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Muscle - Physio 3 SMC

Terms in this set (99)

consists of a motor neuron and all of the muscle fibers it innervates

neuromuscular junction

where the motor neuron and muscle fiber synapse

motor end plate

where ACh receptors are in the muscle fiber sarcolemma

end plate potential

graded depolarization of the muscle plasma membrane

muscle fiber's membrane

excitation contraction coupling

AP> release Ach from terminal> Ach diffuse to sarcolemma> binds to motor end plate receptors> change in ion permeability> graded depolarization of muscle's plasma membrane> end plate potential> series of events> muscle cell contraction

the mechanical response to a single action potential, latent period, contraction phase, relaxation phase

the period of time that elapses between the generation of an action potential in a muscle cell and the start of muscle contraction

contraction phase

starts at the end of the latent period and ends when muscle tension peaks

relaxation phase

the period of time from peak tension until the end of muscle contraction

also known as muscle force

the number of these is reflected by a strong muscle contraction

_______ muscle contraction implies that many motor units are activated, with each unit developing its maximal tension or strength

________ muscle contraction implies that fewer motor units are activated, but each motor unit still develops its maximal tension

motor unit recruitment

by increasing the number of active motor units, we can produce a steady increase in muscle force

a single stimulated contraction of whole skeletal muscle

although no force s generated during this intervall, chemical changes occur intracellularly in preparation for contraction (including the release of calcium from the sarcoplasmic reticulum)

during the ___________ phase, the myofilaments utilize the cross bridge cycle and the muscle develops tension

_________ takes place when the contraction has ended and the muscle returns to its normal resting state and length

threshold voltage

is the smallest stimulus required to induce an action potential in a muscle fiber's plasma membrane, or sarcolemma

stimulus voltage

as the __________________ to a muscle is increased beyond the threshold voltage, the amount of force produced by the whole muscle also increases.

maximal tension

_______ in the whole muscle occurs when all the muscle fibers have been activated by a sufficiently strong stimulus

maximal voltage

a sufficiently strong stimulus

motor unit recruitment

mimics muscle activity in vivo, where the recruitment of additional motor units increases the total muscle force produced

skeletal muscle fibers are innervated by?

sarcoplasmic reticulum

smooth ER where Ca2+ is stored

a single action potential propagating down a motor axon results in a _____ action potential and a ______ contractile event in the muscle fibers it innervates

excitation contraction coupling

during the latent period for an isometric contraction the cellular events involved in _______ ______ _______ occur.

motor unit recruitment

an increase in the number of active muscle fibers to increase the force developed in a muscle

results from activation of cross bridge cycling via increased intracellular calcium levels

threshold voltage

the minimal stimulus needed to cause a depolarization of the muscle plasma membrane (sarcolemma)

maximal voltage

the amount of stimulus required to successfully recruit all the muscle fibers into developing active forve

maximal voltage

at the ________ ________, all the muscle fibers contained in this muscle are depolarized and they all develop active force / they were all successfully recruited

neurotransmitter released at the synaptic knob of a motor neuron

increase in stimulus

results in an increase of force produced by the whole muscle

the progressive increase in force generated when a muscle is stimulated in succession, such that muscle twitches follow one another closely, with each successive twitch peaking slightly higher than the one before

staircase effect

treppe is also known as

occurs when muscle fibers that are developing tension are stimulated again before the fibers have relaxed

stimulus frequency

rate of stimulus delivery to the muscle

occurs because the muscle fibers are already in a partially contracted state when subsequent stimuli are delivered

during a single twitch of a skeletal muscle, maximal force is ________ achieved

is achieved by increasing the stimulus frequency

activated motor units

another way to increase the force produced by a muscle is to increase the number of ______________________

unfused tetanus

when the maximum possible muscle force from each stimulus reaches a plateau

complete (fused) tetanus

if stimulus is applied with even greater frequency, the twitches will begin to fuse so that the peaks and valleys of each twitch become indistinguishable from one another

maximal tetanic tension

when the stimulus frequency reaches a value beyond which no further increases in force are generated by the muscle

stimulus frequency

the rate that stimulating voltage pulses are applied to an isolated whole skeletal muscle

muscle tension increases and decreases during a state of unfused tetanus

develops at this greater frequency stimulus

sustained muscle tension due to very frequent stimuli

a decline in a skeletal muscles ability to maintain a constant level of force or tension after prolonged, repetitive stimulation

accumulations of lactic acid, ADP, and Pi in muscles are though to be the major factors causing ________

cross bridge cycling

during_______ in skeletal muscle,force is created by the power stroke of myosin heads

sustained muscle tension DUE TO repetitive stimuli

during _______ the number of cross bridges begins to decline although the rate of frequency remains constant

if an intervening rest period is imposed on active skeletal muscle the development of fatigue will be _______

when a muscle attempts to move a load that is equal to the force generated by the muscle, the muscle contracts ___________

isometric contraction

the muscle stays at a fixed length, muscle do not shorten even though they are contracted

the length of the muscle before stimulation

is generated by stretching the muscle and results from the elastic recoil of the tissue itself

is largely caused by the protein titian, which acts as a molecular bungee cord

is generated when myosin thick filaments bind to actin thin filaments, this engaging the cross bridge cycle and ATP hydrolysis

the muscle exerts ________ force when it is stretched

the muscle exerts ________ force when it is stimulated

the sum of passive and active forces

isometric length- tension relationship

a graph relating the three forces generated to the fixed length of the muscle

during an _________ contraction, the skeletal muscle is generating force, but it remains at a fixed length

is determined by the amount of myosin bound to actin

passive force in skeletal muscle is largely caused by the protein ________

when a skeletal muscle is stimulated and generates force but remains at a fixed length, the muscle is contracting _____________

cross bridge cycle

active force stimulated through a range of muscle lengths will utilize ATP hydrolysis to drive the ______________

maximal active tension will be produced in a skeletal muscle fiber when the fiber is at its ___________ length

isotonic contraction

the skeletal muscle length changes and thus, the load moves a measurable distance

isotonic concentration contraction

the force generated by the muscle is greater than the weight of the attached load

there is a rise in muscle tension but no observable movement of the weight

shortening velocity

the speed of the contraction

shortening velocity

depends on the load that the muscle is attempting to move

the ________ the load, the slower the muscle twitch

latent period (for isotonic concentric contraction)

during the ___________ of an isotonic concentric contraction, cross bridges cycle and, when muscle tension exceeds the load, muscle shortening occurs

muscle shortening velocity ________ with heavier loads

______ contraction of a muscle is one in which the length of the muscle changes

protein fiber contractile unit

cytoplasm of a muscle cell

cylindrical protein structures that extend the entire length of a single muscle fiber

surrounds each muscle fiber

surrounds fascicles

surrounds entire muscle

a band or sheet of fibrous connective tissue that covers, supports, and separates muscle, forms tendons

where the axon widens to synapse with a myocyte

the space between the synaptic knob and motor end plate

muscle that functions as prime mover

2 muscle that contract together

1 muscle contracts while the other relaxes

middle of sarcomere, anchors myosin

separate one sarcomere from the next

extends between regions where myosin and actin overlap

actin only, extends between sarcomeres

elastic component protein responsible for allowing the sarcomere to stretch and recoil

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