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Fundamentals of neuroscience > Skeletal muscle control (systems) > Flashcards

Skeletal muscle control (systems) Flashcards

1
Q

What are α-motor neurones?

A

They are the motor neurones of the spinal cord

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2
Q

Where are the cell bodies of α-motor neurones found?

A

Cell bodies in the ventral horn

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2
Q

Where do α-motor neurones project to?

A

Out to the skeletal muscles

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3
Q

What do α-motor neurones synapse with?

A

Synapse w muscle fibres = neuromuscular juction

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4
Q

What is a motor unit?

A

Single α motorneurone & all the fibres it innervates

(Made up of α-motoneurones & muscle fibres)

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5
Q

What are skeletal muscles made up of?

A

Bundles of muscle fibres

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6
Q

How many muscle fibres can an α motorneurone synapse w?

A

Each α motorneurone can synapse w multiple muscle fibres

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7
Q

What is focal innervation?

A

Each muscle fibre receives input from a single α motorneurone - this is focal innervation

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8
Q

What is a safety feature muscle have?

A

Nerve terminals always release 8-10x more ACh than necessary so we always get muscle contraction w a single AP

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9
Q

See flashcard on the NMJ (in another deck not sure which one) and ACh reuptake

A

thank u c

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10
Q

What is tubocurarine?

A
  • Nicotinic receptor antagonist
  • Some South American hunters use this to hunt animals
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11
Q

What is smooth contraction?

A
  • Each α-motorneurones innervates muscle fibres that are spread throughout the muscle
  • α-motorneurone fire ascynchronously
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12
Q

What is innervation ratio?

A

No. muscle fibres innervated by each individual α-motorneurone

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13
Q

What is innervation ratio is inversely correlated with?

A

Contractile precision

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14
Q

Give some examples of innervation ratio being inversely correlated w contractile precision:

A

Fingers = very dexterous, 5-15 fibres per α-motorneurone

Abdominal muscles = coarse movements, 200-1500 fibres per α-motorneurone

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15
Q

What are the 2 types of muscle fibres?

A
  • Type I
  • Type II
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16
Q

What are type I muscle fibres AKA?

A

Slow twitch

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17
Q

What are type II muscle fibres AKA

A

Fast twitch

18
Q

What are the the following like for type I muscle fibres:

  • Contraction
  • Force of contraction
  • Resistance to fatigue
A
  • Contraction = slow (0.1s)
  • Force of contraction = low
  • Resistance to fatigue = high
19
Q

What are the the following like for type II muscle fibres:

  • Contraction
  • Force of contraction
  • Resistance to fatigue
A
  • Contraction = fast (0.01s)
  • Force of contraction = high
  • Resistance to fatigue = low
20
Q

What are the the following for type I muscle fibres:

  • Energy source
  • Colour
  • Function
A
  • Energy source = oxidative
  • Colour = red
  • Function = posture
21
Q

What are the the following for type II muscle fibres:

  • Energy source
  • Colour
  • Function
A
  • Energy source = glycolytic
  • Colour = white
  • Function = rapid movements
22
Q

What is an example of a type I muscle fibre?

A

Anti-gravity muscles e.g. abdominal muscles

23
Q

What is an example of a type II muscle fibre?

A

Eye muscles

24
Q

What sort of muscle fibre are muscles made up of?

A

Made up of both type I and II muscle fibres

α-motoneurones only innervate one type of muscle fibre`

25
Q

How do muscle fibre types increase the force of a contraction?

A
  • Generally, slow twitch are recruited first
  • Heavy loads also req fast twitch muscle fibres –> glycolytic fatigue happens quickly
26
Q

How do α-motoneurones increase the forceof contraction?

A

Recruit more α-motoneurones
Inc the AP firing rate of α-motoneurones
- Summation of muscle contractions
- Max summation (tetanus) = 3.5Kg/cm^2 force in all muscles

27
Q

What are the 3 types of ventral horn hormones?

A
  • α-motoneurones
  • Renshaw cells
  • γ-motoneurones
28
Q

What do γ-motoneurones do?

A

Innervate muscle spindles

29
Q

What do α-motoneurones do?

A
  • Innervate muscle fibres
  • Release ACh
  • Cause contraction of muscle fibres via nAChRs
30
Q

What do Renshaw cells do?

A
  • Inhibitory interneurones
  • Release glycine
  • Synapse w α-motoneurones (inhibit their activity)
  • Lateral inhibition = prevents overactivity & enables fine control of movement
  • Target site of tetanus bacteria toxin
31
Q

What are mechanoreceptors?

A

Stretch receptors

32
Q

What are muscle spindles?

A
  • Mechanoreceptors
  • Intrafusal muscle fibres
  • Attached to the extrafusal muscle fibres
  • γ-motoneurones innervate ends of intramural muscles
  • Sensory neurones innervate middle section of intrrafusal muscles
33
Q

What are the types of intrfusal muscles?

A
  • Dynamic nuclear bag fibre
  • Static nuclear bag fibre
  • Nuclear chain fibre
34
Q

What are annulospiral sensory endings also called and what do they do?

A

Ia = absolute stretch & change in stretch

35
Q

What are flower spray sensory endings also called & what do they do?

A

Il = absolute stretch

36
Q

What is the process of the knee jerk reflex?

A

1 - Strike patellar tendon w a hammer

2 - Stretches the muscle spindle in the quad

3 - APs project along Ia afferents to spinal cord

4 - Synapse (excitatory, glutamate) w -motoneurones

37
Q

What is the process of the knee jerk reflex?

A

1 - Strike patellar tendon w a hammer

2 - Stretches the muscle spindle in the quad

3 - APs project along Ia afferents to spinal cord

4 - Synapse (excitatory, glutamate) w α-motoneurones in ventral horn that innervates that quadricep
–> α-motorneurone releases ACh at NMJ causing contraction of quad

5 - Collateral synapse (excitatory, glutamate) w Renshaw cell in ventral horn
—> Renshaw cell (inhibitory, glycine) synapses w α-motorneurone that innervates hamstring
–> Reciprocal inhibition of hamstring

6 - Leg raises

38
Q

What is the gamma (γ) loop?

A

Monitors muscle contraction & corrects when required

39
Q

What are golgi tendon organs?

A
  • Mechanoreceptors
  • Tendons (Between the muscle & bone)
  • Innervated by Ib sensory neurones
  • When the muscle stretches so do the Golgi tendon organs
40
Q

What is the golgi tendon reflex?

A

Protects the muscle from overloading - inverse stretch reflex

41
Q

Summarise γ-motorneurones:

A
  • Muscle spindles
  • Monitor muscle stretch
  • Stretch reflex (activates muscle contraction) γ-loop (monitors & correct contraction)
42
Q

Summarise α-motorneurones:

A
  • Extrafusal msucle fibres
  • Muscle contraction
43
Q

Summarise golgi tendon organ:

A
  • Monitor muscle tendon
  • Golgi tendon organ reflex (protects muscle from overload - inhibits contraction)

Fundamentals of neuroscience (38 decks)

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