Chapter 1 Flashcards
The strongest force in a muscle can be produced when the muscle is?
Partially flexed meaning many myosin heads are posed above the actin filaments so all of these heads can bind and cause the muscle to contract.
Excitation-Contraction Coupling Phase
The sarcoplasmic reticulum is stimulated to release calcium ions, calcium binds to troponin which causes tropomyosin to move exposing the myosin binding site on actin. The cross-bridge binds to actin allowing cross-bridge flexion to occur. At any time the amount of cross-bridges bound to actin dictates how much force the muscle can produce
Contraction Phase
ATP attached to the crossbridge and is broken down to ADP which causes flexion. Then another ATP molecule must replace the ADP by binding to the crossbridge allowing it to detach from the actin site and recock. Calcium and ATP are required for cross-bridge cycling
Relaxation Phase
Calcium is pumped back into the SR which prevents the link between actin and myosin
Slow Twitch fiber
Type 1, develop force and relax slowly and have longer twitch times. Are fatigue resistant and use aerobic energy but cannot develop force quickly
Fast Twitch fiber
Type 2, develop force quickly and relax quickly resulting in a short twitch time. Fatigue easily, develop force rapidly and have high anerobic power.
2 ways that a muscle increases its force output.
- Increasing the frequency at which motor units are stimulated.
- By motor unit recruitment
Golgi Tendon Organ
Proprioceptors (sensory receptors sensitive to pressure and tension in joints, muscles, and tendons, which communicate with the nervous system to perform coordinated movements) in tendonsthat inhibits a motor neuron if a tendon is overstretched, causing the muscle to relax
Exergonic reactions
release energy and are generally catabolic
endergonic reactions
require energy and are usually anabolic and involve muscle contraction
What system is present at the start of all activity regardless of intensity?
Phosphagen
Creatine Kinase
enzyme that satalyzed the synthesis of ATP from CP and ADP so that ADP + CP (with the help of Creatine Kinase) can turn into ATP and creatine. So obviously type 2 fast twitch fibers contain higher concentrations of CP than Type 1.
Sarcoplasmic Reticulum Function
Store and release calcium ions to regulate muscle contraction
Tetanus
a convergence of smaller contractions in order to create a steay contraction
Sliding Filament Theory
The actin dilaments at each end of the sarcomere slide inward on myosin filaments, pulling the z-lines toward the center of the sarcomere and thus shorteing the muscle fiber. As actin filaments slide over myosin filaments, bothe the H zone and I band shrink.
Type 2a fibers
have greater capacity for aerobic metabolism and more capillaries surronding them than type 2x
Type 2x fibers
show greater ressistnace to fatigue than type 2a
Which of the following structures do the cross-bridges attach during muscle action?
Actin
When throwing a baseball, an athlete’s arm is rapidly stretched just prior to throwing the ball. Which of the following structres detects and reponds to that stretch by feflexively increasing muscle activiy?
Muscle spindle
Muscle Spindle
are sensory receptors within the belly of a muscle, which primarily detect changes in the length of this muslce. The convey length information to the CNS via sensory neurons.
