Chapter 12: Somatosensory

Question 1

What are the sensory sunmidalities in the skin?

Answer 1

Mechanoreceptors: touch, vibration, pressure

Thermoreceptors: temperature

Nociceptors: pain

Question 2

What are Mechanoreceptors in the skin sensitive to?

Answer 2

Bending, stretching, vibration, pressure

Question 3

What are the specialized nerve endings in the skin?

Answer 3

Merkel’s Disk, Meissner’s corpuscule, Pacinian Corpuscule, Ruffini ending

Question 4

What are the Free nerve endings?

Answer 4

Thermal receptors and Nociceptors

Question 5

What are the two Mechanoreceptors specialized doe proprioception? What does each one sense?

Answer 5

Muscle spindles: muscle length

Golgi tendon organs: muscle tension

Question 6

What are the four qualities of a stimulus?

Answer 6

Modality
Location
Intensity and duration

Question 7

What are the 5 sensory modalities?

Answer 7

Vision, hearing, touch, taste and smell

Question 8

How is intensity signaled?

Answer 8

Firing rate

Question 9

How is duration signaled?

Answer 9

Time course of response

Question 10

Between Meissner’s corpuscule, Merkel’s disk, Pacinian corpuscule and Ruffini’s ending, which are slowly adapting and which are rapidly adapting?

Answer 10

Meissner’s and Pacinian are rapid

Merkel’s and Ruffini’s are slowly

Question 11

What are the different types of mechanosensitive ion channels?

Answer 11

• channels sensitive to stretch of lipid bilateral
• channels sensitive to force applied to extra cellular proteins linked to channel
• channels sensitive to force applied to intracellular proteins linked to channels

Question 12

How is spatial resolution enhanced?

Answer 12

Most 2nd order neurons have surround (lateral) inhibition in their receptive fields

Question 13

Explain 2 point discrimination and its link with surround inhibition if 2nd order neurons

Answer 13

Certain 2nd order neurons have surround inhibition which allows for an enhanced spatial resolution in a certain area: on spot will have a much stronger stimulus than what’s around it

Question 14

Where is two pont discrimination best?

Answer 14

In areas with highest innervation density: eg fingertips

Question 15

What are the primary afferent axons?

Answer 15

Axons bringing information from the somatic sensory receptors to the spinal cord or brain stem.

Question 16

Associate the sensory receptor with the axon size type

Answer 16

Proprioceptors of skeletal muscle—Aalpha

Mechanoreceptors of skin—Abeta

Pain temperature—Asigma

Pain, itch, temperature—C

Question 17

What are the 4 divisions of spinal cord?

Answer 17

Cervical
Thoracic
Lumbar
Sacral

Question 18

What is the dermatome?

Answer 18

The area of the skin and deeper tissues innervantes by a si file dorsal root

Question 19

What are the two general sensory pathways?

Answer 19

Dorsal Column- Medial lemniscal pathway system (touch, vibration, pressure, proprioception)

Spinothalamic tract: pain and temperature

Question 20

Describe the dorsal column-medial lemniscal pathway

Answer 20

1) dorsal columns (spinal cord)
2) dorsal column nuclei (medulla)
3) decussation into medial lemniscus (brainstem)
4) ventral posterior lateral nucleus (VPL) in Thalamus
5) primary somatosensory cortex (S1)

Question 21

Which axons project vibration and touch?

Answer 21

Myelinated Abeta axons

Question 22

Describe the trigeminal touch pathway

Answer 22

1) large Mechanoreceptor axons from face project through the trigeminal nerve to the principal sensory trigeminal nucleus.
2) From the principal sensory trigeminal nucleus, the pathway decussates and projects to the VPM in the thalamus.
3) from the thalamus it projects to the primary somatosensory cortex

Question 23

What do lightly myelinated Adelta fibers register?

Answer 23

Register fast, sharp first pain

Question 24

What do unmyelinated C fibers register?

Answer 24

Register duller, longer lasting second pain

Question 25

Describe the spinothalamic tract

Answer 25

1) A-alpha and C afferent synapse in the substantia gelatonisa of dorsal horn
2) the pathway decussates and travels up the cord I. The spinothalamic tract to the thalamus (VPL) and then to S1

Question 26

Explain what the ventral posterior complex projects to and from there where that part projects to and so on (1)

Answer 26

Ventral posterior complex to Brodmann’s areas 1,2,3a,3b

From there they all project to secondary somatosensory cortex which projects to amygdala and hippocampus

Area 2 also projects to parietal areas 5 and 7 which projects to motor and pre motor cortical areas

Question 27

What stimuli do areas 3b and 1 receive?

Answer 27

Cutaneous stimuli

Question 28

What stimuli do areas 3a and 2 receive?

Answer 28

Proprioceptive stimuli from muscles and joints

Question 29

Explain the functional columns in neocortex

Answer 29

• can be found within somatotopic map
• Neurons with same modality from pia to white matter
• rows of slowly adapting neurons and others of rapidly adapting neurons

Question 30

Why can you say about cortical map plasticity?

Answer 30

There can be a reorganization of cortical maps: maps are dynamic and adjust depending on the amount of sensory experience

Question 31

What is the posterior parietal cortex involved in?

Answer 31

1) involved in somatic sensation
2) involved in analysis of “where” things are from visual inputs
3) involved in sensation of where things are on your body or your interpersonal space

Question 32

Tectospinal Tract

Answer 32

Controls orienting reflex (looking towards light)

Projects out of superior colliculus, where RBG project, decussating right away and going into cervical musculature, including neck and shoulders.

Question 33

Area 4

Answer 33

Primary motor cortex, stimulate leads to movement of muscles on contralateral side.

Question 34

Area 6 - Broadman’s Area, “Higher Motor Areas”

Answer 34

Simulation leads to more complex movements

Lateral: Primary motor area
Medial: Supplementary motor area

Question 35

Movement planning

Answer 35

BA6 fires same amount of action potentials when acting out something as much as being given instructions to do so.