sliding filament theory Flashcards
The sarcomere is the _______ ________ unit of the myofibril.
basic functional
In the muscle fiber, what defines the sarcomere?
the space from one Z disk to another Z disk
what is a myofibril?
a rod-like unit within a muscle fiberthat is made up of myofilaments
are proteins elastic?
yes
What are myofilaments made up of?
thick filaments - myosin
thin filaments - actin
These are proteins
When the myofilaments are triggered by calcium release, what happens?
they slide over each other to contract or extend
What is the I-band made up of? what is it dissected by?
thin actin filaments
the Z- line
What is the Z-line?
a dense protein disk that defines the sarcomere borders
What does the Z-line provide?
anchorage for contraction and recoil
Where is the M-line located?
in the middle of the thick myosin filaments
In which region is the H-zone?
the region in the centre of each A-band
What type of filaments is the A-band made up of?
mainly thick filaments and partially overlapping thin filaments
During contraction, the ______ ______ will pull the _____ ________ closer to one another.
myosin (thick filament) heads
actin (thin) filaments
During contraction, the _ disks come closer to one another.
Z
During contraction, the I-bands ______
shrink
During contraction, the ______ __________ slide over one another.
actin filaments
Does the A band change length during contraction?
no
What are the 4 steps of sliding filament theory?
- muscle activation
- muscle contraction
- recharging
- relaxation
What happens during muscle activation? (2)
- 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.
What happens during muscle contraction? (2)
- 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.
What happens during recharging? (1)
ATP is resynthesized which allows actin and myosin to maintain their strong binding state.
What happens during relaxation? (3)
- 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.
When does failure happen?
when ATP isnt available
what is ATP?
adesonine triphosphate, the chemical that fuels muscle contraction.
What is the region in which sliding filament contraction occurs?
the sarcomere
During contraction, ________ myofilaments rachet over ______ filaments, contracting the ___________.
myosin
actin
sarcomere
Within the __________, key regions known as the _ band and_ zone compress and expand to facilitate this process
sarcomere
I
H
do myofilaments themselve expand or contract?
no
What is the name of the mineral (1) and molecule (2) that are crucial during this process?
calcium
ATP
What are the names of the regulatory proteins that aid the formation and release of cross-bridges?
tropomyosin (binding)
troponin (release)
There are also structural _________ which maintain _________ and __________ of myofibrils.
proteins
stability
elasticity
The 5 structural proteins that mainatain myofibrils are called:
tintin
alpha actinin
myomesin
nebulin
dystrophin
- At the neuromuscular junction, ________ ________ is recieved at the __________ _____
action potential
synaptic bulb
- At the neuromuscular junction, once the action potential is recieved, ________ ______ _______ _________ open. Then, _________ ____ diffuse into the terminal
voltage gated calcium channels open
calcium ions
- At the neuromuscular junction, Once calcium ions are diffused into the terminal, this causes ________ __________ to release _______________ via ______________.
synaptic vesticles
acetylcholine
exocytosis
4.Once released, ___________ defuses across the ___________ ______ and binds to _____________ _______, which contain _____-______ ________ ________.
acetylcholine
synaptic cleft
acetylcholine receptors
ligand-gated cation channels
- The ______ ______ _______ ________ open.
ligand-gated cation channels
- Once the channels are open, ________ ____ enter the ________ ______ and _________ ____ exit the _________ ______.
sodium ions
Muscle fiber
potassium ions
muscle fiber
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
- Once the ________ ______ reaches a _________ ______, an ________ ______ propagates along the __________
membrane potential
threshold value
action potential
sarcolemma
When in the process does neurotransmission to a muscle fiber cease?
when acetylcholine is removed from the synaptic cleft
What are the two ways acetylcholine is removed from the synaptic cleft?
- Acetylcholine diffuses away from the synapse
- 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
What are the 4 things that determine the degree of muscle contraction?
- number of muscle fibres innervated by somatic neuron (motor unit)
- Frequency of stimulation (number of impulses per second)
- the size of the muscle fibres
- the ability of the muscle to form cross bridges
at death, when breathing and circulation stop, ________ _____ lack _______ and therefore cannot use ________ __________ to efficiently produce ___.
muscle cells
oxygen
aerobic respiration
ATP
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
At death, when unable to release from contraction, what happens to the muscles in the body?
they all remain tense and cause rigor mortis
What is the arrangement of a small motor unit?
a single motor neuron supplies a small number muscle fibers in a muscle
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
What is the arrangement of a large motor unit?
a single motor neuron supplies a large number of muscle fibres in a muscle
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
In large motor units, how are the axons split?
the axon splits into thousands of branches supplying thousands of muscle fibers in a muscle
What are the two things that make up a motor unit?
the somatic motor neuron and the muscle fibres it innervates
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
What are twitch contractions?
a fast, brief contraction of a muscle following a single stimulus
What influences whether a twitch contraction is going to be strong or weak?
the number of motor units recruited
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
How many phases does each twitch undergo?
three
What are the three phases of a muscle twitch?
the latent period
the contraction period
the relaxation period
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
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
(cont) In twitch phases, In the contraction phase the _________ are actively _________ to the point of ______ _______.
sarcomeres
shortening
peak tension
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
Does a single twitch produce any significant muscle activity in a living body?
no
What is needed to produce a muscle contraction that can produce work?
a series of action potentials to the muscle fibers
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
What are the two factors that affect the tension produced in skeletal muscle?
- the frequency of action potentials or nerve impulses from a motor neuron
- the number of motor neurons transmitting action potential
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
wave summation occurs because the _________ _________ _____ effects of motor neuron signalling is summed or added together
excitation contraction coupling
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
Summation results in ________ contraction of the ______ ____.
greater
motor unit
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
During incomplete tetanus, the muscle goes through ______ cycles of __________ with a short _________ _______ for each.
quick
contraction
relaxation phase
In complete tetanus, the ___________ frequency is so high that the __________ phase dissapears completely. The ________ become _________.
stimulus
relaxation
contractions
continuous.
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
What marks the latent period?
the time between the stimulation of the muscle fibre and the contraction
what marks the contraction period?
crossbridge formation
What marks the relaxation period?
When peak tension is developed and stimulation is removed i.e release of crossbridges
skeletal muscles can be classified as _______ twitch or _______ twitch muscle fibres.
slow
fast
What is muscle tone?
the continuous and passive partial contraction of muscles
What kind of respiration do slow twitch fibers depend on?
aerobic
is the ATP regeneration (for crossbridge formation) faster or slower in slow twitch fibres?
slower
Are slow twitch fibres fatigue resistant?
yes
What kind of activities are slow twitch fibres helpful for?
sustained muscle contraction
endurance activities
Give an example of a slow twitch muscle?
gluteals
What kind of respiration do fast twitch A fibres depend on?
anaerobic and aerobic
How much faster are fast twitch A fibres that slow twitch fibres?
2-3 times faster
Are fast twitch A fibres able to regenerate ATP faster or slower?
faster
Fast twitch A fibres have a ______ blood vessel count.
high
Give an example where fast twitch A fibres are useful.
short period of intense activities eg throwing a javelin or strength training
What kind of respiration do fast twitch B fibres depend on?
anaerobic
How much faster are fast twitch B fibres than slow twitch fibres?
2 - 3 times
Are fast twitch B fibres able to regenerate ATP fast?
yes
Do fast twitch B fibres have a low or high amount of blood vessels?
low
How do fast twitch B fibres get ATP?
glycogen
Do fast twitch B fibres fatigue quickly?
yes
Give an example of exercise that fast twitch B fibres help with.
sprinting
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
What is the agonist?
the prime mover, a muscle whose contraction moves a part of the body directly
what is the antagonist?
the muscle that relaxes when the agonist contracts
What is the synergist?
the muscles that help to create the movement
what is the fixator?
the muscle that stabilises the origin of the agonist and the joint that origin spans
what are the two types of isotonic muscle contraction and the other type of muscle contraction/
concentric
eccentric
isometric
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
