muscular physiology Flashcards
are somatic motor neurons voluntary
yes
what is one motor unit
one motor neuron
all muscle fibers connected to it
how many neurons can be on one muscle fiber
one
do muscle fibers of one motor unit contract in unison or separately
in unison
where is where a nerve fiber and muscle fiber meet
synapse
where is the gap between the axon terminal and sarcolemma
synaptic cleft
how is the sarcolemma modified to allow for more Ach receptors
folds
what “eats” Ach and makes movements not carry on
acetylcholasterase
what is the swollen end of a nerve fiber
axonal terminal
what happens right after the arrival of a nerve signal
Ach releases from vesicles
what happens after ACh releases from synaptic vesicles and it binds to the receptor
depolarization of the membrane
at rest, what part of the membrane is + / -
+: extracellular
-: intracellular
what is the difference in electric potential between the inside and outside of a cell called
membrane potential / membrane voltage
what 3 ions are in excess on the outside of a cell during membrane potential
sodium
calcium
chlorine
what ion is in excess on the inside of a cell during membrane potential
potassium
what is the increase of positivity of membrane potential
depolarization
what ion is constantly leaking out of the membrane
potassium
what determines the negative resting potential of the membrane
potassium leaking out of the cell and negative proteins within the cell
what causes sodium channels to open
ACh binding to receptors
sodium channels opening cause a the cell membrane to be ________
depolarized
what is the cause of repolarization of the cell
what closes and what enters
sodium channels close and potassium channels open and K goes back into the cell
what is the time after a muscle fiber has been stimulated to pass before the muscle can be stimulated to contract again
hyperpolarization
what refers to the increase in negativity of membrane AGAIN
hyper polarization
what is excitation contraction coupling
the fact that a contraction FOLLOWS an action potential
where does an action potential propagate down to reach the deep part of a muscle fiber
T tubules
what is calcium’s job in muscle contraction
to bind to troponin so that tropomyosin will roll off of actin
what is occurring during a recovery stroke
_____ of the head
hydrolysis of ATP to ADP and Pi
cocking
during a power stroke, what is happening
myosin is sliding over the actin
what breaks the cross bridge between actin and myosin
ATP binds to myosin
what causes the shortening of muscles
sarcomeres shortening
what are pulled closer together during a muscle contraction
Z discs
where does calcium travel
Down t tubules
how does a muscle stop itself from contracting once its fatigued or has run out of ATP (2)
acetylcholinesterase
reabsorption of Ca by the sarcoplasmic reticulum
what refers to the fact that the amount of tension generated by a muscle depends of how shortened it was before it was stimulated
length tension relationship
what is the optimum resting length
what does it maintain
2-2.5 um
muscle tone
why is a muscle contraction weak if the muscle is too relaxed
there is minimal overlap between myosin and actin
why is there a weak contraction when a muscle is overly shortened
myosin will bump into z discs and won’t be able to contract any farther
what is a quick cycle of contraction and relaxation when stimulus is at or above the threshold
a twitch
what is the graph that illustrates the amount of tension of a muscle over time
a myogram
what are the 3 phases of a twitch
latent
contration
relaxation
what period the delay between stimulus and contraction called
why is this required
this generates ______ tension
latent period
time required for excitation and tensing of elastic components of muscle
internal
the contraction phase generates ______ tension
external
what is the force generated to overcome a load and produce movement
external tension
when is the phase where tension declines to the baseline
how much time does this take relatively
what is absorbed to stop muscle contraction
relaxation phase
longer than contraction
Ca
_____ muscles work more quickly during exercise
______ influences cross bridges
warm
hydration
what is the process of bringing more motor units into play with stronger stimuli
recruitment of multiple motor units
what is the principle that states that weak stimuli recruit small units while strong units recruit large units for powerful movements
size principle
what is the theory that states that after a certain threshold, muscles will contract with the same force
all or nothing theory
muscle twitches have _____ peaks
identical
during imcomplete tetanus / temporal summation, what happens
is this normal
what causes this to happen
what is the “incomplete” referencing
each new twitch rides on the previous one and produces a stronger muscle contraction
yes
more release of Ca
incomplete relaxation between stimuli
during complete/ fused tetanus, what happens
is this normal
steady contractions
no
what is isometric muscle contraction
holding tension (internal tension but external resistance)
what is isotonic contraction
muscle changes length but not tension
what is a contraction where the muscle shortens
concentric contraction
what is a contraction where the muscle lengthens
eccentric contraction
when is calcium released from the SR to bind to troponin
after an action potential has propagated down the length of the muscle
