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Motor Unit and Muscle Action
Motor Unit and Muscle Action
26
Anatomy
Graduate
03/16/2015

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Term
3 general types of muscles
Definition
smooth, cardiac, skeletal
Term
what makes up myofibrils (2)
Definition
filaments, sarcomeres
Term
what makes up muscle fibers
Definition
myofibrils
Term
after fibres, what is the next largest level of muscle organization
Definition
bundle of fibres
Term
what is the largest level of muscle organizaiton
Definition
muscle
Term
a typical muscle is controlled by about a hundred large motor neurons whose cell bodies lie in a distinct cluster called what
Definition
motor nucleus
Term
a typical muscle is controlled by about a hundred large motor neurons whose cell bodies lie in a distinct cluster called a motor nucleus located in what
Definition
spinal cord or brain stem
Term
each muscle fiber is normally innervated by only one motor neuron in only one place, usually near the midpoint, except
Definition
during development
Term
ensemble of muscle fibers innervated by a single motor neuron
Definition
muscle unit
Term
ensemble of muscle fibers innervated by a single motor neuron together with its motor neuron is called what
Definition
motor unit
Term
functional connection between a motor neuron and a target muscle fiber is a chemical synapse called what
Definition
the end plate
Term
the neuromuscular synapse formed by a motor neuron on a muscle fiber is large and filled with many vesicles containing what
Definition
neurotransmitter acetylcholine
Term
acetylcholine released from the presynaptic terminal is rapidly hyrdolyzed by what
Definition
acetylcholinesterase
Term
acetycholine being rapidly hydrolyzed ACHase results in what
Definition
muscle fiber is ready to respond again in an all or none manner to the action potention
Term
once the postsynaptic membrane of the neuromuscular junction is depolarized to threshold an action potential propagates along the membrane of the muscle fiber, what is this membrane called
Definition
sarcolemma
Term
most mammalian muscles are composed of a a mix of 3 types of muscle fibers what are they
Definition
slow twitch (type I), fast-twitch fatigue resistant (type IIa), fast-twitch fatigable (type IIB)
Term
red muscles are composed mostly of what muscle fibers
Definition
slow twitch type I
Term
describe the force produced by type I fibers in response to an action potential
Definition
rises and falls relatively slowly
Term
type I muscle fibers use what energy mechanism
Definition
aerobic metabolism
Term
why do individual red muscle fibers produce less contractile force than fast-twitch fibers
Definition
red muscle fibers have fewer contractile filaments
Term
white muscles are composed of what fibers
Definition
type II, fast twitch
Term
type ii fibers rely on what to sustain force output
Definition
anaerobic catabolism
Term
type ii fibers have large stores off what that provide energy
Definition
glycogen
Term
which motor neuron has large cell bodies and large diameter axons. those that supply type I or type II
Definition
type II
Term
in both reflexive and voluntary contractions how are motor units recruited?
Definition
weakest to strongest
Term
sized ordered recruitment serves two important purposes what are they
Definition
energy conservation, matching force production with force required
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