

Cones
- central
- 3 types
- colour
- low sensitivity
- high spatial acuity
- 4.5 million

25
Q

Discovering distribution of cone types in the retina

A
  1. flash with yellow = reflected with blue, absorbed red and green
  2. bleach with red to eliminate red function, flash with yellow and only green will absorb
26
Q

On-center and off-center retinal ganglion cells

A

On-center
- turns on when light is on in their center
- does the opposite of cone
- weird glutamate receptor
- metabotropic glutamate receptor mGluR6
- glutamate causes mGluR6 to close Na channel
= glutamate is inhibitory
= depolarize in light

Off-center
- turns off when light is off in their center
- does the same as cones
- normal ionotropic glutamate receptor (glutamate makes Na channel open)
= hyperpolarize in light

27
Q

Ionotropic versus metabotropic glutamate receptors

A

Ionotropic
- neurotransmitter binds to channel
- channel opens
- ions flow across membrane

ex. glutamate (AMPA) receptor, GABA (A) receptor

Metabotropic
- nt binds to receptor
- activates G-protein
- G-protein subunits go to effector proteins
- then send intracellular messengers
- cause channel to open or close
- ion flow

28
Q

Biolistic transfection

A

biology + ballistic

  • like a BB gene gun shooting DNA particles into a neuron
  • gold particles covered with DNA, in tubes
  • shoot into neuron
  • some happen to land in nucleus and get transcribed
    = neuron will make the protein
29
Q

Biolistic transfection - example with retinal ganglion cells

A

morgan, schubert, wong

  • put genes for 2 fluorescent proteins into mouse retinal ganglion cells
  • using biolistic transfection
  • used to show what the cells look like and where their glutamate receptors are

Fluorescents
1. td-tomato fills cytosol (orange)
- done with gene gun

  1. PSD-95 found around glutamate receptors (green)
    PSD = postsynaptic density
  • can be digitized using a computer program to get rid of confusing dots, only show probable receptor dots with specific traits

PNB 2XB3 (Neuroanatomy) (5 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions