sliding filament theory Flashcards
1
Q
The sarcomere is the _______ ________ unit of the myofibril.
A
basic functional
1
Q
In the muscle fiber, what defines the sarcomere?
A
the space from one Z disk to another Z disk
2
Q
what is a myofibril?
A
a rod-like unit within a muscle fiberthat is made up of myofilaments
3
Q
are proteins elastic?
A
yes
4
Q
What are myofilaments made up of?
A
thick filaments - myosin
thin filaments - actin
These are proteins
5
Q
When the myofilaments are triggered by calcium release, what happens?
A
they slide over each other to contract or extend
6
Q
What is the I-band made up of? what is it dissected by?
A
thin actin filaments
the Z- line
7
Q
What is the Z-line?
A
a dense protein disk that defines the sarcomere borders
8
Q
What does the Z-line provide?
A
anchorage for contraction and recoil
9
Q
Where is the M-line located?
A
in the middle of the thick myosin filaments
10
Q
In which region is the H-zone?
A
the region in the centre of each A-band
11
Q
What type of filaments is the A-band made up of?
A
mainly thick filaments and partially overlapping thin filaments
12
Q
During contraction, the ______ ______ will pull the _____ ________ closer to one another.
A
myosin (thick filament) heads
actin (thin) filaments
13
Q
During contraction, the _ disks come closer to one another.
A
Z
14
Q
During contraction, the I-bands ______
A
shrink
15
Q
During contraction, the ______ __________ slide over one another.
A
actin filaments
16
Q
Does the A band change length during contraction?
A
no
17
Q
What are the 4 steps of sliding filament theory?
A
- muscle activation
- muscle contraction
- recharging
- relaxation
18
Q
What happens during muscle activation? (2)
A
- The motor nerve stimulates a motor impulse to pass down a neuron to the neuromuscular junction
- The motor impulse stimulates the sarcoplasmic reticulum to release calcium into muscle cells.
19
Q
What happens during muscle contraction? (2)
A
- calcium floods into the muscle cell and it binds with triponin, allowing actin and myosin to bind
- the myosin and actin cross-bridges bind and contract using ATP. This is called a power stroke.
20
Q
What happens during recharging? (1)
A
ATP is resynthesized which allows actin and myosin to maintain their strong binding state.
21
Q
What happens during relaxation? (3)
A
- the stimulation of the nerve stops
- Calcium is then pumped back into the sarcoplasmic reticulum which breaks the link between actin and myosin
- myosin and actin return to their unbound state causing the muscle to relax.
22
Q
When does failure happen?
A
when ATP isnt available
23
Q
what is ATP?
A
adesonine triphosphate, the chemical that fuels muscle contraction.
24
What is the region in which sliding filament contraction occurs?
the sarcomere
25
During contraction, ________ myofilaments rachet over ______ filaments, contracting the ___________.
myosin
actin
sarcomere
26
Within the __________, key regions known as the _ band and_ zone compress and expand to facilitate this process
sarcomere
I
H
27
do myofilaments themselve expand or contract?
no
28
What is the name of the mineral (1) and molecule (2) that are crucial during this process?
calcium
ATP
29
What are the names of the regulatory proteins that aid the formation and release of cross-bridges?
tropomyosin (binding)
troponin (release)
30
There are also structural _________ which maintain _________ and __________ of myofibrils.
proteins
stability
elasticity
31
The 5 structural proteins that mainatain myofibrils are called:
tintin
alpha actinin
myomesin
nebulin
dystrophin
32
1. At the neuromuscular junction, ________ ________ is recieved at the __________ _____
action potential
synaptic bulb
33
2. At the neuromuscular junction, once the action potential is recieved, ________ ______ _______ _________ open. Then, _________ ____ diffuse into the terminal
voltage gated calcium channels open
calcium ions
34
3. At the neuromuscular junction, Once calcium ions are diffused into the terminal, this causes ________ __________ to release _______________ via ______________.
synaptic vesticles
acetylcholine
exocytosis
35
4.Once released, ___________ defuses across the ___________ ______ and binds to _____________ _______, which contain _____-______ ________ ________.
acetylcholine
synaptic cleft
acetylcholine receptors
ligand-gated cation channels
36
5. The ______ ______ _______ ________ open.
ligand-gated cation channels
37
6. Once the channels are open, ________ ____ enter the ________ ______ and _________ ____ exit the _________ ______.
sodium ions
Muscle fiber
potassium ions
muscle fiber
38
6 (cont). The greater inward flux of __________ ____ relative to the outward flux of __________ ____ causes the _________ ______ to become _____ ________.
sodium ions
potassium ions
membrane potential
less negative
39
7. Once the ________ ______ reaches a _________ ______, an ________ ______ propagates along the __________
membrane potential
threshold value
action potential
sarcolemma
40
When in the process does neurotransmission to a muscle fiber cease?
when acetylcholine is removed from the synaptic cleft
41
What are the two ways acetylcholine is removed from the synaptic cleft?
1. Acetylcholine diffuses away from the synapse
2. Acetylcholine is broken down by the enzyme acetylcholinesterase into acetic acid and choline, the choline is then transported into the axon terminal for resynthesis of acetylcholine
42
What are the 4 things that determine the degree of muscle contraction?
1. number of muscle fibres innervated by somatic neuron (motor unit)
2. Frequency of stimulation (number of impulses per second)
3. the size of the muscle fibres
4. the ability of the muscle to form cross bridges
43
at death, when breathing and circulation stop, ________ _____ lack _______ and therefore cannot use ________ __________ to efficiently produce ___.
muscle cells
oxygen
aerobic respiration
ATP
44
At death, after _______ respiration stops, respiration continues ___________ at first, but the muscle cells eventually become so short on ____ that the _______ and ______ filaments cannot release from the _________ ______ and the _________ _____ cannot be pumped back out of the muscle cell.
aerobic
anaerobically
ATP
myosin
actin
contracted state
calcium ions
45
At death, when unable to release from contraction, what happens to the muscles in the body?
they all remain tense and cause rigor mortis
46
What is the arrangement of a small motor unit?
a single motor neuron supplies a small number muscle fibers in a muscle
47
What do small motor units allow the body to do? Give an example.
they permit very fine motor control of the muscle, such as the extraocular muscles of the eye
48
What is the arrangement of a large motor unit?
a single motor neuron supplies a large number of muscle fibres in a muscle
49
What do large motor units allow the body to do? give an example.
allow the body to perform gross movements such as extending the knee joint
50
In large motor units, how are the axons split?
the axon splits into thousands of branches supplying thousands of muscle fibers in a muscle
51
What are the two things that make up a motor unit?
the somatic motor neuron and the muscle fibres it innervates
52
Increased _____ and __________ of a muscle requires an increased number of motor units. For smoothness of movement, timing of ________ of the _____ ____ is important.
force
manipulation
recruitment
motor unit
53
What are twitch contractions?
a fast, brief contraction of a muscle following a single stimulus
54
What influences whether a twitch contraction is going to be strong or weak?
the number of motor units recruited
55
What can the tension produced by a single twitch be measured by? What does it specifically measure
a myogram
the amount of tension produced over time
56
How many phases does each twitch undergo?
three
57
What are the three phases of a muscle twitch?
the latent period
the contraction period
the relaxation period
58
in twitch phases, During the latent period, ______ ________ is being _________ along the _________, and ________ ____ are released from the ________ ______. However, contraction has not occurred yet.
action potential
propogated
sarcolemma
caclium ions
sarcoplasmic reticulum
59
In the twitch phases, in the contraction phase, ________ ____ in the _________ have bound to _______, ____________ has shifted away from ______ _______ ______, and _______ _______ have formed.
calcium ions
sarcoplasm
troponin
tropomyosin
active binding sites
cross bridges
60
(cont) In twitch phases, In the contraction phase the _________ are actively _________ to the point of ______ _______.
sarcomeres
shortening
peak tension
61
In twitch phases, in the relaxation phase, _________ decreases as contraction ______. _________ ____ are pumped out of the __________ back into the ____________ ______ and _____ ________ _______ stops. This returns the _______ ____ to its resting state.
tension
stops
calcium ions
sarcoplasm
sarcoplasmic reticulum
cross bridge cycling stops
muscle fiber
62
Does a single twitch produce any significant muscle activity in a living body?
no
63
What is needed to produce a muscle contraction that can produce work?
a series of action potentials to the muscle fibers
64
Normal muscle contraction is more _______ and it can be modified by ______ from the ________ _____ to produce varying amounts of _______. This is called _______ _____ ________.
sustained
input
nervous system
force
Graded muscle response
65
What are the two factors that affect the tension produced in skeletal muscle?
1. the frequency of action potentials or nerve impulses from a motor neuron
2. the number of motor neurons transmitting action potential
66
If a fiber is stimulated whilst a previous twitch is still occurring, what happens to the second twitch? What is this response called?
it will be stronger
wave summation
67
wave summation occurs because the _________ _________ _____ effects of motor neuron signalling is summed or added together
excitation contraction coupling
68
At the molecular level, summation occurs because the _______ _______ triggers the release of more ________ ____. These become available to activate additional _________ while the muscle is still contracting from the first stimuli.
second stimulus
calcium ions
sarcomeres
69
Summation results in ________ contraction of the ______ ____.
greater
motor unit
70
If the frequency of ________ _______ signaling increases, ___________ and subsequent muscle _________ in the motor unit continues to rise until it reaches a peak point. The tension at this point is about _______ to ______ times greater than the tension of a _______ _______. This state is referred to as ____________/________ _________.
motor neuron
summation
tension
three
four
single twitch
incomplete/unfused tetanus
71
During incomplete tetanus, the muscle goes through ______ cycles of __________ with a short _________ _______ for each.
quick
contraction
relaxation phase
72
In complete tetanus, the ___________ frequency is so high that the __________ phase dissapears completely. The ________ become _________.
stimulus
relaxation
contractions
continuous.
73
During complete tetanus the ____________ of calcium ions in the __________ allows virtually all of the ___________ to form ______ ________ and shorten. This allows the contraction to continue ___________.
concentration
sarcoplasm
sarcomeres
cross bridges
uninterrupted
74
What marks the latent period?
the time between the stimulation of the muscle fibre and the contraction
75
what marks the contraction period?
crossbridge formation
76
What marks the relaxation period?
When peak tension is developed and stimulation is removed i.e release of crossbridges
77
skeletal muscles can be classified as _______ twitch or _______ twitch muscle fibres.
slow
fast
78
What is muscle tone?
the continuous and passive partial contraction of muscles
79
What kind of respiration do slow twitch fibers depend on?
aerobic
80
is the ATP regeneration (for crossbridge formation) faster or slower in slow twitch fibres?
slower
81
Are slow twitch fibres fatigue resistant?
yes
82
What kind of activities are slow twitch fibres helpful for?
sustained muscle contraction
endurance activities
83
Give an example of a slow twitch muscle?
gluteals
84
What kind of respiration do fast twitch A fibres depend on?
anaerobic and aerobic
85
How much faster are fast twitch A fibres that slow twitch fibres?
2-3 times faster
86
Are fast twitch A fibres able to regenerate ATP faster or slower?
faster
87
Fast twitch A fibres have a ______ blood vessel count.
high
88
Give an example where fast twitch A fibres are useful.
short period of intense activities eg throwing a javelin or strength training
89
What kind of respiration do fast twitch B fibres depend on?
anaerobic
90
How much faster are fast twitch B fibres than slow twitch fibres?
2 - 3 times
91
Are fast twitch B fibres able to regenerate ATP fast?
yes
92
Do fast twitch B fibres have a low or high amount of blood vessels?
low
93
How do fast twitch B fibres get ATP?
glycogen
94
Do fast twitch B fibres fatigue quickly?
yes
95
Give an example of exercise that fast twitch B fibres help with.
sprinting
96
When muscles fatigue its because there is no _______ or _______ to generate ____ fast enough. _____________ molecules bind to _________ which would otherwise be involved in the stimulation of a new contraction. _________ acid build up decreases __ and therefore inhibits ___________.
oxygen
glycogen
ATP
phosphate
calcium
lactic
PH
contraction
97
What is the agonist?
the prime mover, a muscle whose contraction moves a part of the body directly
98
what is the antagonist?
the muscle that relaxes when the agonist contracts
99
What is the synergist?
the muscles that help to create the movement
100
what is the fixator?
the muscle that stabilises the origin of the agonist and the joint that origin spans
101
what are the two types of isotonic muscle contraction and the other type of muscle contraction/
concentric
eccentric
isometric
102
What does the length tension relationship of muscle describe?
the amount of tension that is produced by a muscle as a feature of its length
