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Behavioral Neuroscience > Final Exam - Somatosensory > Flashcards

Final Exam - Somatosensory Flashcards

To know each and every slide to ACE the final!!

1
Q

What are the four major divisions of the somatosensory system?

A
  1. Discriminative touch (what am I touching)
  2. Proprioception (understanding of where limbs are positioned in space)
  3. Nociception (pain)
  4. Temperature sense (thermal sense)
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2
Q

The dorsal root ganglion conveys information to where?

A

CNS

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3
Q

Sensory receptors can be what two things?

A
  1. Specialized

2. Bare nerve endings

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4
Q

What are the two classes of sensation?

A
  1. Epicritic

2. Protopathic

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5
Q

What is epicritic?

A

A class of sensation that has small receptive fields, dense on fingertips and face.

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6
Q

What is the function of encapsulated receptors (4 functions)?

A

Classified under Epicritic sensation

  1. Involved in fine discriminations, where something is happening, and what is happening.
  2. Topognosis: localize gentle touch.
  3. Identify vibration.
  4. Two-point discrimination
  5. Stereognosis: identify objects by shape (without looking, feeling only)
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7
Q

What do protopathic sensations consist of?

A

Bare nerve endings

  1. Pain
  2. Temperature
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8
Q

What is the somatosensory pathway?

A

Peripheral target (skin) -> dorsal root ganglion cell -> CNS

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9
Q

What are dermal receptors?

A

Small receptive fields packed very densely close to the surface of the skin.

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10
Q

What is the Meissner’s Corpuscle?

A

A dermal receptor:

  1. Rapidly adapting: increases firing rate transiently when stimulus is started and turned off (finger touch table/taking off = change in baseline)
  2. Detect rapid shape change, such as edges
  3. Larger receptive field than Merkel Disk
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11
Q

What is the Merkel Disk?

A

A dermal receptor:

  1. Slow adapting: keeps reporting change from baseline, always elevated until stimulus is off
  2. Detects compression
  3. Sensitive to contours of object and spatial patterns
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12
Q

What are subcutaneous receptors?

A

Large receptive fields located deeper than the dermal receptors: the smooth skin (palm)

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13
Q

What is the Pacinian Corpuscle?

A

A subcutaneous receptor:

  1. Rapidly adapting
  2. Rapid indentation of skin
  3. Vibration sensitive: movement of skin
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14
Q

What is the Ruffini Ending?

A

A subcutaneous receptor:

  1. Slow adapting
  2. Stretching of skin or bending of fingernails
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15
Q

What are involved with the receptors of hairy skin?

A

Back of skin

  1. Hair follicle receptors: Sense displacement of hair
  2. Field receptors: detect stretch of skin as joints are flexed.
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16
Q

What is the vibration sensitivity of the Merkel Disk?

A

5 - 15 Hz

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17
Q

What is the vibration sensitivity of Meissner’s Corpuscles?

A

20 - 50 Hz

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18
Q

What is the vibration sensitivity of the Pacinian Corpuscles?

A

60 - 400 Hz

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19
Q

Where are humans maximally sensitive at (vibration)?

A

200 - 250 Hz

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20
Q

Receptor distribution between SA I (Merkel) and RA (Meissner’s)?

A

RA (Meissner’s) more dense (more receptive fields)

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21
Q

Receptor distribution between SA II (Ruffini) and PC (Pacinian)?

A

SA II (Ruffini) more dense in fingers and palm, but PC (Pacinian) more dense in finger tips.

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22
Q

How are spatial characteristics of Objects measured?

A
  1. Size and shape encoded by receptors stimulated.
  2. Texture information
  3. Merkel Disks: best spatial resolution
  4. Meissner’s Corpuscles: Identify individual dots in pattern
  5. Pacinian Corpuscles: Monitors speed at which finger moves over surface
23
Q

How is the body sensitive to temperature?

A
  1. Cold, cool, warm, hot
  2. Monitor difference between object and skin temperature (what is the temp of object in comparison to skin)
  3. Deviate from slow base firing rate as temperature deviates from 34 degree C.
24
Q

Which temperatures are interpreted as pain?

A

Above 50 degrees C and below 5 degrees C.

25
Q

What are nociceptors?

A

Detect and transmit pain sensation

26
Q

What transmitters are used for nociceptors?

A

Transmitters include histamine, K+, bradykinin, Substance P, NGF

27
Q

What are the three classes of nociceptors?

A
  1. Mechanical
  2. Thermal
  3. Polymodal (destructive effects of stimulus, not physical properties - chemical burn, etc)
28
Q

What does NGF do?

A

A transmitter that regulates pain sensation. By blocking NGF, you can block some chronic pain.

29
Q

Is a nociceptor the same as tactile receptors?

A

No, tactile receptors do not encode for pain, touch only.

30
Q

What is proprioception?

A

Another class of receptors:

  1. Stationary limb position
  2. Limb movement
  3. Muscle spindle cells, Golgi tendon organs, joint capsule receptors (all of these provide feedback such as muscle contraction, load, and joint)
31
Q

What is visceral sensation?

A

Another class of receptors:

  1. Mechanoreceptors: overeating (stomach expands -> receptors tells body to stop eating by detecting stretch, pressure, and anything else that is transduced through mechanical stimulation)
  2. Chemoreceptors: detects O2 concentration, pH of blood, etc.
32
Q

How do shingles arise?

A

Result of chicken pox virus that live in nerve roots. Usually affects a single dermatome.

33
Q

What are dermatomes?

A

An area of skin that is mainly supplied by a single spinal nerve. Each nerve relays sensation from a particular region of the skin to the brain.

34
Q

What is the purpose of the somatosensory cortex?

A

Integrates information to generate overall impression of object.

35
Q

What is the S I region?

A

Part of somatosensory cortex:

  1. Postcentral gyrus
  2. BA 3b and 1: information from skin (tactile)
  3. BA 3a and 2: proprioceptive information (limb position in space)
36
Q

What is S II region?

A

Part of somatosensory cortex:
1. Superior bank of lateral fissure -> insula
(Activated in response to light touch, pain, visceral sensation, and tactile attention)

37
Q

What BA’s consist of the posterior parietal cortex ?

A

BA 5 and 7 (part of somatosensory cortex)

38
Q

Describe receptive fields

A
  1. Larger in cortex than for dorsal root ganglion neurons (bigger as you get higher up)
  2. Modifiable by experience (sensory feedback through learning increases or decreases receptive fields)
  3. Formed during development (retasking, rededication of brain tissue as we go through life)
39
Q

Describe the increasing receptive fields through BA.

A 
BA 3b = one fingertip 
BA 1 = four fingertips
BA 2 = four fingers
BA 5 = both hands (8 fingers)
(Increasing cortical recording site = larger receptive field)
40
Q

Somatosensory cortex layers II and III project to what?

A

To areas 1 and 2, S II cortex

41
Q

Somatosensory cortex layer IV gets info from where?

A

Thalamus

42
Q

Somatosensory cortex layer V projects to what?

A

Basal ganglia, brain stem, and spinal cord

43
Q

Somatosensory cortex layer VI projects to what?

A

Thalamus

44
Q

Explain somatotopic organization.

A

BA 3b and 1 = a two homunculus system in which both presents a way to localize touch stimuli in the brain.

45
Q

Explain the types of dorsal column receptive fields.

A
  1. Convergent excitation: no inhibition of receptor neurons
  2. Surround inhibition: receiving strong excitation and inhibition
  3. Lateral inhibition: Active neurons inhibit adjacent neurons.
46
Q

What does lateral inhibition do for two-point discrimination?

A

Improves tactile perception for two-point stimuli.

47
Q

What does BA 2 detect?

A

Feature detection:

  1. Orientation-sensitive neuron: different orientations = different nerve firing
  2. Direction-sensitive neuron: Neurons fire rapidly depending on direction of stimulus across the hand.
48
Q

What produces direction sensitivity in BA 2?

A

Convergence of relay neurons.

49
Q

What are BA 3b and 1 responsive to?

A

Touch

50
Q

What is BA 3a responsive to?

A

Position

51
Q

What does BA 2 do?

A

Combines touch and position

52
Q

What does BA 5 receive?

A

Joint information to encode information about posture (proprioceptive system: where limbs are in space)

53
Q

What does BA 7 do?

A

Takes output form BA 5:

  1. Integrates visual and tactile stimuli
  2. Important for eye-hand coordination

Behavioral Neuroscience (9 decks)

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