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PSHL231 Neurophysiology > Labs 5/6 > Flashcards

Labs 5/6 Flashcards

1
Q

Only … are active in low light levels?

A

Rods

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2
Q

Do rods or cones have longer phototransduction?

A

Rods

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3
Q

Why does your vision in a dark room become better after being in a dark room for period of time?

A

Time for rhodopsin to change from trans to cis - it takes time for this change to occur.

Dark adaptation - maximum rod sensitive takes about 25-30 minutes to occur.

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4
Q

Why do we have a slower reaction time in the dark?

A

Because rods are active and they have slower phototransduction than cones which are active in the light.

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5
Q

Why is there reduced visual acuity in rods?

A

Because rods transmit to retinal ganglion cells which have larger dendritic trees and larger receptive fields = less ability to discriminate.

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6
Q

What causes us to have a blind spot?

A

The optic disc where optic nerves exit and blood vessels enter and exit.

No ability to see light because there are no photo receptors there.

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7
Q

What is meant by normal vision is binocular?

A

That we see through two eyes

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8
Q

Why does binocular vision mean that we don’t see our blind spot?

A

Any image that falls on the nasal retina in one eye will fall on the temporal retina of the other eye - therefore the brain fills in the gap using information from the opposite eye.

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9
Q

What is convergence?

A

“Convergence” describes the way your eyes move together and point inward when you look at nearby objects.

Convergence required to keep the image situation with the fovea of each eyes retina when coming what your looking at comes closer.

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10
Q

What happens during accommodation?

A

Shifting and shaping of the lens for refraction.

Lens becomes more rounded to allow for greater refraction so the image was focused on the retina.

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11
Q

What states are the ligaments in when the ciliary muscles are relaxed?

A

Ligaments are tort

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12
Q

What lens corrects presbyopia?

A

A convex (converging) lens

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13
Q

What are the three components of the near response?

A

Convergence
Constriction
Accommodation

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14
Q

What stage of the near response is effected by age?

A

Accommodation due to loss of elasticity (presbyopia).

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15
Q

What is the most common form of colour blindness?

A

Red/Green colour blindness

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16
Q

What is a periscope?

A

Combination of mirrors that allows light from above the water to reflect into the submarine.

So you can see things above the water without submarine having to come up.

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17
Q

Do we see red light with rods?

A

No - red light does not activate photopigment in rods.

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18
Q

What light are submarines lit with?

A

Red light - means they can still see in the dark.

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19
Q

What events determine reaction time?

A

Formation of image on retina
Phototransduction
Retinal processing
Transmission to occipital lobe
Cortical processing
Motor program selection
Transmission
EC coupling
Cross - bridge cycling

20
Q

How long after events occur do we visually perceive them?

A

100 ms after the event

21
Q

Why do we have greater acuity when imagine is on fovea?

A

High concentration of cones on fovea.

Retinal ganglion cells are primarily fed by cones, which have small receptive fields therefore high acuity (discrimination).

22
Q

Where is blind spot located?

A

Optic disc - Within nasal retinal

23
Q

Why is red/green colour blindness more common in males?

A

because it is due to a mutation in opsin gene located on X chromosome

Recessive gene

In females, genes on the other X chromosome compensate so this type of colour blindness is less likely to manifest.

24
Q

Explain Hyperopia:

A

Long sightedness
Eye shorter so light falls behind the retina
Close objects unfocused (close up vision impaired)
Fixed by a convex lens which brings the light forward onto the retina.

25
Q

Explain Myopia:

A

Short sightedness
Eye longer so light falls in front of the retina
Far away objects unfocused (far vision impaired)
Fixed by a concave lens which pushes the light further back onto the retina.

26
Q

Does sweet taste adapt - explain?

A

Yes - the sweetness decreased over time.

This is because signalling through GPCR gets saturated and there is a potential depletion of secondary messengers. Therefore, fewer signals to the CNS.

27
Q

Does sour taste adapt - explain?

A

Sour taste does not change over time. This is because the signal transduction for sour taste is through ions channels. if there is a gradient fro H+ ions will keep entering the cell. Therefore the ion channels do not become saturated.

The change in pH affects K+ leak channels and blocks K+ exit.

28
Q

Why did the mixture solution taste less sour than the purely sour solution even though it had the same amount of sour?

A

Because the CNS prioritises sweet than sour so it overpower the sour taste (this is because sweet is an energy signal) = mixture suppression

29
Q

How does an adaptation to sweet affect the perception of subsequent sour tastes?

A

When we adapt to sweet it means our secondary messengers for sweet receptors are depleted and therefore less sweet signals to CNS and no more suppression of the sour sensation within the CNS.

30
Q

Why is warmer ice cream sweeter than colder ice cream

A

Increased activation of temperature sensitive action channel (TRPM5)

31
Q

Why is the perception of smell stronger for warm food/drink?

A

diffusion of odorant’s into gaseous phase is fast at higher temperatures.

32
Q

What is retronasal olfaction?

A

When odorant’s travel from mouth to nasopharynx and attach to olfactory receptors in nose - e.g., gives you a perception of smell even when nose might be blocked.

33
Q

What is the difference between compensated and uncompensated audiograms?

A

A compensated audiogram is an audiogram which has been compensated so the population average is at baseline 0.

An uncompensated audiogram is where the population average is set against absolute intensity and frequency values.

34
Q

What is impedance matching?

A

Amplification

35
Q

What are the two ways that energy transmission is enhanced (amplification)?

A

Tympanic membrane and ossicles

tympanic membranes - x20 larger than oval window and pressure at air side amplified to fluid side.

ossicles - acts as level system - amplify pressure wave from tympanic membrane to oval window.

36
Q

Did the lab use compensated or uncompensated audiograms?

A

Compensated

37
Q

What is the opposite of impedance matching?

A

The dampening of loudness via muscles attached to bones to remove them from off the tympanic membrane.

38
Q

What are the two main functions of the eustachian tube (nose to ear)?

A

Equalises pressure between the middle ear and atmosphere

Aeration (exposure to air) and clearance of middle ear by draining fluid and mucus to reduce likelihood of middle ear infection

39
Q

Why are infants more likely to get a middle ear infection?

A

because their Eustachian tube is more horizontal therefore less efficient at draining fluid

40
Q

Is the basal or apical end of a basilar membrane narrow?

A

Basal end = narrow and stiff = oscillates at high frequency sound waves = high pitch is percieved

Apical end = wide and flexible = oscillates at low frequency sound waves = low pitch is perceived

41
Q

How is loudness detected?

A

Produce larger amplitude vibrations of basilar membrane
= more activation of hair cells
= results in higher rate of AP firing on afferent neurons

42
Q

Why does the sensation of rotation decline with time?

A

Acceleration stops (movement without acceleration).

therefore the endolymph catches up - cupula restored - sterocilia in resting position - AP at rest.

43
Q

When you first start to spin what is happening?

A

Angular acceleration - bones move but endolymph fluid has inertia (stays where it is) caused bending of cupulla - sterocilia on hair cells bend towards kinociium causing increase AP firing.

44
Q

What direction of motion is felt when you stop spinning?

A

Motion felt in opposite direction of the previous spinning movement.

45
Q

What is the eye movement after spinning called and why does it happen?

A

Nystagmus (eyes flickering back and forth) - occurs because eyes trying to compensate for signalled head movement - attempting to keep our visual world in focus as we spin.

Signal transduction of eyes slower than vestibular so they haven’t yet realised that we are not moving anymore.

46
Q

What is coriolis illusion?

A

What happened when tilted head - which changes the axis in vestibular system.

The misperception of body orientation due to head movement while under the effect of rotation, often inducing nausea. This effect comes about as the head is moved in contrary or similar motion with the body during the time of a spin.

47
Q

is the saccule horizontal or vertical?

A

Saccule is Vertical

Utricle is Horizontal

PSHL231 Neurophysiology (10 decks)

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