L2.1 Motor Control

Question 1

Generally speaking, what is a motor skill?

Answer 1

A skill where the quality of movement is important, e.g. throwing a dart

Question 2

Generally speaking, what is a cognitive skill?

Answer 2

A skill where the decision or strategy is more important than the quality of the movement, e.g. moving a chess piece

Question 3

Answer 3

Question 4

Answer 4

Question 5

What happens at the dorsal horn? (Grey matter)

Answer 5

Where sensory neurons enter the spinal cord and synapse onto interneurons and projection neurons

Question 6

What happens at the anterior, lateral, and posterior fasciculus?

Answer 6

Areas where information travels up and down the spinal cord

Question 7

The ventral horn of grey matter contains what? (basic answer)

Answer 7

Motor neurons

Question 8

The intermediate grey matter of the spinal cord contains? (basic answer)

Answer 8

Autonomic innervations

Question 9

Why are there swellings in the ventral horns of grey matter at the C5, C8, L5, and S4 levels of the spinal cord?

Answer 9

These levels contribute to large plexuses, and thus have a large amount of motor neurons exiting.

Question 10

Sensory input neurons can terminate anywhere in which laminae layers?

Answer 10

Question 11

What does decussate mean?

Answer 11

To cross to the other side, usually in an X shape

Question 12

Define a reflex arc

Answer 12

A predictable, involuntary, stereotyped response to sensory input

Sensory information enters the spinal cord dorsally and synapses on interneurons or motor neurons directly to form a reflex arc

Question 13

Answer 13

Question 14

What does somatotopic map mean in relation to the spinal cord?

Answer 14

There is an order to where neurons lie in the spinal cord, it is not random or chaotic

Question 15

In the somatotopic organisation of the spinal cord, flexors are more _____ than extensors

Answer 15

More dorsal

Question 16

In the somatotopic organisation of the spinal cord, axial muscles are more ____ to distal muscles

Answer 16

More medial

Question 17

Which type of motor unit actually makes the body move?

Answer 17

Alpha motor unit

Question 18

What is the anatomical classification of a motor unit?

What is the physiological classification of a motor unit?

Answer 18

Anatomical: Single alpha motor neuron plus the muscle fibres it innervates

Physiological: Coordination between motor neuron and muscle fibres in accordance with its function, e.g. biochemical and neural specialisations

Question 19

What functional subclassifications of a motor unit are there?

Answer 19

Question 20

All skeletal muscle, except a few in the head, contract in response to being stretched.

This simple reflex involves a 2 neuronal pathway, and is known as?

Answer 20

Myotatic/stretch reflex

Question 21

Describe a basic stretch reflex in relation to the patella tendon

Answer 21

Question 22

In regards to a stretch reflex, what is the purpose of reciprocal inhibition?

Answer 22

Basically, if a stretch reflex is triggered, and a response is required (such as contracting the quadriceps), then the antagonistic muscle group (hamstings) should also be inhibited by the same relex, or otherwise, the body will be fighting itself

Question 23

Generally speaking, where are the muscle spindles monitoring stretch located?

What are they known as?

Answer 23

Within the middle 1/3 of the muscle

Intrafusal muscle fibres

Question 24

What type of fusal muscle fibre produces power and makes movement?

Answer 24

Extrafusal

Question 25

There are two types of intrafusal muscle fibres that monitor stretch within muscles. What is the name of the thinner one, and what is the name of the larger/broader one?

Answer 25

Thinner: Nuclear chain fibres Larger/broader: Nuclear bag fibres

Question 26

There are 2 types of **sensory endings** on the muscle spindle fibres, what are they and where do they mostly go to?

Answer 26

**Primary endings (group 1a)**: Single large neuron that ends on the centre of *all* fibres but *mostly* **Nuclear Bag Fibres** **Secondary endings (group II)**: few smaller neurons that end *mainly* on **Nuclear Chain Fibres** either side of the central zone

Question 27

Primary endings (group 1a) mostly synapse on Nuclear Bag Fibres; what is their role with regards to stretch?

Answer 27

They are sensitive to the onset of stretch but discharge at a slower rate during stretch - dynamic changes in stretch

Question 28

Secondary endings (group II) end mainly on Nuclear Chain Fibres; what is their role with regards to stretch?

Answer 28

They are not as sensitive at the onset of stretch but they remain active during stretch - steady stretch

Question 29

What type of muscle fibres do alpha motor neurons innervate?

Answer 29

Extrafusal muscle fibres

Question 30

What is the purpose of gamma motor neurons innervating intrafusal muscle spindles?

Answer 30

Well, definitely not to generate significant force. When a muscle is contracted, it shortens, which lessens the stretch placed on it and silences the muscle spindles. To compensate, gamma motor neurons generate some tension to return sensitivity to muscle spindles

Question 31

What is muscle tone? What causes it?

Answer 31

Question 32

Damage to either alpha motor units, or any part of the muscle spindle feedback, will cause?

Answer 32

Hypotonia/flaccidity

Question 33

Where are Golgi tendon organs found?

Answer 33

Interspersed in the collagen of musculotendinous junctions

Question 34

What type of sensory neurons attach to Golgi tendon organs?

Answer 34

Primary endings (Group 1b)

Question 35

1b sensory fibre endings are wound into?

Answer 35

Collagen in musculotendinous junctions around Golgi tendon organs

Question 36

Answer 36

Golgi tendon organ

Question 37

What do Golgi tendon organs monitor?

Answer 37

Muscle tension, detected by increased tension within the tendons. Necessary for when fine adjustments are required, like holding an egg They are stimulated by tension pulled on their long axis (parallel to muscle fibre orientation/line of pull of muscle)

Question 38

What can activation of the Golgi tendon organ lead to? How can this be silenced?

Answer 38

Detects increased muscle tension, can lead to inhibition of alpha motor neuron and, subsequently, relaxation of the muscle (Oh know I'm working too hard, better cut this out). Can be overridden by the descending pathway - e.g. when trying to lift a heavy weight/load and generate a large amount of force

Question 39

What is the withdrawal reflex?

Answer 39

Question 40

What is the crossed extensor reflex?

Answer 40