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Flashcards in Neuro-Muscular System Deck (60):
1

AUTONOMIC NERVOUS SYSTEM AND NEUROMUSCULAR SYSTEM

The autonomic nervous system (ANS) regulates the function of our internal organs such as the heart and controls some of our skeletal muscles within the body. The movement of muscles during exercise is controlled by the brain via nerves. The neuromuscular system is where the nervous system and the muscles work together to allow movement. The sympathetic and parasympathetic systems transmit information from the brain to the parts of the body that need to adjust what they are doing to prepare for exercise. We know already that the sympathetic system prepares the body for exercise and the parasympathetic has the opposite effect, helping the body systems to slow down during recovery.

2

Why are some people able to run so much faster than others, while some people may run slower but can keep going for hours?

One reason is that there are three different types of muscle fibre and any one individual will have a different mix of these fibre types. As the fibres have distinct characteristics, this will affect performance in certain sporting activities. The mix of fibres in your physiological make-up is genetically determined and largely unaffected by training.

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What are the 3 types of muscle fibre?

- Type 1 - Slow oxidative (SO) ---- SLOW TWITCH ---- - Type 2a - Fast oxidative glycolytic (FOG) - Type 2b - Fast glycolytic (FG) TYPE 2 = Fast twitch

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Type 1 slow oxidative (SO) muscle fibres How do they contract compared to fast twitch?

They contract more slowly.

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Type 1 slow oxidative (SO) muscle fibres Why are they more suited to aerobic work compared to fast twitch fibres? STRUCTURAL

- Mitochondria - Blood capillaries - Myoglobin - Oxidative enzymes

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Type 1 slow oxidative (SO) muscle fibres Aerobic respiration is a slow process, however, which means that.. FUNCTIONAL

- Slow twitch fibres cannot generate as much force as fast twitch fibres, but... -Produce no fatiguing by-products - Can sustain low intensity exercise for prolonged periods of time.

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Individuals with a high proportion of slow twitch fibres are suited to what sports?

-Distance running -Cycling -Swimming -Rowing

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Type 2 fast twitch muscle fibres - Fast twitch fibres are used for what activities? -What sort of power do the contractions have?

- High intensities - Strong force of contraction

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Type 2 fast twitch muscle fibres Why are fast twitch fibres used for activities at high intensities and why do they have much stronger force of contractions?

- The motor neurone that carries the impulse is larger. - There are generally more type 2 muscle fibres attached to each motor neurone - Type 2 fibres are much larger and thicker than other muscle fibres

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Type 2 fast twitch muscle fibres Why are type 2 muscle fibres suited to anaerobic work?

- They have few mitochondria, capillaries, myoglobin & oxidative enzymes - Many glycolytic enzymes

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Fast twitch fibre variation - What are the two types of fast twitch?

2A fast oxidative glycolytic (FOG) muscle fibres 2B fast glycolytic (FG) muscle fibres

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Type 2A fast oxidative glycolytic muscle fibres -How do they contract compared to type 1 fibres and why?

They contract more quickly and so can exert more force than type 1 fibres.

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Type 2A fast oxidative glycolytic muscle fibres - How can they produce energy?

Both aerobically and anaerobically

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Type 2A fast oxidative glycolytic muscle fibres - What energy are they more suited to?

Anaerobic work

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Type 2A fast oxidative glycolytic muscle fibres -Being more suited to anaerobic, what does this mean?

This means that there is a rapid build-up of lactic acid which causes these fibres to fatigue quite quickly. These are, however, more resistant to fatigue than type 2b fibres.

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Type 2A fast oxidative glycolytic muscle fibres What example of sports are there?

-400m -200m swim

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Type 2B fast glycolytic muscle fibres - When do these fibres work and for how long?

- These fibres work at very high intensity for a short period of time

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Type 2B fast glycolytic muscle fibres - How do they accumulate lactic acid?

Quickly and also have high fatigability.

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Type 2B fast glycolytic muscle fibres - Examples of sports?

-100m -Throw -Jump

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Size of fibre - Structural or Functional - Slow twitch (Type 1) - Fast twitch (Type 2a & 2b)

- Structural - Small/thin - Big/thick

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Speed of contraction - Structural or Functional - Slow twitch (Type 1) - Fast twitch (Type 2a & 2b)

-Functional -Slow -Fast

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Force of contraction - Structural or Functional - Slow twitch (Type 1) - Fast twitch (Type 2a & 2b)

-Functional -Small -Large

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Fatigability - Structural or Functional - Slow twitch (Type 1) - Fast twitch (Type 2a & 2b)

-Functional - Low - High

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Mitochondrial density - Structural or Functional - Slow twitch (Type 1) - Fast twitch (Type 2a & 2b)

-Structural -High -Low

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Myoglobin content - Structural or Functional - Slow twitch (Type 1) - Fast twitch (Type 2a & 2b)

-Structural -High -Low

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Capillary density - Structural or Functional - Slow twitch (Type 1) - Fast twitch (Type 2a & 2b)

-Structural -High -Low

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Oxidative enzymes - Structural or Functional - Slow twitch (Type 1) - Fast twitch (Type 2a & 2b)

-Structural -Lots -Little

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Glycolytic Enzymes - Structural or Functional - Slow twitch (Type 1) - Fast twitch (Type 2a & 2b)

-Structural -Little -Lots

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Aerobic/anaerobic - Structural or Functional - Slow twitch (Type 1) - Fast twitch (Type 2a & 2b)

-Functional -Aerobic -Anaerobic

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Fuel stores - Structural or Functional - Slow twitch (Type 1) - Fast twitch (Type 2a & 2b)

-Structural -Fats/carbs -Carbs

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Motor neuron - Structural or Functional - Slow twitch (Type 1) - Fast twitch (Type 2a & 2b)

-Structural -Less -More

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How is fibre type determined?

Genetically

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What is it possible to do through training?

Hypertrophy of the muscle fibre

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What is a motor unit?

A motor unit is the motor neurone and the number of fibres it stimulates.

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As there are so many fibres within each muscle..

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it would be impossible for each one to have its own motor neurone. Similarly, one neurone cannot possibly stimulate all the fibres in one muscle.

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What does the motor neurone do?

Transmits the nerve impulse to the muscle fibre

 

 

Each motor neurone branches off and is connected to a number of fibres within a muscle.

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What is a neuro-muscular junction?

Each motor neurone branches off and is connected to a number of fibres within a muscle. The point where the neurone attaches to the muscle fibre is called the neuro-muscular junction.

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Fibres contained in a single motor unit are...

The fibres contained in a single motor unit are of the same type, i.e. are all either slow or fast twitch, never a mixture of both. Therefore we often refer to slow and fast twitch motor units, not just muscle fibres.

39

The number of fibres in a single motor neurone..

The number of fibres in a single motor unit varies, depending on the precision of movement required and the type of work the muscle performs. For example, the muscles in the quadriceps are thought to contain as many as 2000 fibres per motor unit, as they are required to generate large amounts of power. The muscles in the fingers, which require much less power but more precise movements, may contain as few as 15 muscle fibres in each motor unit.

40

What is the all or nothing law

When a motor unit receives an impulse of sufficient intensity to elicit a response, all the muscle fibres within that motor unit will contract at the same time and to the maximum possible extent. If the impulse is not of sufficient intensity, none of the muscle fibres in the motor unit will contract. This is known as the all or none law.

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How to increase the strength of contraction

This refers to the strength of contraction exerted by a muscle.

When competing in a weight-lifting competition, athletes will need to vary the strength of muscular contraction depending on the weight they are lifting. 

Number, size, type

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How to increase the strength of contraction

Number

The greater the number of motor units that are recruited the stronger the contraction.

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How to increase the strength of contraction

Size

Larger motor units containing more muscle fibres are recruited when a strong contraction is required.

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How to increase the strength of contraction

Type

Fast twitch motor units are recruited when a strong contraction is required, and slow twitch motor units when low force is required.

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Wave summation

The greater the frequency of stimuli, the, greater the tension developed by the muscle.

 

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Explanation of wave summation

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·Repeated activation of a motor neurone stimulating a muscle fibre results in greater force of contraction.

·No time to relax creates a strong muscular contraction.

·The most powerful contraction that can be created is called a tetanic contraction.

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Spatial Summation

When a lower force is required but for a longer period of time, motor units are activated a few at a time.

This means that as one group of motor units relaxes, others are recruited, which spreads the fatigue within the muscle.

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48

How does the all or nothing rules apply to these?

The all or none law applies to all these – if the nerve impulse is strong enough to activate the motor unit, all the fibres will contract.

49

Introduction to PNF

PNF is an advanced stretching technique. It is also considered to be one of the most effective forms of flexibility training for increasing range of motion.

Uses a stretch-contract-stretch technique in which a muscle is lengthened (stretched), then contracted isometrically, then briefly relaxed, then re-lengthened (stretched again) assisted by a partner or machine

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PNF method - Stage 1

-The athlete is passive and a partner assists with the stretch

-Then the partner extends the body limb until the target muscle is stretched to the limit

-And tension is felt

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PNF method - Stage 2

-The athlete then holds the position for a few seconds then

-contracts the stretched muscle isometrically for 5-6 seconds

-The partner must inhibit all movement

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PNF method - Stage 3

-The muscle group is relaxed

-Then immediately and cautiously pushed past its normal range of movement again for about 6 seconds

-Allow 30 seconds recovery before repeating the procedure 2-4 times

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MUSCLE SPINDLES & GOLGI TENDON ORGANS

 

What are they?

Muscle spindles and Golgi tendon organs are types of proprioceptors

Muscle spindles: These detect changes in muscle length; they signal how far and how fast a muscle is being stretched and produce the stretch reflex.

Golgi tendon organs: These are activated when there is tension in a muscle.

 

54

Muscle Spindles

Muscle action is controlled by receptors called muscle spindles which are located in skeletal muscle. These provide sensory information to the brain about changes in muscle length. Muscle spindles are modified muscle fibres which lengthen and shorten as the muscle lengthens and shortens. They send information to the CNS via sensory nerves about how much and how quickly the muscle is changing length. If the muscle needs to respond to the stretch an impulse is sent from the CNS down a motor nerve causing it to contract. It is a reflex action – the brain is not involved.

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55

The stretch reflex

This is a reflex action which protects the muscle against overstretching.

When a muscle is stretched to a point at which it could become damaged, it is detected by the muscle spindles within the muscle.

The muscle spindles send a sensory impulse to the CNS, which causes a reflex shortening of the muscle, thus preventing it from over-stretching – this is the stretch reflex

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56

Golgi tendon organs

-Found between the muscle fibre and tendon

-Detect levels of tension in a muscle

-When a muscle has too much tension

-They send inhibitory signals to the CNS.

-This allows the muscle to relax and lengthen

-This is autogenic inibition

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The role of muscle spindles & GTO

At Stage 1 PNF

-Muscle spindles lengthen as mucle lengthens

-Sensory impulses sent to CNS

 

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The role of muscle spindles & GTO

Stage 2 of PNF

-Muscle spindles shorten slightly which...

-Overides the stretch reflex

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The role of muscle spindles & GTO

Stage 3 of PNF

-GTO detects increased tension in muscle and cause autogenic inhibition.

60

What is the aim of regular PNF training?

To toughen up or inhibit muscle spindles enabling further lengthening of a muscle by overriding the stretch reflex.