The Motor System and Spinal Cord. Definitions and Introduction.

Question 1

What is ataxia?

Answer 1

Mild incoordination.

Question 2

What is hyper-reflexia?

Answer 2

When a reflex is larger than normal.

Question 3

What is muscle paralysis?

Answer 3

Complete muscle weakness where the muscle is no longer functional.

Question 4

What is muscle paresis?

Answer 4

Partial muscle weakness.

Question 5

What is muscle spasticity?

Answer 5

Where muscles stay in a contracted state.

Question 6

Are all motor responses to stimuli voluntary or involuntary?

Answer 6

They can be voluntary or involuntary.

Question 7

What name is given to all of the motor neurons that originate from the brain?

Answer 7

Upper motor neurons.

Question 8

Where are the cell bodies of upper motor neurons located?

Answer 8

In the cortex or the brain stem.

Question 9

What name is given to motor neurons that are partly in the CNS or are totally outside the CNS?

Answer 9

Lower motor neurons.

Question 10

Where are the cell bodies of lower motor neurons located?

Answer 10

In the ventral grey horn of the spinal cord.

Question 11

What are the axons of lower motor neurons referred to as?

Answer 11

As spinal nerves.

Question 12

What name is given to the descending tracts of the spinal cord?

Answer 12

The lateral and ventral funiculi.

Question 13

Does synapsis occur between upper motor neurons and lower motor neurons?

Answer 13

Yes.

Question 14

What is the function of descending motor fibres?

Answer 14

They excite particular muscle groups.

Question 15

What happens when one muscle group is activated by descending motor fibres?

Answer 15

When one muscle group is excited another must be inhibited.

Question 16

Are lower motor neurons excitatory or inhibitory?

Answer 16

They are excitatory and inhibitory.

Question 17

Do upper motor neurons make decisions?

Answer 17

No, they only relay the message.

Question 18

What are movements are upper motor neurons responsible for?

Answer 18

Voluntary movements (both gross and fine).

Question 19

What motor neurons are responsible for maintenance of normal muscle tone and regulation of posture?

Answer 19

Upper motor neurons.

Question 20

What are the 2 major upper motor neuron systems?

Answer 20

The pyramidal system.

The extra pyramidal system.

Question 21

What is the first section of the motor pathway?

Answer 21

The extra pyramidal system of the upper motor neuron system.

Question 22

Where do the neurons of the extra pyramidal system originate from?

Answer 22

The brainstem.

Question 23

Do the axons of the neurons of the extra pyramidal system ever cross over?

Answer 23

They will either cross over immediately or they will not cross at all.

Question 24

In what tract will the neurons of the extra pyramidal system run in the spinal cord?

Answer 24

The ventral and lateral funiculus.

Question 25

What is the function of the neurons of the extra pyramidal system?

Answer 25

They transmit information from the brain to the lower motor neurons in the limbs, trunk and neck.

Question 26

What 2 influences will the extra pyramidal system have on muscles?

Answer 26

It helps to maintain subconscious muscle tone. It controls large muscle groups to achieve smooth gait and stable posture.

Question 27

What is paresis?

Answer 27

Partial muscle weakness.

Question 28

What is paralysis?

Answer 28

No muscle response.

Question 29

What will be the effects of lesions to the extra pyramidal system?

Answer 29

Over stimulated lower motor neurons.

Question 30

What are the symptoms of lesions to the extra pyramidal system?

Answer 30

Complete muscle paralysis or gait deficiencies. Sometimes we can get hyper-reflexia as there are no inhibitory signals. A typical sign is muscle weakness and spasticity.

Question 31

Where do the neurons of the pyramidal system originate in the brain?

Answer 31

In the motor cortex.

Question 32

Do the neurons of the pyramidal system cross over?

Answer 32

Yes, they cross over in the medulla.

Question 33

What part of the spinal cord will the neurons of the pyramidal system run down?

Answer 33

The lateral funniculus.

Question 34

Where do the neurons of the pyramidal system synapse out of the spinal cord?

Answer 34

At the ventral horn.

Question 35

What happens after the neurons of the pyramidal system have synapsed out of the spinal cord?

Answer 35

They travel to their destination via lower motor neurons.

Question 36

What muscles are innervated by the neurons of the pyramidal system?

Answer 36

Small muscles that are used in co-ordinated activities or fine motor skills.

Question 37

What kind of thought is required for movements involving the pyramidal system?

Answer 37

Conscious thought.

Question 38

The pyramidal system is well developed in what animals?

Answer 38

Primates.

Question 39

What are the signs of damage to the pyramidal system?

Answer 39

Gait will be normal, but there will be mild postural deficiencies. There will also be mild muscle stiffness and spasticity.

Question 40

What are signs of damage to the pyramidal system in primates?

Answer 40

Damage to facial, hand or arm muscles.

Question 41

How do the symptoms of lesions in the extrapyramidal system differ from lesions in the pyramidal system?

Answer 41

Lesions in the extrapyramidal system result in abnormal gait. Lesions in the pyramidal system result in normal gait, but abnormal fine movements.

Question 42

How does the crossing over of neurons differ in the extrapyramidal system and pyramidal system?

Answer 42

EPS. Contralateral from the forebrain and brainstem and ipsilateral in the spinal cord. PS. Mostly ipsilateral.

Question 43

Will damage to the extrapyramidal system lead to effects in postural responses?

Answer 43

Extrapyramidal damage will affect the animals gait and their postural responses.

Question 44

What systems will be affected by upper motor neuron disease?

Answer 44

The pyramidal or extra pyramidal systems.

Question 45

What are the effects of upper motor neuron disease?

Answer 45

Muscle weakness and spasticity.

Question 46

Why do muscles tend to be hyper-reflexive if there is damage to the motor system?

Answer 46

As there is a loss of inhibitory neurons meaning the muscles receive much more innervation than normal.

Question 47

Will damage to the pyramidal system not affect the animals gait?

Answer 47

No.

Question 48

Is the extra pyramidal system a conscious or unconscious process?

Answer 48

An unconscious process.

Question 49

Will extrapyramidal damage affect gait and postural responses?

Answer 49

Yes.

Question 50

Will pyramidal damage affect gait and postural responses?

Answer 50

Only postural responses.

Question 51

Will damage to the unconscious proprioceptive pathway affect gait and postural responses?

Answer 51

Both.

Question 52

Will damage to the conscious proprioceptive pathway affect gait and postural responses?

Answer 52

Only the postural responses.

Question 53

Is there loss of muscle strength is there is damage to the proprioceptive pathways?

Answer 53

No, as the animal has only lost sensitivity, not the ability to use the limb.

Question 54

Will damage to the vestibular system affect gait and postural responses?

Answer 54

Both.

Question 55

What signs give clues that there is damage to the proprioceptive pathway and not the motor pathway?

Answer 55

If the animal has large ranges of movement it indicates the proprioceptive pathways are affected.

Question 56

Will muscle strength be affected if there is the vestibular system?

Answer 56

Muscle strength is unaffected.

Question 57

What are key signs that there is damage to the vestibular system?

Answer 57

These lesions often result in one side of the animal being affected e.g. a head tilt.

Question 58

What signs give clues that there is damage to the cerebellum?

Answer 58

No loss of muscle strength, but there is no menace response and tremors will be present.