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Neuroscience & Mental Health Y2 > Neuromuscular and Spinal Cord Control of Movement > Flashcards

Neuromuscular and Spinal Cord Control of Movement Flashcards

1
Q

What mechanism causes the graded effects of neuronal transmission

A

Summation

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2
Q
  • The degree of summation will determine how readily a neurone can ….
A

reach threshold to produce an AP

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3
Q

3 steps of activation at a NMJ:

A
  1. When an AP arrived at the MNJ, Ca2+ influx causes ACh release
  2. ACh binds to receptors on the motor end plate
  3. Ion channel opens- Na+ influx causes an AP in the muscle fibre
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4
Q

What causes MINIATURE END-PLATE POTENTIALS

A

At rest, individual vesicles release ACh at a very low rate in a motor neuron

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5
Q

What is the motor unit:

A

NAME GIVEN TO 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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6
Q

Stimulation of one motor unit causes contraction of how many fibres

A

all the muscle fibres in that unit

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7
Q

THE ALPHA MOTOR NEURON is the….

A

lower motor neurons of the brainstem and the spinal cord (the last neurons before the muscle fibre)

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8
Q

THE ALPHA MOTOR NEURON is located in…

A

the ventral horn of the spinal cord

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9
Q

motor neuron pool contains …

A

all alpha motor neurons innervating a single muscle

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10
Q

The 3 different motor unit types are:

A

Slow S type 1
Fast fatigue resistant, FR TIIA
Fast fatiguable FF, TIIB

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11
Q

Which motor unit has the largest diameter cell bodies, dendritic tress, axon thickness, and fastest conduction velocity

A

FF TIIB

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12
Q

2 mechanisms by which the brain regulates the force that a single muscle can produce?

A

RECRUITMENT

RATE CODING

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13
Q

Explain recruitment in regulating force produced by a motor neuron

A
  • Motor units are not randomly recruited- there is an order to this
  • Governed by the ”SIZE PRINCIPLE”- smaller units are recruited first (these are generally the slow twitch units)
  • As more force is required, more units are recruited
  • This allows for fine control e.g. writing, under which low force levels are required
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14
Q

Which type of motor unit is recruited first

A

Smaller units and so generally slow twitch

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15
Q

Explain rate coding in regulating force produced by a motor neuron

A
  • A motor unit can fire at a range of frequencies Slow units fire at a lower frequency
  • As the firing rate increases, the force produced by the unit increases
  • Summation occurs when units ire at frequency too fast to allow the muscle to relax between arriving APs
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16
Q

Which type of motor unit has the lowest firing frequency

A

Slow twitch T1

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17
Q
  • Summation occurs when units are at frequency too fast to …
A

allow the muscle to relax between arriving APs

18
Q

Motor unit and fibre characteristics are dependent on …

A

the nerve which innervated them

19
Q

If a fast twitch muscle and a slow muscle are cross innervated (their innervation is switched) what happens to speed of twitching

A

the slow becomes fast and the fast becomes slow

20
Q

Type I to II muscle fibre switching is possible in cases of … example of when this occurs.

A

severe deconditioning or spinal cord injury

Microgravity during spaceflights results in shift from slow to fast muscle fibre types

21
Q
  • Ageing is associated with loss of type I and II fibres but also preferentially loss of what type of fibre. What is evidence of this
A

type II

evidenced from slower contraction times

22
Q

REFLEX definition:

A

AN AUTOMATIC AND OFTEN INBORN RESPONSE TO A PERIPHERAL 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

Reflex response size is proportional to …

A

the size of the stimulus

24
Q

Describe the reflex pathway starting with the sensory receptor

A

Sensory receptor -> sensory neuron -> (interneuron -> inhibits antagonistic muscle) motor neuron -> effector

25
Q

What is a Volley, e.g. afferent volley or effect volley

A

collection of APs

26
Q

What detects stretch in the reflex arc

A

Muscle spindle

27
Q

What is the Hoffman reflex

A
  • Stimulate the nerve that you want to stimulate the muscle of interest electrically
  • Stimulate a mixed nerve right in the centre and it will send signals up to the spinal cord and down to the muscle
  • This allows you to achieve the same identical stimulation each time
  • Should result in a quick response resulting from immediate motor activation, and a slower response resulting from sensory and THEN motor activation (the second is called the Hoffman reflex)
28
Q

What test can enable us to work out which part of the NS is damaged

A

Hoffman Reflex

29
Q

Explain crossed extensor reflex

A

If you step on a plug, Not only is a response on the ipsilateral side to the stimulus required e.g. moving your foot off of the plug, but a response on the contralateral side is needed e.g. repositioning your other leg to stay balanced This is what we mean by crossed extensor

30
Q

How do you enhance the kneejerk reflex

A

ching our teeth or making a fist when having our patellar tendon tapped

31
Q

what is the Jendrassik manoeuvre

A

enhance the kneejerk reflex by clenching our teeth or making a fist when having our patellar tendon tapped- this is called the JENDRASSIK manoeuvre

32
Q

Explain the Jendrassik manoeuvre

A
  • Higher centres of the CNS exert inhibitory and excitatory regulation upon the stretch reflex
  • Inhibitory control dominates in normal conditions (N)
  • Decerebration reveals the excitatory control from supraspinal areas
  • Rigidity and spasticity can result from brain damage giving over-active or tonic stretch reflex
33
Q

HIGHER CENTRES INFLUENCE REFLEXES BY: (5)

A 
1) activating alpha motor neurone
activating inhibitory interneurons
activating propriospinal neurons
activating gamma motor neurons
activating terminals of afferent fibres
34
Q

HIGHER CENTRES AND PATHWAYS INVOLVED in reflexes are? (4)

A

Cortex
Red nucleus
Vestibular nucleus
Tectum

35
Q

Pathway the cortex controls in reflexes? and this does?

A

Corticospinal (fine control of limb movements and body adjustments)

36
Q

Pathway the Red nucleus controls in reflexes?

A

Rubrospinal (automatic movements of arm in response to posture/balance changes)

37
Q

Pathway the Vestibular nucleus controls in reflexes?

A

vestibulospinal (altering posture to maintain balance)

38
Q

Pathway the Tectum controls in reflexes?

A

tectospinal (head movements in response to visual information)

39
Q

HYPER-REFLEXIA is a classic symptom of ….

A

upper motor neurone disorders e.g. stroke

40
Q

CLONUS definition? Often seen in?

A

series of involuntary, rhythmic muscular contractions and relaxations (often seen in upper motor neurone disorders)

41
Q

BABINSKI SIGN is… often seen in people with ….

A

Stimulation on sole of foot with blunt instrument leads to an uncontrolled upward extension of the hallux (toe) in people with upper MN disorders

42
Q

Hyporeflexia is associated with XXXX diseases

A

lower motor neurone

Neuroscience & Mental Health Y2 (18 decks)

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