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CNS Physio > Lecture 3 > Flashcards

Lecture 3 Flashcards

1
Q

The Anterolateral System (Spinothalamic Pathway System) tract ascends in the ___ and ___ columns of spinal cord.

A

Anterior and lateral

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2
Q

How many modalities does the Dorsal Column System transmit?

A

Only one: mechanoreceptive

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3
Q

What kind fibers does the Anterolateral System (Spinothalamic Pathway System) use?

A

Small, myelinated and unmyelinated fibers for slow transmission (0.5-40 m/sec) (A𝛿 and C fibers).

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4
Q

How many modalities does the Anterolateral System (Spinothalamic Pathway System) transmit?

A 
A broad spectrum:
1) Pain
2) Thermal sensations
3) Crude touch
4) Crude pressure
(crude because poorly localized)
5) Tickle and itch
6) Sexual sensations.
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5
Q

The Anterolateral System (Spinothalamic Pathway System) has a __(low/high) degree of spatial and temporal orientation. Why?

A

Low; because of the slow conducting fibers and lots of divergence.

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6
Q

Why is pain an important sensation?

A

It’s protective and tells you to stop the damage by stopping the damaging stimuli.

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7
Q

What is the pathway of the Anterolateral System (Spinothalamic Pathway System)? (Until the second order neuron)

A

1) The afferent neurons (first order neurons) enter the spinal cord to the
posterior horn .
2) In the posterior horn, the first order neuron synapses with second order
neuron.

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8
Q

What is the pathway of the Anterolateral System (Spinothalamic Pathway System)? (Until the end)

A

1) The second order neuron goes 1 or 2 segments up or
down then crosses (decussates) to the other side of spinal cord [The
crossing occurs anterior to the central canal].
4) The second order neuron ascends either in anterior or lateral column of
spinal cord to reach the ventrobasal part (VPL, VPM) of the thalamus.
5) In the thalamus, the second order neuron synapses with the third order neuron
6) The 3rd order neuron goes to postcentral gyrus (primary somatosensory area).

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9
Q

Pain signals follow the same journey in the Anterolateral System (Spinothalamic Pathway System), BUT:

A

Instead of the second order neuron reaching the ventrobasal part of the thalamus, it goes to intralaminar nuclei.

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10
Q

The Anterolateral System (Spinothalamic Pathway System) conveys nerve impulses to:

A

The postcentral gyrus of the cerebral cortex.

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11
Q

What does modality mean?

A

Type of sensation

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12
Q

The dorsal column is __(well localized/poorly localized), while the anterolateral is column is __(well localized/poorly localized).

A

Well localized; poorly localized)

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13
Q

The higher the speed of transmission, the higher the ___.

A

Degree of spatial orientation.

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14
Q

The dorsal column has a ___(low/high) degree of temporal and spatial faithfulness, while the anterolateral is column has a ___(low/high) degree.

A

High; low

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15
Q

Which has a better intensity gradation and why? The dorsal column or the anterolateral column?

A

The dorsal column, because faster signal transmission = less differences between stimuli.

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16
Q

In which tracts do repetitive stimuli confine to? Why?

A

The dorsal column tracts because it transmits signals at a higher speed.

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17
Q

Which has a more modalities? The dorsal column or the anterolateral column?

A

The anterolateral column.

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18
Q

Where does the second order neuron decussate in the dorsal column system?

A

At the level of the brain stem (medulla oblongata)

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19
Q

Where does the second order neuron decussate in the anterolateral column system?

A

At the level of spinal cord.

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20
Q

What is the trigeminothalamic pathway special for?

A

Sensations from the face area.

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21
Q

What kinds of sensations does the trigeminothalamic pathway transmit?

A

All kinds of sensations (fine and crude).

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22
Q

The trigeminothalamic pathway conveys nerve impulses to the __.

A

Cerebral cortex

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23
Q

Where does the afferent neuron go to synapse in the trigeminothalamic pathway?

A

To the nuclei of the trigeminal nerve.

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24
Q

Where does the afferent nerve go after synapsing in the trigeminothalamic pathway?

A

It crosses to the other side and goes to the VPL in the thalamus.

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25
Q

Where does the afferent nerve go after reaching the thalamus in the trigeminothalamic pathway?

A

To the somatosensory

cortex (post central gyrus).

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26
Q

In dorsal column tract, If the damage/transection is below the level of medulla, the loss of sensation is ___.

A

Ipsilateral (at the same side of damage).

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27
Q

In anterolateral tract, If the damage is below the level of medulla, the loss of sensation is ___.

A

Contralateral (at the opposite side of damage).

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28
Q

In both systems, If the damage is above the level of medulla, the loss of sensation is ___.

A

Contralateral (at the opposite side of damage).

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29
Q

Where is the Somatic Sensory Cortex located?

A

In the postcentral gyrus.

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30
Q

The Somatic Sensory Cortex contains highly organized distinct ___.

A

Spatial orientation.

31
Q

Each side of the cortex receives information from the __(same/opposite) side of the body .

A

Opposite

32
Q

The Somatic Sensory Cortex has __(equal/unequal) representation of the body.

A

Unequal

33
Q

Which area of the body has the highest representation in the Somatic Sensory Cortex?

A

Lips

34
Q

Which area of the body has the second highest representation in the Somatic Sensory Cortex?

A

Face

35
Q

Which area of the body has the third highest representation in the Somatic Sensory Cortex?

A

Thumb

36
Q

Why do the lips have the highest representation in the Somatic Sensory Cortex?

A

Because they have a very large number of receptors

37
Q

Which areas of the body have the lowest representation in the Somatic Sensory Cortex?

A

The trunk and lower body.

38
Q

Why do the trunk and lower body have the lowest representation in the Somatic Sensory Cortex?

A

Because they have a very low number of receptors

39
Q

How many layers are found in the cortex?

A

6

40
Q

Layer 1 is found ___, while layer 6 is found ___.

A

Near the surface of the cortex; Deep within the cortex

41
Q

Incoming signals enter which layer of the cortex?

A

Layer 4 (They spread both up and down)

42
Q

What do layers 1 and 2 of the cortex receive?

A

Diffuse input from lower brain centers.

43
Q

What do layers 2 and 3 of the cortex do?

A

Send axons to closely related portions of the cortex probably for communicating between similar areas.

44
Q

What do layers 5 and 6 of the cortex do?

A

Send axons to more distant parts of the nervous system

45
Q

Where does layer 5 send axons to (specifically)?

A

The brainstem and spinal cord

46
Q

Where does layer 6 send axons to (specifically)?

A

The thalamus

47
Q

How are the neurons arranged within the layers of the cortex?

A

In columns.

48
Q

Each column of neurons serves:

A

A specific sensory modality

49
Q

Different columns are __ among each other.

A

Interspersed

50
Q

Interaction of the columns occurs at ___, which allows for the:

A

Different cortical levels; beginning of the analysis of the meaning of the sensory signals.

51
Q

What does the destruction of somatic area 1 result in?

A

1) Loss of discrete localization ability.
2) Inability to judge the degree of pressure.
3) Inability to determine the weight of an object.
4) Astereognosis.
5) Inability to judge texture.

52
Q

What is Astereognosis?

A

Inability to determine the shape or form of objects.

53
Q

Where are the somatic association areas located?

A

Behind the somatic sensory cortex in the parietal area of the cortex.

54
Q

Where do the somatic association areas receive inputs from?

A

1) The somatic sensory cortex
2) The ventrobasal nuclei of the thalamus (ventroposteriolateral-VPL-and
ventroposteromedial-VPM-)
3) The visual and auditory cortex.

55
Q

What is the function of the somatic association areas?

A

To decipher sensory meaning; it has a high level of interpretation by knowing where this area is compared to the other areas and forming 3D position of the sensation.

56
Q

What happens if we lose the somatic association areas?

A

1) The inability to recognize complex objects
2) Loss of self (Amorphosynthesis)
3) Inability to form the shape of the objects.

57
Q

The thalamus has some ability to discriminate tactile sensation, because:

A

Some of the neurons end in the thalamus.

58
Q

What is the role of the thalamus?

A

The perception of pain and

temperature

59
Q

If the postcentral gyrus is damaged, what can a person still feel?

A

Pain, temperature, and a bit of tactile sensations.

60
Q

What are corticofugal fibers?

A

Descending fibers from the cortex back to the sensory

61
Q

What do the corticofugal fibers relay?

A

Areas of the:

1) Thalamus
2) Medulla
3) Spinal cord.

62
Q

Corticofugal fibers are ___(inhibitory/excitatory); they

A

Inhibitory; suppress the sensory input (negative feedback)

63
Q

What is the function of corticofugal fibers?

A

1) To decrease the spread of a signal
2) Sharpen the degree of contrast of a signal
3) Adjust the sensitivity of the system

64
Q

What is a weak stimulus?

A

Able to stimulate the central part of the cerebral cortex cells (few number)

65
Q

What is a moderate stimulus?

A

Able to stimulate a larger number of cortical cells

66
Q

What is a strong stimulus?

A

Able to stimulate a very high number of cortical cells

67
Q

If there is lateral inhibition, then 2 points will feel as:

A

2 points

68
Q

If there is no lateral inhibition, then 2 points will feel as:

A

1 point

69
Q

The more the intensity. the more the ___.

A

Receptor potential = more number of impulses

70
Q

A stronger stimulus is perceived as

stronger, due to:

A

Higher number of impulses

71
Q

When does the power law not hold?

A

At either very weak or very

strong stimulus strength.

72
Q

Where is the highest sensitivity area? (Imagine the power law graph)

A

In the middle

73
Q

What is the function of the corticofugal fibers on the power law curve?

A

To bring down the stimulus from the plateau phase (low sensitivity area) to the middle (high sensitivity area)

74
Q

How do we know whether we’re flexing or extending?

A

When you change the angle of a joint, some neurons transmit more impulses while others transmit less impulses.

CNS Physio (8 decks)

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