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Neuro yr 2 > motor control and movement disorders ppt 1 > Flashcards

motor control and movement disorders ppt 1 Flashcards

1
Q

what are extrafusal muscle fibres?

A

the external muscle fibres those attached to tendons

(Muscle spindles are found within the belly of a skeletal muscle. the special muscle fibres inside the spindle are called intrafusal muscle fibers. The regular muscle fibers outside of the spindle are called extrafusal muscle fibers.)

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2
Q

are alpha motor neurons upper or lower motor neurons? which parts of the CNS are they part of

A

lower motor neurons of the brainstem and the spinal cord

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3
Q

what type of muscle fibres do alpha motor neurons innervate?

A

extrafusal muscle fibres of the skeletal muscle

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4
Q

what does activation of an alpha motor neuron lead to?

A

CONTRACTION of ALL the muscle fibres in the respective MOTOR UNIT

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5
Q

what is a motor neuron pool?

A

all the ALPHA motor neurons innervating a single MUSCLE

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6
Q

what is a motor unit? (structurally and what is its significance)

A

structurally
a single motor neuron together with all the muscle fibres that it innervates.

significance
It is the smallest functional unit with which we can produce force.

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7
Q

how many muscle fibres does the average motor neuron supply?

A

600 muscle fibres

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8
Q

do we have more motor neurons or more muscle fibres?

A

more muscle fibres
(Humans have approximately 420,000 motor neurons and 250 million skeletal muscle fibres)

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9
Q

Where do you think there are more neurons per motor unit ?

A

more fine movement areas such as fingers

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10
Q

what are the types of motor unit

A

1) slow (S, type I)
2) fast, fatigue resistant (FR, type IIA)
3) Fast, fatiguable (FF type IIB)

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11
Q

what are the characteristics of type I motor neurons?

A

C.B. A. C.V. D.T. (CBA FOR A CV Dont Try)

cell body diameter: smallest
axons : thinnest

conduction velocity : slowest

dentritic trees : small

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12
Q

what are the characteristics of type IIA and IIB motor neurons compared to type I?

A

C.B. A C.V. D.T. (CBA FOR A CV Dont Try)

cell body diameter: larger
dentritic trees : larger
axons : thicker
conduction velocity : faster

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13
Q

which type of motor unit is THE fasteST and strongeST?

A

fast fatiguable (FF TYPE IIB)

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14
Q

Which motor unit type is most fatigue resistant?

A

slow (type I)

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15
Q

where is each type of motor neuron located?

A

they are all distributed throughout the muscle

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16
Q

which motor unit type evokes the STRONGEST force?

A

type II B fast fatiguable

17
Q

what are the 2 mechanisms of regulation of muscle force?

A

recruitment and rate coding

18
Q

what is the recruitment mechanism for regulation of muscle force and what does it allow for?

A

-motor units are recruited based on “size principle” from smaller units (slow) first
- allows for fine control for ex in writing

19
Q

what is the rate coding mechanism for regulation of muscle force?

A
  • motor units start by firing at lower frequencies
  • as firing rate increases the force produced by the unit increases due to summation
20
Q

what is summation?

A

when UNITS fire at frequency TOO FAST to allow the muscle to RELAX between arriving action potentials so the FORCES generated by subsequent **action potentials **are SUMMED.

21
Q

what is trophe’ and what are its functions

A

type of gorwth factor
prevent neuronal death
promote growth of neurons after injury

22
Q

are the qualities of a motor unit dependent or independent to the nerve that innervates them?

A

dependent

23
Q

what is cross innervation and what does it cause?

A

its when the neurons normally innervating a fast and a slow twitch motor unit interchange and it causes the slow unit to become faster than it was and the fats slower than it was (but not slower/ faster than the original slow/ fast units)

24
Q

what is the most common case of neuron type transition and in what conditions? (since theres plasticity in motor units)

A

type IIB to IIA (To fatigue resistance from fatiguable) following training

25
Q

what fibre type transition happens in responce to severe deconditioning or spinal cord injury?

A

type I to II

26
Q

what fibre type transitions happen in AGEING?

A

1) loss of type I AND II fibres
2) preferential loss of type II fibres (larger proportion of type i leading to slower contraction times)

27
Q

what is the neural pathway of reflex functions and what are some of their basic characteristics?

A

-nerve impulses pass INWARD from receptor to a nerve centre and then OUTWARD to an effector (muscle or gland)
- automatic/ involuntary / doesn’t reach level of conciousness
- responses to peripheral stimuli

28
Q

what does the magnitude and timing of a reflex function depend on?

A

-on intensity and onset of the stimulus
-magnitude can also be influenced by the descending (supraspinal) control of reflexes

29
Q

how do reflexes differ from voluntary movements? (other than the voluntary/involuntary)

A

once reflexes are released they cant be stopped

30
Q

what does “the jendrassik maneuvre” refer to?

A

-the descending (supraspinal) control of reflexes
-when the patellar tendon (knee) reflex becomes larger due to clenching the teeth, making a fist, or pulling against locked fingers

31
Q

how is the stretch reflex regulated by descending (supraspinal) control in normalcy?

A

inhibitory control dominates in normal conditions

32
Q

what is decerebration

A

when cerebrum is separated from brainstem

33
Q

what kind of descending control of the stretch reflex is observed after decerebration and how?

A

excitatory control because the cerebrum was the one inhibiting the excitatory signals originating below the cerebrum so upon separation the inhibitory signals are blocked

34
Q

what can be the stretch reflex related result of brain damage?

A

Rigidity and spasticity can result from brain damage giving over-active or tonic stretch reflex.

35
Q

what is the cause of overactive reflexes and the mechanism of its action

A

upper motor neuron lesions
loss of descending inhibition

36
Q

what is clonus?

A

an example of hyper reflexia where your foot contracts involuntary and rhythmically

37
Q

what is babinski sign

A

when your toe curls upwards instead of downwards after sole stimulated with sharp object (newborns upward is normal)

38
Q

what is hyporeflexia and common cause

A

below normal or absent reflexes associated with lower motor neuron diseases

Neuro yr 2 (13 decks)

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