The motor system lecture 20

Question 1

Describe the visually guided task used by Passingham in 1987

Answer 1

Monkey had to press a button when a light flashes to get a treat

Question 2

Describe the internally guided task

Answer 2

Monkey had to pull, lift and twist to get a treat

Question 3

Lesions were made in which two areas by Passingham?

Answer 3

The premotor cortex or the supplementary area

Question 4

Monkeys with a lesion in the premotor cortex made errors on which tasK?

Answer 4

The visually guided task

Question 5

Monkeys with lesions in the supplementary area made errors in which task?

Answer 5

The internally guided task

Question 6

What type of firing is shown in the motor cortex?

Answer 6

Short lead- with no preference for visual or internally guided tasks

Question 7

What is short lead firing?

Answer 7

Firing just before a movement

Question 8

What is long lead firing?

Answer 8

Firing a long time before a movement

Question 9

What are the cells in the premotor cortex firing patterns?

Answer 9

Short lead with a preference for visually guided tasks, some cells fire no matter the guidance

Question 10

What are the firing in the SA like?

Answer 10

Both short lead and long lead. Short lead cells have no preference, long lead cells fire more for internally guided tasks.

Question 11

Which area allows communication between hemispheres?

Answer 11

The SMA

Question 12

What sort of experiment showed connections from SMA to other hemisphere?

Answer 12

Tracer experiments

Question 13

What sort of movement does this allow for?

Answer 13

Coordinated bilateral movement

Question 14

A monkey with a lesion in SMA performs a bimanual movement how?

Answer 14

Hands mirror each other- SMA is crucial for uncoupling the hands and allowing them to perform different movements

Question 15

What are acallosal patients?

Answer 15

People missing all or part of their corpus callosum- the part which connects the two hemispheres

Question 16

What sort of movements are acallosal patients able to do well and why?

Answer 16

Movements which are different on each side. Because each SMA is more able to control the contralateral side independently without interference from the other side

Question 17

Which area of the premotor cortex is important for encoding grasp?

Answer 17

PMv-F5

Question 18

Describe the role of the ventral premotor cortex

Answer 18

Involved in encoding a library of different grasps to plan movements and also learn and copy from other movements

Question 19

In which area of the spinal cord are motor neurones found?

Answer 19

The ventral horn

Question 20

What is a reflex?

Answer 20

A fast involuntary response to sensory stimulus

Question 21

What are the three types of muscle spindles?

Answer 21

Dynamic nuclear bag fibre, static nuclear bag fibre, nuclear chain fibres

Question 22

What are the two types of sensory fibre which innervate the muscle spindles?

Answer 22

Type 1a and 2

Question 23

Which spindles do type 1a innervate

Answer 23

All three.

Question 24

What does the type 1a detect?

Answer 24

Rate of change of length

Question 25

Which muscle spindles do type 2 sensory fibres innervate?

Answer 25

Static nuclear bag fibre and nuclear chain fibres

Question 26

What do type 2 detect?

Answer 26

Change of length

Question 27

Why can muscle spindles contract?

Answer 27

Because they were muscle fibres that were converted into sense organs

Question 28

What type of motor neurones go to the spindles?

Answer 28

Gamma- dynamic and static

Question 29

Which spindles do the dynamic gamma motor neurone go to?

Answer 29

Only the dynamic nuclear bag fibre

Question 30

Which spindles do the static gamma motor neurones go to?

Answer 30

The static nuclear bag fibres and the nuclear chain fibres

Question 31

What can the motor neurones do the the spindles?

Answer 31

Change their sensitivity

Question 32

Describe the firing of a 1a sensory neurone when a muscle is stretched

Answer 32

The neurone has a dynamic response- it increases its firing rate as the muscle is stretched more. When stretching stops, firing returns to its steady state level which is higher now than it was before.

Question 33

What is the effect of activating a static gamma motor neurone during this?

Answer 33

It increases sensitivity to the steady state response

Question 34

What is the effect of activating a dynamic motor neurone?

Answer 34

Increases sensitivity to the dynamic response- so more increase in firing as stretching muscle

Question 35

Describe the monosynaptic pathway of the stretch reflex

Answer 35

When a muscle is stretched, it is detected by muscle spindle fibres which send afferent sensory neurones (1a and 2) to the spinal cord, passes through the dorsal horn and synapses onto motor neurone in the ventral horn which goes to the muscle and causes it to contract.

Question 36

Describe the inhibitory component of the stretch reflex

Answer 36

The sensory neurone also activates an inhibitory interneuron that inhibits the motor neurone which innervates the antagonistic muscle, relaxing it.

Question 37

Describe load compensation

Answer 37

When extra load is added to a muscle, it stretches and position moves. the stretch reflex allows quick contraction of the muscle to accommodate for the extra load

Question 38

What is the long latency smart reflex?

Answer 38

A longer more coordinated reflex which involves cortical processing to achieve a goal orientated movement

Question 39

Where are Golgi tendon organs found?

Answer 39

In tendons

Question 40

What do Golgi tendon organs detect?

Answer 40

Stretch of tendons

Question 41

What sensory fibres are associated with tendons?

Answer 41

1b fibres- inhibitory reflex