Muscle - Lecture 3 Flashcards
(59 cards)
What happens when calcium leaves the sarcoplasmic reticulum (SR)
Binds to troponin (bound on thin filaments - actin). Troponin part of calcium binding familiy of protein and becomes active.
What happens after troponin becomes active (has bound calcium)
Change in conformation releases tropomyosin that was wrapped around the actin
What the release of tropomyosin from actin filaments allows
Liberates the actin molecule’s binding site for myosin head groups
How muscle comes back to a relaxed state after release of calcium from the SR
Calcium is pumped back into the SR so troponin and tropomyosin back in place
What is a twitch
A contraction of a muscle fiber in response to a single AP
Why a twitch lags (little gap before AP and contraction)
Because of the series of events that must happen between AP and muscle contraction
What is reflected by the duration of contraction (from a single AP)
The time that it takes for calcium concentration to return to baseline
Name of the force generated by a muscle and the two things that control it
Tension.
Is controlled by Recruitment and Summation
Skeletal muscle what it is adapted for (how much force and how large its functional range is)
Adapted for large force generation over a narrow operating range
Recruitment def.
Varying the number of muscle fibers involved in a contraction
By what mechanism do muscles vary the force of their actions
By recruitment
Motor units can be _____ or ______ but recruitment would involve putting more _______ to work and not _________ them
small or large. (more or less muscle fibers for a single motor neuron).
Recruitment : Put more motor units (so motor neurons) to work and not more muscle fibers per motor unit
Summation def. + what it applies to
Additive effects of several closely spaced twitches. APPLIES TO ONE MUSCLE FIBER
The closest the twitches, the higher the ___________
relative muscle tension
What is called the sustained contraction of a muscle fiber and what is necessary to get to it
Fused tetanus. Need close enough APs
What is the converse of a fused tetanus and when does it happen
Unfused tetanus : Happens when close twitches but not close enough. APs fired a little more frequently than the duration of the twitch
In an active muscle, individual fibers can either be ______ or _______
relaxed or contracted
Fused tetanus tension how much greater than twitch tension
3x greater
How ATP rate in muscle fiber changes over multiple twitches and why
Stays the same because rate of use = rate of production
What molecule changes ADP back to ATP and what it happens to it after this change
Creatine phosphate. Is a Pi storage molecule. After putting a phosphate on ADP to make it ATP, becomes creatine
Which enzyme is involved in creatine phosphate -> creatine / ADP –> ATP
Creatine kinase
How long creatine phosphate can sustain ATP formation in the cell and why
only a couple seconds because of the amount of creatine phosphate in the cell.
What does the creatine phosphate mechanism lasting a couple seconds serve for
Provides time for a more standard metabolic system to take over and produce ATP
Which molecule does the muscle fiber use for a sustained source of energy
Glucose
