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Neurology > Week 2 Neuro Part 2 > Flashcards

Week 2 Neuro Part 2 Flashcards

1
Q

What type of lower motor neurones innervate the muscle bulk

A

alpha motor neurones

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2
Q

What type of lower motor neurone innervate a muscle spindle

A

gamma motor neurones

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3
Q

where do the axons of lower motor neurons exit the spinal cord

A

the ventral roots

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4
Q

How are motor neurone distrinuted in the spinal cord

A

they are not distriuted equally - there are higher numbers in the cervical enlargement and lumbar enlargement

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5
Q

What is a motor unit

A

the alpha motor neurone and all of the skeletal muscle fibres it innervates - ies the smallest functional component of the motor system

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6
Q

what is the motor neurone pool

A

the collection of alpha motor neurones that innervates a single muscle

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7
Q

How is the force of muscle contraction graded

A

frequency of action potentials

recruitment of additional synergistic motor units

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8
Q

How are lower motor neurones cell bodies distributed in the ventral horn

A

those innervating axial muscles are more medial, distal muscle are more lateral

those innervating flexors are dorsal, extensors are ventral

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9
Q

What ate type one muscle fibres

A

slow oxidative - slow contraction and relaxation
resist fatigue
red fibres

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10
Q

what are type two a fibres

A

fast contraction an relaxation fatigue resistant

red fibres

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11
Q

what are type 2 b fibres

A

fast contraction but easily fatigued
white fibres
poorly vascularised

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12
Q

which skeletal muscle fibres types have high myoglobin and which have low

A

types 1 and 2a - high

type 2b - low

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13
Q

which type of motor unit is most numerous

A

slow

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14
Q

which type of muscle fibres are associated with fast fatiguing motor units

A

type 2b

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15
Q

What type of muscle fibres are associated with fatigue resistant muscle fibres

A

Type 2a

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16
Q

what type of muscle fibre is associated with slow motor units

A

type 1

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17
Q

what type of motor neurone is required for standing

A

slow - with type 1 muscle fibres - resisting fatigue

18
Q

What type of motor unit is required for walking/jogging

A

fast fatigue resistant - type 2a muscle fibres

19
Q

What type of motor unit is require for movements such as jumping

A

fast fatigable - type 2b

20
Q

what does it mean to have a small motor unit

A

each alpha fibre is only supplying a few muscle fibres - needed for fine movements eg extraocular eye movement

21
Q

what does it mean to have a large motor unit

A

each alpha motor neurone supplies a large number of muscle fibres

22
Q

What is the myotatic reflex

A

when a skeletal muscle is stretched in contracts

23
Q

what organ within the muscle senses the change in length

A

muscle spindle

24
Q

what motor neurons are the efferents for the muscle spindle

A

gamma motor neurones

25
Q

What neurotransmitter mediates the myotatic reflex

A

glutamate

26
Q

what is different about mytatic reflexes

A

it is a monosynaptic reflec arc - synapse occurs in the spinal cord

27
Q

What sensory neurones innervate the spindle fibres and act as the the afferent limb of the reflex arc

A

Ia sensory neurones

28
Q

How can the intrafusal fibres be subdivided in the muscle spindle

A

Bag 1 - sensitive to rate of change of muscle length - innervated by dynamic gamma motor neurones

bag 2- sensitive to changes in absolute length of muscle fibre - innervated by static gmn

chain fibres - sensitive to absolute length - static gamma fibres

29
Q

which afferent fibre is more sensitive to rate of change of muscle lenght

A

1a

30
Q

Which afferent fibres is more sensitive to changes in absolute length

A

II

31
Q

Where are Golgi tendons located

A

at the junction of muscle and tendon

32
Q

what do Golgi tendons do

A

monitor changes in mucles tension in series with extrafusal fibres

they therefore act to regulate muscle tension to protect muscle form overload

33
Q

What sensory afferents innervate Golgi tendons

A

group Ib

34
Q

what is the inverse myotatic reflex

A

group Ib afferents form Golgi tendons synpats on inhibitory interneurons which synsaps on alpha motor neurons to relax the muscle

polysynaptic (unlike myotatic reflex which is monsynaptic)

35
Q

where are proprioceptive axons present

A

in connective tissue of joints eg joint capsules and ligaments

36
Q

where does proprioception arise from

A

muscle spindles
Golgi tendon organs
joint receptors

37
Q

what is reciprocal inhibition

A

when the extensor contracts - flexor must relax and vice versa

38
Q

what mediated the recipricol inhibition

A

inhibitory interneurons

39
Q

what do excitatory interneurons mediate

A

the flexor reflex

the crossed extensor reflex

40
Q

what is the flexor refelx

A

contraction of flexors occurs due to noxius stimulus eg pain

41
Q

what is crossed extensor reflex

A

noxius stimuli causes limb to extend - enhances postural support during withdrawal of foot from pain you do not fall over

Neurology (36 decks)

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