-
In skeletal muscle, minimum unit of contraction is a __, which is measured in terms of __, or force it generates
twitch; tension
-
A single action potential generates __. Force generated depends on __
- a single twitch;
- how many fibers are in the motor unit
-
Tension generated by entire muscle depends on:
- number of motor units activated
- frequency at which motor units are firing
-
If action potentials are close together in time, the twitches are __, tension __
summed; increases
-
Twitches sum because __
Ca2+ pumps can not clear Ca2+ from sarcoplasm before next action potential arrives
-
__ occurs when action potentials are so frequent there is always Ca2+ in the sarcoplasm
Tetanus
-
How long muscle fiber can sustain tetanus contraction depends on __
ATP supply
-
__ is needed to break the actin-myosin bonds, and "re-cock" the myosin heads
ATP
-
To maintain contraction, actin-myosin bonds have to __
keep cycling
-
Slow-twitch fibers are __ & contain __
- oxidative or red muscle;
- myoglobin (oxygen binding protein), many mitochondria, and is well-supplied with blood vessels
Maximum tension develops slowly.
-
fiber that is highly resistant to fatigue. Muscles with high proportion of this type of fiber are good for aerobic work (e.g. long distance running, cycling, swimming, etc.)
slow-twitch fibers (oxidative or red muscle)
(page 41 & 42 on slide)
-
__ fibers have reserves of glycogen & fat. They can produce ATP as long as oxygen is available.
Slow-twitch
-
Fast-twitch fibers are __ & contain __
- glycolytic or white muscle;
- little or no myoglobin, fewer mitochondria, fewer blood vessels
Develop greater maximum tension faster
-
fiber that develops fatigue more quickly & can't replenish ATP for prolonged contraction
fast-twitch fibers (glycolytic or white muscle)
(page 41 on slide)
-
__ determines how much force can be generated (in muscles)
The resting length of the sarcomeres
-
If the resting length of the sarcomeres is stretched, there is __, which means __
- less overlap between actin & myosin fibers;
- fewer cross-bridges & less force
-
If the resting length of the sarcomeres is fully contracted, there is __
more space for shortening
-
Muscles have 3 systems for supplying ATP for contractions:
- immediate system
- glycolytic system
- oxidative system
-
The __ system uses preformed ATP & creatine phosphate
immediate
immediate system = ATP + CP
This system is exhausted within seconds.
-
The __ metabolizes carbs to lactic acid & pyruvate.
glycolytic
-
The __ system metabolizes carbs or fats to H2O & CO2.
oxidative
-
Muscles contain __, which stores energy in a phosphate bond that can be transferred to ADP
creatine phosphate (CP)
- used in immediate system
-
The __ enzymes are in the sarcoplasm. ATP generated is then rapidly available to myosin.
glycolytic
Glycolysis alone isn't very efficient. Lactic acid accumulates.
Immediate & glycolytic systems provide energy for less than one minute.
-
__ systems produces large amounts of ATP, but takes place in the mitochondria. ATP must diffuse from the mitochondria to the myosin - rate is slower than other 2 systems
Oxidative
|
|
