Physiology of skeletal muscles Flashcards
Name 4 functional characteristics of slow twitch muscle fibres
- slow speed of contraction
- low force of contraction
- high resistance to fatigue
- Very high aerobic capacity
Name 5 structural characteristics of type IIx muscle fibres
- Low mitochondrial density
- Low capillary density
- Low myoglobin content
- Very high glycogen store
- Large motor neuron size
What are 5 structural characteristics of Fast Oxidative glycolytic muscle fibres ?
- Medium mitochondrial density
- Medium Capillary density
- Medium myoglobin content
- High glycogen store
- Medium motor neuron size
What are 4 functional characteristics of fast twitch glycolytic muscle fibres?
- High speed of contraction
- High force of contraction
- Low resistance to fatigue
- High anaerobic capacity
What are 5 structural characteristics of slow twitch oxidative muscle fibres?
- High mitochondrial density
- high capillary density
- High myoglobin content
- Low glycogen store
- Small motor neurone size
Name 4 functional characteristics of fast twitch glycolytic muscle fibres
- Very high speed of contraction
- High force of contraction
- Low resistance to fatigue
- Very high anaerobic capacity
What are the roles of the sympathetic and parasympathetic nervous systems?
- The sympathetic nervous system prepares the body for exercise (increases HR)
- The parasympathetic nervous system helps the body to return to normal after exercise by relaxing high energy functions. (slows HR)
True or False?
We have a set number of muscle fibres in our body
- False
- We have a mix of all 3 but not in equal proportions, it is genetically determined
What types of athlete would have slow twitch muscle fibres?
- Long endurance athletes
- Marathon runners
- Long distance cycling-tour de France
Type IIa Muscle fibres are more common in what athletes?
- Games athletes
- Football
- Basketball
- Rugby
100 + 200m Sprinters, maximal + near maximal lifts would have mainly what muscle fibre types?
- Type IIx/fast twitch glycolytic
What is a motor unit?
- A motor neurone and the muscle fibres it is attached to
True or false?
Only one type of muscle fibre can be found in one particular motor unit
- True!
How does a motor neurone stimulate the muscle fibre?
- action potential travels through the motor neuron
- a nerve impulse is sent
- this stimulates the muscle fibre
What is the all or none law?
- One motor neurone stimulates the muscle fibres, either all of them or none of them contract
Name 2 other parts of the all or none law
- A minimum threshold is needed for the muscle fibres to contract
- If the sequence of impulses is = to or more than the threshold then all muscle fibres in the motor unit will contract.
How can we vary the strength of contractions?
- Recruit different sizes of motor units
- Recruit more/less motor units
- Recruit different muscle fibres (Type I/IIa/IIx)
What is the effect of having a large/small motor unit?
- Big MU=large force of contraction
- Small MU=small force of contraction
What is the effect of recruiting more/less motor units?
- More MU=larger force of contraction
- Less MU=Smaller force of contraction
What muscle fibres cause a small force of contraction?
Slow twitch oxidative muscle fibres
Fast twitch glycolytic muscle fibres cause what force of contraction?
A large force of contraction
What does wave summation mean?
- repeated nerve impulse
- No time to relax
- smooth sustained contraction occurs instead of muscle twitches
What is the definition of spatial summation?
- This is where the strength of the contraction will change depending on number and size of the motor unit
- Delays fatigue as some motor units contract whilst some relax
- determines whether or not there will be an action potential.
What are tetanic contractions?
- Bursts of increasing frequency to the nerve
- Allowing a two minute period between stimuli for muscle recovery
- Causes a sustained muscle contraction
How does spatial summation delay fatigue?
- Some motor units contract whilst some relax
How would wave summation help a gymnast to produce a more powerful contraction?
- Muscle is stimulated before it relaxes
- enables gymnast to apply greater force to adjust the height to match what is needed for her technique
At what rate do type IIa muscle fibres produce ATP
- Produce ATP at a fast rate due to the use of both aerobic and anaerobic systems
What is the process of PNF stretching?
- A muscle group is passively stretched
- They then contract isometrically against resistance while in the stretched position
- It is passively stretched again through the resulting increased range of motion.
What type of contraction occurs during PNF?
- Isometric contraction
What is the contract-relax method?
- The muscle group is passively stretched
- It is then isometrically contracted for around 10 seconds
- Muscle relaxed for appr. 2 secs
- Stretched again for 10 secs
What does CRAC stand for?
- Contract Relax Agonist Contraction
What is the process of CRAC?
- Muscle group is passively stretched
- Isometrically contracted against resistance for around 10 seconds
- Active stretch is applied
What is the difference between a passive and active stretch?
- An active stretch doesn’t require a partner, you are stretching the muscle yourself
- A passive stretch is where an external force is being applied
What is the Golgi tendon organ?
- Monitor information about the tension or force experienced by a muscle and tendon.
During the contraction phase, significant amount of tension occurs within the muscle and tendons. What happens to the GTO?
- The GTO is stimulated
- Counteracting the stretch reflex caused by muscle spindle activation
- This causes an inhibitory reflex
- Relaxation of the muscles being worked on.
How does the GTO enable a larger range of motion.
- Relaxation of the stretched muscle and contraction of its antagonistically paired muscle
- enables the joint to be taken to a greater range of motion
- This leads to improved adaptations in muscle length.
What happens when a high force could lead to injury in either the muscle of tendon?
- When high force could lead to injury in the muscle or tendon, the GTO causes an inhibitory reflex.
What is an inhibitory reflex?
- a relaxation of the whole muscle
Explain the difference between tetanic summation and wave summation (4 marks)
- Tetanic summation allows maximal force to be produced by motor units
- This is because maximal impulses are sent down a nerve.
- In wave summation many impulses are sent down a nerve
- they gradually add together to produce a larger force but it is sub-maximal
Discuss the use of Type 2a Muscle fibre type in a basketball match. (5 Marks)
- Fast speed of contraction,
- Lots of fast movements in match,
- High force of contraction allowing higher jumps and more power
- Medium aerobic capacity.
- Allows muscles to work for the duration of the game is not too long.
Describe a method for creating a larger force of contraction. (2 Marks)
- Tetanic summation
- greatest amount of impulses sent to muscles
- causing them to contract with the largest force possible
- more motor units innovated
Describe the process of post-isometric relaxation
- controlled by Golgi tendon organ
- When muscles are contracted isometrically for a long period muscle inhibition will occur
- This results in the muscle relaxing
