Somatic sensation and ascending pathways Flashcards

1
Q

What is a sensory modality? Give general somatic sensory examples

A
How a stimulus is perceived
temperature
pain
pressure/crude touch
vibration 
fine touch
proprioception
2 point discrimination
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2
Q

What determines the sensory modality

A

The type of receptor

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3
Q

What modality is wetness?

A

It is a combination of modalities (e.g. temp and fine touch)

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4
Q

Briefly describe the route of a primary sensory neurone

A

Cell body is found in the dorsal route ganglion

Crosses from PNS to CNS

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5
Q

Briefly describe the route of a secondary sensory neurone

A
Cell body is found in the spinal cord (sometimes brainstem)
Crosses midline (decussates)
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6
Q

Briefly describe the route of a tertiary sensory neurone

A

Cell body is found in the thalamus

Projects to the primary sensory cortex

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7
Q

Briefly describe the types of primary neurones

A

Rapidly adapting- signal degenerates over time
e.g. mechanoreceptors in the skin
Slow adapting- signal frequency doesn’t decay
e.g. nociceptors (pain transmission)

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8
Q

What is a receptive field

A

The area of skin that a sensory neurone collects information from

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9
Q

What is the relationship between acuity and the receptive field?

A

Inversely proportional

Smaller receptive field= greater acuity

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10
Q

What is the clinical significance of receptive fields overlapping?

A

Determine dermatomal sensation in the middle of the dermatome, where it is less likely there will be any overlap

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11
Q

Briefly describe two benefits of the orderly and parallel way in which the corresponding CNS is organised

A

Requires minimum amount of ‘building material’ e.g. axons, myelin, neurones
Converts information from dermatomes into the homunculus

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12
Q

What system is the modality of pain relayed to the cortex by?

A

Spinothalamic (anterolateral) system

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13
Q

What system is the modality of crude touch relayed to the cortex by?

A

Spinothalamic (anterolateral) system

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14
Q

What system is the modality of temperature relayed to the cortex by?

A

Spinothalamic (anterolateral) system

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15
Q

What system is the modality of fine touch relayed to the cortex by?

A

Dorsal column system

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16
Q

What system is the modality of 2 point discrimination relayed to the cortex by?

A

Dorsal column system

17
Q

What system is the modality of vibration relayed to the cortex by?

A

Dorsal column system

18
Q

Briefly describe the medial lemniscus

A

Connects the gracile and cuneate nucleus with the thalamus

19
Q

What is the cervical nucleus in the dorsal column called?

A

Cuneate nucleus

20
Q

What is the lumbar nucleus in the dorsal column called?

A

Gracile nucleus

21
Q

How are neurones added on as they travel up the dorsal column? How is this drawn topographically?

A

Neurones are added laterally
Lumbar is most medial, and cervical is most lateral
(Check cross sectional diagram with notes)

22
Q

How are neurones added on as they travel up the spinothalamic tract? How is this drawn topographically?

A

Neurones are added medially
Lumbar is the most lateral, and cervical is the most medial
(Check cross sectional diagram with notes)

23
Q

Briefly describe where the primary and secondary sensory neurones synapse in the spinothalamic system

A

In the spinal cord, near the same level the primary neurone entered the spinal cord

24
Q

What is the spinothalamic tract?

A

The tract connecting the spinal cord to the thalamus

25
Briefly describe why you rub an area of pain
Stimulates mechanoreceptors Stimulates A-Beta fibres Stimulates inter neurone Inhibits secondary sensory neurones
26
Briefly describe what happens during hypnosis to reduce pain
Stimulates excitatory cortical neurone Acts on periaqueductal grey in midbrain This then synapses at the nucleus raphe magnus This then stimulates inhibitory interneurones
27
Briefly describe how proprioception works
Muscle spindles report muscle length | There are also receptors in joints
28
Briefly describe lissauer’s tract
It allows first order sensory neurones of the spinothalamic tract to ascend or descend before decussating