Somatic Sensory System Flashcards

1
Q

How can nerve endings be classified?

A

Encapsulated and unencapsulated

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2
Q

Give 3 examples of encapsulated nerve endings

A
  • Meissner(tactile) corpuscles
  • Pacinian (lamellate) corpuscles
  • Ruffini corpuscles
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3
Q

What are Pacinian corpuscles involved in?

A

Deep pressure, stretch, tickle, vibration

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4
Q

What are Meissner corpuscles involved in?

A

Light touch/texture

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5
Q

What are Ruffini corpuscles involved in?

A

Heavy touch, joint movement

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6
Q

Give 2 examples of unencapsulated nerves

A
  • Merkel(tactile) discs

- Free nerve endings

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7
Q

What are free nerve endings involved in?

A

In epithelia; pain, heat cold

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8
Q

What are Merkel discs involved in?

A

Light touch, texture, edges, shapes

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9
Q

How are primary axons classified?

A

By conduction velocity

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10
Q

What is sensory information organised into and where?

A

Into layers in the spinal cord dorsal horn

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11
Q

What happens in the spinal cord dorsal horn?

A

Sensory information is organised into layers

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12
Q

2 tracts that information gets delivered to the brain

A
  • Medial lemniscal tracts

- Spinothalamic tracts

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13
Q

What kind of info do medial lemniscal tracts carry?

A

Mechanoreceptive and proprioceptive information to the thalamus

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14
Q

What kind of info do spinothalamic tracts carry?

A

Pain and temperature signals to the thalamus

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15
Q

What do first order neurones do?

A

Detect stimulus and transmit to spinal cord

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16
Q

What do second order neurones do?

A

Relay signals to the thalamus

17
Q

What do third order neurones do?

A

Carry the signal from the thalamus to the cortex

18
Q

Which order neurones are commissural?

19
Q

How are axons organised in the medial lemniscal system?

A

Topographically

20
Q

In the medial lemniscal system, what are the two pathways?

A

Lateral and medial pathways

21
Q

Medial lemniscal system: upper body

A
  • Follow the lateral pathway

- Synapse on 2nd order neurones in cuneate nucleus

22
Q

Medial lemniscal system: lower body

A
  • Follow the medial pathway

- Synapse on neurons in gracile nucleus

23
Q

Medial lemniscal system: What are the lateral and medial pathways together known as?

A

Dorsal column nuclei

24
Q

What happens when 2nd order neurones cross the midline and ascend in the medial lemniscus? Which order neurones reverse topology?

A

The topology is revered so that the lower body axons are more lateral
3rd order axons reverse it

25
What is a dermatome?
A region of skin innovated by a specific sensory ganglipn
26
Why do dermatomes arise?
Due to dermis of each region deriving from a specific somite
27
What is the area of cortex dedicated to each dermatome proportional to?
Density of innervation in that area, not the physical size of the area
28
All sensory fibre tracts cross the midline in the brainstem: true or false?
False, olfactory system