Muscle Physiology Flashcards
Unused muscle is degraded or muscle protein degraded faster than it is replaced are two ways that ________ can occur.
Muscular atrophy
What does troponin inhibit and what prevents troponin from doing so?
Cross-bridging and Ca++ (troponin has a high affinity for Ca++)
A ________ is all muscle fibers that are innervated by a single neuron.
Motor unit
What adds new sarcomeres to the ends of muscles?
Stretching
When is phosphocreatine used and for how long?
At the beginning of contraction (maximal) for approximately 5-8 seconds
What are I bands and how do they appear under a light microscope?
Regions composed entirely of actin and appear white
Fewer mitochondria, larger, extensive sarcoplasmic reticulum, minimal blood supply, less myoglobin (white), and glycolytic enzymes present are all characteristics of ________ type muscle fibers.
Fast
How can hypertrophy be described in muscle?
Existing muscle fibers gain more actin and myosin. New muscle fibers are not created
How much energy from nutrients gets used to make ATP and how much of nutrients can be converted to Work, under optimal conditions?
50% and 25%
What happens when a muscle is at rest?
The muscle receives impulses from the spinal cord so a certain amount of tautness remains in the muscle at all times
Lots of mitochondria, smaller, smaller nerves, extensive blood supply, and large supplies of myoglobin (red) are all characteristics of ________ type muscle fibers.
Slow
What is believed to attach tropomyosin to actin?
Troponin
What are the two types of contractions and their respective subdivisions?
Isometric: contraction where muscle does not change length
Isotonic:
- eccentric: contraction where muscle gets longer
- concentric: contraction where muscle gets shorter
What are Z disks and what is the region between 2 Z disks called?
The anchoring site of actin. Sarcomere
What is required for Ca++ to be pumped back into the sarcoplasmic reticulum?
ATP
What anaerobic method of ATP production can be used to supply muscle? How long does it last?
Glycolysis. Approximately 1 min
Small motor units are recruited initially followed by larger motor units (if necessary) is a process known as ________.
Multiple fiber summation
How does each head of myosin act when “walking” across the actin?
Independently
How many myofibrils is each muscle fiber composed of?
Hundreds to thousands (approximately 1500 myosin filaments and 3000 actin filaments)
What are the spaces between muscle fibers filled with and what does it contain?
Sarcoplasm. K, Mg, PO4, enzymes, lots of mitochondria, sarcoplasmic reticulum
________ motor muscles have motor units consisting of a few muscle fibers whereas ________ motor muscles have motor units consisting of many muscle fibers.
Fine, gross
________ occurs when there is an increased frequency of action potentials (which can lead to tetany or maximal sustained contraction).
Frequency summation
What are A bands and how do they appear under a light microscope?
Composed of myosin filaments, either alone or overlapping with I bands. They appear dark
What links Z disks with myosin filaments?
Titin
