The Motor System and Spinal Cord. Definitions and Introduction. Flashcards
What is ataxia?
Mild incoordination.
What is hyper-reflexia?
When a reflex is larger than normal.
What is muscle paralysis?
Complete muscle weakness where the muscle is no longer functional.
What is muscle paresis?
Partial muscle weakness.
What is muscle spasticity?
Where muscles stay in a contracted state.
Are all motor responses to stimuli voluntary or involuntary?
They can be voluntary or involuntary.
What name is given to all of the motor neurons that originate from the brain?
Upper motor neurons.
Where are the cell bodies of upper motor neurons located?
In the cortex or the brain stem.
What name is given to motor neurons that are partly in the CNS or are totally outside the CNS?
Lower motor neurons.
Where are the cell bodies of lower motor neurons located?
In the ventral grey horn of the spinal cord.
What are the axons of lower motor neurons referred to as?
As spinal nerves.
What name is given to the descending tracts of the spinal cord?
The lateral and ventral funiculi.
Does synapsis occur between upper motor neurons and lower motor neurons?
Yes.
What is the function of descending motor fibres?
They excite particular muscle groups.
What happens when one muscle group is activated by descending motor fibres?
When one muscle group is excited another must be inhibited.
Are lower motor neurons excitatory or inhibitory?
They are excitatory and inhibitory.
Do upper motor neurons make decisions?
No, they only relay the message.
What are movements are upper motor neurons responsible for?
Voluntary movements (both gross and fine).
What motor neurons are responsible for maintenance of normal muscle tone and regulation of posture?
Upper motor neurons.
What are the 2 major upper motor neuron systems?
The pyramidal system.
The extra pyramidal system.
What is the first section of the motor pathway?
The extra pyramidal system of the upper motor neuron system.
Where do the neurons of the extra pyramidal system originate from?
The brainstem.
Do the axons of the neurons of the extra pyramidal system ever cross over?
They will either cross over immediately or they will not cross at all.
In what tract will the neurons of the extra pyramidal system run in the spinal cord?
The ventral and lateral funiculus.
What is the function of the neurons of the extra pyramidal system?
They transmit information from the brain to the lower motor neurons in the limbs, trunk and neck.
What 2 influences will the extra pyramidal system have on muscles?
It helps to maintain subconscious muscle tone.
It controls large muscle groups to achieve smooth gait and stable posture.
What is paresis?
Partial muscle weakness.
What is paralysis?
No muscle response.
What will be the effects of lesions to the extra pyramidal system?
Over stimulated lower motor neurons.
What are the symptoms of lesions to the extra pyramidal system?
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.
Where do the neurons of the pyramidal system originate in the brain?
In the motor cortex.
Do the neurons of the pyramidal system cross over?
Yes, they cross over in the medulla.
What part of the spinal cord will the neurons of the pyramidal system run down?
The lateral funniculus.
Where do the neurons of the pyramidal system synapse out of the spinal cord?
At the ventral horn.
What happens after the neurons of the pyramidal system have synapsed out of the spinal cord?
They travel to their destination via lower motor neurons.
What muscles are innervated by the neurons of the pyramidal system?
Small muscles that are used in co-ordinated activities or fine motor skills.
What kind of thought is required for movements involving the pyramidal system?
Conscious thought.
The pyramidal system is well developed in what animals?
Primates.
What are the signs of damage to the pyramidal system?
Gait will be normal, but there will be mild postural deficiencies.
There will also be mild muscle stiffness and spasticity.
What are signs of damage to the pyramidal system in primates?
Damage to facial, hand or arm muscles.
How do the symptoms of lesions in the extrapyramidal system differ from lesions in the pyramidal system?
Lesions in the extrapyramidal system result in abnormal gait.
Lesions in the pyramidal system result in normal gait, but abnormal fine movements.
How does the crossing over of neurons differ in the extrapyramidal system and pyramidal system?
EPS. Contralateral from the forebrain and brainstem and ipsilateral in the spinal cord.
PS. Mostly ipsilateral.
Will damage to the extrapyramidal system lead to effects in postural responses?
Extrapyramidal damage will affect the animals gait and their postural responses.
What systems will be affected by upper motor neuron disease?
The pyramidal or extra pyramidal systems.
What are the effects of upper motor neuron disease?
Muscle weakness and spasticity.
Why do muscles tend to be hyper-reflexive if there is damage to the motor system?
As there is a loss of inhibitory neurons meaning the muscles receive much more innervation than normal.
Will damage to the pyramidal system not affect the animals gait?
No.
Is the extra pyramidal system a conscious or unconscious process?
An unconscious process.
Will extrapyramidal damage affect gait and postural responses?
Yes.
Will pyramidal damage affect gait and postural responses?
Only postural responses.
Will damage to the unconscious proprioceptive pathway affect gait and postural responses?
Both.
Will damage to the conscious proprioceptive pathway affect gait and postural responses?
Only the postural responses.
Is there loss of muscle strength is there is damage to the proprioceptive pathways?
No, as the animal has only lost sensitivity, not the ability to use the limb.
Will damage to the vestibular system affect gait and postural responses?
Both.
What signs give clues that there is damage to the proprioceptive pathway and not the motor pathway?
If the animal has large ranges of movement it indicates the proprioceptive pathways are affected.
Will muscle strength be affected if there is the vestibular system?
Muscle strength is unaffected.
What are key signs that there is damage to the vestibular system?
These lesions often result in one side of the animal being affected e.g. a head tilt.
What signs give clues that there is damage to the cerebellum?
No loss of muscle strength, but there is no menace response and tremors will be present.
