The Phisiology Of Skeletal Muscle Flashcards
(46 cards)
1
Q
The Sliding Filament Theory
A
1- Preparing Binding Site
- action potential allows for the sarcoplasm in reticulum to release calcium ions
- ions bind to troponin in which pulls tropomyosin exposing the myosin
2- The Power Stroke
- cross bridge created
- when binded to myosin head it pulls the actin filament towards sarcomere centre
3- The Binding Site
- ATP re energises the myosin head
- myosin filament uncouple from the actin filament
4) The Ratchet Mechanism
- sufficient calcium is needed
- myofibril gets smaller
- h zone disappears
5) Return Of Calcium
- calcium ions return to sarcoplasmic reticulum
- troponin shape changes
2
Q
Actin
A
- the thin protein filament sound in the muscle cells that together with myosin form sarcomeres, the contrachle units of the skeletal muscle
3
Q
Myosin
A
- the thick protein filament that together with actin form sarcomeres the contractile units of the skeletal muscle
4
Q
Troponin
A
- a calcium receptor that sits on the top of troponin
5
Q
Tropomyosin
A
- spirals that wrap around the actin filament which covers the myosin binding site which prevents myosin attachment during relaxed state
6
Q
The structure of the skeletal muscle
A
- the muscle belly is wrapped in a thick tissue that allows for movement of muscles and carries the epimysium
- perimysium surrounds bundles of muscle fibres named fasciculi
- endomysium surrounds each individual fibre
- each of them extend to form tendons
- muscle fibres are made of of hundreds of myofibrils
- these contain actin and myosin which allow for energy production and the control of the movement
7
Q
SFT- Step 1- preparing the binding site
A
- troponin pulls tropomyosin away form the binding site
- sarcoplasmic reticulum releases calcium ions
- troponin and tropomyosin are found on the actin filament
8
Q
SFT- Step 2- Power Stroke
A
- myosin head attaches to actin filament
- myosin head pulls the actin filament towards the centre of the sarcomere
- myosin head is thick
- actin filament is thin
9
Q
SFT- Step 3- binding ATP
A
- ATP releases energy
- energy allows the myosin to pull the actin filament inwards and so shortening the muscle
- how is the ATP binding site exposed for re energising? Myosin filament uncoupled from actin filament allowing ATP to bind onto it- returning the myosin back to re energising state
- H zone gets smaller as the muscle contracts
10
Q
STF- Step 4- ratchet mechanism
A
- myosin detaches from the actin
- sarcomere length gets smaller as well as the the myofibril
- sarcoplasmic reticulum keeps releasing calcium ions and the H zone eventually disappears
11
Q
SFT- Step 5- return of calcium
A
- calcium leave the myosin binding site as their is no actin potential
- calcium ions go to the sarcoplasmic reticulum
- muscles become relaxed
12
Q
Slow Twitch Muscle Fibres (type 1)
A
- they contract more slowly but are highly resistant to fatigue
- favoured by endurance athletes
13
Q
Fast Twitch Muscles Fibres (type 2)
A
- they contract more rapidly generating greater forces but are more liable to fatigue
- favoured by sprinters and power athletes
The 2 types
1) type 2b- fast oxidative glycolytic- they are more resistant to fatigue
2) type 2b- fast twitch glycolytic- greater anaerobic capacity
14
Q
Slow Twitch characteristics
A
Speed of contraction- slow
Force of contraction- low
Resistance to fatigue- very high
Aerobic capacity- very high
Anaerobic capacity- low
Fibre size- small
Mitochondrial density- high
Capillary density- high
Myoglobin content- high
PC store- low
Glycogen store- low
Triglyceride store- high
15
Q
Fast twitch- type 2a characteristics
A
Speed of contraction- fast
Force of contraction- high
Resistance to fatigue- moderate
Aerobic capacity- moderate
Anaerobic capacity- high
Fibre size- large
Mitochondrial density- moderate
Capillary density- moderate
Myoglobin content- moderate
PC store- high
Glycogen store- high
Triglyceride store- moderate
16
Q
Fast twitch- type 2b characteristics
A
Speed of contraction- fast
Force of contraction- highest
Resistance to fatigue- low
Aerobic capacity- low
Anaerobic capacity- high
Fibre size- large
Mitochondrial density- low
Capillary density- low
Myoglobin content- low
PC store- high
Glycogen store- high
Triglyceride store- low
17
Q
Muscle fibre recruitment
A
- each muscle fibre within the muscle belly is supplied by only one motor neuron but can innervate anything from just a few fibres into several hundred
18
Q
Motor Unit
A
- it’s a basic functional unit of skeletal muscle
- it is the motor nerve and group of muscle fibres it controls
- stimulation of one motor neurone causes all the muscle fibres in that motor unit to contract simultaneously
- each individual muscle will be made up of motor units
- the amount of motor units recruited depends on the amount of strength required for a given movement
- greater strength= more motor units
- motor units are usually made up of the same muscle fibre type
19
Q
The All or None Law
A
- muscle fibres within a motor unit contract fully or not at all
- they can not partially contract
- a minimum stimulation is needed for the muscle to contract- if this threshold is reach all will contract
- if it falls short of the threshold then the muscle fibres do not respond and muscular contraction fails to occur
20
Q
Spatial Summation- an increase in responsiveness of a nerve resulting from the additive effect of numerous stimuli
A
- for a muscle to contract the EPSP must be of a certain level of intensity to intimate the sliding filament mechanism
- spatial summation describes the progressive increase in the size of the EPSP as a result of the arrival of a number of impulses at the synaptic cleft if individual fibres
21
Q
With reference to the Sliding Filament Hypothesis, explain the roles of tropomyosin and troponin during muscle contraction. (4 marks)
A
A. Tropomyosin prevents myosin attaching to actin filaments
B. Nerve impulse/electrical impulse/action potential
C. Releases calcium ions (from sarcoplasmic reticulum)
D. (Calcium ions) attach to troponin (on actin filaments)
E. Causing shape of troponin to alter/moves out of the way
F. Tropomyosin binds to actin/winds around/neutralises the troponin
G. Exposes myosin binding site (on actin filament)
H. Allows myosin to bind to actin/cross-bridges formed
22
Q
Explain how actin and myosin filaments in the sarcomere bind together during muscular contraction. (4 marks)
A
A. Filaments unable to bind due to tropomyosin
B. Receipt of nerve impulse/action potential/electrical impulse/wave of
depolarisation
C. Sarcoplasmic reticulum (releases)
D. Calcium (ions released)
E. (Calcium) Attach to troponin (on actin filaments)
F. Causes change of shape of troponin/moves tropomyosin
G. Exposes myosin binding site (on actin filament)/ ATP
H. Cross bridge formation
I. Powerstroke occurs/Ratchet Mechanism/Reduce H zone/z lines
closer together
23
Q
How can a performer vary the strength of muscular contractions to ensure that a skill is completed correctly? (4 marks)
A
A. (Greater the force needed) larger motor units recruited
B. More units recruited
C. Need fast twitch fibres rather than slow twitch fibres
D. Multiple unit summation/spatial summation
E. All or none law/All or nothing law/or explanation
F. Wave summation/frequency of impulse/innervations
G. Motor unit unable to relax/increase the force
H. Tetanus/titanic for powerful contraction
I. Muscle spindles detect changes in muscle length/speed of contraction
J. Send information to brain/CNS
K. Compares information to long term memory to ensure correct force applied/past
Experiences
L. Spatial summation – rotating the frequency of the impulse to motor units to delay fatigue
24
Q
Describe the characteristics of the main muscle fibre type used by elite sprinters. (4 marks)
A
- Fast contracting
- High force production/more powerful
- Low lactate/fatigue tolerance/lactate threshold
- Larger/faster motor neurone
- High sarcoplasmic reticulum development
- More/thicker myosin/larger/bigger diameter
- High PC stores/levels of creatine kinase
- High glycogen stores
- High glycolytic/anaerobic/ATPase enzyme capacity
25
It has been suggested that performers should be screened or tested to establish the proportions of different muscle-fibre types before deciding which activity to concentrate on.
Discuss whether such tests should be the only consideration when choosing an activity. (4 marks)
1. Fast-twitch for speed/anaerobic or strength/slow-twitch for stamina/aerobic;
2. Proportions inherited;
3. Unaffected by training;
4. But many other factors involved in activities e.g. skills/techniques;
5. e.g. Length of levers in sprinting;
6. e.g. VO2 max in stamina-based activities;
7. Two suitable examples of other factors such as fitness, ability,
physique/frame size etc.
26
What do you understand by the term motor unit? (2 marks)
1. Motor neurone and muscle fibres;
2. All fast-twitch or slow-twitch/ homogenous;
3. All or none law.
27
How are motor units involved in the process of spatial summation? (2 marks)
(
a) (iii) 1. (Spatial summation) – Increased strength/more force in muscles;
2. Use bigger/larger motor units;
3. More motor units;
4. Fast-twitch units produce more force than slow-twitch units. 2 marks
(ii) Contraction of different types of muscle fibres involves the use of motor units.
28
What are the characteristics of the type of muscle fibres used to produce maximal contractions? (6 marks)
1. Fast-twitch (glycolytic) fibres/type 2b;
2. Fast motor neurone conduction velocity;
3. Large muscle fibre diameter;
4. More sarcoplasmic reticulum development;
5. Low mitochondrial density;
6. Low capillary density;
7. Low myoglobin content;
8. High PC stores;
9. High glycogen stores;
10. Low triglyceride stores;
11. High myosin ATPase / glycolytic enzyme activity;
12. Low oxidative enzyme activity;
13. Fast contraction / relaxation time;
14. High force production/more powerful;
15. Low fatigue resistance.
29
Explain how the muscle spindle apparatus may be used to adjust the strength of a muscle contraction. (3 marks)
1. Muscle spindles are (stretch) receptors/propriocepters;
2. Force/resistance causes contraction or stretching of a muscle detected by muscle spindles;
3. Results in sensory impulses going to brain/spinal cord/CNS concerning state of contraction;
4. Muscle pre-sets tension based on information held in memory;
5. Gamma bias;
6. Tension adjusted through feedback of information to brain;
7. Gamma neurones activate spindle/intrafusal fibres;
8. Recruit more/bigger motor units;
30
The player in Figure 4 is preparing to catch the ball. Explain the role of muscle spindles in the action of catching the ball. (3 marks)
A. Changes to contraction/lengthening/shortening/stretch in muscle detected by spindles/intrafusal fibres;
B. Sensory nerve impulses to brain/spinal cord/CNS;
C. Body awareness/kinesthesis/position of arms set;
D. Spindles pre-set tension in muscles/muscle loading;
E. Uses memory/experience; (E must be linked to D to credit)
F. Gamma bias (
31
Identify five structural and/or physiological differences between fast and slow-twitch muscle fibres. (5 marks)
1. Fast-twitch have – faster contractions/twitches/faster (myosin) ATPase;
2. More PC;
3. Lower lactate tolerance/fatigue easily;
4. More glycogen;
5. More anaerobic enzymes/greater capacity;
6. Less mitochondria;
7. Less myoglobin;
8. More oxidative enzymes/lower oxidative capacity;
9. More force/strength/powerful contractions;
10. More sarcoplasmic rectilium;
11. Larger motor neurone/(motor) unit/fibre diameter.
32
Suggest three possible physiological causes of muscle fatigue. (3 marks)
1. Lack of PC;
2. Lactate/lactic acid build up/OBLA;
3. Increase acidity/lowering pH/increase H+concentration;
4. Effect on enzymeds/actin/PFK;
5. Lack of calcium ions;
6. Glycogen depletion;
7. Acetylcholine depletion;
8. Dehydration/electrolyte depletion;
9. Muscle wisdom/less impulses sent from brain.
33
With reference to the Sliding Filament Hypothesis, explain the roles of tropomyosin and troponin during muscle contraction. (4 marks)
A. Tropomyosin prevents myosin attaching to actin filaments
B. Nerve impulse/electrical impulse/action potential
C. Releases calcium ions (from sarcoplasmic reticulum)
D. (Calcium ions) attach to troponin (on actin filaments)
E. Causing shape of troponin to alter/moves out of the way
F. Tropomyosin binds to actin/winds around/neutralises the troponin
G. Exposes myosin binding site (on actin filament)
H. Allows myosin to bind to actin/cross-bridges formed
34
Explain how actin and myosin filaments in the sarcomere bind together during muscular contraction. (4 marks)
A. Filaments unable to bind due to tropomyosin
B. Receipt of nerve impulse/action potential/electrical impulse/wave of
depolarisation
C. Sarcoplasmic reticulum (releases)
D. Calcium (ions released)
E. (Calcium) Attach to troponin (on actin filaments)
F. Causes change of shape of troponin/moves tropomyosin
G. Exposes myosin binding site (on actin filament)/ ATP
H. Cross bridge formation
I. Powerstroke occurs/Ratchet Mechanism/Reduce H zone/z lines
closer together
35
How can a performer vary the strength of muscular contractions to ensure that a skill is completed correctly? (4 marks)
A. (Greater the force needed) larger motor units recruited
B. More units recruited
C. Need fast twitch fibres rather than slow twitch fibres
D. Multiple unit summation/spatial summation
E. All or none law/All or nothing law/or explanation
F. Wave summation/frequency of impulse/innervations
G. Motor unit unable to relax/increase the force
H. Tetanus/titanic for powerful contraction
I. Muscle spindles detect changes in muscle length/speed of contraction
J. Send information to brain/CNS
K. Compares information to long term memory to ensure correct force applied/past
Experiences
L. Spatial summation – rotating the frequency of the impulse to motor units to delay fatigue
36
Describe the characteristics of the main muscle fibre type used by elite sprinters. (4 marks)
1. Fast contracting
2. High force production/more powerful
3. Low lactate/fatigue tolerance/lactate threshold
4. Larger/faster motor neurone
5. High sarcoplasmic reticulum development
6. More/thicker myosin/larger/bigger diameter
7. High PC stores/levels of creatine kinase
8. High glycogen stores
9. High glycolytic/anaerobic/ATPase enzyme capacity
37
It has been suggested that performers should be screened or tested to establish the proportions of different muscle-fibre types before deciding which activity to concentrate on.
Discuss whether such tests should be the only consideration when choosing an activity. (4 marks)
1. Fast-twitch for speed/anaerobic or strength/slow-twitch for stamina/aerobic;
2. Proportions inherited;
3. Unaffected by training;
4. But many other factors involved in activities e.g. skills/techniques;
5. e.g. Length of levers in sprinting;
6. e.g. VO2 max in stamina-based activities;
7. Two suitable examples of other factors such as fitness, ability,
physique/frame size etc.
38
What do you understand by the term motor unit? (2 marks)
1. Motor neurone and muscle fibres;
2. All fast-twitch or slow-twitch/ homogenous;
3. All or none law.
39
How are motor units involved in the process of spatial summation? (2 marks)
(
a) (iii) 1. (Spatial summation) – Increased strength/more force in muscles;
2. Use bigger/larger motor units;
3. More motor units;
4. Fast-twitch units produce more force than slow-twitch units. 2 marks
(ii) Contraction of different types of muscle fibres involves the use of motor units.
40
What are the characteristics of the type of muscle fibres used to produce maximal contractions? (6 marks)
1. Fast-twitch (glycolytic) fibres/type 2b;
2. Fast motor neurone conduction velocity;
3. Large muscle fibre diameter;
4. More sarcoplasmic reticulum development;
5. Low mitochondrial density;
6. Low capillary density;
7. Low myoglobin content;
8. High PC stores;
9. High glycogen stores;
10. Low triglyceride stores;
11. High myosin ATPase / glycolytic enzyme activity;
12. Low oxidative enzyme activity;
13. Fast contraction / relaxation time;
14. High force production/more powerful;
15. Low fatigue resistance.
41
Explain how the muscle spindle apparatus may be used to adjust the strength of a muscle contraction. (3 marks)
1. Muscle spindles are (stretch) receptors/propriocepters;
2. Force/resistance causes contraction or stretching of a muscle detected by muscle spindles;
3. Results in sensory impulses going to brain/spinal cord/CNS concerning state of contraction;
4. Muscle pre-sets tension based on information held in memory;
5. Gamma bias;
6. Tension adjusted through feedback of information to brain;
7. Gamma neurones activate spindle/intrafusal fibres;
8. Recruit more/bigger motor units;
42
The player in Figure 4 is preparing to catch the ball. Explain the role of muscle spindles in the action of catching the ball. (3 marks)
A. Changes to contraction/lengthening/shortening/stretch in muscle detected by spindles/intrafusal fibres;
B. Sensory nerve impulses to brain/spinal cord/CNS;
C. Body awareness/kinesthesis/position of arms set;
D. Spindles pre-set tension in muscles/muscle loading;
E. Uses memory/experience; (E must be linked to D to credit)
F. Gamma bias (
43
Identify five structural and/or physiological differences between fast and slow-twitch muscle fibres. (5 marks)
1. Fast-twitch have – faster contractions/twitches/faster (myosin) ATPase;
2. More PC;
3. Lower lactate tolerance/fatigue easily;
4. More glycogen;
5. More anaerobic enzymes/greater capacity;
6. Less mitochondria;
7. Less myoglobin;
8. More oxidative enzymes/lower oxidative capacity;
9. More force/strength/powerful contractions;
10. More sarcoplasmic rectilium;
11. Larger motor neurone/(motor) unit/fibre diameter.
44
Suggest three possible physiological causes of muscle fatigue. (3 marks)
1. Lack of PC;
2. Lactate/lactic acid build up/OBLA;
3. Increase acidity/lowering pH/increase H+concentration;
4. Effect on enzymeds/actin/PFK;
5. Lack of calcium ions;
6. Glycogen depletion;
7. Acetylcholine depletion;
8. Dehydration/electrolyte depletion;
9. Muscle wisdom/less impulses sent from brain.
45
What are the characteristics of the type of muscle fibres used to produce maximal contractions? (6 marks)
1. Fast-twitch (glycolytic) fibres/type 2b;
2. Fast motor neurone conduction velocity;
3. Largemusclefibrediameter;
4. More sarcoplasmic reticulum development;
5. Low mitochondrial density;
6. Low capillary density;
7. Low myoglobin content;
8. High PC stores;
9. High glycogen stores;
10. Low triglyceride stores;
11. High myosin ATPase / glycolytic enzyme activity;
12. Low oxidative enzyme activity;
13. Fast contraction / relaxation time;
14. High force production/more powerful;
15. Low fatigue resistance.
46
Explain how the muscle spindle apparatus may be used to adjust the strength of a muscle contraction. (3 marks)
1. Muscle spindles are (stretch) receptors/propriocepters;
2. Force/resistance causes contraction or stretching of a muscle detected by muscle
spindles;
3. Results in sensory impulses going to brain/spinal cord/CNS concerning state of
contraction;
4. Muscle pre-sets tension based on information held in memory;
5. Gamma bias;
6. Tension adjusted through feedback of information to brain;
7. Gamma neurones activate spindle/intrafusal fibres;
8. Recruit more/bigger motor units;
