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The Sarcoplasmic Reticulum is a:
series of tubes formed by membranes around each myofibril. Is similar to smooth endoplasmic reticulum.
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The action of the Sarcoplasmic Reticulum is to:
Store the calcium ions in relaxed muscle.
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What are the dilated ends of a section of the sarcoplasmic reticulum called:
Terminal cisterns
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Describe what a Transverse Tubule looks like:
Tunnel like infoldings of the sarcolemma that extend inward at right angles to the myofilaments
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Each sarcomere has ______ and are filled with _____________ _______
two T Tubules, extracellular fluid.
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Triad=
transverse tubule + 2 terminal cisterns on either side of it.
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_______ are the basic functional units of striated muscle fibers.
sarcomeres
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Sarcomeres are divided into _____ and _____
bands and zones
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The Z-discs mark the divisions between _________
saromeres
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Darker areas in the sarcomere is called the
A Band
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The lighter area in the sarcomere is called the
I Band
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The Transverse tubules are located at the junction between ____ and ____ bands
A and I
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The ____ band has only thin filaments in relaxed muscle
I band
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The __ zone within the A band have overlapping filaments.
H zone
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Other parts of the __ band have overlapping filaments
A
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__ line is formed by proteins that connect adjacent thick filaments
M line
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Z discs are places where:
thick filaments are anchored
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During Contraction, thin filaments slide:
inward toward the H zone
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Explain why Muscles shorten?
filaments overlap but do not change in length
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Myosin molecules have a head and tail region what is the head also referred to as?
Cross bridges
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In a relaxed muscle the heads become activated by energy from _____
ATP
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Actin molecules have myosin binding sites that are covered in a relaxed muscle by a regulatory molecule called?
tropomyosin
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Another regulatory molecule called _____ is present in the thin filaments
troponin
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Signals from nerves result in:
changes in the membrane of muscle that travels into the transverse tubule system to release of calcium ions from the sarcoplasmic reticulum
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The _____ ____ combine with tropin , causing it to change shape
calcium ions
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The shape change moves the _______ and the _______ away from the myosin binding sites.
troponin and the tropomyosin
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The activated myosin heads bind to the myosin-binding sites on _____
actin
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When the nerve stops stimulating the muscle, muscle action potentials _____
stops
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During _______, calcium stops being released from the sarcoplasmic reticulum and is pumped back into
relaxation
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Explain Rigor Mortis (rigidity of death)
Calcium leaks out and the cross bridges attach, No ATP produced so cross bridges cant detach
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When does Rigor Mortis begin
3-4 hours after death, peaks at about 12 hours
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When does Rigor Mortis end:
Diminishes over the next 48-60 hours as tissues begin to disintegrate.
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Maximum force is exerted when maximum number of ______ ______ make contact
cross bridges
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At ______ ______, fewer cross bridges can bind
longer lenghts
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At ______ _______, thick filaments crumple
short lenghts
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Maximum force is exerted at ________ ________
intermediate lenghts
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Neurons that stimulate muscles to contract are _____ ______
motor neurons
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A motor neuron and all the skeletal muscle fibers it stimulates=
a motor unit
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All the fibers of a ____ _____ contract and relax together
motor unit
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________ is the minimum voltage necessary to produce contraction.
Threshold
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Amount of force generated on muscles depends on 4 factors which are:
length of muscle fibers before they contract, Number of muscle fibers contracting, The structure of muscle (arrangement of fascicles) and the Frequency of stimulation
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The number of muscle fibers contracting depends n the number of _____ ______ and the ____ of an individual____ _____
motor unit, size, motor unit
-
The process of increasing the number of active motor units
recruitment
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Twitch Contraction is a:
briefd contraction of all the fibers in a motor unit in response to a single action potential in the motor neuron
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First Part of Twitch contraction = latent period where:
calcium is released and slack taken up in the system
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Second Part of Twitch contraction= contraction phase:
muscle tension increases
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Third Part of Twitch contraction= ________ phase in which calcium ions are taken back up and muscle tension decreases.
relaxatation
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Wave (temporal summation) is caused by?
a stimuli that arrives after the refractory period but before the relaxation period is over
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In the ________ period a muscle that has contracted temporarily loses its ability to contract.
refractory
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What is Tetanus
no relation between stimuli
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What the cause of Muscle Fibers?
few muscle fibers are contracted involuntarily at a given time.
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What is the cause of Cramps?
Painful, spasmodic contractions triggered by the spinal cord
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Cramps are initiating by:
irritating factors such as extreme cold, heavy exercise, lack of blood flow, electrolyte depletion, dehydration, or low blood glucose.
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All fibers of a single motor are of the:
same type
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Nearly all muscles have a mixture of _____ twitch and _____ twitch motor units in them but the proportions differ according to each muscles function.
slow and fast
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Slow-twitch fibers are:
- smaller have abundant mitochondria, capillaries, myoglobin , Are RED, low glycogen content, aerobic respiration, resistant to fatigue,
- Examples: Soleus and postural muscles of spinal column
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Fast- Twitch fibers are:
- Larger, fewer mitochondria, capillaries and low myoglobin content, and WHITE, high glycogen content, anaerobic,poor resistant to fatigue
- Examples: Gastrocnemius, biceps brachii
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Slow twitch muscles are used in:
Endurance activities
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Fast-Twitch are used int:
Rapid intense movements of short duration
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