lecture 9.5 main points Flashcards
when is skeletal muscle at low activity? describe ATP use
when relaxed, only using a moderate amount of ATP
when is skeletal muscle at high activity? describe ATP use
when contracting, using ATP at a rapid pace
why is ATP important for skeletal muscle cells
ATP is the only source used directly for contractile activities
move and detach cross bridges, power calcium pumps in SR and sarcolemma , power return of Na and K to normal levels after excitation
how long does accumulated ATP power the muscle contraction at its onset? what must occur if the muscle is to continue contraction?
3-6 seconds, in order to continue contraction muscle must make more ATP
regeneration of ATP- direct phosphorylation
direct phosphorylation of ADP using creatine phosphate
(adding a phosphate)
especially important in muscle fibers
where is most creatine found in the body
in skeletal muscle
regeneration of ATP - anaerobic pathway
glycolysis to make lactic acid, no oxygen required
glycolysis followed by fermentation
regeneration of ATP - aerobic pathway
glycolysis makes oxygen and modified glycolysis products into mitochondria
what is creatine and where is it made in the body
creatine is a small amino acid derived molecule that is made in the liver, kidneys, and pancreas
what are some dietary sources of creatine
milk, red meat, some fish
describe ATP production and ATP use by the muscle cell at rest
when relaxed, muscle fibers produce more ATP than is needed for resting metabolism (use is low)
at rest, what is the excess ATP used to make
creating phosphate
what transfers a phosphate from ATP to creatine creating creatine phosphate
creatine kinase (an enzyme)
this forms CP and ADP
what chemical environment is necessary for the formation of creating phosphate - an abundance or declining amount of ATP
abundance
at rest, contrast ATP amounts vs CP
CP is 3-6 more plentiful than ATP when a muscle is relaxed
what happens to ATP levels when muscle contracts and uses more ATP than it is making
during contraction, ATP levels decline
during contraction what happens to ADP levels vs ATP levels
ADP levels increase in sarcoplasm
how does creatine kinase respond to the decrease in ATP and rise in ADP with respect to creatine phosphate? how much additional contraction time does this allow for ?
CK takes phosphate back from CP and adds its to ADP creating ATP.
allows for roughly 15 seconds of contraction time
at rest, when a phosphate it taken from ATP what is left over?
ADP and creatine phosphate
when phosphate is added to creatine, what does creatine become
creatine phsophate
during contraction, when is phosphate is taken from creatine phosphate, what is left
creatine
during contraction, when a phosphate is added to ADP what is formed?
ATP
what is the metabolite (breakdown product) of creatine called
creatinine
how is creatinine gotten rid of by the body
filtered by the kidneys into the urine
how much creatine do you require per day, on average
two grams a day through synthesis or dietary means to replace urinary loss
anaerobic pathway, why is called this ?
does not require oxygen
what is the first step of the anaerobic pathway? what is used and what is created? where in the cell does this occur
glycolysis is the first step, glucose is degraded into two pyruvic acid. two ATP molecules are produced per glucose molecule
happens in the cytosol
at 70% or above maximum contractile activity, what happens to muscle blood flow and delivery/removal of nutrients, O2 and wastes?
bulging muscles compress blood vessels, oxygen delivery impaired
If oxygen levels are low, what is the next step in the anaerobic pathway that is needed to allow glycolysis to continue
pyruvic acid converted to lactic acid in order to regenerate specific molecules needed for glycolysis to continue
how is lactic acid removed from the muscle cell
diffuses through the muscle transport proteins into the interstitial fluid and then bloodstream
what organs can use lactic acid for fuel
liver, kidneys, and the heart
what can lactic acid be converted back to and what organ can accomplish this
can be converted back into pyruvic acid or glucose by the LIVER
compare ATP production in anaerobic vs aerobic (speed and amount)
anaerobic yields only about 5% as much as ATP as aerobic respiration, but makes it 2.5 times faster
how long does the anaerobic pathway allow for sustained, strenuous activity
30-40 seconds
what are the drawbacks of the anaerobic pathway
uses huge amounts of glucose for relatively small amounts of ATP produces and creates lactic acid as a byproduct
when does the aerobic pathway dominate for ATP production in the muscle cell
produce 95% of ATP during rest and light to moderate exercise
why is it called aerobic pathway
requires oxygen
what is the first step in the aerobic pathway? what is used? what is created? where in the cell does it occur?
glycolysis is the first step, pyruvate used to produce CO2, H2O, and a large amount of ATP, occurs in the mitochondria
if there is enough oxygen present in the cell during aerobic respiration, what are the next steps and where do they occur
with enough oxygen present in the cytosol, pyruvate is modified and enters the mitochondria where the breakdown of the modified pyruvate during the citric acid cycle produced molecules that are used in oxidative phosphorylation to produce a lot of ATP
what other fuels can be used for the process of the aerobic pathway
stored glycogen, blood borne glucose, pyruvic acid from glycolysis, amino acids, free fatty acids
define aerobic endurance
length of time muscle is capable of contraction using ATP primarily produced from aerobic pathway
define anaerobic threshold
point at which muscle metabolism converts to primarily anaerobic ATP production
contrast energy production during 60 second sprint vs multi hour run
sprint uses ATP stored in muscles first, then uses creatine phosphate, then the anaerobic pathway
multi hour run uses aerobic pathway
define EPOC
excess post exercise oxygen consumption, the amount of O2 repayment required after exercise
why is EPOC necessary
replenish ATP stores, replenish creatine phosphate and myoglobin stores, convert lactic acid back into pyruvate so it can be used in mitochondria to replenish ATP, balance hormones
why is EPOC called the after burn
the greater the EPOC, the more fat stores you may potentially use throughout the day to return the muscle back to original state
how are muscles classified by appearance? contrast red and white muscle
red muscle fibers - dark meat, high myolobin content, many mitochondria, rich vascularization
white muscle fibers - white meat, high amounts of glycolytic enzymes, low myoglobin content, less vascularization
how are muscles classified by function ?
speed of contraction and primary metabolic pathways
muscle function, characteristics of slow v fast fibers
speed at which myosin ATPases split ATP, pattern of electrical activity of motor neurons
muscle function, characteristic of primary metabolic pathways used for ATP
oxidative - use aerobic pathways
glycolytic - use anaerobic
slow oxidative fibers (SO) (Type I)
small, appear dark red
least powerful
myosin heads hydrolyze ATP slowly leading to lower rate of contraction
very fatigue resistant
low amount of glycogen stores
highly vascularized
lots of mitochondria
high myoglobin
aerobic respiration
used for endurance activities
what activities use slow oxidative fibers
postural maintenance, long distance running, swimming, cycling
Fast oxidative glycolytic fibers (FOG) (Type IIa)
intermediate in size, red to pink in color
more myofilaments than SO
slightly less vascularized than SO
moderately resistant to fatigue
myosin heads hydrolyze ATP 3-5x faste than SO, faster contraction
have the most mitochondria
generate considerable ATP through aerobic respiration
high myoglobin
moderate amount of glycogen
can use anaerobic pathway efficiently when oxygen drops
walking and sprinting
what activities use the fast oxidative glycolytic fibers
walking and sprinting
fast glycolytic fibers (FG) (Type IIx) (IId in humans) (IIb in small mammals)
largest, white in color, powerful
many myofibrils
low myoglobin
low amount of mitochondria in comparison to other types
a lot of glycolytic enzymes in sarcoplasm for glycolysis
primarily use anaerobic pathway to generate ATP during contraction
large amounts of glycogen
myosin heads hydrolyze ATP very quickly
what activities use fast glycolytic fibers
short powerful activities, resistance training programs, lifting weights
is a typical muscle made of just one type of muscle fiber?
no, made of a mixture of all three
what skeletal muscle fibers are most common in the average muscle
slow oxidative
what causes variations in the ratio of the three muscle fiber types in muscles
action of the muscle, training program, genetic factors
common proportions of muscle fiber types in neck and back
SO fibers for postural support
common proportions of muscle fiber types in shoulder and arm
higher proportion of FG - used for lifting or throwing but not used all the time
common proportions of muscle fiber types in leg and thigh
SO and FOG - used for support, walking and running
are there different types of muscle fibers in a single motor unit or are they all the same type?
all of the same type within a particular motor unit
in what order and why are the different motor units of a muscle recruited
first SO, then FOG, then FG
small, medium, then large
depending on the amount of force required
what affects the properties of a muscle
regularity of muscle use as well as duration and intensity of activity
what are the effects of exercise on a muscles size and ATP production capacity
can produce an increase in size and change in muscle cells capacity for ATP production
what is hypertrophy
increase in size and diameter but not in number, can happen in response to stress
during hypertrophy what structures are increased in quantity in an enlarged muscle cell
myofibrils- more contractile organelles for more tension generation
mitochondria - bigger muscle cells with more contractile organelles need more ATP to power them
sarcoplasmic reticula - need more Ca storage and release for new myofibrils
what are the effects of strenuous exercise on the muscle cell? list structures affected.
strenuous exercise produces stress and damage to muscle fibers
torn sarcolemmas, damaged myofibrils, disrupted Z discs
what two molecules, normally confined to the inside of the muscle cell, can be found in the blood post exercise
myoglobin, creatine kinase
what does DOMS stand for
delayed onset muscle soreness
how long post exercise does it usually take for DOMS to occur
12-48 hours post exercise
what causes DOMS
what causes DOMS?
cause is not completely understood, microtrauma (microscopic muscle damage) may be a contributing factor
what are some of the structures that are affected by DOMS
sarcomeres, (Z discs, thin filaments, thick filaments)
calcium homeostasis in muscle cell disrupted, ATP production may slow
what time of isotonic contraction causes DOMS?
eccentric
what is the role of lactic acid in DOMS?
does not cause DOMS, lactic acid levels in blood return to normal within an hour after exercise
what happens to muscle fibers In response to damage
undergo repair and adaptation - become more resilient to type of activity that produces damage This decrease damage and soreness from future activities of similar type
what happens to muscle cells if they are not stressed
undergo atrophy
decrease in size and diameter
define disuse atrophy
can occur from not using
define denervation atrophy
can occur from damage to the nerves that cause contraction
what happens if atrophy persists past 6 months to 2 years
muscle fibers irreversible replace by fibrous connective tissue
what most likely determines the ratio of SO to FG fibers in different muscles
genetics
what impact does the ratio of muscle fibers have on a person’s ability to excel at certain exercise activities
person may be better at some activities than others based on distribution of fibers
who may excel at resistance and short duration high intensity activities? list examples
higher proportions of FG fibers
weight lifting and sprinting
who may excel at long duration low to moderate intensity activities? list examples
higher percentage of SO fibers
long endurance cycling, running, swimming
do the typical number of muscle fibers increase? is there a difference in number of muscle fibers in a large muscular person, vs a thin person
total number of muscle fibers typically does not increase regardless of difference in body size
what can affect the characteristics of muscle fibers
different types of activity
endurance vs strength
list the effects of muscle adaptation to endurance (aerobic) training
increased muscle capillaries, number of mitochondria, myoglobin synthesis
in endurance training, which muscle fibers experience the greatest result
SO fibers
in endurance training, what fibers may gradually alter their characteristics
some FG fibers to FOG fibers
what are the effects of aerobic training on other systems besides muscle
cardiovascular and respiratory adaptations that increase the nutrient transport and waste removal for skeletal muscle cells
VO2 max and lactate threshold may come into play
list the effects of muscle adaptation to strength (anaerobic) training
increase the size and strength, and tension of FG fibers
increase number of myofilaments in muscle cell - results in hypertrophy (bulging muscles)
increase number of mitochondria
increased glycogen stores
increase number of glycolytic enzymes
during anaerobic training which muscle fibers experience the greatest result
FG fibers
during anaerobic training which muscle fibers may gradually alter their characteristics?
FOG fibers to FG fibers
how long does muscle adaptation take
weeks to months
what happens to muscle is exercise ceases
muscle revert to unexercised state
define spasm
sudden involuntary activation of a motor unit within the whole muscle - usually painless
define cramp
involuntary and often painful tetanic muscle contractions
causes of cramps
inadequate blood flow to muscle - dehydration or blood clot
nerve compression
overuse
injury
abnormal blood electrolyte levels - Ca and Mg levels are important
intracellular vs extracellular Na and K also important
what happens to muscles as we age
by age 30 sarcopenia (loss of muscle mass) begins
due to decrease in physical activity
with aging, slow progressive loss of skeletal muscle mass tat is replaced largely by fibrous connective tissue and adipose tissue
compare strength of 25 year old vs 85 year old
at 85, muscle strength is approx 40% of what it was at 25
what can slow the rate of muscle loss
regular exercise
why is exercise important for the elderly
helps reduce bone density loss, prevents loss of ROM in joints, increases cardiovascular health
what are anabolic steroids
mimics the effect of testosterone and DHT in the body
what are the typical beneficial effects of anabolic streoids
increase in muscle size and therefore increase strength, increase lean muscle mass (with proper diet)
cause increased bone growth and remodeling
stimulates red bone marrow
list dangerous effects of long term, high dose steroid use
can cause increase in all cell types - including cancer cells
liver damage
kidney damage
stunted growth for those still growing
mood swings
increased blood pressure and risk of heart disease
increase LDL levels
increased sebaceous gland secretion - pimples
what is stacking and why is it dangerous
combining different steroids and non steroid drugs when undergoing a cycle
negative affects of steroids in males
decreased endogenous testosterone production, conversion of excess testosterone to estradiol - causes female like breast tissue in males
testicular atrophy from decreased sperm production
baldness - increase in androgenic alopecia
negative female side affects
atrophy of breasts and uterus, menstrual irregularities, sterility, increase male pattern growth of body and facial hair, permanent deepening of voice
clitoral enlargment
negative side effects in adolescents
stunted growth due to premature skeletal maturation and accelerated puberty changes
risk of not reaching expected height is precedes growth spurt
who can actually benefit from vitamin supplements
those with nutritional deficiencies or professional athletes
what is recommended daily intake for protein (in grams) per 2.2 lbs of body weight
0.8 g per 2.2 lbs of body weight
who needs more protein intake
growing children, pregnant women, post surgical patient, athletes
when can protein become dangerous
over 200g a day can lead to kidney damage over time
why are pre, during, and post workout supplements dangerous
can increase blood pressure, cause concentration issues, increase rate of dehydration during activity
why do pre, during, and post workout supplements do nothing other than load up with stimulants
advertised ingredients are typically below the amounts needed to make it physiologically relevant
