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Psyc323 > Week 4 Somatosensory > Flashcards

Week 4 Somatosensory Flashcards

1
Q

Touch is important to survival

A

-Body information – posture, movement, pain
-Use of objects – food, objects, tools
-Communication – conveying messages, in the way you touch someone
Proper development – body growth: Don’t develop the rest of sensory system without touch information, also don’t develop hormonally

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2
Q

Touch is a diverse modality, incorporating

A

Cutaneous sensation: Pressure - mechano, Vibration – mechano, A-beta fibres – myelinated, fast conduction, Temperature – thermo, Pain – noci
Proprioception: Body information – where it is positioned relative to itself, Are you moving?, A-alpha fibres – myelinated, fast conduction
Kinaesthesia
Pain: nociception
Itch: Pain and itch are parts touch that are qualitatively different, Different stimuli, different pathways

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3
Q

Cutaneous sensation

A 
Often what we think of when we think of touch
- Arises from any surface of the body
- Submodalities
o Pressure
o Vibration
o Temperature 
o Pain
- Stimuli
o All are physical stimuli – although pain can involve chemical stimuli as well o Mechanical compression
o Vibration
o Thermal energy transfer
o These can all be in the pain submodality if intense enough
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4
Q

Sensory system, 4 criteria

A
  1. Specialized to receive particular stimulus – i.e. has specific receptors for specific physical energy/chemical molecules
  2. Performs signal transduction (stimulus → neuronal potential)
  3. Relays the neural signal to the brain via certain pathway (synapse 1 → synapse 2 → synapse 3 …)
  4. Has its own cortical region for processing (sensory cortices + association cortices)
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5
Q

System for non-painful sensation

A

-Activate receptor – going all the way to the spinal cord using only one cell
o Signal transduction
- To spinal cord from cell body and up to brainstem – massive distance before relay
- Long neurons – axons forming peripheral nerves and cranial nerve V for the face

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6
Q

Process of touch – non-painful cutaneous sensation

A
  1. Sensory receptors are activated under the skin, this causes signal transduction in the
    sensory neuron
  2. Neural signal travels along axons (= peripheral nerve) into spinal cord.
  3. Signal travels up spinal cord and relayed to brainstem neurons – medial-lemniscal Signal relayed to interneuron, then motor neuron – exits spinal cord – reflex arc
  4. Signal relays to contralateral thalamus – medial-lemniscal
    Motor nerve activation may cause muscular response – reflex arc
  5. Signal relays to somatosensory cortex – medial-lemniscal
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7
Q

Mechanoreceptors receptive to pressure/vibration stimuli; 4 types of receptors

A

Meissners corpuscle
Merkels disk
Ruffinis corpuscle
Pacinians corpuscle

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8
Q

2 types of touch fibres

A 
Rapidly adapting (RA)
-Turn receptor on – firing stops quickly even if pressure continues
Slowly adapting (SA)
-Continually fires as long as there is pressure
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9
Q

2 types of receptive fields

A

Diffuse

  • Larger field – could push anywhere in the field and feel it Punctate
  • Smaller – only in that small circle directly to activate cell
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10
Q

Meissner corpuscles

A
  • Shallow, long axis perpendicular to skin
  • RA – punctate innervation
  • Transient stimulation – rapidly adapting
  • tells you something has touched you, not for how long
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11
Q

Merkel disks

A
  • Shallow, small, little branches
  • SA – punctate innervation
  • Steady pressure – slowly adapting
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12
Q

Ruffini endings

A
  • Deeper, long axis parallel to skin
  • SA – diffuse innervation
  • Steady pressure and stretching – slowly adapting
  • Get stretching information
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13
Q

Pacinian corpuscles

A
  • Deepest, fewest in number but most sensitive
  • RA–diffuse innervation
  • Transient stimulation for even lightest touches
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14
Q

Free nerve endings

A
  • Nociceptors and thermoreceptors here

- Feel pain and thermal information

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15
Q

Reflex arc

A
  • Within spinal cord
  • Sensory neuron – afferent information from skin
  • Interneuron
  • Motor neuron – efferent information to muscles
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16
Q

Ascending pathway

A
  • Non-painful information is relayed via medial-lemniscal pathway
  • Sensory neuron
  • 2’ neuron in brainstem – decussates at brainstem
  • 3’ neuron in thalamus
  • somatosensory cortex
17
Q

Somatosensory cortex

A

-2 major subdivisions:
S-I – receives input from thalamus: Broken into Brodmann’s 3a, 3b, 1, 2, S1 = postcentral gyrus, Output to motor cortex
o S-II – receives input from thalamus and S-I: Output to motor cortex and limbic system, Limbic for tactile learning and memory
-The judge of whether the visual info or somatosensory info is correct
-2 important features of somatosensory cortex: Somatotopic organisation, Hierarchical processing

18
Q

Somatotopic arrangement

A

-The amount of space on the somatosensory cortex devoted to each body part is proportional to the sensitivity of that part: Areas with the most afferents have the most cortical space
-Generally neighbouring regions of body map to neighbouring regions of
cortex

19
Q

Experience-dependent plasticity

A

-Topographical representation is not permanent – Somatotopic organisation is
malleable
-S1 cortical representations can change depending on amount of sensory input being received

20
Q

Somatosensory processing

A
  • Sensory information undergoes hierarchical processing (area 3- 1, 2, 5- SII)
  • At each stage more and more info is integrated
21
Q

Proprioceptive and kinaesthetic sensation

A
  • The ability to sense the position and movement of our own body: Proprioception = position of body relative to itself, Kinaesthesia = sensing movement of your joints and muscles
  • Often not what we think of when we think of touch
  • Arises from inside the body: requires a physical stimulus from the internal environment
  • Sensory info that largely goes unnoticed, yet essential to daily function: Posture, Large scale movement
22
Q

Process of touch – proprioception and kinaesthesia

A
  1. Sensory receptors are activated within the body, this causes signal transduction in
    the sensory neuron
  2. Neural signal is relayed towards the brain
  3. Cortical processing?: Brainstem- thalamus and cerebellum, Thalamus-cortex(motor cortex?), Cerebellum-online parietal cortex/cerebellum processing loop
23
Q

Three types of receptor neurons – all do signal transduction

A
  • Muscle spindles – proprioceptors: Respond to change in muscle length, High density in hand, neck, ocular muscles, In skeletal muscle
  • Golgi tendon organs: Respond to change in muscle tension, Within tendons
  • Joint receptor neurons: Respond to joint movement, At joints
24
Q

Functions of touch

A
  1. Body information
  2. Identification and use of things
  3. Communication
  4. Development
25
Q

Functions of touch: Body information

A
  • Posture
  • Locomotion
  • Limb movement
  • Internal stretch
  • Internal/external pain
  • Something touching me?
  • Parietal cortex an important site in terms of online processing of body information:ingrate somatosensory with other types of information
  • Mismatch: Rubber hand illusion, Somatoparaphrenia, Phantom limbs
26
Q

Functions of touch:Identification and use of things

A
  • Objects: identify things based on touch
  • People: Mather-infant recognition
  • Haptic technology: tactile feedback technology
  • Haptics: cutaneous sensations can arise from anywhere on surface of body
27
Q

Functions of touch: Development

A
  • Touch deprivation: one form of sensory deprivation
  • Early touch deprivation is detrimental to development
  • the more touch you have the better you seen to grow and act
28
Q

Functions of touch: Communication

A
  • Semantic communication: braille
  • Social communication: touch + vision combo= earliest form of communication from infancy, important component of interpersonal relationships throughout life
  • whats in a handshake: salutation, show of friendship
29
Q

Detection and identification

A
  • Detection: need to be able to produce quantifiable stimuli, mechanical compression, vibration, thermal energy
  • Identification: what do you feel and where?, pain or vibration or what
30
Q

Detection and identification of cutaneous sensation can be influenced by:

A

-Adaptation: Can feel jewellery when you first put it on and then are not aware of it, Reduction in detection even though the receptors are being activated
-Area of body: Density – threshold when receptors are highly dense, Sensitive areas – glabrous – non hairy areas of skin, lips/ fingers > back/stomach
-Age: Things get worse as we age, skin is no different, Skin gets slack – lose pliability, lose sensitivity in touch
-Sex: Females > males, Not genetic but due to what males and females stereotypically do, Nurture, Males have calloused hands – epidermis later gets thicker and
increases distance between receptors and what is touching you
-Temperature: Exposed to cold – pliability decreases – skin gets harder and is difficult
to deflect and push into it, Hands don’t work as well – less sensitivity
-Practice: Do anything needing fine sensory tactile input – threshold will be
lower, Number of receptors is stable but get more cortical space dedicated to
the area of body being used

Psyc323 (10 decks)

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