Anatomy of Spinal Cord, Motor SYstems & Spinal Reflexes

Question 0

interneurons

Answer 0

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

Question 1

alpha motor neurons

Answer 1

very large and rapidly conducting

Question 2

spinal cord ends around

Answer 2

L1

Question 3

lumbar cistern

Answer 3

where CSF is collected during lumbar puncture

Question 4

cervical and lumbar enlargement

Answer 4

thickenings of gray matter that correspond to limbs

Question 5

white matter decreases..

Answer 5

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

Question 6

fastest conducting nerve fibers

Answer 6

1A

Question 7

fastest fibers conduct about

Answer 7

100 m/s

Question 8

unmyelinated C fibers conduct

Answer 8

more slowly than 1 m/sa

Question 9

alpha motor neurons go to

Answer 9

extrafusal muscle fibers

Question 10

gama motor neurons (slower) go to

Answer 10

intrafusal (spindle) muscle fibers

Question 11

1a sensory fibers go to

Answer 11

muscle spindle

Question 12

1b sensory fibers go to

Answer 12

golgi tendon organ

Question 13

II sensory fibers go to

Answer 13

cutaneous mechanoreceptors

Question 14

III sensory receptors go to

Answer 14

fast nociceptors; cold thermoreceptors

Question 15

IV sensory fibers go to

Answer 15

slow nociceptors; warm

Question 16

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

Answer 16

interneurons

located in intermediate gray matter

Question 17

motor pools

Answer 17

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

Question 18

most muscles receive innervation from

Answer 18

several spinal segments and nerve roots

Question 19

motor neurons to hand located

Answer 19

laterally

Question 20

motor neurons to axial muscles

Answer 20

medially

Question 21

extensor muscles

Answer 21

ventral

Question 22

flexor muscles

Answer 22

dorsal

Question 23

each motor neuron branches to supply

Answer 23

multiple muscle fibers distributed over a significant portion of muscle

Question 24

motor unit

Answer 24

motor neuron and all of the muscle fibers it innervates

Question 25

as you attempt to contract more forcefully

Answer 25

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

Question 26

type 1 muscle fibers

Answer 26

red muscle fibers–>lots of myoglobin
small and weak
high aerobic metabolism
fatigue very slowly

Question 27

type II muscle fibers

Answer 27

white muscle fibers
large fast and strong
fatigue more easily, because low aerobic metabolism

Question 28

when you do things that require little strength, but much endurance

Answer 28

red muscles predominate

Question 29

powerful movements use

Answer 29

white muscle fibers

Question 30

intermediate type of muscle fiber

Answer 30

fast twitch, fairly powerful

more fatigue resistant

Question 31

number and types of muscle fibers contained in a muscle

Answer 31

dependent on the nerve and cant be changed by external factors like exercise

Question 32

exercise CAN

Answer 32

increase the strength of existing white muscle fibers or red muscle fibers to a greater degree

Question 33

endurance exercises

Answer 33

tend to strengthen red muscle fibers

Question 34

explosive excercises tend to

Answer 34

strengthen white fibers

Question 35

3 classic spinal cord reflexes

Answer 35

muscle stretch
inverse myotactic
flexion reflex

Question 36

which 2 require muscle receptors for stretch and tension?

Answer 36

muscle stretch reflex

inverse myotactic reflex

Question 37

muscle stretch reflex

Answer 37

myotactic (deep tendon)

stretching a msucle results in contraction (tested with refelx hammer)

Question 38

inverse myotactic reflex

Answer 38

stretch (to the point of muscle damage)

results in relaxation of muscle

Question 39

flexion reflex (withdrawal)

Answer 39

painful stimulus of a limb results in withdrawal

Question 40

muscle spindles

Answer 40

receptive organs that consist of modified skeletal muscle –>intrafusal fibers (gamma motor neurons)

Question 41

muscle spindles are

Answer 41

few, but heavy innervation

Question 42

outside of muscle spindle

Answer 42

extrafusal

Question 43

pathway of 2 activation in muscle spindle

Answer 43

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

Question 44

annulospiral ending

Answer 44

peripheral end of 1A afferent

Question 45

why do we have patellar reflex

Answer 45

stabilize limb in a particular position and to prevent unintended movement

Question 46

if you stretch the whole muscle

Answer 46

you stretch intrafusal and extrafusal muscle fibers

Question 47

spindle afferent firing during and after stretch

Answer 47

during active stretch, burst of activity

followed by a new level of stretch with new baseline firing pattern

Question 48

if muscle is shortened, the spindle

Answer 48

is unloaded and decreases in firing

renders the muscle spindle unable to detect any further stretch of the muscle from this new position

Question 49

alpha-gama co activation

Answer 49

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

Question 50

what sets of length of muscle

Answer 50

muscle spindle

resists stretch frm this position

Question 51

gamma loop

Answer 51

g motor neurons–>intrafusal fibers–>annulospiral ending–>reflex contraction of extrafusal to take tension off intrafusal

Question 52

gamma loop is important for

Answer 52

smooth routine movements

Question 53

spasticity

Answer 53

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

Question 54

where do golgi tendon organs exist

Answer 54

in CT that attaches a muscle fiber to muscle tendon

Question 55

pathway of golgi tendon organs

Answer 55

muscle fiber contracts–>tension placed on CT–>activate 1B afferent nerve fibers–>signals muscle contraction

Question 56

golgi tendon organs and stretch

Answer 56

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)

Question 57

clasp knife phenomena

Answer 57

unusual feeling of giving way of a muscle that is being passively stretched
overactive spinal reflex

Question 58

most info from GTO?

Answer 58

cerebellum–> coodinating movement

Question 59

withdrawal reflex

Answer 59

reflxion in limb
extension in contralateral limb
reciprocal connections in the other limbs

Question 60

babinski response is an

Answer 60

overactive withdrawal reflex

Question 61

withdrawal reflexes produce

Answer 61

physiologicla flexion

Question 62

interneurons have patterns

Answer 62

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

Question 63

one area of interneuron pattern generation

Answer 63

locomotoion (but not stong enoguh for functional ambulation in individuals where descending motor control systems are disrupted, such as spinal cord transacation)