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PHYL2064 > Somatosensory L5: Systems > Flashcards

Somatosensory L5: Systems Flashcards

1
Q

What are Somatosensory receptor organs?

A

Muscles, tendons, skin.

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2
Q

______ are most primary sensory neurons (often branched) – exception: Merkel’s disk in the skin

A

Receptors

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3
Q

There are several modalities (and submodalities), each with their own specific _____(ascending/descending) pathway

A

ascending

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4
Q

What is touch?

A

touch, pressure, low and high frequency vibration

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5
Q

What is proprioception?

A

position/movement

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6
Q

What is thermoreception?

A

warm/hot or cold/cool

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7
Q

What is pain?

A

sharp cutting; dull burning; deep aching, temperature

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8
Q

What are 3 features of non-encapsulated touch for cutaneous receptor types?

A
  1. Hair follicle receptor
  2. Merkel’s disk
  3. Free nerve ending.
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9
Q

What are 3 features of encapsulated touch for cutaneous receptor types?

A
  1. Meissner corpuscles
  2. Pacinian corpuscles
  3. Ruffini corpuscles.
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10
Q

What are encapsulated touch- cutaneous receptor types?

A

cutaneous tissue and nerve ending encapsulated in thin sheath

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11
Q

What are hair receptors, Merkel’s disc, Pacinian corpuscle, Ruffini endings and Meissner’s corpuscle?

A
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12
Q

_____ neuron endings spiral around the base of hair follicles

A

Afferent

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13
Q

What is the stimulus for hair receptors?

A

mechanical displacement of the hair leads to receptor potential

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14
Q

What are fast adapting receptors?

A

phasic

Sustained stimulation does not produce further action potentials

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15
Q

How can hair receptors respond?

A

Respond best to moving objects and signal the direction and speed of the moving object: Discriminative touch.

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16
Q

What are tonic receptors?

A

Stay activated until stimulus goes Eg. nociceptive

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17
Q

What are phasic receptors?

A

Eg. glasses on face

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18
Q

Where is the Merkel cell-neurite complex found?

A

Found in hairy and not hairy skin in basal layer of the epidermis

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19
Q

What are 2 receptor types in the Merkel cell-neurite complex?

A

Merkel cell and Merkel disk

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20
Q

What is the specialised receptor cells?

A

Merkel cell

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21
Q

What forms the Merkel disk in Merkel cell-neurite complex?

A

Enlarged afferent neuron endings form Merkel disk

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22
Q

How does Merkel cell-neurite complex respond?

A

Respond to fine tactile stimuli (pressure) and slow vibration (5-15 Hz)

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23
Q

What is the force for Merkel cell-neurite complex?

A

Force applied to skin leads to distortion of the cell receptor potential = neurotransmitter release (glutamate?) in Merkel cell leads to action potential in Merkel disk.

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24
Q

In Merkel cell-neurite complex, each afferent neuron innervated up to 90 _____ cells in a discrete patch of skin

A

Merkel

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25
Q

_____(Large/small) receptive fields in fingers, _____(large/small) in palm of hand and legs

A

Small; larger

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26
Q

Is the Markel cell-neurite complex fast or slow adapting?

A

Slow adapting

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27
Q

What do Merkel cell neurite complex respond best to?

A

Responds best to steady pressure from small objects.

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28
Q

Where is the Meissner corpuscle found?

A

Encapsulated receptor found within the dermal papillae in non-hairy skin

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29
Q

What is the Meissner corpuscle most sensitive to?

A

Most sensitive to flutter (low frequency vibrations 30-50 Hz) and movement

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30
Q

What is Meissner corpuslcle?

A

Stack of epithelial cells with afferent fibre endings interspersed between the cells.

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31
Q

What is the force for Meissner corpuscle?

A

Force applied to skin causes epithelia cells to slide past each other = distortion of membranes of axon terminals = receptor potential

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32
Q

What forms the Meissner corpuscle?

A

Single afferent neuron forms many Meissner corpuscles

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33
Q

Is Meissner corpuscle fast or slow adapting?

A

Rapidly adapting response

34
Q

Is Meissner corpuscle have ____ (small/large) receptive fields

A

small

35
Q

How does Meissner corpuscle respond best?

A

Respond best to rubbing against skin, movement across a surface

36
Q

What are Ruffini corpuscle?

A

Encapsulated mechanoreceptor

37
Q

What is Ruffini corpuscle sensitive to?

A

Sensitive to skin stretch (15-400 Hz), sustained pressure

38
Q

Where are Ruffini corpuscle found?

A

Found deep in the skin, in joint ligaments and capsules (touch and proprioceptor)

39
Q

What does Ruffini corpuscle contain?

A

Contains strands of collagenous fibres, continuous with connective tissue

40
Q

In Ruffini corpuscle, afferent fibre branches within the capsule, endings are intertwined with ______ fibres

A

collagenous

41
Q

What is detected in the dermis of Ruffini corpuscle?

A

Tugging or stretching in the dermis detected

42
Q

Are Ruffini corpuscle fast or slow adapting receptors?

A

Slowly adapting receptor

43
Q

What does Ruffini monitor?

A

Monitor slippage of object (modulation of grip).

44
Q

What are encapsulated in for Pacinian corpuscle?

A

Encapsulated (onion shaped with layers of epithelial cells surrounding afferent neuron endings)

45
Q

What are Pacinian corpuscle sensitive to?

A

Sensitive to vibratory pressure (100-300 Hz), deep touch

46
Q

In Pacinian corpuscle, in subcutaneous tissue beneath the dermis, connective tissues of bone, body wall and body cavity = cutaneous and _____ function

A

proprioceptive

47
Q

In Pacinian corpuscle, Epithelial cells contain fluid that is displaced when force is applied, movement of fluid ____ force

A

dissipates

48
Q

What is a mechanical deformation for Pacinian corpuscle?

A

opening of pressure sensitive channel = receptor potential

49
Q

Is Pacinian corpuscle fast or slow adapting receptors?

A

Fast adapting

50
Q

What is the function of Pacinian corpuscle?

A

grasping releasing objects, surface texture discrimination

51
Q

What are 5 characteristics of free nerve ending?

A
  1. Found throughout the body (skin, muscles, tendons, cornea, viscera, etc.)
  2. Receptors for crude touch, pain and temperature
  3. Morphologically very similar but different functions, each with its own ascending pathway
  4. Adaptation depends specific functional type, but mostly slow adapting
    • Some can be fast adapting
  5. Small unmyelinated fibre- s- Slower transmission
52
Q

What are 5 characteristics of properioception?

A
  1. Essential for maintaining balance and posture
  2. Stimuli: internal forces generated by certain position or movement of a limb/body part
  3. Receptors are in muscles, tendons, joint ligaments and capsules
  4. Skeletal muscles: muscle spindles and Golgi tendon organs, free nerve ending
  5. Joints: encapsulated endings similar to those in the skin, free nerve endings.
53
Q

What are 6 characteristic of muscle spindles?

A
  1. Sensitive to muscle stretch (length) – they signal rate of change
  2. Most numerous in muscles responsible for fine movement (e.g. hand, eyes)
  3. Encapsulated (contain small muscle fibres, afferent and efferent nerve terminals
  4. Small muscles fibres in capsule attach to large fibres of the muscles, capsule is oriented in parallel to muscle fibres
  5. Two types of afferent endings at center and polar ends of the muscles spindle
  6. When the muscle is stretched, mechanically gated ion channels open = receptor potential.
54
Q

What are 6 characteristics of Golgi Tendon Organs?

A
  1. Sensitive to muscle contractions against a force (muscle tension)
  2. Similar to Ruffini corpuscles
  3. Encapsulated, intertwining collagen bundles, continuous with muscle tendon, afferent nerve endings are interspersed with collagen
  4. Found in tendons of striated muscles near muscle-tendon junction = in series with muscle fibres in one end and muscle tendon on the other end
  5. When muscle contract, terminals are compressed until muscle relaxes again
  6. Slowly adapting response.
55
Q

What are 5 characteristics of thermoreception?

A
  1. Cold receptors respond to decreases in skin temperature (5- 43˚C)
    • More or less = becomes painful = some damage
  2. Hot receptors respond to increases in skin temperature (maximum at 45˚C)
  3. When temperature of skin is 36 ˚C then both receptors respond minimally = neutral thermal region
  4. Cold afferent fibres are myelinated and faster than unmyelinated warm afferent fibres = decreases in temperatures are detected faster than increases- Winter = colder = more activation of cold receptors
  5. Fast adapting (respond best to changes).
56
Q

What are 4 characteristics of pain?

A
  1. Primarily a protective mechanism to bring awareness that tissue damage is occurring
  2. Begins with stimulation of nociceptors
  3. Sensation of pain is accompanied by behavioural responses (e.g. withdrawal) and emotional reactions- Sometimes can reach the brain but not the conscious part
  4. Subjective perception can be influenced by other past or present experiences.
57
Q

What are 3 categories of pain receptors?

A
  1. Mechanical
    • Eg. touching
  2. Thermal
    • Eg. burning
  3. Polymodal (chemicals, e.g. capsaicin- Eg. spicy food ).
58
Q

Pain signals are transmitted over two _____ pathways

A

afferent

59
Q

What is the Substance P Pain Pathway?

A
60
Q

What are analgesic pathway?

A
61
Q

What are 5 characteristics of somatosensory pathways- peripheral axons?

A
  1. Morphology of peripheral axons varies with type of receptor it forms/innervates
  2. Myelination as well as diameter determines the conduction velocity
  3. Thick myelinated fibres (fast: 70-170 m/s) carry proprioceptive information
  4. Medium myelinated fibres (5-70 m/s) carry information from the mechanoreceptor in the skin as well as pain and temperature information
  5. Thin unmyelinated fibres (slow 0.5-2 m/s) carry information about temperature, pain and itch.
62
Q

What do thick myelinated fibres carry?

A

(fast: 70-170 m/s) carry proprioceptive information

63
Q

What do medium myelinated fibres carry?

A

(5-70 m/s) carry information from the mechanoreceptor in the skin as well as pain and temperature information

64
Q

What do thin unmyelinated fibres carry?

A

(slow 0.5-2 m/s) carry information about temperature, pain and itch

65
Q

What are the 4 general principles for somatosensory?

A
  1. Primary afferent fibre synapses with secondary neuron(s) in spinal cord or brain stem- interneurone
  2. In each pathway the fibres cross over to opposite side of the spinal cord or brain stem before reaching the thalamus = contralateral cortex receives information
  3. From the thalamus, neurons project into the somatosensory area of the cortex
  4. Somatotopic organisation of the somatosensory cortex.
66
Q

What does the sensory homunculus look like?

A
67
Q

What are 7 features of phantom limbs/pain?

A
  1. Sensation that amputated limb is still there
  2. Can also occur in people born without limbs
  3. Sensation such as hot/cold, itchiness and pain can be felt in the absent/amputated limb
  4. Long thought to be a psychological problem but now recognised as spinal cord/brain problem
  5. MRI studies show activity in the areas of the brain that receive input from the missing limb when phantom pain is felt
  6. Rewiring problem? Memory of pain problem?
  7. Treatment : mirror
68
Q

What is phantom limb pain?

A

Sensation that amputated limb is still there Long thought to be a psychological problem but now recognised as spinal cord/brain problem

69
Q

When can phantom limb pain occur?

A

Can also occur in people born without limbs

70
Q

What sensations can be felt in phantom limb pain?

A

Sensation such as hot/cold, itchiness and pain can be felt in the absent/amputated limb

71
Q

What does an MRI show in phantom limb pain?

A

MRI studies show activity in the areas of the brain that receive input from the missing limb when phantom pain is felt

Rewiring problem? Memory of pain problem?

72
Q

What is the treatment of phantom limb pain?

A

mirror

73
Q

What are 6 characteristics of Alien hand syndrome?

A
  1. Seen in patients treated for extreme epilepsy (sectioned corpus callosum) and also patients with degenerative brain diseases or stroke
  2. Several subtypes depending on which part of the brain is affected
  3. Hand appears to have a mind of its own
  4. Patients report that they cannot control the hand
  5. Various theories about mechanisms
  6. Treatment – no cure; keeping the hand occupied by giving it something to hold, or holding the hand seems to help.
74
Q

When are Alien hand syndrome seen?

A

Seen in patients treated for extreme epilepsy (sectioned corpus callosum) and also patients with degenerative brain diseases or stroke

75
Q

What is Alien hand syndrome?

A
  1. Several subtypes depending on which part of the brain is affected
  2. Hand appears to have a mind of its own
  3. Patients report that they cannot control the hand
76
Q

What is the treatment of Alien hand syndrome?

A

no cure; keeping the hand occupied by giving it something to hold, or holding the hand seems to help.

77
Q

What are 5 characteristics of Body integrity identity disorder (BIID)?

A
  1. Feeling that the leg (often the left leg) does not belong
  2. Sufferers want to have the limb amputated even though it is physically healthy
  3. Condition often leads to depression, self-mutilation
  4. Long thought to be a psychological disorder
  5. Evidence is emerging that the problem lies in the somatosensory area of the parietal lobe – representation of leg is missing.
78
Q

What is Body integrity identity disorder (BIID)?

A
  • Feeling that the leg (often the left leg) does not belong
  • Sufferers want to have the limb amputated even though it is physically healthy;
79
Q

What does the Body integrity identity disorder (BIID) lead to?

A
  • Condition often leads to depression, self-mutilation
  • Long thought to be a psychological disorder
    • Due to homunculus –> childhood..etc
80
Q

What does evidence say about the problem with Body integrity identity disorder (BIID)?

A

Evidence is emerging that the problem lies in the somatosensory area of the parietal lobe – representation of leg is missing.

PHYL2064 (29 decks)

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