8.0 Motor Systems Flashcards Preview

MedST IB: Neurobiology and Human Behaviour (NHB) > 8.0 Motor Systems > Flashcards

Flashcards in 8.0 Motor Systems Deck (105)
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What is a consequence of a lesion in:

a) Association cortex
b) Cerebellum
c) Brainstem
d) lower motor neuron
e) Primary motor cortex/upper motor neuron
f) Basal ganglia

a) Association cortex → apraxia
b) Cerebellum → Ataxia/poor coordination
c) Brainstem → Postural deficits
d) lower motor neuron → Flaccid paralysis
e) Primary motor cortex/upper motor neuron → Spastic paralysis
f) Basal ganglia → Hyper/hypokinesia


Upper motor neuron vs lower motor neuron lesions:

Upper motor neuron = exaggerated reflexes + spastic paralysis

Lower motor neuron = Loss of reflexes + flaccid paralysis


Define ataxia:

Neurological disorder of voluntary coordination of muscle movements


What is noise (with regards to neural signals)?

Random variation in neural signals


What is the motor equivalence problem?

Describes redundancy in the motor system
Goal directed movement can be achieved in different ways


Define non-linearity

Mixing individual motor commands does not produce predictable results


Define non-stationarity

Behaviour of motor systems can change over time

Muscle contraction depends on history (thixotropy)


Define thixotropy

Muscle contraction depends on history


Define negative feedback systems:

A sensed parameter is compared to a desired 'set point'
If they match → no output
If they differ → system will generate a corrective action


Examples of negative feedback systems:

1) Blood glucose
2) Temperature
3) Respiration rate
4) Blood pressure


Advantages of negative feedback systems:

Automatically compensate for unpredicted events that cause deviation from set point (e.g. noise)


Disadvantages of negative feedback systems:

1) Time delays (error signal can be out of date by the time it reaches brain)
2) Instability and oscillation


Define feed-forward systems:

Motor commands are prepared (by estimation) in advance based on sensory information available

Fast movements need feed-forward predictive control


What is an internal model system?

Brain contains an internal model system - it is a representation of the mechanics of the body and the behaviour of the external world


What are the two types of the internal model system?

1) Inverse model
- Starts with desired movement
- Needs to be learnt

2) Forward model
- Predicts the consequences of motor commands (before and during movement)
- Needs internal feedback or efference copy


Define efference copy

An internal copy created of the efferent motor signal, which is input into a forward model


What brain structures are regarded as centres for feedforward control?

1) Cerebellum
2) Motor cortex


Where are the alpha-motoneurons located in the spinal cord?

Ventral horn


Define a motor unit:

All the muscle fibres innervated by 1 motoneuron


What are the different motor unit categories?

Comment on anatomy, biochemistry and physiology



What is rate coding?

Mechanism of controlling motoneurons

Varying the motorneuron firing rate


What is motorneuron recruitment?

Mechanism of controlling motoneurons (more important than rate coding)

Varying the number of motoneurons recruited (↑ force needed → ↑ motoneurons recruited)


Define the size principle (motoneuron recruitment):

Motor units are recruited to action in an orderly sequence of increasing force


What are the 3 sources of input into motoneurons?

1) Spinal interneurons (most numerous)
2) Afferent fibres (only from muscle spindles)
3) Descending fibres (rare)


What is a proprioceptor?

A receptor that provides information about the state of the body (position/movement of joints/muscle force etc)


Define proprioception:

Perception of position and movement of the body (a.k.a. kinaestheia)


3 types of proprioceptors in motor system:

1) Muscle spindles afferents (signal stretch)
2) Golgi tendon organ afferents (signal tension)
3) Joint receptors (signal position and movement)


What are the different types of fibre in a muscle spindle?

1) Intrafusal
2) Extrafusal


What are the two types of fibre in an intrafusual fibre?

1) Bag fibre (dynamic response to changes in muscle length)
2) Chain fibre (Static response. Linear response)


What are the two types of sensory fibres in each intrafusal fibre?

1) Primary (Ia) spindle afferent (Aα)
2) Secondary (II) spindle afferent (Aβ)