Anatomy and Physiology Ch 10 (skeletal muscle structure / contraction of skeletal muscle) Flashcards

Terms Definitions
neuromuscular junction
axon terminals and a skeletal muscle fiber
synaptic cleft
space between the synaptic end bulb and the sarcolemma where acetylcholine diffuses to the motor end plate
synaptic end bulb
branching divisions off the end of an axon terminal
motor unit
a somatic motor neuron and all the skeletal muscle fibers it ennervates
synaptic vesicles
vesicles within the synaptic end bulb that are filled with acetylcholine
neurotransmitter molecules
motor end plate
region of the sarcolemma directly across from the synaptic end bulb
contains ACh receptors
plasma membrane of a skeletal muscle fiber
somatic motor neurons
neurons that stimulate skeletal muscles to contract
the detection, amplification, and recording of changes in skin voltage produced by underlying skeletal muscle contraction
(electrical impulses generated and conducted by muscle fibers)
force or strength of a contraction depends on:
frequency of motor neuron impulses
number of motor units activated
(motor unit recruitment)
state of slight tension in resting skeletal muscles that maintains the muscle in a state of readiness
changing the strenth of a muscle contraciton in proportion to the load placed on it
primary function of muscle
to convert chemical energy to mechanical work
(muscle contracting)
layer of areolar connective tissue surrounding
skeletal muscle fibers
bundles of skeletal muscle fibers
layer of dense regular connective tissue surrounding fascicles
bundles of fascicles
layer of dense regular connective tissue surrounding a muscle
formed from endomysium, perimysium and epimysium that extend beyond each skeletal muscle fiber
sarcoplasmic reticulum
endoplasmic reticulum in skeletal muscle fibers that specializes in storing calcium
bundles of thick and thin filaments that contain different proteins
movement of myofibrils causes muscle contraction
orderly arrangement of thick and thin filaments
the smallest structural and contractile unit of a muscle myofibril
composition of thin filament
actin (binding site for myosin)
tropomyosin (nestled between the actin molecules)
tropin (molecules that bind at precise intervals along the tropomyosin strand)
T tubules
tubelike invaginations in the sarcolemma that transmit the action potential to terminal cisternae
terminal cisternae
widened areas of the sarcoplasmic reticulum
two terminal cisternae with
a T tubule between them
composition of thick filaments
myosin molecules (twisted golfclubs)
the tails form the thick filament
heads (crossbridges) project toward the thin filaments
Z discs
narrow, plate-shaped regions of dense material that separate one sarcomere from another and secure the thin filaments
I bands
lighter, less dense areas that contain only thin filaments
stripes are Z discs
A bands
darker middle part of each sarcomere
extends the entire length of the thick filaments
M line
supporting proteins that hold the thick filaments together at the center of the H zone
H zone
narrow center of each A band
cotains only thick filaments
Fast Glygolytic Fibers (cells)
large diameter
lower myoglobin & blood supply
lighter in color (white)
produce ATP by glycolysis
(fast but not enduring)
Slow Oxidative Fibers (cells)
smaller in diameter
more myoglobin & blood supply
darker in color (red)
produce ATP by aerobic cellular respiration
(slow but more enduring)
Fast Oxidative Glycolytic Fibers
medium diameter
medium color (pink)
produces ATP by both methods
4 steps of a muscle contraction
1. ATP hydrolysis energizes the myosin head
2. Myosin attaches to actin to form crossbridge - phosphate is released
3. Power stroke initiated by release of phosphate - ADP is released
4. Another ATP binds to myosin binding poscket of actin releasing the myosin head - return to step 1 as long as there is calcium and ATP available
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