Chapter 8: Using Muscles and Glands Flashcards
many individual muscle fibers are bundled into ____
fasicles
why are adult muscle cells multinucleated?
because they develop from the fusing of myoblasts in embryo
membrane surrounding each muscle fiber
sarcolemma
muscle fiber’s endoplasmic reticulum
sarcoplasmic reticulum
why does a skeletal muscle look striped?
because of the parallel myofibrils that are aligned in such a way to give a striped appearance.
myofibrils contain arrangements of ___ and ___ that repeat by regular units called ____
myofibrils contain arrangements of ACTIN and MYOSIN that repeat by regular units called SARCOMERES
each muscle fiber contains numerous ___
myofibrils.
each myofibril contains numerous ____
myofilaments (actin and myosin), arranged in sarcomere units.
each sarcomere is separated by a ____
Z line.
in the sliding filament model, the myosin-free bands ___ and the myosin-containing bands stay ____
in the sliding filament model, the myosin-free bands SHORTEN and the myosin-containing bands stay CONSTANT IN WIDTH.
In order for the myosin head to DETACH from actin, what must be present? what happens if it is not present/
you need ATP for myosin head to detach. If there is no ATP, it will not detach and rigor mortis will set in.
The energy to generate a myosin bending force comes from the release of a phosphate from ATP creating ADP.
To release the myosin head from the actin binding site, the ADP on the myosin head must be replaced by a new molecule of ATP.
2 things needed for cross bridge cycling to occur
Ca2+ and ATp
if the end of the muscles are fixed, then further actin-myosin interactions result in an ___ ___ , which is:
isometric contraction: the muscle pulls on its attachment site but does not change in length. (ex/ balling your hands in a fist. There is no movement happening but you are clenching your muscles).
Briefly explain the need for a neuromuscular junction
Motor neurons release acetylcholine at neuromuscular junctions. Acetylcholine depolarizes the sarcolemma, triggering an action potential that spreads through the T-tubule system into the muscle fiber’s interior where it triggers calcium release from the sarcoplasmic reticulum.
___ twitch fibers predominate in small muscles that require intricate but weak movements
FAST twitch. ex/ iris or vocal cords.
___ twitch fibers predominate in large muscles that tend to stay contracted for long periods of time
SLOW twitch.
Describe how myoglobin content affects muscle contraction ability
large amount of myoglobin = darker meat = lots of mito = oxidative phosphorylation = probably slow twitch fibers that are strong and can remain contracted for a long period of time.
individual muscle fibers are innervated by the axons of ___ neurons whose cell bodies are located either in the ___ horn of the spinal cord or in the ___
individual muscle fibers are innervated by the axons of MOTOR neurons whose cell bodies are located either in the VENTRAL horn of the spinal cord or in the MEDULLA (reflex)
the synapse between a motor axon and skeletal muscle fiber is called a
neuromuscular junction
Each muscle fiber is innervated by only one axon, but each axon innervates multiple muscle fibers (top right). ONE axon and all the muscle fiber cells it innervates is called a
motor unit
T Tubules extend from small openings in the ____ deep into the muscle fiber so they can adequately contact the ___ ___
T Tubules extend from small openings in the SARCOLEMMA deep into the muscle fiber so they can adequately contact the SARCOPLASMIC RETICULUM
acetylcholine is released from the ___ ___, floats through the neuromuscular junction and diffuses to the post synaptic side of the synapse called the ___ ___ ___
acetylcholine is released from the MOTOR NEURON, floats through the neuromuscular junction and diffuses to the post synaptic side of the synapse called the NEUROMUSCULAR JUNCTION
When acetylcholine binds to cholinergic receptors on the muscle fiber, it allows an influx of ____, depolarizing the ____, triggering an ___ ___ ___.
When acetylcholine binds to cholinergic receptors on the muscle fiber, it allows an influx of Na+ depolarizing the SARCOLEMMA, triggering an END PLATE POTENTIAL.
This end plate potential opens VOLTAGE GATED Na+ channels, which let even more sodium into the muscle fiber cell, triggering a MUSCLE ACTION POTENTIAL.
As an action potential that was started by motor neuron stimulation travels down the T tubules and sarcolemma of the muscle fiber, ___ ___ (voltage gated) open, causing Ca2+ to be released from the ___ ___
As an action potential that was started by motor neuron stimulation travels down the T tubules and sarcolemma of the muscle fiber, RYANODINE RECEPTORS (voltage gated) open, causing Ca2+ to be released from the SARCOPLASMIC RETICULUM
___ ___ channels physically link T tubules of the sarcolemma to the deeper parts ____ ___, and ensure that action potentials conducted throguh the T tubules causeCa2+ to be released from the sarcoplasmic reticulum into the sarcoplasm.
RYANODINE RECEPTORS channels physically link T tubules of the sarcolemma to the deeper parts SARCOPLASMIC RETICULUM, and ensure that action potentials conducted throguh the T tubules causeCa2+ to be released from the sarcoplasmic reticulum into the sarcoplasm.
What is calcium induced calcium influx?
when ryanodine receptors between the T tubules and sarcoplasmic reticulum open and release Ca2+ into the sarcoplasm, the ELEVATED CA2+ levels OPEN EVEN MORE CA2+ channels in the SR and cause even MORE Ca2+ release.
This huge amount of Ca2+ is sufficient to activate the tropomyosin complex. In conjunction with ATP, the myosin binding sites on the actin filament complex get exposed, facilitating binding and power stroking of the filaments.
before a muscle can relax, the sarcoplasmic Ca2+ must decrease in order for tropomyosin to move back to cover the binding sites on the actin filament. How is this accompolished? (2 ways)
1) protein parvalbumin.
2) Ca2+-ATPAse; uses ATP to pump Ca2+ back into the SR, building back its stores.
When does tetanus occur?
when action potentials recur at intervals that are too fast for Ca2+ to be brought back into the Sr from the sarcoplasm, resulting in sustained contraction because of HIGH FIRING RATES of motor neurons.
What is myasthetnia gravis? How is treated?
autoimmune disesase resulting in serious muscle weakness because the body develops antibodies to its own acetylcholine receptors
Treatment: drugs that inhibit acetylcholinesterase, to PREVENT Ach breakdown. Allows Ach to stay in the cleft longer and raise the probability to interact with whatever receptors the pt has remaining.
A nicotinic receptor is ionotropic or mechanotropic? Where is it located?
IONOTROPIC. Stimulated by nicotine, blocked by curare. Receptor between pregang and post gang neuron
