Somatosensation 2 and Motor Cortex Flashcards
What is the golgi tendon organ?
sensory receptor that detects changes in muscle tension
Muscle spindles consists of __________ intrafusal muscle fibers - of _____ main types. (hint: numbers)
8-10 intrafusal fibers; 2 main types
TRUE or FALSE: shortening the muscles causes depolarizations
FALSE: lengthening causes depol
What are the 2 main types of muscle spindles?
Ia and II
TRUE or FALSE: the rate of change of muscle length fires in a static (tonic) form in Ia and II afferents.
FALSE:
- rate of change of muscle length = dynamic (phasic); Ia
- muscle length = static (tonic); Ia and II
Draw a diagram to show how Ia and II afferents are affected by an increase in muscle tension to a steady state.
slide 6; Ia = dynamic/phasic; IIa = static/tonic
What does the golgi tendon organ (GTO) detect? muscle spindles? What kind of fibers are involved?
- GTO = muscle TENSION (GTO-Ib fiber)
- muscle spindle = rate of change of muscle length (dynamic/Ia); muscle length (static/II)
Draw APs for how changes in muscle length in GTOIb, Ia, and II fibers.
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
What kind of channels are on the golgi tendon organ? muscle spindles?
both GTO and muscle spindles have Piezo2 channels
TRUE or FALSE: Group I and II afferents target the dorsal horn of the SC.
FALSE: target the VENTRAL horn
which fiber goes to muscle spindles and GTOs? where does it synapse in the SC lamina?
- A-alpha
- synapse in lamina VII and IX
Which 2 major tracts carry somatosensory information to the brain? What kind of information do they each convey?
- medial lemniscal tract = touch/proprioception
- spinothalamic tract = pain/temperature
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
FALSE: both tracts convey 3rd order info
Which nucleus in the ML tract conveys touch/proprioceptive info from the upper torso/limbs? lower torso/limbs?
- gracile = upper
- cuneate = lower
Where does the crossover occur in the ML tract? ST tract?
- ML tract crosses at medulla
- ST tract crosses directly at spinal cord
Which nucleus in the thalamus is involved in relaying somatosensory information?
ventro-posterior subnuclei
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?
VPM (medial) + VPL (lateral) to area 1 and 3b
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?
VPI (inferior) to S2 (secondary somatosensory cortex)
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?
VPS (superior) to area 3a and 2
(note: area 3a can synapse on area 4, which is the motor cortex)
Which area on the cortex does majority of somatosensory info go to?
area 3a
What is the term used to describe overrepresentation of “important” areas on the cortex?
homunculus
The tactile fovea refers to magnification of the ________ and __________.
face and hands
In what kind of organiztion are whiskers somatotopically mapped in rats?
barrel cortex, where each barrel = 1 whisker
What percentage of the somatosensory cortex in a star-nosed mole represents the rhinarium?
52% (more than half)
(i.e. large representation of the rhinarium in star-nosed mole)
TRUE or FALSE: rats have a huge trigeminal nerve
FALSE: star-nosed moles
(hint: rhinarium on face takes up most of the somatosensory cortex)
Which cranial nerve is especially huge in star-nose moles?
trigeminal nerve (CN V)
Which tentacle on the star-nose mole nose underlies majority of the cortical area in S1?
11
How many somatosensory cortices do star-nose moles have?
3 (S1-S3)
Which somatosensory cortex in the star-nose mole receives information only for the rhinarium?
S3
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.
micro vibrissae
Which appendage is most largely represented in the somatosensory cortex of the naked more rat?
incisors and areas around the incisors
draw the pathways of info transmission from the brain to the spinal cord.
slide 16 (cerebral cortex, thalamus, basal ganglia, cerbellum, brainstem, spinal cord)
TRUE or FALSE: you don’t need cortex for movmenet
TRUE
What are rhythmic motor patterns produced by?
central pattern generators (CPGs)
What are CPGs?
assemblies of neurons that produce rhythmic patterns of neural activity without rhythmic inputs
TRUE or FALSE: the MLR is found in the spinal cord
FALSE: in brainstem
TRUE or FALSE: CPGs are found in the spinal cord
TRUE
What does CPG activity look like in an intact animal’s left and right limbs?
rippling (slide 19)
Where in the brain do voluntary motor acts begin?
the primary motor cortex (MI)
Where is the primary motor cortex found? What is it responsible for? Where does it relay motor signals to? Is it ipsilateral or contralateral?
- found in frontal lobe
- responsible for executing voluntary movements
- relays signals to brainstem and spinal cord
- contralateral control
TRUE or FALSE: the foot and face are very enlarged in the motor homunculus
FALSE: HAND and face enlarged
What does prolonged stimulation (0.5s) of M1 areas elicit?
stereotyped, complex movements
What stereotyped movements result from prolonged stimulation to the medial areas of the primary motor cortex?
hand to lower torso
What stereotyped movements result from prolonged stimulation to the middle areas of the primary motor cortex?
arm to the chest
What stereotyped movements result from prolonged stimulation to the lateral areas of the primary motor cortex?
arm to face
Label a diagram of the action zones on the primary motor cortex.
slide 26
Which action zones are particularly large?
reach and grasp
What areas of the brain send information to M1 to aid in planning movements?
- supplementary motor cortex (SMA)
- premotor cortex (PMC)
- frontal eye field (FEF)
- posterior parietal motor area (PMA)
What does PMC firing signal? When does it fire?
- fire at appearance of cue
- signal “intention”
_____________ neurons fire when performing a task or watching someone else perform the task.
mirror
What are the 2 regions where mirror neurons are found?
- F5 in ventral PMC cortex
- inferior parietal area in PMA
