Unit 8 - Muscular System Flashcards
Explain muscle recruitment
Starting with the smallest motor units, progressively larger units are recruited with increasing strength of muscle contraction. The result is an orderly addition of sequentially larger and stronger motor units resulting in a smooth increase in muscle strength.
Explain how a skeletal muscle can be stimulated to produce a sustained contraction
If a muscle is exposed to a series of stimuli increasing in frequency, a point is reached where the muscle is unable to complete its relaxation period before the next stimulus arrives. This stacking of twitches causes a sustained contraction.
What is a tetanic contraction?
A tetanic contraction results when a sustained forceful contraction lacks even partial relaxation
What is muscle tone?
Muscle tone is a response to nerve impulses originating repeatedly from the spinal cord, and traveling to small numbers of muscle fibers within a muscle
What do concentric contractions do?
Cause muscle to shorten, generating force
What do eccentric contractions do?
Cause muscles to elongate in response to a greater opposing force
Describe the difference between fast-twitch and slow-twitch muscles.
Slow-twitch muscles use energy slowly and fairly evenly to make it last a long time. This helps them contract (work) for a long time, without running out of power. Fast-twitch muscles use up a lot of energy very quickly, then get tired (fatigued) and need a break.
Compare and contrast the characteristics of smooth muscle, cardiac muscle, and skeletal muscle structure.
Skeletal muscle is voluntary and striated, cardiac muscle is involuntary and striated and smooth muscle is involuntary and non-striated.
Compare the characteristics of smooth muscle, cardiac muscle, and skeletal muscle contractions.
Skeletal and cardiac muscle contracts and relaxes in short, intense bursts, whereas smooth muscle sustains longer or even near-permanent contractions.
Explain how ATP and creatine phosphate function in muscle contraction.
When the muscle starts to contract and needs energy, creatine phosphate transfers its phosphate back to ADP to form ATP and creatine. This reaction is catalyzed by the enzyme creatine kinase and occurs very quickly; thus, creatine phosphate-derived ATP powers the first few seconds of muscle contraction.
Describe how oxygen is supplied to skeletal muscles.
Oxygen is carried from the lungs by hemoglobin in the blood. When the hemoglobin reaches the muscle, the oxygen is transferred to the myoglobin in the muscle fiber.
Describe how an oxygen debt may develop.
During strenuous exercise, primarily the muscles and not the liver use the oxygen, so the lactic acid accumulates. Oxygen debt then, is defined as the amount of oxygen needed by the liver to convert the lactic acid back into glucose, plus the amount needed by the muscles to resynthesize ATP and creatine phosphate and return them to their original concentrations. Because the conversion of lactic acid into glucose is a slow process, it may take several hours to repay the oxygen debt.
How does muscle fatigue occur?
If a muscle is exercised strenuously for a long period, it may lose its ability to contract. This is called muscle fatigue.
What is the most common cause of muscle fatigue?
The accumulation of lactic acid from anaerobic respiration. The lactic acid causes factors, such as pH, to change so that the muscle fibers no longer respond.
What causes a muscle cramp?
A lack of ATP
