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
increased cross section=____ force
increased
pennate fiber arrangement
perpendicular arrangement
large cross section
large force
short length=small length change
parallel fiber arrangement
small cross section=small force
long length=long length change
type 1 muscle fibers (slow oxidative)
slow twitch
small diameter
red
O2 rich-aerobic
longer lasting
recruited first
endurance
type 2a muscle fibers (fast oxidative)
fast twitch
large fibers
aerobic and anaerobic
fast force production, less endurance
red/pinkish
type 2b muscle fibers (fast glycolytic)
fast twitch
intermediate fibers
anaerobic-glycolysis
white
strong, rapid
fatigue faster than type 2a and type 1
last to be recruited
order of recruitment
type 1, 2a, 2b
what are the postural muscle fiber type?
type 1
what are the positional muscle fiber type?
mostly 2b
what are the factors affecting velocity and duration of muscles contractions?
load and recruitment
greater load=___ latency, ___ and ____contractions
longer, slower, briefer
more motor units recruited=___ and ___ muscle contractions
faster, more prolonged
concentric: heavier load=___ velocity
lower
concentric: lighter load=___ velocity
higher
what type of relationship do load and velocity have concentrically?
an inverse relationship
is there greater force production eccentrically or concentrically
eccentrically
what relationship does concentric force production have to velocity of shortening?
inverse
what relationship does eccentrically force production have to velocity of shortening?
direct
increase force concentrically=___ velocity
decrease
increase force eccentrically=___ velocity
increase
aerobic (endurance) exercise leads to…
increased capillaries, mitochondria, and myoglobin synthesis
anaerobic exercise leads to…
muscle hypertrophy, increased myofilaments, glycogen storage, mitochondria, connective tissue, and muscle strength
where do muscle tissues come from?
embryonic myoblasts (from the mesoderm)
how do muscles develop?
head to toe and proximal to distal
peak neural control age
mid adolescence
as you age, connective tissues…
increase
as you age, muscle fibers…
decrease
when does sarcopenia start?
age 30
preferential atrophy of what type of fibers?
type 2 fibers
decreased satellite cells=___ healing
decreased
decreased neurons leads to what
muscle fibers losing their input
