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BRS 2 Neurology > 1b Neuromuscular Control > Flashcards

1b Neuromuscular Control Flashcards

1
Q

what are alpha motor neurones?

A

The lower motor neurones of the brainstem and the spinal cord that innervate the extrafusal muscle fibres of skeletal muscles

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2
Q

What does activation of the alpha motor neurones cause?

A

Muscle contraction

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3
Q

What is a motor neurone pool?

A

Pool which contains all the alpha motor neurones which innervate a single muscle

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4
Q

what is a motor unit?

A

a single motor neuron together with all the muscle fibres that it innervates. It is the smallest functional unit with which to produce force.

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5
Q

What does stimulation of a motor unit cause?

A

Contraction of all the muscle fibres in that unit

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6
Q

What are Type 1 muscle fibres?

A

Slow - smallest cell bodies and smalled dendritic trees, thinnest axons and slowest conduction velocity

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7
Q

What are Type 2A muscle fibres?

A

Fast, fatiguable - larger diameter cell bodies, larger dendritic trees, thicker axons and faster conductions

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8
Q

What are Type 2B muscle fibres?

A

Fast, fatigue resistant - larger diameter cell bodies, larger dendritic trees, thicker axons and faster conductions

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9
Q

What are Type 2B muscle fibres?

A

Fast, fatiguable - larger diameter cell bodies, larger dendritic trees, thicker axons and faster conductions

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10
Q

Which type of muscle fibre produces the largest amount of force?

A

Type 2B

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11
Q

How are the three motor unit types classified?

A

amount of tension generated, speed of contraction and fatiguability.

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12
Q

What are the two mechanisms by which the brain regulates the amount of force a single muscle produced?

A

rate coding and recruitment

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13
Q

What is recruitment?

A

When smaller units are recruited first, and as more force is required, larger units are then recruited - this allows for fine control when necessary

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14
Q

What is rate coding?

A

When different units can fire at different frequencies - higher firing rate is larger force

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15
Q

When does summation occur?

A

When the muscle units fire at a frequency which is too fast to allow the muscle to relax between AP’s

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16
Q

what are neurotrophic factors?

A

a type of growth factors which prevent neuronal death and promote the growth of the neurones after injury

17
Q

What is the effect of neurotrophic factors?

A

If a fast twitch muscle and a slow muscle are cross innervated, the soleus becomes fast and the FDL becomes slow.

The motor neuron has some effect on the properties of the muscle fibres it innervates.

18
Q

What causes a change from IIB to IIA fibres?

A

Training

19
Q

What causes a change from Type I to Type II?

A

Severe deconditioning or spinal cord injury, or microgravity

20
Q

What change is ageing associated with?

A

with loss of type I and II fibres but also preferential loss of type II fibres.

21
Q

What is the evidence that ageing results in a loww of type 1 and 2 fibres, with a preferential loss of type 2?

A

Larger proportion of type 1 fibres = slower contraction times

22
Q

What is a reflex?

A

An automatic response to a stimulus that involves a nerve impulse passing inward from a receptor to a nerve centre and then outward to an effector (as a muscle or gland) without reaching the level of consciousness.

23
Q

What is the Jendrassik Manoeuvre?

A

Try clenching the teeth, making a fist, or pulling against locked fingers when having patellar tendon tapped. The reflex becomes larger

24
Q

What type of control dominates in normal conditions?

A

Inhibitory control

25
Q

What reveals the excitatory control from the supraspinal areas?

A

Decerebration

26
Q

What can be the result of brain damage that causes a tonic stretch reflex?

A

Rigidity and spasticity

27
Q

What is hyper-reflexia?

A

Overactive reflexes due to a loss of descending inhibition, and is associated with upper motor neuron lesions

28
Q

What is Clonus (As a type of hyper-reflexia)?

A

Involuntary and rhythmic muscle contractions

29
Q

What is the Babinski Sign?

A

When the sole of the foot is stimulated with a blunt instrument, the big toe curls upwards (in adults, this is abnormal)

30
Q

When the sole of the foot is stimulated with a blunt object, what is the normal and pathological response in adult and kids?

A

Adults - Normal = Down, Pathological = Upwards
Children - Normal = Upwards

31
Q

What type of lesion is babinski sign associated with?

A

Upper motor lesions

32
Q

What is hyporeflexia?

A

Below normal or absent reflex - associated with lower motor neurone disease

BRS 2 Neurology (22 decks)

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