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Year 2 - Neuroscience > Neuromuscular & Spinal Cord > Flashcards

Neuromuscular & Spinal Cord Flashcards

1
Q

EPSP?

A

Excitatory Post Synaptive Threshold

Brings potential CLOSER to firing threshold

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2
Q

IPSP?

A

Inhibitory Post Synaptic Threshold

Brings potential FURTHER from firing threshld

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3
Q

Summation?

A

Graded effects of EPSP + IPSP

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4
Q

NMJ?

A 
Specialised synapse
BETWEEN the:
o motor neurone
AND
o motor end plate (muscle fibre cell membrane)
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5
Q

mEPPs?

A

Miniature End-Plate Potentials

At rest, individual vesicles release ACh at a very LOW rate causing mEPPs

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6
Q

Alpha motor neurones?

A

These are the LMNs of the brainstem & spinal cord - hence innervate skeletal muscle fibres

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7
Q

What contains ALL the alpha motor neruones innervating a single muscle?

A

Motor neuron pool

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8
Q

Somatotropic arrangement of alpha-neurones in the SC

A

In the ventral horn!

o Posterior = flexor
o Anterior = extensor
o Medial lateral = proximal
o Postolateral = distal

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9
Q

Motor Unit?

A

Single motor neurone
+
all the muscle fibres it innervates

i.e. stimulation of ONE motor unit causes contraction of ALL the muscle fibres in that unit

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10
Q

How many motor neurones innervate EACH muscle fibre?

A

ONE distinct motor neurone

i.e. two DIFFERENT MNs CANNOT innervate the same muscle fibre

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11
Q

Innervation ratio?

A

Number of muscle fibres innervated by a MN

i.e. lower the number = MORE precise the movement

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12
Q

3 types of Motor Units?

A

o SLOW (S, Type I)

o Fast, Fatigue Resistant (FR, Type IIA)

o Fast, Fatiguable (FF, Type IIB)

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13
Q

Type I Motor Unit?

A

SLOW

o smallest soma
o small dendritic trees
o thinnest axons

o SLOWEST conduction velocity

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14
Q

Type IIA Motor Unit?

A

FAST, FATIGUE RESISTANT

o larger soma
o larger dendritic trees
o thicker axons

o FASTER conduction velocity

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15
Q

Type IIB?

A

FAST, FATIGUABLE

o larger soma
o larger dendritic trees
o thicker axons

o FASTER conduction velocity

(same as Type IIA essentially!)

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16
Q

How are the 3 motor unit distributed?

A

Are NOT discretely located but spread out (OneNote!!)

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17
Q

What 3 properties are the 3 different motor unit types classified by?

A
  1. Tension generated
  2. Speed of contraction
  3. Fatiguability
18
Q

What 2 regulative mechanism in in place to regulate the force that a single muscle can produce?

A
  1. Recruitment

2. Rate coding

19
Q

How does ‘Recruitment’ regulate force production?

A

Governed by the ‘Size Principle’

o SMALLER units are recruited FIRST (generally slow twitch units)

o As MORE FORCE is required, more units are recruited

This allows for FINE CONTROL when low force is required

20
Q

How does ‘Rate Coding’ regulate force production?

A

via. rate of FIRING

o SLOW units fire at a LOWER frequency
o As the firing rate INCREASES, FORCE by the UNIT INCREASES

21
Q

In regards to ‘Rate Coding’ when does summation occur?

A

When the units fire at a frequency TOO FAST to allow the muscle to RELAX between arriving APs

22
Q

What are neurotrophic factors?

A

Type of GF

23
Q

Characteristics of neurotrophic factors?

A

o Prevent neuronal death

o Promote growth of neurones after injury

24
Q

Relationship between motor units, fibre characteristics & nerves?

A

Motor unit & fibre characteristics are DEPENDENT on the NERVE which INNERVATES them

i.e. if fast twich muscle (FDL or FHL) and a slow muscle (SOL) are CROSS-INNERVATED:
o the SOL becomes FAST
o the FDL becomes SLOW

25
Q

Under which conditions can fibre types change properties?

A

o Training:
Type IIB –> Type IIA

o Deconditioning/SC injury:
Type I –> Type II

o Ageing:
Loss of Type I & II (preferential loss of Type II so larger proportion of Type I)
i.e. hence why slower contraction times

26
Q

What are Extrapyramidal Tracts associated with?

A

Concerned with AUTOMATIC MOVEMENTS in response to stimuli (modify motor function)

27
Q

What somatotopic representation is associated with the coticospinal tracts in the SC?

A

1a - LATERAL CS.T

1b - ANTERIOR CS.T

1a has sacral, lumbar, thoraci and cervical regions

28
Q

Pathway of reflex reaction?

A
  1. Sensory receptor
  2. Sensory neurone
  3. Integration in interneurone
  4. Motor neurone
  5. Effector muscle
29
Q

Experiment to see how many synapses within a reflex arc?

A

A volley (an AP travelling past recording equipment)

The difference in time from the afferent volley to the IC efferent recording

(generally one synapse = 0.7ms)

30
Q

Monosynaptic (stretch) reflex?

A

e.g. knee-jerk reflex

When the patella ligament is hit:

  1. sensory stretch receptors activated
  2. sends impulse to integrating centre
  3. both to an INHIBITORY & EXCITATORY neurone to 2 different muscle groups
31
Q

What is beneficial about the Hoffman (H-) Reflex?

A

Done so electronically (rather than mechanically) via. patella hammer
SO
any difference in response due to person NOT human error

32
Q

What are the 2 waves seens in the Hoffman (H-) Reflex?

A

INITIAL M-wave

o direct response of muscle to the stretch with NO synpases (inital twitch after knee being hit)

H-reflex

o response of muscle a few ms later as the response has travelled through a few synapses (multiple fibres) - sensory neurone response exciting the motor neurone again

33
Q

Describe the H wave seen in the Hoffman (H-) Reflex

A

o it ACTIVATES at LOWER stimuli strengths BUT is SLOWER to fire

o DECREASES at HIGHER stimuli strength as motor cells get activates that fire AGAINST the normal flow & CANCEL out the AP

34
Q

Polysynaptic Reflexes - flexion withdrawal?

A

Reflexes that cross the spinal cord to the other side such that the other limbs do something to keep us upright

Called:
FLEXION withdrawal AND
CROSSED extensor

i.e. withdrawal of one leg in a reflex action & extensor of the other leg in the same reflex arc to ensure balance (gait)

35
Q

Jendrassik Manoeuvre?

A

Can influence reflex action with supraspinal control

i.e. clench teeth while knee jerk - will get a GREATER RESPONSE

36
Q

Explain the supraspinal control of reflexes

A

Higher centres of the CNS exert INHIBITORY & EXCITATORY REGULATION upon the stretch reflex

o INHIBITORY control DOMINATES in normal conditions

37
Q

What can affect the supraspinal control of reflexes?

A

Decerebration

Leads to hyperreflexia & spasticity (over-active or tonic stretch reflex)

38
Q

Gamma Reflex Loop?

A

(along with gamma motor neurones)
Ensure the muscle NEVER remains slack and so can remain SENSITIVE to stretch movements

Gamma neurones SHORTEN the spindle to maintain its sensitivity

39
Q

What is found synonymously with alpha motor neurones?

A

Gamma motor neurones!

So found together & fire together when needs be

40
Q

Why is hyperreflexia seen in stroke patients?

A

Loss of descending inhibition

Year 2 - Neuroscience (18 decks)

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