A & P- Neuromuscular system Flashcards
Which one of the following describes spatial summation?
A
A motor unit being capable of fully contracting or not contracting at all
B
A sustained, smooth muscular contraction
C
Repeated nerve impulses allowing no time for the muscle fibres to relax
D
The addition of impulses received at different places on the neuron
(Total 1 mark)
D – The addition of impulses received at different places on the neuron
Usain Bolt and Mo Farah are both multiple Olympic champions, Usain Bolt in the 100 m and Mo Farah in the 10 000 m.
Analyse how the structures of their predominant muscle fibre types differ, producing functional characteristics that impact on their performance.
[total 15 marks]
AO1 Knowledge of structural characteristics of type I (slow twitch) and type IIx (fast glycolytic) muscle fibre types
Type I (slow twitch)
Size of motor neuron: Small Number of mitochondria: High Capillary density: High Myoglobin content: High ATPase levels: Low
Type IIx (fast glycolytic)
Size of motor neuron: Large Number of mitochondria: Low Capillary density: Low Myoglobin content: Low ATPase levels: High
Type IIa fibre types are not relevant to this question.
AO2 Application of the structural characteristics of muscle fibre types to their functional characteristics and sport/athlete
Mo Farah
* Mo Farah’s predominant muscle fibre type will be type I/slow twitch as 10 000 m is a long-distance running event which lasts over 3 minutes requiring the aerobic energy system.
The structure of these muscle fibres gives them a high aerobic capacity. This is because:
* The high capillary density of type I muscle fibres means they are supplied with large amounts of oxygenated blood.
* Their high myoglobin content means more of this oxygen is pulled into the muscle cell as myoglobin has a higher affinity to oxygen than haemoglobin.
* This extra oxygen can also be turned into energy more quickly in the extra mitochondria in their muscles.
* The ability of Mo Farah’s type I muscle fibres to use oxygen more readily will increase his VO2 max/aerobic power.
Usain Bolt
* Usain Bolt’s predominant muscle fibre type will be type IIx/fast glycolytic.
The structure of these muscle fibres gives them a high anaerobic capacity. This is because:
* Large motor neurone provides great impulse to more muscle fibres resulting in faster, stronger contraction.
* High ATPase levels mean that ATP can be broken down more quickly to produce the energy required for muscle contractions.
* Usain Bolt’s type IIx muscles fibres will improve his speed and power which are vital components in a 100 m sprint.
AO3 Analysis of how their muscle fibre type improves their performance in their sport (must be linked to structural and functional characteristics of correct muscle fibres to be creditworthy).
Mo Farah
* Higher VO2 max/increased lactate threshold will allow Mo Farah to run at a faster speed for a longer period of time without fatiguing.
* This will give him a faster time for the race compared to an athlete with a high percentage of type IIa or type IIx muscle fibres.
* While Farah may be required to sprint at the end of the race, his position before the sprint, determined by his aerobic capacity, is much more important than the speed of his finish in determining success.
Usain Bolt
* The increase in power from type IIx muscle fibres will allow him to drive out of the blocks and accelerate quickly.
* His increased speed will allow him to cover the remaining distance in the race in the fastest time possible.
* As the race is short and quick, aerobic power is not required/fatigability is not a consideration, so muscles do not need these functions.
Accept any other appropriate analysis of how the structure of each athlete’s predominant muscle fibres differ, producing functional characteristics that impact on their performance.
Max 15 marks
State two structural characteristics of fast glycolytic muscle fibres (type IIx).
[total 2 marks]
* Large motor neurone size (1)
* Mitochondrial density is low (1)
* Myoglobin content is low (1)
* Capillary density is low (1)
* High amount of anaerobic enzymes/myosin ATPase (1)
Accept any other relevant structural characteristic of fast glycolytic muscle fibres.
Explain how two functional characteristics of fast glycolytic muscle fibres will support an athlete during a 100 metre race.
[total 2 marks]
* Speed of conduction/contraction, eg will allow the athlete to generate a fast start (1)
* High levels of force generated, eg will allow the athlete to push out against the blocks at the start of the race with more force/will allow the athlete to increase maximal speed by applying a greater force to the ground or blocks (1)
* High anaerobic capacity, eg will allow the athlete to maintain force production throughout the race to achieve maximal speed/maintain momentum throughout the 100 metres (1)
* High glycolytic enzyme activity, eg will support quicker/prolonged anaerobic ATP resynthesis/production during the race/allowing the athlete to maintain momentum at higher intensities during the race (1)
Candidates must both state a functional characteristic and how it will support an athlete during a 100 metre race.
Accept any other appropriate explanation for how functional characteristics of fast glycolytic muscle fibres will support an athlete during a 100 metre race.
Which type of summation is shown in the graph below?
A
Spatial
B
Tetanic
C
Wave
C
Explain the role of muscle spindles and Golgi tendon organs in proprioceptive neuromuscular facilitation (PNF).
[Total 4 marks]
Suggest how PNF could improve the performance of the hurdler.
[Total 2 marks]
(a) [AO1 = 4]
Sub-max 3 The muscle spindles:
* Detect an increase in muscle length / how far / fast a muscle is stretched (1)
* Send a message to the nervous system (1)
* During PNF the muscle spindles will initiate a stretch reflex / muscle contraction (1)
* This can prevent over stretching (1)
Sub-max 3 Golgi-tendon organs:
* Detect increased tension in a muscle (1)
* Send inhibitory signals / autogenic inhibition / override stretch reflex (1)
* Cause muscle to relax (1)
Accept any other appropriate explanation of the role of muscle spindles and Golgi tendon organs in proprioceptive neuromuscular facilitation (PNF).
(b) [AO3 = 2]
* The hurdlers improved range of movement / flexibility would allow them to clear the hurdles with more ease (1)
* The hurdlers increased range of motion / flexibility would allow them to improve stride length, generating more power / velocity (1)
* The hurdlers increased range of motion / flexibility would support the hurdler to generate a more fluid / efficient stride pattern (1)
* PNF may help to minimise the risk of injury, allowing them to continue training and performing (1)
Do not credit jumping higher.
Accept any other appropriate suggestions for how PNF stretching could improve the performance of the 110m hurdler.
Proprioceptive Neuromuscular Facilitation (PNF) is a form of stretching that can increase flexibility.
Explain the role of golgi tendon organs during PNF.
[Total 2 marks]
Golgi-tendon organs detect the tension in the muscle (created during the isometric contraction Phase) (1).
Golgi-tendon organs send inhibitory signals / autogenic inhibition (1).
Delays the stretch reflex (1).
Allowing for greater range of movement (1).
In the diagram below, the main muscle fibre type used for a powerful forehand stroke is fast glycolytic (type IIx).
State three characteristics of this muscle fibre type.
[Total 3 marks]
* Large motor neurone size
* Large muscle fibre diameter
* More sarcoplasmic reticulum development
* High PC stores
* High glycogen stores
* Low mitochondrial density
* Low myoglobin content
* Low capillary density
* High myosin ATPase / glycolytic enzyme activity
* High fatigability / low aerobic capacity / high anaerobic capacity
* High force production / speed of contraction
* White in colour.
Accept other appropriate characteristics of fast twitch glycolytic muscle fibres (type IIx).
It is important for sprinters to push off the blocks effectively to achieve a fast start.
Using Newton’s first and second laws of linear motion and knowledge of the neuromuscular system, analyse how a sprinter is able to achieve a fast start.
(Total 8 marks)
AO1 – Knowledge of Newton’s first and second laws of linear motion and the neuromuscular system
Newton’s first and second laws – Eg First law is the law of inertia. Inertia is a body’s reluctance to change its state of motion. A force is required to overcome inertia. Second law is the law of acceleration, the rate of change of momentum of an object is directly proportional to the force causing the change. Any change in momentum takes place in the direction the force was applied.
Force = mass × acceleration
Neuromuscular system – Eg three muscle fibre types, type I, type Ia, type IIx. Muscle contraction brought about by the recruitment of muscle fibres. Spatial summation is when the strength of a contraction changes by altering the number of size of motor units. Wave summation is where there is a repeated nerve impulse with no time to relax so a smooth, sustained contraction occurs. This is a tetanic contraction. Muscle fibres form a motor unit (with motor nerve), each muscle fibre in the unit contracting or relaxing at the same time. This is according to the all-or-none law. There are different sizes of motor unit.
AO2 – Application of Newton’s first and second law and the neuromuscular system to a sprinter
Eg The sprinters current state of inertia is stationary; to alter this state of inertia the sprinter needs to apply a muscular force by contracting his leg muscles in order to overcome his inertia so that he can leave the blocks, moving from a stationary position to begin to run.
By varying the force of his muscles’ contraction and the number of motor units recruited the sprinter can cause a change in momentum from stationary to moving. The sprinter applies a force against the blocks and then the ground to generate the required momentum to move forward down the track.
It would be beneficial to the sprinter to have a high percentage of fast twitch fibres type IIx. The sprinter will recruit large, fast twitch motor units in the leg muscles to generate the force required to overcome inertia, the sprinter will use spatial summation, varying the number of motor units recruited throughout the muscle to allow the fibres in each unit to relax whilst others are contracting to provide the necessary force.
AO3 – Analysis / Evaluation of how the sprinter is able to achieve a fast start
Eg The greater the muscular force that the sprinter can apply against the blocks, the more readily the body will alter its state of inertia, allowing the sprinter to move more quickly out of the blocks. By varying the force of his muscles’ contraction, the greater the force he generates, the greater the acceleration away from the blocks, giving him a better start than his competitors.
If the sprinter increases the frequency of stimulation of the muscle fibres in the motor unit such that the next impulse reaches the muscle before it has completely relaxed from the previous the resulting force is greater, hence the sprinter may use wave summation to increase the force of the muscle contraction further, generating a greater force and therefore greater acceleration according to Newton’s second law.
Accept other appropriate analysis of Newton’s first and second laws of linear motion and the neuromuscular system in enabling a sprinter to achieve a fast start.
Max 8 marks
Which of these are characteristics of a type I muscle fibre?
A
High resistance to fatigue and high numbers of mitochondria
B
Large motor neuron size and large capillary density
C
Large muscle fibre diameter and high myoglobin count
D
Low phosphocreatine stores and low glycogen content
A
Muscle spindles are proprioceptors located between the muscle fibres.
Outline the role of muscle spindles.
[Total 2 marks]
- Detect change in muscle length/tension/stretch (1)
- Prevent overstretching (1)
- By initiating the stretch reflex (1)
Explain how wave summation allows a gymnast to gain the required height in a floor routine.
[Total 3 marks]
Wave summation will allow the gymnast to produce a more powerful contraction (1)
because the muscle is stimulated again before it is relaxed (1)
therefore the gymnast will be able to apply greater force to adjust the height achieved to match the requirements of the technique performed (1).
Accept other appropriate explanations of how wave summation allows a gymnast to gain the required height. Answers must relate to a floor routine.
(a) Fast twitch glycolytic muscle fibres (type IIx) are used to produce powerful contractions.
Identify two characteristics of fast twitch glycolytic muscle fibres (type IIx).
(2)
(b) Explain how the characteristics of fast twitch glycolytic muscle fibres (type IIx) you identified in part (a) are suited to producing ATP anaerobically during powerful contractions.
(2)
(Total 4 marks)
(a) Award one mark for each of the following points.
- Fast motor neurone conduction velocity (1).
- Large muscle fibre diameter (1).
- More sarcoplasmic reticulum development (1).
- High PC stores (1).
- High glycogen stores (1).
- High myosin ATPase/glycolytic enzyme activity (1).
Do not accept produce powerful contraction (in the stem).
Accept other appropriate characteristics of fast twitch glycolytic muscle fibres (type IIx).
Max 2 marks
[AO2 = 2]
(b) Award one mark for each of the following points.
- High PC stores – increased energy source for ATP production via the ATP-PC system (1).
- High glycogen stores – increased energy source for ATP production via the lactate anaerobic system (1).
- High myosin ATPase activity – increased enzyme activity for ATP production within the ATP-PC system (1).
- High glycolytic enzyme activity – increased enzyme activity or ATP production within the lactate anaerobic system (1).
Accept other appropriate explanations as to how the characteristics of fast twitch glycolytic muscle fibres (type IIx) are suited to producing ATP anaerobically during powerful contractions.
Gymnasts have to change the position of their body when performing a somersault during a gymnastic floor routine.
Name the muscle fibre type predominantly used by a gymnast during a floor routine and state the functional characteristics that allow these muscles to produce this type of movement.
[Total 3 marks]
A Fast twitch fibres/type 2/Type2a/Fast oxidative glycolytic/ FOG/Type 2b/fast twitch glycolytic/FTG
B Fast speed of contraction
C High force of contraction/powerful contraction/ strong contraction
D Type2a/Fast oxidative glycolytic/FOG – some capacity to resist fatigue
specific fibre type must be named
Andy Murray won the 2013 Wimbledon Men’s Tennis Final. During the match he completed a variety of strokes and a series of rallies, which varied in length.
Outline how the force of muscle contraction can be varied to ensure that skills are executed correctly.
(Total 5 marks)
A Size of motor units recruited / larger for greater contraction / smaller for less powerful.
B Multiple unit summation.
C Number of units recruited / more or less.
D Type of muscle fibre size determines force of contraction / fast twitch fibres rather than slow twitch fibres for more powerful contractions.
E All or none law / All or nothing law / or explanation / action potential or threshold is reached / contraction occurs in all of the fibres in the motor unit.
F Wave summation.
G Frequency of impulse / innervations.
H Motor unit (muscle) unable to relax / increase the force.
I Tetanus / tetanic for powerful contraction.
J Muscle spindles detect changes in muscle length / speed of contraction.
K Send information to brain / CNS.
L Compares information to long term memory to ensure correct force applied / past experiences.
M Spatial summation.
N Rotating the frequency of the impulse to motor units to delay fatigue / some work while others rest or equiv.
Muscle contraction answer does not have to specify increase or decrease in force applied.
