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Neuroscience > Somatosensation I > Flashcards

Somatosensation I Flashcards

1
Q

What are the 5 functions of the somatosensory pathway?

A

→ Conveying sensation from the body
→ touch

→ proprioception ( sense of body position)
→ Heat and cold
→ pain and itch

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2
Q

How many pairs of spinal nerves do we have?

A

→ 31 pairs

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3
Q

How is the CNS connected to the body?

A

→ Spinal and cranial nerves

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4
Q

What is a nerve?

A

→ a bunch of fascicles

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5
Q

What do fascicles consist of?

A

→ Individual myelinated axons

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6
Q

What is the membrane of the fasciles called?

A

→ perineurium

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7
Q

What is the membrane of the spinal nerve called?

A

→ Epineurium

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8
Q

What is the membrane of each individual axon called?

A

→ Endoneurium

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9
Q

What do the 8 spinal nerves and the top of the thoracic nerves form?

A

→ Brachial plexus

→ Cervical plexus

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10
Q

What is the function of spinal nerves?

A

→ Carry information between the CNS and the periphery

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11
Q

How many pairs of nerves does the cervical region contain?

A

→ 8

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12
Q

What do the dorsal roots contain?

A

→ Sensory afferents

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13
Q

What do the ventral roots contain?

A

→ Motor efferents (somatic)

→ Autonomic effererents

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14
Q

What do dorsal and ventral roots unite to form?

A

→ Spinal nerve

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15
Q

What does white matter contain?

A

→ Ascending and descending axon tracts

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16
Q

What does grey matter contain?

A

→ Cell bodies
→ Dendrites

→ Synapses

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17
Q

Where do the spinal nerves pass through?

A

→ Intervertebral foramina

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18
Q

What do dorsal root ganglia contain?

A

→ All the cell bodies of all the sensory neurons of the somatosensory system

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19
Q

What do large fibres sense?

A

→ tactile and proprioceptive

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20
Q

What do small fibres sense?

A

→ Temperature
→ pain

→ itch
→ crude touch

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21
Q

What are dorsal root ganglia neurons called and why?

A

→ pseudo unipolar neurons
→ they have a single process

→ gives rise to an axon in both directions

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22
Q

What kind of adaptation does a Merkel disc have?

A

→ Slow adapting

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23
Q

How many large fibre afferents are there in the skin?

A

→ 4

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24
Q

What kind of touch are Merkels discs sensitive to?

A

→ Light touch and pressure

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25
Q

Where are Meissners corpuscles and Merkels discs located?

A

→ between the dermis and the epidermis

26
Q

What happens to a Merkels disc if a stimulus is applied and maintained?

A

→ Action potentials fire

→if the stimulus is maintained then the action potentials continue to fire

27
Q

What happens to a Meissners corpuscle if a stimulus is applied and maintained?

A

→ action potentials fire

→ if the stimulus is maintained the action potentials drop to 0

28
Q

What are the cutaneous tactile afferents?

A

→ Meissners corpuscles

→ Merkels discs

29
Q

What are the deep tactile afferents?

A

→ Ruffini

→ Pacinian

30
Q

What type of fibre are tactile afferents?

A

→ A beta

large diameter, myelinated, 2nd fastest conducting

31
Q

What do Pacinian corpuscles respond to?

A

→ Vibration

32
Q

What do Ruffini corpuscles respond to?

A

→ Slipping

→ Non slipping

33
Q

What are fast adapting afferents?

A

→ Meissner

→ Pacinian

34
Q

What are slow adapting afferents?

A

→ Ruffini

→ Merkel

35
Q

What do muscle spindles detect?

A

→ Changes in muscle length

36
Q

What fibres detect change in length in muscles?

A

→ Large fibre systems

→A-alpha afferents

37
Q

What senses muscle tension?

A

→ Golgi tendon organs

38
Q

What is muscle length a cue for?

A

→ Proprioception

39
Q

What type of neuron is a normal motor neuron?

A

→ Alpha

40
Q

What are A delta fibres like?

A

→ thin

→ myelinated

41
Q

What are C fibres like?

A

→ Thin

→ unmyelinated

42
Q

What does a small receptive field mean?

A

→ THe stimulus is localised

43
Q

What are the two major somatosensory pathways?

A

→ Dorsal column - medial lemniscal system

→ Spinothalamic tract

44
Q

What does the dorsal column sense?

A

→ Mediates discriminative touch
→ vibration
→Inputs from A-β and A-α afferent fibres

→ proprioception

45
Q

What does the spinothalamic tract sense?

A

→ Coarse touch
→ temperature
→coarse touch, temperature, pain
Inputs from A-δ and C fibres

→ pain

46
Q

Describe the pathway from a tactile afferent in the upper body to the somatosensory cortex

A

→ Stimulus from the Merkel, Ruffini, Pacinian or Meissners occurs
→ The stimulus travels via 1st order neurons to the dorsal column (cuneatus)

→ the 1st order neuron travels up to the medulla (nucleus cuneatus) where it synapses with a 2nd order neuron
→ the 2nd order neuron decussates at the midline
axons from cells of the dorsal column nuclei arch toward the ventral and medial medulla, and decussate
→ the 2nd order neuron travels up the medial lemniscal tract of the brainstem to the VPL thalamus
→ 2nd order neuron synapses at the VP thalamus with a 3rd order neuron which carries it to the somatosensory cortex

47
Q

What is the difference between the Cuneate and Gracile dorsal column?

A

→ Cuneate - upper body

→ Gracile - lower body

48
Q

What inputs come to the ventral posterior medial nucleus?

A

→ Sensory inputs of the head and face

49
Q

What inputs come to the ventral posterior lateral nucleus?

A

→ Sensory inputs from the body

50
Q

Where is the somatosensory cortex?

A

→ Front of the parietal lobe

51
Q

What are A-beta afferents?

A

large diameter, myelinated,

→2nd fastest conducting

52
Q

Where are small receptive fields found?

A

→ tips of fingers

53
Q

Describe the pathway from a tactile afferent in the upper body to the somatosensory cortex in the face

A

→ large diameter mechanosensory receptors from face picked by trigeminal ganglion
→ synapses onto the principal ipsilateral nucleus of trigeminal complex
→the 2nd order neuron decussates at the midline
→ the 2nd order neuron travels up the medial lemniscal tract of the brainstem to the VP thalamus
→relayed to somatosensory cortex

54
Q

What is one difference between VPL and VPM?

A

→VPM- face

→VPL sensory info from the body

55
Q

What are areas 1, 2,3 in the postcentral gyrus?

A

→ primary somatosensory cortex

56
Q

What is area 4 in the central sulcus?

A

motor cortex

57
Q

How are regional cortical differences identified?

A

→ relative thickness
→ cell size
→density

58
Q

How are somatotopic maps duplicated?

A

duplicates 4 times each in the Browman’s area

59
Q

Where does secondary somatosensory info go to?

A

→ to amygdala and hippocampus

60
Q

Where does parietal somatosensory info go?

A

→ to motor and premotor cortical areas

61
Q

What is the only sensory information which does not first synapse in the thalamus?

A

olfactory

62
Q

What is the difference between muscle spindle and Golgi tendon organ?

A

The function of the GTO can be considered opposite of the muscle spindle, which serves to produce muscle contraction.
When a GTO is stimulated, it causes its associated muscle to relax by interrupting its contraction.​

Neuroscience (21 decks)

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