Motor Control

Question 0

Where are MN for particular muscle are clustered in groups with associated gamma neurons? What is another name for this cluster?

Answer 0

Ventral horn
Lamina IX

AKA MN POOL

Question 1

Somatotopic MN arrangement in ventral horn?

Answer 1

Extensors - ventral
Flexors - dorsal
Trunk - medial
Axilla - mid
Extremities - lateral

Question 2

How does threshold compare for large vs small motor units?

Answer 2

Low for small

High for large

Question 3

How does muscle spindle input compare for large vs small motor units?

Answer 3

Much input for small

Little input for large

Question 4

How does amt of capillaries compare for large vs small motor units?

Answer 4

Many for small

Few for large

Question 5

Hennemens size principle dictates that smaller neurons are recruited first. Recruitment of individual MNs progresses from sm to lg in stereotypic fashion except in ____________ type movements in which all units recruited nearly simultaneously.

Answer 5

Ballistic

Question 6

What percent of most everyday movements do smaller motor units contribute?

Answer 6

40%

Question 7

Active factors in muscle stiffness?

Answer 7

Actin and mysosin cross bridging during contraction

Question 8

Intrinsic factors in muscle stiffness?

Answer 8

Weak actin myosin bonds at rest. Longer duration, more bonds.

Question 9

Passive factors in muscle stiffness?

Answer 9

CT like Titin: keeps sarcomere from being pulled apart when muscle is stretched and keeps myosin in center of sarcomere.

Question 10

What factor contributes to normal muscle stiffness?

Answer 10

Titin.
Type Ia quick stretch NOT activated by slow stretch. Normally type II stretch response NOT activated. Weak actin myosin bonds give way.

Question 11

Describe the characteristics of abnormal stiffness due to UMN lesion.

Answer 11

Inc active factors of hyperreflexia
Inc UMN activity -> Hyperactive quick stretch reflex (+DTR)
Slow stretch reflex may manifest
Disuse can lead to contracture and more weak actin myosin bonds

Question 12

Describe the characteristics of abnormal stiffness due to contracture.

Answer 12

Loss of sarcomeres -> muscle shortens
Less Titin -> remaining Titin stretches more (passive factor)
More actin myosin bonds (intrinsic bonds)

Question 13

Reduced muscle stiffness corresponds with reduced DTR (hyporeflexia). What else?

Answer 13

LMN lesion: less actin myosin bonds to LMN: less intrinsic factor
Dec UMN activity: dec active factors

Question 14

What is spinal shock called?

Answer 14

Diaschesis

Question 15

In acute SC injury what happens to resting membrane potential? Why?

Answer 15

Diaschesis is due to inability of membrane to reach threshold. CNS Lesion results I’m decreased EPSPs.

Question 16

Voluntary movement (automatic, routine, unique) is ___________ while reflexive movement is ___________.

Answer 16

Adaptive (closed loop)

Stereotyped (open loop) -> same output every time

Question 17

What type of movement is a “helper” and what type of movement is primarily responsible for motor control?

Answer 17

Reflexive helps

Voluntary is responsible

Question 18

True or false: you can consciously inhibit all reflexes.

Answer 18

False. Can inhibit some but not all reflexes.

Question 19

What factors contribute to information planning of proprioception and kinesthesia (the schema that dictates motor plan creation and adaptation)?

Answer 19

Muscle spindles
GTOs
Joint receptors
Cutaneous receptors

Question 20

Feed forward is associated with _________ loop.

Answer 20

Open

Question 21

Feedback is associated with _________ loop.

Answer 21

Closed

Question 22

Which loop requires real time adaptation and adjustment? How long?

Answer 22

Closed. Occurs at least 150-200 ms.

Question 23

Which loop is preprogrammed and too fast to use sensory info?

Answer 23

Open.

Question 24

GTOs can facilitate extensor muscle spindles during stance phase and inhibit the same muscle spindles in swing phase. This is an example of what response?

Answer 24

Bimodal response.

Question 25

Networks of spinal INTERNEURONS that activate LMN in reciprocal patterns of flex/ext for walking are called:

Answer 25

CPGs : central pattern generators

Question 26

CPGs adapt based on _________ input and are driven by __________.

Answer 26

Sensory input

Higher centers

Question 27

Crossed effects where activity on one side of spinal cord affects activity on other side is due to:

Answer 27

Central pattern generators