C: Ascending Sensory Pathways 1 Flashcards

1
Q

What kind of modalities are carried in the spinothalamic pathway? 4

A

Modalities that are essential to survival:

1) Pain
2) Temperature
3) Some touch
4) Pressure

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2
Q

Modalities carried in the spinothalamic pathway are carried via neurons with what characteristics? How fast is conduction?

A

Thin, poorly myelinated or unmyelinated fibres

Conduction is slow

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3
Q

What kind of modalities are carried in the dorsal column pathway? 2

A

Modalities that increase detail:

1) Discriminative touch: 2-point discrimination and vibration
2) Proprioception

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4
Q

Modalities carried in the dorsal column pathway are carried via neurons with what characteristics, how fast is conduction?

A

Large diameter, heavily myelinated fibres

Fast conduction

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5
Q

General sensory pathways involve how many neurons?

A

3

A primary, secondary and tertiary

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6
Q

Where is the cell body of the primary neuron in a general sensory pathway located?

A

Ipsilateral dorsal root ganglion - outside the CNS

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7
Q

On which side does a primary neuron enter the CNS?

A

Same side as the receptor

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8
Q

Which neuron in a general sensory pathway crosses the midline?

A

Axon of the secondary neuron

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9
Q

In a general sensory pathway where does the cell body of a secondary neuron reside?

A

Ipsilateral grey matter of the CNS

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10
Q

In a general sensory pathway cell bodies of the tertiary neuron reside where?

A

In the contralateral thalamus

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11
Q

Axons of the tertiary neurons in a general sensory pathway project to where?

A

The somato-sensory cortex

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12
Q

Is synaptic transmission in a general sensory pathway a simple relay?

A

No, it can be modified by other inputs such as descending pathways

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13
Q

What 2 kinds of circuits can exist in the relaying of sensory information?

A

1) Diverging circuit - emphasises input

2) Converging circuit - diminishes input

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14
Q

In a spinothalamic pathway where does the axon of the secondary neuron cross the midline?

A

At the level that it enters the spinal cord - crosses anterior to the canal via the ventral white commissure

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15
Q

How does the axon of a secondary axon in the spinothalamic pathway ascend the spinal cord?

A

In the spinothalamic tract

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16
Q

Where do the primary and secondary neurons in a spinothalamic pathway synapse?

A

In the ipsilateral dorsal grey horn at the level of entry to the spinal cord

17
Q

What is meant by the statement that the spinothalamic tract is somatotypically organised?

A

Input from a specific sensory receptor will go to a specific region in the spinothalamic tract

18
Q

What name is given to the spinothalamic tract once it enters the brainstem?

A

The spinal/lateral lemniscus

19
Q

Where do primary and secondary neurons synapse in the dorsal column pathway?

A

In the cuneate and gracile tubercles

20
Q

Cuneate fascicle carries sensory info from approximately what level?

A

Above T6

21
Q

Gracile fascicle carries sensory info from approximately what level?

A

Below T6

22
Q

Where are the cell bodies of secondary neurons in the dorsal column pathway located?

A

In the gracile and cuneate nuclei (within the tubercles)

23
Q

How do the axons of primary neurons ascend the spinal cord in the dorsal column pathway?

A

In the ipsilateral cuneate or gracile fascicle

24
Q

Where are the cell bodies of tertiary neurons located in the dorsal column pathway?

A

Contralateral thalami

25
Q

At what level do the axons of secondary neurons cross the midline in the dorsal column pathway?

A

At the level of the closed medulla

26
Q

Axons of the secondary neurons in the dorsal column pathway cross the midline via what?

A

Internal arcuate fibres

27
Q

After crossing the midline fibres in the dorsal column pathway ascend to the thalami via what?

A

The medial lemniscus - which is somatotopically organised

28
Q

Which lies more lateral the cuneate fascicle or the gracile fascicle?

A

The cuneate fascicle

29
Q

Fibres travel from the thalami to the post central gyri via what?

A

The posterior limb of the internal capsule

30
Q

Do fibres carrying pain and temperature travel ipsilaterally or contralaterally in the spinal cord?

A

Contralaterally

31
Q

Do fibres carrying discriminative touch and proprioception travel ipsilaterally or contralaterally in the cord?

A

Ipsilaterally

32
Q

What kind of neuron is a primary neuron in a general sensory pathway?

A

Pseudounipolar

33
Q

Do all the fibres in the spinothalamic tract decussate at the level of entry to the spinal cord?

A

No, MOST do but some fibres ascend ipsilaterally for a few vertebral levels in the spinal cord before decussating, these are fibres in the spinothalamic tract carrying light touch and pressure sensation.