Muscle Physiology Part 2 Flashcards
what is the only energy source for contractile activities?
ATP
how long does it take for ATP to get depleted?
4-6 seconds
what are the 3 mechanisms for ATP regeneration?
direct phosphorylation, anaerobic pathway, and aerobic pathway
what is direct phosphorylation?
CP+ADP=ATP and creatine
creatine kinase catalyzes the transfer of phosphate
immediate source of ATP
short duration contraction
about 15 seconds
anaerobic pathway (glycolysis)
glucose broken down into 2 pyruvic acid and 2 ATP
no oxygen=pyruvic acid becomes lactic acid
- reconverted into pyruvic acid or glucose by the liver
slower than phosphorylation
short term source of ATP (about 30-40 seconds)
aerobic pathway (respiration)
requires mitochondrial reactions and oxygen
can use many different sources
glucose–> CO2+H2O+32 ATP
slower than anaerobic
95% of ATP
long-term source of ATP (more than 30 seconds)
very efficient process
what is muscle fatigue?
the physiological inability to contract despite continued stimulation from motor neurons
what are intrinsic factors that contribute to muscle fatigue?
what’s happening inside the muscle
ionic imbalance
what are extrinsic factors that contribute to muscle fatigue?
what’s happening in the neurons
decreased release of ACh
not as excitable
what is excess post exercise oxygen consumption? (EPOC)
increased breathing effort and blood flow enhances oxygen delivery to muscles
oxygen is taken above resting consumption to restore metabolic conditions
how is oxygen taken above resting consumption?
reconversion of lactic acid into pyruvic acid or glucose
synthesis of CP and ATP
replace O2 and glycogen
what does force production depend on?
of cross bridges formed
what factors effect that number of cross bridges formed?
frequency of stimulation, motor unit recruitment, size of fibers, and degree of stretch (length-tension relationship)
what is the length tension relationship of sarcomeres?
resting length=100% (aligned so all myosin can bind to actin)
max tension at 80-120% of resting length (max overlap of actin and myosin)
understretched (shortened sarcomere)
myosin really close to Z disc so it has some actin to bind to but can’t really pull it anywhere
overstretch (elongated sarcomere)
not much overlap b/w actin and myosin
can’t form cross bridges=can’t generate force
length tension relationship of muscle
active and passive tension
muscle’s optimal ability to produce tension is slightly beyond resting length
what is active tension?
generated by muscle contraction (sarcomere shortening)
what is passive tension?
elastic tissue elements stretched beyond resting length
connective tissues that don’t get excited by APs
after a muscle passes 100%, passive tension increases
- even though active tension decreases, overall tension increases
what is a clinical implication of the length tension relationship?
positioning for manual muscle testing
a quick stretch to a muscle can improve force production
