Neuromuscular system Flashcards
(22 cards)
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.
Performers have to improve the capacity of the appropriate muscle fibres for their sport and to recover as quickly as possible following exercise.
Name the muscle fibre type in use during an endurance race and identify the physiological characteristics that allow these muscle fibres to work for an extended period of time.
[Total 3 marks]
Slow twitch fibres / type 1 / slow oxidative fibres
High number of / larger mitochondria
Sub max of 2 marks
High level of myoglobin
Sub max of 2 marks
High capillary density
Sub max of 2 marks
High levels of triglyceride
Sub max of 2 marks
Do not accept ‘red in colour’
Not fat
High levels of oxidative enzymes
Sub max of 2 marks
All gymnastic events require controlled powerful movements.
How can a performer vary the strength of muscular contractions to ensure that a skill is completed correctly?
[Total 4 marks]
(Greater the force needed) larger motor units recruited.
Accept reverse
More units recruited.
Accept reverse
Need fast twitch fibres rather than slow twitch fibres
Multiple unit summation / spatial summation.
These terms must be explained and refer to technical name for first two points.
All or none law / All or nothing law / or explanation.
Allow action potential / threshold is reached, contraction occurs in all of the fibres in the motor unit.
Spatial summation can be credited twice with appropriate explanations.
Wave summation / frequency of impulse / innervations.
Motor unit unable to relax / increase the force.
Tetanus / titanic for powerful contraction.
Muscle spindles detect changes in muscle.
length / speed of contraction.
Send information to brain / CNS.
Compares information to long term memory to ensure correct force applied / past
experiences.
Spatial summation – rotating the frequency of the impulse to motor units to delay
fatigue.
During the race, a swimmer has to dive off the starting blocks as quickly as possible.
Identify the ‘muscle fibre type’ used to complete this action and justify your answer.
[Total 3 marks]
Fast twitch fibres / type 2
First answer only.
Type 2b / fast twitch glycolytic / FTG
B – Not Type 2a.
Fast speed of contraction
Fast twitch oxidative / FOG.
High force of contraction / powerful contraction / strong contraction.
Not characteristics
If both types of fast twitch named, first point only.
A sprinter is driving out of the blocks in a 100 m race.
Analyse how the following factors help the sprinter to make an explosive start:
- Recruitment of muscle fibres
- Newton’s Laws of linear motion [Year 2 content]
[15 marks]
AO1 Knowledge of the recruitment of muscle fibres and Newton’s Laws
* A motor unit consists of a motor neurone and all the muscle fibres it stimulates.
* The ‘All or None Law’ states that if a motor unit receives sufficient stimulation an action potential will be released and all the fibres in that motor unit will contract.
* Spatial summation – the addition of impulses received at the same time, but at different location on the neuron. If, when added together, the impulses are large enough an action potential will be released.
* Wave summation – repeated nerve impulse which does not allow the muscle fibres time to fully relax. This results in a tetanic contraction.
* Tetanic contraction – a smooth sustained muscle contraction. Not a muscle twitch.
* Newton’s first law of linear motion (law of Inertia) states a body will remain in a state of rest or uniform motion until a (large enough) force acts upon it.
* Newton’s second law of linear motion (law of acceleration) states acceleration is directly proportionate to the magnitude of the force produced and is governed by the direction the force is applied/Force = mass x acceleration.
* Newton’s third law of linear motion (law of action/reaction) states that for every action there is an equal and opposite reaction.
AO2 Application of the recruitment of muscle fibres and Newton’s Laws to the sprinter making an explosive start
- Spatial summation will result in recruitment of more motor units/bigger motor units/fast-twitch motor units.
- All movements will involve wave summation/tetanic contractions as they require more than a single muscular twitch.
- (Newton’s 1st Law) The sprinter must produce a large enough muscle contraction/force to overcome their inertia and move out of the blocks.
- (Newton’s 2nd Law) As the mass of the sprinter remains constant, their acceleration is equal to the muscular force they produce.
- The direction of the force exerted by the sprinter into the blocks governs the direction of the sprinter’s acceleration.
- (Newton’s 3rd Law) The internal muscular force produced by the sprinter will be applied to the blocks which will apply an equal and opposite force back onto the sprinter.
AO3 Analysis of how recruitment of muscle fibre types and Newton’s Laws of linear motion help the sprinter to make an explosive start
* The recruitment of more motor units/bigger motor units/fast-twitch motor units will maximise the force produced to overcome inertia.
* It will also increase the acceleration of the sprinter as this is directly proportional to the force produced.
* The larger backwards force being applied to the blocks, will result in a larger forward force being the applied by the blocks to the sprinter.
* These factors will result in the sprinter moving out of the blocks faster, accelerating more quickly towards maximum speed which will give them an advantage over other competitors/help them to run a faster time.
* The sprinter will have to apply the muscular force to the blocks at the correct angle to maximise the start, as too flat and they may fall/too high would increase air resistance or limit horizontal acceleration.
* The tetanic contractions produced as a result of wave summation will result in smooth efficient movement aiding speed production
Passive stretching and isometric muscle contraction are stages in PNF
(Proprioceptive Neuromuscular Facilitation).
Each stage activates different proprioceptors.
For the passive stretching stage:
* name the main proprioceptor involved
* explain the role of that proprioceptor.
[2 marks]
- Muscle spindles. (1)
- Detect the amount of stretch in a muscle / initiate a stretch reflex / cause the muscle to contract / prevent overstretching. (1)
Award zero where main proprioceptor is incorrectly named.
Accept any other explanation of the role of named main proprioceptor during the passive stretch stage of PNF stretching.
Maximum 2 marks
For the isometric muscle contraction stage:
* name the main proprioceptor involved
* explain the role of that proprioceptor.
[2 marks]
- Golgi tendon organs. (1)
Do not accept GTO.
- Detect the amount of tension / cause autogenic inhibition / the muscle to relax / override the stretch reflex. (1)
Award zero where main proprioceptor is
incorrectly named.
Accept any other explanation of the role of named main proprioceptor during the isometric muscle
contraction stage of PNF stretching.
Fast glycolytic (type IIx) and slow twitch (type I) muscle fibres generate ATP in
different ways.
Analyse how differences in ATP generation in these muscle fibre types make them
suitable for two athletics events of your choice.
Refer to the structural and functional characteristics of the muscle fibres in your
answer.
[15 marks]
AO1 Knowledge of type I and type IIx muscle fibres and methods of ATP generation
* Type IIx muscles fibres are known as fast glycolytic muscle fibres.
* They have the following characteristics to aid with ATP generation:
o High PC stores
o High glycogen stores
o High level of ATPase / glycolytic enzymes.
* Fast twitch (type IIx) muscle fibres generate ATP via the ATP-PC and anaerobic glycolytic energy
systems.
* Type I muscle fibres are known as slow oxidative muscle fibres.
* They have the following characteristics to aid with ATP generation:
o High mitochondrial density
o High myoglobin levels
o High triglyceride stores.
- Slow twitch (type I) muscle fibres generate ATP via the aerobic energy system.
Credit any correct knowledge of type I and type IIx muscle fibres even if not linked to ATP generation eg
type IIX have a large muscle fibre diameter.
AO2 Application of the functional characteristics of muscle fibres to methods of ATP generationand named athletic events
Fast twitch (type IIx)
- Used in 100 / 200 / 400m sprints OR any field event.
- As race is completed in less than 3 minutes so ATP can be generated by the ATP-PC and anaerobic glycolytic systems.
- High anaerobic capacity means they produce the highest speed and force of contraction allowing the sprinter to complete the race in the fastest possible time.
Slow twitch (type I)
* Used in anything from 1500m to a marathon.
* As races lasts much longer than 3 minutes so the majority of ATP must be generated by the aerobic energy system.
* High aerobic capacity / low fatiguability allow the runner to maintain a higher average speed resulting in a faster time.
AO3 Analysis of how the differences in ATP generation between fast twitch (type IIx) and slow twitch (type I) muscle fibres make them better suited to different named athletic events
Fast twitch (type IIx)
- High PC stores increase the available fuel for the ATP-PC energy system. This is beneficial for a 200 m sprinter as ATP is resynthesised more quickly allowing the sprinter to maintain a higher speed throughout the race.
- High glycogen stores provide a source of fuel for the anaerobic glycolytic energy system. This allows the 200 m runner to maintain a rapid level of ATP resynthesis even once PC stores have been depleted.
- High levels of ATPase allow type IIx muscle fibres to break down ATP more quickly allowing faster movements such as those required to sprint quickly in the 200 m
Slow twitch (type I)
* High mitochondrial density provides more sites for aerobic ATP resynthesis allowing the marathon runner to maintain higher pace for longer without fatiguing.
- High myoglobin levels will transport and store more oxygen in the muscle. This is required for the complete aerobic breakdown of glucose and fats allowing the marathon runner to resynthesise more ATP without producing lactic acid.
- High triglyceride stores can be used by the marathon runner during lower intensity periods of the race. This will preserve glycogen stores, so they are able to work at higher intensities when required eg hill
climb, sprint finish.
Accept any other appropriate analysis of how the differences in ATP generation between fast glycolytic (type IIx) and slow twitch (type I) muscle fibres make them suitable for two athletics events, with reference to the structural and functional characteristic of the muscle fibres.
Maximum 15 marks
