Lesson 4: Muscles in Action Flashcards
Antagonistic Muscles
Since muscles only cause movement when they contract, muscles must work in antagonistic pairs.
A muscle can only shorten to pull the bone in a single direction, in order to reverse the action another muscle is needed.
Antagonistic muscles move the same bone in opposite directions.
When one contracts, the other relaxes
To raise the forearm the biceps act as the agonist.
They shorten through contraction.
The antagonist, the triceps, are relaxed.
To lower the forearm again, the triceps act as the agonist.
They shorten through contraction
The antagonist, the biceps, are relaxed
Energy Needs
During exercise the energy needs of muscles increase. The muscles use large
amounts of ATP to break the cross bridges formed during sarcomere contraction
Muscles can access ATP differently based on the type of exercise.
For short high energy bursts of activity the muscles can use the small amount of stored ATP or phosphocreatine. Phosphocreatine can transfer a phosphate group to ADP to create ATP.
For sustained effort, the muscles can use ATP obtained from aerobic respiration by accessing glucose in the blood, glycogen in the muscles and liver.
Oxygen is supplied by the bloodstream or a molecule called myoglobin.
Striated Muscle Fibers
Most striated muscles contain a mixture of different muscle fibers.
There are three types of muscle fibers:
Slow Fibers – these fibers produce less forceful contractions and fatigue slowly.
Fast Fibers – these fibers produce very forceful contractions and fatigue quickly
Intermediate Fibers – these fibers produce forceful contractions and fatigue at an intermediate rate.The amount of each fiber within the muscle depend on the function of the muscle and training.
Muscles can respond to the stresses placed upon them
Weightlifting causes the production of myofibrils that consist of fast myosin to increase power generation
Aerobic exercise causes the increase in myoglobin, mitochondria and capillaries that allow for a resistance to fatigue.
