Lesson 21 Flashcards
excitation
action potentials in motor nerve fiber lead to action potentials in the muscle fiber
excitation-contracting couping
events that link the action potentials on the sarcolemma to activation of the myofilaments, thereby preparing them for contraction
contraction
the step in which the muscle fiber develops tension and may shorten
relaxation
when stimulation ends, a muscle fiber relaxes and returns to its resting length
what molecule helps muscle return to their resting length?
titin
rigor mortis
hardening of muscles and stiffening of the body beginning 3-4 hours after death
what causes rigor mortis?
muscle relaxation requires ATP, and since the cell is dead it cannot produce more ATP to break the cross bridge
tension produced by muscle fibers depends on: (3)
- the number of pivoting cross-bridges that are formed
- the fiber’s resting length at the time of stimulation
- the frequency of stimulation of the muscle
length-tension relationship
the amount of tension generated by a muscle depends on how stretched or shortened it was before it was stimulated
If overly shortened before stimulated, contraction is _____
weak; thick filaments butt up against Z discs, some thin filaments overlap
if too stretched before stimulated, contraction is _____
weak; minimal overlap between thick and thin filaments results in minimal cross-bridge formation
muscle tone
the nervous system maintains partial contraction to ensure that resting muscles are near optimum resting length
twitch
a single neural stimulation produces a single contraction
threshold
minimum voltage that causes a muscle twitch
increasing the frequency of stimulus delivery increases _____ _____
tension output
