Exam #3 Chapter 9 Muscular System (Histology & Physiology) part 2 Flashcards
what is the 2nd step of the cross-bridge cycling to occur?
1) the myosin head pivots
2) releases ADP
3) pulls the thin filament towards the M line (power stroke) (PULL)
what happens to the calcium ions during muscle relaxation?
they are pumped back into the sarcoplasmic retiuclum using ATP
what phases occurs after the stimulus during the muscle twitch in the lab?
the short lag phase, contraction phase and a relaxation phase.
during stimulus frequency and muscle contraction in a lab what does higher frequency stimulations produce?
incomplete tetanus with higher tension but partial relaxations between stimulations
what type of muscle fiber does treppe occur in?
one that has rested for a prolonged period
what type of motor units do muscles that produce delicate movements have?
ones with fewer fibers than large postural muscles that produce powerful, less controlled movements
What are all cells and what do they have?
polarized and they have a resting membrane potential that can be measured
if there is an increasing stimulus at a low frequency what is there?
a gradual increase in tension above the threshold stimulus to a maximal stimulus
during muscle frequency and contraction in a lab how does our nervous system stimulate muscles?
at a high frequency producing complete tetanus and recruits enough motor units to accomplish the task
when is the only time myosin heads can generate force?
in the area of overlap
while producing a muscle twitch in a lab what does a single stimulus produce?
a brief contraction and relaxation generating some tension (force)
what does the force a single fiber generates depends on?
the rate of action potential and the fiber length
how is the muscle tone produced?
involuntarily when one is awake
why does excitation-contraction coupling occur?
because of the anatomical association between the T tubules and the sarcoplasmic reticulum.
what does the membrane cause in and out of the cell?
more negative ions in the cell and more positive ions outside the cell
after the steps of excitation-contraction coupling occur what then occurs?
the steps of cross-bridge cycling now produce a movement
what does the active tension curve show?
the force generated at different muscle lengths
during muscle frequency and muscle contraction in a lab how is an increase in tension achieved?
through multiple-wave summation
what does a single motor neuron innervate?
multiple muscle fibers that are called a motor unit and function together
what is the relaxation phase?
the time during which relaxation occurs
what is excitation-contraction coupling?
the steps between an action potential in the sarcolemma and contraction
if a muscle is stimulated with a constant stimulus at a low frequency what is there?
a small increase in the tension generated (treppe)
what is the 3rd step of the Excitation-contraction coupling to occur?
the action potential n the T Tubule caused a reason of calcium from voltage-regulated channels in the the terminal cisternae
why do sarcomeres generetate little or no force when it is stretched too much?
because there is little or no overlap
when do sarcomeres generate maximum force?
at an optimal length with maximum overlap
what are our muscles generally near?
the optimal sarcomere length
what is an action potential?
a rapid and change to the resting membrane potential
during stimulus frequency and muscle contraction in a lab what does low frequency stimulation produce?
twitches with little tension
what does there need to be in order for the cycle of cross-bridge cycling to occur?
Calcium needs to be present and there needs to be available ATP
what is occurring during isometric contractions?
force is generated but the muscle length does NOT change
what does muscle tone prepare the muscle for?
contraction and steadies the body
what is the first step in contraction?
when a muscle fiber is stiumulated to produce an action potential in the sarcolemma at the neuromuscular junction
what happens at the neuromuscular junction?
a muscle fiber is stimulated to produce an action potential in the sarcolemma
after death do cells have a membrane potential that can be measured?
no
what happens when no more action potentials come down the somatic motor neuron axon?
all the ACH is degraded, stopping action potentials in the sarcolemma.
what happens to the tropomyosin during muscle relaxatoin?
it’s rolled back on the myosin binding sites of actin and contraction ceases
what are the two types of isotonic contractions?
1) concentric isotonic contractions
2) eccentric isotonic contractions
what is the lag (latent) phase?
the gap between the time of the stimulus application to the motor neuron and the beginning of the contraction
what is the 3rd step of the cross-bridge cycling?
An ATP binds to the myosin head and it detaches from the action (RELEASE)
why does the voltage read as a negative number?
because the inside is negative compared to the outside
what is multiple-wave summation?
the adding of calcium releases together
why is little or no force generated in a sarcomere when it is compressed too much?
since the thin filaments overlap or the thick filaments hit the Z disc
what are eccentric isotonic contractions?
the muscle lengthens
what is muscle tone?
the contraction of a few motor units when the muscle is not contracting
what is the 2nd step of the Excitation-contraction coupling to occur?
next to the T Tubules are 2 large sections of the sarcoplasmic reticulum called terminal cisternae that form a triad with the T Tubule
what is the contraction phase?
the time during which contraction occurs
what is the fourth and last step of the Excitation-contraction coupling to occur?
the calcium binds to troponin and moves trypomyosin off the actin active sites to which myosin heads can now bind
what is the first step of the Excitation-contraction coupling to occur?
the action potential in the sarcolemma travels down the T Tubules
what is the 4th step of the cross-bridge cycling?
the myosin head hyrolyzes ATP into ADP and (P) which remain attached and the head recocks (EXTEND)
what type of force does a sarcomere generate when it is compressed too much?
little or no force
during cross-bridge cycling what happens when tropomyosin is moved?
when tropomyosin is moved the myosin head has an attached ADP and an attached inorganic phosphate (P)
in neurons and muscle fibers what are actions potentials always?
the same
during stimulus frequency and muscle contraction in a lab at higher frequency stimulations how is complete tentanus achieved?
with high, steady tension generated by high calcium levels obtained
what is the first step of the cross-bridge cycling to occur?
the myosin head, with an ADP and (P) attached, binds to the myosin binding sites of actin, for a cross bridge and releases the (P) (GRAB)
when can a sarcomere generate little or no force?
when it is stretched too much
what speeds is calcium diffused out down the steep concentration gradiant and pumped back into the sarcoplasmic retiuclum?
it is released at a quick rate and pumped back in slowly
what is occurring during isotonic contractions?
force is generated and muscle length changes
what is the action potential caused by?
ions moving through the membrane in ion channels
what is the force related to during the muscle twitch?
the amount of calcium
what are concentric isotonic contractions?
the muscle shortens
when there is an increasing stimulus at a low frequency that occur during stimulus strength and motor unit response that causes a gradual increase in tension above stimulus to a maximal stimulus, what is this due to?
stimulating more motor units (graded response)
what needs to be present in order for myosin binding sites to be available?
calcium
