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Year 2: Neurobiology II > Lecture 5: Motor Control Part II > Flashcards

Lecture 5: Motor Control Part II Flashcards

1
Q

where is the corticospinal tracts in humans vs in vertebrate animals

A

humans = mainly in ventral horn and slightly in intermediate zone; S1 doesn’t contribute much

vertebrates = ventral and dorsal horns; takes up almost the whole gray matter in some animals

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2
Q

where are the rubrospinal and reticulospinal tracts located in the spinal cord

A

rubrospinal = intermediate zone

reticulospinal = ventral horn

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3
Q

LMN somatotopy distribution from medial to lateral in SC

A

trunk to distal extremity

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4
Q

LMN somatotopy distribution from anterior to posterior in SC

A

extensors to flexors

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5
Q

where does the medial vestibulospinal tract end and what does it control

A

ends in neck and upper thoracic region

controls B neck extensors

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6
Q

what does the medial corticospinal tract control

A

B postural flexor mm control

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7
Q

what does the pontine reticulospinal tract control

A

B proximal extremity extensors

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8
Q

what does the lateral vestibulospinal tract control

A

ipsilateral proximal extremity extensors

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9
Q

what does the medullary reticulospinal tract control

A

B distal extremity flexors

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10
Q

what does the rubrospinal tract control and where does it end in the SC

A

controls distal UE flexors

ends in neck and upper thoracic

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11
Q

what does the lateral corticospinal tract control

A

distal extremity flexors

fine motor

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12
Q

what is a motor neuron pool

A

LMNs for one mm all aligned in a column

more cranial portion of the column = proximal mm

more distal portion of column = distal mm

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13
Q

what is a motor unit; describe its integration

A

all mm fibers innervated by one LMN

fibers are intermingled, not homogenous

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14
Q

describe type I mm fibers

A

mainly found in red mm

slow twitch (S)

fatigue resistant

high concentration mitochondria

less glycogen

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15
Q

where are type II mm fibers mainly found

A

mainly in white mm

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16
Q

describe type IIa mm fibers

A

fast twitch
fatigue resistant (FR)
medium concentration of mitochondria and glycogen

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17
Q

describe type IIb mm fibers

A

fast twitch

fatiguable (FF)

low concentration of mitochondria

more glycogen

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18
Q

how can mm fibers be transformed

A

they can go between any form to another with strenuous work

type II can become type I

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19
Q

what type of mm contain what fiber types

A

all mm contain all 3 fiber types just with different ratios depending on the use of the mm

each type of mm fibers mingle together but they form individual motor units

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20
Q

describe small LMNs and their function

A

innervate type I fibers

less powerful but they can last for hours

used with fine motor and postural control

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21
Q

describe medium LMNs and their function

A

innervate type IIa fibers

more powerful and last about 1 hour

used for gross motor tasks (in between small and large LMNs)

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22
Q

describe large LMNs and their function

A

innervate type IIb fibers

most powerful but only last about 1 min

used for gross motor and power

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23
Q

describe the motor unit used for gross motor function, the types of fibers that make up that unit, and the purpose of this set up

A

gross motor = large motor unit (1 LMN innervates hundreds/thousands of mm fibers)

type IIa/IIb fibers controlled by medium and large LMNs

mm example: gastroc (FR/FF)

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24
Q

describe the motor unit used for fine motor function, the types of fibers that make up that unit, and the purpose of this set up

A

fine motor = small motor unit (1 LMN innervates several mm fibers)

less fibers to control per LMN = more accurate

type I mm fibers controlled by small LMN

mm example: extraoccular mm - 1:3 ratio of LMN to mm fibers; slow twitch

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25
how are saccades still fast with extraoccular mm even though they are slow twitch mm
due to the ratio of LMN to mm fibers (1:3) still fast movement
26
generally, 1 LMN controls one motor unit only; what is the exception to this
facial expression mm multiple LMNs overlap different facial mm
27
intensity of a stimuli is encoded by what
action potential
28
what are the steps for LMN activation/force production
1. presynaptic membrane AP travels to LMN axon terminal 2. postsynaptic membrane AP frequency travels along mm fibers 3. force is then produced by mm fiber contraction; force production directly related to AP frequency **there is a lag at each step due to the process of signal conduction
29
what is tetanus
AP over 80 Hz sustained mm contraction
30
what is spatiotemporal summation
different motor units at different locations
31
describe the size principle of motor unit recruitment
UMNs are all the same size; LMNs have 3 sizes small size LMNs (type I) activated first Ohms law - Voltage = current x resistance UMN activation signals (ACh release) induce the same current (I), but smaller LMNs have higher resistance (R) compared to Larger LMNs thus smaller LMNs create a larger voltage works like voltage gated ion channels to form action potential type IIa and IIb follow type I when more force is needed; this is regulated by GTOs
32
3 types mm contraction
concentric = shortening fibers isometric = stay same length eccentric = elongating mm fibers
33
active vs passive insufficiency
active = mm too short to create optimal force passive = mm too long to create optimal force these insufficiencies are found in multiple joint mm
34
2 structural types of muscle spindles
nuclear chain = nuclei aligned in chain/line nuclear bag = nuclei concentrated as in a bag
35
3 functional types of mm spindles
nuclear bag 1. static - detect length 2. dynamic - detect velocity nuclear chain 3. only static type - for length every spindle has at least 2 nuclear bag cells (1 static and 1 dynamic)
36
relationship between mirror neurons and mm spindles
mirror neurons transform sensory info to motor mm spindles transform motor info to sensory
37
extrafusal mm innervation
alpha motor neuron and free n endings
38
intrafusal mm innervation
gamma motor neurons
39
primary type Ia n innervate what type of intrafusal mm
central nuclear bag and chain cells both static and dynamic
40
secondary type II nn innervate what type of intrfusal mm
static nuclear bag and chain cells does NOT innervate dynamic bag cells; dynamic bag cells only innervated by type Ia and gamma motor neurons
41
what happens at the mm spindle with an isometric contraction
increase in Ia/II fibers from static nuclear bag and nuclear chain cells b/c mm is remaining static
42
what happens at the mm spindle with eccentric contraction
increase Ia on dynamic nuclear bag cells
43
what happens at the mm spindle with concentric mm contraction
decrease in dynamic stretch on mm spindle and this a decrease in Ia activity from nuclear bag cells
44
what motor neuron type will be activated with concentric contraction of intrafusal fibers
gamma motor neuron
45
what mm fibers give feedback to motor actions in regard to position sense and kinesthesia
position sense (stretch) = Ia and II from static nuclear bag and nuclear chain; info sent to cerebellum via posterior spinocerebellar tract kinesthesia (velocity) = Ia from dynamic nuclear bag cell
46
Number of CNs with motor function
9
47
what cranial nn are NOT controlled by corticospinal tract
III, IV, and VI
48
which CNs do not have B control but rather contralateral control bias
CNs V and XII vagus and hypoglossal
49
how is CN VII unique in its motor control
facial expression mm motor unit can be innervated by 2 or 3 LMNs facial expression is essential for social congnition
50
all head mm spindle Ia and II innervations are from what CN
CN V
51
what are the 3 ways UMNs can separately control LMNs for facial mm
cingulate motor cortex: - level IV - controls B scalp - from dorsal motor nucleus CN VII motor cortex and posterior parietal cortex: - level IV and III - controls contralateral face - from ventral motor nucleus deep brain structures: - level II - controls face and scalp - from amygdala, basal nuclei, and brainstem nuclei
52
LMNS for facial mm control what portion of the face
ipsilateral face and scalp
53
why does a regional injury to the CN VII anastomosis not affect facial expression
CN VII LMN can innervate different motor units
54
inter CN V and CN VII anastomosis controls what
proprioception of facial mm
55
what are the components of the spinal/brainstem reflex
receptor afferent = somatic or visceral sensory input may/may not have interneurons for integration efferent = somatic or visceral motor output effectors = muscles and glands
56
intrasegmental reflex
afferent and efferent signals at the SAME SPINAL LEVEL
57
intervsegmental reflex
afferent and efferent at MULIPLE SPINAL LEVELS
58
what type of loop is used in the spinal/brainstem reflex
bottom up/closed loop no higher level motor control
59
what is the flexor reflex
via cutaneous receptors aka withdrawal reflex/nociceptive reflex
60
how does the flexor reflex work
noxious stimuli is sent to SC via nociceptive axons (a delta fibers) interneuons in higher and lower segments elicit an intersegmental reflex axon terminals ascend/descend through lissauer's tract efferent outcome: flexors are excited and extensors are inhibited (limb is pulled away from noxious stimuli) - this only happens in UE flexor reflex
61
describe how the crossed extension reflex works
built upon flexor reflex noxious stimuli is recieved and travels to SC via nociceptive axons interneurons alternate excitatory vs inhibitory efferent result: - ipsilateral side = flexors are excited and extensors are inhibited (flexor reflex) - contralateral side = extensors are excited and flexors are inhibited this combo of effects allows the affected limb to withdrawal while allowing the unaffected limb to extend to maintain balance
62
describe how the mm stretch reflex works (aka DTR or myotatic reflex)
example = patellar tendon reflex afferent = mm spindle in quads alpha motor neurons in quads are activated - myotatic reflex- monosynaptic - intrasegmental reflex - afferent/efferent at same lvl alpha motor neurons in HS are inhibited - via interneurons - intersegmental reflex - afferent/efferent at diff. lvl total effect = knee ext/knee jerk reflex
63
biceps reflex spinal level and nerve
C5 musculocutaneous
64
brachioradialis reflex spinal level and nerve
C6 radial n
65
triceps reflex spinal level and nerve
C7 radial n
66
patellar (quads) reflex spinal level and nerve
L4 femoral n
67
achilles (gastroc/soleus) reflex spinal level and nerve
S1 tibial n
68
true deep tendon reflex is controlled by what? how does this work?
controlled by GTO excitatory AND inhibitory neurons total effect depends on which interneurons are activated has temporal/serial and spatial/parallel patterns motor units exerting heavily will be inhibited (protective) involved in size principle during motor recruitment; helps the right size mm fibers be recruited
69
importance of GTO reflex
allows fine adjustments of force production during ordinary motor activities initiates additional forms of autogenic inhibition at higher tension levels
70
what causes the clinical presentation of "clasp knife effects"
constant resistance results to autogenic inhibition through GTO reflex like PNF?
71
describe how reflexes can be modulated by the UMN system
mm spindle- Ia fiber conducts signal to SC various segments = spinal reflex higher levels = conscious perception and unconscious information of mm contraction can be overwritten by higher level cortical motor systems i.e. some people have to be distracted to test DTR
72
how are CPGS foundational for locomotion
can control rhythmic alternating mobility pattern no supraspinal control - cat can still walk on treadmill with SC cut no sensory feedback needed i.e. stepping reflex in babies
73
CPG neurons
propriospinal neurons (specialized interneurons)
74
CPG neurons form what tract and what does it control
fasciculus proprius tracts coordinate 4 limb locomotion
75
at what points with walking do you need control from UMN regions
gait patterns, reach, grasp, etc at start and stop of movement i.e. if you are walking and suddenly trip on something and need to catch yourself
76
CPGs relation to locomotion provides a new hope for what
locomoting pathologies i.e. stroke, TBI, PD, SCI, etc
77
voluntary locomotor regions are continuous components of what
reticular formation
78
what are the 2 voluntary locomotor regions
1. diencephalic locomotor region (DLR) - in thalamus 2. mesencephalic locomotor region (MLR) - boundary of midbrain and pons/pedunculopontine junction
79
function/regulation of voluntary locomotor regions
still regulated by hierarchical control system functions to coordinate CPGs
80

Year 2: Neurobiology II (10 decks)

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