Muscle Cells Flashcards
What are the 4 characteristics of muscle tissue?
excitability, contractility, elasticity, extensibility
excitability in a muscle cell means
outside stimuli can initiate electrical changes in the muscle fiber leading to contraction of that muscle fiber
what does the characteristic contractility mean?
stimulation of muscle fiber can lead to contraction or shortening of the muscle fiber
What does the characteristic elasticity mean
describes the muscle fiber’s ability to return to its original length whehn the tension of contraction is released
what does the characteristic extensibility mean
the ability of a muscle fiber to be stretched beyond its relaxed length
what is the shape/ nuclei of skeletal muscle cells
long, multinucleated (nuclei towards edges)
What is a motor unit
consists of a single motor neuron and the muscle fibers it controls
do larger muscles or smaller muscles have more motor units
larger muscles
What does it mean that muscle fibers obey the all-or-none principle
a muscle fiber contracts completely or not at all
Henneman’s Size Principle
As force increases in a muscle, more and larger motor units are recruited to generate larger force
What is the first recruited motor neuron
slow type
S type motor neurons are (big or small, what kind of excitability)
small, high excitability
what type of neurons are recruited second?
fast, fatigue resistant
FR type motor neuron characteristics (big or small, what kind of excitability)
big, “average” excitability
What is the 3rd recruited motor neuron
fast, fatigable
FF characteristics (big or small, what kind of excitability)
very big, “low excitability”
What determines the strength of the contraction?
the number of motor units that are activated
Muscle tone
the continued steady, low level of contraction that stabilizes joints and maintains general muscle health
synaptic knob
expanded end of the neuron; synaptic terminal
synaptic vesicles
membrane-bound sacs filled with acetylcholine
synaptic cleft
narrow space separating the synaptic knob from the motor end plate
motor end plate
region of sacrolemma across from the synaptic knob that has folds and indentations to increase the surface area in that region
Where are the ACh receptors
in the motor end plate
Acetylcholinesterase (AchE)
an enzyme in the synaptic cleft that rapidly breaks down ACh
