LEWIS: Muscles Flashcards
(74 cards)
0
Q
Sarcolemma is the
A
Plasma membrane
1
Q
Each muscle fibre contains:
A
- myofibrils
- mitochondria
- sarcoplasmic reticulum
- nuclei
2
Q
Sarcoplasmic reticulum is the equivalent to the endoplasmic reticulum of cells. It forms a network of channels - acts as a store of
A
Calcium ions that when released initiate muscle contraction
3
Q
Sarcoplasm is the
A
Liquor interior of a muscle fibre
4
Q
Striated appearance or muscles is caused by alternating
A
Dark and light bands
5
Q
Dark bands are called
A
A bands
6
Q
Light bands are called
A
I bands
7
Q
The I bands are bisected by the
A
Z line
8
Q
The centre of A bands is divided by the
A
H zone
9
Q
The reoccurring unit in a Myofibril is the
A
Sarcomere
10
Q
The sarcomere goes from
A
One Z line to another
11
Q
2 myofilaments:
A
Actin
Myosin
12
Q
Actin filament is the
A
Thin, light band
13
Q
The thin filament of actin extends in each direction from the
A
Z line
14
Q
Myosin filament produces the
A
Dark, thick band
15
Q
Shortening of the sarcomeres in a Myofibril produces the shortening of the Myofibril and in turn, of the
A
Muscle fibre of which it is a part
16
Q
Where the myofilaments do not overlap is known as the
A
H zone
17
Q
Step 1 of muscle contraction:
A
1) nerve impulse arrives at the end of motor neurone
18
Q
Step 2 of muscle contraction:
A
2) acetylcholine is released
19
Q
Step 3 of muscle contraction:
A
-acetylcholine binds to receptors on motor end plates
20
Q
Step 4 of muscle contractions:
A
-sodium ions rush into muscle fibres
21
Q
Step 5 of muscle contractions:
A
Muscle action potential sweeps into T tubules
22
Q
Step 6 of muscle contractions:
A
-sarcoplasmic reticulum releases calcium ions
23
Q
Step 7 of muscle contraction
A
Calcium binds to troponin, causing it to change shape
24
Step 8 of muscle contraction
When calcium binds to troponin, it causes tropomyosin to move and expose myosin binding site
25
Step 9 of muscle contraction
- myosin binds to actin, activating enzyme myosin-ATPase (energy released from ATP breakdown = causes change in shape of myosin head)
- cross bridge formed
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Step 10 of muscle contraction
-Myosin pivots pulling actin filaments (ratchet mechanism/power stroke)
27
Step 11 of muscle contraction:
-myosin releases from actin
28
Step 12 of muscle contraction:
Myosin re-extends into 'ready' position
29
As a muscle contracts:
- Z lines come closer together
- width of the I bands decreases
- width of the H zones decreases
- no change in width of A bands
30
Muscle is stretched:
- width of I bands and H zones increases
| - no change in the width of A bands
31
At rest, thick myosin heads are prevented from attaching to the thin actin filament due to
Tropomyosin
32
muscular contraction is controlled by:
proprioceptors
muscle spindle apparatus
golgi tendon organs
33
proprioceptors are sense organs in the muscles, tendons and joints that
inform the body of the extent of movement that has taken place
34
Muscle spindle apparatus are very sensitive proprioceptors that lie between skeletal muscle fibres and provide information about the
rate of change in muscle length - if muscle is stretched too far they alter tension to shorten muscle, causing a stretch reflex which automatically shortens the muscle
35
Golgi tendon organs are thin pockets of connective tissue that occur where the muscle fibre and tendon meet. They provide information to the CNS concerning the
stretch within the muscle
stretched they trigger the reflex inhibition of the muscle that is contracting and stretching the tendon, and the reflex inhibition of the muscle that is contracting and stretching the tendon, and the reflex contraction of the antagonist
36
3 types of muscle fibre:
type I - slow oxidative
type IIa - fast oxidative glycolytic
type IIb - fast glycolytic
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Skeletal muscles contain all 3 types of muscle fibre but not in equal proportions. the mix is mainly
genetically determined
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Muscle fibres are grouped into motor units and only one type of fibre can be found in
one particular unit
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The relative proportion of each fibre type varies in the same muscles of different people. E.g. an endurance athlete will have a greater proportion of slow twitch fibres in the leg muscles than an elite sprinter who will have
more fast-twitch
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Training is a way the body can produce adaptations to the proportions of muscle fibres:
continuous v weight
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Capillary density:
TYPE I
TYPE IIa
TYPE IIb
high
medium
low
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Aerobic capacity:
TYPE I
TYPE IIa
TYPE IIb
high
medium
low
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Anaerobic capacity:
TYPE I
TYPE IIa
TYPE IIb
Low
medium
high
44
Fatigue levels:
TYPE I
TYPE IIa
TYPE IIb
low
medium
high
45
Myoglobin levels:
TYPE I
TYPE IIa
TYPE IIb
high
medium
low
46
Glycogen levels:
TYPE I
TYPE IIa
TYPE IIb
low
high
high
47
Triglyceride levels:
TYPE I
TYPE IIa
TYPE IIb
high
medium
low
48
Contraction speed:
TYPE I
TYPE IIa
TYPE IIb
slow (10)
fast (50)
fast (50)
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Mitochondrial density:
TYPE I
TYPE IIa
TYPE IIb
high
medium
low
50
A bands =
both actin and myosin
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I bands =
actin only
52
H zones =
myosin only
53
Muscle contracts, Z lines move closer together, the width of the I bands and H zones decreases while the A band
stays the same
54
Slow twitch fibres tend to be smaller in size and produce less overall force than fast-twitch, and they are more energy efficient, producing more force for the same energy input, therefore are well adapted for
prolonged exercise
55
Slow twitch = high endurance levels and are suited to aerobic exercise. Produce ATP primarily from
Aerobic energy pathways
56
fast twitch better suited to anaerobic activity, as they produce their ATP primarily from
anaerobic energy pathways
57
fast twitch are well adapted to short, intense burst of effort. Large diameter as there are more myosin filaments - able to produce more force.
Due to more complex arrangement of sarcoplasmic reticulum, calcium ions can be released and returned to storage more quickly than in slow twitch. Also possess a different myosin-ATPase which releases ATP quicker than than slow twitch.
Fast twitch also have larger stores of
phosphocreatine
58
FOG fibres fatigue easily because of their limited endurance. Used mainly for short, high-intensity endurance events, e.g.
1 mile run/400m swim
59
FG primarily used in low intensity exercise or highly explosive events:
100m sprints/50m swims
60
presence of high proportion of slow-twitch and fast-twitch fibres is not the sole determinant of good performance. likely other factors must influence:
physical - length of lever, VO2 max, physique
| psychological - motivation, commitment, confidence
61
motor neurones leading to skeletal muscles have branches, each of which meets a muscle fibre at a
neuromuscular junction
62
nerve impulses passing down a single motor neurone will thus trigger contraction in all the muscle fibres at which the branches of that neurone end. This minimum unit of contraction is called a
motor unit
63
Each muscle fibre within a motor unit either contracts or does not contract - this is the
all-or-nothing law
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The all or nothing law states that muscle fibres either contract or do not contract. There is no such thing as a
partial contraction
65
If an impulse is equal to or more than the threshold (minimum amount of stimulation required to start a contraction) then the muscle action will
occur
66
If the impulse is less than the threshold then no muscle action will
occur
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Gradation of contraction refers to the strength or force exerted by a muscle and is dependent on:
recruitment
frequency
timing
68
Recruitment: the greater the number of motor units that are recruited, the greater the number of muscle fibres that will contract. This increases the
More motor units also referred to as
Which units we use, depending on whether they are fast or slow twitch will affect the force
force that can be produced
multiple summation
69
Frequency: the greater the frequency of stimuli the greater the tension developed by the muscle.
Stimuli occur very infrequently, the calcium concentration in the sarcomere returns to resting levels before the arrival of the next stimulus.
When the stimuli occur frequently, not all the calcium released in response to the first stimulation is taken back into the sarcoplasmic reticulum, as a result summation occurs - also called
wave summation
70
wave summation, where repeated activation of a motor neurone stimulating a given muscle fibre results in
summation
71
spatial summation is changes in strength of contraction are brought about by altering the
number and size of motor units involved
72
Timing: if all the motor units are stimulated at the same time, then maximum force can be applied. This is referred to as
spatial summation
73
spatial summation, occurs when several impulses from different neurones all arrive at the same time, therefore increasing the
strength exerted by the muscle
