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Reuben's Neuroscience > Neurophysiology > Flashcards

Neurophysiology Flashcards

1
Q

What are the 3 important types of somatosensation?

A
  1. Mechanoreception (touch)
  2. Proprioception
  3. Thermal sensation
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2
Q

At which locations are the higher concentrations of mechanoreceptors located?

A

Glabrous/non-hairy skin including the lips, fingers and palm, toes and sole, and much of the face

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3
Q

What are the four kinds of mechanoreceptors in glabrous skin? (List in order of superficial to deep)

A
  1. Meissner corpuscles
  2. Merkel complexes
  3. Ruffini organs
  4. Pacinian corpuscles
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4
Q

Which of the glabrous skin mechanoreceptors are complex and which are simple?

A

Simple - Merkel, Ruffini

Complex - Meissner, Pacinian

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5
Q

What do mechanoreceptors sense specifically?

A

Forces that distort the skin

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6
Q

What are ‘receptors’ in terms of mechanoreception?

A

Receptors, as opposed to pharmacology where they would be considered the molecular structures, are instead complex extracellular structures that surround the nerve ending of an axon

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7
Q

How is mechanoreception initiated?

A

Mechanoreception is initiated by the physical opening of Na+ channels due to exogenous forces being applied to the receptor region

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8
Q

How is the sensitivity of mechanoreceptors decided?

A

By the amount the Na+ are linked by protein intracellularly as well as extracellularly

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9
Q

Which glabrous skin mechanoreceptors are slowly-adapting and which are rapidly-adapting?

A

Slowly-adapting: Merkel, Ruffini

Rapidly-adapting: Meissner, Pacinian

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10
Q

Which way do mechanoreceptor nerves transmit?

A

Dorsally to a cell body in the DRG and then into the dorsal horn

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11
Q

What is a key difference between mechanoreceptors and nociceptors?

A

Nociceptors only respond to very strong stimuli c.f. mechanoreceptors and proprioception which respond to low basal sorts of energies, so one could say that nociceptors tell us about internal problems and damage whereas mechanoreceptors tell us about the outside world

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12
Q

What information do slowly-adapting and rapidly-adapting mechanoceptors encode?

A

Slowly-adapting: length of time stimulus is applied

Rapidly-adapting: onset/offset/changes of stimulus

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13
Q

Which of the 4 glabrous skin receptor types is the most common?

A

Meissner cells

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14
Q

What size of receptive fields do the 4 types of the glabrous skin mechanoreceptor have?

A

Meissner, Merkel cells - small

Ruffini, Pacinian - large

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15
Q

What do each of the 4 types of glabrous skin mechanoreceptor encode?

A
  • Miessner encode rate of force
  • Merkel encode grip force
  • Pacinian encode vibrations
  • Ruffini encode hand posture
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16
Q

What axon type do mechanoreceptor nerves have?

A

Aβ axons

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17
Q

What test confers information about sensitivity of areas of skin?

A

Two-point discrimination
This uses two probes and asks the participant (without visual cues) to say whether they can feel two probes or one in certain areas of skin

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18
Q

Where do mechanoreceptor nerves extend to?

A

From high in the CNS (the medulla of the brainstem) to the cell body in the DRG of the periphery and all the way out to the sensory organ

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19
Q

Where do mechanoreceptor nerves decussate and how does this differ from pain and temperature fibres?

A

The decussation for mechanoreceptors happens just after the synapse in the medulla of the brainstem. This differs from pain and temperature fibres as they decussate at the same spinal nerve level.

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20
Q

How are nerves organised in the dorsal posterior column going from inferior to superior?

A

Lower somatosensory nerves are situated closer to the midline and higher somatosensory nerves layer further away from the midline.

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21
Q

What is the name of the medial dorsal column nuclei that has input from the legs?

A

Gracile

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22
Q

What is the name of the lateral dorsal column nuclei that has input from the arms?

A

Cuneate

23
Q

What is the name of the somatosensory pathway made out of an arc of flat fibres that passes from the brainstem?

A

Medial lemniscus pathway

24
Q

Where is the 2nd synapse (3rd nerve origin) of the somatosensory pathway and where does it pass?

A

It starts in the thalamus (at the ventral posterolateral/posterior nucleus/ventral basal nucleus) and heads into the cortex to the postcentral gyrus (posterior to the central sulcus)

25
Q

Where is the somatosensory cortex?

A

In a band posterior to the central sulcus (and thereby posterior to the primary motor cortex)

26
Q

T/F: The posterior parietal cortex also conveys somatosensory information.

A

True

27
Q

How many regions are there within the postcentral gyrus/somatosensory cortex?

A

Four (4).

28
Q

T/F: Neural ‘real estate’ is inversely proportional to sensitivity of organ.

A

False. Neural ‘real estate’ tends to follow a more proportional relationship with the sensitivity of the organ.

29
Q

How many somatotopic maps are in S1 (primary somatosensory cortex), S2 (secondary somatosensory cortex) and the posterior parietal cortex?

A

4, 4, 2 respectively

30
Q

T/F: There is overlap of sensation in the periphery, but modularity of sensation in S1 (the primary somatosensory cortex).

A

True.

31
Q

What is the most important region of the primary somatosensory cortex?

A

3b

32
Q

What brain regions contribute to recollection of somatosensory stimuli?

A

The amygdala and hippocampus

33
Q

What is the probable role of the posterior parietal cortex?

A

Contextualise information

34
Q

What does the existence of variable modules imply about the brain?

A

Neural plasticity in the contexts of development and injury

35
Q

In brain/neural injury, where does the neural compensation occur?

A

At all levels of innervation

36
Q

T/F: Nerve regeneration can occur in both the CNS and the PNS.

A

False. Nerve regeneration only occurs in the PNS.

37
Q

Define anaesthesia.

A

No sensation at all.

38
Q

Define hypoaesthesia.

A

Less sensation than normal.

39
Q

Define hyperaesthesia.

A

More sensation than normal.

40
Q

Define dysaesthesia.

A

A different sensation e.g. tingling.

41
Q

Define hyperpathia.

A

An exaggerated response to a painful stimulus.

42
Q

What is a phantom limb?

A

The impression of part of the body that remains after amputation

43
Q

What orientations can a phantom limb be felt in?

A

normal motion, immobilisation, odd orientations

44
Q

T/F: Phantom limbs can cause pain.

A

True

45
Q

Where does the spinal cord end and therefore where is a ‘safe’ site of lumbar puncture?

A

L1/L2 and therefore it is safe to performa lumbar puncture at L3/L4.

46
Q

More distally (caudally) down the body, how are the somatic/motor neurons placed in the ventral horn of the spinal cord?

A

For somatic/motor control the more distal (caudal), the more lateral the spinal cord segments are placed.

47
Q

T/F: In the spinal cord, the more rostral, the more white matter there is.

A

True

48
Q

Where are ventral horns largest?

A

Where there are limbs to innervate.

49
Q

What nerve segments is the lower limb plexus made of?

A

L4 - S3

50
Q

What type of fibre is a pain fibre (as well as temperature and itch)? Describe them.

A

C fibres. Small diameter. Slow transmission speed. Unmyelinated. Free nerve endings.

51
Q

What type of fibre is also a pain fibre but also detects temperature alone (and not itch)? Describe them.

A

Aδ fibres. Free nerve endings. Reasonably small. Reasonable transmission speed (not as large or fast as touch). Reasonable about of myelination.

52
Q

What is the pathway of pain and temperature called?

A

The spinal thalamic pathway/anterolateral system formed by 2nd order neurons that synapse with Aδ and C fibres in the dorsal horn and decussate at the same level of the spinal cord. These 2nd order neurons ascend anterolaterally as the second name suggests.

53
Q

Where do the α motor neurons descend in the spinal cord?

A

At the ventral root

Reuben's Neuroscience (10 decks)

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