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MCBM 2 - Excitatory Cells Questions with 100% Correct Answers
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MCBM 2 - Excitatory Cells Questions with 100% Correct Answers
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1 of 187Definition
NMJ
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connection between sensory electrical synapse between two
neurons and the brain neurons
chemical synapse between a
junction between two cardiac
motor neuron and the muscle
muscle cells
, it innervates
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2 of 187
Definition
excitable cells
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those capable of developing action potentials across their plasma
membranes. They can do this because they express voltage-gated cation
channels in specific membrane domains (e.g., muscle)
gap junctions (electrically couple the muscle cells of the heart) + desmosomes
("spot weld" the cells together so they don't pull apart when the heart contracts)
tropomyosin binds to actin, blocking myosin binding site, but there is no troponin
in smooth muscle (other calcium binding proteins are involved in regulating
smooth muscle
striations less obvious as in skeletal muscle; individual cardiac cells may branch
(unlike other muscle cells); cells electrically coupled via gap junctions
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,Definition
what do epinephrine and norepinephrine lead to
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the myosin head cannot release from actin until it binds a new ATP. This stage
(low energy myosin bound to actin) is known as rigor, as in the rigor mortis
associated with death (the cells very quickly use up all available ATP when it dies
and as the membrane looses viability, a depolarization induces an action
potential and contraction, but no ATP is available to release myosin from actin).
increase in heart rate by decreasing the degree to which Vm is repolarized
(so Vm starts closer to threshold) and increases the rate at which Vm
spontaneously depolarizes. So the Vm gets to threshold in a shorter
amount of time and thus you see an increase in the frequency of action
potentials per unit time
both contraction and relaxation require the presence of ATP. Contraction also
requires calcium. tension does not develop in a muscle previously exposed to
calcium until ATP is added. If you remove ATP before calcium the muscle stays
contracted (it is in its rigor phase); but it will stay contracted even if you take
away calcium at this point (remember, ATP is still lacking). Not until ATP is added
back in does the muscle relax (in the absence of calcium)
The open RyR calcium release channel allows a rapid flux of calcium ions from
the SR lumen into the cytoplasm (down the electrochemical gradient for
calcium). This flood of calcium into the cytoplasm induces muscle contraction.
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, Definition
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multi: no; single: no sarcolemma
image 8 image 9
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Definition
desmosomes
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a complex of 3 subunits that binds
act to hold cardiac cells
to actin periodically along the
together
filament
duration of the calcium signal (up to
end-to-end sarcomeres in series
some period of time)
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