Anatomy of Spinal Cord, Motor SYstems & Spinal Reflexes Flashcards

(64 cards)

0
Q

interneurons

A

located in the center of the spinal cord
connect between other neurons of the spinal cord–when one group of motor neurons are activated, antagonist muscles are inhibited

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1
Q

alpha motor neurons

A

very large and rapidly conducting

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2
Q

spinal cord ends around

A

L1

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3
Q

lumbar cistern

A

where CSF is collected during lumbar puncture

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4
Q

cervical and lumbar enlargement

A

thickenings of gray matter that correspond to limbs

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5
Q

white matter decreases..

A

down the spinal cord because ascending sensory tracts are being added at each successive level as one ascends the cord and motor tracts are successively terminating as one progresses down the spinal cord

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6
Q

fastest conducting nerve fibers

A

1A

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7
Q

fastest fibers conduct about

A

100 m/s

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8
Q

unmyelinated C fibers conduct

A

more slowly than 1 m/sa

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9
Q

alpha motor neurons go to

A

extrafusal muscle fibers

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10
Q

gama motor neurons (slower) go to

A

intrafusal (spindle) muscle fibers

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11
Q

1a sensory fibers go to

A

muscle spindle

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12
Q

1b sensory fibers go to

A

golgi tendon organ

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13
Q

II sensory fibers go to

A

cutaneous mechanoreceptors

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14
Q

III sensory receptors go to

A

fast nociceptors; cold thermoreceptors

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15
Q

IV sensory fibers go to

A

slow nociceptors; warm

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16
Q

what is mostly responsible for activation of alpha motor neurons and where are they located?

A

interneurons

located in intermediate gray matter

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17
Q

motor pools

A

groups in spinal cords where all motor neurons are going to a single muscle (interneurons are adjacent)

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18
Q

most muscles receive innervation from

A

several spinal segments and nerve roots

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19
Q

motor neurons to hand located

A

laterally

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20
Q

motor neurons to axial muscles

A

medially

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21
Q

extensor muscles

A

ventral

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22
Q

flexor muscles

A

dorsal

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23
Q

each motor neuron branches to supply

A

multiple muscle fibers distributed over a significant portion of muscle

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24
motor unit
motor neuron and all of the muscle fibers it innervates
25
as you attempt to contract more forcefully
an additional motor unit becomes active-->increases firing rate-->3rd motor unit added-->slowly build up to muscle contraction where all motor units are firing at relatively high rate
26
type 1 muscle fibers
red muscle fibers-->lots of myoglobin small and weak high aerobic metabolism fatigue very slowly
27
type II muscle fibers
white muscle fibers large fast and strong fatigue more easily, because low aerobic metabolism
28
when you do things that require little strength, but much endurance
red muscles predominate
29
powerful movements use
white muscle fibers
30
intermediate type of muscle fiber
fast twitch, fairly powerful | more fatigue resistant
31
number and types of muscle fibers contained in a muscle
dependent on the nerve and cant be changed by external factors like exercise
32
exercise CAN
increase the strength of existing white muscle fibers or red muscle fibers to a greater degree
33
endurance exercises
tend to strengthen red muscle fibers
34
explosive excercises tend to
strengthen white fibers
35
3 classic spinal cord reflexes
muscle stretch inverse myotactic flexion reflex
36
which 2 require muscle receptors for stretch and tension?
muscle stretch reflex | inverse myotactic reflex
37
muscle stretch reflex
myotactic (deep tendon) | stretching a msucle results in contraction (tested with refelx hammer)
38
inverse myotactic reflex
stretch (to the point of muscle damage) | results in relaxation of muscle
39
flexion reflex (withdrawal)
painful stimulus of a limb results in withdrawal
40
muscle spindles
receptive organs that consist of modified skeletal muscle -->intrafusal fibers (gamma motor neurons)
41
muscle spindles are
few, but heavy innervation
42
outside of muscle spindle
extrafusal
43
pathway of 2 activation in muscle spindle
activation 1-->end of fiber contains contractile elements-->contract but no movement because too weak act 2-->contraction stretches central nuclei (central portion) of muscle fiber wrapped in annulospiral ending (sensory)-->muscle spindle activated
44
annulospiral ending
peripheral end of 1A afferent
45
why do we have patellar reflex
stabilize limb in a particular position and to prevent unintended movement
46
if you stretch the whole muscle
you stretch intrafusal and extrafusal muscle fibers
47
spindle afferent firing during and after stretch
during active stretch, burst of activity | followed by a new level of stretch with new baseline firing pattern
48
if muscle is shortened, the spindle
is unloaded and decreases in firing | renders the muscle spindle unable to detect any further stretch of the muscle from this new position
49
alpha-gama co activation
activation of gama motor neurons can align th emuscle spindle with the new position of the muscle, restoring its ability to detect any stretch frm its new position
50
what sets of length of muscle
muscle spindle | resists stretch frm this position
51
gamma loop
g motor neurons-->intrafusal fibers-->annulospiral ending-->reflex contraction of extrafusal to take tension off intrafusal
52
gamma loop is important for
smooth routine movements
53
spasticity
overreactivity of gama motor neurons results in excessively sensitive stretch reflex -->there is resistance to passive movement that is greater with faster movement due to activation of muscle stretch reflex
54
where do golgi tendon organs exist
in CT that attaches a muscle fiber to muscle tendon
55
pathway of golgi tendon organs
muscle fiber contracts-->tension placed on CT-->activate 1B afferent nerve fibers-->signals muscle contraction
56
golgi tendon organs and stretch
does not respond much | this is because muscle is much more compliant than CT, so CT might not feel tension (but this has a limit)
57
clasp knife phenomena
unusual feeling of giving way of a muscle that is being passively stretched overactive spinal reflex
58
most info from GTO?
cerebellum--> coodinating movement
59
withdrawal reflex
reflxion in limb extension in contralateral limb reciprocal connections in the other limbs
60
babinski response is an
overactive withdrawal reflex
61
withdrawal reflexes produce
physiologicla flexion
62
interneurons have patterns
therefore you can activate some interneurons encoding these patterns and dont have to control alpha motor neurons that are involved in movement individually (cough, sneeze, blink)-->pattern generating
63
one area of interneuron pattern generation
locomotoion (but not stong enoguh for functional ambulation in individuals where descending motor control systems are disrupted, such as spinal cord transacation)