Segmental Motor Center

Question 1

Motor unit

Answer 1

motor neuron, axon & muscle fibers

‘Muscle unit’ = axon terminal & all the muscle fibers served

Question 2

Contractile elements work best at what legnth​

Answer 2

resting length

have the greatest number cross bridges

Question 3

Contractile elements at lengthened​ and shortened legnths

Answer 3

they do not work as well b/c less to grab onto

Question 4

Connective tissue and tension

Answer 4

Connective tissue that is surrounding the muscles can add some passive tension

when you pull on the connective tissue there is some force on the as well

Question 5

Eccentric contraction vs. concentric in about of force producced

Answer 5

when you take the muscle beyond resting length there is passive tension that is added to the active tension

Question 6

Slow,S (slow oxidative, SO

Answer 6

Small motor neuron

Small amount of muscle fibers

Innervates slow twitch muscle fibers for slow contraction and relaxation time; relatively small forces, resistant to fatigue

Activities with sustained muscular contraction

Question 7

Fast, fatigue-resistant,FR

Answer 7

Largemotor neuron

mediumamount of muscle fibers/unit,

Innervates fast twitch muscle fibers (fast oxidative glycolytic, FOG) for fast contraction & relaxation; generate ~ 2x force as (S)

Question 8

Fast, fast-fatigue, FF

Answer 8

Largemotor neuron,

Large amount of muscle fibers/unit,

Innervates very fast twitch muscle fibers (fast glycolytic, FG) for very fast contraction & relaxation time

Generate large, rapid force;particularly important for brief exertions that require large force,running, jumping.

Question 9

size largest to smallest of FF SO and FG

Answer 9

FF FG S

Question 10

the larger the axon what happens to the speed of transmission

Answer 10

gets faster

Question 11

FF FG and S - which creates the greatest force

Answer 11

FF
has the most fibers per motor neuron

Question 12

1A afferent primarily targets what type of motor unit

Answer 12

slow oxidative

Question 13

Twitch tension time - slow

Answer 13

Slow rise of tension over a greater period of time (gradual force production)

Question 14

Twitch tension time - fast

Answer 14

fast twitch therefore fast force production

Question 15

Fatigue index Fast

Answer 15

rapid changes in high force production by not to be used for long periods

Question 16

FR energy use

Answer 16

Not many capillaries, anerobic metabolism or aerobic (phosphocreatine and glycolysis for their energy production)

Have both enzymes so can do both – so when we are training these are normally what we are training

Not to be used continually

Question 17

Slow: endurance

Answer 17

Endurance, use aerobic metabolism (have more capillary)

Highly vascularized

Question 18

en recruit fibers what order do we go in

Answer 18

S > FR > FF

this is an example of pre writing

Question 19

Sag

Answer 19

if you stimulate a certain rate that allows a relax in-between we will see a sag
rapidly formed cross bridges are less resistance to relaxtion

FF and FR

Question 20

Potentiation

Answer 20

slow

the cross bridges form slowly so they are resistant to relax (strong covalent bonds)

Question 21

fatigue time - FF

Answer 21

• FF are gone in less then a minute
• Loss of force
• FF are fatigable

Question 22

fatique​ time - slow

Answer 22

• Slow can produce force for a long time

Question 23

Three features of motor unit recruitment protect against fatigue:

Answer 23

Henneman’s size principle
SMC ‘half centers’
Asynchronous activation

Question 24

Henneman’s size principle

Answer 24

principle gradual ramping of force;

S to FR and FF; ‘small to large’

Only get to the fast ones when we need them for force

Question 25

SMC ‘half centers

Answer 25

extensor and flexor; alternating activation Alternative activates between agonist and antagonist

Question 26

Asynchronous activation

Answer 26

motor units activated intermittently during the voluntary contraction time We do not used the same motor unit when we are doing a contraction, there are different motor neuron within the pool

Question 27

Monosynaptic reflex

Answer 27

Ia afferent input from the muscle spindle to motor neuron activation back to the same (homonymous) muscle and its Modified by descending and peripheral inputs

Question 28

H-reflex, e.g. during locomotion

Answer 28

Electrical equivalent to the monosynaptic reflex Consider why? Consequences if not reduced? Bounding when running – descending paths influence stuff

Question 29

Alpha is what

Answer 29

motor neuron

Question 30

Gamma

Answer 30

MN to the muscle spindle to keep it sensitive

Question 31

Alpha-gamma co-activation is activated for what kind of contractions

Answer 31

all contractions

Question 32

Reciprocal inhibition

Answer 32

Ia Inhibitory Interneuron (IaIN) turns off (reciprocally inhibits) the antagonist SMC during activation of the agonist SMC

Question 33

IB afferent from where

Answer 33

GTO sensory neuron

Question 34

Autogenic inhibition point

Answer 34

Trying to turn off some motor neurons so that others must take over the load

Question 35

IB inhibitory internuron does what

Answer 35

regulates recruitment of agonist AMNs in the MN pool at any one time; turns off some active MUs, others take over for force production (a non-reciprocal inhibition).

Question 36

Recurrent inhibition

Answer 36

Renshaw (R) cells limit the rate and #of motor units active  in the MN pool at any one time. (a non-reciprocal inhibition)

Question 37

non-reciprocal inhibition example

Answer 37

Recurrent inhibition and Autogenic inhibition

Question 38

reciprocal inhibition example

Answer 38

Reciprocal inhibition

Question 39

The ventral horn is organized into two parts

Answer 39

Medial and lateral motor nuclei

Question 40

Propriospinal interneurons (INs) communicate infromation where

Answer 40

information over short and long distances within the spinal cord. Only travel between segment of the spinal cord (communication within the spinal cord)

Question 41

Medial motor nuclei go to what kind of muscles

Answer 41

axial and proximal limb girdle muscles

Question 42

Medial motor nuclei connection

Answer 42

Have an interneuron that connects both sides – this allows us to activate things together If there in an input on the medial side, there will be activation on both sides

Question 43

Lateral motor nuclei to what kind of muscles

Answer 43

limb muscle - for limb movement

Question 44

Lateral motor nuclei connection

Answer 44

Do not have a connection between the two sides – we normally move one limb at at a time

Question 45

Descending connections medial MN

Answer 45

Ventromedial  pathways impact medial MNs Bilateral effects

Question 46

Descending connections lateral MN

Answer 46

Dorsolateral pathways impact lateral MNs

Question 47

Ascending connections for both medial and laterl MN

Answer 47

Ventrospinocerebellar tract Spinoreticular/spinothalamic

Question 48

Ventrospinocerebellar tract

Answer 48

To cerebellum – this compare what is happening the ventral horn to the cortex plans, and can make correction Info: motor copy – telling about the state of the of a segmental motor neuron

Question 49

Spinoreticular/spinothalamic

Answer 49

To brainstem centers

Question 50

segmental motor center is made up of

Answer 50

medial and lateral MN