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Physiology > Module 4: Lecture 5 > Flashcards

Module 4: Lecture 5 Flashcards

1
Q

What are the 2 ways our motor units be controlled?

A
  1. Changing the number of fibres
  2. By changing the activation of the fibres
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2
Q

what is a motor unit made of?

A
  • one motorneuron: cell body sits in the spinal region with the axon splitting into multiple divisions that will interact with a skeletal muscle fibre
  • all the myofibres it innervates with it
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3
Q

What is the motor unit recruitment talking about?

A

this means all of our muscle fibres within a motor unit will be activated when a motor unit is recruited

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4
Q

True or False
The greater the amount of force needed the more motor units will be recruited

A

True

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5
Q

True or False
A muscle fibre can only have ONE neuromuscular junction and it is only innervated by ONE motor neuron

A

True

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6
Q

From a microscopic view, What colour are your slow and fast twitch muscle fibres?

A

slow twitch = dark stain (type 1)
fast twitch = light stain (type 2)

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7
Q

What do we mean when talking about the “size” of a motor unit?

A

the number of muscle fibres that are innervated with the motor unit

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8
Q

True or False
Very fine motor control movements are going to have very few muscle fibres per motor unit

A

True

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9
Q

What is the asynchronous recruitment of motor units?

A

means depending on the amount of force that needs to be generated, you will first recruit some motor units, and then you can recruit additional motor units as needed

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10
Q

Why do we have the asynchronous recruitment of motor units?

A

to control our motor force and not get tired too easily aka fatigue resistance
- typically we will recruit out type 1 muscle fibres first then out type 2 muscle fibres

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11
Q

What are type 1 muscle fibres?

A
  • slow twitch
  • fatigue resistance
  • don’t produce much force
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12
Q

What are type 2 muscle fibres?

A
  • fast twitch
  • tired easily
  • produces lots of force
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13
Q

How does the CNS know which motor units to recruit?

A

motor units are recruited by size from smallest to largest
- The smallest will be type 1
- The largest will be type 2

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14
Q

What is the Henneman’s size principle?

A

the theory is that the size of the motor unit will dictate the recruitment principle
- smallest to largest

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15
Q

What are the 3 rules for the orderly recruitment of motor units?

A
  1. Minimizes Fatigue (always recruit type 1 first for any given action)
  2. Allows a finer control of muscle forces
  3. Simplifies the control of force
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16
Q

What is our whole muscle tension?

A

number of fibres contracting, whether our motor unit is turned on or off

17
Q

The frequency of motor neuron activation means we are altering what?

A

altering the amount of tension the muscle fibres are generating, aka changing the frequency of action potentials

18
Q

How does changing the frequency of the action potential affect the muscle?

A

this changes the amount of calcium in the muscle and that will adjust how much force those muscle fibres are generating

19
Q

What are the 4 factors that influence the extent to which tension can be developed? (3 of which are muscle characteristics)

A
  1. Frequency of stimulation
  2. Length of the fibre at the onset of contraction
  3. Extent of fatigue
  4. Thickness of the fibre (number of myofibrils/sarcomeres)
20
Q

One action potential leads to how many muscle twitches?

A

1

21
Q

What is twitch summation?

A

when a single muscle twitches can summate on top of another

22
Q

True or False?
The amount of calcium that is released during a single twitch is not sufficient to fully activate all of our thin filaments.

A

True

23
Q

What is the name for when we achieve action potentials so frequently that there is no time for our muscles to relax?

A

tetanus

24
Q

At the tetanus stage, what is occurring?

A
  • all your thin filaments are activated
  • all your cross-bridges are formed
  • the motor units are all generating the maximum amount of force it can
25
Q

What happens when you have the disease of tetanus?

A

these individual’s muscles are going under full muscle contraction
- neurological condition
- lockjaw

26
Q

True or False
The motor neruon goes through refractory periods

A

True

27
Q

The central nervous system can control muscle force through 2 key mechanisms which are?

A
  1. Motor unit recruitment
    - through Henneman’s size principle
  2. Motor unit activation rate
    - fusion of muscle twitches
    - frequency of action potentials

Physiology (27 decks)

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