Somatosensation 2 and Motor Cortex

Question 1

What is the golgi tendon organ?

Answer 1

sensory receptor that detects changes in muscle tension

Question 2

Muscle spindles consists of __________ intrafusal muscle fibers - of _____ main types. (hint: numbers)

Answer 2

8-10 intrafusal fibers; 2 main types

Question 3

TRUE or FALSE: shortening the muscles causes depolarizations

Answer 3

FALSE: lengthening causes depol

Question 4

What are the 2 main types of muscle spindles?

Answer 4

Ia and II

Question 5

TRUE or FALSE: the rate of change of muscle length fires in a static (tonic) form in Ia and II afferents.

Answer 5

FALSE:
- rate of change of muscle length = dynamic (phasic); Ia
- muscle length = static (tonic); Ia and II

Question 6

Draw a diagram to show how Ia and II afferents are affected by an increase in muscle tension to a steady state.

Answer 6

slide 6; Ia = dynamic/phasic; IIa = static/tonic

Question 7

What does the golgi tendon organ (GTO) detect? muscle spindles? What kind of fibers are involved?

Answer 7

• GTO = muscle TENSION (GTO-Ib fiber)
• muscle spindle = rate of change of muscle length (dynamic/Ia); muscle length (static/II)

Question 8

Draw APs for how changes in muscle length in GTOIb, Ia, and II fibers.

Answer 8

slide 8
- GTO-Ib unaffected (does not detect changes in length)
- Ia = most bursting when there is a large and rapid CHANGE (increase or decrease) in muscle length
- II = no bursting, just tonic

Question 9

What kind of channels are on the golgi tendon organ? muscle spindles?

Answer 9

both GTO and muscle spindles have Piezo2 channels

Question 10

TRUE or FALSE: Group I and II afferents target the dorsal horn of the SC.

Answer 10

FALSE: target the VENTRAL horn

Question 11

which fiber goes to muscle spindles and GTOs? where does it synapse in the SC lamina?

Answer 11

• A-alpha
• synapse in lamina VII and IX

Question 12

Which 2 major tracts carry somatosensory information to the brain? What kind of information do they each convey?

Answer 12

• medial lemniscal tract = touch/proprioception
• spinothalamic tract = pain/temperature

Question 13

TRUE or FALSE: the medial lemniscal tract conveys 2nd order info to the cortex, whereas the spinothalamic tract conveys 3rd order info to the cortex

Answer 13

FALSE: both tracts convey 3rd order info

Question 14

Which nucleus in the ML tract conveys touch/proprioceptive info from the upper torso/limbs? lower torso/limbs?

Answer 14

• gracile = upper
• cuneate = lower

Question 15

Where does the crossover occur in the ML tract? ST tract?

Answer 15

• ML tract crosses at medulla
• ST tract crosses directly at spinal cord

Question 16

Which nucleus in the thalamus is involved in relaying somatosensory information?

Answer 16

ventro-posterior subnuclei

Question 17

Describe the topographic mapping for fine touch and vibration:
- which part of the thalamus does it synapse at?
- which part of the cortex do projections from the thalamus synapse at?

Answer 17

VPM (medial) + VPL (lateral) to area 1 and 3b

Question 18

Describe the topographic mapping for pain and temperature:
- which part of the thalamus does it synapse at?
- which part of the cortex do projections from the thalamus synapse at?

Answer 18

VPI (inferior) to S2 (secondary somatosensory cortex)

Question 19

Describe the topographic mapping for proprioception:
- which part of the thalamus does it synapse at?
- which part of the cortex do projections from the thalamus synapse at?

Answer 19

VPS (superior) to area 3a and 2

(note: area 3a can synapse on area 4, which is the motor cortex)

Question 20

Which area on the cortex does majority of somatosensory info go to?

Answer 20

area 3a

Question 21

What is the term used to describe overrepresentation of “important” areas on the cortex?

Answer 21

homunculus

Question 22

The tactile fovea refers to magnification of the ________ and __________.

Answer 22

face and hands

Question 23

In what kind of organiztion are whiskers somatotopically mapped in rats?

Answer 23

barrel cortex, where each barrel = 1 whisker

Question 24

What percentage of the somatosensory cortex in a star-nosed mole represents the rhinarium?

Answer 24

52% (more than half)

(i.e. large representation of the rhinarium in star-nosed mole)

Question 25

TRUE or FALSE: rats have a huge trigeminal nerve

Answer 25

FALSE: star-nosed moles (hint: rhinarium on face takes up most of the somatosensory cortex)

Question 26

Which cranial nerve is especially huge in star-nose moles?

Answer 26

trigeminal nerve (CN V)

Question 27

Which tentacle on the star-nose mole nose underlies majority of the cortical area in S1?

Answer 27

11

Question 28

How many somatosensory cortices do star-nose moles have?

Answer 28

3 (S1-S3)

Question 29

Which somatosensory cortex in the star-nose mole receives information only for the rhinarium?

Answer 29

S3

Question 30

While the rhinarium is the most largely represented appendage of the star-nosed mole's somatosensory cortex, the ____________________ is the most largely represented appendage of the african hedgehog's somatosensory cortex.

Answer 30

micro vibrissae

Question 31

Which appendage is most largely represented in the somatosensory cortex of the naked more rat?

Answer 31

incisors and areas around the incisors

Question 32

draw the pathways of info transmission from the brain to the spinal cord.

Answer 32

slide 16 (cerebral cortex, thalamus, basal ganglia, cerbellum, brainstem, spinal cord)

Question 33

TRUE or FALSE: you don't need cortex for movmenet

Answer 33

TRUE

Question 34

What are rhythmic motor patterns produced by?

Answer 34

central pattern generators (CPGs)

Question 35

What are CPGs?

Answer 35

assemblies of neurons that produce rhythmic patterns of neural activity without rhythmic inputs

Question 36

TRUE or FALSE: the MLR is found in the spinal cord

Answer 36

FALSE: in brainstem

Question 37

TRUE or FALSE: CPGs are found in the spinal cord

Answer 37

TRUE

Question 38

What does CPG activity look like in an intact animal's left and right limbs?

Answer 38

rippling (slide 19)

Question 39

Where in the brain do voluntary motor acts begin?

Answer 39

the primary motor cortex (MI)

Question 40

Where is the primary motor cortex found? What is it responsible for? Where does it relay motor signals to? Is it ipsilateral or contralateral?

Answer 40

- found in frontal lobe - responsible for executing voluntary movements - relays signals to brainstem and spinal cord - contralateral control

Question 41

TRUE or FALSE: the foot and face are very enlarged in the motor homunculus

Answer 41

FALSE: HAND and face enlarged

Question 42

What does prolonged stimulation (0.5s) of M1 areas elicit?

Answer 42

stereotyped, complex movements

Question 43

What stereotyped movements result from prolonged stimulation to the medial areas of the primary motor cortex?

Answer 43

hand to lower torso

Question 44

What stereotyped movements result from prolonged stimulation to the middle areas of the primary motor cortex?

Answer 44

arm to the chest

Question 45

What stereotyped movements result from prolonged stimulation to the lateral areas of the primary motor cortex?

Answer 45

arm to face

Question 46

Label a diagram of the action zones on the primary motor cortex.

Answer 46

slide 26

Question 47

Which action zones are particularly large?

Answer 47

reach and grasp

Question 48

What areas of the brain send information to M1 to aid in planning movements?

Answer 48

- supplementary motor cortex (SMA) - premotor cortex (PMC) - frontal eye field (FEF) - posterior parietal motor area (PMA)

Question 49

What does PMC firing signal? When does it fire?

Answer 49

- fire at appearance of cue - signal "intention"

Question 50

_____________ neurons fire when performing a task or watching someone else perform the task.

Answer 50

mirror

Question 51

What are the 2 regions where mirror neurons are found?

Answer 51

1. F5 in ventral PMC cortex 2. inferior parietal area in PMA