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INTRO TO NEUROSCIENCE - COGS1000 > final > Flashcards

final Flashcards

1
Q

explain the net effect of photo transduction in dark conditions

A
  • depolarising inward currentt (influx of Na+ and Ca2+)
  • hyperpolarising outward current (efflux of k+)
    net effect = depolarisation of photoreceptors in dark
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2
Q

explain the net effect of phototransduction in light condiiotns

A
  • depolarising inward current blocked (Na+ and Ca2+ channels are closed)
  • hyperpolarising outward current (efflux of k+ ions)
    net effect = hyperpolarisaiotn of photoreceptors in light
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3
Q

what makes up the right visual field

A

temporal portion of the right eye

nasal poriton of left eye

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4
Q

what makes up the left visual field

A

temporal portion of left eye

nasal portion of right eye

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5
Q

what does a lesion in the right optic nerve result in

A

loss of vision to the eye of origin (right eye)

- as the info has not crossed over yet so only in the eye effected - the nerve only carries info from one eye

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6
Q

what does a lesion in the right optic chiasm result in

A

affects nasal retina acosn from each that cross to the contralateral side leaving uncrossed from the temporal iin tract - (nasal sees temporal)

bitemporal heminopsia

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7
Q

what does a lesion in the right optic tract result in

A

as lesion is on riight side, lose left visual field

left homologous heminospia

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8
Q

what does a lesion in the right myers luc result in

A

lose info from the left superior visual field on both eyes

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9
Q

what does a lesion in the visual cortex result in

A

loss it left hand side of both eyes - however fovea is spared
left homoymous heminsopsia with macula sparing

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10
Q

what is the main featture of lower motor neurons

A

innervate muscles

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11
Q

where does the corticobulbar tract originate and terminate

A

originate in M1 and terminate in brainstem

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12
Q

what muscles is the corticobulbar tract control?

A

muscles of face and enck, mastication, swallowiing…

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13
Q

where does the corticospinal tract originate and terminate

A

originate in M1 and terminate in spinal cord

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14
Q

what muscles is the corticopsinal tract control?

A

proximal and distal limb muscles

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15
Q

what happens with 90% of corticospinal axons

A

they cross the body midline (decussate) in medulla and fronm lateral corticospinal tract

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16
Q

what happens with 10% of corticospinal axons

A

terminate ipsiillaterally or bilaterally and from the ventral corticospinal tract

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17
Q

what does the VOR compensate for?

A

VOR compensates nealry perfectly for rapid head movments at 1hz>

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18
Q

what does VOR gain refer to

A

ratio of eye to head movemtn

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19
Q

what does OKR compensate for?

A

OKR compensates for nealry perfeclty for low frequency around 0.1hz

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20
Q

what is OKR gain

A

ration of eye movement to retinal image motion

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21
Q

what is the superior colliculus and frontal eye fields important for?

A

they play an important role in planning an initiating saccades to visual targets

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22
Q

what is myopia

A

= near sighted, image falls In front of the retina

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23
Q

what is the cornea

A
  • cornea: transparent tissue that permits light rays to enter the eye
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24
Q

what is hyperopia

A
  • hyperopia (far sighted) = light rays are focused beyond the retina
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25
Q

what does damage to the retina cause

A
  • damage to this region results in loss in acuity and distortion of central vision – progressing to blind spots and later complete loss of vision
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26
Q

what is the msot common cause of vision loss in people over 55

A

macular degeneration

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27
Q

what causes macular degeneration

A

by degeneration of photoreceptors

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28
Q

what do bipolar cells do

A

give a graded response not action potential

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29
Q

what do ganglion cells do

A

go out of optic disc, via optic nerve to brain

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30
Q

what do horizontal cells do

A

modulate the reaction between photoreceptor and bipolar cells

31
Q

what do amacrine cells fo

A

modulate the reaction between bipolar cells and ganglion cells

32
Q

what is the biochemical process when light hits

A

biochemical process when light hits:

  • photon absorbed by retinal  changes the configuration
  • this change causes changes to opsin which:
  • activates transducin ( intracellular messenger)
  • activates phophodiesterase (PDE)
  • hydrolyses cGMP  less cGMP
33
Q

what does rods and cones differ in?

A
  1. shape – rod-like vs cone-like
  2. photopigment – and therefore their response characteristics
  3. pattern of synaptic connections – which determines spatial acuity
    - rods – convergence from rods to rod bipolar cells: pools the signal (hence, low light vision)
    - rod bipolar cells synapse on amacrine cells
    - these amacrine cells synapse on cone bipolar cells and in turn the ganglion cells
  4. distribution across retina – rods in the periphery, cones in the fovea
    - cones: through at low density, packed into fovea, high special activity
    - rods: throughout periphery, none in the centre, low spatial acuity
34
Q

how many pigments does rods contain

A
  • rods contain a single photopigment (rhodopsin)
35
Q

how many pigments does cones contain

A

3 differnet types of photopogment

36
Q
  1. Describe two differences between photoreceptors and other sensory cells.
A

Just like other sensory cells (e.g. bipolar cells or ganglion cells), photoreceptors are a class of neuron that is found in the retina. What makes photoreceptors unique is that they are found on the deepest layer of the retina. Another difference is that photoreceptors exhibit a graded change in membrane potential in response to light instead of action potential and hyperpolarise in the presence of light.

37
Q
  1. What is light adaptation in the retina and why is it so important?
A

Light adaptation is a phenomena and is the process of the compensating for an increase illumination. This compensation is important as due to the illumination increasing, sensitivity decreases (as photoreceptors are most sensitive to light at lower levels of illumination), preventing the receptors from saturating and thereby extending the range of light sensitivities they operate at.

38
Q
  1. What are the advantages of animals having both rods and cones, rather than just one type of photoreceptor.
A

There are a variety of significant advantages of animals having 2 types of photoreceptors. The most significant benefit is that rods and cones are used for different purposes. Rods are found in periphery and they respond well under low light vision or night vision. Cones are found in central vision region and are 3 types which each detect light at different wave lengths. Therefore, by having both rods and cones animals are able to see and process visual stimuli across a broad range of light conditions.

39
Q
  1. Explain the concept of feedforward postural control and provide one example. In your answer, explain what is predictive or anticipatory about the feedforward postural control.
A

Feedforward postural control is a “preprogramed” response that involves activation of leg and trunk muscles prior to an expected body perturbation. Feedforward postural control is typically anticipatory, meaning the response predicts instability hence prepares for that instability before it occurs. Both the vestibular nuclei and reticular formation play a role in providing information to the spinal cord to maintain posture however in the feedforward control reticular formation has the greatest contribution. The relevant neurons in the reticular formation initiate feedforward adjustments that stabilise posture during ongoing movements. For example, if an individual was to pull a handle with his arm to trigger an auditory tone, activity in the biceps begin 200ms after the tone, but a proximal leg muscle, the gastrocnemius muscle activity actually began prior to the bicep highlighting how we can anticipate instability in our posture and compensate for that instability.

40
Q
  1. How do neurons in the abducens nuclei control the amplitude and direction of an eye movement.
A

In order for the eyes to fixate on a new target in space two tasks must be achieved by the neurons in the abducens nuclei: controlling the amplitude of the movement and controlling the direction of the movement. Amplitude of the saccadic eye movement is encoded by the duration of neuron activity in the lower motor neurons. Neurons in the abducens nucleus fire a burst of action potentials just prior to abducting the eye and are silent when the eye is adducted. The amplitude of the movement will then be correlated with the duration of the burst of action potentials in the abducens neurons. Direction of movement is controlled by two gaze centres in reticular formation which determine which eye muscles are activated. The Paramedian pontine reticular formation (PPRF) is a collection of local circuit neurons in the midline of the pons and these are the neurons responsible for generating horizontal eye movements. In the PPRF, neurons innervate the cells in the abducens nucleus which contains 2 types of cells. One type of the cells is composed by lower motor neurons that innervate the lateral rectus muscle on the same side and the other type called internuclear neurons send their axons across their midline leading to the medial rectus muscle being innervated. Therefore the neurons in the abducens nuclei are responsible for controlling the amplitude and direction of eye movements.

41
Q
  1. First, identify each of the association cortices. Second, describe the main function of each associative areas and some of primary symptoms that patients with damage in this area might show.
A

The association cortex (including the frontal, parietal and temporal lobes) brings together sensory and much other information to produce useful behaviour whatever the circumstance may be. Each lobe within the association cortices plays a different role and deficits in those areas result in different symptoms. The parietal lobe is primarily responsible for mediating attention as well as a sense of where things are. Damage to this area would cause contralateral neglect syndrome, which is classified as an inability to attend to objects or even one’s own body, in a portion of space, however an individual’s visual acuity, somatic sensation and motor ability remain intact. If the left parietal lobe is damage it is more severe and the individual can only see the right side as only the left lobe is being used, however, if the left lobe is damaged the right will take over the whole field. The main function of the temporal lobe is that is especially important for recognising objects and conditions therefore damage to this region will result in agnosia, the difficulty in recognising, identifying and naming objects – individuals acknowledge the presence of something but cannot identify it. The most studied agnosia is prosopagnosia which is the inability to recognise faces. The frontal association cortex is especially important for electing and planning appropriate behavioural responses. Damage to the frontal lobe can cause a variety of symptoms however the greatest would be that individuals lose their “personality”. The first case of this was Phineas Gage who had suffered a rod going through his left eye socket destroying his frontal lobe. Even after recovery those who knew Phineas said his personality completely changed and was not the same personality.

42
Q

in what wat are ion channels simnilar to active transporters

A

both miantian ion concentration gradietns

43
Q

which property is chaacteristic of NA+ channels but not K+ channels

A

ability to inactivate

44
Q

which substacne binds only to the extracellular domain of ligand gated ion channels?

A

neurotransmitters

45
Q

what is scoptic vsiion

A

low ligth

46
Q

if you have a lesion in hte right optic tract your vision loss will afect

A

the left side of space

47
Q

where do ganglion cells cross at

A

optic chiasm

48
Q

what neurons innervate striated

A

alpha motor neurons

49
Q

what neurosn innervate specilsied fibresa

A

gamma motor neurons

50
Q

which motor units are resistant to fatigue

A

slow and fast fatigue resistant

51
Q

according to the size principle, in which order are motor units recruited in response to increasing synaptic input

A

slow, fast fatigue-resistant, fast-fatiguable

52
Q

motor neuorns with cell bodies in the cerebral cortex and brainstem are parrt of which motor system

A

upper motor neurons

53
Q

what layer of the primary motor cortex are located in which cortical layer

A

5

54
Q

the peripheral msucle group that an upper motor neuron projects to is the

A

muscle field

55
Q

what structure can be found exclusively at an electrical synapse

A

connexon

56
Q

what is a connexon

A

assembly of proteins that form the pore for a gap junction between the cytoplasm of two adjacent cells

57
Q

what is the action fo the neurotransmitter at a chemical synapse

A

it transfers an action potential sform the presynaptic neuron to the postsynaptic neuron

58
Q

what is the main excitatory neurotransmitter in the adult brain

A

glutamate

59
Q

on the way to the retina, light passes through tissues and fluids in which order

A

cornea, aqueous humor, lens, vitreous humour, retina

60
Q

during accomodation, the shape of the _____ is change dby the ______ in order to see objects are varying distances

A

lens, ciliary muscle

61
Q

what does convergence allow?

A

rods to pool signals generating larger reposnes in bipolar cells

62
Q

where does ganglion cells cross

A

optic chiasm

63
Q
  • loss of colour vision
  • retina is still functioning
  • sees shades of grey
    He most likely systained damage to what area?
A

v4

64
Q

damage to the striate cortex below the calcarine sulcus would result in diffculty processing information from whcih visual field

A

superior

65
Q

object in the superior temporal quadrant of hte visual field would be mapped on what quadrant of the retina

A

inferior nasal

66
Q

what system is responsible for the processing info regarding self motion, head positon, and spatial orientation

A

vestibular

67
Q

what type of movement does the saccule respond to?

A

vertical

68
Q

what type of movement does the utricle respond to

A

horizontal

69
Q

as motor unit size increases, which property of the alpha motor neuron decreases

A

excitability

70
Q

what technique is helpful in mapping primary motor cortex

A

cortical stimulation

71
Q

what percentage of pyramidal tract fibres decussate to form the lateral corticospinal tract

A

90%

72
Q

what is the muscle field

A

the group of muscles whose activity is directly facilitated by a giver upper motor neuron

73
Q

how are the upper motor neurons in the superior colliculus organised

A

as a topographical map of eye movement vectors

74
Q
  1. What are the distinct characteristics (both function and structure) of magnocellular versus parvocellular streams?
A

There are many differences between magnocellular and parvocellular pathways. Magnocellular layers are made of 2 layers composed of large neurons whereas the parvocellular layers is made of 4 layers with much smaller neurons. M ganglion cells terminate in the Magnocellular pathways and have larger receptive fields, faster conduction and are insensitive to different wave lengths of light. P ganglion cells terminate in the parvocellular pathways – they have smaller receptive fields, closer conduction, sustained responses, sensitive to differences in wave lengths and are involved in colour not motion. The magnocellular pathway conveys information that is critical for the detection of rapidly changing stimuli whilst the parvocellular pathway mediates high acuit

INTRO TO NEUROSCIENCE - COGS1000 (3 decks)

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