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57 Cards in this Set

  • Front
  • Back
a mechanical response of an individual muscle cell, a motor unit, or a whole muscle to a single action potential.
latent period
the delay of a few milliseconds tha occurs btwn the action potential in a muscle cell and the start of contraction, when the cell first begins to generate force.
contraction phase
starts at the end of the latent peroid and ends when muscular tension peaks.
relaxation phase
typically the longest of the tree phases, is the time btwn peak tension and the end of the contraction, when tension returns to zero.
isometric twitch
a twitch during which a muscle generates force but does NOT shorten.
isotonic twitch
a twitch during which a muscle shortens and lifts a constant load.
contractile component
thick and thin filaments of muscle
compared to elastic components
series elastic component
conn. tissue that is in series with the sarcomeres of skeletal muscle
increase in muscle tension with repeated twitch contractions.
1. force generated in individual muscle fibers
2. the # of muscle fibers contracting
What are the 2 factors affecting the force generated by individual muscle fibers.
When a muscle is stimulated repetitively such that additional action potentials arrive before twitches can be completed, the twitches superimpose on one another, yielding a force greater than that of a single twitch
_________ occurs whenever twitches occur at a frequency such that Ca+ cannot be removed from the cytosol as rapidly as it is released from the SR.
________ removal is necessary for relaxation.
Summation reaches a peak called ________.
The ______ are reached when Ca+ levels are great enough to saturate troponin, exposing all myosin-binding sites on actin.
fused tetanus
Ca+ levels are great enough to contiually saturate troponin such that all myosin-binding sites on actin ae continually exposed, resulting in a plateau called _______ _______.
maximum tetanic tension
when the muscle is generating all the force it can
force-generating capacity
The inherent ability of a muscle to generate force which is usually assessed by measuring maximum tetanic tension or peak tension in an isometric twitch.
A fiber's ________ is the crucial variable that determines its force-generating capacity.
A fiber's ________ does not affect its force-generating capacity insofar as i reflects the # of sarcomeres in series, ________ in fibers length do influence its ability to generate force.
increase in # of active motor units
size principle
correspondence btwn the size of motor units and the order of recruitment
motor neurons
The basis for the size principle is not only that motor units vary in size, but that the _______ _______ that control units vary in size.
But more than just the force of muscle contraction is important in movement; the speed with which muscle contract is important as well.
slow-twitch fibers
which contract slowly
control of eye movement
fast-twitch fibers
which contract quickly
gastrocnemius of the leg
Differences btwn the two fibers (slow and fast twitch) are seen in _________ contractions and isotonic contractions.
The difference btwn fast and slow twitch fibers is based not on their size or shape, but instead on the type of _______ present in their thick filaments.
fast myosin
Socalled ____ _______ has the inherent ability to hydrolyze ATP at a faster rate than slow myosin, and the ATPase rate has been found to correlate strongly w/ a fiber's speed of contraction.
Glycolytic fibers
__________ fibers have high cytosolic concentration of glycolytic enzymes and therefore can generate ATP rapidly via glycolysis
oxidative phosphoralation
Glycolytic fibers have a relatively low capacity for generating ATP via ___________ _______________ because they contain relatively few mitochondria, where this occurs.
_________ fibers are rich in mitochondria and have a high capacity for producing ATP via oxidative phosphoraylation.
# of mitochondria
What is the distinction btwn the oxidative and glycolytic fibers?
Another difference btwn the fiber types is that oxidative fibers contain an oxygen-binding protein known as ________, whereas glycolytic fibers lack it.
a reddish molecule that bind oxygen reversibly.
red muscle
Because myoglobin imparts a reddish-brown color oxidative fibers, these fibers are often referred to as ____ _______.
white muscle
Glycolytic fibers, which lack myoglobin and this reddish color, are referred to as ______ _______.
slow oxidative fibers
contain slow myosin and have a high oxidative capacity, producing most of their ATP by oxidative phosphoralyation.
fast glycolytic fibers
contain fast myosin and have a high oxidative capacity and contain fast myosin.
Smooth muscle
muscle cell found in internal organs, blood vessels, and are involuntary
have thick and thin filaments that run obliquely, but no sarcomeres.
Contraction in smooth muscle are triggered when calcium binds reversibly to ___________.
a cytosolic protein that regulates many processes in amotst all cells of the body.
myosin kinase
This binding triggers a conformational change that enables the calcium-calmodulin complex to bind to and activates an enzyme called ________ ________.
The effect of __________ input to smooth muscle cells may be exitatory or inhibitory, depending on whether the neurons in question are sympathetic or parasympathetic.
smooth muscle is regulated by __________ neurons.
____________ is released from varicosities (swellings) located at intervals along the aoxon and diffuses over a long distance to large groups of cells.
gap junctions
In smooth muscle, ____ ________ allow ions to move from one cell to another, so an electrical signal initiated in one cell spreads to neighboring cells.
multi-unit smooth muscle
Most smooth muscle cells are not connected by gap junctions but instead are largely separate and richly supplied w/ neurons; this is called ______-_____ _______ _______.
multi-unit smooth muscle
found in large respiratory airways and large ateries
single-unit smooth muscle
Smooth muscle cells are extensively linked by gap junctions, such tht electrical signals originating in a few cells are transmitted to the rest of the cells; such smooth muscle is innervated by relatively few neurons and is called ______-____ _______ ________.
pacemaker potential
spontaneous depolarization in the resting membrane potential
causes cells to contract and relax in signals
can be influenced by neural activity
cardiac muscle
_______ _______ is similar to skeletal muscle in that it is straited, has the same sarcomere structure, and has contractions that are regulated by the troponin-tropomyosin system.
The heart's contractile activity is said to be ________, whereas the contractile activity of skeletal muscle is said to be neurogenic.
_______ action potentials are broad and last for hundreds of milliseconds, making them quite different from the spiky action potentials that occur in skeletal muscle and most neurons of last for 1-2 milliseconds.
___________ of cardiac muscle can NOT occur.
cardiac muscle
_______ ________ cells are similar to smooth muscle cells in that they are extensively connected by gap junctions, such that an action potential, once initiated, travels throughout the entire cell network.