Physiology - Mechanisms of Single Fiber Contraction and Skeletal Muscle Energy Metabolism

Contraction of muscle fiber that is caused by the two thin filaments sliding towards or away from each other?

Towards

Cross bridges attach to the ______________________ and act like oars to "row" the thin filaments toward the center of the sarcomere.

Thin Filaments

Cross bridges attach to the thin filaments and act like oars to "row" the thin filaments toward the center of the ___________________.

Sarcomere

For sliding filament mechanism, which of the following shortens? Thin filament, Thick filament, Sarcomere, or multiple?

Sarcomere

One stroke of the cross bridge yields ____________________ movement of the thin filaments

Very little

Usually, one end of a muscle is attached to a __________________.

Fixed position (origin)

When the sarcomeres shorten during contraction, the centers of the sarcomeres also slide toward the ________________.

Origin

Muscle fiber generates ______________ and ______________ through the interaction of actin and myosin contractile proteins.

Force, Movement

What are the 4 roles of ATP in skeletal muscle energy metabolism?

Provides energy for force generation (hydrolysis of ATP by myosin), breaks the cross bridge/actin bond (binding to myosin), Na/ATPase pump, Ca++ pump into SR

What are the 3 ways muscles can produce ATP?

Use of creatine phosphate, glycolysis, oxidative phosphorylation

How quickly does creatine phosphate produce ATP?

Very rapid

Creatine is naturally produced where?

Kidneys, liver

Over half of creatine stores are provided by what?

Food (meat)

About 95% of the body's creatine is found where?

Skeletal Muscle

Normal range of creatine?

2-12 mg/L

Half life of creatine?

~3 hours

Supplementation of creatine can improve performance of __________________________, ________________________.

high intensity exercise, mental function.

CP can transfer the phosphate and energy to ADP to form ______________ and _____________________.

ATP, free creatine

Can the energy from CP be released by myosin to drive the cross-bridge activity?

No

During rest, CP builds up in the muscle to about how many times ATP.

5X

If contractile activity lasts more than a few seconds, ATP must be produced by other means - not by ______________________.

Creatine Phosphate

When intensity of exercise exceeds about 70% of the maximal rate of ATP breakdown, ___________________- produces the majority of ATP.

Glycolysis

Where does glucose for glycolysis come from?

blood stores, muscle glycogen

As glycolysis increases, what is the byproduct?

Lactic acid

During moderate levels of muscular activity, most ATP is formed by what?

Oxidative Phosphorylation

Oxidative Phosphorylation occurs where?

Mitochondria

For oxidative phosphorylation during the first 5-10 minutes, fuel comes from the breakdown of ____________________ to _______________________.

muscle glycogen, glucose.

For oxidative phosphorylation during the next 30 min, fuel comes from ______________________ such as glucose and fatty acids equally.

blood borne nutrients

For oxidative phosphorylation beyond 45 minutes, __________________ become the primary source of fuel and muscle's glucose utilization decreases.

fatty acids

What do we need to metabolize the built up lactic acid?

Oxygen